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ANNALS OF THE

SOUTH AFRICAN MUSEUM

VOLUME 51

ANNALS

OF THE

SOUT AFRICAN MUSEUM

VOLUME 51

PRINTED FOR THE

TRUSTEES OF THE SOUTH AFRICAN MUSEUM:

1968

THE ANATOMY OF THE CAPE ROCK LOBSTER,

ASUS LALANDII (H. Milne Edwards)

NELLIE F. PATERSON

South African Museum, Cape Town

(With 81 figures)

[MS received 11 May 1966]

Introduction .

Material and methods

Classification .

External features . abe:

A. Exoskeleton and ecdysis .

B. Parts of the body

1. Cephalothorax

2. Abdomen. .

3. Cephalic peleriteee

C. Appendages

1. Antennule

2. Antenna .

3. Mandible .

4. First maxilla .

5. Second maxilla

6. First maxilliped

7. Second maxilliped

8. Third maxilliped

g. Pereiopods

10. Pleopods

11. Uropods

D. Autotomy and eeeenertion a

appendages

E. External apertures

F. Food and feeding aitacineatticn

Internal anatomy

A. Body cavity . . :

B. Endophragmal skeleton 3

C. Muscular system .

Ann. S. Afr. Mus. 51, 1968:

1. Trunk musculature

(a) Cephalothoracic muscles

(6) Abdominal muscles

2. Muscles of the eye

3. Muscles of appendages

(2) Antennule

(6) Antenna .

(dZ) First maxilla.

(e) Second maxilla .

First maxilliped. .

(zg) Second maxilliped .

1-232, 81 figs.

CONTENTS

PAGE PAGE

2 (A) Third maxilliped 89

4 (2) Pereiopods gi

6 (7) Pleopods . 98

9 (k) Uropod . 102

g OD. Alimentary tract . 105

13 1. Ossicles and teeth wi provente

16 culus 5 107

18 2. Proventricular valves) Ill

19 3. Muscles of fore-gut III

23 (a) Extrinsic muscles 112

26 (6) Intrinsic muscles 114

27 4. Significance of proventriculus 115

28 5. Digestive gland 118

29g ~=6E._Excretory organs . 119

29 1. Antennal glands . 11g

30 2. Other excretory organs . 128

31 F. Respiratory organs 128

31 G. Blood vascular system 133

32 1. Pericardial cavity and eare 135

34. 2. Arterial system 140

35 3. Venous sinuses 150

4. Branchial circulation. 152

35 H. Nervous system j 156

36 1. Central nervous system : 158

37 (a) Cerebral ganglia 158

41 (b) Cerebral nerves 159

41 (c) Ventral nerve cord 164

4I 2. Stomatogastric nervous system . 173

45 I. Sense organs . 177

45 1. Sensory setae . 178

45 (a) Tactile and Cleon sa Bn iG hs:

54 (6) Antennulary setae 179

65 2. Statocysts . 4 181

68 Saves Baste 184.

70 (a) Median eye 184

72 (6) Compound eyes 186

76 (i) Ommatidia lz

79 (ii) General remarks ou 189

81 (c) Vascular system - 194

83. J. Endocrine organs. 196

86 1. Pericardial organs 197

2 ANNALS OF THE SOUTH AFRICAN MUSEUM

PAGE PAGE

2. Post-commissure organs. . . 198 23) Female Oi ese area

R, Sims eel Bo 4 6 5 5 oD) 3. Speculations concerning fertili-

PXCorcane ye Lu aer ee Mt ja: Rao zation of the eggs. 4 2) s.saKo

area Ua ee email ake Gan Development =.) 3/0). yi.n a ere eT

SuUMMATY: cui e- jacuee il eee . 219

K. Reproductive system . . . . 206 Acknowledgements . . . . . . 220

Tae Malerianccs te ots iets 207% (Reterences Vii 25 eo u tae athe a nO)

INTRODUCTION

The common European and American fresh-water crayfishes, Astacus and

Cambarus, have long been accepted as classical examples of decapod Crustacea,

and the anatomy of the former in particular has been described and illustrated

in most text-books of elementary zoology. In the absence of fresh-water cray-

fishes from South Africa, the marine species, asus lalandi (H. Milne Edwards),

is an excellent substitute for practical instruction, not only on account of its

large size, but also because supplies are plentiful.

Popularly called the spiny crayfish, spiny lobster, Cape crawfish, kreef, or

Cape rock lobster, this species and closely related forms abound along the rocky

shores of countries in the southern hemisphere and, as a result of important

fisheries established for their collection, canning, and marketing, a number of

interesting articles dealing with their applied biology and economic signifi-

cance have appeared from time to time. Reports by the pioneers of systematic

investigations based in Cape Town have been cited by Barnard (1950), and

flourishing industries have been surveyed more recently by Matthews (1962)

and Soares-Rebelo (1964), while further intensive research is currently in pro-

gress under the direction of Dr. A. E. F. Heydorn, of the Division of Sea

Fisheries, Cape Town.* In addition, the observations of Hickman (1945),

Chace & Dumont (1949), Sheard (1949), Bradstock (1950), Angot (1951), and

Grua (1960) may be mentioned as examples of the aims and achievements of

various research stations in other countries. Most of the published information

summarizes the results of comprehensive investigations concerning essential

commercial and ecological problems, including the distribution of and fluctua-

tion in populations of the species in divers breeding grounds and the legal

measures adopted in different countries for the protection of rock lobster

‘sanctuaries’. Regarding their general distribution, Hickman (1945) has stated

that they occur off the coasts of Tasmania, New Zealand, South Africa, Tristan

da Cunha, and Juan Fernandez, Chile. To these areas Gruvel (1911), Chace &

Dumont (1949), Barnard (1950), Angot (1951), and Grua (1960) have added

the islands of St. Paul and New Amsterdam in the southern Indian Ocean,

while Sheard (1949: 8) has specified ‘a circumpolar distribution range from

32° to 45°S latitude’, and has also given particulars of fishing grounds in

Australian waters, including those off Tasmania.

For many years it has been assumed that the animals which have been

commercially exploited in the aforementioned geographical areas were widely

* Appointed Deputy Director, Oceanographic Research Institute, Durban, as from July 1967.

THE ANATOMY OF THE CAPE ROCK LOBSTER 3

dispersed Jasus lalandii, but Holthuis (1963) has determined that six separate

species are represented in these localities, and that they are distinguishable

mainly by variations in the spines on the carapace and the squamous patterns

on the abdominal terga. The species recognized by Holthuis and their respective

regional distribution are: Jasus lalandu (H. Milne Edwards), South Africa;

fj. paulensis (Heller), St. Paul and New Amsterdam Islands; 7. edwardsii (Hut-

ton), New Zealand; 7. frontalis (H. Milne Edwards), Juan Fernandez; and two

new species, 7. novaehollandiae from south-east Australia, and 7. tristani from

Tristan da Cunha. One of the distinctive features of 7. lalandi indicated by

Holthuis is that it has a number of squamae immediately in front of the trans-

verse groove on the first abdominal tergum (figs 1, 9, 43), whereas in the other

five species the whole of the anterior half of the first abdominal tergum is non-

squamous and smooth.

According to Gilchrist (1913a, 1918) and Von Bonde & Marchand (1935),

f- lalandii shows a preference for the cooler waters of the Atlantic coast, along

which productive fishing grounds range from Cape Point in the south to Cape

Cross 60 miles north of Walvis Bay, those north of the Orange River being now

controlled by the Administration of South West Africa. In these localities the

rock lobsters are stated to have a vertical distribution from low-water mark

down to 20 or 25 fathoms. The choice of cooler waters has also been confirmed

by Sheard (1949), but apparently the Australian specimens are fished at

greater depths, special pots having been devised for their capture at approxi-

mately 40 to 45 fathoms. From Angot’s (1951) and Grua’s (1960, 1964) analyses

of fishing operations off the islands of St. Paul and New Amsterdam, it also

emerges that growth takes place when the water temperature is low and that

the reproductive period does not coincide with the austral summer.

While most of the research projects have been designed with the object of

compiling data and statistics immediately concerned with the promotion of the

rock lobster industry, the more academic studies of Fasus lalandi have not

entirely been neglected. Preliminary observations of early embryonic develop-

ment and descriptions of the main larval stages by Gilchrist (19130, 1916,

1918, 1920) have been supplemented by Von Bonde’s (1936) fuller account of

both the embryonic and the post-embryonic development. Jointly in 1922 these

two investigators and also Von Bonde & Marchand (1935) have been respon-

sible for what little published information there is concerning the general

anatomy of both sexes of this species. Thus, for the past forty years the article

by Gilchrist & Von Bonde (1922) has been relied upon as a guide to practical

studies in a number of South African zoology departments. While this has

proved adequate for elementary courses, most of the systems of organs have

been treated rather superficially and, in view of the universal upsurge of

interest in the physiology of Crustacea, the need for a more profound under-

standing of its anatomy has arisen. In connexion with the taxonomy of the

order, the external features of the majority of Decapoda have been examined

carefully but, although a number, including certain palinurids, have been

4 ANNALS OF THE SOUTH AFRICAN MUSEUM

widely used as experimental animals, there are few comprehensive accounts of

the internal organs. The foundation laid by Huxley (1881) in his excellent

monograph on Astacus astacus (L.) has been amplified by the painstaking studies

of Keim (1915), Schmidt (1915), Baumann (i921), Panning (1924), and Stoll

(1925) on different systems of the same species. Apart from these publications

and Herrick’s (1911) account of the American lobster, information relating to

the internal organization of Macrura Reptantia is somewhat scattered and

often fragmentary, but much of it has been collated by Balss and his asso-

ciates in the classical treatise on Decapoda in Bronns Klassen und Ordnungen des

Tierreichs (1940-1961), and in two volumes entitled, The physiology of Crustacea,

edited by T. H. Waterman (1960, 1961). Such details as seem essential to a

comparison of the anatomy of the Cape rock lobster with that of other decapods

have been drawn from these and other sources, and are discussed wherever

pertinent.

The following account of the various systems of organs in 7. lalandi is intended

to convey elementary facts for the information of students attending a course

in general zoology, but it also includes some finer details that may serve as a

basis for any future physiological investigations. It has been concluded that its

overall organization resembles that of the better-known fresh-water crayfish,

Astacus astacus (L.), and that some of the structural differences between the two

species may be ascribed to idiosyncrasies of habits and habitat.

MATERIAL AND METHODS

The specimens on which most of the present observations are based were

taken from the stock maintained for practical classes in the Zoology Depart-

ment, University of Cape Town: they comprised small to medium-sized mature

males and females, averaging 21 to 22 cm in total length and having a cephalo-

thoracic length of approximately 7-5 cm. Such specimens were usually obtained

alive from a local fisherman operating off Robben Island in Table Bay; they

were then killed and preserved in 5°% formalin. Occasionally, to check certain

details, freshly killed specimens were used. Observations were also made of

living animals at the Sea Point Aquarium, and on a few kept alive in the cons-

tant temperature rooms of the Zoology Department, in which the water

temperature was about 13°C. A number of juvenile males and females,

kindly collected at Liideritz Bay, South West Africa, by Mr. M. J. and Dr.

Mary-Louise Penrith of the South African Museum, were also a source of

useful and interesting information.

Most of the dissections were prepared by making lateral incisions along

the cephalothorax and abdomen and, after removal of the dorsal part of the

exoskeleton, the various systems of organs were traced in succession from the

most superficial dorsal to the deeper ventral structures. A complete impression

of each system was thus gradually built up as the dissections proceeded. A good

overall picture of a median or parasagittal view of the general anatomy (fig. 31)

THE ANATOMY OF THE CAPE ROCK LOBSTER 5

may also be obtained by making a mid-dorsal incision followed by careful

excision of the organs, especially the muscles, of one side, and final clearance

of the exoskeleton of that side. In this way, all the organs of the other side and

also median structures are left intact, resulting in a proper perspective of the

anatomy with the essential organs zn situ.

To check some of the details observed in gross dissections of adult specimens,

transverse serial sections, cut at 10 » thick, were made of the young planktonic

puerulus stage (fig. 81) which had been fixed in Bouin’s aqueous fluid when

collected by Dr. Heydorn. Some difficulty was experienced in softening the

rather thick, transparent exoskeleton. Treatment of specimens for two or three

days with 3% nitric acid in 70% alcohol and then placing them for three or

four days in a 10% solution of soft soap in 70% alcohol gave poor results.

When diaphanol, followed by tetra-hydro-naphthalene (tetralin) as a clearing

agent, proved almost as unsatisfactory, mushroom extract, as recommended

by Carlisle (1960), was tried. It was found advisable to subject the specimens

to the action of a 1 : 10 dilution of the extract at 37° C. for two to four days,

transferring them to fresh mushroom extract daily. After washing the specimens

thoroughly in distilled water for 15 minutes or longer, they were then

dehydrated in three changes of triethyl phosphate, cleared in methyl benzoate

celloidin, and embedded in paraffin wax in a vacuum oven. The various

stains employed to differentiate the tissues were: Mallory’s triple stain, Hansen’s

haematoxylin or Heidenhain’s iron haematoxylin with eosin Y or eosin B as

counterstains, and Weigert’s iron haematoxylin followed by Biebrich scarlet

and methyl blue, but pleasing results were also obtained by using Mayer’s

haemalum and counterstaining in eosin B.

Subsequent to fixation in Zenker’s fluid, serial sections were also made of

the eyes, the excised sinus gland, the gills, and the antennal gland of the adult.

The sections of the eyes and sinus gland were stained in Heidenhain’s iron

haematoxylin and phloxine, while the histology of the gills and the antennal

gland was clearly defined by employing Heidenhain’s iron haematoxylin and

eosin B. Following the procedure elaborated by Steedman (1960), some

specimens were sectioned and stained after infiltration with Tropical Ester

Wax and, although the sections were inclined to overstretch a little even at

room temperature, on the whole the preparations were good and stained well.

It should also be indicated here that additional notes on simple techniques

used in preparations of the endophragmal skeleton (p. 42), the blood vascular

system (p. 133), and parts of the nervous system (p. 167) have been included,

and that, while the illustrations are drawn to scale, certain liberties have been

taken in displacing some of the organs to clarify the position of the parts relative

to one another. This is particularly evident in the figures of the musculature of

the appendages, in which the individual muscles are diagrammatically repre-

sented and some of the superficial elements have been slightly reflected to

expose the more deeply seated ones.

6 ANNALS OF THE SOUTH AFRICAN MUSEUM

CLASSIFICATION

The classification of decapod Crustacea proposed by Borradaile (1907) has

been broadly adhered to by other taxonomists, including Calman (1909),

Barnard (1950), and Balss (1957), and, using it as a basis, the systematic

position of Zasus lalandi relative to other members of the order may be tabulated

as follows:

Order: DECAPODA

Suborders: NATANTIA REPTANTIA

Tribes: PENAEIDEA CARIDEA STENOPIDEA

PALINURA ASTACURA ANOMURA RBRACHYURA

Superfamilies: ERYONIDEA SCYLLARIDEA

Families: SCYLLARIDAE PALINURIDAE

Genus: Jasus Parker

Species: Jasus lalandii (H. Milne Edwards)

The suborder Natantia and the tribes Palinura and Astacura are fre-

quently distinguished from the remaining Reptantia as the MACRURA or forms

with a large, straight abdomen and a broad, strong tail-fan. Of the MAcRURA

REPTANTIA, Von Bonde & Marchand (1935) have listed 14 South African

species, and Barnard (1950) has accounted for at least another 17 species,

including some from Mauritius. In both publications two species of Fasus are

recorded: 7. lalandi (M. Edw.) and 7. parkert Stebb. The latter occurs off the

coast of East London and, among other characteristics, is distinguished from

J. lalandu by the absence of squamae, by the submedian and lateral rows of

strong spines on the carapace, the indistinct cervical groove, and the mid-dorsal

keel on the first five abdominal segments. The distinctive features of 7. parkeri

Stebb. have been considered by George & Grindley (1964) to be sufficient

justification for its removal to a new genus, designated Projasus.

As some of the characters mentioned in Borradaile’s (1907) keys are rele-

vant to a description of the external features of 7. /alandii, it seems pertinent to

review them briefly, although they have been abstracted elsewhere by Pearson

(1908), Barnard (1950) and other authorities.

The REPTANTIA are differentiated from the Natantia by the following

characters: the body is usually depressed; in the abdomen the first segment is

generally the smallest; the rostrum is small or absent; the basal segment of the

antennulary peduncle is not enlarged into a stylocerite; the exopodite of the

antenna is reduced or wanting; the pereiopods lack exopodites and each appears

to be composed of six segments owing to the coalescence of the basipodite and

THE ANATOMY OF THE CAPE ROCK LOBSTER 7

the ischiopodite; the pleopods are not natatory and may be reduced or absent.

Some of the distinctive features of the PALINURA are: the macrurous abdo-

men and the broad tail-fan; the small or absent rostrum; the lateral fusion of

the epistoma with the carapace; the numerous gills; and the presence, at least

in the female, of an appendix interna on some of the pleopods.

The scYLLARIDEA are distinguished by the carapace being secured between

an inner knob on the last thoracic segment and an outer flange on the first

abdominal segment; the antenna is uniramous and the proximal segment of

its peduncle is fused with the epistoma; with the exception of the last pair in the

female, none of the pereiopods is normally chelate; in both sexes the first

abdominal segment has no pleopods; the telson is more or less truncate.

In the family PALINURIDAE the cephalothorax is subcylindrical; the eyes

are not lodged in separate sockets; and each antenna has a three-segmented

peduncle which supports a long whip-like flagellum.

Barnard (1950) has shown that species of at least five genera belonging to

this family, namely, Fasus Parker, Palinurus Fabr., Palinustus M. Edw., Linuparus

Gray, and Panulirus (Gray) White, are represented in the South African fauna,

while the genus Palinurellus Von Martens has been collected off the coast of

Mauritius and, according to Balss (1941), is exceptional among Scyllaridea,

in having vestiges of pleopods on the first abdominal segment of both sexes.

Barnard (1950) has also indicated that in 1946 Holthuis created the genus

Justitia for the species Palinurus longimanus M. Edw., the relatively long and

sturdy first pereiopods of which are unusual in being subchelate.

Based on certain marked structural differences, Parker (1883, 1884)

rearranged the species which had originally been included in the genus

Palinurus Fabr. into three subgenera, namely, asus, Palinurus, and Panulirus,

and these were later arbitrarily accepted as valid genera. It was not until 1961,

however, that an application by Holthuis (1960) was approved by the Inter-

national Commission on Zoological Nomenclature (Opinion 612, Bull. zool.

Nom., 1961, 18: 312-315), and the generic name Jasus Parker, 1883, was

placed on the Official List of Generic Names in Zoology. The generic features

of Fasus Parker recognized by various taxonomists are: its small pointed rostrum

which is clasped by a pair of pedate processes; the presence of procephalic pro-

cesses; the short antennulary flagella; the approximation of the bases of the

antennae; and the absence of stridulating organs. (With the exception of Fasus

and Palinurellus, both sexes of Palinuridae produce harsh noises when the

antennae are raised and, because of this, Parker (1884) separated the family

into two natural groups, the Stlentes, or non-stridulating forms, and the Stri-

dentes, or stridulating species. In the Stridentes the dorso-medial articulation

of the basal segment of the antennal peduncle with the head is modified into

a projecting, ventrally ridged process which slides over the lateral, keeled,

frontal region of the exoskeleton and makes an audible creaking sound.)

Although probably first popularly called ‘langouste de Lalande’ by Lam-

arck, the original systematic description of the spiny rock lobster as Palinurus

8 ANNALS OF THE SOUTH AFRICAN MUSEUM

lalandit is generally ascribed to H. Milne Edwards (1837). Its subsequent

removal to the genus Jasus by Parker in 1883 has, of course, not affected the

account of the specific characters which were expressed as follows by H. Milne

Edwards (1837: 293-294):

‘LANGOUSTE DE LALANDE.—P. lalandii.

Cornes latérales du front lisses en dessus et en dessous, et beaucoup moins avancées que la petite

corne médiane, au-dessous de la base de laquelle on voit deux petites épines. Carapace armée

d’épines et couverte de gros tubercules ovalaires déprimés et séparés a leur base par des poils

courts et serrés. Abdomen entiérement couvert de tubercules aplatis, squammiformes, et garnis sur leur

bord postérieur d’une rangée de poils trés-courts; une seule dent sur le bord postérieur des

cornes latérales de l’abdomen. Antennes internes courtes. Pates antérieures trés-grosses, courtes

et armées en-dessous de deux dents coniques trés-fortes, dont une placée sur le deuxiéme article,

et autre sur le bord inférieur du bras ou troisiéme article; pates suivantes, granuleuses en-dessus.

Couleur brun-rouge, irréguliérement tacheté de jaune. Longueur (du corps), environ 15 pouces.

Habite les cétes du cap de Bonne-Espérance. (C. M.)’

Some confusion regarding the orthography of the specific name has been

evident, for it has appeared in print either as 7. lalandii or as 7. lalandei, but in

1960 Holthuis proposed that the latter spelling receive official recognition. This

emendation was later abandoned, however (Opinion 612, Bull. zool. Nom.

1961, 18: 312-315), and the specific name Jalandi was ratified.

The obvious transverse furrow on each abdominal tergum, produced by

the prominence of the penultimate row of squamae, is another noteworthy

characteristic referred to by Stebbing (1902) and Barnard (1950). To the

specific features supplied by Milne Edwards, Barnard has also added the

presence of a distinct cervical groove, while details concerning the mandibular

palps and the exopodites of the three pairs of maxillipeds have been specified

by Gruvel (1911).

As indicated by Milne Edwards (1837), the general coloration of the body

is brownish red, but it is also frequently tinged with an iridescent purplish

hue which is particularly noticeable on the tail-fan. One of the sexual differences

noted by Gilchrist (1913@), Von Bonde & Marchand (1935), and Von Bonde

(1936) is that the females are usually rather darker than the males, while

among animals collected in the vicinity of St. Paul and New Amsterdam

Islands, Angot (1951) has observed an appreciable colour range, varying from

light red in shallow coastal waters to dark red in specimens captured at greater

depths. Size variations are also apparent, a total length of up to 460 mm (18

inches) for South African specimens and up to 510 mm (20 inches) for Austra-

lian forms having been recorded by Barnard (1950). Moreover, reports by

Gilchrist (1913a), Von Bonde & Marchand (1935), Von Bonde (1936), Hick-

man (1945), Bradstock (1950), and Grua (1960) show that certain size

differences may be correlated with sexual dimorphism, mature males being

invariably larger than the females; but a possible explanation of this, offered

by Von Bonde (1936), is that the females attain sexual maturity earlier than

the males, the estimated ages being approximately 2} years in females as

against 5 to 6 years in males.

THE ANATOMY OF THE CAPE ROCK LOBSTER 9

EXTERNAL FEATURES

A. EXOSKELETON AND Ecpysis

The whole surface of the body is covered by a thick, epidermal exoskeleton,

the constituents and structure of which have been minutely examined in

Brachyura by Drach (1939), and discussed relative to Crustacea in general by

Dennell (1960). Briefly, it is composed of a chitin-protein complex impregnated

with calcium carbonate, and is structurally differentiated into a thin, non-

chitinous epicuticle and a thicker, chitinous endocuticle, with the latter sub-

divided into three strata, viz. a pigmented layer, a thick calcified layer, and an

uncalcified layer adjacent to the epidermis. Calcium salts are reported to be

deposited heavily in the epicuticle and the pigmented layer, as well as in the

calcified layer proper, but the latter is distinguished from the other three zones

of the exoskeleton by its poor protein content. To allow of movement, the

exoskeleton remains thin and flexible between the segments of the body and

also between the parts of the appendages, where the softer areas consist mainly

of epicuticle and uncalcified endocuticle and are termed arthrodial membranes

(figs 1, 5, 8, 16, 25, 31).

In the taxonomic notes it has been indicated that the dorsal surface of the

exoskeleton of 7. lalandii is furnished with pointed spines and a mosaic of

closely-set, flattened scales or squamae (fig. 1) which are bordered by reddish,

plumose setae. Similar setae also fringe the free edges of the carapace and the

posterior margins of the abdominal segments and, as a rule, the setae at the

bases of the cephalothoracic squamae project forward, while those on the

abdomen are backwardly directed. The spines are arranged in regular longi-

tudinal rows on the dorsal part of the cephalothorax; they generally point

forward and become progressively smaller behind the conspicuous, acutely-

pointed postocular processes. The more lateral regions of the cephalothorax

lack spines, but are covered with small contiguous squamae and are smoother

in appearance and lighter in colour than the dorsal surface of the cephalothorax.

As the body is encased in a calcified exoskeleton, growth is discontinuous

and can only be effected during relatively short periods when the animal sheds

its exoskeleton and endoskeleton and also the cuticular lining of the gut. The

process of exuviation or ecdysis is characteristic of all Arthropoda, and in

Crustacea it has been most fully investigated in brachyuran Decapoda. It has

been shown by Drach (1939) and Passano (1960) that, although it only recurs

from time to time during the life-span of the animal, each ecdysis is really the

culmination of a number of phases which affect the animal’s behaviour and

metabolism throughout the comparatively long intermoult periods between

successive ecdyses. The secretion of the epicuticle and the pigmented layer of

the endocuticle of the new exoskeleton precedes ecdysis, while the expansion of

the thoracic region of the body and the resultant rupture of the old exoskeleton

along a resorptive or ecdysial suture are implemented by a marked absorption

of water. From studies of ecdysis in Panulirus argus (Latreille), Travis (1954) has

ime) ANNALS OF THE SOUTH AFRICAN MUSEUM

concluded that uptake of water probably takes place through the gills and the

intersegmental membranes, and that the accumulation of an unknown gas

between the old and the new linings of the stomach is also of material assistance

in the enlargement of the body. Carlisle & Knowles (1959) have accepted the

theory of integumentary and branchial uptake of water, but Passano (1960)

has favoured the opposite view, expounded by Drach (1939), that in aquatic

decapods pre-ecdysial water is absorbed through the lining of the gut.

During the present observations of 7. lalandi the resorptive suture became

evident along the branchiostegite some time before ecdysis, and a relatively

broad vertical resorptive band was also noticed at the junction of the pre-

branchial and the branchial chambers. Ecdysis of captive 7. lalandi was

observed on several occasions between sunset and midnight, and an examination

of the cast shells indicates that the carapace becomes detached from the epimera

and the inner lining of the branchiostegite along the cervical and the branchio-

cardiac grooves. Furthermore, it is apparent that ecdysis also involves the

endoskeleton, parts of which, especially the mesophragms, are markedly

resorbed, so that sufficiently wide gaps are formed for the extrication of the new

endoskeleton. In most of the exuviae examined the branchiostegites were intact,

and it would appear that, as in Panulirus argus (Travis, 1954.), calcium resorption

along the ecdysial suture helps to loosen the branchiostegite from the articular

condyle on the last epimeron, and that during ecdysis slight flexure of the

branchiostegite takes place along its weakened suture. Although the branchi-

ostegites do not necessarily fracture, there is an important transverse hinge

between the epistoma and the supralabral ridge. On this the old carapace is

tilted upward and forward at an angle of about go° after rupture of the thoraco-

abdominal intertergal arthrodial membrane by pressure from the underlying

soft-bodied animal. This results in a wide dorsal opening between the thorax

and the abdomen of the old exoskeleton through which the animal gradually

emerges, withdrawing its appendages, gills and abdomen and eventually

jerking itself free from the old exoskeleton and endoskeleton. The whole process

takes about five minutes, and in a normal ecdysis the old skeletal framework

of the animal is shed completely and within the exuviae the old cuticular

linings of the fore-gut and the hind-gut remain attached anteriorly and

posteriorly.

It is also evident from the deliberations of Drach (1939) and Passano

(1960) that the intermoult cycle is characterized by a number of events which

contribute to the general reorganization of the tissues and the preparatory

stages of the next ecdysis. Shortly after exuviation, there is a gradual hardening

of the new exoskeleton combined with the formation of the calcified layer of

the endocuticle; and, subsequent to the completion of tissue growth and the

secretion of the uncalcified layer of the endocuticle, organic reserves (lipids,

glycogen, and proteins) and mineral reserves (Ca and Mg phosphates) are

stored in the digestive gland or hepatopancreas against a period of fasting and

the elaboration of a new exoskeleton prior to the next ecdysis.

THE ANATOMY OF THE CAPE ROCK LOBSTER 1A

According to Passano (1960), there is experimental proof that these

activities are influenced by such environmental factors as light and temperature,

and that they are regulated by the interaction of certain hormones and neuro-

secretions. The incidents leading up to ecdysis are initiated by the release of

a moulting hormone into the blood from a small, paired Y-organ, which in

crabs is located towards the anterior limit of the branchial chamber near the

mandibular external (posterior) adductor muscle. It is believed, however,

that one of the neurosecretions produced by the X-organ and periodically

released from the sinus gland in each eyestalk has a moult-inhibiting effect and

suppresses synthesis by the Y-organ of the moult-promoting hormone.

Observations by Von Bonde & Marchand (1935) have revealed that in

fj. lalandii ecdysis takes place twice a year until a cephalothoracic length of

34 to 4 inches is reached, after which there is probably a regular annual moult;

sexual maturity may, however, be attained when the cephalothoracic length

is 2 to 3 inches or even less. These investigators also noted that the moulting

season varied in different localities and that, whereas in males it usually took

place from September to February, the time of annual ecdysis of females was

not determined, but was thought by them and by Gilchrist (1913a@) to occur

during the winter months. Some corroboration of the latter supposition is

implied in Matthews’s (1962) statement that ecdysis in female South West

African rock lobsters coincides with the peak spawning period from August to

November, but from operations off the South African west coast, in which

soft-shelled specimens were collected at quarterly intervals from June 1962 to

March 1963, Heydorn (1965) has concluded that in the two areas investigated

neither sex appeared to have a definite moulting season; nevertheless peak

moulting periods for males occurred during September at Port Nolloth and

during December at St. Helena Bay, and a slight increase in the percentage of

moulting females was observed during March at Port Nolloth.

The moulting cycle and growth rate of captive Australian spiny lobsters

have recently been studied by Fielder (19642), who found that experimental

animals with a cephalothoracic length of from 5 to 7-9 cm moulted three times

a year, while those in the 8 to 8-9 cm category underwent two annual moults,

and the frequency of moulting seemed to be influenced by increases in the

temperature of the water. Hickman (1945) has also mentioned that immature

Tasmanian asus moult several times a year, and his findings confirm reports

by Gilchrist (1918) and Von Bonde & Marchand (1935) that ecdysis of the

female is a precursor of mating and egg-laying, the latter usually taking place

a few days after the female has moulted. Hickman’s further observation that

oviposition occurs mainly from April to June is more or less in accordance

with Grua’s (1964) account of events in 7. paulensis, but is hardly compatible

with records for South African rock lobsters which, although variable and

somewhat confusing, nevertheless indicate that egg-production tends to be

later in F. lalandiit than in F. novaehollandiae and F. paulensis. Thus, Gilchrist

(1918) noted that in 1916 spawning occurred from October to about the

16594 ANNALS OF THE SOUTH AFRICAN MUSEUM

middle of December, while in the following year it started in June. Females

‘in berry’ were found by Von Bonde & Marchand (1935) from July to February,

but the times varied at different stations, and it was estimated that the average

ovigerous period lasted approximately two to three months. More recently,

Matthews (1962) has reported that South West African female rock lobsters

reach maximum fertility from August to November and are practically barren

during the period from February to April or May. Analyses of egg-carrying

females collected by Heydorn (1965) in two areas off the South African west

coast in June, September, and December 1962, indicated that the highest

percentages were in September, but the general impression is that June to

August probably represents the period of maximum productivity, especially

in larger females, and this more or less corresponds with Fielder’s (19645)

remarks on fishing surveys in South Australia. The reason for these variations

is not apparent, but may be associated with environmental factors, particularly

with differences in the temperature of the water. In this connexion, Sheard

(1949) has mentioned that Australian forms of Zasus prefer waters of less than

18° C., especially during ecdysis, mating, and oviposition, while Grua (1960,

1964) has established that spawning takes place off the islands of St. Paul and

New Amsterdam in autumn when the water temperature is approximately

14° or 16°C. In his treatise on the crayfish industry in Western Australia,

Sheard (1962) has given some significant information regarding the correlation

between the monthly water temperatures and ecdysis in Panulirus cygnus George

[Panulirus longipes (H. Milne Edwards) ]. In this species he has ascertained that

the following four moulting cycles prevail: when the water temperatures are

falling in June, maturing females moult prior to the mating season in July and

early August; coinciding with periods of rising temperatures, moulting takes

place in January and early February in females after the larvae have emerged

from the eggs; males and some females were observed to moult in January to

March; and the immature crayfish moulted in November. From this it 1s

evident that the moulting period for males of P. cygnus is from January to

March and that, as in 7. lalandii, the main moult of the females is the one pre-

ceding mating. It is also notable that ovigerous females of P. cygnus were col-

lected from late August to February, a period which roughly corresponds with

that in records for 7. /alandit published by Von Bonde & Marchand (1935),

Matthews (1962), and Heydorn (1965), and it seems likely that in most pali-

nurids spawning takes place once a year. There seems to be some uncertainty

regarding the number of annual ecdyses that occur in mature females of Fasus,

and it could be assumed that, because the female strips the empty egg-capsules

from the pleopods, another moult is not required after the larvae have hatched.

Grua (1964), however, has remarked that, in addition to the pre-mating

ecdysis in 7. paulensis, a summer ecdysis may be necessary for the renewal of

the ovigerous setae which are damaged when the female cleans the pleopods.

Some confirmation of Grua’s statement was obtained while making recent

observations of captive 7. lalandii at the Sea Point Aquarium. During the

THE ANATOMY OF THE CAPE ROCK LOBSTER 13

summer months, when some mature males and both sexes of juvenile rock

lobsters were moulting, a number of mature females, including several that

had been ‘in berry’ and had cleared the ovigerous setae, underwent a second

annual moult. It is rather significant that after this ecdysis the pleopods were

devoid of ovigerous setae, and it has been concluded that they are

only developed at the moult which precedes mating. It is therefore probable

that, as in species of Panulirus (Crawford & De Smidt, 1922; Lindberg, 1955;

Sheard, 1962), a post-ovigerous ecdysis also occurs in Jasus.

B. Parts OF THE Bopy

Fundamentally the body may be divided into three regions or tagmata,

the head or cephalon, the thorax, and the abdomen but, in common with other

Decapoda, secondary fusion of the first two parts has resulted in the formation

of a cephalothorax.

In the Malacostraca the number of body segments is limited to twenty-one,

some of which are indistinctly marked, but most of which are indicated exter-

nally by the presence of paired, jointed appendages. The estimation of the total

number of segments, however, is contingent upon the interpretation of the

components of the head region, and recently the problem of head segmentation

in the Arthropoda has been reviewed in articles by Butt (1960) and Manton

(1960). The former author has attempted to identify four head segments, while

Manton has substantiated her previous convictions (1928, 1934, 1949) that

there are six head somites.

The main differences of opinion relate to the preantennulary and the

antennulary segments: on the one hand, Butt doubts their existence while, on

the other hand, from studies of the ontogeny of various arthropods, Manton

has provided evidence which justifies their recognition. Basing his conclusions

mainly on insect embryology, Butt has introduced another version of the

concept of arthropod head segmentation in which the intercalary segment, with

the labral lobes representing its appendages, is regarded as the first segment:

accordingly, in his opinion the arthropod head is composed of an unsegmented

acron plus the intercalary (second antennal of Crustacea), the mandibular, the

first maxillary, and the second maxillary segments. Arguments in favour of

regarding the second antennal segment as the first true body segment have

previously been presented by Snodgrass (1938, 1951, 1952), who compared the

arthropod acron to the annelid prostomium. He stated that in the arthropod

embryo this region bears the eyes, the labrum, the preantennae occasionally,

and the first antennae (antennules of Crustacea), and concluded that in the

majority of Eumalacostraca the head is composed of the unsegmented acron and

one segment, that of the tritocerebral or second antennal somite. Snodgrass

therefore discounted the preantennulary and the antennulary segments and

assigned the mandibles and the first and second maxillae to the thorax, but

Manton (1949, 1965) has found that many of his views concerning some of the

cephalic appendages and arthropod head segmentation are fallacious.

14 ANNALS OF THE SOUTH AFRICAN MUSEUM

Paired mesodermal somites, neuromeres, and limb-rudiments, which are

accepted as reliable criteria of segmentation, have been reported in the anterior

region of the head of various arthropods by a number of embryologists, whose

conclusions are reviewed by Manton (1960). Moreover, in studies of the onto-

geny of certain Crustacea, Manton (1928, 1934) has clearly demonstrated that,

as in Myriapoda and Insecta, three preoral segments, the preantennulary, the

antennulary, and the antennal, are present. The labral rudiment originates in

anterior unsegmented ectoderm and forms a median transverse bridge between

the anterior ends of the U-shaped germinal band level with the preantennulary

somites. As development proceeds and the preoral somites become more

marked on the germinal band, the labral rudiment derives most of its mesoderm

from the preantennulary somites and gradually shifts back until it lies behind

the antennal somites at the anterior margin of the mouth. As Manton (1960)

has pointed out, there is proof that in insect embryos the paired labral lobes

represent the transitory appendages of the preantennal somite and not those

of the premandibular or intercalary segment. In Crustacea, although pre-

antennulary limb-rudiments are not developed, other valid criteria of meta-

merism have been demonstrated in the preantennulary region. The pre-

antennulary somites were first discovered by Manton (1928) in Hemimysis, in

which definite and partly persistent coelomic cavities are formed. Nair (1949)

has also described preantennulary coelomic cavities in Caridina, and pre-

antennulary somites also occur in Webalia (Manton, 1934) and in several other

Crustacea which have been cited by Nair (1949) and Manton (1960). The

denial of segmental status to the antennules is another obvious misconception,

for they develop as the appendages of distinct somites which havea pair of ganglia.

On this premise it is considered that the first head segment is purely

embryonic, but that the other five head segments are distinguished externally

in the adults by a series of paired appendages, the antennules, the antennae,

the mandibles, the first maxillae, and the second maxillae. Eight segments,

bearing in succession three pairs of maxillipeds and five pairs of pereiopods, are

present in the thorax. The abdomen consists of six apparent segments, each of

which, except the first in Jasus, has a pair of appendages. The appendages of the

sixth abdominal segment, the wropods, are large and when spread out they form

the so-called tazl-fan. The abdomen ends in a median, somewhat rectangular

structure, the telson, which lies above and between the uropods and has mem-

branous connexions and lateral articulations with the sixth abdominal segment,

beneath which it can be flexed simultaneously with the uropods. It should be

noted that studies of malacostracan embryos (Manton, 1928, 1934) have proved

that the telson arises from the unsegmented posterior end of the embryo. It

therefore has no segmental value and merely represents a dorsal extension of

the last abdominal segment. Moreover, the latter segment has been shown by

Manton to be formed by the fusion of two embryonic segments, and a similar

conclusion is implied in Stoll’s (1925) suggestion that the large ganglion in the

last abdominal segment of Astacus may represent the ganglia of two fused segments.

THE ANATOMY OF THE CAPE ROCK LOBSTER

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16 ANNALS OF THE SOUTH AFRICAN MUSEUM

I. CEPHALOTHORAX

Dorsally and laterally the cephalothorax is covered by a thick exoskeleton

on which a number of areas are defined by certain grooves. Following Huxley’s

(1881) account of the anatomy of Astacus, it has generally been supposed that

the possible boundary between the head and thoracic regions is marked by a

fairly deep cervical groove (fig. 1) which runs transversely across the middle of

the exoskeleton and is continued forward and downward on each side as an

oblique, slightly curved depression. The cephalic area of the exoskeleton is

somewhat indistinctly demarcated by a faint dorso-lateral furrow into a

median gastric and two lateral, yellowish hepatic regions (fig. 1), respectively so

called because the former lies above the fore-gut while the latter cover the

anterior mandibular apodemes and their contained lateral extensions of the

digestive gland. Anteriorly between the paired stalked eyes, the gastric region

is produced into a short median spine, the rostrum (figs 1, 3, 10, 60, 77), which

is characteristically embraced by a pair of structures (figs 3, 10, 60, 77), termed

the clasping or fedate processes by Parker (1883, 1884, 1889).

Behind the cervical groove the thoracic region is enveloped by a dorsal

shield, called the carapace, a term which 1s also frequently used by carcinologists

to describe the whole of the dorsal cephalothoracic exoskeleton. Two shallow,

longitudinal branchio-cardiac grooves divide the carapace into a mid-dorsal

cardiac region overlying the pericardial cavity and a pair of lateral folds, the gill-

covers or branchiostegites (figs 1, 2, 10, 53, 77). Each branchiostegite forms the

outer wall of the branchial chamber and may represent the conjoined thoracic

pleura. In 7. lalandii the carapace is typically broader in the mature male than

in the female, a feature which has been cited by Gilchrist (1913a), Von Bonde

& Marchand (1935), and Von Bonde (1936) as one of the reliable means of

distinguishing the sexes.

The development of the carapace results not only in the rigidity of the

cephalothorax, but also obscures all traces of metamerism on the dorsal surface.

Ventrally, however, there is a series of firmly-united, calcified plates, the

sterna (figs 2, 7, 80), separating the bases of the eight pairs of thoracic appen-

dages. Between the first three pairs of appendages the sternum is a narrow,

median ridge, but behind this it gradually widens into a large, triangular

shield which reaches its maximum breadth between the penultimate pair of

limbs and narrows appreciably in the last thoracic segment. The last five

thoracic segments are clearly defined by transverse, setose grooves on the

sternum, the lateral margins of which are notched for the ventral articulations

of the appendages.

The thoracic segmentation is also evident laterally where vertical plates,

considered by Snodgrass (1952) to be thoracic pleura but herein designated

epimera (figs 2, 3, 7), form the inner wall of the branchial chamber. They

extend upward from the arthrodial membranes of the appendages and are

confluent dorsally with the inner lining of the branchiostegite. Resulting from

the invagination of the endopleurites of the endophragmal skeleton, the proxi-

THE ANATOMY OF THE CAPE ROCK LOBSTER 17

antennule antenna

antennulary sternum

excretor ore

wp, epistoma

exhalant aperture

anterior mandibular

apodeme

SMA AL scaphognathite

mandibular epimeron

Ist maxilliped

epimeron 2nd max.

3rd maxilliped

Srd thoracic epimeron

coxopodite ist pereiopod

Pleural muscle chamber

branchiostegite

ndopleurite

endosternite

position of pleurobranch

arthrophragms

“WW Og

7th thoracic epi merdn

sternal muscle chamber

setiferous process

coxopodite 5th pereiopod articular condyle

male gonopore

“sternum

Fic. 2. Ventral view of cephalothorax of male, showing position of right appendages and left

half of endophragmal skeleton after removal of left thoracic appendages and left branchiostegite.

mal regions of successive epimera are demarcated segmentally by external

indentations, and their contiguous margins are folded and loosely connected

above the dorsal articulations of the coxopodites of the appendages. These

areas form the convex outer walls of the pleural muscle chambers of the limbs,

and those of the last four segments support the pleurobranch gills. The first

two thoracic epimera are small, triangular plates applied to the anterior margin

of the third and largest epimeron, behind which there is a gradual decrease in

the extent of the outlines of the pleural muscle chambers in the fourth to the

eighth thoracic segments. The last thoracic epimeron is produced into a knob

or articular condyle (figs 2, 3, 7, 9, 43) which fits closely like a ‘press stud’ into

a depression on the inner surface of the branchiostegite, so that the postero-

ventral angle of the latter is firmly secured to the side wall of the body. A

conspicuous, triangular setiferous process (figs 2, 7) and a posterior ridge, like-

wise covered with setae, occur ventral to the condyle and surround the dorsal

articulation of the fifth pereiopod. Although distinct from the coxopodite of

18 ANNALS OF THE SOUTH AFRICAN MUSEUM

the fifth pereiopod, the setiferous process is comparable to similar plates on

the coxopodites of other pereiopods, and it and the posterior ridge probably

prevent ingress of water to the branchial chamber between the branchiostegite

and the last leg.

2. ABDOMEN

In the abdominal region, which is broader in the female than in the male,

the six segments are distinct and the exoskeleton of each is divisible into several

well-marked areas (fig. 1). Dorsally there is a wide, convex tergum which is

continuous on each side with a pointed, downwardly-directed pleuron. The

ventral surface is occupied by the sternum which is usually thinner and more

flexible than the tergum, but is strengthened posteriorly in front of the abdo-

minal appendages by a narrow, calcified bar for the insertion of some of the

abdominal muscles. The first abdominal sternum, however, consists largely of

a relatively wide plate, but in front of this there is a pair of oval medial sclerites.

The separation of the latter probably allows of greater flexibility of the thoraco-

abdominal junction, while the division of the posterior bar of the sixth sternum

into two fairly broad sclerites which do not meet in the middle may represent

a similar slight modification associated with movements of the posterior part

of the abdomen. Each abdominal appendage is attached by flexible mem-

branes to the postero-lateral edge of the sternum, and the small ventro-lateral

area between the appendage and the lateral margin of the pleuron is sometimes

referred to as the epzmeron; that of the sixth segment has a rounded protuberance

against which the protopodite of the uropod abuts when the tail-fan is flexed.

The successive abdominal segments are connected with one another by

intertergal and intersternal arthrodial membranes (figs 8, 31) which, by alter-

nate folding and stretching, permit of movements between the segments. As,

however, adjacent segments are hinged together laterally by a process from the

posterior edge of one segment fitting into an anterior depression in the next

segment behind, movement is limited to the vertical plane in which the whole

abdomen is capable of strong extension and flexion. For such movements the

abdominal terga are structurally adapted, each having a smooth anterior

surface (fig. 9) which is exposed during flexure of the abdomen, but slides

beneath and is overlapped by the tergum in front when the abdomen is

extended. When fully flexed, the abdomen is bent under the cephalothorax

and, correlated with this, the broad tail-fan may spread out laterally and

curve ventrally forward, enabling the animal to make escape movements by

darting rapidly backward through the water.

The cephalothorax and the abdomen are also connected by thin arthrodial

membranes, the intertergal one and the smooth anterior half of the first

abdominal segment being overlapped by the inturned posterior margin of the

carapace. In addition, when the abdomen is extended, a forwardly-directed,

lateral flange (fig. 9) on the first abdominal segment fits over the posterior edge

of the carapace, and the two regions of the body are thus practically interlocked.

THE ANATOMY OF THE CAPE ROCK LOBSTER 19

3. CEPHALIC SCLERITES

It is apparent from the foregoing remarks concerning the external features

of the body that the full complement of plates or sclerites of a typical crustacean

segment comprises the dorsal tergum, the ventral sternum, and the lateral

pleura and epimera. The head is considered to consist initially of six segments,

but fusion or cephalization of the parts has taken place, and in the adult, apart

from the paired appendages, there is little evidence of metamerism in the head.

Most of the head appendages, however, articulate with lateral and ventral

sclerites which have been interpreted as analogues of the epimera and the

sterna of thoracic and abdominal segments. Some published opinions con-

cerning similar structures in other species are discussed, and a characteristic

dorsal lobe located in front of the rostrum has been termed the frontal tubercle.

frontal tubercle

pedate process

antennal socket

procephdlic process

dntenna!l epimeron

antennulary sternum

lateral apodeme of epistoma

cpistoma cephalic apodeme

anterior mandibular Sterna 5 & 6

Ist max. tendon

transverse mandibula fused maxillary paraphragms

tendon

epimeron 1st mox.-——“[Wits mn : y endopleurite 1st max.

epimeron 2nd max.

1st & 2nd thor. paraphragms

endosternite 2

ant. process endopleurite 4

posterior mandibular

apodeme

arthrophragm 1

arthrophragm oA

thoracic epimera AY

endosternite

endopleurite 4

sternum

post. process endopleurite 4

paraphragm

“uu OS

rnesophragm

P g endosternite between

thoracic segments 7 & 8

articular condyle

sternal apodeme

sternal canal

posterior endosternite

Fic. 3. Dorsal view of endophragmal skeleton and adjacent parts of cephalothoracic exoskeleton.

20 ANNALS OF THE SOUTH AFRICAN MUSEUM

(a) Frontal tubercle

At the anterior end of the head there is a small, blunt, orange-coloured

projection which is marked by a median suture. It is situated mid-dorsally

antero-ventral to the rostrum and, as Parker (1883, 1884, 1889) has shown, it

corresponds to the region which in other palinurids is enlarged and modified

into the fixed part of the stridulating organ. Parker (1883, 1884) originally

identified it as the antennulary sternum, but later (1889) emended the term

to inter-antennulary bar. Surmounting it and clasping the rostrum is a pair

of forked pedate processes (figs 3, 10, 60, 77), considered by Parker firstly (1883)

as belonging to the antennulary sternum, secondly (1884) as probable out-

growths of the antennulary epimeral plates, and finally (1889) as projections

of the prostomial plate, and this vacillation of opinion serves to emphasize the

difficulties of interpreting the parts of the head, particularly in the Palinuridae.

The frontal lobe of 7. lalandii is situated in the region comparable to that which

Huxley (1881) considered to be the ophthalmic sternum in Astacus, while

Balss (1940) has referred to it as the frontal sclerite of the ocular segment in

Palinuridae. The presence of an ophthalmic segment is questionable and, while

this sclerite lies above the antennules, it is also significant that the basal segment

of the antennal peduncle articulates with it. It has been called the frontal

tubercle (figs 3, 10, 77), but it seems to be merely an anterior projection of the

antennal epimeron.

(b) Cephalic sterna

The antennulary sternum (figs 2, 3, 17) is probably formed by the fusion

of a pair of adjacent narrow sclerites, to which the antennules are attached

ventrally by arthrodial membranes. When viewed from within (fig. 3), it is

obvious that these plates are continuous with marked ridges which curve round

the lateral margins of the antennulary sockets, arch dorsally to the frontal

tubercle, and may represent arthrophragms between the antennules and the

antennae. In addition, there is a median ridge which is shaped like a spearhead

and passes vertically upward to join the presumed antennulary epimeron: this

part is similar to the antennulary sternum described by Huxley (1881) and

separates the antennulary sockets medially, its lateral barbs serving as struts for

the articulation on each side of a strong, dorsal, hinge-like spur (fig. 60) which

passes inward from the base of the first segment of the antennulary peduncle.

The most conspicuous structure on the ventral surface of the head is a

broad smooth plate, the epzstoma (figs 2, 3, 4, 17, 18, 31), the lateral margins of

which are fused with the head exoskeleton. The antennae are joined ventrally

to the anterior border of the epistoma and articulate with it ventro-laterally,

and projecting from the middle of its posterior margin there is a transverse

supralabral ridge (fig. 4.) to which the labrum and a spinous process from each

mandible are attached. A slight postero-median groove marks the position of

an internal median apodeme (fig. 8), and arising on each side of the supralabral

ridge there is a conspicuous lateral apodeme (fig. 3) for the attachment of some of

THE ANATOMY OF THE CAPE ROCK LOBSTER 21

the antennal muscles.

Huxley (1881), Pearson (1908) and others have interpreted the epistoma

as a fusion of the antennal and mandibular sterna. Snodgrass (1951, 1952),

however, has asserted that, being a preoral structure, it represents neither of

these sterna, and has suggested that the mandibular sternum has either disap-

peared or that its vestige is to be found in the postoral metastomal plate. The

whole issue is complicated by embryological events accompanying the backward

displacement of the mouth (Manton, 1928, 1934, 1949). During this process,

the labrum and the stomodaeum shift from a position just in front of the

developing antennae to one in the mandibular segment, so that the antennae

become secondarily preoral. The homologies of the epistoma are therefore

somewhat vague, but it has been concluded that the ventral articulations of the

antennae and the attachment of the antennal muscles to the epistomal apodemes

in J. lalandu probably indicate that the epistoma is a ventral sclerite of the

antennal segment. There is no certainty as to whether or not the mandibular

sternum is bound up with this region, but Balss (1940), who regarded the

epistoma as the antennal sternum, identified the supralabral ridge of Scyllaridea

as the mandibular sternum, and this supposition appears to be substantiated

when it is recalled that the lower articulation of an appendage is with the

sternum of its segment.

It has further been suggested by Borradaile (1907), Calman (1909), and

Balss (1940) that in the Scyllaridea the segment corresponding to the coxopodite

of the antenna of other Decapoda has been incorporated into the epistoma. In

this connexion, it is significant that, in describing the external features of the

genus Puerulus, Ramadan (1938) rejected previous convictions concerning the

homology of its broad inter-antennal sclerite with the epistoma of other groups,

and suggested that it simply represents the concrescence of the proximal seg-

ments of the antennal peduncles, the median suture marking their line of fusion.

In view of the position of the excretory apertures in Palinuridae, Parker (1884,

1889) and Snodgrass (1951) have expressed a similar opinion, contending that

in this family the fused antennal coxopodites have displaced the epistoma, which

is thus reduced to a small, median, transverse sclerite supporting the labrum.

Nevertheless, a comparison of available South African species of Astacura and

Palinuridae suggests that there is no appreciable difference between the large

epistoma of the Astacura and the conspicuous, triangular plate which separates

the antennal bases in the Palinuridae. In both groups the anterior margin of

the plate is indented medially behind the antennules and, furthermore, the.

reduced epistoma of Palinuridae, as interpreted by Parker and Snodgrass,

bears a resemblance to the supralabral ridge of the epistoma of Astacura. In

all the palinurids examined, the region in question is somewhat furrowed medial

to each excretory pore, and in Palinustus mossambicus Brnrd this depression is

accentuated into a distinct groove, which may be an external indication of a

possible fusion of the lateral antennal coxopodite with a median epistoma.

Bearing in mind that the excretory apertures of Astacura are located more or

22 ANNALS OF THE SOUTH AFRICAN MUSEUM

less medially on the antennal coxopodites, it seems likely that the processes

herein identified as lateral apodemes of the epistoma in asus may also partly

represent the lines of fusion of the antennal coxopodites with the epistoma.

Some support for this assumption appears to be given by the resemblance

between the attachments of certain of the basal antennal muscles on these

apodemes and the origins of the corresponding muscles in Astacus (Schmidt,

1915) on the proximal borders of the antennal coxopodites. Moreover, in both

Astacus and Jasus the two ventral cephalic muscles are also inserted on the

lateral apodemes of the epistoma, and have no connexions with the supralabral

bar identified by Parker and by Snodgrass as a reduced epistoma in palinurids;

it is assumed that such connexions would probably be established if the trans-

verse bar in the Palinuridae were a real epistoma. For these reasons, the

definition of the palinurid epistoma given by Borradaile and by Calman has

been retained in describing the parts of 7. lalandiz, but it is conceded that further

comparative studies may be required before the problem can be resolved

satisfactorily.

Apparently there has been less dispute concerning the last two cephalic

sterna (figs 3, 19) which are generally regarded as having coalesced to form a

small, transverse, ventral plate between the bases of the maxillae. In some

Reptantia, however, Snodgrass (1951) has interpreted this as a probable

remnant of the mandibular sternum, termed by him the metastomal plate, and

in his opinion compression of the maxilliped segments has resulted in the fusion

of the maxillary sternum with the maxilliped sternum. While the metastoma

and its paragnaths are attached to the anterior margin of this cephalic sternal

element and are considered by some authorities as likely derivatives of the

mandibular segment, it is also noticeable that the transverse maxillary para-

phragms are associated with this ventral plate and it is thus conceivable that it

belongs mainly to the maxillary region. It is nevertheless possible that part of

the mandibular sternum has also merged with it, for paired processes (figs 3,

19), which are thought to be comparable to the transverse mandibular tendons

described by Manton (1928, 1934, 1964) in a variety of arthropods, occur

anterior to it and the maxillary paraphragms and seem to indicate the presence

of mandibular skeletal elements at this level.

Some of the lateral plates in the head region are more elusive than the

sterna, but all the segments have certain sclerites which may be described as

epimeral. A slightly tuberculated plate, which extends vertically downward

from the overhanging edge of the frontal tubercle to the wide arthrodial

membranes of the antennules, has been suggested as the possible epimeron of

the antennulary segment (figs 17, 60). It forms part of the frontal area of the

head between the bases of the antennae, and corresponds to the region deter-

mined as the antennulary sternum in Astacus by Huxley (1881) and in pali-

nurids by Parker (1884) and Balss (1940). The later author distinguished it as

THE ANATOMY OF THE CAPE ROCK LOBSTER 23

the proepistoma, while Snodgrass (1951) defined it as the head plate in Panulirus

argus.

Underlying the eyestalk and the pedate process and curving forward to

meet the frontal tubercle, there is a broad transverse plate to which the basal

segment of the antennal peduncle is attached dorsally by an arthrodial mem-

brane. While Huxley (1881) regarded it as the antennulary epimeron in

Astacus, it seems as though it may be interpreted equally well as the epimeron

of the antennal segment (fig. 3) and, as previously suggested, it probably forms

the frontal tubercle with which the dorso-medial articulation of the antenna

takes place.

supralabral ridge labrum

epistoma

LEGS mandibular palp

Aire

n SKE. ON

o excretory pore S Aa Lf > has exhalant aperture

3 r —

: mandible

eas

mandibular epimeron cg

(ES a

mouth

left paragnath

reflected Ist max,

epimeron 1st max. mandibular condyle

e€pimeron 2nd max. fused maxillary paraphragms

second maxillary socket

first thoracic epimeron

Fic. 4. Ventral view of mouth region; the left first maxilla has been reflected to show the

metastoma and the paragnath, and the branchiostegite on each side has been removed to

expose the roof of the prebranchial chamber.

On each side of the mandibular segment, the epimeron (figs 2, 4) is repre-

sented by the anterior two-thirds of the thin, arched roof of the prebranchial

chamber. Towards its posterior limit the condyle of the mandible articulates

with it, while anteriorly it lies beneath the anterior mandibular apodeme and

unites with a transverse extension of the epistoma which forms the upper

boundary of the exhalant aperture of the respiratory system and has been

called the wing of the epistoma by Snodgrass (1951, 1952).

The first and second maxillary epimera are indistinctly demarcated from

each other, but the former (figs 3, 4) may be manifest in a narrow ridge

which separates the mandibular epimeron from the second maxillary epimeron.

The latter (figs 2-4) is a fairly broad plate occupying the posterior third of the

roof of the prebranchial chamber, and is comparable with the maxillary

pleural bridge described by Snodgrass (1951) in Astacura and Palinura.

C. APPENDAGES (Fig. 5)

The paired appendages occur on most of the body segments, to which they

are attached by arthrodial membranes and are usually articulated by two

24 ANNALS OF THE SOUTH AFRICAN MUSEUM

joints located more or less opposite each other on the epimera and the sterna

of their respective segments. The complete series of appendages and their

corresponding segments may be summarized as follows:

CEPHALON: Segment 1-— Embryonic and transitory, without appendages

ie 2 — Antennules

‘ei 3 — Antennae

Bs 4 — Mandibles

5 5 — First maxillae

39 6 — Second maxillae

THORAX: Segment 7 - First maxillipeds

“, 8 — Second maxillipeds

ss 9 — Third maxillipeds

Gs 10 — First pereiopods

a 11 — Second pereiopods

5 12 — Third pereiopods

* 13 — Fourth pereiopods

35 14 — Fifth pereiopods

ABDOMEN: Segment 15 — Appendages absent in both sexes

Fs 16 — First pleopods

Be 17 — Second pleopods

A 18 — Third pleopods

sm 19 — Fourth pleopods

% 20 — Uropods

Most of the limbs are biramous and distinctly jointed and thus conform to

the stenopodium type of crustacean appendage, but in the arrangement of their

lamellate parts the first and the second maxillae are suggestive of phyllopodia.

Like the stenopodia, the phyllopodia are biramous, the stem carrying medial

lobes or endites and lateral lobes or exites. The parts, however, are broader and

less cylindrical than those of a stenopodium and are interconnected by thin

flexible membranes; joints are absent and turgor is maintained chiefly by

internal pressure.

A typical stenopodium, as exemplified by the third maxilliped (fig. 5 H),

consists of a basal protopodite which supports two rami, an inner endopodite and

an outer exopodite. The protopodite (fig. 16) usually has two segments, the coxopo-

dite and the basipodite, while the endopodite is divisible into five segments, namely

(fig. 16), the zschiopodite, the meropodite, the carpopodite, the propodite, and the

dactylopodite. In each maxilliped an exopodite, featuring a peduncle and a

tapering flagellum, is attached to the basipodite, while arising from the coxopo-

dite there is a setiferous process which commonly supports a thin respiratory

lamella, the epipodite, and a podobranch gill. Nowadays it is customary to

shorten the above terms by omitting the terminal ‘ite’ but, as the longer ver-

sions have been used in naming the appendicular muscles, they have been

retained here. Thus the parts of the endopodite (endopod) may be abbreviated

THE ANATOMY OF THE CAPE ROCK LOBSTER 25

membrane peduncle joint

20 mm.

endopodite AN

site“ NA

WwW Of

10 mm.

an D. 18§ MAXILLA.

post. apodeme.

exopodite

podobranch E. 2"¢ MAXILLA,

endopodite

epipodite

= endopodite

f exopodite

setiferous process

ww OL

podobranch

~g St MAXILLIPED.

10 mm.

epipodite

protopodite

exopodite

10 mm.

1 8 _PEREIOPOD

SMALL_MALE. _ J. sth peEREIOPOD

SMALL MALE.

L. MALE PLEOPOD.

endopodite

: K sth pEREIOPOD

SMALL FEMALE.

protopod ite

appendix interna

protopodite

‘ ie Banconodite

See Y

Jp phi

ovigerous '*)!

setae

20 mm.

M FEMALE PLEOPOD.

2nd Abdom. Seg. ug,

N. FEMALE PLEOPOD. * O. UROPOD.

5th Abdom. Seg.

Fic. 5. Appendages of right side, drawn from various aspects to iJlustrate some of their respective

structural features. Ventral views are given of the antenna, the mandible, the male pleopod,

and the uropod; caudal views of the pereiopods; and dorsal views of the other appendages.

B, basipodite; CA, carpopodite; CO, coxopodite; D, dactylopodite; J, ischiopodite: M, meropo-

dite; P, propodite; f.c.e., precoxal endite of second maxilla.

26 ANNALS OF THE SOUTH AFRICAN MUSEUM

to ischium, merus, carpus, propodus, and dactyl, and the two segments of the

protopodite (protopod) may be referred to as the coxa and the basis.

Various modifications of the generalized type which are apparent in

several of the appendages are: the flat, unsegmented endopodite of both pairs of

maxillae and the first maxilliped, the fusion of such parts as the basipodite with

the ischiopodite in limbs behind the first maxilliped, and the absence of exopo-

dites in the anterior cephalic appendages and all the pereiopods. Exopodites are

present, however, on the pereiopods of the phyllosoma larva, but become

reduced in the puerulus stage to small, vestigial protuberances which, according to

Gilchrist (1920), aresuppressed during transformation into the post-puerulusstage.

I. ANTENNULE (Fig. 5 A)

The antennule, which is connected by wide arthrodial membranes to the

head exoskeleton, projects forward from the middle of the frontal region, its

base being somewhat concealed dorsally by the large antenna. As in other

Decapoda, it consists of a long, slender, three-segmented peduncle which bears

two short distal flagella. The first segment of the peduncle is the longest and is

about equal in length to the combined measurements of the other two segments.

Located in its somewhat swollen base is a balancing organ or statocyst, the

position of which is indicated by a lighter dorsal area which is bordered by

ridges and setae (fig. 67). Antero-medially between the ridges is the small

aperture through which the statocyst communicates with the exterior (fig. 60).

The homologies of the parts of the antennule with those of other appen-

dages are doubtful, but it is apparent from Gilchrist’s (1913, 1916) descriptions

of the naupliosoma larva of 7. lalandii that the antennules are primarily uni-

ramous and that the two terminal flagella appear in the 24 mm phyllosoma

larval stage. In the nauplius larva of other Crustacea and in adult non-

malacostracans the antennules are also uniramous, and the suggestion that the

antennulary flagella of adult Malacostraca represent the exopodite and the

endopodite of a generalized appendage is not universally accepted. Assuming

that the antennule was biramous, Huxley (1881) and Pearson (1908) naturally

concluded that the whole of the peduncle was the protopodite, but Gilchrist &

Von Bonde (1922) have identified the first peduncular segment of the antennule

of F. lalandit as the protopodite and the other two segments as the endopodite.

To some extent, this latter view appears to be substantiated by the musculature,

from which there is evidence that the proximal segment may be double and

may represent the fused coxopodite and basipodite. It would therefore seem

that the antennules of 7. lalandii are not strictly biramous and that they are

more accurately described as biflagellar appendages.

Both flagella have membranous connexions with the distal margin of the

third peduncular segment, and each is multisegmented, relatively broad near

its base, and produced distally into a curved pointed tip. The widest part of

each flagellum is furnished with setae which are arranged in regular rows on

each annulus. Those on the slightly longer and narrower inner flagellum comprise

THE ANATOMY OF THE CAPE ROCK LOBSTER 27

rather stiff feathered hairs along the dorsal margin and softer plumose setae,

edged by stiff bristles, along the ventral rim (fig. 65). Most of the surface of the

outer flagellum is beset with long, delicate, colourless, partly annulated setae,

the aesthetascs (fig. 66), which are bordered laterally by conspicuous bristles.

The outer flagellum, which fits basally into a relatively deep lateral cleft on

the distal margin of the third peduncular segment, vibrates constantly against

the slightly concave lateral surface of the rather more porrect inner flagellum.

The setae of the two flagella thus impinge on one another, and the different

types are doubtless correlated with the several functions attributed to the

antennules. While handling experimental animals, it was observed that the

outer flagellum was the last external structure to show signs of movement in

moribund specimens and, on cessation of its activity, death could be presumed.

2. ANTENNA (Fig. 5 B)

As in other Scyllaridea, the antenna is uniramous in the adult, the exopo-

dite being lacking, but Gilchrist (1913), 1916) has shown that in the

naupliosoma larva it is a biramous, locomotory appendage, the exopodite of

which gradually diminishes during the various phases of the phyllosoma larva

until it atrophies in the 24 mm stage. The adult appendage thus consists of a

stout, three-segmented peduncle and a very long, tapering flagellum. Calman’s

(1909) statement that the decapod antennal peduncle is primarily five-

segmented, the two proximal segments representing the protopodite and the

other three segments the first three parts of the endopodite, seems to imply that

either the dactylopodite is absent or that it has fused with the propodite to form

the flagellum. The reduction of the peduncle of Scyllaridea to three segments is

assumed to have been effected by concrescence of the basal segment (coxopo-

dite) with the epistoma and the fusion of the second and third segments (basi-

podite and ischiopodite) which are commonly united in other appendages of

Reptantia. A comparison of the antennal muscles of 7. lalandit with Schmidt’s

(1915) description of the system in Astacus apparently confirms these conclusions

regarding the modification of the base of the scyllarid antenna. A resemblance

between the musculature of the more distal segments of both forms is also

indicated but, in view of Balss’s (1940) criticism of Schmidt’s interpretation of

the parts of the peduncle of Astacus, it seems likely that the second and third

segments in 7. lalandii correspond to the meropodite and the carpopodite of

other forms; whether or not the flagellum is a combination of the propodite

and the dactylopodite is still uncertain.

The segments of the peduncle are spinous and covered with squamae;

they are strongly jointed together and the action of their powerful muscles

produces the sudden elevation and lashing movements of the whip-like fla-

gellum. Although the latter is multisegmented, it is rather rigid and easily

broken. It is usually as long as or even longer than the body, has incomplete

rings of stiff setae, and is generally dark coloured, but several pale bands are

normally present.

28 ANNALS OF THE SOUTH AFRICAN MUSEUM

As a result of the supposed fusion of the antennal coxopodite with the

epistoma, the paired excretory organ, instead of discharging on the proximal

segment of the antenna as in most Decapoda, opens ventro-laterally on the

epistoma (figs 2, 4, 38); in certain other South African palinurids examined,

the apertures tend to be more posterior and occur nearer the outer angles of

the triangular epistoma.

3. MANDIBLE (Fig. 5 C’)

The mandible has no exopodite and bears little resemblance to a typical

stenopodium. Following Borradaile’s (1917) deliberations, however, it seems

likely that its strongly-calcified body and broad gnathal lobe (fig. 19) represent

the fused coxopodite and gnathobase (precoxa) of a generalized appendage,

while the three segments of the short palp correspond to the basipodite and two

parts of the endopodite. The two palps curve inward towards the mid-line

between the labrum and the anterior margins of the gnathal lobes, assisting in

the manipulation of food and preventing any loss from the anterior border of

the mouth. Whereas in many Caridea the gnathal lobe is characterized by

pronounced incisor and molar processes and is a powerful chewing organ, in

Jasus and other Reptantia these processes are not clearly differentiated and the

appendage is less effectual in shredding the food. A blunt, tooth-like projection,

which perhaps replaces the incisor process of the mandible of other decapods,

is demarcated by an antero-medial indentation, and that of the left mandible

is consistently the more protuberant. With the exception of Palinustus mossam-

bicus Brnrd and Linuparus trigonus (Von Siebold), the mandibles of other

South African Palinuridae in the South African Museum collection have

similar asymmetrical anterior processes; but these are distinguished from the

whitish process of Jasus lalandii and fF. tristani Holthuis in that either both of

them, as in Projasus parkert (George & Grindley) and Palinurus gilchristi Stebb.,

or only the right one, as in Panulirus homarus (L.) [Panulirus biirgeri (De Haan)],

Panulirus ornatus (Fabr.), and Panulirus versicolor Latr., has a reddish-brown cap.

Behind this process, the broad gnathal surface has a fairly sharp ventro-medial

edge and a few blunt tubercles and shallow depressions. The edge of the right

mandible underlies and is usually finer than that of the left side and, as the

marginal contours of the pair fit together precisely, the food is grasped tightly

and compressed when the mandibles are in apposition. Laterally the body of

the mandible is produced into a hollow, rather thin-walled, dome-shaped

anterior apodeme (figs 2, 3, 5, 19) which lies below the hepatic region of the head

exoskeleton and provides attachment for some of the mandibular muscles,

while its concavity is almost filled by a portion of the digestive gland. Near the

base of the palp there is a tuft of finely-feathered setae which may have some

functional significance, for it is located behind the excretory pore at the ventral

border of the exhalant aperture (figs 2, 4) through which the current of spent

respiratory water flows from the prebranchial chamber.

Although the mandible has powerful muscles, its movement is restricted

THE ANATOMY OF THE CAPE ROCK LOBSTER 29

to the transverse plane because it articulates dorsally by a postero-lateral condyle

(figs 4, 5, 19) with the mandibular epimeron in the roof of the prebranchial

passage, and close to the base of the palp it has a long spinous process which is

projected medially and is firmly attached to the margin of the supralabral

ridge. Snodgrass (1950, 1952) identified the latter as the epistoma in Palinura

and, accordingly, he considered the spinous process to have a marginal epi-

stomal hinge and an apical epistomal articulation. The slender but strong

posterior apodeme (figs 3, 5, 19) for the insertion of the posterior adductor muscle

of the mandible is attached to the hinder margin of the body of the mandible;

it passes vertically into the head and forms an obvious landmark at the side

of the fore-gut.

4. FIRST MAXILLA (Fig. 5 D)

Characteristically, the first maxilla is a small flattened appendage which

is closely applied to the lower surface of the ipsilateral paragnath. The exopo-

dite is lacking and the endopodite is a short fairly flexible process with relatively

long terminal setae. The protopodite is strengthened by a number of ventral

sclerites and is produced into two stout median endites. The latter are often

referred to as the coxopodite and the basipodite, but they have been defined as

the inner and the outer laciniae by Borradaile (1917, 1922), who concluded that

they probably represent the first and the third endites of a generalized crusta-

cean limb. Thus, the proximal endite would correspond to a gnathobase, while

the area lateral to it is the true coxopodite and the outer endite is a process

of the basipodite. At the same time, at the base of the proximal endite in

Jj. lalandii there is an additional, small, median lobe which resembles a reduced

precoxal endite. In his description of the first maxilla of Fasus edwardsii, Parker

(1889) also used the term laciniae for the endites, but he subscribed to the

belief that the inner process is supported by the basipodite and the outer

process by the ischiopodite, and considered that they are, therefore, not

strictly homologues of the endites and the laciniae of other appendages. The

two endites probably work independently, and their medial margins are

furnished with strong spines which meet those of the endites of the contralateral

first maxilla in the mid-line and assist in the retention and comminution of the

food. The inner and smaller endite has an indented posterior margin, and its

sclerotized base is concave dorsally where it abuts on the base of the paragnath.

This endite curves medially towards the mouth between the metastoma and the

paragnath, and appears to function mainly in thrusting food into position

between the mandibles. Two other noticeable features are the long tendon for

the insertion of the abductor muscle and the tuft of long plumose setae located

on a lateral sclerotized area which may be likened to a setiferous process of the

coxopodite.

5. SECOND MAXILLA (Fig. 5 £)

The second maxilla is considerably larger than the first maxilla and is

remarkable for its modification into a flattened, thin-walled organ which is an

30 ANNALS OF THE SOUTH AFRICAN MUSEUM

essential part of the respiratory system. It consists of three main regions, namely,

the protopodite, prolonged medially into three slender endites; a flat, subtriangu-

lar, rather more heavily sclerotized endopodite; and its most striking feature, a

broad curved plate, the scaphognathite or ‘baler’, which has variously been inter-

preted as representing an enlarged exopodite, an epipodite, or a combination of

both of these elements. In many decapods the second maxilla is provided with

four endites, and Borradaile (1917, 1922) has suggested that the first belongs

to the precoxa, the second to the coxopodite, and the third and fourth to the

basipodite. From this it would seem that the two outer lobes in 7. lalandii are

basipodite endites and the inner one a coxopodite endite. Near the base of the

latter is an inconspicuous lobe which may be comparable with the more

obvious precoxal endite of other forms. The margins of most of the parts are

fringed with finely plumose setae, and the endites seem to be too delicate to

be effective in feeding. In any case, the second maxilla is located in the pre-

branchial chamber some distance lateral to the mouth: it lies almost hori-

zontally, with the anterior tip of the scaphognathite reaching the exhalant

aperture and the posterior end, with its rather stiff setae, curving into the antero-

dorsal part of the branchial chamber. The whole appendage is attached by a

soft arthrodial membrane and moves freely. The action of the scaphognathite

was not fully investigated in living animals but, as its movements are more or

less dorso-ventral and sinuous, it is assumed that water is scooped up from the

anterior part of the branchial chamber and propelled into the prebranchial

chamber by the upturned posterior half of the lamella. It is then driven forward

and expelled through the exhalant aperture by the undulation of the anterior

half of the scaphognathite. In resting animals the anterior tips of the scaphog-

nathites were observed to beat rhythmically up and down at the exhalant

apertures at the rate of about 110 to 120 times a minute. The action of the

two scaphognathites was not always synchronized, and in restive animals the

frequency is probably higher.

One of the salient features of the Decapoda is that the first three pairs of

thoracic appendages, the mavxillipeds, are directed forward and serve as accessory

mouth-parts.

6. FIRST MAXILLIPED (Fig. 5 F)

The first maxilliped, although fundamentally a stenopodium, is largely a

flattened lamellar appendage, situated to the side of the mid-ventral line

behind the first maxilla. As in the latter appendage, the protopodite bears two

endites which are interconnected along their adjacent margins by a very narrow

membrane, and each has rows of strong setae on its somewhat obtuse medial

margin. The endopodite is a small, flat, unsegmented lobe, the medial margin of

which is joined to endite 2, while the lateral margin, with its fringe of long

setae, rests against the inner wall of the exopodite. The latter is conspicuous and

typical of stenopodia in having a stout peduncle and a curved, flexible and

active flagellum which usually consists of 16 segments. The exopodite underlies

THE ANATOMY OF THE CAPE ROCK LOBSTER 31

the second maxilla; its peduncle is flattened laterally to form the floor of the

prebranchial chamber and projects in front of a broad thin-walled epzpodite,

the surface of which bears long thread-like setae. The epipodite is attached to a

small setiferous process and arches dorsally behind the scaphognathite of the

second maxilla, forming a vertical partition between the prebranchial and

branchial chambers and having its lateral margin firm and thickened where it

comes into contact with the branchiostegite.

7. SECOND MAXILLIPED (Fig. 5 G)

The second maxilliped is distinguished from the first maxilliped by its

more pediform appearance. The two parts of the protopodite, the coxopodite and

the basipodite, are aligned with the five segments of the endopodite, the whole

forming a strong forwardly-directed shaft in which all the segments, except

the united basipodite and ischiopodite, are movable on one another by joints

that are essentially similar in position to those of the pereiopods (fig. 16). The

endopodite is applied to the mouth region and its parts are somewhat flattened.

The meropodite is the longest segment and the three terminal segments are

short and broad. The anterior margin of the propodite is curved and fringed

with stiff setae, in addition to which there are four or five strong lateral spines.

The small dactylopodite is almost semicircular in shape and is usually furnished

with nine terminal spines. Flexure between the short carpopodite and the

meropodite carries the two distal segments towards the mid-line so that their

spines meet those of the contralateral second maxilliped. The basipodite is

longer than the ischiopodite and, as in other appendages, attached to it is the

exopodite. The latter resembles that of the first maxilliped in having a

16-segmented flagellum, but its peduncle is more cylindrical. On the medial

margin of the broad coxopodite is a rounded, setose lobe which probably acts

as a gnathobase, and articulating laterally with the coxopodite is a setiferous

process which supports a conspicuous, thin-walled epzpodite and a podobranch.

8. THIRD MAXILLIPED (Fig. 5 H)

The third maxillipeds are longer and stronger than the second maxillipeds

and project forward covering the other mouth-parts ventrally. The endopo-

dite has the same number of segments as that of the second maxilliped, but

differences in the lengths of the parts are apparent. The basipodite is rather

short, while the ischiopodite and the meropodite are subequal in length and

their flattened medial surfaces are covered with tufts of strong setae which

tend to obscure a row of small blunt teeth arranged along the dorso-medial

edge of the whole of the ischiopodite and the proximal half of the meropodite.

As in the second maxilliped, marked flexure occurs between the meropodite

and the short carpopodite, and the two terminal segments are turned somewhat

obliquely towards the mid-line and reflexed on the medial border of the mero-

podite. The dorsal surface of the propodite is furnished with long setae and the

whole surface of the dactylopodite has tufts of shorter setae. When the car-

32 ANNALS OF THE SOUTH AFRICAN MUSEUM

popodite flexes, the conical dactylopodite approximates the mouth and the

spinous anterior margin of the second maxilliped of the same side. The coxopo-

dite has a medial protuberance resembling a gnathobase, and laterally there is

a setiferous process bearing an epipodite and a podobranch. The exopodite, which is

attached to the basipodite, is proportionally shorter than that of the first two

maxillipeds, and its flagellum commonly has 12 segments. In describing the

specific features of Fasus lalandii, Gruvel (1911) commented on the dissimilarities

of the exopodites of the three pairs of maxillipeds and concluded that there

were 16 or 17 flagellar segments in the first two pairs and 11 segments in the

third maxillipeds. The numbers, however, are by no means constant, and 13

or even 15 segments have been counted in the exopodite flagella of the third

maxillipeds of several specimens selected at random.

Q. PEREIOPODS (Fig. 5 -F)

Apart from a few minor points, the five pairs of pereiopods are structurally

alike. Moreover, the only significant differences between them and the third

maxillipeds are the suppression of the exopodites and the elongation and

strengthening of the endopodites, which are thus adapted to support the body

and act as walking legs. The longest segments are the meropodite and the pro-

podite which are slender and generally subequal in length. As in the third

maxilliped, the basipodite and ischiopodite are fused and the limb can be

flexed acutely between the meropodite and the carpopodite.

The orientation of the segments is largely determined by the position of

the articulating jomnts (figs 1, 16, 25) on which the several segments swing in

different planes and so effect the movement of the appendage as a whole. The

coxopodite has dorsal and ventral joints which articulate respectively (fig. 7)

with the epimeral and sternal plates of the skeleton and permit the limb to be

moved forward and inward and pulled backward and outward in the hori-

zontal plane. The conjoined basipodite and ischiopodite articulate with the

coxopodite by antero-ventral and postero-dorsal joints and the movement is

upward and downward in a vertical direction. The elongate meropodite has

ill-defined dorsal and ventral joints and is nearly rigid, being capable of only

slight independent to-and-fro movements, but its orientation is largely influ-

enced by the action of the preceding segments. The joints of both the car-

popodite and the dactylopodite are anterior and posterior in position and the

segments swing vertically, while the propodite, which has dorsal and ventral

joints, moves transversely on the carpopodite. The successive limb segments are

interconnected by arthrodial membranes and, while the carpopodite shows the

greatest freedom of movement, the propodite is almost as mobile even though

its joints differ from those of the carpopodite.

Different types of locomotion and modern ideas concerning the mechan-

isms involved in the movements of the limbs of Crustacea have been discussed

by Lockhead (1961) and Wiersma (1961), and the results of intensive research

on locomotion in a great variety of arthropods have been presented by Manton

THE ANATOMY OF THE CAPE ROCK LOBSTER 33

(1958, 1964, 1965, and earlier articles). Three main types of joints have been

distinguished by Manton (1958, 1965) in the legs of Diplopoda and Chilopoda.

These are the joint between the coxa and the body and two functionally distinct

kinds of intersegmental leg articulations which Manton has called pivot joints

and hinge joints. Pivot joints are located on the anterior and posterior surfaces

of the leg, and ‘the axis of movement passes horizontally through the middle of

the overlapping leg segments’ (1958: 504). Hinge joints, which occur at the dorsal

junctions of leg segments, are operated mainly by flexor muscles. Precise

structural and functional details of the joints of diplopod and chilopod legs

and the properties of the cuticle have been given by Manton, but these aspects

have yet to be investigated in Jasus. In position and function, the anterior and

posterior joints of the basipodite, the carpopodite, and the dactylopodite of a

jasus pereiopod are comparable to the pivot joints of diplopod legs, while the

dorsal and ventral joints of the meropodite and the propodite are analogous

to hinge joints. Whereas the meropodite has only reductor muscles and its

movements are limited, the propodite is provided with antagonistic reductor

and productor muscles and its range of movement is probably equivalent to that

of the diplopod leg segments which have dorsal hinge joints and flexor muscles.

In addition to differences in the position of the gonopores (figs 2, 80),

sexual dimorphism is apparent in a few structural peculiarities of certain of the

limbs. In both sexes the first pair of pereiopods is shorter than the others, and

not chelate as in many Reptantia, but they are furnished with the sharp spines

described by Milne Edwards (1837) in his original account of the species. They

are also usually directed forward, and the medial surfaces of the dactylopodites

and the distal half of the propodites of the right and left limbs can be approxi-

mated and are markedly setose in both sexes. In the male the first legs (fig. 5 /)

are robust and strongly flexed between the meropodite and the carpopodite,

while in the female (fig. 16) they tend to be slightly straighter and more

slender. In all the pereiopods the dactylopodite forms a strong pointed claw,

the tip of which may be used for scraping and cleaning parts of the exoskeleton

or for clinging to rock surfaces, while the dactylopodites of the last three pairs of

legs normally act as a support for the body when the animal is resting or walking

on the substratum. The dactylopodite of the fourth pereiopod of both sexes

and also that of the fifth leg of the male (fig. 5 7) has five or six pairs of strong

ventral spines, more or less replacing the tufts of setae present on the other

dactylopodites. In the female the fifth pereiopod (fig. 5 A) is chelate, the

pincer being formed by the dactylopodite working against a relatively short,

pointed, slightly movable projection of the lower distal edge of the propodite.

Paired, stiff spines are also present on the under surface of the dactylopodite of

the fifth pereiopod of young females, but seem to become reduced in number

in mature forms and obscured by a horseshoe-shaped brush of short, fairly

stout setae, into the midst of which the tip of the propodite process fits when

the dactylopodite is flexed. The main function of the chela only becomes

apparent during the breeding season when it is used by females ‘in berry’ to

34 ANNALS OF THE SOUTH AFRICAN MUSEUM

arrange and clean the eggs and to remove the empty egg-capsules from the

ovigerous setae of the pleopods. These events have been reported by Gilchrist

(1913a), Von Bonde & Marchand (1935), Fielder (19645), and Grua (1964),

and have also been observed in captive females during the present study.

An epipodite and an accompanying podobranch, similar to those of the

third maxilliped, are attached to the setiferous process of the coxopodite of all

except the last pereiopod, opposite which the only gill is a pleurobranch.

10. PLEOPODs (Fig. 5 L—NV)

On the second to the fifth abdominal segments in both sexes there are

paired appendages or pleopods which are sexually dimorphic. They all agree

in having a short protopodite which is distinctly divisible into a narrow,

ventrally incomplete coxopodite and a somewhat larger basipodite, but they

differ in that the female pleopods are biramous, while those of the male are

uniramous. The female pleopods are larger than those of the male, the pair on the

second abdominal segment (fig. 5 17) having subequal, flexible, foliaceous

exopodite and endopodite which, with the exopodites of other pleopods enfold

the eggs in the ovigerous females. The pleopods on the third, fourth, and fifth

abdominal segments (fig. 5 JV) are distinguished by the reduction of the endo-

podite to a somewhat cylindrical rod which in mature females is furnished with

long non-plumose setae to which the eggs are attached during the breeding

season. The proximal segment of these endopodites bears a remnant of the

lamella observed in the first pair of pleopods, and in each of the female pleopods

the endopodite has a distal conical projection, the appendix interna. The latter

is particularly well marked in the biramous pleopods of the puerulus stage

(fig. 6), where it is about equal in length to the relatively long setae fringing

_-coupl ing hooks

protopodite

Fic. 6. Ventral view of right pleopod on second abdominal segment of a 22 mm long puerulus

stage.

both the endopodite and the exopodite, and bears a subterminal seta and a

group of six or seven terminal coupling hooks for connecting the pleopods in

THE ANATOMY OF THE CAPE ROCK LOBSTER 35

pairs when they are used in swimming. Gilchrist (1920) has indicated that the

change from the puerulus to the post-puerulus condition is accompanied by

the disappearance of the seta and the coupling hooks on the appendix interna,

and also that sexual dimorphism becomes manifest for the first time in the

progressive differentiation of secondary sexual characters in the pleopods of

the developing males and females.

The basipodite of the male pleopod (fig. 5 L) only supports a relatively small,

oval, lamellar exopodite, the endopodite having practically disappeared and

being represented at most by a minute, pointed, medial process on the basi-

podite. In small specimens of the closely-related asus tristant Holthuis and in

Projasus parkert (George & Grindley), however, traces of a biramous condition

are still evident in the male pleopods, each having a vestigial but recognizable

endopodite, which in the first pair of pleopods of both species is distinctly

lobular and setose. This may indicate that the pleopods of the males of these

two species are structurally closer to the possible ancestral type than are those

of 7. lalandii and other Palinuridae in which the remnant of the endopodite is

hardly discernible on the male appendages.

II. UROPODs (Fig. 5 O)

The uropods are alike in both sexes, being larger than the pleopods and

heavily sclerotized. The two segments of the protopodite are inseparably fused

and the exopodite and endopodite are broad lamellae, equal in length to the

telson, with which they form the tail-fan. The lateral margins of the telson and

the exopodites and endopodites of the uropods are markedly serrated, and the

dorsal surfaces have rows of backwardly-directed spines, each fringed with

setae.

D. AuTOTOMY AND REGENERATION OF APPENDAGES

Autotomy, or reflex amputation of an injured appendage, is a phenomenon

characteristic of a number of Arthropoda and, among decapod Crustacea, it is

said to occur in all Brachyura, most Anomura, and some Macrura. Having

regard to the recent critique of autotomy and various aspects of regeneration in

Crustacea by Bliss (1960), only two other publications need be cited, namely,

Pearson’s (1908) description of the process in Cancer pagurus and the more

comprehensive account by Wood & Wood (1932) of the mechanism in a wide

range of Crustacea.

According to the latter authors, autotomy is strictly a reflex response to

external stimulation that induces an injured pereiopod to break off cleanly

along the suture which demarcates the basipodite from the ischiopodite. Of the

various designations given to the line of detachment, Pearson’s (1908) ‘fracture

plane (fig. 16) is concise and apposite, and seems preferable to other terms

mentioned by Bliss (1960).

Two additional closely related phenomena, which have been distinguished

from autotomy by Wood & Wood (1932), are autospasy and autotilly. The former

36 ANNALS OF THE SOUTH AFRICAN MUSEUM

term describes the rupture of a limb at the fracture plane when it is seized and

pulled by an outside agent; autotilly is the removal of a limb along the fracture

plane by the action of other appendages of an injured animal.

A significant feature of the mechanism involved is that no muscles pass

across the fracture plane from the basipodite into the ischiopodite, and Wood

& Wood (1932) and Bliss (1960) have demonstrated that the main levator

(levator a, fig. 26) or ‘automizer’ muscle, which is inserted by a long tendon

rostro-laterally on the proximal margin of the basipodite, is responsible for

the breakage of the limb. Normal contraction of this muscle elevates the fused

basipodite and ischiopodite, but undue contraction of the muscle causes these

segments to be pressed so strongly against the distal margin of the coxopodite

that they separate along their weakest point, the fracture plane.

When the distal part of the limb has been discarded by autotomy or auto-

spasy or autotilly, the stump is covered by a thin diaphragm to which, according

to Wood & Wood (1932), the pedal artery and nerve are so attached by con-

nective tissue that they are also severed at a fixed point. Excessive bleeding is

prevented by a valvular structure, and the small quantity of blood that exudes

forms a scab, beneath which a small limb bud is soon formed for the regeneration

of the limb segments. The time required for the complete regeneration of a

limb seems to vary in different Decapoda and several successive moults may

take place before the limb attains its normal proportions.

Apart from occasional fracture of the pereiopods and antennal flagella

while handling live specimens and indications of rather thin regenerated limbs

and the presence of a dark brown scab on an amputated leg in some captive

animals, no attempt was made to analyse these events in the course of the

present study. Bradstock (1950), however, has reported autotomy and auto-

spasy of the pereiopods and autospasy of the antennae in Fasus collected off

Wellington, New Zealand; in these animals autotomy of the pereiopods was

more frequent in females than in males, and a period of a year was required for

the complete regeneration of an antennal flagellum lost by autospasy.

E. ExTERNAL APERTURES

The mouth (figs 4, 31) is a mid-ventral opening between the mandibles,

and is obscured by the forwardly-directed maxillipeds. In addition to soft

lateral lips, it is bounded anteriorly by an upper lip, the /abrum, and posteriorly

by a lower lip, the metastoma. Both of these are cushion-like, fleshy structures,

the exposed surfaces of which are strengthened by sclerites. The hood-like

labrum (figs 3, 4, 8, 31) is attached to the posterior edge of the supralabral ridge

and is continued postero-medially into a soft process which extends between

the mandibles and overhangs the mouth. The metastoma (fig. 4) has a deep mid-

ventral groove and is produced basally into a pair of conspicuous lobes, the

paragnaths. Each forwardly-directed paragnath (fig. 4) is intercalated between

the mandible and the first maxilla and is closely applied to the ventral surface

of the former, as well as being confluent with the lateral lips.

THE ANATOMY OF THE CAPE ROCK LOBSTER 37

The anus (fig. 31), situated ventrally on the telson, is an elongate aperture

flanked by a pair of strong semilunar lobes. At the base of each lobe there is a

longitudinal depression for the insertion of the dilatator muscle of the anus,

while antero-laterally another groove marks the insertion of the anal com-

pressor muscle.

The excretory apertures (figs 1, 2, 4, 38, 39, 43) are crescentic slits on the

surface of an obvious pair of tubercles which are located laterally on the

epistoma and seem to be slightly more anterior in position than those of some

other South African palinurids examined.

The exhalant apertures (figs 2, 4, 43), through which the spent respiratory

water is expelled, are situated ventro-laterally behind the excretory apertures.

The male gonopores (fig. 2) occur ventrally on the coxopodites of the last

pair of pereiopods; each is a semicircular opening partly overlapped by a

cuticular flap.

The female gonopores (fig. 80) are two crescentic apertures on the ventral

surface of the coxopodites of the third pair of pereiopods.

F. Foop AND FEEDING MECHANISM

Chace & Dumont (1949) have remarked that palinurids in general are

omnivorous and, in so far as experimental animals are known to select fresh

rather than decomposing food, they are not altogether scavengers. From obser-

vations of the feeding habits of captive and free-living animals, Lindberg

(1955) has concluded that Panulirus interruptus is primarily a scavenger, and the

composition of the stomach contents suggests that it is an omnivore, while

Sheard (1962) has also expressed the opinion that Panulirus cygnus is omnivorous.

Although a number of investigators have reported that the fore-gut of

jasus is either empty or contains only portions of the bait used in trapping the

animals, some idea of its natural food is gradually emerging. Gilchrist (19132)

styled 7. lalandii as a scavenger and stated that small specimens were occa-

sionally cannibalistic on larger soft-shelled individuals, but he also noted the

remains of mollusc shells in analyses of the stomach contents and observed that

captive animals would eat live Turbo and the spines of living echinoids. It is

obvious, however, that the diet depends on the food available in different

localities. In the gut contents of Tasmanian specimens Hickman (1945) has

identified the remains of other crayfish, crabs, echinoids, the small mollusc

Cantharidus eximus Perry, Mytilus planulatus Lamarck, Ischnochiton, and seaweed,

while Fielder (19642) has kept other Jasus novachollandiae in captivity on a supply

of Katelysia scalarina (cockles) and Modiolus sp. (mussels), supplemented by

pieces of sharks, bony fishes, and squids. The presence of fragmented molluscan

shells, crustaceans, echinoids, Bryozoa, and algae in the stomach contents was

subsequently reported by Fielder (1965), who concluded that, as dead and not

living Crustacea were preferred by experimental animals, a predilection is

shown for scavenging. He also established that they are normally nocturnal

with a peak period of feeding and locomotion at dusk, and that olfaction is

38 ANNALS OF THE SOUTH AFRICAN MUSEUM

probably of greater significance than vision in detecting food. The majority of

the Cape rock lobsters examined had been captured in baited traps, and the

cardiac fore-gut was almost empty or contained unrecognizable particles.

However, in young specimens collected in a rock pool at Liideritz, South West

Africa, and having a cephalothoracic length of from 30 to 40 mm, the cardiac

fore-gut was fully distended by a mixture of sand grains and semi-digested food,

comprising fragments of echinoid spines, sphaeromid isopods, amphipods,

acephalous dipterous larvae measuring about 6 mm long, the hard head-

capsules of other insect larvae, pieces of lamellibranch shells, and the intact

shells of a minute gasteropod resembling Eatoniella nigra (Krauss).

Preliminary investigations as to the attractiveness of food offered to two

medium-sized males kept in the laboratory were not very convincing. Although

the animals had been starved for some time, they could not be induced to feed

readily on portions of stockfish (Merluccius capensis). When, however, a variety

of living marine molluscs, such as Stphonaria capensis, small Patella granularis,

Oxystele variegata, small Aulacomya magellanica (Chemn.) = (Mytilus crenatus Lam.),

and the seaweeds Ecklonia and Ulva were provided, more interest was displayed.

One male showed an immediate preference for Ecklonia which was nibbled with

apparent relish, a fact that suggests a partial retention of the vegetarian diet

of the post-puerulus stage mentioned by Gilchrist (1920). Both specimens

sought out and lifted individual Patella or Aulacomya to the mouth, using mainly

the dactylopodites of the first pereiopods to insert the mollusc between the

third maxillipeds. In all these observed attempts at feeding, the molluscs were

dropped after a short period but, on leaving the tank in darkness overnight, it

was apparent on the following morning that a substantial quantity of Ecklonia

had been eaten, and scattered over the bottom of the tank were empty shells

of Patella and Aulacomya; some of the latter had been broken up, but the

Stphonaria, Oxystele, and Ulva were untouched. Subsequent observations of a

number of experimental animals at the Sea Point Aquarium indicated that

molluscs and Ecklonia were preferred to pieces of fish. On several occasions,

some of the rock lobsters were seen feeding at night on small mussels which

were grasped by the dactylopodites of the first pereiopods and so manipulated

that the posterior end and dorsal surface of the mollusc shell were turned towards

the rock lobster’s mouth. While usually supported in this position by the third

pereiopods, the dactylopodites of the first pereiopods were inserted between the

lower edges of the shell valves of the mussel and the two valves were pulled

apart, sometimes with the assistance of the dactylopodites of the second pereio-

pods. The latter were also used to loosen and remove parts of the posterior

adductor muscle and the mantle of the prey and convey them to the third

maxillipeds and the mouth.

These observations are by no means conclusive, but they seem to show that

J. lalandit resorts to scavenging when there is insufficient live food. They also

suggest that its principal food is seaweed, living molluscs, and perhaps other

marine animals that will provide protein and some of the calcium required for

THE ANATOMY OF THE CAPE ROCK LOBSTER 39

impregnation of the exoskeleton. Drach’s (1939) researches have proved,

however, that this source of calcium is of minor importance. He has also

determined that calcium reserves in the digestive gland are equally insufficient

to meet all requirements, but absorption of calcium from the sea water, probably

through the gills, is apparently essential to complete calcification of the

exoskeleton.

At the Sea Point Aquarium, where rock lobsters are fed regularly each

afternoon on pieces of fresh stockfish introduced into the large exhibition tank,

the following observations were made before and during feeding. Some of the

animals were ensconced in niches and crannies in the background of rocks, but

the majority were resting or walking about on the bottom, usually supporting

themselves on the last three pairs of pereiopods. Many were seen to be cleaning

the antennulary flagella by drawing them through the apposed medial edges of

the two third maxillipeds, and in some instances the dactylopodites of either

the right or the left second pereiopod or frequently the dactylopodites of the

fourth pereiopods were used to scrape the antennal peduncles, the eyes, and the

dorsal and lateral surfaces of the head. Occasionally, the second to the fourth

pereiopods were extended and their dactylopodites were drawn as far as

possible along the ipsilateral antennal flagellum. In both sexes the dactylopo-

dites of the fifth pereiopods were used to groom the surfaces of the abdomen,

the tail-fan, and the pleopods.

The animals appeared to be on the alert and to anticipate the approach

of feeding time for, immediately the pieces of fish were thrown into the tank

from above, there was a general stampede in the direction of the descending

lumps of food, the animals darting swiftly upward and seizing a portion

between the dactylopodites of the paired first and second pereiopods. After

having grasped the food, collision with other individuals was skilfully avoided

by using the escape tail-fan mechanism to move rapidly backward and eventu-

ally settle either on the rocks or on the bottom to ingest the juicy morsels. The

food was held in place against the mouth-parts usually by the dactylopodites

of both pairs of first and second pereiopods, but sometimes only the first

pereiopods and one or other of the second pair were used. While ingestion was

in progress, many of the animals walked about on the bottom supported by the

last three pairs of pereiopods and, as some approached the glass front of the

tank, further observations were possible.

Gilchrist’s (1913a) statement that the phyllosoma larvae employ the first

and second pereiopods to capture floating food particles and convey them to

the mouth is of interest, but in the adult the application of the anterior pereio-

pods and the third maxillipeds to the mouth during feeding tends to obscure

the further sequence of events in the oral region. It is thus hardly possible to

determine the part played by the first maxillipeds and the maxillae, but this

difficulty has also been experienced by previous investigators who have

attempted to discover the precise function of the mouth-parts in other Deca-

poda. From the present observations of the behaviour of adult specimens and

40 ANNALS OF THE SOUTH AFRICAN MUSEUM

the structure of their appendages it may be assumed, however, that the food

is inserted between the mouth-parts by the dactylopodites of the first pereiopods

and is held firmly in position by the mandibles. It was often noticed that, when

a large piece of food had been seized and was gripped by the mandibles, the

anterior pereiopods and the third maxillipeds would tug at it repeatedly, as

though attempting to tear it apart. At the same time, the endopodites of the

second maxillipeds were moved transversely across the outer surface of the

portion of food in what seemed to be a kind of sawing action that would cut

into the food. The spinous and setose medial margins of all the maxillipeds and

the endites of the first maxillae seem able to retain the food and, perhaps by

friction, may help to break it up. While this is taking place, the food will be

forced gradually between the mandibles, no doubt assisted by the thrusting

action of the inner endites of the first maxillae, but actual tearing of the food

by the mandibles is doubtful. The labrum and the metastoma and its paragnaths

are capable of various movements and appear to be complementary to the

mouth-parts and the mandibular palps in holding the food between the bluntly-

tuberculated mandibles while it is being crushed prior to its passage into the

oesophagus. Dissections indicate that the labrum is furnished with a complicated

musculature, comprising what appear to be constrictor, levator, abductor, and

adductor muscles, while each paragnath has an abductor and an adductor

muscle and the metastoma a pair of probable abductors. Moreover, examination

of sections of the puerulus stage and dissections of the adult reveal that there is

a pair of relatively large, compact glands between the bases of the first maxillae

and the paragnaths; the parts bordering the mouth are also liberally supplied

with glands, the secretion from which probably facilitates the process of

ingestion. .

Somewhat similar conclusions regarding the possible method of feeding in

other decapod Crustacea were reached by Borradaile (1916, 1917, 1922) and

by Yonge (1924), but in the animals examined by these authors actual seizure

of the food is usually performed by the chelipeds. Borradaile (1916) has also

remarked that in Palaemon serratus the second and not the third maxillipeds are

the most important organs for grasping the food and directing it forward to the

first maxillae and the mandibles and, if the piece of food is large, the incisor

processes of the mandibles will bite into it and reduce it.

In captive Fasus the process of ingestion was completed in five minutes or

longer, the time required depending on the size of the piece of food. It was then

observed that the exopodites of the three pairs of maxillipeds became very

active and were flicked to and fro across the mouth region, as if they were

cleaning the surface. Simultaneously, vigorous movements of the scaphogna-

thites seemed to take place, creating a strong forward current of water which

apparently served to flush the parts.

THE ANATOMY OF THE CAPE ROCK LOBSTER AT

INTERNAL ANATOMY

A. Bopy Cavity

One of the diagnostic features of the Arthropoda is the expansion of the

primary body cavity or haemocoel to form the perivisceral cavity and the

great reduction of the secondary body cavity or coelom. The arthropod coelom

arises as Cavities in some but not necessarily all of the mesodermal somites of

the embryo, and variations in the number and the segmental position of the

spaces have been reported in crustacean embryos. For instance, it has been

established by Manton (1928) that coelomic spaces are developed in all the

somites of Hemimysis except the antennulary, the mandibular, and the first

maxillary somites, and that, although those originally formed in the pre-

antennulary somites become obliterated, secondary preantennulary cavities

persist in the adult. In Nebalia (Manton, 1934) there are no coelomic spaces

in the anterior trunk somites, and the preantennulary spaces make a brief

appearance in the late embryo. It has also been shown that in both these

Crustacea the end sacs of the adult antennal glands are derived from the

cavities in the antennal somites, and that the coelomic spaces in other somites

disappear towards the end of embryonic development. Embryonic coelomic

cavities have also been described by Nair (1949) in the preantennulary, the

antennulary, the antennal, and the trunk somites of Caridina, while Waterman

& Chace (1960) have mentioned that Shiino (1950) has ascertained that in

Panulirus japonicus they are only evident in the antennal segment.

In conjunction with the suppression of the coelomic cavities in arthropod

embryos, the blastocoelic spaces between the primary germ layers expand and

become filled with haemolymph. The resultant cavity, termed the haemocoel by

Lankester (1900), consists of irregular perivisceral venous sinuses which

constitute an intrinsic part of the blood vascular system. The haemocoel is not

merely a blood-filled cavity, but variations in its internal pressures may also

assist in movements of the body and its appendages. In most Decapoda, how-

ever, the hard exoskeleton prevents marked changes in shape, but Manton

(1965) has shown that hydrostatic pressures within the haemocoel can be

demonstrated in some arthropods. By using weighted bridges and recording

the maximum loads raised by certain burrowing annelids and the chilopod

Orya barbarica (Gervais), she has noted significant differences in the pushing

powers of the two types of animals, and has found that the pressure responses

of the chilopod are greater than those of the annelids. She has concluded that,

while hydraulic effects are still evident in some arthropods, the haemocoel as a

hydrostatic mechanism has become less important in the larger and more

advanced members of the phylum in which rapid movements result mainly

from the action of sets of antagonistic muscles.

B. ENDOPHRAGMAL SKELETON (Figs 2, 3, 7)

A distinctive feature of many Reptantia is the presence in the thorax of an

elaborate internal framework, the endophragmal skeleton (endoskeleton),

42 ANNALS OF THE SOUTH AFRICAN MUSEUM

which not only protects and supports the viscera, but also provides attachment

for the thoracic muscles and greater structural stability for the movements of

the appendages. The component parts of the arthropod endoskeleton have

been carefully studied by Manton (1928, 1934, 1964), who has disclosed that

it is a combination of cuticular apodemal invaginations and transverse segmen-

tal tendons; the latter are particularly evident in the head region, but also

occur in the trunk of some species.

The parts of the endophragmal skeleton of the adult may be studied

easily in preparations made as follows: after excising the abdomen, the cara-

pace, and the appendages, the viscera and especially as many of the muscles as

possible should be removed without damaging the endoskeleton; the specimen

should then be boiled gently in a 10% solution of NaOH or KOH until clean

and, after thorough washing in water, it may be preserved in 70% alcohol.

Pilgrim & Wiersma (1963) also advocate the use of the stain, alizarin red S, as

a means of determining calcified and uncalcified areas and the presence of

certain epimeral hinges.

epimeron

er eli) Oe [ees dorsal articulation of coxopodite

ant. endopleurite process

pleural muscle chamber

mesophragm

articular condyle

position of -

pleurobranch

setiferous

process

endosternites

sternal muscle chamber

Paraphragm ventral articulations of coxopodites

Fic. 7. Side view of thoracic epimera, sterna, and endophragmal skeleton.

As there are few available accounts of the adult endophragmal skeleton of

other Decapoda, the terminology used for the structures observed in 7. lalandiu

is based largely on the descriptions given by Huxley (1881) and Pearson (1908)

for Astacus and Cancer respectively. Being associated with the broad sternal

region, the endophragmal skeleton of 7. lalandii is well developed and contri-

butes to the general rigidity of the cephalothorax. Fundamentally, as in other

Decapoda, it consists of a series of double sternal and epimeral infoldings from

the walls of adjoining segments, termed respectively the endosternites and endo-

THE ANATOMY OF THE CAPE ROCK LOBSTER 43

pleurites. These are inclined on each side of the body and combine to form the

endoskeleton and, in addition, each endopleurite has a vertical process which

unites with the corresponding endosternite to form an intersegmental partition

or arthrophragm (figs 2, 7) between the bases of two successive appendages.

The endosternites (figs 2, 3, 7) are paired, flat, vertical plates jutting upward

from the grooves between the sterna. The last of the series, projecting from the

junction of the thorax and the abdomen, are more horizontal and partly

resemble the ‘sella turcica’ of the brachyuran endoskeleton mentioned by

Pearson (1908) and Drach (1939). In most segments the dorsal edge of each

endosternite (fig. 3) is comparable tothe paraphragm of Astacus, which Huxley

(1881) described as a transverse projection of the head of a narrow, pillar-like

endosternite. Beginning between the second and third segments, paired hori-

zontal, somewhat cruciform pieces, the mesophragms (figs 3, 7) are differentiated

at the dorso-medial ends of the endosternites; and, as the jagged borders of the

two mesophragms of a pair usually interlock and are united by fibrous tissue

not only with each other in the mid-line, but also anteriorly and posteriorly

with the similar processes of adjacent segments, a more or less continuous

series of flat, calcified plates results. These arch over the sterna and form part of

the roof of a relatively shallow, mid-ventral sternal canal (figs 3, 31), through

which pass the ventral nerve cord and the subneural artery. Typical meso-

phragms seem to be lacking in the first two thoracic segments, but it is possible

that they may be represented by the fimbriated inner ends of the fused first and

second thoracic paraphragms. The first obvious pair of mesophragms on the

endosternites between the second and third segments are small and separated

from each other and also from the stronger second pair, but the gaps between

the two pairs are bridged by the superficial ventral thoracic muscles. Projecting

upward from the middle of the eighth thoracic sternum and causing a marked

external depression there is a pair of short, slightly divergent, independent

sternal apodemes (fig. 3), which seem to have been developed for the attachment

of the superficial ventral thoraco-abdominal muscles. The upper extremity

of each sternal apodeme links up with the last mesophragm and the latter also

has a slender ligamentous connexion with the broad posterior endosternite in

the eighth segment.

Each endopleurite (figs 2, 3, 7) arises at the junction of two successive

thoracic epimera and, projecting inward, it commonly bifurcates dorsally into

wide, sloping anterior and posterior processes. The anterior process of any one

endopleurite lies in the caudal half of a segment, while the posterior process of

the endopleurite in front extends into the rostral part of the same segment, and

both processes meet at the paraphragm and interlock with the endosternite.

In each segment, as in Cancer (Pearson, 1908), the linkage of the endopleurite

processes with the endosternite results in the separation of an upper Pleural

muscle chamber from a wider, lower sternal muscle chamber (figs 2, 7), in both of

which the large muscles of the basal segments of the appendages are lodged and

find attachment.

44. ANNALS OF THE SOUTH AFRICAN MUSEUM

The endosternites and endopleurites of the first two thoracic segments are

somewhat ill defined, but arthrophragms (fig. 3) are present for the attachment

of the arthrodial membranes of the appendages. Behind the second arthro-

phragm there is a narrow process, presumably an endosternite from the second

thoracic sternum (fig. 3), which meets the anterior process of the third endo-

pleurite. The third endopleurite, which is a fairly prominent vertical strut

behind the mandible approximately level with the anterior limit of the branchial

chamber, apparently corresponds to the lamina in Pilgrim & Wiersma’s (1963)

description of this region in Procambarus. It divides into customary anterior and

posterior processes, but the former passes medially to join the first obvious

mesophragm and virtually serves as a paraphragm between the second and

third segments. In addition, the endopleurite produces a conspicuous antero-

dorsal process (fig. 3), which may be analogous to the so-called fused first and

second thoracic paraphragms of other Decapoda. It passes obliquely forward and

inward to meet its fellow of the other side in the mid-line at the

anterior extremity of the endophragmal skeleton.

The latter, generally called the ‘cephalic apodeme’ (figs 3, 8, 11, 13, 19),

really consists of a pair of processes with interlocking medial margins, the

conjoined pieces forming a raised, transverse bridge which supports the

posterior region of the head and serves as a crutch for the hinder end of the

fore-gut. It lies behind the mandibles and is slightly antero-dorsal to the fused

sterna of the two last cephalic segments, of which, according to Huxley (1881),

it represents the mesophragms. It is an important centre for the attachment of

a number of anterior muscles and is itself firmly secured on each side to the

base of the lateral apodeme of the epistoma by the short, strong ventral cephalic

muscle (fig. 8).

The interpretation of structures bordering on the cephalic apodeme is

rather uncertain and somewhat arbitrary, but some of them may be likened to

the more typical parts of the endophragmal skeleton. The cephalic apodeme is

elevated above the sternal region by short, lateral supports which may be

considered as endosternites of the last two cephalic segments, and the arch

so formed encloses the suboesophageal ganglion. Confluent with the side walls

of the arch and extending to the epimera of the last two head segments, is a

grooved, double bar, which has generally been thought to represent the fused

paraphragms of these segments (figs 3, 4). To it, however, the posterior arthrodial

membrane of the first maxilla and the anterior membrane of the second maxilla

are attached, so that at least one arthrophragm also seems to be involved in

this structure. Projecting antero-laterally beneath the cephalic apodeme and

passing into the cavity of the mandible there is an obvious palmate process

which carries the mandibular anterior adductor muscle. It has been shown by

Manton (1928, 1934, 1964) and Snodgrass (1938, 1950) that in many arthro-

pods the mandibular adductor muscles are attached to a transverse inter-

mandibular tendon and that this resembles the endosternite which supports

the ventral muscles of the prosomatic appendages of Limulus. The paired

THE ANATOMY OF THE CAPE ROCK LOBSTER 45

structure in 7. /alandit appears to be analogous to the tendon of the mandibular

adductor muscle of other arthropods, but the median bar connecting the two

sides is no longer evident. Manton’s (1964) term, transverse mandibular tendon,

has, however, been applied to it (figs 3, 19), although there is no such tendon in

Astacus (Schmidt, 1915; Manton, 1964).

The only other endoskeletal structures of importance in the head region

are two procephalic processes (figs 3, 8) to which the anterior gastric muscles are

attached. Each process is a small, backwardly-directed plate located postero-

laterally on the dorsal surface of an infolding of the exoskeleton which passes

from the base of the rostrum over the ocular peduncle and forms an internal

shelf at the anterior extremity of the head.

C. MuscuLar SysTEM

The muscles of freshly killed specimens are too flaccid for satisfactory

investigation, but in material treated with 5°% formalin or in preparations

fixed in Zenker’s fluid and transferred to 70% alcohol, as recommended by

Schmidt (1915), the individual components are more easily analysed.

The whole system, which is conveniently divisible into two parts, the trunk

musculature and the muscles of the appendages, is broadly similar to that of

Astacus astacus (L.) and Pandalus danae Stimpson, described respectively by

Schmidt (1915) and Berkeley (1928). As might be expected, the complex

abdominal muscles closely resemble those of Jasus (Palinurus) edwardsi (Hutton)

investigated by Parker & Rich (1893), but they are also comparable with those

of certain other Malacostraca studied by Daniel (1931, 1933) and with those

of Panulirus polyphagus (Herbst) examined by George, Reuben & Muthe (1955).

Some reference is made to Cochran’s (1935) observations of the myology of

the blue crab, Callinectes sapidus Rathbun, and to a new terminology proposed

by Pilgrim & Wiersma (1963) for some of the muscles of Procambarus clarki

(Girard). For purposes of comparison between the different species, the

nomenclature used in the following account has been based mainly on the

observations of Schmidt and Daniel but, wherever possible, the names of the

individual muscles have been simplified.

I. TRUNK MUSCULATURE

The body muscles form a complex system of dorsal, ventral, and lateral

bundles, many of which are branched and intricately intertwined. They

occupy the greater part of the body cavity, the large muscles of the cephalo-

thorax showing few traces of segmentation and participating mainly in move-

ments of the abdomen, while the abdominal muscles are proportionally more

powerful and are arranged on a segmentally-repeated plan.

(a) Cephalothoracic muscles

Instead of dividing these into the different categories recognized by

Schmidt (1915), they are described more or less in order as seen in progressive

46 ANNALS OF THE SOUTH AFRICAN MUSEUM

antennal depressor

median apodeme of epistoma

labrure procephalic process

mandible. anterior gastric

paragnath dnterior dorso-ventral

antennal promotor

ventral cephalic

5 ri =

cephalic apodeme posterior dorso-ventral

epimeral attractor

lateral. thoraco-abdominal

anterior thoracic (medial)

Yj A\\\ W//; 4

YW ZA a |

eA WW centinaliny

anterior thoracic (lateral A x

thoracic superficial ventral deeper thoraco-qbdominal

transverse 1 ae

superficial dorsal thoraco-abdom.

superficial ventral thoraco-abdominal

abdominal superficial extensors

posterior oblique 1 (inner slip)

anterior oblique 1

intersternal membrane” 3 \\

P Et \ abdominal deeper extensors

abdominal superficial ventrals NE

intertergal membrane

transverse 6

anterior obli 6

nn Haque dorsal rotator uropodos

ventral rotator uropodos

ant. & post. flexors of telson

Fic. 8. Medial view of main muscles of right half of body.

dissections from the dorsal to the ventral surface in one half of the bilaterally

symmetrical animal.

Epimeral attractor muscle (Figs 8-10, 13, 43, 53)

This name was used by Schmidt (1915) to define a band of short vertical

fibres which connect the exoskeleton with the endoskeleton. The muscle band

extends from the posterior limit of the branchio-cardiac groove to the antero-

THE ANATOMY OF THE CAPE ROCK LOBSTER 47

lateral end of the cervical groove, where it terminates approximately at the

level of the anterior mandibular apodeme. All the fibres are attached to the

carapace and are inserted on the inner, dorsal margin of the epimeral plates

opposite the upper limit of the lining of the branchiostegite. The whole strip

is clearly divisible into an outer or lateral series of short fibres and an inner row

of somewhat longer, more medial fibres and, as the latter is interrupted at the

level of the transverse part of the cervical groove, it is separable into an anterior

portion coinciding with the lateral region of the cervical groove and a posterior

part which is located beneath the branchio-cardiac groove.

These subdivisions are respectively comparable to the lateral, anterior,

and dorsal heads of the epimeral attractor muscle of Procambarus, in which

Pilgrim & Wiersma (1963) have also distinguished an antero-ventral, a pos-

terior, and a receptor head. There can be little doubt that the latter is also

present in Jasus, but no particular study was made of stretch receptors and

their associated muscles. The antero-ventral head does not seem to be differen-

tiated in 7. lalandii, and there is some resemblance between the posterior head

of the epimeral attractor muscle of Procambarus and one of the muscles, perhaps

the transverse muscle, herein assigned to the wall of the pericardial pouch

(p. 135).

It is also of interest to note that the short musculus contractor epimeralis, which

Schmidt (1915) defined in Astacus and reported in Homarus, was not observed

in Jasus. Alexandrowicz (1952) has also remarked that it is wanting in Palinurus

elephas (Fabr.), and Pilgrim & Wiersma (1963) have attributed its non-

existence in Panulirus interruptus to the absence of an uncalcified medial epimeral

hinge that occurs in forms possessing this muscle.

cervical groove gastric region of head

lateral thoraco-abdominal (medial)

epimeral attractor

heart

posterolateral suspensory.

ligament

deeper thoraco-abdominal

branchial membrane

pericardial pouc lateral thoraco-abdominal (lateral)

smooth half of

triangular sclerite abdominal} tergum 1

flange

articular condyle

squamous half of

abdominal tergum 1

Fic. g. Dorsal view of posterior half of cephalothorax after removal of branchiostegites and

cardiac region of carapace.

48 ANNALS OF THE SOUTH AFRICAN MUSEUM

Lateral thoraco-abdominal (Figs 8-10, 12, 45, 53)

Apparently so called by Schmidt (1915) because of its lateral insertion,

this is the most superficial of the longitudinal muscles in the thorax and com-

prises medial and lateral portions. Its main purpose is probably to assist in

straightening the abdomen, but independent unilateral contraction may also

cause a sideways movement.

The medial part is the longer and stronger of the two and is a thick bundle

with a marked transverse inscription; flanking the heart, it originates on the

carapace behind the cervical groove. It tapers towards its insertion on a small,

narrow sclerite antero-medial to a more conspicuous, triangular, calcified

sclerite (figs 9, 45) that lies behind the pericardial pouch in line with the

articular condyle for the carapace and fits into a dorso-lateral notch on the

anterior margin of the first abdominal segment.

The lateral part is a flat, more or less vertical, fan-shaped muscle in the

posterior region of the thorax. It is separable into two bundles, a narrower

dorsal element and a broader ventral portion, both of which are attached one

above the other on the epimeron of the penultimate segment behind the

epimeral attractor muscle. The two bundles pass through the pericardial

pouch below and lateral to the aforementioned medial part of the main

muscle and have a broad insertion on the anterior margin of the triangular

sclerite. By analogy with the insertions of the three heads of the similar muscle,

the abdominal abductor, of Procambarus, the triangular sclerite is obviously

comparable to one of the linking thoraco-abdominal sclerites, which col-

lectively have been designated as the ‘secula’ by Pilgrim & Wiersma (1963).

Superficial dorsal thoraco-abdominal (Figs 8, 10, 12)

Connecting the posterior region of the thorax with the first abdominal

segment is this flat, dorsal, double band, which resembles the first superficial

dorsal muscle of Astacus (Schmidt, 1915) and the thoraco-abdominal super-

ficial extensor muscle of Procambarus (Pilgrim & Wiersma, 1963). Its two parts

arise one behind the other on the epimera at the posterior limits of the sixth

and seventh thoracic segments, the posterior flap overlapping the anterior one

as they both spread out beneath the medial section of the lateral thoraco-

abdominal muscle and extend backward through the pericardial pouch to the

proximal rim of the first abdominal segment, where they have a broad, super-

ficial insertion.

Deeper thoraco-abdominal (Figs 8-10, 53)

Lying in the pericardial cavity and also uniting the thorax with the

abdomen, this more extensive and more ventral muscle is identical with the

medial and lateral musculi dorsales profundi thoraco-abdominales of Astacus

(Schmidt, 1915) and the three heads of the thoraco-abdominal deep extensor

muscle of Procambarus (Pilgrim & Wiersma, 1963). It shows possible traces of

segmentation in that it consists of three compact bundles that arise in sequence

on the epimera above the endopleurites at the posterior borders of the third,

THE ANATOMY OF THE CAPE ROCK LOBSTER 49

antennule antenna

rostrum

‘frontal tubercle

pedate process

anterior gastric muscle

proventriculus: ophthalmic artery

posterior gastric muscles:

posterior adductor of mandible

digestive gland right testis

antennary artery

lateral thoraco-abdom. muscle

heart

deeper thoraco-abdom. muscle

branchial membrane ]

dorsal abdominal artery

epimeral attractor muscle

branchiostegite

sup. dorsal thoraco-abdom. muscle

Superficial extensor abdom. seg, 1

deeper extensor abdom. seg. 1

20 mm,

ant. oblique (flexor).muscles

Superficial extensor abdom, seg. 5

remotors of uropod—_ aye

auxiliary muscle

telson uropod

Fic. 10. Dorsal view of small male; part of the cephalo-thoracic exoskeleton and the abdominal

terga have been removed.

50 ANNALS OF THE SOUTH AFRICAN MUSEUM

fourth, and fifth segments in line with the origins of the previous muscle.

Several inscriptions are evident on the first two bundles, each of which is

bipartite and has dorsal and antero-ventral attachments. The small dorsal

connexion of the anterior bundle is located near the anterior end of the branchio-

cardiac groove and marks the subdivision of the medial vertical fibres of the

epimeral attractor muscle into anterior and posterior sections. While the fibres

of the first bundle are slightly twisted, those of the other two bundles are

straighter, and it may also be noted that the branchio-pericardial orifices are

apparent immediately behind the attachments of the three bundles. All three

portions slant and expand towards the mid-line, the first and third underlying

the second as they insert dorsally on the proximal margin of the first abdominal

segment below the superficial dorsal thoraco-abdominal muscle. The latter

and the present muscle are aligned with the two layers of the dorsal abdominal

musculature to which they act as accessory extensors of the abdomen.

Anterior fascia

According to Berkeley (1928), this term may be applied to a tough coat

of fibrous tissue, which surrounds the cephalic apodeme and may be equated

with the two endophragmal compressor muscles distinguished in Astacus by

Schmidt (1915). It also envelops the medial parts of the fused paraphragms of

the fifth and sixth cephalic segments, particularly at their junction with the

sternal region. In addition, it secures the inner ends of the fused paraphragms

of the first and second thoracic segments to the upper surface of the cephalic

apodeme. To it are attached the medial part of the paired anterior thoracic

muscle, the posterior dorso-ventral muscle, and some of the muscles of the first

and second maxillae.

Anterior thoracic muscle (Figs 8, 11, 13, 53)

This is one of the largest and strongest muscles of the thorax and occupies

the ventral half of the body cavity between the deeper thoraco-abdominal

muscle and the endophragmal skeleton. It consists of a number of inter-

connected parts, which serve as powerful flexors and are effectively thoraco-

abdominal in nature. Unlike the similarly-termed system of Astacus (Schmidt,

1915) and the corresponding deep thoracic flexor muscles of Procambarus

(Pilgrim & Wiersma, 1963), it does not join the bulky first anterior oblique

muscle, but proceeds below this and the first (i.e. thoracic) transverse muscle

to insert broadly on the proximal margin of the medial sclerite of the first

abdominal sternum.

For convenience, the several components may be divided into narrower

medial and more complex lateral portions. The former, like the medial part of

the analogous muscle of Astacus and the first deep thoracic flexor muscle of

Procambarus, consists of two slips, the inner of which arises ventrally on the

anterior fascia below the cephalic apodeme, while the outer or more lateral

head is attached to the paraphragm between the second and third segments.

The lateral portion comprises a series of four bundles, most of which are

THE ANATOMY OF THE CAPE ROCK LOBSTER 51

cephalic apodeme

Gnterior thoracic (medial)

branchio-pericardial vessels

central 1

anterior thoracic (lateral) : : :

branchio-pericardial vessel

heads of Central 1 posterior oblique 1 (outer slip)

anterior oblique 1

dorso-latera} 1

1 i :

SRE} TOSS posterior oblique 2 (attachment)

SSEUERID RSA 20C1) oblique transverse 2

lateral abdominal 1 pr

quxifiary 1

transverse 2a

wu Og

f\ Seas promotor of pleopod 2

posterior oblique 5

transverse 4b (attachment)

oblique transverse 5

transverse 4a

central 5 (attachment)

central 5 (insertion)

\ ZZ Cc :

art of lateral remotor uropodos =

p P \ S=a

dorsal rotator uropodos : ea dorso-lateral 6

Fic. 11. Dorsal view of ventral trunk muscles.

marked by transverse inscriptions. The first bundle arises on the anterior

process of the third endopleurite, while the next two have broad attachments

on the frontal area of the epimeron of the third segment. The first bundle

passes below the foregoing medial section of the muscle, which is joined by an

antero-dorsal slip extending back from the second bundle. The fourth bundle

differs from the others in that it consists of two overlapping parts: one arises

antero-dorsally on the epimeron between the third and fourth segments,

below the attachment of the anterior bundle of the deeper thoraco-abdominal

muscle and in front of the upper end of the anterior branchio-pericardial

52 ANNALS OF THE SOUTH AFRICAN MUSEUM

vessel; the origin of the second part of the fourth bundle is more ventral and

occurs on the endopleurite and the paraphragm between the third and fourth

segments.

Posterior to the lateral constituents of the anterior thoracic muscle are two

additional muscles, attaching respectively between the fourth and fifth and the

fifth and sixth segments immediately below the middle and the posterior

bundles of the deeper thoraco-abdominal muscle. Each has two heads, one

originating dorsally on the epimeral ridge and the other on the endopleurite

of the corresponding segment, and the dorsal heads occur at the anterior

boundaries of the middle and the posterior branchio-pericardial vessels (fig.

11). These two elements seem to be lacking in Astacus, but Pilgrim & Wiersma

(1963) have described an innominate muscle in Procambarus which appears to

correspond with one of these. They converge towards the mid-line and crossing

them posteriorly is a dorsal, transverse inscription, behind which they unite

to form a cylindrical cord. The latter, by analogy with the arrangement of

the abdominal musculature, may be assumed to represent the first central

muscle, because it traverses and supports the first abdominal anterior oblique

muscle; for this reason, the two muscles in question have been identified as the

heads of central muscle 1 (figs 11, 13). A further complication in this region is

that, attached to a ventral inscription on the anterior head of the first central

muscle, there are two broad, flat slips which together may be regarded as

forming the first posterior oblique muscle.

Anterior dorso-ventral muscle (Fig. 8)

Arising antero-laterally on the cephalic apodeme, this narrow and rather

weak unit passes outward and slightly obliquely upward in front of the mandibu-

lar posterior adductor muscle. It is inserted by a long, flat tendon on the body

wall medial to the large promotor muscle of the antenna.

Posterior dorso-ventral muscle (Fig. 8)

The course of this rather inconspicuous muscle is more horizontal than

strictly dorso-ventral. It arises as a long, narrow, fibrous band laterally on the

anterior fascia and, travelling dorsally over the muscles of the second maxilla,

its few short fibres are inserted on the epimeron near the junction of the bran-

chial and the prebranchial chambers and below the anterior end of the epimeral

attractor muscle.

The function of these two muscles is obscure, but Berkeley (1928) has

suggested that the two anterior and one posterior dorso-ventral muscles that

occur in Pandalus danae probably strengthen the anterior fascia, while the

anterior ones may also protect the viscera from compression by the large

antennal muscles.

Ventral cephalic muscle (Fig. 8)

This is a tough, more or less tendinous strip, which arises on an antero-

lateral process of the cephalic apodeme and is directed forward dorsally over

THE ANATOMY OF THE CAPE ROCK LOBSTER 53

the anterior apodeme of the mandible to an insertion on the posterior edge of

the lateral apodeme of the epistoma close to the attachment of the depressor

muscles of the antenna. As it is short and strong and fastens the cephalic

apodeme to the epistoma, it probably provides some support for the anterior

extremity of the endophragmal skeleton.

Thoracic superficial ventral muscles (Figs 8, 13)

Of the six pairs of these narrow, mid-ventral bands, the first four are

clearly defined, but the last two pairs are weakly developed. The first pair

bridges the gap between the anterior fascia and the mesophragms in the third

thoracic segment and each of the other pairs is attached to the posterior border

of the mesophragm of one segment and inserted on the anterior part of the

next successive paired mesophragm. The attachments of the two muscles of a

pair are usually fairly wide apart, but the muscles tend to spread out and the

inner fibres slope medially towards each other and are adjacent at their

insertions.

Like certain other small muscles, their usefulness is uncertain, but their

better development in the immediate postcephalic region, where the meso-

phragms are not firmly united, indicates that they may help to sustain this part

of the body or perhaps participate in any slight movements, while their rudi-

mentary condition above the heavily-calcified posterior mesophragms may be

correlated with the greater rigidity of the corresponding segments. Schmidt

(1915) has also suggested that in Astacus they may be of some significance during

ecdysis, but has offered no explanation of this supposition.

Superficial ventral thoraco-abdominal muscle (Figs 8, 13)

Generally considered as a continuation of the superficial ventral muscles

of the thorax, this stouter pair of adjacent muscles is attached to the vertical

sternal apodeme in the last thoracic segment and fills the posterior mid-ventral

depression of this region. Although each muscle consists of fairly straight medial

and more oblique lateral fibres, these are not identical with the parts dis-

tinguished in Astacus by Schmidt (1915) and in Procambarus by Pilgrim &

Wiersma (1963). Instead of being divisible into one muscle inserted posteriorly

on the first abdominal sternum and another having an insertion on the inter-

sternal membrane between the thorax and abdomen, all the fibres are inserted

on the medial sclerite of the first abdominal sternum below the insertion of the

anterior thoracic muscle. This arrangement appears to provide for greater

freedom of movement of the ventral thoraco-abdominal junction than would

eventuate if these muscles were inserted directly on the proximal rim of the

broad calcified first abdominal sternum immediately in front of the attach-

ments of the second anterior oblique and some of the fibres of the third anterior

oblique.

Apical muscles (Figs 60, 61)

In addition to the foregoing musculature, there is a pair of short, broad,

anterior muscles, the omission of which by Schmidt (1915) seems to have

54 ANNALS OF THE SOUTH AFRICAN MUSEUM

resulted in some misconceptions regarding the homologies of certain muscles

associated with the middle region of the fused eyestalks. The muscles in question

were first briefly mentioned as the musculi compressores annuli by Baumann

(1921) in his account of the circulatory system of Astacus. This term has been

retained by Elofsson (1964), while Hanstrém (1947) referred to them as apical

muscles innervated by the apical nerves, and his nomenclature seems appro-

priate for descriptive purposes. The eye muscles of Fasus (Palinurus) edwardsit

studied by Parker & Rich (1893) are probably essentially similar to those of

Ff. lalandii and, although their terminology is obsolete, it is likely that their

levator of the basal sclerite is analogous to the apical muscle of F. lalandii.

The two flat apical muscles are located frontally in the middle cylinder

of the fused eyestalks, and can only be clearly seen when the cephalic part of

the nervous system has been exposed (fig. 61). They extend from the mid-

dorsal surface outward and downward towards the junction of the eyestalk

with the body near the ventral base of the pedate process (fig. 60): as Bau-

mann’s term suggests, they probably function as compressors of the eyestalk

cylinder.

(b) Abdominal muscles

Movements of the abdomen are effected by powerful longitudinal muscles

that are distinctly arranged into dorsal and ventral groups in each segment.

The dorsal muscles, which lie between the terga and the intestine, are respon-

sible for extending and straightening the abdomen, while contraction of the

larger ventral muscles results in flexure of the segments.

(1) Dorsal abdominal muscles

The abdominal extensors are distinguished as two layers of paired muscles,

which form an almost continuous series down the length of the abdomen.

Herein, and also in Pilgrim & Wiersma’s (1963) article, they are described as

the superficial and deeper extensor muscles and correspond respectively to

the musculi dorsales superficiales and the musculi dorsales profundi abdominis

of Astacus (Schmidt, 1915). Situated above the anterior ends of the superficial

extensors is another pair of rather inconspicuous bundles, which have been

called the dorsal arthrodial muscles.

Dorsal arthrodial muscle (Fig. 12)

In describing the muscle receptor organs of Homarus, Alexandrowicz

(1951) drew attention to the presence of paired, small, medio-dorsal muscles

connected with the intertergal membranes, and his observations have been

confirmed in Procambarus and Astacus by Pilgrim & Wiersma (1963), who have

termed them the dorsal membrane muscles. In Jasus similar delicate muscle

fibres form two fan-shaped elements in the first to the fifth segments immedi-

ately dorsal to the superficial extensors. Each is attached in the middle of the

tergum of one segment and is inserted anteriorly on the next dorsal arthrodial

THE ANATOMY OF THE CAPE ROCK LOBSTER 55

membrane behind. Although weakly developed, they doubtless assist in move-

ments of the intersegmental arthrodial membranes during extension and

flexion of the abdomen.

deeper extensors | Superficial dorsal thoraco-abdominal

| {lateral thoraco-abdominal

Superficial extensor 1 x }

dorsal arthrodial

lateral abdominal 1

20 mm.

Superficial extensor 2

lateral abdominal 3

SN, WIN 7

ils | | \ . lateral abdominal 2

ies.

(=; Promotor of pleopod 1

EN)

eZ Vie

al sal ~ anterior oblique

deeper extensor 3 —=—— SWE]

duxiliary 3

central 4 & 5 etc.

deeper extensor 4

Fic. 12. Dorsal view of anterior part of abdomen, showing the dorsal musculature.

In their investigation of the thoraco-abdominal junction of Procambarus,

Pilgrim & Wiersma (1963) have described certain other dorsal and lateral

membrane muscles, but these appear to be similar to the muscles herein

interpreted as intrinsic muscles of the pericardial pouches (p. 135-6).

Superficial extensors (Figs 8, 10, 12, 31, 54)

Mid-dorsally below the terga of the first five abdominal segments there

are paired, strap-shaped muscles, each of which consists of medial and lateral

bundles of almost straight fibres. Although they are uniformly arranged, they

are not directly continuous, for each muscle originates near the anterior edge

of the tergum and is inserted posteriorly on the next intertergal membrane, so

that there is a slight gap between the insertion of one muscle and the attach-

ment of the next one behind. As in Procambarus (Pilgrim & Wiersma, 1963), in

most segments the lateral division is attached on an oblique tergal ridge

postero-lateral to the level of the attachment of the medial portion.

The superficial extensors of the first abdominal segment arise immediately

behind the insertions of the superficial dorsal thoraco-abdominal muscles, but

the two of the pair are more widely separated than usual and do not adjoin in

56 ANNALS OF THE SOUTH AFRICAN MUSEUM

the mid-dorsal line. Furthermore, the lateral part of the superficial extensor

of this segment is subdivided into two sections which tend to embrace the

attachment of the axial column of ventral muscles, its narrower outer strip

originating laterally on the first abdominal segment immediately posterior to

the calcified triangular sclerite that supports the lateral thoraco-abdominal

muscle.

In the sixth segment the superficial extensors are weakly developed and seem

to be reduced to a few relatively short, medial fibres which are attached

obliquely on the tergum and pass back beneath the medial remotor muscle of

the uropod.

Deeper extensors (Figs 8, 12, 31, 54)

Being much thicker than the superficial extensors, this series almost fills

the mid-dorsal part of the haemocoel above the intestine. Each muscle consists

of closely-approximated medial and lateral parts and the consecutive units

are practically continuous down the length of the abdomen, being attached

anteriorly in one segment and inserted on the proximal border of the next

segment behind. The medial part is composed of markedly oblique fibres which

are separated into two main bundles; posteriorly the innermost bundle tends

to overlap the outer bundle, but their insertions seem to be less complex

than those observed in Procambarus by Pilgrim & Wiersma (1963). The lateral

part consists of straight, longitudinal fibres and comprises several bundles,

which are slightly superimposed on one another and so arranged that the

insertion of the inner slip is somewhat dorsal to the outer fibres of the medial

deeper extensor. Functionally they are similar to the superficial extensors and

may be regarded as a continuation of the deeper thoraco-abdominal system.

The last of the series, in the sixth segment, is narrower than usual, and is

inserted on the proximal margin of the telson, of which it acts as an extensor.

(ii) Ventral abdominal muscles

The large, longitudinal flexor muscles practically fill the space below the

intestine and are intricately arranged and intertwined to form thick, lateral,

rope-like cords which are interconnected segmentally by transverse muscles.

Daniel (1931, 1933), whose terminology has been applied to the component

parts in Zasus, has shown that, despite varying degrees of complexity, the dis-

position of the abdominal muscles in the major groups of Malacostraca can

be reduced to a basic plan. The main segmental constituent on each side is a

thick anterior oblique muscle that twists around certain axial bundles distin-

guished as the central and the oblique transverse muscles, both of which enter into

relationship with the major transverse muscle. A short, dorso-lateral auxiliary

muscle is connected with most of the anterior oblique muscles, and just behind

each of the latter is a narrow bundle, termed the dorso-lateral muscle. Additional

to these, there is a comparatively long, flat posterior oblique muscle, which is

usually attached on the tergum in front of the oblique transverse muscle, but

travels beneath it and the central muscle to a ventral insertion. In most seg-

THE ANATOMY OF THE CAPE ROCK LOBSTER 57

ments the attachments of all these muscles, except the anterior obliques, are

grouped together on the tergum and form a conspicuous, rounded, tuft-like

mass intercalated laterally between successive anterior obliques. The regular

pattern formed on the sterna (fig. 14.) by the attachments and insertions of the

anterior oblique muscles and the insertions of the posterior oblique muscles

suggests that concerted action is ensured down the length of the abdomen.

While each muscle is usually distinct, the plan becomes involved by occa-

sional linkage of neighbouring units, and it seems pointless to describe the

course of the individual muscles and their minor variations. Instead, a general

account is given of each set of muscles and, in addition to superficial views of

their arrangement (figs 8, 11), a grossly oversimplified scheme (fig. 13) has

been included in an attempt to present a clearer impression of the system as a

whole. In this plan the muscles represented are greatly attenuated and dis-

torted and some interconnexions have been omitted. It was devised while

endeavouring to compare the system of asus lalandi with Daniel’s (1931,

1933) more realistic, but rather abstruse, diagrams of the abdominal muscles

of other Malacostraca and, by coincidence, it is remarkably similar to figure 26

in Parker & Rich’s (1893) beautifully illustrated account of the muscles of

Jasus edwardsu, although this article was consulted after the present conclusions

had been reached. The descriptions given by these authors therefore strengthen

some of the following convictions regarding the composition of the ventral muscu-

lature and indicate that there is probably a uniform design in all species of Fasus.

Anterior oblique muscles (Figs 8, 10-13, 31, 54, 77, 78)

This group forms the principal flexors of the abdomen and comprises a

series of strong paired muscles, all of which, except the last two pairs, occupy

three successive segments. Typically each muscle arises ventro-laterally on or

just in front of the anterior margin of one segment, practically in line with the

lateral fibres of the superficial ventral muscles (fig. 14); it then arches dorsally

in the pleural region and passes transversely across the segment towards the

mid-line. After adjoining and sometimes, as in the last three segments, being

connected by an aponeurosis with the contralateral muscle, it continues

posteriorly as a broad ventral band and is inserted by tendinous material on the

posterior sternal ridge of the second segment behind that in which it originates.

Thus, for instance, anterior oblique muscle 4 (fig. 13) is attached near the

proximal border of the third segment, but winds through the next two segments

and has a broad insertion on the posterior bar of the fifth segment.

Compared with forms investigated by Schmidt (1915) and Daniel (1933),

one pair of anterior oblique muscles is lacking, so that the first of the series in

jasus is equivalent either to the second or to the combined first and second

anterior obliques. of those Eucarida that possess seven pairs of these muscles.

It bulges forward into the posterior region of the thorax as a conspicuous mass

which, although composed of two broad bundles with separate origins, may be

regarded as anterior oblique 1 (figs 8, 11, 13, 77). It differs from other anterior

ANNALS OF THE SOUTH AFRICAN MUSEUM

medial anterior thoracic cephalic apodeme

lateral anterior thoracic ST UCINGI Gi APEIee Sir

(lateral & medial fibres)

thoracic superficial ventral

central 1

endophragmal skeleton

sternum

anterior oblique 1

transverse 1

oblique transverse 1

dorso-lateral 1

posterior oblique 1

(inner slip)

oblique transverse 2

superficial ventral

stones Jy NY: central 2

thoraco-abdomina|! \ a & SS) EY ARS

transverse 2a anterior Oblique 2

transverse 2b

posterior oblique 2

abdominal Superficial ventralis

posterior oblique 5 central 6

: 1

\ p; anterior oblique 6

transverse 6 e/g ~4|

\ dorso-lateral 6

posterior oblique 6

ventral rotator uropodos

anal compressor dorsal rotator uropodos

anterior flexor telsonos

ae flexor telsonos

uropod aes f: i son

y y

Gnal dilatator

ventral flexor telsonos

{

Fic. 13. Medial view of scheme of main right ventral muscles.

THE ANATOMY OF THE CAPE ROCK LOBSTER 59

obliques in that its attachment is not essentially sternal; its anterior bundle is

connected ventrally with the first transverse muscle and the posterior bundle

mainly with an element identified as the first oblique transverse muscle, but

some of its posterior fibres have a ventro-lateral attachment on the anterior

margin of the first abdominal segment. The whole muscle curves dorsally over

the first central muscle towards the mid-line before travelling ventrally to an

insertion on the posterior sternal ridge of the second abdominal segment.

Anterior oblique muscle 3 has a normal attachment close to the anterior edge

of the second abdominal segment, but some of its strong inner fibres arise

proximally on the first abdominal sternum behind the attachment of the second

anterior oblique muscle. This deviation from the norm may compensate in

some measure for the absence of superficial ventral muscles in the first abdo-

minal segment.

Although bulky, anterior oblique muscles 5 and 6 are relatively the shortest

of the series and occupy two instead of the usual three segments. The former is

inserted near the anterior margin of the sixth sternum, while the latter passes

to the posterior sternal ridge of the same segment and its strong tendon is

continued outward as far as the medio-ventral edge of the protopodite of the

uropod.

Auxiliary muscles (Figs 11, 12, 77)

Antero-laterally in each abdominal segment, except the first, there is a

short, stout muscle which arises by a tough tendon on the posterior sternal rib

of the segment in front and near the origin of its corresponding anterior oblique

muscle; it passes obliquely upward and backward, spreading out to a dorsal

insertion on the tergum adjoining the attachments of the central muscles. The

last of the series is the largest and projects into the sixth segment where it

intervenes between the lateral and the medial remotor muscles of the uropod.

Daniel (1931, 1933) has suggested that these are subsidiary to the anterior

oblique muscles, and has also commented on the absence of auxiliary muscles

in the first abdominal segment of Homarus and Palinurus. Similar muscles

present in Jasus edwardsii were originally described by Parker & Rich (1893)

as oblique flexors.

Central muscles (Figs 8, 11-13, 77)

Arranged intersegmentally and constituting part of the scaffolding around

which the anterior oblique muscles twist, are curved dorso-lateral columns,

distinguished as the central muscles by Parker & Rich (1893) and Daniel

(1931, 1933). Although they form a regular series stretching from one segment

to the next and are mostly fastened dorso-laterally to the tergum, they are not

directly continuous, for the insertion of the posterior end of one muscle and the

anterior attachment of the next in sequence are separated from each other and

partly obscured by the attachments of the posterior oblique and the oblique

transverse muscles.

Central muscle 1 (figs 8, 11, 13) acts as a support for the first anterior oblique

60 ANNALS OF THE SOUTH AFRICAN MUSEUM

muscle and, as previously indicated (p. 52), is considered to arise by two heads

on the epimera approximately opposite the fifth and sixth thoracic segments,

a conclusion that is substantiated by the observations of Parker & Rich (1893)

and Daniel (1931, 1933). It is a somewhat twisted, double cord, the outer

bundle of which joins the posterior fibres of the first anterior oblique, whereas

the inner bundle is bridged to the second transverse muscle and is inserted

antero-laterally in the first abdominal segment close to the attachment of the

first dorso-lateral muscle.

Central muscle 2 is also bipartite at its origin in the first abdominal segment,

its outer fibres arising antero-laterally, while its stout inner bundle attaches

ventro-laterally behind the first central and the first dorso-lateral muscle.

Central muscle 6 (fig. 13) is a short, longitudinal column, practically confined

to the fifth abdominal segment and inserted ventro-laterally at the anterior

border of the sixth segment posterior to the insertions of the fifth anterior and

the fifth posterior obliques and in proximity to the last auxiliary muscle.

The central muscles of 7. lalandit may be compared to the lateral portions

of the inter-tergal abdominal muscles of Panulirus polyphagus as described by

George, Reuben & Muthe (1955), who have suggested that they assist the

dorsal extensor muscles in straightening the abdomen, and consequently they

and the major flexors (anterior obliques) relax and contract alternately. It is

also of interest that central muscles have not been differentiated by either

Schmidt (1915) or Berkeley (1928), but it seems likely that the longitudinal

lateral parts of the transverse muscles of Astacus and Pandalus are their functional

equivalents.

Transverse muscles (Figs 8, 11, 13, 54)

Daniel (1931, 1933) has recorded the presence of one thoracic and four

abdominal transverse muscles in Eucarida, including the decapods Homarus

and Palinurus. The arrangement in 7. lalandii is substantially similar, with the

possible addition of transverse muscles in the fifth and sixth segments, but in

this detail there is agreement with Astacus (Schmidt, 1915) and 7. edwards

(Parker & Rich, 1893), in which transverse muscles also occur in the posterior

segments.

Transverse muscle 1 (figs 8, 11, 13) is comparable to the thoracic transverse

muscle described by Parker & Rich, Schmidt, and Daniel; it is a wide band

that runs in the mid-line below the first central muscles and serves to connect

the anterior bundles of the first pair of anterior obliques. In some respects, it

is analogous to the minor transverse muscles in abdominal segments, especially

that in the first abdominal segment.

In each abdominal segment there are major (transverse a) muscles, and

in the first four segments additional minor (transverse b) muscles which

correspond with the dorsal and the ventral transverse muscles of Astacus

(Schmidt, 1915). The major transverse muscle may be described as an inter-

segmental bridge composed of strands from the right and left anterior oblique,

THE ANATOMY OF THE CAPE ROCK LOBSTER 61

the central, and the oblique transverse muscles of the segment in front. The

minor transverse muscles, on the other hand, are paired intrasegmental forma-

tions. With the exception of the first, each arises on the tergum (fig. 11) lateral

to the origins of the posterior oblique and the oblique transverse muscles; it

then bends inwardly below the posterior oblique and becomes thin and vertic-

ally flattened towards its mid-ventral insertion on the posterior face of the

major transverse muscle. The first minor transverse muscle (transverse 2 ),

fig. 13) stems from a broad inscription on the inner fibres of the second anterior

oblique muscle, but its upper fibres also adjoin the ventral part of the second

central muscle.

George, Reuben & Muthe (1955), although not recognizing discrete

transverse muscles, have indicated that each inter-tergal muscle of Panulirus

polyphagus has an inherent transverse portion which is responsible for the

compression of the segment. From this it may be inferred that the inter-tergal

muscles of Panulirus are homologous to the transverse muscles of Astacus

(Schmidt, 1915) and Pandalus (Berkeley, 1928), while the latter in turn are

evidently comparable to the combined transverse and central muscles defined

by Parker & Rich (1893) and Daniel (1931, 1933).

Oblique transverse muscles (Figs 11, 13)

This name was applied by Daniel (1931, 1933) to certain rather incon-

spicuous muscle slips that usually unite neighbouring anterior oblique and

central muscles in the anterior abdominal segments. In the present study these

connections are considered to be relatively unimportant, and the term has been

transferred to the elements described by Parker & Rich (1893) as oblique

extensors and by Daniel (1931, 1933) as the dorso-lateral muscles, because

each appears to be an oblique portion for the attachment of the major trans-

verse muscle. Each member of the series arises on the tergum near the anterior

head of the central muscle, and a small portion of it is visible dorsally adjacent

to the posterior oblique muscle. Towards the mid-line, however, it becomes

obscured as it bends below the central muscle and forms with it the saddle that

supports the anterior oblique muscle; subsequently it merges with the major

transverse muscle of the next segment.

A muscle, which may tentatively be identified as oblique transverse 1 (fig.

13), originates in the thorax at a ventral inscription on the posterior bundle of

the first anterior oblique; it curves medially beneath the first central muscle

to become confluent with the major transverse muscle in the first abdominal

segment.

Dorso-lateral muscles (Figs 11, 13)

Associated with the transverse muscles of the first three abdominal seg-

ments, Parker & Rich (1893) distinguished paired accessory oblique extensors.

These are homologous to the accessory dorso-lateral muscles described by

Daniel (1931) in Palinurus, and the similar muscles of 7. lalandii have simply

been called the dorso-laterals.

62 ANNALS OF THE SOUTH AFRICAN MUSEUM

On the whole, they are rather weakly-developed bundles that run parallel

to the postero-dorsal fibres of the anterior oblique muscles and arch medially

to join the major transverse muscles. Like the accessory oblique extensors

mentioned by Parker & Rich, the first three have independent dorso-lateral

attachments close to the posterior ends of the central muscles, but in the fourth

and fifth segments the apparently analogous strands are connected with the

anterior oblique muscles.

By reference to the relative positions of other muscles, a narrow bundle,

which is closely applied to the sixth anterior oblique, may be determined as

dorso-lateral muscle 6 (figs 11, 13), although it bears some resemblance to the

ventral branch of the transverse muscle in the sixth abdominal segment of

Astacus (Schmidt, 1915). It originates proximally in the sixth segment and

bends medially to join the last transverse muscle.

Posterior oblique muscles (Figs 11, 13, 54)

Attached dorso-laterally on the first to the fourth abdominal terga, and

perceptible in front of the heads of the oblique transverse muscles, are four of

the six posterior oblique muscles. Each passes ventrally as a flat band adjacent

to the oblique transverse muscle, but extends through two segments to insert

distally in the second of these close to the tendon of the auxiliary muscle; as a

rule, it also has a posterior slip connected with the neighbouring auxiliary

muscle. Posterior obliques 2 and 5 (the first and fourth in the abdomen) are

narrower than the other two, but they are all relatively strong and are capable

of assisting the anterior obliques in flexing the abdomen.

Probably belonging to this series are two additional muscles, one in the

posterior region of the thorax and the other in the fifth abdominal segment.

The former consists of two flat strips attached to a ventral inscription on the

anterior head of the first central muscle, and both are thought to represent

posterior oblique muscle 1 (figs 8, 11, 13). The outer slip (fig. 11) passes below

anterior oblique muscle 1 and is inserted somewhat dorso-lateral to the insertion

of the lateral part of the anterior thoracic muscle on the medial sclerite of the

first abdominal sternum. The inner slip (figs 8, 13) is more medial and con-

tinues into the first abdominal segment, where it becomes applied to the

anterior face of the minor transverse muscle (transverse 2 5).

The other muscle of uncertain homology has provisionally been called

posterior oblique muscle 6 (fig. 13). It is a somewhat fore-shortened, longitudinal

element arising near and running parallel to the last oblique transverse muscle.

It is inserted close to the last central muscle on the anterior margin of the sixth

segment.

Flexor muscles of telson (Fig. 30)

While the telson is intimately linked to the uropod on each side by the

telso-uropedal muscle (p. 105), it can also be bent forcibly beneath the last

abdominal segment by the contraction of three pairs of strong flexor muscles.

These are probably most frequently used when the animal is resting or walking

THE ANATOMY OF THE CAPE ROCK LOBSTER 63

to and fro or creeping backward into rock crevices. The telson and the uropods

are then normally tucked under the abdomen, but the main driving force for

rapid backward movement of an animal in flight is provided by the contraction

of the powerful abdominal flexor muscles in conjunction with tHe scooping

action of the tail-fan.

Most of the fibres of the short thick anterior flexor muscle of the telson spring

from the postero-ventral face of the tendon of the dorsal rotator muscle of the

uropod, but some are also attached to the tendon of the last anterior oblique

muscle. The anterior flexor passes obliquely inward and backward and has a

broad dorso-medial insertion in the proximal part of the telson.

The posterior flexor of the telson is a longer and a more conspicuous muscle

which has its origin at the posterior end of the tendon of the last anterior

oblique muscle. It extends below and slightly lateral to the anterior flexor of

the telson, and its large insertion covers a considerable part of the antero-dorsal

wall of the telson.

From an attachment on the tendon of the last anterior oblique muscle in

the distal region of the sixth abdominal segment, the broad flat ventral flexor

of the telson runs below the preceding muscle and is inserted ventro-laterally

in the telson. This muscle is absent in Astacus (Schmidt, 1915), but in Pandalus

(Berkeley, 1928) there are three pairs of flexor muscles resembling those of

Ff. lalandiz.

Anal compressor muscle (Figs 8, 13, 30, 63, 77)

Situated medio-ventrally in the last abdominal segment and the proximal

part of the telson, this fairly strong muscle arises partly antero-ventrally on the

sixth sternum and partly on the prolonged tendon of the last anterior oblique

muscle. It inserts ventrally without tendinous material on a crescentic fold

antero-lateral to the anus.

Anal dilatator muscle (Figs 8, 13, 30, 63)

Running parallel to the preceding muscle and having a somewhat similar

attachment on the tendon of anterior oblique muscle 6, this equally strong,

but more lateral, muscle has an insertion along the base of the anal lobe. While

it serves to open the anus, contraction of the compressor muscle closes the

aperture.

Abdominal superficial ventral muscles (Figs 8, 13, 14, 54)

The term ventral membrane muscles has been preferred by Pilgrim &

Wiersma (1963) for this system of paired, segmentally-repeated elements, which

operate during flexion of the abdomen. They are generally considered to be a

continuation of the series of superficial ventral muscles in the thorax, but,

strangely enough, there is none in the first abdominal segment of 7. lalandii.

In each half of the other segments the muscles usually have a somewhat

latero-ventral attachment on the intersternal arthrodial membrane, and are

divisible into lateral and medial portions (fig. 14). The lateral band consists

of fairly strong, almost straight fibres, which slightly overlap the medial fibres

64 ANNALS OF THE SOUTH AFRICAN MUSEUM

ant. oblique 5 attachment

osterior sternal ridge 3

: ant. oblique 3 insertion

intersternal membrane post. oblique 4 insertion

medial fibres dnt. oblique 6 attachment

Fed eyes ant. oblique 4 insertion

tendon auxiliary 4 ant. oblique 5 insertion

Wu Og

post. oblique 5 insertion

tendon auxiliary 5 ant. oblique & insertion

Posterior sternal ridge 6

Fic. 14. Diagrammatic inner view of last three abdominal sterna, showing the approximate

arrangement of the superficial ventral muscles.

and are inserted partly on the anterior and partly on the posterior edges of the

posterior ridge of the sternum. The medial fibres are appreciably thinner and

tend to slope inward to insert on the proximal part of the posterior sternal ridge

in front of the insertions of the anterior and posterior oblique muscles and the

tendon of the auxiliary muscle. In most segments, however, they do not reach

the mid-ventral line, and a gap occurs between them and the ventral nerve

cord.

As observed by Schmidt (1915) in Astacus and by Pilgrim & Wiersma

(1963) in Procambarus, there is an additional strip of medial fibres in the fifth

abdominal segment. This has a normal attachment on the intersternal mem-

brane between the fourth and fifth segments but, while the outer medial fibres

are inserted on the ridge of the fifth sternum in front of the tendon of the last

auxiliary muscle, this inner bundle extends farther back and is inserted on the

intersternal membrane between the fifth and sixth segments, practically

meeting the one of the other side in the mid-ventral line. The reason for this

modification is not immediately apparent, but it seems as though the medial

fibres are usually more or less aligned with the insertions of the anterior and

posterior oblique muscles. Consequently, the addition of another medial band

stretching across the fifth sternum may be correlated with the foreshortening

of the fifth anterior oblique and its insertion and that of the fifth posterior

oblique near the proximal edge of the sixth sternum.

Perhaps owing to the complex musculature associated with the uropods

and the telson, the superficial ventral muscles of the sixth segment (fig. 14)

are reduced to relatively strong, medial fibres which underlie the last ganglion

of the ventral nerve cord. Two rather narrow bundles are evident, the outer

overlapping the inner; both arise anteriorly on the intersternal membrane

between the fifth and sixth segments and are inserted distally on the broad

sternal bar of the sixth segment.

THE ANATOMY OF THE CAPE ROCK LOBSTER 65

(iu) Lateral abdominal muscles

Schmidt (1915) and Berkeley (1928) have described weak, serially-arranged

lateral abdominal muscles attached to the hypodermis and inserted on the

segmental articulations. Similar paired elements occur in the first three seg-

ments of 7. lalandii, but in the posterior segments they seem to be replaced by

fibrous tissue. The first (figs 11, 12) is an obvious band which originates on the

proximal border of the first abdominal segment and is joined to auxiliary

muscle 1 behind it by tough fibrous tissue that passes medial to the hinge

joint. The muscles in the second and third segments are less conspicuous, and.

consist of delicate strands extending from the tergum behind the insertion of

the central mass of muscles to the hinge joint but, like the first muscle, they

are also connected by tendinous material with neighbouring auxiliary muscles.

Lateral muscles were also observed by Daniel (1931) in the first three abdo-

minal segments of Homarus and Palinurus, but the latter is exceptional in

having two pairs, instead of a single pair, in each of these segments.

2. MUSCLES OF THE EYE (Fig. 15)

Each eye consists of a two-segmented peduncle and a swollen optic cup,

at the distal extremity of which the darkly-pigmented visual portion is located.

The optic cup and the peduncle are united by a thin, flexible, cuticular mem-

brane, and the second peduncular segment, which has a calcified sclerite

covering its exposed surface, is movable on the first segment. The latter projects

laterally beneath the rostrum, and it and the base of the second segment are

cushioned against the pedate process by a fairly wide, pliable membrane. The

basal segments of the two eyestalks are confluent in the mid-dorsal line and

together form the middle cylinder, which is located below the rostum and has

a thickened dorsal wall. The middle cylinder, a term used by Berkeley (1928)

and Cochran (1935), has been variously interpreted by different observers.

Parker & Rich (1893) defined it as a mid-dorsal calcification of the arthrodial

membrane of the eyestalks and named it the ‘inter-ophthalmic sclerite . .

having the form of a half cylinder’, while Schmidt (1915), Baumann (1921),

and Elofsson (1963, 1964) have referred to it respectively as the ‘mittleren

Chitinring’, the ‘Augenring’, and part of the ‘bec ocellaire’. One of the features

mentioned in Borradaile’s (1907) key is that the eyes of Palinuridae ‘are not

enclosed in separate orbits formed by the edge of the carapace’, a statement

which probably alludes to the coalescence of the basal segments of the eye-

stalks. On the other hand, the comparatively small eyes of the Scyllaridae are

separated by the wide frontal margin of the head and are lodged in individual

sockets. The two eyestalks of Jasus and some other Decapoda are obviously

fused mid-dorsally and are free from the overlying rostrum. Ventrally, how-

ever, the basal segments of both eyestalks are attached by a thin arthrodial

membrane to the margins of the pedate processes and to the sclerite herein

termed the antennal epimeron (fig. 3). The united eyestalks thus have a com-

mon articular cavity, called the ophthalmic fenestra by Parker & Rich (1893),

66 ANNALS OF THE SOUTH AFRICAN MUSEUM

and consequently the middle cylinder is incomplete ventrally.

As the eyes are normally laterally inclined and their stalks are almost at

right angles to the longitudinal axis of the body, the terms medial and lateral,

which are appropriate to the more porrect eyes of Astacus and Pandalus, are

hardly applicable but have been retained, even though they are descriptive of

the functional anterior and posterior surfaces. The eye musculature is complex

and comparable with that of other Decapoda, but from observations of live

animals movement of the eyestalk seems to be very slight and difficult to

detect, although when the eyes are being cleaned by the pereiopods they are

moved freely in various directions.

adductor medial retractor

- optic cup

attractor

ventral retractor

middle cylinder

dorsal retractor post. basal

abductor ant. basal

lateral retractor tendon

[i= ||

Fic. 15. Muscles of left eye, dorsal view.

Anterior basal

This fairly long, paired muscle arises on a strong median tendon from the

median apodeme of the epistoma (fig. 8). The tendon subsequently bifurcates

to support the two muscles which pass forward and upward on either side of

the cerebral artery and are inserted adjacent to each other on the postero-

dorsal edge of the subrostral cylinder of the fused eyestalks. As in other Deca-

poda, contraction of the two muscles may depress the cylinder and cause a

slight rotation of the eyes.

Posterior basal

The median tendon of the previous muscle is continued forward and again

divides to two shorter and more posterior muscles. These diverge somewhat as

they extend upward to be inserted by tendinous material mid-dorsally on the

body wall at the base of the rostrum and near the medial margin of the attach-

ment of the anterior gastric muscle. On each side there is another long tendon

which passes backward and outward from the insertion of each posterior basal

muscle to a more distal part of the wall of the head.

As the median tendon runs between the two circum-oesophageal con-

nectives and the two pairs of basal eye muscles overlie the cerebral ganglia, it

would seem that the whole combines to support and protect the anterior part

of the nervous system. At the same time, the posterior basal muscles are adjacent

THE ANATOMY OF THE CAPE ROCK LOBSTER 67

to the cor frontale at the anterior end of the median ophthalmic artery, and it

is conceivable that their contraction may be correlated with the propulsion of

blood from this arterial dilatation into the brain and the eyes.

Aitractor

There are no muscles associated with the projecting part of the first seg-

ment of the eyestalk, but the second segment contains a short, stout, rather

conical muscle, which has been identified with the musculus oculi attractor of

Astacus (Schmidt, 1915). It is attached ventrally near the junction of the two

segments and passes slightly obliquely upward and forward to a broad dorsal

insertion in the distal part of the second segment. A somewhat similar muscle

has been described by Parker & Rich (1893) as the rotator muscle of the basal

sclerite in asus edwardsii. Probably it is partly antagonistic to the basal eye

muscles in rotating and perhaps slightly compressing the second segment.

According to Berkeley (1928) and Cochran (1935), the attractor eye muscle

of the animals dissected by them is located in the middle cylinder, but this is

obviously a misinterpretation of the paired apical muscle and, following on

this, the muscle identified by them as the adductor is in all probability the

attractor eye muscle as defined by Schmidt.

Two pairs of musculi compressores annuli have been described in Natantia

by Elofsson (1964), who maintains that both are innervated by the apical

nerves, but admits that the supply to the musculus compressor annuli anterior

is usually indistinct. It seems likely that Elofsson’s posterior compressor muscles

are homologous to the apical muscles of Jasus, and these are certainly supplied

by the apical nerves (fig. 61). Specific structural and myological differences

doubtless exist and, while not wishing to dogmatize, it may be suggested that

the anterior pair of mm. compressores annuli observed by Elofsson in Natantia

are analogous to the attractor eye muscles of Reptantia. In Jasus, at least, the

attractor muscle of each eye is located in the eyestalk proper, and its innerva-

tion by the second oculomotor nerve (figs 59, 61) may account for Elofsson’s

difficulty in tracing the nerve supply in sections of Natantia.

Abductor

As in Astacus (Schmidt, 1915), this muscle is attached ventrally by a short

tendon in the second segment of the eyestalk near the origin of the attractor

muscle and is inserted distally in the optic cup. It rotates the latter backward

relative to its longitudinal axis and appears to be less substantial than that of

Astacus.

Adductor

Arising dorso-medially at the junction of the optic cup and the eyestalk,

this relatively broad muscle runs obliquely forward to a medial insertion on the

wall of the optic cup. In moving the eye forward, it opposes the abductor

muscle, but differs from the analogous muscle of Astacus in being confined to the

optic cup and not to the second peduncular segment.

68 ANNALS OF THE SOUTH AFRICAN MUSEUM

Retractor muscles

As in the species investigated by Schmidt (1915), Berkeley (1928), and

Cochran (1935), retraction and rotation of the eye about its longitudinal axis

are accomplished by four conspicuous muscles, all of which originate on the

flexible membrane between the eyestalk and the optic cup and are inserted in

the latter at different levels.

Dorsal retractor

This is one of the most prominent of the eye muscles; it arises dorsally and

slants slightly backward to a dorso-lateral insertion in the distal part of the

optic cup. In addition to moving the optic cup upward, it is somewhat antagon-

istic to the adductor muscle.

Ventral retractor

Being located below the optic ganglia, this is the only ventral muscle of the

eye. It lies opposite the dorsal retractor, but is rather broader and pursues a

straighter course from the articular membrane to the ventro-distal region of

the optic cup. Unlike the other retractor muscles, it does not participate in the

rotation of the optic cup.

Lateral retractor

The two distinct, relatively stout bundles of this muscle are attached

laterally to the cuticular membrane. The anterior or inner portion is the shorter

of the two and is inserted proximally in the optic cup above the dorsal retractor

muscle; the broader posterior or outer section partly obscures the abductor

muscle and is applied to the lateral wall of the optic cup. Both parts effect a

strong outward and backward movement of the cup.

Medial retractor

Partly overlapping the adductor muscle, this short element originates

close to the dorsal retractor and passes obliquely to a medial insertion in the

proximal part of the optic cup. It is the weakest of the eye muscles and probably

plays a minor part in the rotation of the optic cup.

3. MUSCLES OF THE APPENDAGES

The nomenclature applied by Schmidt (1915) to the appendicular muscu-

lature of Astacus has been adhered to as closely as possible and, to abridge the

descriptions and obviate unnecessary repetition of the function of homologous

muscles, a brief explanation of Schmidt’s usage of the terms may be given.

Berkeley’s (1928) account of the myology of Pandalus has also been based on

Schmidt’s investigations, while Cochran (1935) has compared her findings in

Callinectes sapidus with those of Schmidt and Berkeley. Reference to the observa-

tions of these authors is therefore implied in comparisons made between 7.

lalandi and any of these three decapods.

In the second and third maxillipeds and in the five pairs of pereiopods the

action of the segments of the protopodite and the endopodite is to some extent

THE ANATOMY OF THE CAPE ROCK LOBSTER 69

governed by articulating joints (fig. 16) and, as a rule, each segment moves

about an axis perpendicular to that of the segment proximal to it. The disposi-

tion of the muscles effecting these movements is thus fairly uniform in most of

the thoracic appendages, and the terminology is descriptive of their function.

posterior joint

orthrodial membrane

dorsal joint,

ONS 3} Upropodite

ventral joint

carpopodite posterior joint

arthrodial membrane

“wi Og

dorsal: joint

posterior joint

erthrodial membrane

dorsal joint—_,

attachment of coxopodite

basipodite

protopodite

setiferous process

ventral joint

Fic. 16. Right first pereiopod of small female, posterior (caudal)

view.

The main muscles which move the protopodite of any appendage are

usually attached to parts of the endophragmal skeleton, particularly to the

endopleurites and the endosternites, and they occupy the upper or pleural and

the lower or sternal muscle chambers (figs 2, 7). Whereas the terms promotor

and remotor are assigned to the muscles which respectively rotate the coxopodite

forward and backward about an axis almost perpendicular to the sagittal plane,

the names levator and depressor are reserved for the muscles which raise and lower

the basipodite in a dorso-ventral plane. Similar movements are apparent in

the segments of the endopodite but, to distinguish their muscles from those of

the two segments of the protopodite, a different set of terms has been devised.

Thus, the muscles which are analogous to the promotors and the remotors are

respectively called the froductors and the reductors, while those which correspond

to the levators and the depressors are termed the abductors and the adductors.

Brief mention must also be made of the terms used in connexion with the

attachments and insertions of the muscles described in the following account.

As most of the appendages are somewhat flattened against the ventral surface

of the body, their upper and lower surfaces are obviously dorsal and ventral.

The coxopodites of the pereiopods are, however, set at an angle to the horizontal

axis of the body, and the limbs tend to be poised more obliquely outward,

70 ANNALS OF THE SOUTH AFRICAN MUSEUM

especially when they are supporting the body during ambulation; as is cus-

tomary, the anterior and posterior surfaces of the segments are called rostral

and caudal respectively.

The appendicular muscles were dissected in sequence from the anterior

to the posterior end of the specimen and, while the mouth-parts and the pereio-

pods are most easily examined from the dorsal or the frontal aspect after removal

of the thoracic trunk musculature, the pleopods are more directly approached

from the ventral surface. The individual muscle attachments and insertions

were carefully ascertained and each appendage, with its related exoskeletal

and endoskeletal elements, was removed upon completion of the observations

of its muscles. The conclusions have been diagrammatically represented in the

accompanying figures, but in some of the larger appendages the full extent of

the massive proximal muscles has not been indicated, and the joints and the

arthrodial membranes have been omitted.

(a) The antennule (Fig. 17)

The basal segment of this slender, active appendage has no external

articulations with the head, but is attached by an extensive arthrodial mem-

brane and is capable of rotation in various directions. There is, however, a

strong internal process from the dorsal base of the first peduncular segment.

This articulates with a lateral projection of the medial partition between the

two antennulary sockets, and has been termed a hinge (fig. 60). The three

peduncular segments are interconnected by relatively wide membranes and the

second and third segments are almost as mobile as the first; the second segment

has a slight dorsal joint and can be moved outward at an acute angle on the

first segment, while the third segment has small lateral and medial joints and

bends sharply upward and downward on the second segment. The muscles

operating the segments cannot be homologized easily with those of a typical

stenopodium, but the fact that there is a duplication of antagonistic muscles

associated with the proximal segment seems to suggest that this segment may

represent a fusion of the coxopodite and basipodite of a generalized appendage.

Promotor

This strong muscle arises on the dorsal wall of the head below the pedate

process and is inserted dorsally by a long flat tendon on the proximal margin

of the first segment of the peduncle above its dorsal hinge. By its contraction

the antennule is raised in the sagittal plane.

Remotors (a, 6)

Two muscles, which are unrepresented in Astacus and Pandalus but seem

to be present in Callinectes sapidus, are considered to be antagonistic to the pro-

motor muscle and, like the remotor muscles of other appendages, have their

origin in the body.

At its attachment on the lateral ridge of the antennulary socket, remotor a

THE ANATOMY OF THE CAPE ROCK LOBSTER 71

is wide, but it narrows appreciably towards its lateral insertion by a broad

tendon on the proximal margin of the first segment.

flagella

att

liSrectieton flagelli

adductor 2

)}

reductor 1b

reductor 3 S\

abductor 2 |

A statocyst

reductor la ££

Wnt promotor

Y \\ Eg epimeron

remotor b yp S

=\) Li =

sternum Wf IN S

| \ eos

epistoma~_|} mee

remotor a f

Fic. 17. Muscles of left antennule, lateral

view.

Remotor b is much shorter but, nevertheless, is fairly broad and strong. It

arises ventrally at the junction of the antennulary sternum and the epistoma,

and passes slightly obliquely upward and forward to be inserted laterally on

the first segment adjacent to remotor a.

Reductor 1 (a, b)

An adductor and two abductor muscles have been observed by Berkeley

(1928) in the first antennulary segment of Pandalus, but they do not seem to be

homologous to two muscles that occur in Jasus. The latter bear a closer resem-

blance to the two muscles described as remotors in Astacus and Pandalus and are

similarly disposed in the first segment. As their action is probably antagonistic

to that of the promotor muscle, they are complementary to the remotor muscles

in lowering the appendage.

Reductor 1 a is attached latero-ventrally by a strong, blunt tendon on the

proximal edge of the first segment. Its fibres are unequal in length and are

inserted along the ventro-lateral wall of the proximal half of the first segment.

Lying below the level of the statocyst, the comparatively shorter reductor

1 } originates medio-ventrally on a strong tendon on the proximal margin of

the first segment. It spreads out somewhat and is inserted medio-ventrally in

72 ANNALS OF THE SOUTH AFRICAN MUSEUM

the middle of the segment. There is a tendency for the two reductor muscles

to split into two heads at their insertion in such a way that the ventral section

of each is distinct from the lateral or the medial portion, as the case may be.

Abductor 2

In Astacus and Pandalus the second antennulary segment is raised and

lowered in the sagittal plane respectively by a productor and a reductor

muscle, but in Yasus the two antagonistic muscles appear to function more in

the outward and inward movements of the segment. They have therefore been

labelled as the abductor and adductor muscles, and it is of interest that in

Callinectes sapidus the second segment is operated by four muscles and seems to

combine the features of Astaciis and Pandalus on the one hand with those of

Jasus on the other.

Distal to the statocyst in the first segment is the broad lateral attachment

of abductor 2, while its insertion takes place ventro-laterally by a fairly stout

tendon on the proximal margin of the second segment.

Adductor 2

The broad attachment of this somewhat smaller muscle is also in the distal

half of the first segment, but on its medial wall; it is inserted medially by a short

tendon on the proximal border of the second segment.

Productor 3

The third segment is raised dorsally in the sagittal plane by a rather short

muscle, which arises laterally about the middle of the second segment and is

inserted dorso-laterally by a short tendon on the proximal edge of the third

segment.

Reductor 3

The action of the previous muscle is opposed by this somewhat longer and

stronger one, which originates dorso-medially in the proximal part of the second

segment. It passes obliquely across the segment and is inserted ventrally by

a long flat tendon on the proximal margin of the third segment.

Reductor flagelli

Only one muscle is associated with the activity of the antennulary flagella,

neither of which has any intrinsic flexor muscles. The single muscle is attached

dorsally and medially in the proximal part of the third segment and is inserted

ventrally by a long tendon on the proximal edge of the outer flagellum. It

moves the latter outward and downward about an axis somewhat inclined to

the sagittal plane, and is responsible for its constant vibration against the more

inert inner flagellum.

(b) The antenna (Fig. 18)

As there has been a reduction in the number of segments in the antennal

peduncle in all Scyllaridea, the proximal antennal muscles can hardly be

likened to those of the few decapods that have previously been described. In

THE ANATOMY OF THE CAPE ROCK LOBSTER 73

his account of the antennal musculature of Astacus, Schmidt (1915) assigned

certain small basal muscles to the basipodite and an ill-defined ischiopodite,

and identified the three remaining segments as the meropodite, the carpo-

podite and the propodite, and the flagellum as the dactylopodite but, according

to Balss (1940), Schmidt misconstrued the proximal components of the antennal

peduncle and, consequently, his terminology is inaccurate. The disposition of

the antennal muscles of Jasus suggests that the epistoma and the antennal

coxopodite are fused and that the basal segment is twofold but, to obviate

confusion, the three segments have simply been numbered and their muscles

named according to their supposed functions.

The segments of the peduncle articulate with one another by strong joints

which are so arranged that each segment moves in a plane different from that

of the preceding member. The segments are also set slightly obliquely on one

another and, when the antenna is fully extended, the arrangement of the inter-

segmental joints seems to differ from that of the pereiopods. It is possible,

however, that the dorsal and ventral antennal joints are functionally similar to

the anterior and posterior leg joints and that the medial and lateral antennal

joints are comparable with the dorsal and ventral joints of the leg. The first

segment, which has wide arthrodial membranes at its base, articulates dorso-

medially with the frontal tubercle of the head and ventro-laterally at the

junction of the epistoma with the head exoskeleton and is raised and lowered

slightly obliquely in the sagittal plane. Between the first and second segments

there are also fairly wide membranes and the joints are dorso-lateral and ventro-

medial in position; the second segment moves easily, being tilted inward and

upward on the one hand and outward and downward on the other. The third

segment has dorsal and ventral joints and pivots freely inward and forward and

outward and backward. The joints of the flagellum are almost medial and

lateral in position, and the movements tend to be obliquely upward and back-

ward and downward and forward, but the inclination of the segments and

differences in the planes of their articulations with one another also affect the

orientation of the flagellum. On the whole, however, the dorso-ventral move-

ments of the antenna are more vigorous than its lateral ones.

The main muscles operating the antenna as a whole are associated with the

basal segment, but the muscles of the other segments are equally powerful and

are characterized by long supporting tendons.

Promotor

Being superficial, this is a conspicuous element, but it also happens to be

flatter than most of the antennal muscles. It is attached by a wide surface

dorsally on the wall of the head (fig. 8) immediately in front of the cervical

groove, and passes forward as a broad band along the side of the fore-gut

medial to the mandibular minor abductor muscle and above the antennal

gland. It is inserted dorsally by a long, flat, strong tendon on the proximal

margin of segment 1 and, as it serves as the principal muscle for raising the

74 ANNALS OF THE SOUTH AFRICAN MUSEUM

[o)

: extensor flagelli

; flexor flagelli

fl iPS)

She extensor 3

adductor 2

abductor 2

reductor 2

Pproductor 2

depressor b

Ut! depressor a

epi stoma _/ f°

levator d

depressor c

Fic. 18. Muscles of left antenna, dorsal

view.

appendage, it is comparable to the antennal promotor muscle of Astacus and

Pandalus.

Remotor

In Astacus and Pandalus the remotor muscle is at least subequal to the

promotor, but what appears to be the corresponding muscle in Fasus is a narrow

slip that hardly seems capable of participating in movements of the antenna. It

originates laterally on the head wall between the attachments of the two lateral

adductors of the mandible and, passing downward and outward across the

main lobe of the labyrinth of the antennal gland (fig. 38), it spreads out a little

as it inserts laterally on the rim of the epistoma slightly antero-lateral to the

level of the excretory aperture. It thus extends between two immovable skeletal

parts and its function is obscure; perhaps it acts as a support for the labyrinth

and part of the bladder, or it may in some way be concerned in regulating the

elimination of urine from the ureter.

Levator

Arising by strong tendinous material on the outer face of the lateral

apodeme of the epistoma anterior to the ventral cephalic muscle, this sub-

stantial muscle runs upward and is inserted by a broad surface dorso-laterally

on the proximal border of the first segment.

THE ANATOMY OF THE CAPE ROCK LOBSTER 75

Depressors (a, 6, c, d)

There are four muscles which oppose the promotor and levator muscles

by lowering and rotating the antenna. Four antennal depressors have also been

described by Schmidt (1915) in Astacus while, according to Berkeley (1928),

three occur in Pandalus. It is uncertain if these are homologous to the muscles

of Fasus, but it seems probable that depressors a and b of Astacus and Fasus are

essentially similar and that the other two may be subject to specific differences.

Depressor a consists of two large heads, each with slanting fibres. The

outer head arises on the inner face of the lateral apodeme and the inner head

on the outer border of the medial apodeme of the epistoma, and they pass

respectively to the lateral and medial faces of a large, flat, vertical tendon

located medio-ventrally on the proximal margin of the first segment.

Contrasted with the other antennal muscles, depressor b is a short, rather

inconspicuous element lying near the postero-medial corner of the first segment.

It is attached close to the medial edge of the tendon of the promotor muscle

and slopes forward to its insertion by a fairly long and strong tendon below the

dorso-medial joint of the first segment.

Depressor c is a thick bundle arising anteriorly on the lateral apodeme of

the epistoma. Running forward below the levator muscle, it is inserted ventrally

by a flat tendon on the proximal border of the first segment.

Largely concealed dorsally by depressor a, depressor d is attached to the

anterior edge of the lateral apodeme of the epistoma medial to depressor c, and

is inserted close to depressor a by a short tendon.

Productor 2

The second antennal segment is operated by four muscles, the presence

of which is suggestive of its compound nature and reminiscent of the muscu-

jature described by Schmidt (1915) in the basal parts of the antennal peduncle

of Astacus. Like the first segment, it is set obliquely, and the movements pro-

moted by its muscles involve production and abduction on the one hand, as

against reduction and adduction on the other hand.

Productor 2 is a broad muscle arising dorsally on the proximal margin of

the first segment and, after narrowing somewhat, it is inserted dorsally on the

proximal edge of the second segment, on which it exerts an upward pull.

Reductor 2

This, the stronger of the two medial muscles, is attached dorsally and

ventrally on the proximal margin of the first segment and is inserted medio-

dorsally by a long, flat tendon on the proximal border of the second segment.

Its ventral fibres pass obliquely upward from their attachment and are mainly

responsible for the downward movement of the segment.

Abductor 2

Somewhat larger than the productor of the second segment, this muscle

has its origin both dorso-laterally and ventro-laterally in the proximal part of

76 ANNALS OF THE SOUTH AFRICAN MUSEUM

the first segment, its ventral fibres being particularly strong and slanted. It is

inserted ventro-laterally by a long, angled tendon on the proximal margin of

the second segment and pulls the latter outward.

Adductor 2

Arising medially on the proximal border of the first segment and inserted

medially on the proximal edge of the second segment, this relatively smaller

muscle supplements reductor 2 and draws the second segment inward towards

the mid-line.

Flexor 3

The third segment is moved outward by this thick muscle which occupies

the outer half of the second segment and is comparable to the flexor of the

antennal propodite in Schmidt’s (1915) account of Astacus. Its dorso-lateral,

lateral and ventral attachment covers a large area, but the muscle narrows as

it passes distally to insert ventro-laterally by a strong, somewhat folded tendon

on the proximal edge of the third segment.

Extensor 3

Like its antagonist, this larger and more powerful muscle has a wide

attachment, but arises dorsally and medially in the proximal part of the second

segment. It is inserted medially on the proximal margin of the third segment

by a long, flat tendon with a raised median spine.

Flexor flagelli

Corresponding to the flexor of the dactylopodite of Astacus, this muscle

moves the flagellum outward and backward relative to the third segment.

Its fibres are unequal in length and originate dorso-laterally and ventro-

laterally in the third segment. They all converge on a long, flat, vertical tendon

located laterally on the proximal edge of the flagellum.

Extensor flagelli

The fibres of this muscle also have a somewhat pinnate appearance, but

spring from the medio-dorsal and medio-ventral walls of the third segment.

They are inserted medially by a long, narrow, vertical tendon on the proximal

margin of the flagellum and oppose the action of the flagellar flexor muscle.

Because the heavy calcified body of the mandible articulates postero-

laterally by a condyle with the mandibular epimeron and is also attached

anteriorly to the supralabral ridge, its axis of movement is obliquely transverse

and it is practically incapable of true rotation. Its muscles are all extrinsic and,

like the proximal muscles of other appendages, arise either on the exoskeleton

or on the endoskeleton. They have been likened by Snodgrass (1938, 1950) to

the promotors and the remotors of a typical arthropod leg but, as they produce

movements towards and away from the mid-line in decapod Crustacea, they

serve essentially as adductors and abductors. Snodgrass (1950) concluded,

THE ANATOMY OF THE CAPE ROCK LOBSTER Wi

however, that the variation in the number and functional adaptation of the

mandibular muscles in different groups of Arthropoda did not warrant the

introduction of a functional terminology, but recognized the prevalence of

three primary groups of muscles, namely, an antero-dorsal (A), a postero-

dorsal (P), and a ventral group (V), in each of which there may be one or more

muscles. Nevertheless, these are comparable to the mandibular muscles of

Jasus, for which Schmidt’s (1915) nomenclature has been followed and, with

the abbreviations used by Snodgrass in brackets, the homologies may be sum-

marized thus: lateral adductors (1A, 2A); minor abductor (3A); anterior

adductor (1V); major abductor (2V); and posterior adductor (P).

In a comparative study of the jaw mechanisms of representatives of all

the major groups of arthropods, Manton (1964) has indicated that many of

the earlier conclusions relating to the basic structure and function of the

arthropod mandible are inaccurate. She has recognized two structural types of

mandibles, Types A and B, and two types of mandibular movements, Types I

and II. The mandibles of 7. lalandi clearly belong to structural type A, in

which the body of the mandible represents a modified gnathobase and the

basal part of the coxopodite. Furthermore, owing to their strong gripping

action in the transverse plane they are examples of type II, in which the

movement is described by Manton as a direct or primary abductor—adductor

one. Type II movement found in the more advanced Crustacea is, however,

considered to be a modification of the rolling type I movement which is

characteristic of the grinding mandibles of the Branchiopoda and the more

primitive Malacostraca, and the antagonistic muscles producing the type II

movement are remotors (adductors) and promotors (abductors). Thus, the

muscles described in 7. lalandii as antero-lateral, postero-lateral, and posterior

adductors are respectively remotor (adductor) muscle 1, remotor (adductor)

muscle 2, and remotor (adductor) muscle 4 in Manton’s account of Astacus and

Carcinus, while the minor and major abductors in 7. lalandit are the promotor

(abductor) muscle 3 and the promotor (abductor) muscle 6 of the crayfish

and the crab; the remaining muscle, the anterior adductor of 7. lalandii, is

comparable with the transverse muscle 5 a, which is attached to the head endo-

skeleton in the crayfish and is small in the crab.

Posterior adductor

This is the strongest and most conspicuous muscle of the mandible and

is its main adductor. It consists of two bundles of fibres which originate one

behind the other postero-laterally on the wall of the head anterior to the cervical

groove. The two bundles meet on a long, slender posterior apodeme which

extends downward at the side of the fore-gut and is articulated with the pos-

terior rim of the body of the mandible.

Anterior adductor

Attached to and supported by the transverse mandibular tendon which

juts antero-laterally below the cephalic apodeme, this broad muscle spreads

78 ANNALS OF THE SOUTH AFRICAN MUSEUM

flexor palpi a

major abductor

antero-lateral flexor palpi b

adductor flexor palpi c

15 mm.

postero-lateral

adductor

gnathal surface

cephalic apodeme

transverse mandibular

2 tendon

minor abductor

anterior apodeme

condyle

maxillary Pparaphragms

Sterna 5 & 6

Posterior adductor

5 anterior adductor thoracic paraphragms 1 & 2

Posterior apodeme

Fic. 19. Muscles of left mandible, dorsal view. The major abductor and the

anterior adductor muscles have been inordinately lengthened to indicate their

attachments respectively on and below the cephalic apodeme.

out and is inserted on the inner face of the posterior part of the body of the

mandible, practically filling this region, while the rest of the mandibular

concavity is occupied by digestive gland. It is complementary to the posterior

adductor and approximates the gnathal surface of the mandible to that of its

fellow.

Lateral adductors

Two of these muscles occur dorso-laterally on the anterior apodeme of the

mandible. The postero-lateral adductor is the more important of the two and

consists of numerous short, closely-packed fibres which have ‘a widespread

origin on the antero-lateral part of the hepatic region of the wall of the head

and are inserted over the outer convex surface of the anterior apodeme. The

antero-lateral adductor is short and flat and quite distinct from the postero-lateral

adductor, arising on the head wall antero-dorsal to it and being inserted on the

rim of the anterior apodeme close to the insertion of the major abductor

muscle. These two muscles assist the anterior adductor by tilting the anterior

part of the mandible towards the mid-line, and Snodgrass (1950) and Manton

(1964) have indicated that the strong gripping action of the decapod mandibles

is largely dependent on the development of the anterior apodeme which

provides leverage for the adductor muscles.

Abductors

The action of the adductor muscles is opposed by two distinct muscles

which are conformable with the major and minor abductors in Astacus. Arising

on the blunt antero-lateral extremity of the cephalic apodeme antero-dorsal

to the attachment of the anterior adductor, the broad major abductor passes

forward and outward to insert antero-laterally on the inside of the anterior

apodeme. In front of the cervical groove there is a row of short, flat muscle

fibres, which originate on the dorso-lateral gastric ridge of the head exoskeleton

and extend laterally to the upper rim of the anterior apodeme medial to the

THE ANATOMY OF THE CAPE ROCK LOBSTER 79

postero-lateral adductor muscle. They are probably equivalent to the minor

abductor of Astacus which, however, tapers towards its insertion by a short

tendon on the outside of the mandible.

Flexores palpi (a, b, c)

The three-segmented mandibular palp is joined to the body of the man-

dible by a pliable arthrodial membrane and is moved actively in front of the

mouth by one extrinsic and two intrinsic flexor muscles. As in Astacus, the palp

has no extensor muscles, but Schmidt (1915) has suggested that the elasticity

of the arthrodial membrane probably provides the necessary opposing force.

Flexor palpi a is relatively strong and originates medio-ventrally on the

posterior inner face of the body of the mandible beneath the medial part of

the anterior adductor muscle. It tapers towards its insertion by a short tendon

on the medial proximal edge of the first segment of the palp. The last segment

of the palp of Astacus is furnished with a flexor muscle, but in Jasus there are

two such muscles, flexores palpi b and ¢ which bend the two distal palpal seg-

ments. Each arises in one segment and is inserted medio-ventrally in the .

proximal part of the next segment.

(d) The first maxilla (Fig. 20)

As it plays an important part in the manipulation of the food, this small

flat appendage has well-developed muscles, most of which are thick and

cylindrical and cause strong rotation of the appendage on its slack arthrodial

membrane.

endopodite outer endite

depressor

remotor b

: NS Kt levator

remotor da ta E

ph promotor e

tendon of abductor

lateral ddductor

Fic. 20. Muscles of left first maxilla, dorsal view.

Promotor

This is a fairly stout muscle attached by a small tendon laterally on the

anterior fascia below the fused paraphragms of the fifth and sixth cephalic

segments and close to the sternal region. It passes somewhat obliquely outward

across the base of the appendage and is inserted dorso-laterally in the coxo-

80 ANNALS OF THE SOUTH AFRICAN MUSEUM

podite. It raises the appendage and rotates it forward about an axis slightly

inclined to the sagittal plane.

Remotor (a, 6)

As in Astacus and Pandalus, remotion of the appendage is effected by

adjacent dorsal and ventral muscles, which are ventral to the promotor and are

inserted laterally in the proximal part of the coxopodite. The dorsal remotor,

remotor a, arises close to the promotor and also has a short pointed tendon,

while the somewhat larger ventral muscle, remotor 6, originates without ten-

dinous material below both the dorsal remotor and the promotor.

Levator

Attached to the anterior fascia by tendinous tissue medial and ventral to

the promotor and inserted dorsally by a very short, broad tendon on the

proximal margin of the basipodite, this muscle raises the larger outer endite

and also moves it inward about an axis slightly inclined to the sagittal plane.

Depressor

Counteracting the levator muscle and running ventrally parallel to it,

this rather stronger unit has its origin ventrally on the anterior fascia and is

inserted ventrally on the proximal border of the basipodite.

Abductor

To compensate for its rather remote origin on the wall of the head dorsal

to the lateral adductors of the mandible, this small, conical muscle has a very

long, slender tendon which passes downward between the mandible and the

first maxilla and inserts laterally on the proximal edge of the coxopodite. Its

function is to pull the appendage away from the mouth. The presence of an

abductor tendon seems to be characteristic of Jasus, for one similar to that of

J. lalandii has also been reported in the first maxilla of 7. edwardsii by Parker &

Rich (1893).

Adductors

Two adductors, a lateral and a medial, oppose the abductor muscle and

approximate the endites to the mouth.

The lateral adductor is the stronger of the two and is attached to the wall of

the head near, but slightly postero-dorsal to, the origin of the abductor muscle.

It runs for some distance parallel to the tendon of the latter muscle, but enters

and traverses the coxopodite dorsally. As it travels medially, it splits into two

tendons, the posterior and stronger of which is inserted medially at the base of

the inner endite, while the anterior tendon passes to the base of the outer

endite. Apparently this muscle is slightly variable in different species. In

Astacus it arises by a long thin tendon and is inserted medio-dorsally in the

coxopodite, and the abductor muscle has no tendinous material. Two slender

muscles, called the m. adductor anterior and the m. adductor posterior

coxopoditis I maxillae by Cochran (1935), occur in Callinectes and are suggestive

of the separate insertions of the lateral adductor of Jasus.

THE ANATOMY OF THE CAPE ROCK LOBSTER 81

Closely applied to the posterior border of the lateral adductor, there is

another bundle which, at first sight, seems to belong to the first maxilla. Its

long, slender tendon, however, extends across the maxillary muscles and is

inserted at the lateral base of the paragnath, of which it is probably an adductor.

The short, rather broad medial adductor arises on the anterior fascia near

the fused cephalic sterna. It runs below and parallel to the levator muscle and

is inserted medially at the junction of the inner and outer endites.

Adductor endopoditis

Only one comparatively strong and almost cylindrical muscle operates

the endopodite and moves it towards the mid-line. It originates close to the

base of the outer endite and is inserted laterally in the proximal part of the

endopodite.

(e) The second maxilla (Fig. 21)

This much flattened appendage is largely thin-walled and the boundaries

of the coxopodite and basipodite are rather indistinct. The scaphognathite,

however, has a conspicuous, swollen, dorso-laterally sclerotized base, on which

it swings dorso-ventrally with a slight rotary action. The proximal muscles

almost fill the space between the fused paraphragms of the last two cephalic

segments and those of the first two thoracic segments, and the majority consti-

tute the so-called respiratory muscles which are generally considered to be the

chief agents controlling the movements of the scaphognathite.

scaphognathite endopodite endopodite

adductor endopoditis ¢

flexor of

scaphognathite

flexor of

scaphognathite

depressor

adductor coxopoditis

wu Oe

SS". promotor

Sv’

Ae \\ remotor

respiratory 2-6

respiratory 7 \ .

\ respiratory 1

Fic. 21. Muscles of left second maxilla, dorsal views; the promotor and respiratory muscle 1

have been removed in the diagram on the right.

Promotor

This thick strong muscle arises below the cephalic apodeme and passes

somewhat obliquely outward above the respiratory muscles. It is inserted

dorso-laterally on the proximal border of the coxopodite close to the posterior

skeletal swelling of the scaphognathite. It raises the coxopodite and also the

posterior half of the scaphognathite, so that in some respects it functions as

a respiratory muscle.

82 ANNALS OF THE SOUTH AFRICAN MUSEUM

Remotor

A fairly strong remotor muscle has been reported in the second maxilla

of other decapods, but was not observed in all specimens of 7. Jalandii. It

springs medio-ventrally from the sternal region below the cephalic apodeme

and runs to the ventro-lateral margin of the coxopodite. It underlies the

respiratory muscles, and is not so markedly separated from them as is the

promotor muscle.

Adductor coxopoditis

Attached ventro-medially below the fused cephalic paraphragms, which

are omitted in figure 21, this narrow, straight, but fairly strong element passes

dorsally over the respiratory muscles. It has a ventral insertion on the proximal

border of the coxopodite, and pulls the latter inward and backward.

Depressor

In Astacus and Callinectes the depressor muscle has two heads, but in Pan-

dalus and F. lalandi it is a single, fairly broad muscle which arises medially in

the sternal region. It proceeds outward and forward through the coxopodite

and is inserted mid-dorsally on the proximal margin of the basipodite. It

causes an inward and downward movement of the basipodite, and, as in other

decapods, it has no antagonistic levator muscle.

Adductor endopoditis

This muscle is inconspicuous in most specimens and consists of only a

few very short fibres which are attached dorso-medially in the basipodite and

are inserted ventrally in the proximal part of the endopodite. It has no antago-

nistic muscle, but this also applies to Astacus, Pandalus, and Callinectes, and

Schmidt (1915) has suggested that its action is opposed by the resiliency of the

flexible arthrodial membrane. Nevertheless, the endopodite of the second

maxilla of asus seems to have little independent movement, and may be

influenced by the contraction of the depressor muscle.

Flexor muscle of scaphognathite

The anterior half of the scaphognathite contains a relatively strong muscle

which is partly responsible for the sinuous movements of this part of the

appendage. Its two bundles, which may be analogous to the superior and

inferior flexor muscles of the scaphognathite of Pandalus, originate at the

junction of the protopodite and the scaphognathite and, on passing into the

latter, some of the anterior fibres become slightly twisted.

Respiratory muscles

In common with other decapods, there is a complex set of seven muscles,

most of which are inserted in the swollen base of the scaphognathite. Together

with the flexor muscle, they are thought to bring about the undulatory move-

ments of the scaphognathite whereby the respiratory current of water is swept

out of the prebranchial chamber.

It is doubtful if they are all identical with those that have been described

THE ANATOMY OF THE CAPE ROCK LOBSTER 83

in Astacus, Pandalus, and Callinectes, but the broad first respiratory muscle is essen-

tially similar in all four species. In asus it arises laterally on the fused thoracic

paraphragms and extends forward and outward beneath the lateral part of

the promotor muscle. It has a dorsal and somewhat distal insertion in the base

of the scaphognathite, and appears to be one of the main muscles for raising

the scaphognathite.

The second to the sixth respiratory muscles are so compressed that, upon

cursory examination, they appear as two transverse bands lying below the

promotor muscle in the angle formed by the last cephalic and the first thoracic

paraphragms. Arising in a row on the anterior fascia, they run outward parallel

to one another, and laterally they lie ventral to the first respiratory muscle.

They are fairly easily separated, however, and the third, fourth, and fifth of

the series are distinguished by distinct tendons at their insertions on different

levels of the basal swelling of the scaphognathite. Of this group, the second and

the third are the most conspicuous, while the fifth is a narrow slip, partially

obscured dorsally by the sixth muscle.

The seventh respiratory muscle, like that of Pandalus, is short, broad, and

practically confined to the scaphognathite. It is covered dorsally by the inser-

tion of the first repiratory muscle and consists of three small wedge-shaped

bundles which are attached to the distal margin of the coxopodite and spread

out as they insert ventrally and distally in the scaphognathite posterior to the

flexor muscle.

(f) The first maxilliped (Fig. 22)

The muscles of this appendage are hardly consistent with those of the other

two maxillipeds and present a closer resemblance to the arrangement in the

maxillae because, apart from the more or less cylindrical and freely movable

exopodite, the parts are markedly flattened. Endites 1 and 2 are medial lobes of

the protopodite, probably respectively representing expansions of the coxopodite

and the basipodite. The endopodite, which is also flattened and joined medially

to endite 2, has little independent movement; in fact, some of the muscles

seem capable of moving the appendage as a whole rather than its individual

parts, and none of them has supporting tendons. They are broadly similar to

those of the first maxillipeds of Astacus and Pandalus, but the arrangement

appears to vary with the species and the homologies of some of the muscles

are uncertain. Several muscles, which are unrepresented in other forms, occur

in Callinectes; Cochran (1935) has numbered these and made tentative sug-

gestions as to the resemblances between some of them and the muscles of

Astacus.

Promotor medialis

This broad muscle is attached medially on the endosternite and not on the

fused thoracic paraphragms as in Astacus and Pandalus. It is inserted dorsally

on the proximal margin of the coxopodite and, while it moves the latter forward

84 ANNALS OF THE SOUTH AFRICAN MUSEUM

ESS

bE ~

a iy endopodite

flagellar ai

abductor flagelli

adductor éxopoditis

abductor exopod itis

Promotor medialis

attractor b epipoditis

remotor

Promotor lateralis

epipodite

Fic. 22. Muscles of left first maxilliped, dorsal view.

or upward, to some extent it may also be adducent in function. It is directed

more laterally than the medial promotor of Astacus, and in some respects

resembles the levator muscle described by Schmidt (1915).

Promotor lateralis

Originating laterally on the fused paraphragms of the first two thoracic

segments, this rather longer and narrower muscle is inserted dorso-laterally

on the proximal edge of the coxopodite. It doubtless assists the previous muscle

in raising the appendage, but may also be slightly antagonistic to it by causing

an outward movement.

Remotor

Jasus resembles Pandalus and differs from Astacus in having a remotor

muscle, which arises below the lateral promotor on the fused thoracic para-

phragms. It has a ventro-lateral insertion on the proximal border of the

coxopodite and, although weaker than either of the promotor muscles, it is

capable of opposing their action by lowering the appendage.

Attractores epipoditis (a, b)

As in Pandalus, elevation of the epipodite is effected by two muscles. Attractor

epipoditis a is a conical element arising ventrally in the coxopodite and passing

outward to insert near the shoulder of the epipodite. Unlike Pandalus, however,

this muscle is not repeated in other thoracic segments, although the epipodite

THE ANATOMY OF THE CAPE ROCK LOBSTER 85

is joined to the setiferous process of the coxopodite by a flexible membrane. In

both the adult and the puerulus stage blood channels and strands of fibrous

tissue, but no recognizable muscle fibres, occur at the base of the epipodite, and

any necessary changes in its position will probably be produced by movements

of the limb.

The much stronger attractor epipoditis b is attached laterally to the fused

thoracic paraphragms close to the lateral promotor, to which it runs parallel

and inserts at the junction of the epipodite with. the coxopodite. Schmidt

(1915) suggested that in Astacus this muscle might have replaced the non-

existent remotor muscle but, as Berkeley (1928) has indicated, this opinion is

nullified by the presence of attractors of the epipodite, as well as a remotor, in

the first maxilliped of other species.

Levator

From a medial attachment on the endosternite near the base of endite 1,

this conspicuous muscle extends outward through the coxopodite to the proxi-

mal border of the basipodite and is concerned with the outward movement of

the appendage.

Depressor

Opposing the action of the levator muscle and attached medio-ventrally

below it, this short muscle is directed forward to its medio-ventral insertion on

the proximal margin of endite 1. In Astacus and Pandalus it has a more normal

insertion at the proximal edge of the basipodite, but the position of muscle

number 75 in Callinectes is somewhat similar to that of the depressor in Jasus,

and was considered by Cochran (1935) to be reminiscent of the depressor of

Astacus and Pandalus.

According to Berkeley, two adductor muscles are associated with the endo-

podite of Pandalus, while a single muscle in Astacus was identified by Schmidt as

a reductor of the endopodite. None of these is present in Callinectes or Fasus, but

the muscle in Astacus is suggestive of attractor epipoditis a of Pandalus and Jasus.

Abductor exopoditis

Originating ventro-laterally in the basipodite, this relatively short entity

passes into the ventral proximal region of the exopodite and causes an outward

and backward movement of this part of the appendage. A similar muscle is

present in Pandalus, but not in Astacus or Callinectes.

Adductor exopoditis

This equally short but rather thicker muscle is attached close to its anta-

gonist and is inserted medially in the proximal part of the exopodite.

Abductor flagelli

In all three maxillipeds there is a single, fairly strong muscle which

practically fills the peduncle of the exopodite and, being inserted ventrally at

the proximal end of the flagellum, it functions in the outward movement of

86 ANNALS OF THE SOUTH AFRICAN MUSEUM

this structure. The abductor flagelli of the first maxilliped is stouter than that

of the other two maxillipeds and pursues a straighter and more medial course

through the peduncle, its insertion being mid-ventral, while that of the second

and third maxillipeds tends to be ventro-lateral.

Flagellar muscle

In each of the three maxillipeds, the flagellum of the exopodite has an

intrinsic muscle which is responsible for its active movements in various

directions. It consists of thin muscle strands arising from the base and annula-

tions of the flagellum and extending down its length to an insertion in the

terminal segment.

(g) The second maxilliped (Fig. 23)

The second and third maxillipeds differ from the first in being pediform

and in having the same number of segments in the well-developed endopodite

as in the pereiopods. Because of the coalescence of the basipodite and ischio-

podite, the latter is immobile and no muscles pass into it from the basipodite.

Productor and reductor muscles have, however, been established in the ischio-

podite for the slight forward and backward movements of the meropodite,

and the arrangement of the whole system resembles that of other Decapoda.

productor propoditis

reductor propoditis

productor dactylopoditis

| eho b F

Sy, SK } reductor dactylopoditis

ESS

}

DS os

1\. adductor carpopoditis

A\\ \ abductor carpopoditis

\ productor meropoditis

ik Ne peductor meropoditis

adductor exopoditis

> depressor a

10 mm.

remotor b

Fic. 23. Muscles of left second maxilliped, dorsal view.

THE ANATOMY OF THE CAPE ROCK LOBSTER 87

Promotor

This relatively short but powerful dorsal muscle lies anteriorly in the

sternal muscle chamber. It apparently consists of two partly superimposed

bundles which have broad attachments on the anterior face of the paraphragm

and the endopleurite between the second and third thoracic segments and may

correspond to promotors a and 6 of the third maxillipeds and pereiopods. The

insertion takes place dorso-medially by a fairly long, flat tendon on the proximal

margin of the coxopodite, and contraction of the muscle directs the coxopodite

forward and inward.

Remotor (a, b)

Although narrower than the promotor, this muscle 1s clearly divisible into

two bundles which arise in the small pleural muscle chamber.

Remotor ais fairly robust and extends latero-dorsally from the endopleurite

near the epimeron. It is inserted ventro-laterally on the proximal margin of

the coxopodite by a fairly long tendon.

Remotor b is subequal in size to remotor a and is inserted with it, but passes

below it from a more ventral attachment on the endopleurite.

Levator (a, b)

The two heads of this muscle have separate origins, but are inserted dorso-

laterally on the proximal margin of the basipodite by a common, strong, flat

tendon; together they pull the basipodite outward about a slightly inclined

angle.

Levator a is fairly long, originates on the endopleurite below the lateral

fibres of the promotor muscle, and runs forward parallel to the remotor muscle.

Levator b is considerably shorter, passes somewhat obliquely forward from

a dorso-medial attachment on the proximal border of the coxopodite, and

becomes applied to levator a distally.

Depressor (a, 6)

Situated behind the promotor muscle in the sternal muscle chamber, this,

like the two previous muscles, is also distinctly bipartite.

Depressor a is a compound of three bundles, two of which arise medially

and laterally on the anterior face of the fairly large endosternite separating the

second and third thoracic segments, while the third is attached medially on

the proximal margin of the coxopodite. All three bundles are inserted ventro-

medially by a strong tendon on the proximal edge of the basipodite.

Depressor b is a smaller, single bundle that originates laterally in the coxopo-

dite. It passes inward beneath the levator muscles and becomes fixed to the

side of the tendon of depressor a. The two depressors are antagonistic to the

levator muscle and produce a downward and inward movement of the basi-

podite.

Productor meropoditis

The relatively long meropodite is moved forward by this rather small

88 ANNALS OF THE SOUTH AFRICAN MUSEUM

muscle, which is attached laterally in the ischiopodite and is inserted dorso-

laterally on the proximal margin of the meropodite by a short tendon.

Reductor meropoditis

This is proportionally broader and stronger than its antagonist, the pro-

ductor muscle of the meropodite. It arises dorso-medially in the ischiopodite

and narrows somewhat at its insertion by a short ventro-medial tendon on the

proximal edge of the meropodite.

Abductor carpopoditis

While the action of the meropodite is decidedly limited, the carpopodite

is freely movable and its two antagonistic muscles occupy a large part of the

meropodite.

The abductor muscle originates dorso-laterally in the proximal part of the

meropodite and is inserted laterally by a fairly long tendon on the proximal

border of the carpopodite.

Adductor carpopoditis

Attached ventro-laterally in the proximal part of the meropodite, this

equally strong, but flatter, muscle is inserted medially on the proximal edge of

the carpopodite by a strong tendon running down the length of its fibres.

Productor propoditis

From a wide area of attachment dorso- and ventro-laterally on the wall

of the carpopodite, this muscle narrows considerably towards its dorso-lateral

insertion by a broad, flat tendon on the proximal margin of the propodite;

it moves the latter forward.

Reductor propoditis

This rather smaller muscle occupies the medial half of the carpopodite,

along the ventro-medial wall of which it is attached. It is inserted ventro-

medially on the proximal border of the propodite by a narrow tendon.

Productor dactylopoditis

The terminal segment is pulled forward by this muscle which springs from

the dorso-lateral wall of the propodite and is inserted dorso-laterally by a

relatively long, flat tendon on the proximal margin of the dactylopodite.

Reductor dactylopoditis

This antagonist of the preceding muscle is slightly weaker, arises ventro-

medially in the propodite, and is inserted almost mid-ventrally on the proximal

edge of the dactylopodite by a relatively strong tendon.

Abductor exopoditis

The only muscles located in the basipodite are the two for moving the

exopodite, the rest of this segment being filled with connective tissue and blood.

The abductor muscle of the exopodite is attached medially in the basipodite

THE ANATOMY OF THE CAPE ROCK LOBSTER 89

and finds its insertion by a relatively long, flat tendon on the proximal

lateral border of the exopodite.

Adductor exopoditis

Lying close to the former muscle, this weaker one arises more ventrally

in the basipodite and, passing obliquely outward, is inserted by a short tendon

medially on the proximal margin of the exopodite. There is no corresponding

muscle in Astacus or Callinectes, but the latter has an attractor muscle for the

epipodite.

The remaining muscles, namely the abductor flagelli and the flagellar, are

similar to those of the first maxilliped.

(h) The third maxilliped (Fig. 24)

The third maxilliped is longer and more robust than the second maxilliped,

and has a closer resemblance to the pereiopods in the shape of its segments. As

in the second maxilliped, the carpopodite swings easily on the meropodite and

it and the two more distal segments can be flexed ventrally towards the mouth

and so directed that their heavily setose medial margins meet those of the

other third maxilliped in the mid-line. The exopodite is shorter than that of the

second maxilliped, but has similarly-arranged abductor and adductor muscles

and, as there is also a general agreement in the disposition and function of the

other parts of the system, brief comments only are given on some features of

the main muscles.

= Atel = Of pEOpOOli Us extensor dactylopoditis

flex on DnODO atts flexor dactylopoditis

productor carpopoditis

10 mm.

reductor carpopoditis

flagellar

A flexor meropoditis

abductor flagell'

levator b

levator ¢ adductor exopoditis

pe ee aucton exopoditis

levator

depressor b

| e i i depressor a

A\ ff YY promotor b

ig YP promotor a

LP remotor b

remotor a

Fic. 24. Muscles of left third maxilliped, dorsal view.

go ANNALS OF THE SOUTH AFRICAN MUSEUM

Promotor (a, 6, c)

As in the second maxilliped, this is a comparatively short but substantial

muscle which, however, is divisible into three heads having attachments

laterally on the endopleural invagination (promotor a), on the paraphragm

between the second and third thoracic segments (promotor b), and on the frontal

side of the mesophragm and the endosternite between the third and fourth

segments (promotor c, fig. 27). A broad, heavy tendon inserts it medio-dorsally

on the proximal border of the coxopodite.

Remotor (a, b)

At least two heads and possibly the makings of a third head may be dis-

tinguished in this muscle, which is again characteristically the most lateral of

the proximal muscles.

The large lateral bundle, remotor a, has a curved attachment high up on the

epimeron, but it also spreads on to the under surface of the shaft of the endo-

pleurite between the third and fourth segments; it is inserted ventro-laterally

on the proximal margin of the coxopodite by a long tendon which supports

the muscle and extends well into the pleural muscle chamber.

The more medio-ventral remotor b originates on the surface of the posterior

process of the endopleurite between the second and third epimera and is

inserted near the tendon of remotor a.

Levator (a, b, c)

The main branch, levator a, arises behind the promotor muscle on the

anterior face of the endosternite and endopleurite and is inserted dorso-

laterally on the proximal edge of the basipodite by a spatulate tendon.

Levator b is essentially similar to that of the second maxilliped and is

inserted by a short tendon medial to levator a.

Levator c consists of two superimposed parts which arise laterally and

ventro-laterally in the proximal region of the coxopodite and are inserted by

a short tendon adjacent to that of levator a.

Depressor (a, b)

Relative to the levator, this is a more powerful muscle, but its two main

heads resemble those of the second maxilliped.

Depressor a consists of at least four bundles, the attachments of which

spread over the proximal border of the coxopodite, the medial area of the

endosternite, the endopleurite, and the epimeron. Its dorso-lateral fibres

(fig. 27) overlap the remotor muscle in the pleural muscle chamber, obscuring

it in a medial view, while its shorter ventro-lateral slip extends from the anterior

face of the vertical plate of the endopleurite between the third and fourth

segments.

Depressor b arises laterally in the proximal part of the coxopodite, a small

spur-like projection of which separates it from levator c. It is inserted on a

slight ridge of the proximal margin of the basipodite adjoining the long, sabre-

like, ventro-lateral tendon of depressor a.

THE ANATOMY OF THE CAPE ROCK LOBSTER QI

Pilgrim & Wiersma’s (1963) observations on living Procambarus demonstrate

that the promotor and not the depressor muscles, as suggested by Schmidt

(1915), are mainly instrumental in bringing the medial edges of the basi-

podites and ischiopodites together when food is clasped between the two third

maxillipeds. The remotor muscles are evidently responsible for withdrawing

the appendages from the mid-line, but when they and the depressors contract

simultaneously the maxillipeds are said to retain their hold on the food.

Flexor meropoditis

As in Astacus and Callinectes, there is no extensor muscle of the meropodite,

and only one muscle, a relatively strong flexor, is developed for moving this

segment inward and upward. Originating proximally in and occupying the

medial half of the long ischiopodite, it is inserted dorso-medially by a long,

strong tendon on the proximal edge of the meropodite.

Each of the three distal segments of the endopodite is provided with two

antagonistic muscles, which differ slightly in function from the analogous

muscles of the second maxilliped. Thus, while the carpopodite is moved forward

and backward by a productor and a reductor muscle, the propodite and the dactyl-

opodite are operated by extensor and flexor muscles, which respectively produce

forward and outward and contrary backward and inward movements of the

segments. Although there is a functional similarity between these and the

corresponding six muscles of Astacus, some differences are evident in their

attachments and insertions. In Jasus (fig. 24) it may be noted that the extensor

muscles of the propodite and the dactylopodite originate ventro-laterally and

their flexors are dorsal; the tendinous insertions of the productor of the carpo=

podite and the extensors of the propodite and dactylopodite are lateral, as

opposed to the medial insertions of their antagonistic muscles. The reductor of

the carpopodite also differs from that of Astacus in being composed of short

dorso-medial and long ventral fibres, but this probably foreshadows the

arrangement in the pereiopods.

(i) The pereropods

The musculature of all five pairs of pereiopods is fairly uniform and, apart

from the absence of the exopodites and their associated muscles, the main

elements are almost identical with those of the third maxillipeds. Most of them

are inserted and supported by strong flat tendons (fig. 25), each of which usually

has a flexible attachment at some point on the proximal edge of a segment,

and may run through the middle of its particular muscle, receiving fibres at

intervals along its length.

(a) First pereiopod of the male (Fig. 26)

The muscles of the sturdy first pereiopod of the male, although somewhat

shorter and broader than those of the other pereiopods, may be used to illus-

trate the basic arrangement in any of the walking legs.

92 ANNALS OF THE SOUTH AFRICAN MUSEUM

Productor b propoditis abductor dactylopoditis

productor a propoditis adductor dactylopoditis

anterior joint dorsal joint anterior joint

ventral joint

membrane |

reductor propoditis

abductor carpopoditis

ventral joint

reductor b meropoditis

reductor a meropoditis

dorsal joint

anterior joint

levator c

Rema depressor b

levator a depressor a

dorsal joint——

ventral joint

: ences

remotor b a

remotor a

Fic. 25. Diagram of the tendons, some of the joints and intersegmental

arthrodial membranes of the left fourth pereiopod of male; in each

segment all but the proximal margin of the anterior (rostral)

surface has been removed.

Promotor (a, b, c)

Located rostrally in the sternal muscle chamber, the promotor muscle is

bulky and even more distinctly divisible into three heads than that of the third

maxilliped.

The fairly long lateral head, promotor a, arises on the shaft of the endo-

pleurite between the third and fourth epimera, and is obvious in sagittal view

(fig. 27) as it passes downward over the bifurcation of the endopleurite into its

anterior and posterior processes.

The rostral head, promotor b, is short and flat and is attached to the para-

phragm between the third and fourth segments.

The caudal head, promotor c, is more cylindrical and passes downward

from the mesophragm and the frontal face of the endosternite between the

fourth and fifth segments; its attachment is visible in an inner view (fig. 27) in

the region bounded by the mesophragms and the rostral and caudal para-

phragms of the fourth segment. The whole muscle is inserted rostrally by a

broad, flat, heavy tendon which projects from the proximal rim of the coxo-

podite, and contraction of the muscle pulls the leg forward.

THE ANATOMY OF THE CAPE ROCK LOBSTER 93

productor b propoditis

productor a propoditis

Bais) adductor dactylopoditis

abductor

carpopoditis

adductor a

carpopoditis

reductora

meropoditis

levator c

depressor b

y va il \\-remotor a

depressor a

remotor c remotor b

remotor a remotor ¢c

promotor a

remotor b

Fic. 26. Rostral views of muscles of first pereiopods of small male.

Remotor (a, 6, c)

While the remotor muscle of all the pereiopods in Pandalus and that of the

first four legs in Callinectes is apparently undivided, the arrangement in Fasus

is comparable to that of Astacus in which Schmidt (1915) distinguished three

distinct branches.

The main part of the muscle, remotor a, is a large leaf-shaped, almost

vertical bundle, with a dorso-lateral attachment on the epimeron of the fourth

segment.

Remotor b is fairly broad, but shorter than remotor a. It is located rostrally

in the pleural muscle chamber and arises somewhat ventrally on the outer face

of the vertical part of the posterior process of the endopleurite between the

third and fourth epimera.

Remotor c, which occurs between the other two heads, originates on the

under surface of the stem and the anterior process of the endopleurite projecting

from the junction of the fourth and fifth epimera. The fibres of all three parts

of the muscle are inserted caudo-laterally on the proximal border of the

94 ANNALS OF THE SOUTH AFRICAN MUSEUM

coxopodite, those of remotor a and remotor ¢ on a long flat tendon and those

of remotor 5 on a separate, small, adjacent tendon. In the last two pereiopods

the main remotor tendon (fig. 25) is usually broad and short, while in the

last pereiopod there is commonly no separate tendon for remotor bd.

Levator (a, 6, c)

The three divisions of this muscle are essentially similar to those of the

third maxillipeds, levators a and ¢ being conspicuous, while the much weaker

levator 6 arises rostrally on the proximal edge of the coxopodite and becomes

progressively more insignificant in posterior pereiopods.

The attachments of levator a are widely distributed on the anterior face

of the endosternite between the fourth and fifth segments and on the broad

vertical plate of the posterior process of the endopleurite that projects inward

between the third and fourth epimera and separates this muscle from those in

the pleural muscle chamber. It passes through the sternal muscle chamber

caudal to the promotor muscle, and in all the pereiopods is inserted rostro-

laterally on the proximal margin of the basipodite. As previously indicated,

(p. 36), it is by the excessive contraction of this muscle that autotomy of the

limb is effected.

Levator c is rather short and thick and, as in the third maxilliped, is divi-

sible into two bundles originating laterally and caudo-laterally in the proximal

part of the coxopodite near the root of its setiferous process. They are inserted

one above the other by short, separate tendons at the side of levator a on the

proximal edge of the basipodite. The whole levator muscle forms a powerful

element for elevating the basipodite and, with it, the whole appendage.

Depressor (a, b)

As in the second and third maxillipeds, this is one of the strongest and most

extensive of the extrinsic muscles of the pereiopod, but it is still fundamentally

bipartite.

Its main portion, depressor a, occupies most of the caudal half of the sternal

muscle chamber and has several subdivisions arising medially and laterally on

the proximal margin of the coxopodite, and ventrally behind levator a on the

rostral face of the endosternite between the fourth and fifth segments. In

addition, it invades the pleural muscle chamber: its dorso-lateral slip is attached

to the fourth epimeron and the under surface of the endopleurite stem between

the fourth and fifth epimera and covers the inner surface of the remotor muscle;

its ventro-lateral slip arises deep in the pleural muscle chamber on the anterior

face of the vertical plate of the endopleurite between the fourth and fifth

epimera and thus travels behind the remotor muscle. All its various bundles

collect on a strong bifurcated tendon projecting caudo-medially from the

proximal margin of the basipodite.

By comparison, depressor b is rather weak and short. It is attached caudo-

laterally in the coxopodite below levator c, and is inserted near the main

depressor on the proximal border of the basipodite by a very small tendon.

THE ANATOMY OF THE CAPE ROCK LOBSTER 95

Schmidt (1915) has indicated that in Astacus the depressor is the largest of

the protopodite muscles and is effective in raising the body when it pulls the

endopodite forcibly downward while the dactylopodite is in contact with the

substratum. In this connexion, the various joints of the segments also play an

important part in the complex movements of the limb during ambulation. The

action of the promotor and remotor muscles rotates the extended limb forward

and backward on the dorsal and ventral joints of the coxopodite. The leg is

bent between the carpopodite and the meropodite but, owing to the rigidity

of the latter, the fusion of the basipodite and ischiopodite, and the presence of

anterior and posterior joints on the basipodite, contraction of the levator and

depressor muscles also affects the limb as a whole.

Reductor (a, b) meropoditis

In both Astacus and Pandalus a reductor muscle of the ischiopodite has

been reported in all the pereiopods, but it is lacking in the cheliped of the

former, in which the basipodite and ischiopodite are fused. This muscle does

not occur in any of the pereiopods of Callinectes, and is also absent in Jasus.

In the latter the basipodite is filled with connective tissue, but a fairly complex

musculature for the movement of the meropodite occupies the relatively short

ischiopodite. Only reduction seems to be effected and, although the com-

ponents are inserted by a row of four tendons on the caudal proximal margin

of the meropodite, they may be considered to constitute two main muscles

comparable to the dorsal and ventral reductors of the meropodite of Astacus.

Reductor a is short and broad with two subequal heads, one arising caudo-

dorsally and the other caudo-ventrally in the ischiopodite. Both are inserted

caudo-dorsally on the proximal edge of the meropodite by a strong, flat tendon.

The stronger reductor b has a conspicuous, broad attachment rostro- and

caudo-ventrally, and superficially appears to form a compact muscle, but it

separates into three bundles which are inserted caudally by individual tendons

on the proximal margin of the meropodite. Of the three, the uppermost is

the largest and the ventral one the smallest.

Abductor carpopoditis

Lying rostro-dorsally, but also having some attachments distally in the

meropodite, this long, rather flat muscle is inserted dorsally by a narrow,

tapering tendon on the proximal border of the carpopodite. Its function is to

raise and extend the latter segment.

Adductor (a, b) carpopoditis

Relative to its antagonist, this muscle is larger and more powerful and,

as in Astacus, is divisible into two parts, the proportions of which, however,

seem to be reversed in the two species.

Adductor a is attached caudally along the length of the meropodite and

fills the caudal half of the segment. Supporting it is a broad, strong, horizontal

tendon from the mid-ventral proximal rim of the carpopodite.

96 ANNALS OF THE SOUTH AFRICAN MUSEUM

Adductor 6 is much weaker and adjoins the abductor of the carpopodite in

the distal half of the meropodite. It originates rostro-ventrally in the mero-

podite and is inserted in front of adductor a by a long, slender tendon.

Productor (a, b) propoditis

As in the preceding muscle, two heads may be recognized. The dense

fibres of productor a are attached practically along the whole rostral wall of the

carpopodite and are inserted rostrally about the middle of the proximal margin

of the propodite by a strong, flat, vertical tendon.

Productor b is inconspicuous and hardly distinguishable from the much

larger main productor of the propodite. It lies dorsally in the distal part of the

carpopodite and is inserted rostrally next to the other muscle by a small tendon.

Contraction of these muscles produces a forward movement of the propodite.

Reductor propoditis

Opposing the action of the productor of the propodite, this somewhat

smaller and flatter muscle is attached caudally in the carpopodite and is

inserted caudally on the middle of the proximal edge of the propodite by a

broad, almost horizontal tendon.

Abductor dactylopoditis

The fibres of this muscle spring mainly from the dorsal wall of the propo-

dite and insert mid-dorsally by a strong tendon on the proximal margin of the

dactylopodite.

Adductor dactylopoditis

This is the stronger of the two muscles of the terminal segment and

originates partly rostrally and partly caudally in the propodite. It has a very

broad, flat tendon for its ventral insertion on the proximal margin of the

dactylopodite. It serves to move the dactylopodite downward and inward, while

the abductor muscle has the opposite effect.

(b) Variation in attachments of muscles of posterior pereiopods

Although the intrinsic musculature of the segments of the endopodite is

consistently arranged in all the pereiopods, several modifications are apparent

in the attachments of the proximal muscles of the last three pereiopods. In

sagittal view (fig. 27) promotors a and ¢ are evident dorsally in the sternal muscle

chambers between the anterior and posterior paraphragms of the thoracic

segments. While the former usually occurs latero-dorsally with its fibres arising

near the inner anterior edge of the corresponding pleural muscle chamber,

promotor c is located more medially and caudally in the angle between the

mesophragm and the posterior paraphragm; it is also frequently divisible into

three bundles which, in the third maxilliped and first three pereiopods, pass

forward and downward towards their insertion. In the last pereiopod there is a

slight transposition of the lateral head of the promotor muscle, its attachment

being effected nearer the posterior rim of the pleural muscle chamber of the

THE ANATOMY OF THE CAPE ROCK LOBSTER 97

dep.a 1 dep.a 2 prom.a 4

dep.a mxpd III

prom.a mxopd III

prome mxpd III

prom.a 1

prom.c 1 prom.c 5

Fic. 27. Diagrammatic inner view of right half of endophragmal skeleton and proximal

muscles of right third maxilliped and right pereiopods; prom., promotor; rem., remotor;

dep., depressor muscle; numbers 1 to 5 are applicable to the muscles of the five pereiopods.

fourth pereiopod than the anterior border of the last pleural muscle chamber.

Promotor c of the last two pereiopods tends to be anterior to promotor a and is

directed obliquely backward and outward to the respective appendages.

The origins of the three heads of the remotor muscle are practically identical

in the first three pereiopods, but there is a gradual expansion and flattening of

remotors 5 and c from the second to the last pereiopod. Consequently, the large

remotor c of the fourth pereiopod arises partly on the caudal face of the para-

phragm and the endosternite between the seventh and the eighth segments

and is visible in a median view (fig. 27) in front of remotor a of the fourth

pereiopod and promotor c of the fifth pereiopod. The attachment of remotor ¢

of the last pereiopod is spread over a wide area of the caudal or upper face

of the posterior endosternite, medial to the corresponding remotor a. There is

also a tendency for the insertions of remotors 6 and c of the last two legs to

extend on to the proximal caudal margin of the coxopodite. Certain differences

are obvious between this arrangement and that described for Procambarus by

Pilgrim & Wiersma (1963), but these may be attributed to specific dissimilarities

of the skeletal framework and the movability of the eighth sternum in

Procambarus.

The disposition of the levator muscle is less variable, and its main head,

levator a, is hidden dorsally by promotor c.

The criticism levelled by Pilgrim & Wiersma (1963) against Schmidt’s

(1915) assumption that the lateral portion of depressor a of all the pereiopods

arises from the epimeron is supported by the present observations. It certainly

has this origin in the third maxilliped and in the first pereiopod, in each of

98 ANNALS OF THE SOUTH AFRICAN MUSEUM

which it is so large that it obscures remotor a. In the second pereiopod the

dorso-lateral slip of depressor a is also attached to the epimeron, but it is

reduced and passes between remotors a and c, partly covering the former.

From the third to the last pereiopod there is a progressive diminution of the

lateral section of depressor a and it is no longer seen in an inner view. That of

the third pereiopod is attached to the under surface of the strut of the endo-

pleurite between the sixth and seventh epimera and, as in the second pereiopod,

it travels between remotors a and c on its way to its insertion on the pereiopod.

Depressor a of the last two pereiopods does not appear in the pleural muscle

chamber and all its lateral fibres arise on the proximal margin of the coxopodite.

(j) The pleopods (Figs 28, 29)

Although the pleopod of the male differs from that of the female in being

uniramous and in having a proportionally smaller exopodite lamella, the

musculature is remarkably similar in both sexes. Moreover, the disposition of

the muscles in the four pairs of biramous female pleopods is fairly consistent, and

the only noticeable effect of the presence of the endopodite lamella in the first

pair (on the second abdominal segment) is the addition of a flagellar or lamellar

muscle. In the other three pairs of female pleopods the endopodite is a cylin-

drical, two-segmented rod which has a wide membranous connexion with

the medial expansion of the basipodite. In both sexes the coxopodite is incom-

plete ventrally and the basipodite and the exopodite lamella articulate by a

small ventral joint and are interconnected by a relatively wide arthrodial

membrane. The exopodite is not clearly differentiated from the broad exopodite

lamella and may be incomplete, but between the lamella and the basipodite

there is a dorso-lateral sclerotized area for the insertion of some of the muscles

of the exopodite. All the pleopods are attached to the abdominal sterna by

flexible membranes and are capable of rotation.

(a) Muscles common to the male and the female pleopods

The following is a general account of the musculature of any one of the

pleopods, excluding the muscles of the endopodite of the female. Perhaps owing

to the size of the lamellae, the system is more complex than that of either

Astacus or Pandalus with which, however, some similarities are evident.

Promotor

In Astacus Schmidt (1915) observed three proximal muscles which he

named the musculi remotor, rotator dorsalis basipoditis, and rotator ventralis

basipoditis. Analogous muscles occur in asus but, in addition, there is a

conspicuous promotor muscle, which arises dorso-laterally on the tergum in

proximity to the auxiliary muscle (figs 11, 12) and is more powerful in the

female than in the male. It is obviously separated into a more or less cylindrical

anterior head and a broader, flatter, more posterior portion consisting of two

bands of widely spread fibres. The whole narrows somewhat towards its dorso-

lateral insertion by a fairly strong tendon on the proximal margin of the

coxopodite, and on contraction pulls the appendage forward.

THE ANATOMY OF THE CAPE ROCK LOBSTER 99

: remotor

adductor basipoditis (

ventral rotator k

hail Wi hae romotor

reductor exopoditis se TT / : :

ad AL | ft

adductor exopoditis dorsal rotator

abductor exopoditis abductor basipod.

flagellaris exopoditis

Praductor exopod.

a Se abductor flagelli

[ SSSe UTA eae exopoditis

los

{3 adductor flagelli

ia exopoditis

Fic. 28. Ventral view of muscles of left third pleopod of male.

Remotor

Backward movement of the pleopod is effected by this muscle, which

differs in the two sexes, being slender in the male but comparatively wide and

composed of three bundles in the female appendage. In both sexes it is ventral

to the promotor muscle, and is attached antero-laterally on the pleuron and

inserted ventrally by a short tendon on the proximal border of the coxopodite.

Dorsal rotator

This is a thick band, divisible into upper and lower bundles which ori-

ginate postero-laterally on the tergum behind the promotor muscle. It slants

obliquely inward dorsal to the remotor muscle and, traversing the coxopodite,

is inserted ventrally on the middle of the proximal border of the basipodite by

a conspicuous, flat tendon. It is comparable to the musculus rotator dorsalis

basipoditis of Astacus and Pandalus, but differs in having a ventral and not a

dorsal insertion.

Ventral rotator

Arising at the anterior junction of the sternum and pleuron, this muscle

tapers rapidly towards its medial insertion by a slender tendon on the proximal

edge of the basipodite. In the male pleopod it is feebly developed and consists

of only a few fibres, but in the female there is an additional, more substantial

bundle that practically obscures the weaker element ventrally. The two rotator

muscles probably correspond to the levator and depressor muscles of the

thoracic appendages, and are functionally antagonistic, the dorsal one turning

the appendage outward and forward and the ventral one pulling it inward and

forward.

Abductor basipoditis

Some specific variation is apparent in the number of remaining muscles

associated with the basipodite. In Astacus there is a single reductor of the basi-

100 ANNALS OF THE SOUTH AFRICAN MUSEUM

podite, but Pandalus also has a productor and an adductor of this segment.

Two muscles, considered to be an abductor and an adductor, are concerned

respectively with further outward and inward movements of the basipodite of

Jasus.

The origin of the long, narrow abductor basipoditis takes place medio-

dorsally on the proximal border of the coxopodite, through which it runs

obliquely outward to a lateral insertion in the basipodite.

Adductor basipoditis

Lying approximately parallel to the medial margin of the coxopodite and

dorsal to the ventral rotator muscle, this much shorter unit is attached near the

abductor of the basipodite and extends medio-ventrally to the proximal

margin of the basipodite near the insertion of the dorsal rotator muscle.

Productor exopoditis

Crowded into the short basipodite are four muscles, which are responsible

for the movements of the narrow basal part of the exopodite and are distinct

from those of the broad lamella. The productor muscle occupies the dorso-lateral

half of the basipodite and moves the exopodite forward. It is usually divisible

into two bands stretching between the proximal margins of the basipodite and

the exopodite, but an additional bundle may occur in the larger pleopods of

the female.

Reductor exopoditis

Like the previous muscle, this is also bipartite or tripartite, its somewhat

thicker bundles arising side by side ventrally on the proximal border of the

basipodite. They insert ventrally on the proximal margin of the exopodite and

oppose the action of the corresponding productor muscle.

Abductor exopoditis

There appear to be more muscles associated with the exopodite of the

pleopod than in other Decapoda previously investigated. The productor and

reductor muscles have not been reported in Astacus and Pandalus and, while

the former has no adductor muscle, the exopodite of the latter resembles that

of Fasus in being provided with antagonistic abductor and adductor muscles.

Arising dorso-medially in the basipodite, the fairly thick and relatively

long abductor muscle of the exopodite passes outward and backward between

the productor and reductor muscles of the exopodite. It is inserted laterally

in the exopodite and serves to tilt it and the broad lamella outward.

Adductor exopoditis

This shorter muscle has a wide attachment medio-ventrally in the basi-

podite, but tapers acutely before being inserted medially by a slender tendon

on the proximal edge of the exopodite.

Abductor flagelli exopoditis

As the flat, unsegmented lamella of the exopodite is analogous to the

flagellum of the three maxillipeds, the terminology applied to the musculature

THE ANATOMY OF THE CAPE ROCK LOBSTER IOI

of the latter may be repeated in describing the remaining muscles of the pleo-

pod. Abduction and adduction of the lamella, however, are effected by muscles

which have no homologues in either Astacus or Pandalus.

The exopodite lamella is moved forward and outward by a very small

abductor flagelli exopoditis, which is attached laterally in the exopodite ventral

to the insertion of the abductor exopoditis. It tapers rapidly towards its dorsal

insertion by a strong tendon in the middle of the proximal region of the lamella.

Adductor flagelli exopoditis

Inward movement of the exopodite lamella is accomplished by this rather

thicker and more obvious muscle, which arises dorsally in the exopodite and

spreads out ventro-laterally in the proximal part of the lamella.

Flagellaris exopoditis

In both sexes the thin exopodite lamella is provided with a number of

strong fibres which are attached dorsally at its proximal margin. They fan out

into the medial part of the lamella and cause it to bend in various directions.

(b) Additional muscles in the female pleopod

The endopodite is a conspicuous ramus of the female pleopod and its

movements are produced by several intrinsic muscles, all of which are repeti-

tions of the musculature of the exopodite.

adductor basipoditis remotor

ventral rotator

reductor endopoditis

adductor exopoditis

abductor endopoditis

abductor flagelli ss

endopoditis

adductor flagel|i

reductor exopod.

endopoditis

aA productor exopod.

appendix interna

abductor exopoditis

abductor flagelli

exopoditis

adductor flagelli

flagellaris exopoditis

endopoditis i ;

flagellaris exopoditis

5 mm.

Fic. 29. Ventral view of muscles of left first pleopod of female.

Productor and reductor endopoditis

The connexion between the basipodite and the endopodite is largely

membranous, but obvious medial bundles in line with the productor and

102 ANNALS OF THE SOUTH AFRICAN MUSEUM

reductor muscles of the exopodite appear to be inserted more particularly on

the endopodite and may be distinguished as elements contributing to its for-

ward and backward movements.

Abductor and adductor endopoditis

Located in the lower, outer angle of the endopodite are probable abductor

and adductor muscles of the endopodite, which are weakly developed in the

first pleopod, but are more apparent in the other three pleopods. They arise

dorsally on the distal margin of the basipodite near the corresponding muscles

of the exopodite and spread out slightly along the lower proximal wall of the

endopodite, the abductor muscle being ventral to the adductor at its attach-

ment and insertion; the adductor muscle has been omitted in figure 29.

Abductor and adductor flagelli endopoditis

The large inner lamella of the first pleopod of the female is provided with

two subequal antagonistic muscles that are more conspicuous than those of the

exopodite lamella. They are attached dorsally one above the other at the

junction of the basipodite and the endopodite and proceed close together

through the basal segment of the endopodite, but are distinguished from each

other by the fact that the abductor has a ventral and the adductor a dorsal

insertion on the proximal edge of the lamella.

Although the endopodite lamella is lacking in the remaining female

pleopods, these muscles are retained. The abductor, however, is foreshortened

and inserted proximally in the basal segment, while the adductor muscle

extends to the distal region of the segment in line with the appendix interna.

Flagellaris endopoditis

The intrinsic muscle of the endopodite lamella of the first pleopod of the

female resembles that in the exopodite lamella, but it is rather smaller and

situated more in the middle of the lamella. It is, of course, non-existent in

the other three pleopods of the female.

(k) The uropod (Fig. 30)

The last pair of abdominal appendages differs from the pleopods in being

larger and biramous in both sexes and, although the coxopodite and basipodite

are fused, thin arthrodial membranes allow of easy rotation of the undifferen-

tiated protopodite and its appended flat, foliaceous exopodite and endopodite.

The overall plan of the musculature is practically identical with that of Astacus

and Pandalus and, as in these species, the muscles of the protopodite and exopo-

dite are well developed and intricately arranged.

Lateral remotor of uropod

Located dorso-laterally and partly overlapping the last janelle muscle,

this broad, fan-shaped muscle is composed of several bundles attached dorso-

laterally behind the hinge near the proximal margin of the sixth abdominal

segment. As it passes posteriorly, it narrows appreciably and is inserted dorso-

THE ANATOMY OF THE CAPE ROCK LOBSTER 103

ventral rotator uropod

dorsal rotator uropod

lateral remotor uropod

anterior telso-uropedal

anal compressor lateral telso-uropedal

posterior telso-uropedal

medial remotor uropod dorsal abductor exopod.

— ventral abductor exopod.

—S

ee abductor exopod.

anal compressor ——]) WR 8 | = SS = productor exopod.

ant. flexor telson

reductor exopod.

anal dilatator adductor exopod.

adductor, endopod |

post. flexor telson |

exopodite

ventral flexor telson endopodite

telson

20 mm. J

Fic. 30. Dorsal view of muscles of right uropod and right half of telson.

laterally on the proximal border of the protopodite by a broad, flat tendon,

and effects a backward or upward movement of the appendage.

Medial remotor of uropod

The two contiguous bundles of this muscle arise dorso-medially in the

posterior half of the sixth abdominal segment, and are separated from the

lateral remotor by auxiliary muscle 5. The whole muscle lies superficially

above the segmental extensor muscles and runs transversely across the segment

to insert on the same tendon as the lateral remotor, to which it is similar in

function, but also serves partly as an abductor.

Dorsal rotator of uropod

Apart from a narrow anterior slip arising in front of the medial remotor

muscle above the extensor muscles of the sixth abdominal segment, this strong

element originates mid-dorsally on the sixth abdominal tergum in the gap

between the right and left extensor muscles. It slopes ventro-laterally below

the latter and narrows rapidly towards its medio-ventral insertion by a very

distinct, slightly curved tendon on the proximal edge of the protopodite. It

pulls the uropod ventrally and thus turns it forward and inward.

Ventral rotator of uropod

On the whole, this broad, rather flat muscle is about equal in strength to

the dorsal rotator of the uropod, and is situated beneath the lateral remotor of

104 ANNALS OF THE SOUTH AFRICAN MUSEUM

the uropod and auxiliary muscle 5. It is attached yentrally near the anterior

border of the sixth abdominal segment and is inserted antero-ventrally on the

tendon of the dorsal rotator of the uropod, but also spreads on to the adjacent

tendon of the last anterior oblique muscle.

Abductors of exopodite

The expansion of the uropod to form the tail-fan is assisted by three

muscles, which occupy the lateral parts of the protopodite and correspond to

the lateral, dorsal, and ventral abductors of the exopodite in Schmidt’s (1915)

account of the musculature of Astacus.

The most conspicuous of the three is the long lateral abductor, which arises

dorso-laterally on the proximal edge of the protopodite and extends through

the latter to insert ventro-laterally in the exopodite some distance from its

proximal border.

The dorsal abductor of the uropod is medial to and much shorter than the

lateral abductor and, as in Astacus, is composed of two parts. In addition to a

weak, narrow, dorso-lateral band, there is a thicker bundle arising ventro-

laterally in the proximal region of the protopodite, so that it practically

embraces the attachment of the lateral abductor of the exopodite. All its fibres

congregate at a relatively wide insertion medio-dorsal to the lateral abductor

muscle on the proximal margin of the exopodite.

The lateral abductor overlies the small ventral abductor of the exopodite

both at its ventro-lateral origin on the proximal margin of the protopodite and

at its ventro-lateral insertion on the proximal edge of the exopodite.

Adductor of exopodite

This is the only muscle that directly opposes the abductors of the exopodite

and lessens the width of the tail-fan. It is attached ventrally in the distal part of

the protopodite and curves into the exopodite parallel to the lateral abductor

muscle, medial to which it has a broad, dorsal insertion.

Productor of exopodite

Arising dorsally by a broad surface in the proximal half of the protopodite,

this fairly substantial muscle narrows appreciably as it bends round the outer

margin of the adductor of the exopodite and passes to a thin ventral tendon

located just beyond the proximal border of the exopodite. It pulls the latter

forward in a ventral direction.

Reductor of exopodite

The origin of this somewhat shorter and weaker muscle is posterior to the

previous muscle and dorsal to the adductor of the exopodite. It passes dorso-

laterally over the latter and is inserted dorsally without a tendon near the

proximal edge of the exopodite.

Adductor of the endopodite

As in Astacus and Pandalus, the endopodite has no abductor muscle, there

being only a rather weak adductor, which causes an inward movement of the

THE ANATOMY OF THE CAPE ROCK LOBSTER 105

endopodite. It is attached dorso-medially in the protopodite in line with the

productor muscle of the exopodite, and is inserted ventro-medially on the

proximal margin of the endopodite.

Telso-uropedal

This muscle agrees with that of Astacus in originating by a broad surface

dorso-laterally near the proximal border of the telson and in being divisible

into three parts.

The anterior head is narrow and passes from the antero-lateral corner of the

telson into the proximal part of the protopodite where it is inserted medio-

ventrally on the posterior edge of the tendon of the dorsal rotator muscle of

the uropod.

Slightly broader than the former, the Jateral head is inserted laterally in

the proximal region of the protopodite near the dorsal abductor of the exopodite.

The strongest of the three is the posterior head, which passes below the other

two bundles and inserts medio-ventrally in the protopodite opposite the

productor muscle of the exopodite.

Although the telso-uropedal muscle originates dorso-laterally in the telson,

some of the fibres of the lateral and posterior bundles are connected by fibrous

material with the tendon of the last anterior oblique muscle. By contributing

to the outward and forward or ventral orientation of the uropod, the entire

muscle is complementary to some of the other muscles in effecting movements

of the tail-fan.

D. ALIMENTARY TRACT

In common with the majority of free-living triploblastic Invertebrata, the

alimentary tract, which is a straight tube, may be differentiated into three

regions, the stomodaeum, the mesenteron, and the proctodaeum.

The stomodaeum or fore-gut is lied with epicuticle (Dennell, 1960) and

consists of a short oesophagus (figs 32, 33) extending vertically upward from the

antero-ventral mouth (figs 4, 31), and a large proventriculus (figs 10, 31, 77, 78)

which occupies the greater portion of the anterior part of the body cavity.

Following the nomenclature used by Pearson (1908), the proventriculus may

be divided into a large, almost spherical, flat-roofed cardiac fore-gut and a smaller

pyloric fore-gut, in the latter of which anterior and posterior regions are recog- —

nizable. The inner wall of the proventriculus is furnished with a number of

strong teeth which constitute the so-called ‘gastric mill’ for grinding the food;

it also has groups of setae which form a filtering apparatus for straining the

food and ensuring that only the finest particles and liquids are passed back

into the mid-gut.

The mesenteron or mid-gut (figs 32-34) is a short, soft-walled chamber, the

epithelium of which is endodermal in origin and absorptive in function.

Opening into it on each side is the duct from the large, paired digestive gland

(figs 10, 31, 77, 78), while postero-dorsally it gives off a short, inconspicuous,

106 ANNALS OF THE SOUTH AFRICAN MUSEUM

left antennule

epistoma

labrum left antenna

right mandible

antennulary nerve

right 3rd maxilliped

ist pereiopod AR ey

cid mouth

2nd maxilliped

antennary nerve

cerebral ganglion

optic nerve

proventriculus

anterior gastric muscle

il Oesophageal ganglion

AT —pa roesophageal ganglion

posterior gastric muscles

paragnath

i of hepatic duct

ist maxilliped opening Of hepatic du

Ophthalmic artery

ventral thoracic artery antennary artery

f = "

digestive gland ; aut

sternal canal A Z ostium

endophragmal skeleton 4 i Ovary

sternum Al hind-gut

sternal artery

muscular artery Superficial extensor muscles

ist abdominal ganglion

intersternal membrane

ventral nerve cord

deeper extensor muscles

intertergal membrane

ventral abdominal artery fj

anterior oblique muscles dorsal abdominal artery

transverse muscle

pleopods

6th abdominal ganglion

20 mm.

anus

telson

Fic. 31. General anatomy of small female, dissected from the left.

THE ANATOMY OF THE CAPE ROCK LOBSTER 107

forwardly-directed caecum (figs 33, 37) which is closely adherent to the dorsal

wall of the posterior part of the pyloric fore-gut.

The proctodaeum, intestine, or hind-gut (figs 31-34, 77, 78) is the longest part of

the alimentary tract and, like the fore-gut, is lined with epicuticle. It is a

straight narrow tube which lies beneath the pericardial cavity in the cephalo-

thorax and extends down the length of the abdomen below the extensor

muscles to open at the slit-like anus (fig. 31) located ventrally on the telson.

I. OSSICLES AND TEETH OF THE PROVENTRICULUS (Figs 32-34)

The cardiac and pyloric chambers of the fore-gut differ not only in relative

size, but also in that, whereas the wall of the former serves as an internal

masticatory ‘gastric mill’, the latter functions chiefly as a filtering or sieving

mechanism; consequently the structural modifications in each region are

considerable.

(a) Cardiac fore-gut

While this is relatively thin-walled laterally and ventrally, it is supported

dorsally and dorso-laterally by a number of ossicles, which are thickenings of

its cuticular lining. The ossicles not only provide attachment for the extrinsic

and the intrinsic muscles of the fore-gut, but certain of them are produced into

conspicuous teeth which form the grinding apparatus for triturating the food.

The various structures of the cardiac fore-gut are distributed much as are those

of other Reptantia described by Pearson (1908) and Patwardhan (1935).

cardiac ossicle urocardiac ossicle

median tooth

pterocardiac ossicle Zygocardiac ossicle

antero-lateral pad

cardiac plate prepectineal ossicle

exopyloric ossicle

pyloric ossicle

oesophagus postpectineal ossicle

pectined! oOssicle

postero-lateral

cardiac plate

~~ Rael s 6 S 7 ‘J

a igs

cardio-pyloric valve

infero-lateral cardiac ossicle

ventral groove

lateral cardio-pyloric ossicle

antero-inferior pyloric ossicle

anterior supra-ampullary ossicle

lateral pyloric ossicle

1/2 ventral valve posterior supra-ampullary ossicle

lateral valve Blea mid-gut

dorsal valve AL ABE hind-gut

[ean BWOle

Fic. 32. Inner view of fore-gut, cut mid-ventrally to expose the ossicles, teeth, valves, etc.

108 ANNALS OF THE SOUTH AFRICAN MUSEUM

The postero-lateral walls are strengthened by a pair of conspicuous, more

or less semicircular postero-lateral cardiac plates (figs 32-34). The surface of each

is provided with several rows of setae which project into the lumen.

In front of these areas there is a pair of ill-defined antero-lateral cardiac

plates (figs 32, 34); these are more membranous and are not setose.

The cardiac ossicle (figs 32-34) is a fairly large, dorso-median, roughly

triangular piece with an indented posterior margin and a slight, outer, postero-

median ridge for the insertion of the anterior gastric muscles.

Zygocardiac ossicle

i urocardiac ossicle / prepyloric ossicle

\O i i i icle

[2 cardiac ossicle : pyloric ossic

3 TT SS median tooth

3 prepectineal ossicle ME uy Aapaullenceuns

| Jf —\

Wf ss

He 1/2 dorsal valve

lateral tooth

accessory lateral tooth

postero- lateral

cardiac plate

cardio-pyloric valve te

\ : ss lateral valve

fe} h SSNS :

esophagu Ey ampulla mid-gut

hepatic duct 1/2 ventral valve

Fic. 33. Median view of fore-gut.

The pterocardiac ossicles (figs 32, 34) are paired, rather small, slender,

lateral sclerites articulating with the postero-lateral border of the cardiac

ossicle and extending inward towards its postero-lateral notch.

The greater part of the roof of the cardiac fore-gut is formed by the flat

urocardiac ossicle (figs 32-34). It is broadest anteriorly at its articulation with the

cardiac and the pterocardiac ossicles and narrows perceptibly at its posterior

extremity, where it is continued into a downwardly-directed, forwardly-

Prepectineal oOssicle

accessory lateral tooth

(on pectineal ossicle) pterocardiac ossicle

ossicle

>) urocardiac ossicle

Y zygocardiac ossicle

exopyloric ossicle

fe tooth

postpectineal ossicle

infero-lateral cardiac ossicles

antero-lateral cardiac plate K

postero-lateral cardiac plate > i S

ventral groove = 4

Subdentary oss

lateral cardio-pyloric ossicle

feri > = PENS } >

antero-inferior Pyloric ossicle ; AW ar, mesopylonia oaerele

anterior Ssupra-amPpu press

ampullary ossi

ampulia or gian

dorsal valve

supra- ampulla lateral valves E

inter-ampullary mid-gut

hind-gut =

Fic. 34. Plan of inner view of fore-gut, spread out after lateral incision.

THE ANATOMY OF THE CAPE ROCK LOBSTER 109

curved, brownish and slightly bifid median tooth (figs 32-34). In the posterior

two-thirds of the ossicle the lateral margins are marked by a series of blunt,

transverse ridges.

Paired, thickly-sclerotized zygocardiac ossicles (figs 32-34) occur dorso-

laterally and articulate anteriorly with the outer ends of the pterocardiac

ossicles. Each arches backward and downward and tapers anteriorly and

posteriorly; at its widest point it supports a large, blunt denticle which curves

inward towards the median tooth. In addition, there are about 21 acutely-

pointed smaller denticles along the lateral border of the posterior half of the

zygocardiac ossicle; these decrease progressively in size from the large denticle

backward and, combined with the latter, constitute the lateral tooth (figs 33, 34).

The exopyloric ossicles (figs 32, 34.) are a pair of small, somewhat rectangular

plates, which are intercalated between the posterior part of the zygocardiac

ossicle and the pyloric ossicle and virtually lie between the cardiac and pyloric

portions of the fore-gut.

Located in the wall of the cardiac fore-gut lateral to the large denticle

on the zygocardiac ossicle and at the inner end of the curvature of the postero-

lateral cardiac plate is a small, rather inconspicuous, paired pectineal ossicle

(fig. 32). It is characterized by the presence of a minute, hooked, backwardly-

directed accessory lateral tooth (figs 33, 34).

The prepectineal ossicles (figs 32-34) are long, narrow, curved rods Och

lie parallel to the outer edge of the zygocardiac ossicles and extend forward

from the pectineal ossicles to the outer ends of the pterocardiac ossicles.

Two slender fpostpectineal ossicles (figs 32, 34) run backward from the

pectineal ossicles round the posterior margin of the postero-lateral cardiac

plates in the direction of the oesophagus.

The infero-lateral cardiac ossicles (figs 32, 34) are also thin, arched bars,

which lie behind and parallel to the postpectineal ossicles but, unlike the latter,

they are fringed with setae and each forms the anterior boundary of a paired

ventral food groove (figs 32, 34) leading from the oesophagus to the pyloric

fore-gut.

On each side a narrow, slightly bent subdentary ossicle (fig. 34.) passes from

the large denticle on the zygocardiac ossicle to the upper end of the infero-

lateral cardiac ossicle with which it is loosely articulated.

Paired, short, curved lateral cardio-pyloric ossicles (figs 32, 34) extend from

the posterior ends of the infero-lateral cardiac ossicles below the cardio-pyloric

valve into the ventro-lateral part of the pyloric fore-gut.

The side-wall of the cardiac fore-gut is provided with three fairly con-

spicuous fads or cushions, the surfaces of which are beset with short setae. One

is an anterior, elongate-oval swelling between the zygocardiac and prepectineal

ossicles (fig. 32), and the other two are more posterior and are located on either

side of the subdentary ossicle. According to Yonge (1924), similar pads in the

cardiac fore-gut of Nephrops norvegicus guard the entrance into the pyloric fore-

gut.

110 ANNALS OF THE SOUTH AFRICAN MUSEUM

(b) Pyloric fore-gut

This somewhat bent posterior part of the proventriculus, although possess-

ing fewer ossicles, is structurally just as complex as the cardiac fore-gut. Con-

tinuous with the latter is a thin-walled, antero-dorsal pyloric chamber, while

postero-ventrally the second half of the pyloric fore-gut communicates with the

extremely short mid-gut and leads almost directly to the hind-gut.

(i) Anterior part of pyloric fore-gut

Two main median ossicles, the prepyloric and the pyloric, occur in this

region: the prepyloric ossicle (fig. 33) is a small, triangular, vertical plate, extend-

ing upward from the posterior end of the urocardiac ossicle to join the pyloric

ossicle. The latter (figs 32, 33) forms the arched, thin-walled roof of this chamber,

and articulates with the prepyloric ossicle anteriorly and with the exopyloric

ossicles more laterally.

In addition to the above two ossicles, the narrow ventral wall is supported

by a small antero-inferior pyloric ossicle (figs 32, 34). This is a median, somewhat

triangular plate, lying immediately behind the cardio-pyloric valve and

flanked on each side by a short, rod-shaped pre-ampullary ossicle, which is

represented but not labelled in figure 34.

(ii) Posterior part of pyloric fore-gut

This is rather more compact than the anterior part and, owing to the

intricate arrangement of plates, valves and other structures, its lumen is much

smaller. Its most striking feature is the presence of a pair of- ventro-lateral

pockets, each of which contains a remarkable semicircular organ, termed the

pyloric ampulla by Pearson (1908) and the gland filter by Yonge (1924). Each

ampulla (figs 32-34, 36) consists essentially of a thick, ventro-lateral, concave,

plate, which is internally produced into parallel, longitudinal, cuticular rods,

capped with setae. The two ampullae meet mid-ventrally in an obvious

sloping inter-ampullary ridge (figs 34, 36, 37), which lies behind the antero-

inferior pyloric ossicle and projects upward into the very narrow lumen, its

summit being furnished with two parallel rows of setae. Fitting into the con-

cavity of the ampulla is a pronounced, convex supra-ampullary ridge (figs 34, 36),

the dense setose covering of which forms part of the filtering apparatus.

Immediately in front of each supra-ampullary ridge is a short, rod-shaped

anterior supra-ampullary ossicle (figs 32, 34), which supports the wall between the

ridge and the lateral cardio-pyloric ossicle.

In the vicinity of the supra-ampullary ridge, there is also at least another

short bar, the posterior supra-ampullary ossicle (figs 32, 34.), which partly embraces

the opening of the hepatic duct in the anterior region of the mid-gut.

Each lateral wall is occupied by a flat, relatively broad plate, partially

covered with setae; the two plates have been identified as the ress (figs 32, 34,

36, 37), as they are comparable to the structure so described by Yonge (1924)

in his account of the fore-gut of Nephrops norvegicus. The anterior margin of each

THE ANATOMY OF THE CAPE ROCK LOBSTER 1hAUBL

half of the press is strengthened by a narrow, transverse bar, which extends

almost to the posterior extremity of the subdentary ossicle, and may con-

veniently be termed the Jateral pyloric ossicle (figs 32, 34). Articulating with the

latter is another, paired, horizontal rod, the mesopyloric ossicle (fig. 34), which

seems to be the only obvious support of the dorsal wall and may correspond to

the paired posterior mesopyloric ossicle of crabs (Pearson, 1908; Patwardhan,

1935).

The arrangement of most of the aforementioned proventricular structures

broadly reflects the findings of Pearson (1908), Yonge (1924), and Patwardhan

(1935) in other Decapoda. Pearson, however, has mentioned several additional,

small, supporting ossicles in the lateral walls of the pyloric fore-gut of Cancer;

although these have not been detected in Jasus, it is possible that some of them

have been replaced by the press.

2. PROVENTRICULAR VALVES (Figs 32-34, 37)

In addition to ossicles and teeth, the proventriculus is equipped with five

conspicuous valves whose main function is to guide food particles along definite

channels, but some of them may also act as a protection for the soft-walled

mid-gut.

The cardiac and pyloric regions of the proventriculus are incompletely

separated by a relatively large cardio-pyloric valve. This is a thickened infolding

of the postero-ventral wall of the cardiac fore-gut and, like many other parts

of the inner lining of the proventriculus, it is fringed with closely-set setae. It

lies in proximity to the two posterior pairs of cardiac pads and, forming a spout-

like projection in front of the press, it partly obstructs the entrance into the

posterior half of the pyloric fore-gut.

Extending from the posterior division of the pyloric fore-gut into the lumen

of the mid-gut are the following four cuticular, flat, setose valves: the dorsal

valve is a tongue-shaped flap attached to the medial ends of the mesopyloric

ossicles; a similar, but slightly smaller, ventral valve is continuous with the

ampullary region; and two elongate lateral valves pass back from the press. As

Pearson (1908) has remarked, these four valves may serve as a protective

lining for the very short mid-gut, ensuring the direct passage of hard particles

from the fore-gut into the hind-gut and guarding the delicate epithelium of

the mid-gut against injury. Yonge (1924), however, has indicated that this

function cannot be realized in Nephrops norvegicus which has a relatively long

mid-gut. He has therefore suggested that the valves and the filter apparatus

ensure that only liquids and fine food particles will enter the hepatopancreas

and, from an examination of their disposition in Jasus, it seems likely that they

may also be partly adapted for this purpose in decapods with an extremely

short mid-gut.

3. MUSCLES OF THE FORE-GUT (Fig. 35)

The several parts of the fore-gut are dilated and constricted by a compli-

cated musculature which, as in Cancer pagurus (Pearson, 1908) and in Paratel-

en? ANNALS OF THE SOUTH AFRICAN MUSEUM

phusa guerim (Patwardhan, 1935), may be divided into two main categories.

The extrinsic muscles are those which originate outside the fore-gut, generally

on different parts of the exoskeleton; most of them are inserted on the ossicles

of the fore-gut and serve to dilate its parts. On the other hand, the znérinsic

muscles function as constrictors and usually have their attachments and inser-

tions on the proventricular ossicles; it has been shown by Manton (1928, 1934)

that many of the intrinsic muscles are derived from the preantennulary meso-

derm. The arrangement of the muscles in 7. lalandii closely resembles that of

Cancer and Paratelphusa, and the terminology used in the following account is in

accordance with that of Pearson (1908).

lateral cardio-pyloric inner posterior gastric

median cardio-pyloric outer posterior gastrics

ant. & post. dorsal pyloric

dilators

anterior gastric

: EX

upper ant. dilator of fore-gut yp \

; Sa } i l

antero-lateral cardiac

anterior cardiac lateral pylorics

20 mm.

; lateral cardiacs

antero-lateral dilators of fore-gut i ae REA 5

postero-inferior cardiac

lower anterior dilators of fore-gut ventral pyloric dilator

posterior dilator of fore-gut

upper anterior Oesophageal! dilator

Ee Eee postero-lateral dilator of fore-gut

Ueienall) cre relrivertsell chikeiey posterior oesophageal dilator

lower anterior oesophagedl dilator oesophageal! constrictors

Fic. 35. Left lateral view of fore-gut, showing position of muscles; intrinsic muscles are underlined.

(a) Extrinsic muscles

Anterior gastrics: one pair of broad muscles attached to the procephalic

processes. Each passes somewhat obliquely backward and is inserted on the

posterior half of the cardiac ossicle. As some of the fibres are inserted on the

median ridge of the cardiac ossicle, there is only a slight gap between the

posterior ends of the two muscles.

Posterior gastrics. These comprise one pair of inner and two pairs of outer

muscles, all of which arise posteriorly on the gastric region of the wall of the

head. The inner posterior gastrics are attached close together near the mid-dorsal

line and medial to the posterior bundle of the mandibular posterior adductor

muscle. Each is inserted on an antero-lateral ridge of the pyloric ossicle, just

behind the margin of the prepyloric ossicle. The outer posterior gastrics arise

more laterally on the head wall and pass obliquely forward and inward between

the two bundles of the mandibular posterior adductor muscle. On each side

the two muscles are contiguous and are inserted on the exopyloric ossicle, one

above the other.

THE ANATOMY OF THE CAPE ROCK LOBSTER 113

Upper anterior dilators—one pair. These are not compact muscles, each

being composed of a number of separate strands, which arise close together

on the ventro-lateral surface of the procephalic process beneath the anterior

gastric muscle. The muscle strands diverge as they pass backward, inward and

downward, and are inserted separately on the anterior and antero-lateral wall

of the upper part of the cardiac fore-gut.

Lower anterior dilators: one pair, each of which consists of long, thin strands,

and the whole is subequal in size to the upper anterior dilator muscle. The

fibres originate on the median apodeme of the epistoma and spread to each side

of the ventral antero-median wall of the cardiac fore-gut.

Antero-lateral dilators. In Cancer Pearson (1908) has described a single pair

of narrow compact muscles, but in Jasus there appear to be two pairs, one above

the other. They are attached near each other on the mandibular epimeron in

the prebranchial chamber close to the lateral margin of the epistoma. They

consist of long, slender muscle strands inserted on the lateral wall of the cardiac

fore-gut in the region of the antero-lateral cardiac plate. ‘The lower muscle is

the smaller of the two and its fibres are inserted slightly behind and below the

upper muscle.

Postero-lateral dilators: one pair, which are less compact than those of

Cancer. Each arises behind the antero-lateral dilator muscles towards the anterior

end of the mandibular epimeron and passes inward and backward, spreading

out as a broad sheet of fibres which are inserted on the ventral margin of the

postpectineal ossicle.

Posterior dilator. This paired muscle, which is absent in Cancer and Paratel-

phusa, is short, narrow, and compact, and is attached to the postero-dorsal

border of the cephalic apodeme. Crossing over the outer surface of the ventral

pyloric dilator muscle, it passes forward and is inserted postero-laterally on the

wall of the cardiac fore-gut below the postero-lateral cardiac plate and near

the upper limit of the oesophagus.

Dorsal pyloric dilators: two pairs, the anterior and posterior, arising from

the postero-median part of the gastric region of the body wall, a short distance

in front of the cervical groove and just behind the attachment of the inner

posterior gastric muscles. On each side the two muscles pass forward and down-

ward parallel to each other, the anterior muscle being inserted on the dorsal

wall of the pyloric fore-gut behind the pyloric ossicle and the posterior muscle

on the mesopyloric ossicle in front of the dorsal valve.

Ventral pyloric dilator. There is a single pair, corresponding with the inner

of the two pairs of Cancer (Pearson, 1908). Each is a long, strap-shaped band

originating anteriorly on the base of the anterior mandibular apodeme. It

runs slightly backward and abruptly upward medial to the ventral cephalic

muscle, and is inserted on the antero-inferior ossicle in the ventral wall of the

pyloric fore-gut.

Upper anterior oesophageal dilators: one pair, attached to the median apodeme

of the epistoma ventral to the lower anterior dilator muscles of the cardiac

114 ANNALS OF THE SOUTH AFRICAN MUSEUM

fore-gut. Each consists of a number of separate fibres which pass backward and

slightly upward and are inserted on the anterior wall of the oesophagus.

Lower anterior oesophageal dilators: one pair of narrow inconspicuous muscles,

arising below the origins of the previous pair and passing directly backward to

the anterior wall of the oesophagus.

Lateral oesophageal dilators—one pair. Each muscle originates on the postero-

lateral corner of the epistoma, passes backward and slightly obliquely upward,

its separate fibres diverging as they are inserted along the lateral wall of the

oesophagus.

Posterior oesophageal dilators: one pair, each of which is a relatively strong

muscle composed of a series of muscle strands arising together on the anterior

margin of the cephalic apodeme above and medial to the attachment of the

mandibular major abductor muscle. It runs forward and acutely downward

and is inserted on the posterior wall of the oesophagus. Like the posterior

dilator of the cardiac fore-gut, this muscle crosses over the ventral pyloric

dilator.

(b) Intrinsic muscles

Cardio-pylorics. These occur in the dorsal depression above the urocardiac

ossicle and comprise a median and two lateral bundles extending backward

from the posterior border of the cardiac ossicle. The median muscle is inserted

on the dorsal margin of the prepyloric ossicle, while the Jateral muscles pass

obliquely outward to the antero-lateral corner of the exopyloric ossicles.

Lateral cardiacs. As in Cancer (Pearson, 1908) and Paratelphusa (Patwardhan,

1935), three pairs of these muscles occur on each side of the posterior region of

the cardiac fore-gut. The upper muscle arises from the posterior end of the

subdentary ossicle and passes upward and forward to the dorso-lateral edge of

the zygocardiac ossicle as a narrow band of fairly stout fibres. The middle muscle

is slightly longer than the preceding one and also consists of rather thick fibres.

It is attached to the infero-lateral cardiac ossicle and runs obliquely upward

and forward below and parallel to the upper muscle. It is inserted partly on

the antero-lateral corner of the zygocardiac ossicle but mainly on the pre-

pectineal ossicle. The lower muscle forms a broad sheet of delicate strands which

partly cover the postero-lateral cardiac plate, being inserted along its anterior

border and originating on the anterior edge of the infero-lateral cardiac ossicle.

Mocquard’s (1883) suggestion, cited by Pearson (1908), that the lateral

cardiac muscles serve to raise the cardio-pyloric valve is doubtless a true

interpretation of their function but, at the same time, it is also probable that

their contraction will be instrumental in widening the ventral food grooves

which lie between the cardio-pyloric valve and the infero-lateral cardiac ossicles.

Postero-inferior cardiac. In Cancer (Pearson, 1908) and in Paratelphusa (Pat-

wardhan, 1935) this is a median muscle stretching between the two infero-

lateral cardiac ossicles. In Fasus it is effectively similar, but appears to be paired,

the short fibres passing on each side from the posterior edge of the infero-lateral

THE ANATOMY OF THE CAPE ROCK LOBSTER II5

cardiac ossicle to a slender, mid-ventral rod which supports the floor of the

cardio-pyloric valve. It seems likely that they are antagonistic to the lateral

cardiac muscles and are capable of compressing the cardio-pyloric valve and

the ventral food groove.

Anterior cardiac. As it arises on the anterior margin of the cardiac ossicle,

the dorsal part of this median muscle is obscured by the anterior gastric and

the upper anterior dilator muscles. Its delicate fibres spread over the anterior

wall of the cardiac fore-gut and, like the next pair of muscles, serve to constrict

this part of the proventriculus.

Antero-lateral cardiacs. This name was given by Pearson (1908) to a pair of

muscles passing upward from the antero-lateral cardiac plates towards the

mid-dorsal wall. In Fasus somewhat similar muscles are inserted on these plates

above the extrinsic antero-lateral dilator muscles and are attached to the

prepectineal and pterocardiac ossicles.

Lateral pylorics. The wall of the pyloric fore-gut is constricted by a number

of fibres which seem to be arranged on each side into three main muscles. The

anterior muscle forms a sheet of delicate strands attached to the anterior margin

of the lateral pyloric ossicle; they pass obliquely forward and upward across

the anterior chamber of the pyloric fore-gut and are inserted on the pyloric

ossicle. The middle muscle consists of rather stronger fibres arising on the lateral

cardio-pyloric and the anterior supra-ampullary ossicles. They run almost

vertically upward to the posterior margins of the lateral pyloric and meso-

pyloric ossicles and thus cover the anterior part of the press. The posterior

muscle is located in the wall of the posterior half of the press, extending from

its lateral to its dorsal border and being subequal in strength to the middle

bundle.

The oesophageal constrictors are fine circular fibres which run in the wall

of the oesophagus and serve, as their name denotes, to reduce the lumen of

this tubular part of the fore-gut.

4. SIGNIFICANCE OF THE PROVENTRICULUS

An internal masticatory apparatus, the so-called ‘gastric mill’, is a feature

of the malacostracan proventriculus, and it has been demonstrated by Pat-

wardhan (1935) and Reddy (1935) that its elaboration in the Decapoda is

directly correlated with the types of mandibles in the different subdivisions

of the order. Possessing well-defined incisor and molar processes, the mandibles

of most Natantia are efficient masticatory organs and, while a filtering apparatus

is present in the pyloric fore-gut, a complicated gastric mill is usually lacking in

the cardiac fore-gut, being replaced by spinous valves. Contrasted with these

circumstances, the mandibular incisor and molar processes are indistinct in

Reptantia and, to compensate for the inadequate fragmentation of the food

by the mouth-parts, an ingenious internal mill has been designed for the final

comminution of the food. The foregoing account of the complex structures and

the intricate musculature of the proventriculus of Fasus is a measure of the

116 ANNALS OF THE SOUTH AFRICAN MUSEUM

importance of this part of the alimentary tract as a grinding and _ filtering

mechanism for reducing the food and directing the finer particles towards the

mid-gut and the digestive gland.

Once the food has been dealt with by the mouth-parts and forced into the

mouth, it travels up the short, vertical oesophagus, its transit being controlled

by the antagonistic action of the oesophageal dilatator and constrictor muscles.

At the junction of the oesophagus and the capacious cardiac fore-gut a ventral

and two lateral valvular folds assist in narrowing the passage and in retaining

the food in the cardiac chamber. Within the latter the food is pulverized by

the strong median and lateral teeth (figs 32-34), after which there is a separa-

tion of the finer from the larger particles, which then flow along different routes

through the pyloric fore-gut.

a wall of pyloric

aN fore -gut

mu 26

posterior gastric

artery

wall of press

inter-ampul lary

ridge

filter chamber {\ Aces 1 setae of

: filter

supra-ampullary

ridge

cuticular rods

ampulla

Fic. 36. Puerulus stage: transverse section through posterior part

of pyloric fore-gut.

A reasoned exposition of the passage of food through the alimentary canal

of Nephrops norvegicus has been given by Yonge (1924), and a similar course of

events in the proventriculus is applicable to Fasus. Owing to the disposition of

the ossicles, pads and folds of the proventricular wall, certain food grooves or

channels are clearly demarcated. A pair of ventral grooves (figs 32, 34), extending

from the oesophagus to the posterior half of the pyloric fore-gut and supported

by the closely-approximated postpectineal and infero-lateral cardiac ossicles,

form a gutter on each side of the cardio-pyloric valve and lead towards the

ampullae. Running backward from the median tooth to the base of the dorsal

THE ANATOMY OF THE CAPE ROCK LOBSTER MCF

dorsal lobe

: : tubules of digestive gland

developing testis

a ee

Yom)

SAS

Gye

* TAPE en 5

Aa “2 my

8 Se TD,

mid-gut filter

SSNS) Gx

Savy ES: “S

LEY LF

hepatic duct

0.2 mm.

fore-gut epithelium

inter-ampullary ridge

Fic. 37. Puerulus stage: transverse section through hepatic ducts.

caecum of the mid-gut and lying above the press, are two dorso-lateral channels

which, according to Yonge (1924), may be described as the mid-gut filter (fig.

37). Lateral grooves, bounded by the zygocardiac and subdentary ossicles and

by the pads at the sides of the postero-lateral cardiac plates, communicate with

the press in the posterior part of the pyloric fore-gut.

It has also been demonstrated by Yonge (1924) that the secretions from

the digestive gland pass forward along the ventral grooves and become mixed

with the food during mastication in the cardiac chamber. Digested and fine

particulate matter is then conveyed backward via the ventral grooves and

traverses the filter chamber (fig. 36) which is bordered by the setae of the ampullae

and their supra-ampullary ridges. On leaving the filter chamber, the sifted

material passes into the mid-gut and enters the digestive gland, in the tubules

of which absorption and storage of good substances takes place. Simultaneously,

the larger undigested fragments are swept along the lateral grooves and the

mid-gut filter into the press and thence, in Jasus, are guided through the

pyloric valves into the hind-gut.

The mechanism of the gastric mill and the flow of food through the fore-gut

are governed by the previously-described sets of muscles. Based on Huxley’s

118 ANNALS OF THE SOUTH AFRICAN MUSEUM

(1881) account of the gastric mill of Astacus, it is generally assumed that the

anterior and posterior gastric muscles are mainly responsible for the approxi-

mation of the median and lateral teeth, the gnashing action of which is effective

in triturating the food. When the anterior gastric muscles contract, the cardiac

and urocardiac ossicles are pulled forward; as this also adjusts the prepyloric

ossicle, the median tooth on the urocardiac ossicle is brought forward and

directed vertically downward. Added to this operation, the backward pull on

the pyloric and exopyloric ossicles, exerted by the contraction of the posterior

gastric muscles, and perhaps to some extent by the constriction of the wall by

the lateral cardiac muscles, affects the inclination of the zygocardiac ossicles,

causing them to be rotated inward. Thus, when the anterior and posterior

gastric muscles contract simultaneously, the large denticles of the lateral teeth

are brought into contact with the median tooth, and their concerted grinding

action disintegrates the food. Evidence quoted by Pearson (1908), Yonge (1924),

and Balss (1944) suggests that, when the gastric muscles relax, the ossicles

revert to their normal resting position with the teeth apart, partly owing to

the elasticity of the walls at their points of articulation, and partly as a result

of the contraction of the intrinsic cardio-pyloric muscles.

5. DIGESTIVE GLAND (Figs 10, 31, 51, 53, 77, 78)

The digestive gland, hepatopancreas, or ‘liver’, is a paired, voluminous,

yellowish organ, composed of numerous, discrete, digitiform tubules and

enclosed in a delicate syncytial membrane. It is primarily an outgrowth of the

mid-gut and occupies a considerable portion of the cephalothoracic body

cavity, each half of the gland lying mainly between the alimentary tract and

the lateral body wall and being divisible into anterior, dorsal, and posterior

lobes.

The anterior lobe (figs 38, 51, 77) is situated below the antennal promotor

muscle and lateral to the proventriculus. It extends almost to the anterior limit

of the body cavity and projects ventro-laterally into the concavity of the

anterior apodeme of the mandible.

The middle or dorsal lobe (figs 37, 38, 51, 77), which partly overlaps the

other two lobes, lies chiefly in front of the cervical groove and practically in

line with the two bundles of the mandibular posterior adductor muscle. It is

widest anteriorly, where it spreads out laterally between the anterior part of

the branchiostegite and the roof of the prebranchial chamber.

The posterior lobe (figs 37, 51, 77) is larger and more ventral than the other

two lobes. It stretches approximately from the cervical groove to the end of the

sixth thoracic segment and is located ventro-laterally below the pericardial

septum.

On each side the digestive gland communicates with the mid-gut by a

relatively wide hepatic duct (figs 31, 33, 37), which branches into each of the

three lobes and therein forms a system of ramifying ductules that are ulti-

mately continuous with the lumina of the tubules of the gland (fig. 37).

THE ANATOMY OF THE CAPE ROCK LOBSTER 119

It has been shown by Yonge (1924), Van Weel (1955), and Vonk (1960)

that the digestive gland of decapod Crustacea has several functions; it is not

only concerned with the secretion of various enzymes such as proteases, lipases,

and carbohydrates, but it is also an important organ for the absorption of

nourishment and for the storage of glycogen, fat, and sometimes calcium.

E. ExcRETORY ORGANS

In a discussion of facts concerning excretion in Crustacea, Parry (1960)

has shown that the urine produced by the antennal glands of Decapoda

generally contains relatively small quantities of nitrogenous substances, and

that other organs and tissues contribute towards the elimination of waste

products. It has also been demonstrated by Parry (1960) and Robertson (1960)

that, while the antennal glands of some fresh-water decapods are osmoregu-

latory in function, in marine species the antennal glands mainly participate in

the ionic regulation of the body fluids.

I. ANTENNAL GLANDS

The two antennal glands are situated at the bases of the antennae on either

side of the cardiac fore-gut. Each gland may be exposed by removal of the

lateral part of the head exoskeleton, but satisfactory dissection of the entire

organ is somewhat difficult owing to the fact that it is wedged between the

anterior viscera, particularly between the powerful muscles of the antenna.

The whole is a compact structure which lies rather superficially beneath the

body wall and occupies the haemocoelic space bounded by the mandibular

lateral adductor muscles, the cardiac chamber of the fore-gut, and the base of

the antennal peduncle. Dorsally it is largely obscured by the antennal promotor

muscle which, however, can easily be removed; but intervening between the

anterior and posterior parts of the gland is the strong levator muscle of the

antenna, careful excision of which is required before all the parts of the organ

can be displayed.

Marchal’s (1892) article on the antennal glands of decapod Crustacea is

one of the most comprehensive reports on the subject. Not only has it formed

the basis of subsequent accounts of the so-called ‘green gland’ of the fresh-water

crayfish, Astacus, but it also contains factual descriptions of the excretory

organs of a variety of species representative of the main subdivisions of the

Decapoda. Later investigations, such as Waite’s (1899) observations of the

antennal glands of Homarus and the comparative study of the excretory organs

of Astacus and Homarus by Peters (1935), have largely substantiated Marchal’s

findings, while surveys by Parry (1960), Robertson (1960), and Lockwood

(1962) disclose the current research interest in various aspects of the physiology

of the antennal glands.

Marchal (1892) has shown that the essential parts of the decapod antennal

gland are the end sac, the labyrinth, and the bladder or vesicle. These three

structures usually intercommunicate consecutively, and transmission of the

120 ANNALS OF THE SOUTH AFRICAN MUSEUM

post. adduc. muscle of mandible

cardiac fore-gut

WwW Ol

digestive gland

(dorsal lobe)

bladder

digestive gland

white lobe of labyrinth (anterior lobe)

antennary artery.

carapace

excretory tubercle

excretory aperture

Fic. 38. Diagram of left antennal gland zn situ.

excretory products to the exterior is effected by the ureter, which is continuous

with the bladder and discharges on an excretory tubercle at the base of the

antenna. The arrangement of the parts is variable, especially in the Macrura

Reptantia and, although the antennal gland of Astacus is sometimes regarded

as typical of Decapoda, Marchal considered it to be somewhat exceptional, but

he made the important observation that the structural differences between it

and the gland of marine species might signify adaptive modifications to their

respective external media. Even among marine species, however, there is

vesicular arteries

white lobe of labyrinth

° ureter

3 bladder

4 dntennary artery.

labyrinthic ant. renal artery

tubules

post. renal artery

approx.’ position of nephrostome

ureter

mdin lobe of labyrinth

tubercle

excretory ee

Fic. 39. Diagrammatic side view of left antennal gland, removed from the body.

THE ANATOMY OF THE CAPE ROCK LOBSTER IQ]

apparently no uniform structural plan, and some of the most interesting

variations elucidated by Marchal relate to the morphology of the end sac and

the labyrinth.

In Palaemon, Astacus, and the Brachyura the end sac is distinct and per-

ceptible on the dorsal surface of the labyrinth. Frequently, however, the end

sac and the labyrinth are either intricately branched or the lumen of both may

be subdivided by partitions, which develop as infoldings of the walls and

obviously increase the surface area of these parts. Unlike that of Astacus, the

end sac of the majority is ventrally prolonged into a number of processes which

burrow deeply between the convolutions of the labyrinth wall and, in what

may be regarded as extreme examples of this interdigitation of the two parts

(Galatheidae, Thalassinidea, and Paguridae), the end sac may be so completely

embedded in the labyrinth that even its dorsal wall is no longer visible on the

surface of the gland. The bladder is also variously modified and, while in many

Macrura it is a relatively simple sac, in the Anomura, the Brachyura, and in

Palaemon among Natantia it may be extensively and intricately lobed.

Marchal’s (1892) exhaustive studies indicate that the antennal gland of

nearly every decapod species presents its own structural peculiarities and, in

this respect, 7. lalandii is no exception. From the following account, which is

based on dissections and serial sections of the glands of adult specimens, it is

apparent that, although there is some resemblance to the organs of Homarus

and Palinurus, the parts are not morphologically identical with those of any

other species so far described.

branch of end sac

central cavity of end sac

posterior

renal artery

nephrostome

central cavity

of labyrinth

wall of labyrinth 4 ca secretory globules

Fic. 40. Part of transverse section of antennal gland.

122 ANNALS OF THE SOUTH AFRICAN MUSEUM

(a) The end sac

The end sac differs from that of the well-known Astacus in not being exposed

on the dorsal surface of the labyrinth. As in Anomura and Palinurus (Marchal,

1892), it is completely enveloped by the labyrinth and therefore can only be

properly identified in sectioned material (figs 40, 41). It is relatively voluminous

and has a fairly distinct central cavity (fig. 40) which is located more or less

dorso-laterally in the middle of the main lobe of the labyrinth. From this

numerous branches radiate in all directions into the interstices of the labyrinth,

so that the body of the gland is a compound of both the end sac and the

labyrinth.

Waite’s (1899) statement that in Homarus the end sac is a derivative of the

embryonic coelom and that the remainder of the gland is ectodermal in origin

has been quoted in several subsequent publications; but Manton (1928, 1934)

has shown that both the duct and the end sac are mesodermal and that only

the tube which leads to the exterior is ectodermal. Functional differences of

the parts may account for the marked histological contrast between the walls

of the end sac and the labyrinth in 7. lalandii. The wall of the end sac is formed

by a delicate layer of rather irregular cells (fig. 41), each of which contains a

large nucleus and faintly staining granular contents and is 11-5 to 14:3 » high.

lumen

Fic. 41. Transverse section of wall of

end sac.

(b) The labyrinth

The labyrinth is the spongy mass forming the bulk of the antennal gland

and which, for descriptive purposes, may be divided into a main lobe and a

white lobe.

The main lobe (figs 38, 39) constitutes the posterior part of the labyrinth

lying adjacent to the anterior apodeme of the mandible. It is cream coloured,

and when viewed laterally is roughly quadrangular in outline with its antero-

ventral extremity usually curved forward almost to the level of the excretory

pore. In most of specimens examined, an anterior fissure demarcates a more or

less leaf-shaped lateral area from the larger more medial part of the main lobe

THE ANATOMY OF THE CAPE ROCK LOBSTER 123

and marks the approximate position of the underlying central cavities of the

end sac and the labyrinth. It is also in this region that the end sac communi-

cates with the labyrinth by an opening, which is sometimes termed the ‘nephro-

stome’ (fig. 40). In many marine species (Marchal, 1892; Peters, 1935) this

orifice is furnished with a valve-like structure which, however, is apparently

absent in fresh-water forms, such as Astacus (Peters, 1935) and Procambarus

(Maluf, 1941). Sections of the antennal gland of asus reveal that the valve

(fig. 40) is conspicuous and essentially similar to that described by Peters

(1935) in Homarus in that it is composed of relatively large cells which stain

feebly and resemble the epithelial cells of the end sac. It therefore seems likely

that, as Peters suggested, the valve represents a mass of modified end-sac cells

which, by hanging into the central cavity of the labyrinth, forms a closing

device between the two principal parts of the gland and prevents regurgitation

of fluids into the end sac. It is also noteworthy that in the vicinity of the valve

there is a conspicuous accumulation of haemocytes. These have been omitted

in figure 40, but occur in a dilatation of the thin-walled renal vein, into which

blood from the posterior renal artery (figs 39, 40) drains at the hinder limit of

the valve. The venous channel runs parallel to the central cavity of the end

sac and leaves the antennal gland in front of the valve.

The lumen of the labyrinth is broken up into numerous irregular channels

by invaginations of its wall, but in the neighbourhood of the valve there is a

central cavity (fig. 40) which communicates directly with the end sac through

the ‘nephrostome’. The epithelium of the labyrinth (fig. 42) is easily distin-

ww |"O

striated border

Fic. 42. Transverse section of wall of labyrinth.

guished from that of the end sac, not only by its larger, more columnar cells

which are from 18 to 22 » high, but also by its more intensely stained cyto-

plasm. The nuclei are fairly large and almost centrally placed, and the granular

cytoplasm is characterized by fine, but obvious, longitudinal striations. It is

particularly noticeable that the free margin has the appearance of a striated

border, which is comparable with the ‘Porensaum’ of Astacus and Homarus

(Peters, 1935) and is surmounted by numerous globules of various sizes and

124 ANNALS OF THE SOUTH AFRICAN MUSEUM

shapes. These project into the lumen and, as most of the ramifications of the

labyrinth are practically filled with free globules, it seems as though they

have been detached from the epithelial cells as products of active secretion.

Occasional cells are slightly larger than normal and are conspicuous by their

paler staining properties, which may indicate some phase of this process.

In describing the antennal gland of Homarus, Marchal (1892) referred to

the more anterior portion of the labyrinth as the white lobe, a term which was

later accepted by Waite (1899) and Peters (1935). In Jasus the main lobe of the

labyrinth is continuous with a dorso-ventrally flattened forward extension,

which may likewise be termed the white lobe (figs 38, 39) because it is somewhat

lighter in colour than the main lobe and may be analogous to this particular

part of the labyrinth of Homarus. Macroscopically it appears to be less compact

than the main lobe of the labyrinth, but examination of sections indicates that,

while its wall may be less intricately folded, there is little histological difference

between it and the main lobe. As in the latter, ramifications of the end sac run

parallel to the canals of the white lobe, so that the total volume of the end sac

is subequal to that of the labyrinth.

The white lobe curves upward, forward, and inward over the levator

muscle of the antenna and extends almost to the cerebral ganglion. Passing

downward from its anterior extremity are a number of peculiar, branched

tubules which invade the lumen of the ureter and are attached to its anterior

wall by connective tissue strands. These labyrinthic tubules, as they are herein

labelled (fig. 39), are produced into small, conical processes which project

freely into the lumen of the ureter, where each probably opens by a minute

pore. The presence of pores is difficult to determine both in whole mounts and

in sectioned material and, so far as can be ascertained, there is no direct

opening from the labyrinth into the bladder. The labyrinthic tubules therefore

represent the only connexion between the glandular and the storage parts of

the organ, and it seems logical to suppose that their free ends are perforated.

In Palinurus Marchal (1892) has described an accessory gland (glande

annexe) which opens by a fine canal into the ureter, but is distinct from the

labyrinth; the latter, however, communicates with the bladder by a number of

dorsal pores. No such accessory gland is present in Fasus, but a possible analogy

between it and the tubules in the ureter cannot be overlooked. In this context,

it is of interest to note that Marchal (1892) and Waite (1899) have shown that

in Homarus there is also no direct passage from the labyrinth into the bladder

and that the white lobe opens into the ureter by several minute pores. From

this it may be inferred that the arrangement in Jasus closely approximates that

of Homarus in the rather unusual relationship between the labyrinth and the

ureter. It follows that, as in Homarus, waste products must reach the bladder

by a somewhat devious route, having to proceed along the ductules of the

labyrinth into the ureter and thence upward and backward into the bladder.

In confirming Marchal’s original observations, Waite concluded that storage

of urine in the bladder could be effected by closure of the external excretory

THE ANATOMY OF THE CAPE ROCK LOBSTER 125

aperture. While this is a possibility, it may be significant that in Fasus

the narrow, so-called remotor muscle of the antenna (figs 18, 38) runs obliquely

across the main lobe of the labyrinth. As previously mentioned (p. 74), this

muscle may merely support the labyrinth, but its insertion on the epidermis a

short distance from the excretory pore and almost on a level with the lower

end of the labyrinthic tubules in the ureter also suggests that it may participate

either in forcing urine into the bladder or in its expulsion to the exterior.

The bladder or vesicle (figs 38, 39), within which the urine is stored before

being voided from the body, is a large, transparent, roughly globular sac, the

lower wall of which is inseparably adherent to the upper surface of the laby-

rinth. Its delicate wall consists of a single layer of small columnar cells which

are structurally similar to those of the peripheral part of the labyrinth. On the

outer surface there is a thin connective-tissue layer, which is probably highly

contractile, for the bladder shrinks immediately and markedly upon immersion

in fixing agents. Owing to its transparency, the full extent of the bladder is not

easily discernible in ordinary dissections but, by injecting coloured latex or

coloured gelatine mass either directly into it or through the excretory pore,

the whole structure is thrown into relief against the neighbouring organs. It

can then be seen that medially, dorsally and ventrally it fits closely into the

contours of the cardiac fore-gut, while posteriorly it extends between the anterior

and dorsal lobes of the digestive gland and may even invade the former.

Anteriorly it projects for a short distance in front of the white lobe of the laby-

rinth and narrows considerably as it approaches the ureter.

(d) The ureter

The ureter (figs 38, 39) is the transparent, relatively broad efferent duct

continuous with the bladder. It is antero-posteriorly flattened, and is so closely

applied to the base of the proximal segment of the antenna that it is largely

obscured by the antennal levator muscle which occupies the space between

the main lobe of the labyrinth and the ureter. As it passes outward from the

bladder, its lateral wall lies rather superficially below the base of the antennal

peduncle; the duct then curves backward for a short distance and narrows as

it proceeds to its small, crescentic opening situated anteriorly at the tip of a

whitish, conical tubercle (figs 38, 39) on the ventro-lateral surface of the

epistoma. Marchal (1892) and others have described the flexible membrane

stretching across the tubercle as the operculum but, as Maluf (1941) has

rightly observed, the term is inappropriate, for in most decapods the excretory

aperture is exposed on the surface of the membrane and is not covered by it.

Balss (1944), however, has summarized the operation of the so-called operculum

in Brachyura, and has explained that early observers regarded the antennal

glands as auditory organs.

126 ANNALS OF THE SOUTH AFRICAN MUSEUM

(e) General remarks

The most significant difference between the antennal gland of the fresh-

water crayfish, Astacus, and that of Jasus and other marine Decapoda is the

presence in the former of a long, convoluted nephridial canal or white medullary

tubule, which is intercalated between the greenish labyrinth and the bladder.

It was suggested by Marchal (1892) that the absence of this canal in marine

decapods and the functional differences between their glands and those of

fresh-water species might be correlated with the salinity of the external medium.

In apparent confirmation of this, it has been demonstrated by Peters (1935)

that, contrasted with the urine of the marine Homarus which is known to be

isotonic with the blood, that of Astacus is markedly hypotonic owing to a

decrease in the chloride concentration of the urine in transit from the labyrinth

to the bladder. The production of a hyposmotic urine may therefore indicate

that the additional part or nephridial canal in the antennal gland of crayfishes

is an adaptation to their fresh-water habitat. It has generally been considered

that the canal assists in necessary osmoregulatory processes, and that the

dilution of the urine is effected either by an outward secretion of water or by

the resorption of chloride from the excretory products passing through its

lumen. However, in recent analyses of the fluid removed from different parts

of the antennal glands of fresh-water crayfishes Riegel (1965) has shown that

the bladder may be even more important than the nephridial canal in diluting

the urine. Some information is also available concerning the function of the

antennal glands of marine species, Forster & Zia-Walroth (1941) having con-

cluded that water is neither secreted nor resorbed in the antennal glands of

Homarus americanus, while Burger (1955-7) has shown that, although the

glands of Homarus are capable of resorbing glucose, they are not instrumental

in the conservation of chloride, which presumably enters through the gills.

The gist of existing knowledge collated by Parry (1960), Robertson (1960), and

Lockwood (1962) is that, except in such fresh-water forms as crayfishes, Asellus

aquaticus and species of Gammarus, and in the brackish-water Gammarus duebent,

the urine of Malacostraca is generally isotonic with the blood and the excretory

glands play no significant part in osmoregulation. According to Robertson

(1960), it has also been established that in marine decapods the main function

of the antennal glands is the maintenance of the ionic balance of the body

fluids. Selective excretion of Mg** and SO,—— by the antennal glands has

been proved in a number of species, while other ions, including K* and Catt,

are conserved.

There is still no universal agreement among physiologists regarding the

method of urine formation, and opinions differ as to whether it is a product of

filtration or of secretion. For different reasons, Peters (1935) and Picken (1936)

decided that the processes of filtration, secretion, and resorption probably

take place in the antennal glands in much the same way as they do in the

vertebrate kidney. Based chiefly on histological studies of the antennal glands

of Astacus and Homarus, the former investigator deduced that the primary urine

THE ANATOMY OF THE CAPE ROCK LOBSTER 127

is produced as an ultrafiltrate of the blood supply to the wall of the end sac,

and a similar conclusion was reached by Picken on determining that the hydro-

static pressure of the blood of Astacus usually exceeded its colloid osmotic

pressure. Some additional data supporting the filtration theory have been

presented by Forster & Zia-Walroth (1941) and Burger (1955-7), whose

experiments on inulin renal clearances in Homarus americanus demonstrate that

in this animal the primary urine is probably formed by filtration. Furthermore,

the unusual glycosuria reported by Burger in lobsters treated with phlorizin,

a drug known to check resorption of glucose from the vertebrate kidney, may

have a similar significance.

Histologically there is a resemblance between the antennal glands of

Homarus and Jasus, in both of which the marked structural differences between

the epithelial cells of the end sac and the labyrinth suggest functional differen-

tiation of the parts. Whereas occasional cells of the end sac of 7. lalandii may

have granular contents and the lumen is practically empty (figs 40, 41), the

convoluted channels of the labyrinth (figs 40, 42) are filled with globules.

Similar vesicles or ‘Sekretblasen’ in the labyrinth of Astacus and Homarus were

regarded by Peters (1935) as products of the wall of this part of the gland, and

he implied that active resorption of essential substances from them into the

blood could take place in the nephridial canal. Moreover, while Peters doubted

the secretory potential of the end sac, Marchal (1892) was of the opinion

that secretion by the detachment of vesicles from the cells prevails in all parts

of the organ, including the bladder of some species. However, Parry (1960) has

indicated that filtration is possible through the presumed semipermeable wall

of the end sac, especially as there are pressure differences between its blood

supply and its lumen. In dissections of anaesthetized specimens of 7. lalandit,

it was observed that the blood courses through the antennary artery under

considerable pressure on its way to the antennal gland; this fact and the distri-

bution of the renal arteries would seem to provide some evidence that primary

filtration may take place through the wall of the end sac. The alternative theory

that the urine is produced by secretion also has a number of supporters, whose

studies have been cited by Parry (1960) and Lockwood (1962), but recent

research confirms the presence of a filtration mechanism. Kirschner & Wagner

(1965) have proved experimentally that the primary ultrafiltrate is formed in

the end sac of fresh-water crayfishes, and Riegel (1965) has also subscribed to

this view.

As yet, there is no published information on the physiology of the antennal

glands of 7. lalandi and, although they differ in certain respects from those of

marine species which have been studied by other investigators, several of the

histological similarities between them and the organs of Homarus (Peters, 1935)

may have some significance. It is therefore conceivable that filtration takes place

in the end sac and that some unknown substances are added to the primary

urine in other parts of the gland by secretion from the blood.

128 ANNALS OF THE SOUTH AFRICAN MUSEUM

2. OTHER EXCRETORY ORGANS

From information presented by Parry (1960), it is patent that analyses of

the end products of protein metabolism in Crustacea are compatible with the

findings in most aquatic invertebrates. The antennal glands, however, are

not primarily concerned with nitrogenous excretion and, although ammonia

is the principal waste product, relatively small quantities of it and also of urea

are found in the urine. By contrast, the urine contains rather high percentages

of amino nitrogen, but the source of the small amounts of uric acid known to be

excreted has not definitely been ascertained. The explanation of some of these

facts seems to be that, as a consequence of the importance of the antennal

glands in the regulation of the internal ionic levels, other parts of the body

have become involved in the elimination of nitrogenous wastes.

It has long been assumed that the gills and the digestive glands are essential

components of the excretory system and that the former play an important role

in osmoregulation and ionic balance, their surface permeability, according to

Krogh (1939) and Burger (1957), allowing of an intake of water and salts to

compensate for the loss of these from the antennal glands. Among other things,

Burger (1957) has suggested that ammonia is removed by the gills, while

Parry (1960) has indicated that analyses of the digestive glands of a number of

species demonstrate the presence of relatively large quantities of uric acid. An

excretory function has also been attributed to the gut, to the integument, and

to special large cells, termed the nephrocytes or nephrophagocytes, in which

excretory matter appears to accumulate and is presumably later eliminated by

some means or another. Nephrocytes have been reported mainly in the epipo-

dites, the gills and the branchio-pericardial vessels of Decapoda, and have been

shown by Bock (1925) and Dornesco & Homei (1940) to be confined to the

channels containing oxygenated blood in the gills of Astacus and Palinurus

respectively. Numerous oval cells, measuring about 25 u by 14p, have a

similar distribution in the gills of Zasus. They are conspicuous in transverse

sections (fig. 44) by their size, their staining properties, and their apparent

ability to phagocytose injected India ink, and are doubtless identical with the

nephrocytes of other Decapoda.

F. RESPIRATORY ORGANS

Respiration is performed by a series of 21 pairs of segmentally-arranged

gills or branchiae which, according to the observations of several authors cited

by Calman (1909), develop as outgrowths of the bases of the thoracic appen-

dages. They are lodged on each side of the cephalothorax in a somewhat com-

pressed branchial chamber (figs 43, 53) bounded by the thoracic epimera on the

inside and enclosed by the overarching branchiostegite (figs 1, 2, 10, 53, 77) on

the outside. The latter is a lateral fold of the carapace composed of an outer

strongly-calcified wall and an inner, thin, transparent, cuticular lining which,

for convenience, has been termed the branchial membrane (figs 9, 10, 77); it is

distinguished by its dense, inner covering of short, brown, finger-like processes

THE ANATOMY OF THE CAPE ROCK LOBSTER 129

tipped with slender spines and interspersed with long, straggling, finely-barbed

hairs. The lower margin of the branchiostegite is closely applied to the bases of

the coxopodites of the thoracic limbs, but its slight sinuosity allows of ingress of

water into the branchial chamber through the gaps between the limbs.

i podobranch

prebranc biclgichab cy epimeral attractor muscle

epibranchial space epipodite

scaphognathite arthrobranchs pleurobranch

1st abdom. seg.

==, Se

S WW Semis

20mm.

5th pereiopod

3rd maxilliped ist pereiopod setiferous process

2nd maxilliped hypobranchial space

epipodite of ist maxilliped

Fic. 43. Left branchial and prebranchial chambers.

The gills (figs 43, 53), which curve upward from the limb bases and arch

slightly forward, are arranged into segmental sets from the second to the last

thoracic segment. The successive groups of gills are separated by vertical

epipodites (figs 43, 53, 55), each of which is a thin-walled, lamellate, hairy plate

originating on a conspicuous, somewhat triangular setiferous process (figs 5,

43, 56) at the base of the coxopodite of its corresponding appendage. In some

Decapoda the epipodites are bilobed structures, but in Jasus, although they

are folded down the middle into inner and outer laminae in the puerulus stage,

in the adult the duplication is only apparent in the reflection of the outer

margin of each epipodite over the gills of the segment behind.

According to their attachment relative to the appendages and the body

wall, Huxley (1881) differentiated the gills into three types (figs 43, 53, 55):

the podobranchs arising with the epipodites on the setiferous processes, the

anterior and posterior arthrobranchs associated with the arthrodial membranes, and

the pleurobranchs situated on the epimera. Thus on each side of a typical segment

(fig. 53) there is one epipodite and four gills, but the full complement is only

realized in the fifth, sixth, and seventh segments (fig. 55), the anterior seg-

ments lacking pleurobranchs and sometimes other gills, while the last segment

(fig. 55) has only a pair of pleurobranchs. The arrangement of the various gills

on one side of the body and their corresponding appendages are tabulated in

the following branchial formula, which applies not only to the adult but also in

130 ANNALS OF THE SOUTH AFRICAN MUSEUM

some measure to the puerulus stage. In this connexion, it is of interest to note

Gilchrist’s (1920) conclusions that in the phyllosoma larva there are character-

istically one podobranch, one arthrobranch, and an anterior and a posterior

pleurobranch on each side of a given segment. It is said that this arrangement

is retained in the puerulus stage, but that subsequently the larval posterior

pleurobranch is transposed and becomes the posterior arthrobranch of the

adult. This may account for the somewhat forward position of the first three

pleurobranchs in the adult (fig. 56), and perhaps also explains the fact that in

some juvenile animals the last pleurobranch tends to be aligned more with the

arthrobranchs than with the pleurobranchs of other segments.

Anterior Posterior

Appendage Epipodites | Podobranchs| Arthro- Arthro- Pleuro- Total

branchs branchs branchs

1st Maxilliped I — — — _ Ep. + 0 gills

and Maxilliped I I — I — INS ae

grd Maxilliped I I I I _ Ep. + 3

1st Pereiopod I I I I _ Ep. +3

and Pereiopod I I I I I Ep. + 4

grd Pereiopod I I I I I Ep. + 4

4th Pereiopod I I I I I Ep. + 4

5th Pereiopod — — _ — I o+1

Total 7 6 5 6 4. 7 Ep. + 21 gills

The above interpretation of the arrangement of the epipodites and gills

agrees with Huxley’s findings, except for one minor point relating to the single

arthrobranch on the second thoracic segment. Huxley identified this as an

anterior arthrobranch in Astacus and in Palinurus, but Bock (1925) has shown

that in the former genus it is posterior in position. In most thoracic segments

of Fasus (fig. 56) the level of attachment of the podobranch is almost midway

between the anterior and posterior arthrobranchs and, while the exact position

of the single gill on the narrow arthrodial membrane of the second maxilliped

is somewhat elusive, the indications in adult specimens and in sections of the

puerulus stage are that it is slightly behind its corresponding podobranch and

may, therefore, be regarded as a posterior arthrobranch.

Structurally each gill belongs to the trichobranchiate type and is a plumose,

pyramidal organ having a central shaft or gill axis, which is roughly triangular

in transverse section (fig. 44) with rows of thin-walled, slender gill filaments

(fig. 44) along the longer outer anterior and posterior margins. The narrower

inner or more medial surface of the axes of the arthrobranchs and the pleuro-

branchs is almost smooth, being furnished only with sparsely-distributed,

minute, hooked setae, but that of the podobranchs has a fairly dense covering

of long, finely-barbed setae similar in appearance and length to those on the

surfaces of the epipodites. The filaments decrease progressively in number and

THE ANATOMY OF THE CAPE ROCK LOBSTER 131

tegumental glands peuticle

seta

/ Be :

/ , epidermis

connective tissue

fe!

efferent branchial vessel =o

nephrocytes

mantle canal

s ———e

nner filaments afferent branchial vessel

efferent channels

afferent channels

mantle canal mantle canal

Fic. 44. Diagrammatic transverse section of last left pleurobranch of adult; a, to a;, branchial

arteries.

size from the base to the tip of the gill axis and, while they are bilaterally

symmetrical in number and arrangement along the axis of the pleurobranchs,

there are characteristically fewer filaments on one side of the axis of the arthro-

branchs and the podobranchs than on the other.

Microscopic examination of transverse sections (fig. 44) reveals that the

gill axis, like other parts of the body, is bounded by an epidermis consisting

of a single layer of columnar cells interspersed with tegumental glands; its

cuticular layer is fairly thick in the interfilamentar regions but much thinner

on the filaments. The latter are horizontal evaginations of the gill axis, with

the epidermis of which their delicate walls are continuous. Gaseous exchange,

resulting in the oxygenation of the blood, takes place through the epidermis

of the filaments, which, unlike the syncytial condition observed by Dornesco &

Homei (1940) in Palinurus, is composed of cuboidal cells with conspicuous

rounded nuclei.

Four main blood channels occur in the gill axis (fig. 44), the two median

ones being an outer afferent branchial vessel lined with a very thin epithelium and

an inner efferent branchial vessel which is surrounded by a relatively wide dermal

layer of loose connective tissue riddled with blood lacunae. Flanking the median

vessels is a pair of blood spaces corresponding to the circular vessel reported by

Herrick (1911) in the gills of Homarus and to the Mantelkanal, first described

by Bock (1925) in Astacus and later by Dornesco & Homei (1940) in Palinurus.

The two mantle canals are separated from the afferent and efferent branchial

132 ANNALS OF THE SOUTH AFRICAN MUSEUM

vessels by a sheath of rather coarse fibrous connective tissue and attain their

greatest width and adjoin each other between the two median vessels. Pro-

longations of the fibrous coat of each mantle canal extend outward towards

the filaments and appear to participate in the formation of the longitudinal

septum (fig. 44) which divides the lumen of each filament into afferent and

efferent channels. Numerous conspicuous, oval cells, the nephrocytes, occur in the

mantle canals, in the connective tissue around the efferent branchial vessel,

and also along the septa of the filaments where, however, they are located only

on the side of the efferent channels. Their presence is indicative of the sub-

sidiary part played by the gills in the excretory mechanism of the body.

The course of the respiratory current of water through the branchial chamber

is substantially similar to that of Carcinus maenas (Borradaile, 1922) and Astacus

astacus (Bock, 1925), and can be demonstrated easily by introducing carmine

particles in suspension in sea water into the inhalant openings between the leg

bases by means of a fine pipette. To facilitate the observations, the specimen

may be temporarily immobilized by immersing it in an anaesthetic agent,

such as a 1 : 2000 dilution of ‘Sandoz’ in sea water. Within a few minutes the

animal becomes quiescent, and it is then possible to perform simple experiments

to prove that the carmine entering the inhalant openings eventually clouds the

water exuding from the exhalant aperture. Subsequently, to demonstrate the

path of water through the branchial chamber, two ‘windows’, about 1:5 by

I°O cm, may be cut in the branchiostegite, one in the intersegmental region

between the third and fourth pereiopods a short distance above the lower edge

of the branchiostegite, and the other more dorsally at the anterior end of the

branchiostegite just behind the prebranchial chamber. Carmine introduced

between the third and fourth pereiopods will be seen to swirl up around the

bases of the gills into what Borradaile (1922) has termed the hypobranchial space

(fig. 43), and will later be observed through the second ‘window’ to flow for-

ward in the upper or epzbranchial space (fig. 43) on its way to the prebranchial

chamber and the exhalant aperture.

It is thus apparent that the main inhalant stream of water for aerating the

gill filaments enters the branchial chamber through segmental openings between

the limb bases and the lower border of the branchiostegite and that the setae on

these parts are a safeguard against the instrusion of foreign particles into the

branchial chamber. As previously indicated (p. 17), the branchiostegite is

postero-laterally secured to a projecting articular condyle or knob on the last

thoracic epimeron, below which there is a triangular plate corresponding with

the setiferous processes of the coxopodites in other segments. This locking device

and its underlying plate preclude the entrance of water at the postero-ventral

edge of the branchiostegite, but between the first abdominal segment and the

overlapping carapace there is a narrow dorsal passage with an upper row of

inwardly-directed setae which, judging by the course of introduced carmine

particles, allows of an incurrent stream of water for the ventilation of the pleuro-

branch on the last thoracic segment.

THE ANATOMY OF THE CAPE ROCK LOBSTER 133

The passage of water into the lower or hypobranchial space around the bases

of the gills is doubtless facilitated by movements of the appendages, but its

subsequent circulation over the gill filaments and into the epzbranchial space at

the dorsal extremities of the gills is dependent on the scooping action of the

scaphognathite of the second maxilla, which is lodged in the prebranchial

chamber (fig. 43). The latter is an exhalant passage in the cephalic region beneath

the antero-lateral part of the exoskeleton, its immediate roof being the epimera

of the mandibular and maxillary segments. It is separated from the branchial

chamber by the arched and thickened epipodite of the first maxilliped which,

with the exopodite of the same appendage, forms the trough of the prebranchial

chamber. Within this chamber the scaphognathite of the second maxilla lies

more or less horizontally and has freedom of movement, its strong sinuous

action drawing water from the branchial chamber and driving it forward and

out through the exhalant aperture (figs 2, 4, 43). Situated behind the excretory

pore, the exhalant aperture is defined by a slight dorso-lateral deflection of

the roof of the prebranchial chamber and the overlapping edge of the head

exoskeleton, while on its medial border lie the tuft of setae on the antero-

lateral margin of the mandible and a row of short setae in the antero-medial

corner of the prebranchial chamber. When the excurrent stream of water

leaves the exhalant aperture, it flushes obliquely forward over the epistoma,

carrying with it the products from the antennal gland.

That the gills are not the only respiratory surfaces is suggested by the rich

blood supply to the epipodites and the branchial membrane lining the branchio-

stegite, which are sufficiently thin-walled to permit of gaseous exchange between

their contained ramified blood vessels and the inhalant current of water. In

addition to their respiratory function, active chloride absorption has been

attributed to the gills of some freshwater Crustacea by a number of physi-

ologists, among whom Ewer & Hattingh (1952) have also indicated that the

inner surface of the branchiostegite, as well as the gills, of the fresh-water

prawn, Caridina nilotica, has potential chloride-absorbing regions.

G. BLoop VascuLaR System (Figs 44, 46-56, 74)

While the main arteries may be traced in freshly-killed or in preserved

specimens, the vessels are delicate and collapsible and the ramifications of their

finer branches are not easily followed. Injection of various coloured media may

also be rather unsatisfactory, one of the disadvantages being that the heart

ostia are often open in dead animals, and leakage of the injection fluid from the

heart inhibits its flow into the vessels. In the present observations, the best

results were obtained by introducing Higgins black indian ink, diluted with

equal parts of distilled water, into an animal which was partially anaesthetized

after immersion for twenty to thirty minutes in two gallons of sea water con-

taining nine grams of sodium phenobarbitone. After securing the animal to a

dissecting board, a small hole, approximately equal in size to the diameter of

a fine capillary tube, was drilled through the middle of the cardiac region

134 ANNALS OF THE SOUTH AFRICAN MUSEUM

of the carapace, either into the pericardial cavity or into the heart. The capillary

tube, attached by a length of rubber tubing to a raised glass thistle funnel con-

taining the diluted India ink, was then inserted into the hole in the carapace

and the ink was allowed to flow into the vascular system by a slow and regular

drip-feed process. As the ink dripped from the capillary tube, it was carried

by the rhythmical pumping of the heart to all parts of the vascular system,

including the haemocoelic sinuses, the afferent branchial vessels, and the gill

filaments. The operation was completed in from ten to fifteen minutes, by

which time about 5 to 6 cc of the ink had been injected and the animal was

moribund. On removing the capillary tube, the hole in the carapace was

plugged with plasticine and the animal was placed in 10% formalin for a few

days. It was then possible, not only to trace the dilated and clearly-defined

arteries to various parts of the body, but also, as a result of the deposition of

carbon particles, to gain a good impression of the extent of the haemocoelic sinuses.

As in typical decapod Crustacea, the oxygenated blood is pumped from

a short, compact, muscular heart lying in the pericardial cavity into a number of

arteries, which usually branch extensively and terminate in fine vessels in the

tissues and organs. Another characteristic is the absence of direct capillary

connexions between the arterial and the venous parts of the circulation and,

as indicated by Maynard (1960), it is generally assumed that the deoxygenated

blood passing from the tissues traverses interstitial (lymphatic) lacunae before

being collected into sinuses which therefore, strictly speaking, contain haemo-

lymph. In the present account the sinuses are simply regarded as irregular

venous channels; they are more or less continuous throughout the body, and the

wide perivisceral spaces constitute the body cavity or haemocoel.

The general concept is that in most Decapoda the deoxygenated blood

from all parts of the haemocoel eventually drains into a sternal sinus in the

thorax and is then directed into afferent branchial vessels on the outer side of the

gill axes and thus conducted to the gill filaments where oxygenation takes place.

On leaving the gill filaments, the oxygenated blood passes into efferent branchial

vessels which lie on the inner side of the gill axes and communicate with a series

of branchio-pericardial vessels. The latter are located along the inner walls of the

thoracic epimera and discharge dorsally into the pericardial cavity. The blood

then enters the heart through three pairs of openings, the ostia, and, on con-

traction of the cardiac muscles, is driven into the arterial system.

Dissolved in the blood plasma is a copper-containing respiratory pigment

haemocyanin, which has a bluish tint when oxygenated. Wolvekamp & Waterman,

(1960) have given an account of the problems relating to respiration in Crus-

tacea, including the factors influencing oxygen consumption, gaseous exchange

between the external medium and the respiratory surfaces, and oxygen trans-

port by the blood. Various studies of the biochemistry of haemocyanin and

other pigments have been reviewed by Goodwin (1960), and he and Wolve-

kamp & Waterman have indicated that in Arthropoda haemocyanin has only

been found in chelicerates and in decapod and stomatopod Crustacea.

THE ANATOMY OF THE CAPE ROCK LOBSTER 135

I. PERICARDIAL CAVITY AND HEART

(a) The pericardial cavity (Figs 53, 56)

The heart (figs 9, 10, 31, 53, 78) lies in the middle of an irregu-

larly rectangular space, the pericardial cavity, which occupies the mid-dorsal

posterior half of the cephalothorax and is exposed on removal of the cardiac

region of the carapace (fig. 9). The pericardial cavity is roofed over by the

dorsal body wall, while ventrally there is a thin pericardial septum (fig. 53) which

forms a broad, somewhat convex, horizontal sheet extending above the posterior

lobe of the digestive gland and the reproductive organs and is attached laterally

to the epimeral plates. Anteriorly the septum slopes upward behind the dorsal

lobe of the digestive gland to meet the body wall, while the posterior boundary

of the cavity is formed by the union of the septum with the anterior margin

of the first abdominal segment. The septum is a transparent, elastic membrane

containing delicate, lateral alary muscles which pass inward from the epimera

as a series of contiguous, parallel bands; they do not extend across the middle

third of the septum, and frequently appear to be stronger posterior to the

heart. Although the heart is completely separated from the general perivisceral

haemocoel, the pericardial wall is perforated anteriorly and posteriorly by the

main arteries leaving the heart and ventro-laterally by the entrance of the

branchio-pericardial vessels. In addition, the paired lateral and deeper thoraco-

abdominal muscles invade the pericardial cavity (figs 9, 10, 45, 53) and lie

one above the other on each side of the heart.

(b) The pericardial pouches (Figs 9, 45)

Posteriorly the pericardial cavity is prolonged into a wide dorsal space

which is covered by the inturned posterior margin of the carapace and the thin

intertergal arthrodial membrane between the cephalothorax and the abdomen,

while the pericardial septum forms its floor. In the vicinity of the articular

condyle for the carapace, it expands somewhat into a lateral pocket, and a

slightly paired effect is produced. The two halves thus seem comparable to the

pericardial pouches which have been described in Brachyura by Pearson (1908),

Drach (1939), and Bliss (1956, 1963), but they appear to be relatively smaller

and to contain less connective tissue. The whole structure seems to be a modi-

fication of the anterior half of the thoraco-abdominal intertergal region and

has a basket-like appearance owing to the presence of fairly obvious, inner

transverse muscles and thinner, outer longitudinal muscles.

The transverse muscles form a sheet of more or less parallel fibres, those

of the two sides meeting at a median raphe; but as they differ in length, their

lateral attachments take the form of a curved line on the wall of the pouch,

with some of the anterior fibres extending between the posterior edge of the

epimeral plate and the inner ridge of the carapace. On each side of the mid-

line the longitudinal fibres are attached to the dorsal body wall at the junction

of the inturned margin of the carapace and the thoraco-abdominal intertergal

136 ANNALS OF THE SOUTH AFRICAN MUSEUM

epimeral attractor muscle

z longitudinal muscles

transverse muscles

cardiac region of carapace

lateral parts of lateral

thoraco-abddominal muscle

intertergal membrane

oblique muscles

triangular sclerite

Fic. 45. Diagrammatic inner view of muscles associated with the pericardial pouches.

membrane, and some may even originate in the postero-dorsal corner of the

branchial chamber. They curve medially and are then usually inflected pos-

teriorly to converge on a narrow, slightly thickened insertion on the line of

flexure of the intertergal membrane. Associated with the longitudinal fibres,

and probably also with some very delicate fibres in the posterior half of the

intertergal membrane, are two parallel bundles of oblique fibres (fig. 45).

These arise on the epimeron behind the epimeral attractor muscle and below

the lateral portions of the lateral thoraco-abdominal muscle. Passing in a

postero-medial direction under the medial section of the latter muscle, they

are inserted at the base of the longitudinal muscles. They are probably con-

cerned with the infolding of the membrane, while the transverse and longi-

tudinal fibres may be responsible for alternate constriction and shortening of

the intertergal membrane and the pouches.

Pericardial pouches have been reported in a number of decapod Crus-

tacea, but for many years their function has been uncertain. In 1939, however,

Drach drew attention to the fact that, although the new lining of the gut in

marine Brachyura is responsible for water absorption, the pericardial pouches

act as storage organs for the absorbed water, and the elasticity of their walls is

effective in controlling the hydrostatic pressure within the body during the

critical period of ecdysis. Bliss (1956, 1963) has also proved experimentally that

in the land crab, Gecarcinus lateralis, while they may be the normal focus of

intake and retention of water during the intermoult, they become greatly

enlarged by increased absorption before ecdysis. The position of the peri-

cardial pouches in other Decapoda also supports the view that they are closely

associated with this process, for, as Travis (1954) has remarked in Panulirus

argus, one of the most striking changes observed in moulting specimens of

J. lalandit before the old carapace became detached was the gradual distortion

of the body between the thorax and the abdomen owing to the distension of the

thoraco-abdominal intertergal membrane. Once the latter had been ruptured,

the old carapace slid forward rapidly and the soft-bodied animal emerged

dorsally between the cephalothorax and the abdomen of the old exoskeleton.

THE ANATOMY OF THE CAPE ROCK LOBSTER 137

The heart is elongate with sloping anterior margins and a rounded pos-

terior extremity; it is a comparatively large, whitish, spongy organ, measuring

about 20 mm long by 8 to 9 mm broad in medium-sized animals. As in other

Decapoda, it is provided with three pairs of slit-like openings, the ostia (figs 31,

46-49, 53), through which the blood collected in the pericardial cavity enters

the heart. The ostia are antero-dorsal, postero-lateral, and ventral in position

and, while the dorsal ostia are directly obliquely forward and outward, the

lateral ostia are more or less vertical and the ventral ostia are transverse. Each

ostium is bordered by fairly wide, thin-walled lips, and closure of the opening

is effected by contraction of a band of muscles along the free edge of each lip.

The muscle bands of the two lips meet at the corners of the opening, and one

overlaps the other before the muscle fibres pass into the wall of the heart.

Inwardly projecting ostial valves, which have been reported in some Mala-

costraca, were not observed.

The heart is suspended in the pericardial cavity by groups of delicate

elastic threads which are associated with the expansion of the heart and the

influx of blood during diastole. The fine strands constituting any one group

usually arise in a common, short, narrow ligament secured to some particular

part of the pericardial wall, but spread out and tend to interlace on their way

to the heart. They are comparable to the alae cordis of Cancer (Pearson, 1908)

and the suspensory ligaments of Astacus (Baumann, 1921), and comprise anterior

and posterior dorsal strands and six sets of fan-shaped lateral bands. As in

Astacus, the anterior ligaments (figs 46, 47) are small, tough strips attached dorsally

to the integument and inserted on either side of the root of the ophthalmic

artery. Posteriorly the heart is suspended mid-dorsally to the body wall at the

anterior margin of the pericardial pouch by a tuft of short fibres which, although

they seem to be paired at their origin, represent the median posterior ligament

(figs 46, 47) of other forms.

lateral ostium

anterior ligament posterior ligament

dorsal ostium

ophthalmic artery } dorsal postero-lateral ligament

mT “i

) ZED nanan

antennory ne 5

dorsal antero-lateral ligament ventral postero-lateral ligament

dorsal abdominal artery

sternal artery

ventral antero-lateral ligament ventral medio-lateral ligament

dorsal medio-lateral ligament

Fic. 46. Side view of heart.

I 38 ANNALS OF THE SOUTH AFRICAN MUSEUM

Three of the six lateral suspensory ligaments (figs 46-48) are inserted

dorsally and the other three ventrally along the lateral edges of the heart. The

dorsal and ventral antero-lateral and postero-lateral ligaments are similar to those

described by Pearson (1908) and Baumann (1921), but between them are

additional bands which have been termed the dorsal and ventral medio-lateral

suspensory ligaments. The dorsal antero-lateral and dorsal postero-lateral liga-

ments are more compact than the others and, while the former is attached

antero-laterally to the pericardial septum behind the dorsal lobe of the digestive

ophthalmic artery

anterior ligament

antennary artery

dorsal antero-

dorsal ostium lateral ligament

dorsal medio-

lateral ligament

dorsal postero-

lateral ligament

\%G

Wy 3

Uli SX

posterior ligament

right genital artery

dorsal abdominal artery

Fic. 47. Dorsal view of heart.

ophthalmic artery

antennary artery

T~{OOCUvennt ral antero-

lateral ligament

hepatic artery \ g

jyentral medio-

i~ late

ral ligament

[Wu S |

ventral postero-

lateral ligament

en ~

——

bulbus

sternal artery

dorsal abdominal artery

Fic. 48. Ventral view of heart.

THE ANATOMY OF THE CAPE ROCK LOBSTER 139

gland, the dorsal postero-lateral ligament originates close to the antero-lateral

margin of the pericardial pouch (fig. 9). The more fragile dorsal medio-lateral

ligament arises on the epimeron above and approximately midway between

the anterior and the middle branchio-pericardial orifices and passes hori-

zontally over the deeper thoraco-abdominal muscle. The three ventro-lateral

ligaments underlie the dorso-lateral bands and have strong attachments at

intervals in the midst of the alary muscles of the pericardial septum.

In addition to the above, there are several short, mid-dorsal threads

extending between the roof of the pericardial cavity and the wall of the heart,

and associated with the sides of the bulbus arteriosus are a number of fibres

probably comparable to the paired posterior ala cordis of Cancer (Pearson,

1908) and the ligamentia ventralia indicated by Baumann (1921) in Astacus.

(d) Inner structure of the heart

The lumen of the heart is covered by a relatively thin dorsal wall, com-

posed of a spongy network of rather fine muscles. Ventrally there are sets of

stronger cardiac muscles (fig. 49) which branch and interlace in the lumen

and curve upward into the lateral and dorsal walls. The arrangement seems to

be more complex than in the heart of Astacus, in which Baumann (1921) dis-

tinguished a main longitudinal musculus obliquus cordis and a group of trans-

ophthalmic artery

antennary artery

ventral valves

hepatic valves

lateral ostium

ventral ostia

bulbus arteriosus

ventral valve

Fic. 49. Impression of cardiac muscles, after removal

of dorsal wall of heart.

140 ANNALS OF THE SOUTH AFRICAN MUSEUM

verse musculi frontales. In the heart of Zasus there is no continuous longitudinal

muscle, but several separate bundles are slanted antero-posteriorly, and all the

strands are so organized that none traverses the perimeters of the ostia.

The anterior muscles, which may be analogous to the musculi frontales of

Astacus, arise between the hepatic arteries and form the boundaries of niches

for these vessels and also for the ophthalmic and antennary arteries and the

dorsal ostia. In the middle third of the heart the muscle strands are more or

less obliquely transverse before and behind the level of the lateral ostia and

demarcate recesses for these and the ventral ostia. The muscles in the posterior

third are longitudinally arched and define a comparatively deep ventral space

leading into the bulbus arterious. All the recesses occasioned by gaps between

the muscles communicate widely with the central lumen during diastole, and

it seems likely that the disposition of the muscles and their contraction at

systole ensures a balanced distribution of blood to the various arteries.

2. ARTERIAL SYSTEM

From the anterior end of the heart there arise five arteries: a median

ophthalmic (cephalic of Pearson, 1908; Aorta mediana of Baumann, 1921;

carotid artery of Brody & Perkins, 1930), a pair of antennary arteries (lateral

arteries of Pearson; Arteriae laterales cephalicae of Baumann), and a pair of

ventro-lateral hepatic arteries. Posteriorly there is a slight bulbus arteriosus in

which the dorsal abdominal artery (posterior aorta of Pearson; Arteria dorsalis

pleica of Baumann) and the sternal artery (descending artery of Pearson and

Baumann) originate. Guarding the exit of each of the five anterior arteries is

a dorsal and a ventral, partly muscular, semilunar valve, and a similar pair of

valves occurs at the distal end of the bulbus arteriosus immediately in front of

the origin of the sternal and the dorsal abdominal arteries (fig. 49).

(a) Ophthalmic artery (Figs 10, 31, 46-51, 58, 64, 78)

This median vessel passes directly forward from the heart in the mid-dorsal

line and, after running between the right and left mandibular posterior adductor

muscles, it continues over the dorsal surface of the fore-gut, where it lies

immediately beneath the dorsal body wall. Anteriorly it proceeds between the

paired anterior gastric and the posterior basal eye muscles and dilates into a

sort of accessory heart. This local enlargement (figs 50, 64) has been described

by Baumann (1921) as the cor frontale and as the dilatation of the carotid artery

by Brody & Perkins (1930). In asus it is suspended to the wall of the head close

to the insertions of the posterior basal eye muscles by a pair of fibrous strips,

and it is likely that compression of the cor frontale by these muscles drives the

blood into the more anterior vessels.

Passing forward from the cor frontale, the now appreciably narrower

ophthalmic artery curves abruptly downward and enters the median cylinder

of the fused eyestalks, where it divaricates into a pair of conspicuous optic

arteries (figs 50, 71, 74). Each of these is directed horizontally into the eyestalk

THE ANATOMY OF THE CAPE ROCK LOBSTER I41I

in cntemnsloy

right antennary

left antennary-

tegumentary d

ant. renal

QV cor frontale

anterior gastric

ant. intestinal

epimeral

branchiostegal

left genital

tegumentary b

dorsal abdominal

anterior intestinals

lateral abdominal

telso-uropedal

Fic. 50. Dorsal view of arterial system.

142 ANNALS OF THE SOUTH AFRICAN MUSEUM

and, running anterior and parallel to the optic nerve, it enters the optic cup

within which it branches to the optic ganglia. (Some details of the ramifications

of the optic artery are given later (pp. 194-196) in the description of the com-

pound eyes.) In Jasus there is no evidence of the continuation of the median oph-

thalmic artery in front of the optic arteries to form minor antennulary arteries,

such as have been traced in Astacus by Baumann (1921), but astout cerebral artery,

which ramifies profusely in the brain, is given off ventrally from the cor frontale.

(b) Antennary arteries (figs 10, 31, 38, 39, 46-51, 78)

Arising antero-laterally from the heart on each side of the median ophthal-

mic artery there is a conspicuous antennary artery, which courses forward and

outward, dividing repeatedly to irrigate many parts of the cephalothorax. It

may be regarded as having three major branches, the epimeral, the ramus

internus, and the ramus externus.

The epimeral artery (fig. 50) is a substantial vessel originating dorsally close

to the root of the antennary artery. It has been so called because it passes

laterally below the medial bundle of the lateral thoraco-abdominal muscle

and proceeds under the branchio-cardiac groove to the epimeral attractor

muscle. It not only supplies the latter, but also gives off several lateral branches

which ramify extensively in the branchial lining of the branchiostegite and

these have, therefore, been termed the branchiostegal arteries (fig. 50). This

profuse vascularity of the branchiostegal membrane and Calman’s (1909)

statement that in Decapoda the blood from a minor circulation in the branchio-

stegites is returned to the pericardium, suggest that the inner lining of the

branchiostegite has a possible inherent respiratory function. In injected adult

specimens of Yasus and in transverse sections of the puerulus stage the portal of

entry of the stream returning from the branchial membrane to the pericardial

cavity is difficult to detect with certainty, but its most likely position is at the

postero-lateral corner of the pericardial cavity near its junction with the

pericardial pouch.

Posteriorly the main epimeral artery curves medially, giving off a rather

delicate medial tegumentary artery (tegumentary a, fig. 50) to the hypodermis in

the hinder part of the cardiac region of the cephalothorax before anastomosing

with the epimeral artery of the opposite side towards the posterior limit of the

pericardial cavity. From this transverse anastomosis there arises a pair of

fairly stout tegumentary arteries (tegumentary b, fig. 50) which pass vertically

upward to the muscles of the pericardial pouch and the integument behind the

pericardial cavity.

Ramus internus. While proceeding forward parallel and anterior to the

curvature of the cervical groove, the main antennary trunk gives rise to a

delicate medio-dorsal tegumentary artery and one or more comparatively strong

epimeral arteries to the anterior part of the epimeral attractor muscle. It then

becomes divisible into two main branches opposite the posterior adductor

muscle of the mandible; these are similar to the ramus internus and the ramus

THE ANATOMY OF THE CAPE ROCK LOBSTER 143

externus defined by Baumann (1921) in Astacus.

The ramus internus (fig. 50) passes off medially from the main stem and

traverses the posterior bundle of the mandibular posterior adductor muscle,

to which a number of small twigs are given off. It then constitutes the posterior

gastric artery (fig. 50) which divides into an intricate network of vessels to the

muscles of the pyloric fore-gut and the posterior part of the cardiac region of

the fore-gut. The indications are that the left posterior gastric artery is usually

more widespread than the one on the right side, its posterior offshoot continuing

towards the mid-dorsal line of the pyloric fore-gut where it bifurcates into

right and left branches. Both branches supply the mid-gut and the beginning

of the hind-gut in the cephalothorax, but the right branch may extend along

the hind-gut as an anterior intestinal artery (figs 50, 51) which subdivides to

supply the wall of the intestine approximately as far as the third abdominal

segment.

Ramus externus. The residual part of the antennary artery is the ramus

externus (fig. 50) which courses laterally through the cephalothorax, giving

off several arteries to neighbouring tissues including the hypodermis (tegu-

mentary ¢, fig. 50), and eventually terminates in distal branches to the antenna,

the antennule, and the eye muscles. It is thus more extensive than the ramus

internus, and comprises the following main vessels.

The anterior gastric artery (figs 50, 51) is less conspicuous than the posterior

gastric branch of the ramus internus and is the terminal part of a fairly wide

vessel which passes off medially from the ramus externus and runs between the

hypodermis and the antennal promotor muscle, both of which it supplies.

Continuing medially towards the procephalic process, it separates into several

small tegumentary arteries (tegumentary d, fig. 50) in the rostral region and a

larger vessel that extends across the anterior end of the anterior gastric muscle

and then curves ventrally towards the cardiac fore-gut.

Mandibular and oesophageal arteries. The blood supply to the muscles of the

mandible is derived from at least three different sources. Close to the separation

of the ramus externus from the ramus internus, a short artery enters directly

into the anterior bundle of the mandibular posterior adductor muscle (fig. 50).

The minor abductor and the anterior and posterior lateral adductor muscles

are supplied by vessels which spring from the ramus externus proximal to the

renal arteries. The remaining mandibular muscles are served by a large artery

which is a prominent lateral branch of the ramus externus. It is indicated in

figure 50 opposite the level of the first pereiopod, whence it bends latero-

ventrally between the anterior and the dorsal lobes of the digestive gland and

extends below the former into the concavity of the mandible to reach the

anterior adductor and the major abductor muscles. This distribution of blood

to the mandibular muscles is obviously different from that observed by Bau-

mann (1921) in Astacus, in which the mandibular artery is a branch of the

subneural artery.

An examination of serial sections of the puerulus stage demonstrates that

144 ANNALS OF THE SOUTH AFRICAN MUSEUM

a delicate oesophageal artery continues forward in front of the branches to the

inner mandibular muscles and conveys blood to the oesophagus and the lab-

rum. This arrangement is probably normal, for Baumann (1921) has shown

that in Astacus an oesophageal artery separates from the anterior end of the

mandibular branch of the subneural artery and forms a peri-oesophageal ring.

Renal arteries. At least two fairly wide vessels may be traced from the ramus

externus to the antennal gland. They have been called the posterior and the

anterior renal arteries and respectively appear to be comparable with the sac-

cular and the anterior renal arteries described by Marchal (1892) and Baumann

(1921) in other decapods. The posterior renal artery, which has been omitted in

figure 50 but is represented in figure 39, is a short stout vessel that arises

ventrally from the ramus externus. It penetrates the main lobe of the labyrinth

and becomes associated more particularly with the central cavity of the end

sac (fig. 40). The anterior renal artery (figs 39, 50) originates more dorsally on

the ramus externus and its branches ramify in the white lobe of the labyrinth

but, like those of the posterior renal artery, they invade the spaces between the

epithelial walls of the end sac and the labyrinth.

Dissections of the antennal gland (figs 38, 39) reveal the presence of at

least one branching vesicular artery to the wall of the bladder and another which

passes to the ureter and also supplies the antennal remotor muscle. In several

species of Decapoda Marchal (1892) observed that part of the antennal gland

was irrigated from the subneural artery by a branch which he termed the

posterior renal artery. Baumann (1921) also described a similar artery in

Astacus, but no such remote source of arterial blood to the antennal gland was

detected in 7. lalandit.

The antennary artery proper (fig. 50) separates laterally from the anterior

end of the ramus externus. It is a moderately wide vessel which courses through

the antennal peduncle more or less medial to the antennary nerve; it supplies

the various muscles in each peduncular segment and ends in the flagellum.

Beyond the origin of the antennary artery proper, the terminal portion

of the ramus externus travels horizontally inward, and towards the mid-line it

produces a rather thick antennulary artery (fig. 50). This bends acutely forward

to enter the antennulary peduncle, through which it travels lateral to the

antennulary nerve and eventually bifurcates into the two flagella.

Oculomotor artery. Baumann’s (1921) observation, that in Astacus the anten-

nulary and oculomotor arteries are branches of a common stem, is substantiated

in serial sections of the puerulus stage of 7. lalandii. It is apparent that the two

vessels represent the somewhat disproportionate terminal bifurcation of the

ramus externus, the slender oculomotor artery diverging just as the more

conspicuous antennulary vessel curves into the base of the antennulary peduncle.

The right and left oculomotor arteries turn rather abruptly upward close to

each other in front of the brain and between the promotor muscles of the two

antennules, to which a number of twigs seem to be given off. Each artery then

curves outward and courses laterally backward above the brain, running for

THE ANATOMY OF THE CAPE ROCK LOBSTER 145

a short distance along the side of the apical muscle before entering the eyestalk

lateral to the optic nerve or pedunculus lobi optici (fig. 58). Its route through

the eyestalk is not easily followed in injected specimens, but serial sections of

the adult eye indicate that it consists essentially of two main branches: one

supplies the adductor and medial retractor eye muscles and the other the

remaining eye muscles and, in addition, both terminate in fine vessels in the

subretinal connective tissue. It is thus evident that, as in Astacus (Baumann,

1921), there are two independent supplies of blood to the eye, one from the

median ophthalmic artery via the optic artery to the optic ganglia, and the

other to the eye muscles from the oculomotor branch of the antennary artery.

On the whole, the picture presented by the extensive ramifications of the

antennary artery is fundamentally similar to that of Astacus astacus (Baumann,

1921) and Palaemonetes vulgaris (Brody & Perkins, 1930). In these two species,

however, there is a fairly obvious supply from the antennary artery to the

gonads, but in Jasus this seems to be of minor importance. Only a very short

and inconspicuous anterior genital artery (fig. 51) passes off ventrally from the root

of the antennary trunk and is supplemental to an equally small genital branch

from the proximal part of the hepatic artery (fig. 51).

anterior gastric artery

cardiac fore-gut

10 mm.

a Om

y, Ki HM

ANN

Ms )

if i

anterior lobe

mandibular post

adductor muscle

dorsal lobe

ophthalmic artery

antennary artery

anterior genital

Grvemnes

hepatic artery

ant. intestinal

artery

dorsal abdominal

artery

Fic. 51. Side view of dissected right digestive gland, showing

ramifications of hepatic artery.

146 ANNALS OF THE SOUTH AFRICAN MUSEUM

This pair of blood vessels arises ventrally from anterior the end of the

heart almost directly below the antennary arteries and can only be seen satis-

factorily in a lateral dissection and preferably in an injected specimen.

On leaving the heart, they proceed obliquely downward and outward,

passing between the paired gonads immediately behind their transverse con-

necting bridge and frequently becoming obscured by the enlarged ovaries in

mature females. On its course, each gives off a fine anterior genital artery (fig. 51)

to the beginning of the posterior half of the gonad before it travels more

ventrally to penetrate into the digestive gland approximately at the junction

of the dorsal and posterior lobes and close to the entrance of the hepatic duct

into the mid-gut (fig. 37). Shortly after entering the digestive gland, the hepatic

artery divides into three large branches, one to each of the lobes of the gland,

within which a complex network of vessels is formed.

(d) Dorsal abdominal artery (Figs 10, 31, 46-48, 50, 51, 54, 77, 78)

Beginning at the posterior extremity of the bulbus arteriosus at the hinder

end of the heart and outside the pericardial cavity, the dorsal abdominal artery

passes mid-dorsally through the posterior region of the cephalothorax, where

one pair of arteries, the genital, is given off. It continues down the length of the

abdomen above the hind-gut, and produces regular segmental lateral abdominal

arteries which supply most of the abdominal muscles and the abdominal

appendages.

Genital arteries. Some previous mention has been made of subsidiary genital

vessels from the antennary and the hepatic arteries, but the main supply to the

gonads is derived from a pair of genital arteries (fig. 50) which leave the dorsal

abdominal artery immediately behind the bulbus arteriosus. As in Astacus

(Baumann, 1921), the two of the pair are variable in size and distribution, the

right genital artery (figs 47, 48, 50) being almost consistently larger than the

one on the left side. Both genital arteries pass outward, branching repeatedly

to supply the posterior half of the gonads and the gonoducts. The right genital

artery, however, continues laterally, coursing dorsally over anterior oblique

muscle 1 and sending tributaries, not only to this muscle, but also to posterior

oblique 1, to oblique transverse 1, and to the lateral part of the anterior thoracic

muscle.

On the left side, where the more delicate genital artery appears to terminate

in the reproductive organs, it was observed in some specimens that the supply

to the left thoracic musculature was derived from a stout branch arising from

the sternal artery midway between the heart and the sternal canal (fig. 31).

This muscular artery also occurs as a branch of the sternal artery in the puerulus

stage, the muscles of the right side being irrigated by a more conspicuous artery

which originates separately behind the bulbus arteriosus at the beginning of the

dorsal abdominal artery and probably represents the future right genital artery

of the adult.

THE ANATOMY OF THE CAPE ROCK LOBSTER 147

Lateral abdominal arteries (fig. 50). In each abdominal segment the dorsal

abdominal artery gives off a pair of broad, lateral vessels which penetrate

between the dorsal extensor and the more ventral flexor muscles, sending

branches to the muscles and even to the pleopods. The distribution of the

vessels is by no means symmetrical on both sides, nor is it identical in. successive

segments, but in general three main branches are apparent. A medial branch;

which passes downward to supply the central and the anterior oblique muscles,

usually arises towards the proximal end of the lateral abdominal artery. An

antero-lateral branch becomes defined by the bifurcation of the lateral abdominal

artery beyond the medial branch. This vessel provides the main supply to the

superficial and deeper extensor muscles by an intricate system of ramifications.

A relatively wide and extensive postero-lateral branch represents the outermost

prolongation of the lateral abdominal artery. After passing between and irri-

gating the auxiliary and the anterior oblique muscles, it proceeds laterally

to the pleural region, where it divides into at least two main arteries. One, the

pleural, runs chiefly to the larger proximal muscles of the pleopod, while the

other, herein termed the pleopedal (fig. 50), enters the protopodite of the pleopod

and breaks up into several vessels, some of which extend into the lamellate

exopodite and endopodite. This somewhat peculiar and remote origin of the

supply of arterial blood to the ventral pleopods from the dorsal abdominal

artery appears to be fairly characteristic of decapod Crustacea, for it has

also been described for Homarus (Herrick, 1911), Astacus (Baumann, 1921),

and Palaemonetes (Brody & Perkins, 1930).

The arrangement of vessels in the first abdominal segment departs slightly

from that in other segments in that there are no pleopods and the postero-

lateral branch of the lateral abdominal artery ends in the pleuron. This, how-

ever, is Consistent with the findings in other Decapoda in which, even when,

as in Astacus (Baumann, 1921), appendages are present on this segment, the

lateral abdominal artery passes only to the pleuron, and the first pair of abdo-

minal appendages is supplied from the subneural artery and not from the dorsal

abdominal vessel as are the other pleopods.

The antero-lateral branch in the first abdominal segment produces a

somewhat prominent antero-dorsal artery, which extends forward into the

cephalothorax and divides into sundry vessels to the lateral and deeper thoraco-

abdominal muscles. Furthermore, in some specimens a delicate branch was

observed to arise close to the root of each first lateral abdominal artery and was

traced into the cephalothorax below the pericardial septum to the posterior

part of the gonad.

As in other genera described by Herrick (1911), Baumann (1921), and

Brody & Perkins (1930), on entering the sixth abdominal segment the dorsal

abdominal artery bifurcates into a pair of conspicuous lateral trunks, each of

which almost immediately gives off a branch which travels over the surface of

the anterior oblique muscle and supplies the large auxiliary muscle. The two

trunks then gradually diverge on either side of the intestine, each passing out-

148 ANNALS OF THE SOUTH AFRICAN MUSEUM

ward towards the antero-lateral margin of the telson under the anterior oblique

muscle, to which and also to the ventral flexor muscle of the telson tributaries

pass off. The postero-lateral extent of the trunk, which may be termed the

telso-uropedal artery (fig. 50), after dividing to serve the anterior and posterior

flexors of the telson and the telso-uropedal muscles, continues into the protopo-

dite of the uropod and eventually reaches both the exopodite and the endopodite

of this appendage.

According to Baumann (1921), numerous intestinal arteries branch from

the dorsal abdominal and also from the segmental lateral abdominal arteries

in Astacus, but in JZasus there is no regular segmental supply to the hind-gut.

Instead, there may be either a median intestinal artery from the posterior

bifurcation of the dorsal abdominal artery or, more commonly, a pair of fairly

obvious posterior intestinal arteries (fig. 50) originates ventrally on the last lateral

abdominal arteries. The paired arteries extend forward, closely adherent to

the dorso-lateral wall of the intestine, the one on the left side usually travelling

as far as the third segment, while the right one may be shorter and end in the

fourth segment. These vessels provide arterial blood to the caudal part of the

intestine, the proximal portion of which is served by the anterior intestinal

arteries (p. 143) derived from one of the posterior gastric arteries.

(e) Subneural arteries (Fig. 52)

A mid-ventral system, which is situated below the ventral nerve cord and

is of special importance in distributing arterial blood to the ventral nerve cord

and the thoracic appendages, is formed by divarication of the lower end of the

very wide sternal artery. The latter (figs 31, 46, 48) is directed vertically down-

ward from the bulbus arteriosus at the posterior end of the heart and runs either

to the left or to the right of the intestine. Some investigators have indicated that

the sternal artery is originally paired, and the variability of its position relative

to the intestine in the adult is doubtless caused by the irregular suppression

of one or the other of the two vessels. The sternal artery passes between the

mesophragms of the endophragmal skeleton and, entering the sternal canal

(fig. 31), it penetrates the ventral nerve cord between the connectives joining

the third and fourth thoracic ganglia. Having thus attained a subneural posi-

tion, it immediately divides into anterior and posterior branches, which are

usually respectively termed the ventral thoracic and the ventral abdominal arteries,

and are best seen in injected specimens that have been dissected mid-ventrally

between the appendages (fig. 52).

The anterior subneural or ventral thoracic artery (figs 31, 52, 53) is subequal

in diameter to the sternal artery as it proceeds forward giving off stout, paired

vessels to the third, the second, and the first pereiopods, and the third maxilli-

peds (fig. 52). Anterior to the latter, the median artery, which has become

progressively narrower, bifurcates; each fork sends offshoots into the second and

the first maxillipeds and then curves laterally to irrigate the second and the

first maxillae.

THE ANATOMY OF THE CAPE ROCK LOBSTER 149

mandible:

1st maxilliped

2nd maxilliped

ventral thoracic artery

pedal artery

position of sternal artery

segmental

ventral abdominal artery Bena

pleopods

arteries to superficial

ventral muscles

cat eens ine Ud Ss

)\ TAS

x / i \

sd HL )

Fic. 52. Ventral view of subneural arteries in male specimen.

anus

\ ye

Unlike Astacus (Baumann, 1921) and Palaemonetes (Brody & Perkins, 1930),

the ventral thoracic artery does not continue forward into the mandible, nor

apparently does it reach the oesophagus: as indicated on page 143, these parts

derive their blood supply from the mandibular branch of the antennary artery.

Moreover, the point of bifurcation of the anterior end of the ventral thoracic

artery seems to be variable for, according to Brody & Perkins (1930), it takes

place in Palaemonetes in front of the first pereiopods. On the other hand, Bau-

mann (1921) has shown that in Astacus the subneural artery is a continuous

median vessel from which the first maxilliped and the two maxillae on each

side receive blood from divisions of a common lateral branch, while more

150 ANNALS OF THE SOUTH AFRICAN MUSEUM

anteriorly the main artery terminates in the mandibular muscles and in the wall

of the oesophagus.

In addition to supplying the anterior thoracic appendages, Baumann

(1921) demonstrated that in Astacus, close to its origin from the descending

(sternal) artery, the rostral part of the subneural artery sends a pair of vessels to

the anterior thoracic muscles. Similar vessels also occur in Jasus, but usually two

additional pairs are present in front of these, and all of them extend upward

and spread into the anterior thoracic muscles.

The posterior subneural or ventral abdominal artery (figs 31, 52, 54) supplies

the fourth and fifth pereiopods and then passes mid-ventrally along the abdo-

men. Commonly in each segment it produces two pairs of rather weak vessels

to the superficial ventral muscles: the more conspicuous pair underlies the

dorso-lateral nerves to the main abdominal muscles, and the subsidiary pair

occurs more anteriorly, approximately in the middle of the segment. Towards

the posterior extremity of the abdomen, the median vessel gradually becomes

more attenuated, and in front of the anus several branches are given off to the

flexor muscles of the telson and to the anal compressor and the anal dilatator

muscles. Anterior to these there may be an anastomosis with the last pair of

lateral abdominal arteries of the dorsal abdominal system, the arrangement

being reminiscent of the peri-intestinal ring described by Baumann (1921)

in Astacus.

The whole of the ventral nerve cord is richly supplied with oxygenated

blood by short vessels arising irregularly along the course of both the ventral

thoracic and the ventral abdominal arteries, the branches to the thoracic

ganglia (fig. 53) being particularly noticeable.

3. VENOUS SINUSES

It is apparent in injected adult specimens and in sections of the puerulus

stage that the haemal sinuses are provided with delicate limiting membranes

and that they form a system of wide, interconnected spaces surrounding the

viscera, including the arteries and nerves passing to various parts of the body.

In the head region a spacious sinus, which encompasses the brain (fig. 58),

the circum-oesophageal connectives, the antennal glands, the beginning of the

fore-gut, and the anterior lobe of the digestive gland, collects blood anteriorly

from the eyes, the antennules and the antennae, while the venous spaces of the

labrum, the mandibles, and the first maxillae open into it ventrally.

More posteriorly, the cephalic apodeme of the endophragmal skeleton

marks the transition from the head to the thoracic region of the body and the

division of the haemocoel into dorsal and ventral compartments. Thus, through-

out most of the thorax a sternal sinus (fig. 53) becomes defined around the

ventral nerve cord and the subneural artery in the sternal canal, and at its

anterior end it receives deoxygenated blood from the second maxillae. Con-

nected with the sternal sinus through interstices in the endophragmal skeleton,

but separated from it at intervals by the transverse mesophragms, is the dorsal

THE ANATOMY OF THE CAPE ROCK LOBSTER I5!

sinus, which envelops the fore-gut and is laterally continuous with the hepatic

sinus around the dorsal lobes of the digestive gland and also with the venous

spaces in the branchiostegites and the anterior part of the genital sinus. In the

cardiac region of the thorax (fig. 53) the large dorsal sinus lies below the peri-

cardial septum and surrounds the beginning of the hind-gut, the posterior lobes

of the digestive gland, and the gonads.

pericardial cavity

lateral thoraco-abdominal muscle

deeper thoraco-abdominagl muscle

intestine epimeron

digestive gland pericardial septum

Gnterior thoracic muScle dorsal Sinus

branchiostegite = ] \ = s Se Mp "i branchio-pericardial vessel

epipodite

efferent branchials

pleurobranch afferent branchials

posterior arthrobranch infrabranchial Sinus

branchial sinus

second pereiopod

ventral nerve cord

= pedal sinus

i endopleurite pedal nerve

endosternite

mesophragm

Pedal artery

Sternal sinus

ventral thoracic artery

Fic. 53. Puerulus stage: diagrammatic transverse section through fifth thoracic segment. To

give clearer definition to the arrangement of the gills, the gill filaments have been omitted;

l.p.n., longitudinal ventral pericardial nerve, size exaggerated.

dorsal! sinus

dorsal abdominal artery

intestine

anterior oblique muscle

central column

jor bligue muscle

posterior o 4g dorso-lateral nerve

Superficial ventral muscle pleural sinus

‘ww

ventral nerve cord ventral abdominal artery

left pleopod right pleopod

Fic. 54. Puerulus stage: diagrammatic transverse section through third abdominal segment;

l.a.n., somewhat enlarged longitudinal arterial nerve.

152 ANNALS OF THE SOUTH AFRICAN MUSEUM

These two main thoracic sinuses are directly continuous with similar blood

spaces in the abdomen, in each segment of which (fig. 54) the median dorsal

sinus lies above the anterior oblique muscles and contains the dorsal abdominal

artery and the intestine, while the sternal sinus, situated beneath the oblique

muscles, encloses the ventral nerve cord and the ventral abdominal artery. In

addition, each abdominal segment has a pair of pleural sinuses (fig. 54) which

drain the deoxygenated blood from the paired appendages in the second to the

sixth segment, but the blood from the telson enters the end of the dorsal abdomi-

nal sinus. The four abdominal sinuses are linked together by channels running

between the large abdominal muscles, from which blood is also collected.

4. BRANCHIAL CIRCULATION

The deoxygenated blood in the haemocoel must eventually be conveyed

to the respiratory organs for oxygenation, and Huxley’s dictum (1881:69) that

in Astacus ‘all the blood in the body sooner or later makes its way . . . into the

sternal sinus’ . . . from which . . . ‘passages lead to the gills’, seems to have been

accepted as the standard for all Decapoda. It is considered, however, that in

Jasus the circuit to the gills differs somewhat from this concept of events in the

crayfish, and that it bears some resemblance to the circulation in Cancer, in

which Pearson (1908) described a series of branchial sinuses for the transport of

blood through the pleural muscle chambers of the appendages en route to the

gills.

The thoracic sternal sinus of Fasus (fig. 53) is considerably smaller than

the dorsal sinus, which is in line with the pleural muscle chambers, but the two

sinuses communicate freely through gaps in the endophragmal skeleton. An

examination of serial sections of the puerulus stage suggests that the greatest

volume of blood is directed towards the gills, not from the sternal sinus, but

from the dorsal sinus by relatively wide and distinct branchial sinuses (fig. 53)

located in the pleural muscle chambers of the limb bases. At the same time,

vessels passing from the sternal sinus traverse the sternal muscle chambers and

communicate more particularly with the pedal sinuses (figs 53, 55) which return

deoxygenated blood from the appendages. Paired branchial sinuses are apparent

in all thoracic segments, except the first, and on each side of the body they and

the pedal sinuses become associated with a longitudinal infrabranchial sinus

(figs 53, 55) which runs along the bases of the gills from the second to the last

thoracic segment and seems to end in the articular condyle for the carapace.

In the absence of a branchial sinus in the first thoracic segment, the blood from

the first maxilliped and the dorsal and ventral sinuses passes directly into the

anterior end of the infrabranchial sinus. The paired pedal sinuses in the last

thoracic segment not only join the right and left infrabranchial sinuses, but

some of the pedal blood may also enter the stream flowing forward from the

sternal and pleural sinuses in the intersegmental region between the abdomen

and thorax. The reason for this appears to be that the sternal canal does not

extend to the end of the thorax, and thus in the floor of the last thoracic segment

THE ANATOMY OF THE CAPE ROCK LOBSTER 153

there is a wide confluence of ventral abdominal and thoracic blood, including

some passing through the sternal muscle chambers of the last pair of pereiopods.

last pleurobranch posterior arthrobranch

last branchial sinus

anterior arthrobranch

dorsal sinus pleurobranch

intersegmental afferent branchial vessel

pleural sinus ——————-—+

. .

sternal sinus

infrabranchial sinus ge 2 . 7 Y,5 ~ ) po. epipodite

pedal sinus

10 mm.

pereiopod 3

Pereiopod 5

afferent branchial vessel

podobranch

Fic. 55. Side view of right posterior gills; the epipodite and podobranch of the seventh thoracic

segment have been displaced, and the course of the afferent branchial vessels is shown.

From each infrabranchial sinus the deoxygenated blood proceeds into a

series of 21 afferent branchial vessels (figs 44, 53, 55, 56) running along the outer

part of the axes of the serially-arranged gills in the second to the eighth thoracic

segments. Each epipodite (fig. 55) is also furnished with a vessel which arises

as a branch of the afferent branchial to the corresponding podobranch, and in

serial sections of the puerulus stage it is also evident that an afferent vessel passes

from the anterior end of the infrabranchial sinus into the epipodite of the first

maxilliped.

By serial sections of the gills and observations of injected specimens, it

can be shown that offshoots from the afferent branchial vessel traverse the

lateral mantle canals and, radiating into the gill filaments, convey deoxyge-

nated blood into the outer afferent channels in the filaments (fig. 44). The wall of

each filament functions as a respiratory membrane and, after oxygenation, the

blood enters the efferent channel (fig. 44.) which lies on the inner side of the filament

and is separated from the afferent channel by a longitudinal connective-tissue

septum. The actual transition from the afferent to the efferent channel is

problematic. Bock (1925) concluded that in Astacus it could only be established

through blood lacunae at the apex of the filament but, according to Dornesco &

Homei (1940), it may occur in Palinurus along the length of the filament through

irregular spaces formed between the epidermis and the median septum. The

feasibility of the latter suggestion is supported by inspection of the gills of Jasus,

154 ANNALS OF THE SOUTH AFRICAN MUSEUM

in which injected India ink successfully delineated the whole course of the

afferent blood stream: carbon particles, which fill the axial afferent branchial

vessel and the filamentar afferent channels, fail to penetrate into the filamentar

efferent channels, but irregular traces are evident in lateral lacunae beneath the

epidermis of the filament. It is also of some significance that in all the gills the

afferent channels are given off only to the outer filaments adjacent to the afferent

branchial vessels and that the zmner filaments (fig. 44), which are opposite the

efferent branchial vessel, receive no blood directly from the afferent branchial

vessel. Characteristically, there are fewer inner than outer filaments and the

two are sharply contrasted in injected specimens by the absence of injection

fluid in the inner filaments. Thus, for instance, in sections across the widest part

of the pleurobranch (fig. 44) there are usually three pairs of inner filaments and

about fourteen pairs of outer filaments, although the number of the latter has

been reduced by about one third in the given simplified diagram.

Assuming that the lateral lacunae mark the junction between the afferent

and efferent streams and that in them gaseous exchange takes place, the blood

oxygenated in the outer filaments will drain into and proceed along the efferent

channels. Before it eventually reaches the efferent branchial vessels (fig. 44) on the

inner side of the gill axis, however, it describes a somewhat tortuous course

through the gill axis and the remaining inner gill filaments. In this connexion,

the two mantle canals (fig. 44.) running along the sides of the afferent and efferent

branchial vessels are of supreme importance. Into them the efferent channels

from the outer filaments discharge directly, and the blood is then transported to

the inner filaments which have passages analogous to the afferent and efferent

channels of the outer filaments. The blood directed from the mantle canals into

the afferent channels of the inner filaments traverses the superficial lacunae and

enters the corresponding efferent channels, which in turn open widely into the

efferent branchial vessel. Since, however, the blood has presumably already been

oxygenated in the outer filaments, it follows that, while circulating through the

inner filaments, it must be subjected to a further process of oxygenation before

it enters the efferent branchial vessel. These observations confirm the conclu-

sions of Bock (1925) and Dornesco & Homei (1940) that the blood is twice

oxygenated on its course from the afferent to the efferent branchial vessel.

Dornesco & Homei, however, have described a further complication in the

branchial circulation of Palinurus, in which a third category of one or more

pairs of filaments is intercalated between the outer and the inner filaments.

Such filaments, which are not apparent in Jasus, are said to have two longitu-

dinal septa dividing the lumen into three channels, the outermost of which

receives the deoxygenated blood from the afferent branchial vessel, while

the middle and the inner passages accommodate the oxygenated blood and

respectively conduct it into the mantle canal and the efferent branchial vessel.

In addition to the main vessels, five narrower, but distinct, blood channels

(a, to a;, fig. 44) are evident in sections of the gill axes and are similar to the

branchial arteries indicated by Dornesco & Homei (1940) in the gills of Palinurus.

THE ANATOMY OF THE CAPE ROCK LOBSTER 155

Two of the three unpaired vessels, a, and a;, are doubtless associated with the

blood lacunae in the loose connective tissue around the efferent branchial

vessel, but they also give off relatively stout lateral branches which seem to pass

into the septa of the inner filaments. From the paired vessels, a, and a3, which

are located in the midst of the loose connective tissue in the wider parts of the

mantle canals, branches travel along the gill axis to the septa of the outer

filaments. The remaining artery, a,, is adjacent to the inner wall of the afferent

branchial vessel but, apart from delicate tributaries to the latter, it appears

to have no obvious connexion with the gill axis.

pericardia! pouch

pleurobranchs

branchio-pericardial orifices

pericardial cavity

cut epipodite of third maxilliped

branchio-pericardial vessels

efferent branchial vessels

arthrobranch

second maxilliped

podobranch

podobranch t

posterior arthrobranch 3 —

anterior arthrobranch ‘GI, ~ ux ; hird maxillip

afferent branchial vessels pereiopods setiferous process

Fic. 56. Diagram of right branchial chamber with the gills removed and the course of the

branchio-pericardial vessels exposed.

In each segment the efferent branchial vessels of the gills and the epipodite

communicate with a branchio-pericardial vessel (figs 53, 56) which travels along

the inside of the thoracic epimeron and conveys the oxygenated blood to the

pericardial cavity. All told, there are effectively seven branchio-pericardial

vessels on each side of the thorax but, as they join in pairs before reaching the

pericardial cavity, only three wide branchio-pericardial orifices (fig. 56) occur

laterally in the pericardial septum. By viewing the pericardial cavity from

above, these may be easily seen, even in uninjected specimens; they are located

in the angles between the epimera and the attachments of certain bundles of the

thoracic muscular system (fig. 11) and are practically in line with the first

three pereiopods. The oxygenated blood entering through the branchio-

pericardial orifices fills the pericardial cavity and is sucked into the heart lumen

through the ostia at each diastolic expansion of the heart; when the cardiac

muscles contract at systole, it is pumped via the arterial system to all parts of

the body.

The complete circulation of the blood may be expressed in the following

synoptic diagram:

I 56 ANNALS OF THE SOUTH AFRICAN MUSEUM

Oxygenation of blood

in outer gill filaments ~

Efferent channels in Afferent channels in

outer gill filaments outer gill filaments

Mantle canals Afferent branchial vessels

in gill axes in gill axes

}

Re-oxygenation of blood Paired infrabranchial sinus

in inner gill filaments

Efferent branchial vessels Branchial Pedal

in gill axes sinuses sinuses

Branchio-pericardial vessels Dorsal sinus ——» Sternal sinus

Branchio-pericardial orifices Tissues & Organs

Pericardial cavity Arteries

~~ -$-——» Heart

One of the main differences between the above interpretation of the blood

circulation and that described by Huxley (1881) for the crayfish is the recogni-

tion of branchial sinuses for the reception of blood from the dorsal thoracic

sinus of the haemocoel. However, by reference to Huxley’s familiar and fre-

quently reproduced diagram, it may be surmised that branchial sinuses similar

to those of Fasus probably also occur in Astacus in the lateral spaces between the

median sternal sinus and the leg bases.

H. Nervous SysTEM

As the greater portion of this system is ventral in position, its full exposure

from the dorsal aspect involves careful removal of most of the contents of the

body cavity and the median part of the endophragmal skeleton. Although in

gross dissections it may be advisable to excise the large thoracic and abdominal

muscles, it should be noted that several important nerves either innervate them

or pass between them to other organs.

In its entirety it is divisible into two subsections, the central nervous system

and the sympathetic nervous system.

The central nervous system comprises an antero-dorsal brain and a ventral

nerve cord consisting of a chain of segmental ganglia running mid-ventrally

down the length of the body and giving off lateral peripheral nerves to the

muscles and occasionally to other organs in each segment.

The delicate sympathetic or stomatogastric nervous system is associated with the

brain, but functions chiefly in the innervation of the fore-gut and a few neigh-

bouring structures.

THE ANATOMY OF THE CAPE ROCK LOBSTER 157

cerebral ganglia

circumoesophdged! connectives

nerves to mandible, |

maxillae & maxillipeds

postoesophageal commissure

suboesophageal ganglion

branches of 1st pedaJ nerve

4st thoracic ganglion

endophrggmal sketeton

2nd thoracic ganglio

passage for sternal artery

3rd thoracic ganglion

4th thoracic ganglion

5th thoracic ganglion branches of 5th pedal nerve

ventral nerve cord

1st. abdominal ganglion

peripheral nerves

pleopedal nerve

Sl dorso-latera| nerve

“WW Oz

ventral nerves

fongitudinal connectives

outer uropedal nerve

inner uropedal nerve

. 3 4 —— = me ae 3

anterior nerve 7 >. j

oh mf dorsal & ventral

telson nerves

; intestine

intestinal nerve

Fic. 57. Dorsal view of central nervous system.

I 58 ANNALS OF THE SOUTH AFRICAN MUSEUM

I. CENTRAL NERVOUS SYSTEM (Fig. 57)

Probably the easiest method of tracing this is to expose the abdominal part

of the ventral nerve cord first by displacing the hind-gut and the abdominal

extensor and flexor muscles. It will then be possible to follow the cord forward

through the cephalothorax by opening the sternal canal and completing the

dissection by displaying the parts in the frontal region.

The brain is situated antero-dorsally in the cephalothorax in front of the

cardiac fore-gut, below the rostrum and between the eyes, while the ventral

nerve cord is composed of a series of thoracic ganglia, lodged in the sternal canal

beneath the mesophragms of the endophragmal skeleton, and of six abdominal

ganglia lying mid-ventrally close to the sterna.

(a) Cerebral ganglia (Figs 31, 57, 58, 61, 64)

. The brain represents a fusion of three pairs of cerebral ganglia, the limits

of which are hardly perceptible in ordinary macroscopic dissections. Transverse

sections (fig. 58), however, disclose the arrangement of various groups of cells,

intricate fibre tracts, and masses of fibrous tissue or neuropiles, and are essential

to the determination of the origins of various peripheral nerves.

basal eye muscles

0.3 mm. J

blood Sinus

oculomotor nerve I oculomotor nerve I

Oculomotor nerve IL oculomotor nerve II

i CEN

WAY

\a\i)

ophthalmic artery

Pedunculus lobi Optici

(optic nerve) :

median & lateral

neurosecretory cells nerveshicfjmediansey®

pons cerebri

roto

oculomotor artery ‘ pe se

cellullae anteriores

Superiores my lobus paracentralis

lobus olfactorius

(deutocerebrum)

antennary nerve

lateral root lobus accessorius (deutocerebrum)

antennulary nerve

medial root

Fic. 58. Puerulus stage: transverse section of brain; provisional terminology after Hanstrém

(1947).

Omitting details of the complex histology of the brain, it may be observed

that, as is characteristic of Malacostraca, it consists of three main regions com-

parable to its pairs of fused ganglia. The anterior protocerebrum (figs 58, 61)

THE ANATOMY OF THE CAPE ROCK LOBSTER 159

innervates the apical muscles, the compound eyes, and the eye muscles; also

connected with it are three short, median, frontal nerves to the median or

nauplius eye (figs 61, 70), and in some species an unpaired superior ventricular

nerve to the stomatogastric system has been reported. The deutocerebrum (fig. 58)

is more ventral, and from it the nerves to the antennules and the statocysts pass

forward and downward. The posterior region of the brain, the ¢ritocerebrum

(fig. 61), gives off the tegumentary and the antennary nerves, and continues

posteriorly as two conspicuous circum-oesophageal connectives which link the

brain with the suboesophageal ganglion at the anterior end of the ventral nerve

cord. The tritocerebrum is also associated with the stomatogastric system by a

median inferior ventricular nerve.

(b) Cerebral nerves

In addition to the nerves of the median eye (fig. 70), the following paired

nerves may be traced on each side of the brain.

A delicate apical nerve (fig. 61) runs forward from the frental edge of the

protocerebrum to the apical muscle situated in the middle cylinder of the

compound eyes. The two of the pair are frequently linked by a transverse

anastomosis above the median eye, which is thus practically embraced by them.

Proximally they are adjacent to the lateral nerves of the median eye (fig. 70),

with which they seem to have either common or contiguous centres in the brain.

The optic nerve (figs 31, 57-59, 61, 71, 74) or pedunculus lobi optict (Hanstrém,

1947) is a very conspicuous trunk originating dorso-laterally in the protocere-

brum. It passes obliquely upward and forward to the eyestalk where it enlarges

into four optic ganglia, some particulars of which are supplied in the description

of the compound eyes (p. 187).

There is no proof that, as in Astacus (Keim, 1915), the anterior and pos-

terior basal eye muscles are innervated from the oculomotor nerves. Instead,

the anterior muscles are clearly served by a pair of delicate nerves (fig. 61)

passing upward from the protocerebrum between the two optic nerves, while

the posterior basal eye muscles seem to be associated with the sympathetic

nervous system. Consequently, as the pulsation of the accessory heart or cor

frontale is probably influenced by the contraction of the basal eye muscles, the

innervation of the latter suggests that the mechanism is partly controlled by the

brain.

In each eyestalk the eye muscles are innervated by two oculomotor nerves

which originate independently of each other in the protocerebrum. Their sub-

divisions are comparable with the three branches of the single oculomotor

nerve of Astacus described by Keim (1915), and more directly with those of the

discrete oculomotor nerves I and II discovered by Welsh (1941) while investi-

gating the physiology of the sinus gland of Cambarus bartonit.

The thicker nerve, oculomotor I (figs 57-59, 61, 71) arises from the lamin

dorso-lateral to the optic nerve; within the eyestalk it passes above the attractor

eye muscle and divides at the base of the optic cup into two stout branches

160 ANNALS OF THE SOUTH AFRICAN MUSEUM

crystalline cone lamina ganglionaris

crystalline cone stalk medulla externa

retinular cells medulla interna

‘i

zone of rhabdomes sinus gland

to connective tissue

neurosecretory cells

sinus gland fibre tract

me"

medulla terminalis

to abductor muscle

, f

to connective tissue

Sinus gland nerve

(SPX & MTGX) lateral retractor muscle

to dorsal retractor

to ventral retractor muscle

oculomotor nerve La

adductor muscle

medial retractor

mm.

oculomotor nerve Ib

oculomotor nerve II

p 8 oculomotor nerve I

optic othe

xX \ \

Fic. 59. Diagrammatic impression of nerves of right eye of adult, based on serial sections and

dissections. The approximate positions of the sinus gland and neurosecretory cells are indicated.

(fig. 59). The sub-branches of these are distributed to the eye muscles in the

optic cup and are often linked by delicate collateral plexuses. Oculomotor I a

supplies the lateral retractor and the abductor eye muscles and extends distally

to the subretinal connective tissue in the dorso-lateral region of the optic cup.

It has a further relatively strong medial branch, which dips ventrally to inner-

vate the ventral retractor eye muscle and gives rise to a long offshoot that travels

below the distal part of the optic nerve and proceeds to the ventro-medial

subretinal connective tissue.

The second branch, oculomotor I b, is equally widespread and, after inner-

vating the medial retractor, the dorsal retractor, and the adductor eye muscles,

it continues distally to the dorso-medial subretinal connective tissue. One of its

most interesting subdivisions is the sinus gland nerve (fig. 59), which passes

forward and penetrates the neurilemma at the base of the medulla terminalis.

In sections of the eye it is possible to trace its deeply stained basophilic fibres

THE ANATOMY OF THE CAPE ROCK LOBSTER 161

through the medulla terminalis; at least three of them enter the sinus gland,

while another strong fibre passes medially towards a plexus around the main

optic tract and approaches the fibre tract that links the X-organ (MTGX) with

the sinus gland.

Oculomotor nerve IT (figs 58, 59, 61, 71) is somewhat finer than the first nerve

and originates from the brain antero-medially to the optic nerve, to the dorsal

surface of which it appears to be partly adherent when examined in sections of

the eye, but in dissections the two are easily separated. Shortly after entering

the medial half of the eyestalk above the optic nerve, it gives off at least two

anastomosing branches which ramify in the attractor eye muscle. It then

curves forward into the basal region of the optic cup where it unites with

oculomotor I } before the latter branches to the sinus gland and the more

medial eye muscles. In supplying the attractor eye muscle, it resembles the

first branch of the single oculomotor nerve distinguished by Keim (1915), but

varies from it in its origin and in having no connexion with the basal eye

muscles.

These findings substantiate Welsh’s (1941) disclosure of two distinct

oculomotor nerves and his speculation as to the presence of a nerve to the sinus

gland, but differ slightly from his observations in that the sinus gland nerve

(fig. 59) is derived mainly from a branch of oculomotor I and not directly

from the second oculomotor nerve as in Cambarus bartoni. As, however, the two

oculomotor nerves anastomose in Jasus, it is feasible that fibres from both of

them contribute to the formation of the sinus gland nerve.

A careful study of serial sections of the puerulus stage shows that, as in

other Decapoda (Balss, 1941; Hanstrém, 1947), the antennulary nerve has medial

and lateral roots (fig. 58) and resolves into branches supplying the statocyst,

the sensory hairs of the antennulary flagella, and the antennulary muscles.

Therefore, unlike the arrangement in Astacus (Panning, 1924) and Homarus

(Cohen, 1955), the fairly substantial statocyst nerve (fig. 60) appears as a branch

of the main antennulary nerve and initially represents its medial root. It is

traceable to the neuropilum antennulare mediale (Balss, 1941) or the lobus

parolfactorius (Hanstr6ém, 1947), and travels in a ventral direction together

with the fibres of the main antennulary nerve. Before reaching the antennulary

peduncle, it divides into several branches, some supplying the tactile hairs on

the proximal segment of the antennule and others terminating in delicate fibres

in the walls of the statocyst. A slight variation in the number of branches to

the statocyst may prevail, four having been observed in one specimen, but,

more commonly, there are only two branches which seem comparable to the

nervi acustici internus and externus of Astacus (Panning, 1924), although these

were described as having separate origins in the brain. In sections there are

also indications that the sensory hairs of the statocyst are innervated by single

neurones.

Arising more laterally from the deutocerebrum, in regions termed the

neuropilum antennulare laterale and lobus olfactorius by Balss (1941), are the

162 ANNALS OF THE SOUTH AFRICAN MUSEUM

rostrum_

apical muscle

pedate process

antennulary nerve a

epimeron--~

antennulary nerve b

mm.

statocyst nerve

promotor muscle

statocyst

aperture Of

statocyst

remotor muscles

statoliths

Fic. 60. Lateral dissection of base of left antennule to show disposi-

tion of antennulary and statocyst nerves. The left antenna and left

compound eye have been excised, and the left apical muscle is

seen in the middle cylinder of the fused eyestalks.

inner and outer fibres of the conspicuous lateral root of the antennulary nerve

(fig 58), from which two well-defined branches later separate. Apparently

originating in the outer fibres, a comparatively thin antennulary nerve a (fig. 60)

provides the main supply to the proximal antennulary muscles; it is directed

forward to the promotor muscle, but also gives off other branches which extend

downward to the remotor and abductor muscles. Emerging from the brain

slightly postero-ventral to the first branch, the inner and outer fibres continue

as a thick antennulary nerve b (fig. 60) which slopes downward through the

frontal region of the head and, curving below the dorsal hinge of the antennule,

enters the peduncle and travels more or less medially, supplying the various

muscles in the three segments. Sections show that throughout their course the

inner and outer fibres of antennulary nerve #b retain their individuality and

separate distally, the inner fibres passing to the inner flagellum, while the

outer fibres terminate in the setae and the aesthetascs of the outer flagellum.

The conspicuous tegumentary nerve (figs 57, 61) arises dorsally in the trito-

cerebrum and splits into several branches, the subdivisions of which fan out to

the antero-lateral cephalic hypodermis.

On displacing the tegumentary nerve, the more ventral antennary nerve

(figs 31, 57, 58, 61) is revealed as a prominent element composed of a number

THE ANATOMY OF THE CAPE ROCK LOBSTER 163

apical nerve medulla terminalis

adductor muscle

oculomotor II medulla externa

apical muscle

protocerebrum

median eye

Sinus gland

lateral retractor muscle

optic nerve

vesicular nerve

tritocerebrum

“fron al “ganglion-

“eesophagea! “‘gangli ions

& ae ole \ se

paroesophagea! gang on cok Pas

“lobral. nerve:

_f outer mandibular verve D> eo : ty

post-oesophageal commissure \7 L Bae Sones Peet one :

Fic. 61. Dorsal view of cephalic portion of central nervous system and part of stomatogastric

nervous system.

of thick fibres springing ventro-laterally from the tritocerebrum. Proximally it

supplies the antennal remotor, depressor, levator, and promotor muscles, and

then proceeds medially through the peduncle, branching from time to time to

the muscles in the three segments.

The innervation of the bladder of the antennal gland is effected by a

delicate nerve (fig. 61) which arises from the root of the antennary nerve in

proximity to the branches to the antennal remotor and depressor muscles. It is

analogous to the vesicular nerve of Astacus which, however, was traced by Keim

(1915) from the tegumentary nerve. It is admitted that several branches of the

latter nerve run close to the wall of the bladder and, although they terminate

more laterally in the hypodermis, there may be very fine connexions between

some of them and the wall of the bladder. Further proof that the tegumentary

nerve is not the source of the supply to the bladder has been provided by

Maluf (1941), whose observations indicate that in Procambarus clarkii it is served

by two sets of fibres derived from the root of the antennary nerve. Chaudonneret

(1956) has also briefly mentioned that in Orconectes limosus (Cambarus affinis) the

164 ANNALS OF THE SOUTH AFRICAN MUSEUM

bladder is innervated by a branch of the antennary nerve, and perhaps further

investigations will establish that this is the rule in most Reptantia. One differ-

ence between Jasus and the few other decapods so far examined by other

investigators is that in a number of dissections a branch of the vesicular nerve

was traced to the labyrinth of the antennal gland and suggests a possible supply

to this part of the organ.

The long and relatively thick pair of circum-oesophageal connectives (figs 57,

61, 62, 64) slope downward from the posterior end of the tritocerebrum below

the cardiac fore-gut, and at the side of the oesophagus each has a fairly obvious

swelling, the commissural or paroesophageal ganglion (figs 31, 61, 64) which is an

important centre of the stomatogastric system. Behind the oesophagus and

practically beneath the cephalic apodeme of the endophragmal skeleton, the

two circum-oesophageal connectives are bridged by a short, narrow, transverse

post-oesophageal commissure (figs 57, 61), from which a pair of small, so-called

post-commissure organs (fig. 61) arises. The connectives then continue into the

sternal canal, where they merge into an elongate suboesophageal ganglion which

marks the beginning of the ventral nerve cord.

(i) The suboesophageal ganglion (Figs 57, 62, 64)

This represents the fusion of at least six pairs of ganglia and gives rise

ventro-laterally to the paired nerves of the mandibles, the first and second

circum-oesophageal connective inner mandibular nerve

Paragnathal nerve

first dorsal nerve first maxillary nerve

second maxillary nerve

Second dorsal nerve

(cardiac inhibitor)

first maxillipedal nerve

suboesophageal ganglion

second maxillipedal nerve

third dorsal nerve

(cardiac accelerator) : \t

longitudinal connective

Ni: f

first thoracic nerve S\ \

third maxillipedal nerve

first thoracic ganglion

second thoracic nerve i

Fic. 62. Rough sketch of dorsal view of anterior part of ventral nerve cord to illustrate origins

of paired nerves.

THE ANATOMY OF THE CAPE ROCK LOBSTER 165

maxillae, and the three maxillipeds. Three additional pairs of dorsal nerves

also originate at intervals along the length of the suboesophageal ganglion

and belong to the neuromeres of certain of the appendicular nerves.

The overall arrangement is consistent with that observed in Astacus by

Keim (1915) and Stoll (1925) and in Orconectes limosus by Chaudonneret (1956).

Stoll also reported the presence of a median oesophageal nerve and a distinct

pair of paragnathal nerves and, although the former has been confirmed by

Chaudonneret, it does not seem to exist in Jasus, in which a slender median

blood vessel occurs in a similar position between the bases of the two circum-

oesophageal connectives. Keim and Stoll further claimed that the labyrinth

of the antennal gland of Astacus was innervated by a nervus glandulae viridis,

but this was not observed either in Procambarus clarkit by Maluf (1941) or in

Orconectes limosus by Chaudonneret (1956) and could not be detected in asus.

Chaudonneret has rightly drawn attention to certain obvious misinterpretations

in Stoll’s identification of the nerves, and his suggestion that Keim has mistaken

the real paragnathal nerve and Stoll the inner mandibular nerve as the supply

to the labyrinth partly clarifies the confusion concerning the distribution of the

anterior nerves from the suboesophageal ganglion.

The mandibular muscles are innervated by distinct inner and outer

nerves which at first sight appear to stem from different levels of the nervous

system, but in serial sections are seen to originate in the same neuromere. The

outer mandibular nerve (figs 61, 64) separates from the circum-oesophageal

connective shortly behind the paroesophageal ganglion; it passes behind the

ventral pyloric dilator muscle and then sweeps outward and forward in front

of the anterior mandibular apodeme before curving backward to the mandibular

lateral adductor muscles. Commenting on the unusual position of this nerve in

Astacus, Keim (1915) suggested that histological investigations might reveal that

it is centred in the suboesophageal ganglion, and this has been verified by

Chaudonneret (1956) in dissections and sectioned material of Orconectes limosus.

In sections of the puerulus stage of asus it can also be seen to originate in the

suboesophageal ganglion, but it is bound up with and inseparable from the

circum-oesophageal connective until it leaves the latter anteriorly near the

paroesophageal ganglion. The remaining mandibular muscles are served by a

comparatively stout znner mandibular nerve (figs 62, 64) which arises more obvi-

ously from the anterior end of the suboesophageal ganglion. It consists initially

of subequal medial and lateral branches which course forward close to the

ventro-lateral surface of the circum-oesophageal connective. After giving off a

nerve to the lower end of the oesophagus, the medial branch bends abruptly

into the cavity of the mandible and divides to the mandibular anterior adductor

muscle and the flexor muscles of the palp. The rather more dorsal and slightly

thinner lateral branch is distributed to the mandibular posterior adductor and

the major and minor abductor muscles, much as in Astacus (Keim, 1915).

The paired paragnathal nerve has been the subject of discussion by Chau-

donneret (1956), who has argued in favour of the recognition of a preman-

166 ANNALS OF THE SOUTH AFRICAN MUSEUM

dibular somite homologous to the superlingual region of Insecta. He has asserted

that the paragnathal nerve of Orconectes limosus arises medial and therefore

anterior to the inner mandibular nerve, but this is not substantiated by obser-

vations of the arrangement in Jasus. Contrary to expectations based on his

conclusions and also on Keim’s (1915) remark that the lower lip of Astacus is

innervated by a branch of the inner mandibular nerve, the latter nerve in

Jasus was found to be unrelated to the supply to the metastoma and paragnaths.

In fact, the paragnathal nerve (fig. 62) has its origin in the suboesophageal

ganglion close to the root of the first maxillary nerve. It is directed forward

adherent to the first maxillary nerve and, separating medially from the branch

to the abductor muscle of the first maxilla, it travels inward below the inner

mandibular nerve and subdivides to the tissues and the muscles of the meta-

stoma and the homolateral paragnath. Making allowance for Stoll’s (1925)

erroneous identification of the first maxillary nerve as the inner mandibular

nerve, the position of the paragnathal nerve of Astacus is suggestive of that of

Jasus, except that in the latter it is medial and not lateral to the first maxillary

nerve. Consequently, it may be inferred that the paragnathal nerve in some

forms, at least, is not so far removed from the first maxillary nerve as Chau-

donneret (1956) has assumed, and there seems little justification for accepting

his hypothesis that the paragnaths represent vestigial appendages of a pre-

mandibular segment.

The nerves to the two maxillae and the three maxillipeds arise in sequence

ventro-laterally from the suboesophageal ganglion (fig. 62) usually by single

roots, but most of them divide almost immediately into two main branches

which travel forward to the coxopodite of the appendage. The large root of the

third maxillipedal nerve originates some distance behind that of the second

maxillipedal nerve in a somewhat distinct posterior section of the suboeso-

phageal ganglion. This may account for the fact that the thoracic part of the

ventral nerve cord of Astacus is sometimes described as a combination of the

suboesophageal and six thoracic ganglia, the first of the latter being set aside

for the sole purpose of supplying the third maxillipeds.

The three pairs of dorsal nerves apparently correspond to the first, second,

and fourth described in fresh-water crayfishes by Keim (1915), Stoll (1925),

and Chaudonneret (1956), and the reason for the suppression in Jasus of the

counterpart of the third dorsal nerve of other forms is obscure. It is obvious,

however, from Keim’s remarks that the fourth dorsal nerve of Astacus is relatively

insignificant and does not participate in the innervation of the dorsal muscles,

while Chaudonneret has stated that the origin of the third dorsal nerve from

the neuromere of the second maxilliped is less distinct in Orconectes than in

Astacus.

The dorsal nerves are of special importance for, not only do they supply

certain thoracic muscles, but the second and the third also contain fibres which,

in combination with neurosecretions, regulate the frequency of the heart beat

and serve respectively as the cardiac inhibitor and the cardiac accelerator nerve.

THE ANATOMY OF THE CAPE ROCK LOBSTER 167

While these and other delicate nerves may be traced in preserved specimens or

in serial sections, they are best displayed by adopting the vital staining tech-

nique recommended by Alexandrowicz (1932) and successfully used by other

physiologists. For this purpose, immature specimens with a cephalothoracic

length of approximately 4:4 cm were anaesthetized and, as suggested by

Maynard (19532), the ventral nerve cord was severed and the antennae and

the legs were removed to expedite bleeding. After exposure of the heart by

excision of the dorsal part of the carapace, the specimens were immersed in

sea water containing methylene blue, made up in the proportion of 15 to 20

drops of an 0:5°% solution of the stain in distilled water to 100 cc of sea water.

Observations during two to four hourly periods showed the gradual pig-

mentation of the larger nerves and the presence of a nerve plexus associated

with the heart.

The paired first dorsal nerve (figs 62, 64) is pre-eminently strong and issues

dorsally from the suboesophageal ganglion slightly behind the second maxillary

nerve. It passes upward and forward into the body cavity from the sternal canal

in front of the fused paraphragms of the first and second maxillipeds. After

supplying the posterior dorso-ventral muscle, it travels backward below the

digestive gland and sends branches to the anterior part of the epimeral attractor

muscle and the hypodermis.

The second dorsal nerves and the accompanying cardiac inhibitor fibres

(figs 62, 64) are a pair of delicate strands which arise almost level with the

origins of the first maxillipedal nerves and emerge from the sternal canal

behind the cephalic apodeme. Each extends forward for some distance close

to the more conspicuous first dorsal nerve and then courses upward and back-

ward between the medial and lateral parts of the anterior thoracic muscle.

Entering the pericardical cavity, it runs along the medial side of the deeper

thoraco-abdominal muscle, loops around the dorsal antero-lateral ligament

of the heart, innervates the epimeral attractor muscle, and also anastomoses

with the accelerator nerve to form the lateral pericardial plexus.

The third dorsal nerve, with which the cardiac accelerator fibres are asso-

ciated (figs 62, 64), is also slender, but slightly more substantial than the second

dorsal nerve. From its source in the suboesophageal ganglion approximately

dorsal to the root of the third maxillipedal nerve, it passes upward and forward

supplying the first thoracic superficial ventral muscle and then curves backward

beneath the outer face of the lateral part of the anterior thoracic muscle. It

enters the pericardial cavity below the dorsal antero-lateral ligament of the

heart and the cardiac inhibitor nerve and, after uniting with the latter in the

lateral pericardial plexus, it continues posteriorly between the lateral and

deeper thoraco-abdominal muscles, sending branches to them and to the

epimeral attractor muscle.

On each side a lateral pericardial plexus (fig. 64), established by the union

of the cardiac inhibitor and cardiac accelerator nerves, is located above the

deeper thoraco-abdominal muscle. It represents a part of the pericardial organ

168 ANNALS OF THE SOUTH AFRICAN MUSEUM

discovered by Alexandrowicz (1953), and fine branches deriving from it

constitute the anterior and posterior ligamental plexuses which are associated

more particularly with the dorsal antero-lateral and the dorsal postero-lateral

cardiac ligaments. Of perhaps even greater significance is the combination of

the inhibitor and accelerator fibres into a distinct dorsal cardiac nerve (figs 47,

64) which extends from the lateral plexus and penetrates the dorso-lateral wall

of the heart almost midway between the dorsal and lateral ostia. Within the

heart the right and left dorsal cardiac nerves meet in a mid-dorsal series of

neurones which function as the neurogenic pacemaker of the heart and have

been described as the local nervous system by Alexandrowicz (1932) and as the

cardiac ganglion by Maynard (19534, 1960). In certain unpublished observa-

tions of the heart of adult specimens of 7. lalandit made in 1959 by Mr. M. J.

Penrith, and in the present study of both the puerulus stage and mature

animals it is evident that the cardiac ganglion (diagrammatically indicated in

figure 64) takes the form of a longitudinal trunk on the inner side of the dorsal

wall of the heart. As in other marine Decapoda (Alexandrowicz, 1932; May-

nard, 1953a), it consists of five closely-approximated anterior neurones and

four smaller more widely spaced posterior neurones, and distinct processes,

given off anteriorly, posteriorly, and laterally, can be traced into the myo-

cardium. In summarizing recent conclusions concerning the function of the

cardiac ganglion, Florey (1960) and Maynard (1960) have indicated that the

large anterior cells are the follower or motor neurones and activate the myo-

cardium; the smaller posterior neurones are the pacemakers which are capable

of influencing the motor neurones. Analysing the different results of electrical

stimulation of the accelerator and inhibitor nerves of the lobster and crayfishes,

Florey (1960) has suggested that the possible release of excitatory and inhibitory

chemical transmitter substances may account for the fact that, while accelera-

tion provokes prolonged after-effects and practically no adaptation, stimulation

of the inhibitor nerves has the opposite result.

Although the physiology of the dorsal nerves of Jasus has not been investi-

gated, the present morphological findings are compatible with the more

critical experimental studies by Alexandrowicz (1932), Wiersma & Novitski

(1942), Smith (1947), and Maynard (1953a, 19530) on the cardiac regulator

nerves of other decapods. A similar structural pattern prevails in all the species

thus far examined, and the main difference seems to relate to the fact that,

while some forms, such as Cancer irroratus (Smith, 1947), Panulirus argus (May-

nard, 1953a), and possibly Homarus (Maynard, 19536), possess two pairs of

cardiac accelerator nerves, 7. lalandii agrees with Procambarus clarkiu (Wiersma

& Novitski, 1942) in having only one pair of accelerator nerves.

(ii) Thoracic ganglia

In accordance with the accounts of the nervous system of Astacus published

by Huxley (1881), Keim (1915), and Stoll (1925), the ventral nerve cord

behind the suboesophageal ganglion comprises five thoracic and six abdominal

THE ANATOMY OF THE CAPE ROCK LOBSTER 169

ganglia arranged serially from the fourth thoracic to the last abdominal

segment. All the ganglia are double, but each pair is fused into a single mass by

an inconspicuous transverse commissure, and the consecutive ganglia are

united intersegmentally by a pair of longitudinal connectives. Normally the

thoracic connectives are short, broad and adjacent, but those between the

third and fourth ganglia are more widely separated than usual for the passage

of the descending sternal artery. The fourth and fifth thoracic ganglia are

approximated and joined by very short connectives, while the last thoracic

and the first abdominal ganglia are linked by very long connectives that

emerge from the sternal canal and pass dorsally over the superficial ventral

thoraco-abdominal muscles into the abdomen.

Each thoracic ganglion gives off a pair of stout pedal nerves (figs 57, 62)

which proceed laterally into the muscle chambers of their corresponding

pereiopods and branch to the musculature in the coxopodite and the segments

of the endopodite.

Immediately in front of each ganglion in the fourth to the eighth thoracic

segments a pair of more delicate thoracic nerves (figs 62, 64) originates dorso-

laterally at the end of the inter-ganglionic connectives; the first pair (fig. 62)

occurs near the posterior limit of the connectives between the suboesophageal

ganglion and the first thoracic ganglion and innervates the muscles in the

fourth segment. As a rule, each thoracic nerve divides almost immediately

within the sternal canal into medial and lateral branches; the former supplies

the thoracic superficial ventral muscle and the medial part of the anterior

thoracic muscle, while the lateral branch proceeds to the lateral section of the

anterior thoracic muscle, the deeper and lateral thoraco-abdominal muscles,

and the epimeral attractor muscle. The thoracic nerves are also responsible

for the innervation of the reproductive organs, the paired genital nerve arising as

a branch of the third thoracic nerve in the female and of the fifth thoracic

nerve in the male. Towards the posterior end of the thorax some minor

differences are apparent in the distribution of the thoracic nerves. Thus, as

there are no epimeral attractor muscle fibres opposite the last two thoracic

segments, the corresponding nerves are lacking; and, in addition to its typical

branches, the last thoracic nerve contributes to the innervation of the paired

first anterior oblique muscle and may also supply the superficial ventral

thoraco-abdominal muscle.

Apart from slight differences in their enumeration, the thoracic nerves of

jasus are essentially similar to those of Astacus (Keim, 1915; Stoll, 1925). Stoll,

however, has concluded that in the crayfish the first three thoracic nerves are

bound to their corresponding pedal nerves; he has also distinguished an addi-

tional pair of commissural nerves arising from the longitudinal connectives,

but these are suggestive of the thoracic nerves of Jasus.

Mention must also be made of further interesting and important ramifica-

tions of the thoracic nerves. It has been demonstrated by Alexandrowicz (1932)

that in a variety of Decapoda they give rise to a system of nervi segmentales cords

170 ANNALS OF THE SOUTH AFRICAN MUSEUM

which innervate the antennary, the hepatic, and the posterior cardio-arterial

valves and the alary muscles of the pericardial septum and are independent of

the lateral pericardial plexuses associated with the dorsal nerves from the

suboesophageal ganglion. The arrangement in asus resembles that observed

by Alexandrowicz in Homarus, Scyllarus, and the Brachyura. Delicate segmental

nerves, passing inward from the last four pairs of thoracic nerves, combine to

form a pair of faint longitudinal strands (/.p.n., fig. 53) on the under surface of

the middle third of the pericardial septum medial to the paired gonads. The

two longitudinal threads are interconnected by several transverse anastomoses

and branch anteriorly to the valves of the paired antennary and hepatic

arteries. Posteriorly, after supplying the valves of the bulbus arteriosus and the

sternal and genital arteries, the two strands are continuous with a similar system

applied to the dorsal abdominal artery. As in the thorax, fine nerves, termed

the nervi segmentales aortae by Alexandrowicz, separate from the abdominal

nerves and usually run in a medial direction parallel to the paired lateral

abdominal arteries. The valves at the origins of the latter vessels receive fine

branches from these segmental nerves and, in addition, there are delicate

longitudinal connectives (J/.a.n., fig. 54) on the surface of the dorsal abdominal

artery. In discussing the significance of these elements, Alexandrowicz indicated

that the cardiac muscles are functionally antagonistic to those of the cardio-

arterial valves and the alary muscles of the pericardial septum. Consequently,

he suggested that the delicate system of segmental nerves probably acts as a

regulatory mechanism that governs the contraction of the muscles of the valves

and the pericardial septum during the diastolic period when. the heart is

distended and filling with blood.

(iii) Abdominal ganglia

The six abdominal ganglia, although proportionally smaller than those in

the thorax, are clearly recognizable antero-dorsal to the sternal ridges of their

respective segments as elongate-oval swellings with intervening longitudinal

connectives. In each of the first five abdominal segments three main pairs of

peripheral nerves pass outward and backward from the nerve cord. Two broad

pairs originate one behind the other in the ganglion, and the third, more

delicate pair issues from the longitudinal connectives a short distance beyond

the ganglion. The first paired nerve, which has been termed the fleopedal nerve

(fig. 57), is ventral in position and travels across the segment close to the

sternum; except in the first segment, where it terminates in the pleuron, it

supplies the muscles of the pleopod. The branches of the second, slightly more

posterior dorso-lateral nerve (figs 54, 57) are distributed chiefly to the abdominal

flexor muscles, but there is also a comparatively strong offshoot (fig. 54) which

curves dorso-laterally over the anterior oblique muscle and proceeds to the

superficial and deeper extensor muscles. Arising somewhat dorso-laterally from

the longitudinal connectives, the third of the series (fig. 57) are comparable

with the ventral nerves of Astacus defined by Keim (1915) and Stoll (1925). Each

THE ANATOMY OF THE CAPE ROCK LOBSTER D7

arches backward between the ventral portions of the anterior and the posterior

oblique muscles and, in addition to innervating these, also sends a branch to

the abdominal superficial ventral muscle.

On the whole, the following paired nerves, which radiate from the sixth

abdominal ganglion into the uropods and telson of Zasus, are essentially similar to

those of Astacus (Keim, 1915; Stoll, 1925). In a ventral dissection (fig. 63) most

of them seem to be more superficial than those of Astacus, and some of the

variations in the distribution of their branches in the two forms may result

more from differences of interpretation than from any marked specific

modifications.

anterior nerve

ventral! nerve cord outer uropedadl nerve

uropod ventral rotator muscle

: uropod lateral remotor muscle

anterior nerve

uropod medial remotor muscle

outer uropedal nerve.=

inner uropedal nerve rg

dorsal telson nerve

exopodite productor

muscle

intestinal nerve

exopodite adductor

muscle

inner uropedal nerve

dorsal telson nerve’

Gnal nerves :

ventral telson nerves =;

anal compressor muscle

anal dilatator muscle

ventral flexor muscle of telson?)

endopodite ddductor mus

exopodite

endopodite

Hee ON iain eo

Fic. 63. Diagrammatic ventral view of sixth abdominal ganglion and nerves to parts of left

uropod and left half of telson.

The relatively thin anterior nerve arises ventro-laterally and passes out

almost horizontally close to the sternum. After giving off a delicate supply to

the superficial ventral muscle of the sixth abdominal segment, it divides into

two branches, one of which innervates the ventral rotator muscle of the uropod,

round the lateral margin of which it then proceeds upward to the dorsal

rotator muscle of the uropod. The other branch extends below the lateral

remotor muscle of the uropod and ends in the hypodermis of the sixth pleuron

and the lateral region of the protopodite of the uropod.

172 ANNALS OF THE SOUTH AFRICAN MUSEUM

In Keim’s (1915) account of Astacus the next two nerves were described as

the nervus uropedalis and the nervus telsonos ventralis but, as the latter nerve

is hardly associated with the telson in Jasus, it seems more appropriate to

designate the two nerves in question as the outer and inner uropedals, and to

reserve the name ventral telson nerve for one which occurs more posteriorly

in the telson.

The conspicuous outer uropedal nerve, which is comparable with the uropedal

nerve of Astacus, originates close to the root of the anterior nerve and courses

obliquely outward, innervating the telso-uropedal muscles on its way to the

exopodite of the uropod. Within the latter, it supplies the abductor and

adductor muscles, and continues as a strong nerve from which a number of

branches pass into the lamella and underlie the rows of dorsal spines.

The znner uropedal is the most posterior of the latero-ventral nerves from the

sixth abdominal ganglion, and is subequal in thickness to the outer uropedal

nerve but is more widespread. Near its origin it divides into two main branches

which are directed postero-laterally over the ventral surface of the anal com-

pressor and the anal dilatator muscles, presumably without supplying them.

The thinner anterior branch subdivides into three: one offshoot travels forward

dorsal to the telso-uropedal muscles and enters the lateral and medial remotor

muscles of the uropod near their insertions; another curves into the proximal

part of the exopodite and apparently terminates in the productor and reductor

muscles; while the posterior sub-branch innervates the tissues in the proximal

lateral corner of the telson. This branch is absent from the ventral telsonos

nerve of Astacus, doubtless because Keim (1915) observed that the remotor

muscles of the uropod were served by the uropedal nerve. In passing to the

endopodite of the uropod and innervating its adductor muscle and broad

lamella, the stouter posterior branch of the inner uropedal nerve of Jasus

broadly conforms to Keim’s (1915) description of the ventral telsonos nerve of

Astacus, but differs in having no obvious connexions with the telso-uropedal,

the anal compressor, and the anal dilatator muscles.

As in Astacus (Keim, 1915; Stoll, 1925), the dorsal telson nerve issues postero-

dorsally. It is rather flat and passes above the anal compressor and anal dilatator

muscles, dividing into three branches which supply the flexor muscles of the telson.

The term ventral telson nerve has been applied to a strong nerve that originates

directly below the dorsal nerve of the telson and is represented by Keim (1915)

as an extension of the nervus telsonos dorsalis in Astacus. In JFasus, however, it

appears as a discrete element which travels backward medial to the anal com-

pressor muscle and ramifies in the telson. About halfway along its course it

gives off a fairly obvious, flat, lateral branch which probably innervates the

anal compressor and anal dilatator muscles. The nerve supply to these muscles

is difficult to determine with certainty in Jasus. There are occasional indications

that they may receive fine fibres from the main telso-uropedal and inner

uropedal nerves, but these are so indistinct and inconstant that it is assumed

that the most likely source is from the ventral telson nerve.

THE ANATOMY OF THE CAPE ROCK LOBSTER 173

The slender, but well-defined, anal nerve passes downward between the

dorsal and ventral telson nerves, and in some specimens may be adherent to

the latter. It innervates certain vertical muscle fibres stretching between the

dorsal wall of the telson and the terminal portion of the hind-gut, and fre-

quently the paired anal nerves are linked by a transverse anastomosis on the

ventral wall of the anal region of the intestine.

In addition to the above paired nerves, there is a delicate, median intestinal

nerve which extends from the postero-dorsal end of the sixth abdominal ganglion

directly to the ventral wall of the preanal part of the hind-gut. There it divides

into a short fosterior intestinal nerve to the anal region and a long anterior intestinal

nerve that generally proceeds undivided along the mid-ventral wall of the hind-

gut. The innervation of this region is variable, however, and in some dissections

the anterior intestinal nerve was observed to separate into two lateral intestinal

branches, similar to those in Keim’s (1915) account of Astacus.

2. STOMATOGASTRIC OR SYMPATHETIC NERVOUS SYSTEM

Careful dissections of preserved specimens or of animals with the nerves

stained zn vivo with dilute methylene blue in sea water, as well as the verification

of some details in serial sections, are required to trace the ramifications of this

system. It is linked to the brain by a median nerve and consists of several

interconnected ganglionic centres from which delicate nerves diverge to the

fore-gut and some neighbouring organs. The overall plan resembles that of the

crab (Pearson, 1908), the American lobster (Herrick, 1911), and more par-

ticularly that of Astacus, the details of which as presented by Keim (1915) have

proved a useful basis for the following summarized conclusions regarding the

arrangement in asus.

The main centres are a pair of ganglionic swellings, termed the paroeso-

phageal ganglia by Pearson (1908), the commissural ganglia by Herrick (1911),

Keim (1915) and some modern physiologists, and the Connectivalganglien by

Balss (1944). The first term seems appropriate because, as the name introduced

by Balss implies, the ganglia are not related to any true commissures, but are

easily observed (figs 31, 61, 64) as enlargements on the course of the circum-

oesophageal connectives a short distance in front of the post-oesophageal

commissure. They are also adjacent to the postero-lateral wall of the oesophagus

which receives a pair of delicate nerves, either from the ganglia or from the

connectives immediately posterior to them.

Emerging from each paroesophageal ganglion are two main nerves. The

inferior oesophageal nerve (figs 61, 64) arises postero-ventrally and curves forward

below the lateral oesophageal dilator muscle to meet the corresponding nerve

of the other side anterior to the oesophagus in a small, but nevertheless dis-

cernible, oesophageal ganglion (figs 31, 61, 64). The inferior oesophageal nerve

commonly gives off two delicate branches to the oesophageal muscles, as well

as a stout labral nerve (fig. 61), and the latter invariably has an anastomosis

with the oesophageal ganglion. Chaudonneret’s (1956) observation that the

174 ANNALS OF THE SOUTH AFRICAN MUSEUM

lateral ventricular nerve lateral pericardial plexus

dorsal ventricular nerve cardiac ganglion

Superior ventricular ganglion rsal rdi nerve

- wal ophthalmic artery Sioretgiy Gains "sls

cor frontale ligamental

Lemoine’s nerve plexus

20 mm.

circum-oesophagea! connective hepatic thoracic nerves

oesophagea! ganglion outer mandibular cardiac accelerator

2 = : first dorsal (third dorsal)

inferior oesophageal nerve inner mandibular

: sSuboesophageal ganglion

superior oesophageal nerve cardiac inhibitor

paroesophageal ganglion Gecondiidersal)

Fic. 64. Semi-diagrammatic side view of stomatogastric and cardiac nerves. The thoraco-

abdominal and anterior thoracic muscles have been omitted and this may give a somewhat

misleading impression of the course of the nerves.

labyrinth of the antennal gland of Orconectes limosus is innervated from the

inferior oesophageal nerve is not realized in Jasus and can hardly be expected

owing to the intervention of the antennal depressor muscles between the nerve

in question and the gland. The most likely supply to the labyrinth so far

detected in Jasus is derived from a branch of the vesicular nerve, which appears

to enter the main lobe of the labyrinth in association with the anterior renal

artery. This conclusion, however, is contrary to opinions regarding other

Decapoda, in which the labyrinth is either considered to be innervated from

some other source or to have no nerve supply and, in discussing the latter

arrangement in Procambarus clarkii, Maluf (1941) was convinced that the

secretory activity of the antennal gland was not governed by the nervous

system.

The superior oesophageal nerve (figs 61, 64) leaves the paroesophageal ganglion

anteriorly, and near its origin usually gives rise to two slender branches which

subdivide into a plexus on the antero-lateral wall of the cardiac fore-gut. The

main nerve continues forward dorsal to the inferior oesophageal nerve and

unites with its pair of the opposite side in front of the cardiac fore-gut.

As in other decapods, a long, fairly thick, median inferior ventricular nerve

(figs 61, 64) issues from the tritocerebrum between the two circum-oesophageal

connectives. It is directed postero-ventrally through the tendon of the basal

muscles of the eye and joins the upper end of the oesophageal ganglion.

THE ANATOMY OF THE CAPE ROCK LOBSTER 175

According to Keim (1915), the paired inferior and superior oesophageal

nerves, as well as the median inferior ventricular and inferior stomatogastric

nerves of Astacus, are all centred in the oesophageal ganglion, but in Jasus

the right and left superior oesophageal nerves converge some distance above

the oesophageal ganglion. From their point of union, another nerve passes

downward and joins the oesophageal ganglion in immature specimens, but

tends to connect with the inferior ventricular nerve in mature animals. This

arrangement may prove to be fairly general, for Chaudonneret (1956) has

observed a similar disposition of the inferior and superior oesophageal nerves

in Orconectes limosus, and has commented on its being one of the differences

between his findings in the American crayfish and previous accounts of the

decapod sympathetic nervous system. It is nevertheless possible that the

stomatogastric system varies in different species of Macrura, and the only

means of correlating the circumstances in asus with those of Astacus (Keim,

1915) is to suggest that the slight ganglionic swelling at the union of the pair of

superior oesophageal nerves represents a somewhat ventrally situated frontal

ganglion (fig. 61).

If this interpretation is correct, then the vertical anastomosis between. this

frontal ganglion and the oesophageal ganglion or the inferior ventricular nerve,

as the case may be, is comparable to the median inferior stomatogastric nerve

(fig. 61), although it is considerably shorter than that of Astacus.

Pursuing this line of thought, it is also reasonable to suppose that the

lower position of the frontal ganglion in Jasus has resulted in a lengthening of

the median superior stomatogastric nerve (figs 61, 64) which extends upward from

the frontal ganglion along the anterior wall of the cardiac fore-gut. Thus, as

in Astacus, the inferior and superior stomatogastric nerves are respectively

below and above the frontal ganglion but, owing to the difference in position

of the latter in the two animals, there is an inverse ratio in the lengths of the

two nerves.

The superior stomatogastric nerve links the ventral part of the system to a

conspicuous, spindle-shaped superior ventricular ganglion (fig. 64) which is located

within the cor frontale at the anterior end of the median ophthalmic artery.

Three pairs of nerves are commonly distributed to the anterior muscles of the

fore-gut, partly from the superior ventricular ganglion and partly from the

nerve continuous with it posteriorly.

In Keim’s (1915) account of Astacus, the frontal ganglion enters into

relationship with the brain by way of a superior ventricular nerve, but in Fasus no

such connexion. was observed. In fact, it is questionable if this delicate median

nerve exists in Jasus, and it has therefore been omitted in figures 61 and 64.

All the other nerves of the sympathetic system are distinct, but this one, which

should extend upward from the protocerebrum to the superior stomatogastric

nerve, has eluded positive identification. In all dissections, two bundles of

delicate striated fibres, which could easily be mistaken for nerves, were seen

to be located between the pair of nerves to the anterior basal eye muscle and

I 76 ANNALS OF THE SOUTH AFRICAN MUSEUM

to pass upward from the margin of the protocerebrum apparently to the optic

arteries. Between these bundles there were occasional evidences of one or two

very tenuous nerve fibres, but it is doubtful if they are related to the stomato-

gastric nervous system. The presence of a superior ventricular nerve in Decapoda

has been generally accepted (Balss, 1944; Hanstrém, 1947), but Balss has

indicated that it was not observed by Mocquard (1882) and Police (1908).

Continuous with the posterior extremity of the superior ventricular

ganglion there is a median dorsal ventricular nerve (fig. 64.) which leaves the lumen

of the ophthalmic artery ventrally and travels over the mid-dorsal surface of

the cardiac fore-gut, subsequently bifurcating into a pair of lateral ventricular

nerves. Each lateral ventricular nerve (fig. 64) is directed postero-ventrally over

the fore-gut and innervates the posterior gastric muscles as it passes between

them and the anterior bundle of the mandibular posterior adductor muscle. It

also gives off fine anterior twigs to the lateral wall of the cardiac fore-gut, a

stronger posterior branch which curves beneath the posterior gastric muscles

to reach the muscles of the pyloric fore-gut, and a more ventral hepatic nerve

(fig. 64) to the digestive gland.

Keim (1915) has discussed some of the earlier uncertainties and dis-

crepancies concerning the origin of the median nervus cardiacus or Lemoine’s

nerve as it is sometimes called, and has established that in Astacus it is derived

from the superior stomatogastric nerve. Although Lemoine’s nerve in Fasus

(fig. 64.) is fairly easy to detect as a delicate thread running dorsal to the median

ophthalmic artery, its course above the cor frontale is more obscure and

evidently differs from that of Astacus. It seems to have a paired origin in the

superior ventricular ganglion, the two roots passing forward and upward

round the ligaments suspending the cor frontale to the wall of the head. At

this level, which is dorsal to the cor frontale and anterior to its contained

superior ventricular ganglion, the two nerves are interconnected by a trans-

verse anastomosis at either end of which is a minute ganglion that probably

innervates the posterior basal eye muscle. Behind the anastomosis the two

nerves converge to the left of the cor frontale and form the long median

Lemoine’s nerve, from which a fine plexus is given off almost immediately to

the postero-dorsal wall of the cor frontale. The median nerve maintains its

position to the left of the ophthalmic artery for some distance, but on approach-

ing the heart it becomes mid-dorsal. It then passes between the anterior cardiac

ligaments and proceeds to the cardio-arterial valves at the base of the ophthal-

mic artery.

The function of Lemoine’s nerve has been investigated by a number of

physiologists, among whom Wiersma & Novitski (1942) have demonstrated

that it has no effect on the heart beat, and this seems to support the view that

it does not extend into the myocardium. Assuming that it terminates in the

valves of the ophthalmic artery, it is presumably similar in function to the

nerves of other cardio-arterial valves and controls rhythmic contraction of the

valves alternating with that of the cardiac muscles.

THE ANATOMY OF THE CAPE ROCK LOBSTER 77

I. SENSE ORGANS

The more obvious sense organs, such as the eyes and the statocysts, have

been well described in various Crustacea, and recently considerable attention

has been given to delicate, less conspicuous, but none the less essential, sensory

mechanisms. Detailed studies of the proprioceptors in the limb joints of Rep-

tantia have been made by a number of physiologists, including Burke (1954),

Alexandrowicz (1958), Wiersma (1959), Whitear (1962), and Bush (1962,

1965), and a concise account of the structure and function of these and other

similar receptors has been given by Cohen & Dijkgraaf (1961). It has been

shown that the limb proprioceptor organs are located in elastic strands, most

of which stretch between a muscle tendon in one limb segment and the integu-

ment at the proximal edge of the next limb segment. The proprioceptors are

associated with bipolar sensory neurones, and the fibres in each organ have

been observed to respond to the direction of movement and the position of the

joint.

Many of the diverse setae distributed over the body and the appendages

are tactile in function, but certain of the antennulary hairs are probably

chemoreceptive. Investigations by Lindberg (1955) on the behaviour of

Panulirus interruptus and some observations made during the present study of

fF. lalandi indicate that the antennules are highly sensitive to prevailing

environmental conditions and that they are particularly active during loco-

motion and foraging. Electrophysiological experiments performed by Laverack

(19624, 19626, 1963) and Mellon (1963) have demonstrated that minute hairs

located in numerous shallow pits on the body surface of Homarus and Procam-

barus may be differentiated into hair-peg organs which function as water

current receptors, and hair-fan organs which act as pressure receptors.

From a number of published accounts, it is apparent that sound production

is fairly general in decapod Crustacea, but it seems to be of little importance

in the few members of Parker’s (1884) Palinuridae Silentes. As indicated by

George & Grindley (1964), however, Dr. Heydorn has reported that in nature

f- lalandit emits audible noises. These sounds are thought to be produced by the

enashing of the mandibles, and a similar acoustic mechanism has been cited

by Dijkgraaf (1955) for Maja squinado and related forms. The antennal stridu-

latory organs of the Palinuridae Stridentes have been well documented by

Parker (1878), Dijkgraaf (1955), Lindberg (1955), Moulton (1957), Hazlett

& Winn (1962a, 1962b), and George & Grindley (1964). Two types of sound

were distinguished in Panulirus argus by Moulton (1957), who suggested that

each was related to a different behavioural pattern: a ‘conversational’ tone or

‘slow rattle’ was heard when the animals were undisturbed, but, when they

were alarmed, a defensive ‘rasp’ was produced.

It appears from Lindberg’s (1955) and Moulton’s (1957) observations

that the sounds produced by Panulirus have practically no effect on possible

predators. They may be signals that can be recognized by other members of

the same species but, so far, little is known about the sense organs responsible

178 ANNALS OF THE SOUTH AFRICAN MUSEUM

for their detection. Experimenting with several species of Decapoda, Prentiss

(1901) demonstrated that, whereas excision of both statocysts resulted only in

a slight weakening of the reactions to artificial sound vibrations, removal of the

antennules and the antennae markedly reduced sensitivity to stimulation; this

was particularly noticeable in a species of Hippolyte (Virbius) in which statocysts

are normally absent. He therefore inferred that decapod crustaceans lack true

auditory organs and that their responses to sound waves are merely tactile

reflexes. Dijkgraaf (1955) also found that ablation of both statocysts of Palinurus

elephas had no marked effect on reactions to experimental stimulation, while

Burke (1954) has suggested that the protopodite-dactylus proprioceptor of the

pereiopods of Carcinus maenas may be partly a vibrator receptor. It has been

concluded by Cohen (1955) and Cohen & Dijkgraaf (1961) that, although

there is experimental evidence of the presence in the statocysts of some receptors

which only respond to vibrations passing through the solid substratum, hearing

in the widely accepted sense has not been proved in Crustacea.

I. SENSORY SETAE

The different kinds of decapod cuticular hairs and bristles and their

possible functions have been reviewed and illustrated by Balss (1944). There-

fore, only a few general remarks are given here as an introduction to a more

detailed inspection of the antennulary setae which include important categories

of cuticular sense organs.

(a) Tactile and olfactory setae

Despite considerable morphological variation, the setae on the body sur-

face and the appendages may, according to Prentiss (1901), be differentiated

structurally and presumably functionally into two main types, namely, tactile

elements or mechanoreceptors and olfactory hairs or chemoreceptors.

Characteristically, the tactile setae have a long, tapering, feathered shaft

attached by a basal spherical bulb or ampulla that allows of great mobility.

The conclusion reached by Farre (1843) and Prentiss (1g01) that each tactile

seta is innervated by a single nerve fibre has received some confirmation from

more recent investigators, but there is experimental proof that certain short

hairs on the carapace of Procambarus clarkii (Mellon, 1963) and on the chelae

and carapace of Homarus gammarus (Laverack, 1963) are mechanoreceptors,

each of which is supplied by a pair of sensory neurones.

Olfactory setae are commonly shorter than the tactile setae, from which they

also differ in lacking an obvious ampulla, in being non-plumose, and in their

innervation by several nerve elements. Experiments performed by Holmes &

Homuth (1910) have shown that in the crayfish olfactory receptors are present

on the antennae, the mouth-parts, and the extremities of the chelipeds, but that

the greatest response to chemical stimulation is displayed by the outer flagellum

of the antennule. A gustatory sense has frequently been attributed to the

olfactory setae on the mouth-parts of some species, but Barber (1961) has

THE ANATOMY OF THE CAPE ROCK LOBSTER 179

indicated that, while this appears to be substantiated by behavioural experi-

ments, it is difficult to determine if the subtle discrimination between smell and

taste exists in Crustacea.

In F. lalandii numerous, short, plumose setae occur on the general body

surface, and also in a row along the upper margin of the raised antennal

flagellum and on the flagella of the exopodites of the three pairs of maxillipeds,

while the slender hairs on the epipodites are barbed, rather than plumed. Some

of the setae on the endopodite of the first maxilla are likewise plumed, and,

although most of the parts of the second maxilla are fringed with plumose hairs,

the longer setae projecting from the posterior extremity of the scaphognathite

into the anterior region of the branchial chamber are non-plumose and may be

chemoreceptive.

(b) Antennulary setae

In describing the appendages, it was noted that the antennulary flagella

of Fasus are short and slightly dimorphous, the outer flagellum being somewhat

smaller and broader and more or less fitting into the lateral concavity of the

inner flagellum. Both are furnished with plumose and non-plumose setae which

conform to the above general definitions of tactile and olfactory receptors.

Most of the setae are arranged in regular transverse rows coinciding with the

broadest annulations which number approximately 28 on the inner flagellum

and 33 on the outer flagellum.

The inner flagellum is compressed and, while its medial convex and lateral

concave surfaces are bare, it carries relatively short dorsal and longer ventral

marginal setae, the majority of which are plumed and have a basal ampulla

marginal bristle

plumose setae

Fic. 65. Ventral setae of inner

flagellum of antennule.

provided with a minute pointed spur. Predominantly, but not consistently,

the plumose setae in each annulus are arranged in a row of four near each dorso-

lateral and ventro-lateral edge, but occasionally there may be a supplementary

group of two (fig. 65) or three setae proximal to the main set. In addition, two

or three small, unplumed bristles occur along the dorsal margin, and the ventral

180 ANNALS OF THE SOUTH AFRICAN MUSEUM

setae are bordered by a conspicuous projecting bristle and usually a short,

plumose seta: all the long ventral plumose and non-plumose setae are so directed

that they embrace the setae of the outer flagellum.

The dorsal surface of the outer flagellum is smooth and convex, the setae

being located ventrally and comprising three structural kinds in each annulus

(fig. 66). The greater area of the ventral surface supports rows of long, delicate,

non-plumose, colourless hairs, which are faintly annulated distally, measure

about 1-2 mm long, and are comparable to the aesthetascs of other Crustacea.

There are fewer aesthetascs proximally and distally, but in most of the middle

cesthetascs ——_

0.5 mm.

lateral marginal

bristles

Fic. 66. Setae of outer flagellum

of antennule.

annuli there are two rows, in each of which 20 to 30 aesthetascs were counted.

Lateral to the aesthetascs is a long, stiff, pointed bristle, approximately 1-4 mm

in length, and one or two short plumose setae, about 400 to 500 » long, which

are probably respectively similar to the large guard and the smaller com-

panion hairs of Panulirus argus, described by Laverack (1964) and Laverack &

Ardill (1965). On the medial edge of each annulus a relatively long, unplumed

bristle, with its tapering point slightly curved outward over the aesthetascs,

also resembles a guard hair.

By analogy with the sundry functions attributed to the antennulary setae

of other Decapoda, it may be assumed that in Jasus the plumose setae respond

to tactile stimulation, while the others, and particularly the aesthetascs, are

probably chemosensitive. Calman (1909) has remarked that in many Crustacea

the aesthetascs are better developed in the males and assist in the detection of

the females, while Marcus (1911) found that the males of certain blind, deep-

sea Galatheidae had a higher olfactory quotient than the females and correlated

this with the loss of eyes. Presumably, as indicated by Forster (1951) in Palaemon

(Leander) serratus, sight plays a minor role in the mating behaviour, and only

a recently moulted female with ripe gonads will provide the necessary chemical

stimulation attractive to the male. It is also of interest that Barber (1961) has

not included the Decapoda in the list of Crustacea in which this quantitative

sexual dimorphism of the aesthetascs has been observed. A cursory examination

of a few South African palinurids reveals no marked sexual differences of

aesthetascs in Projasus parkeri (George & Grindley) or in Panulirus homarus (L.)

[P. biirgeri (de Haan) ], but it is possible that they may be rather more numerous,

THE ANATOMY OF THE CAPE ROCK LOBSTER 181

longer, and finer in the males than in the females of Palinurus gilchristi Stebb.

and 7. lalandit. For instance, in the latter species there may be approximately

25 per row in the female and 30 per row in the male, but it is doubtful if this

numerical difference has any functional significance.

Krijgsman & Krijgsman (1954) concluded that the antennulary flagella of

F. lalandii are ‘osmoreceptive’, in that they are capable of registering experi-

mental changes in the salinity of the water, while, according to Cohen &

Dijkgraaf (1961), there is evidence that the antennules of Carcinus maenas are

sensitive to water currents, and, if the antennules of Jasus are likewise sensitive

to water-borne vibrations, it seems likely that the plumose setae would react to

such stimuli. The exact site of ‘“osmoreception’ is unknown, but Laverack (1964)

has indicated the difficulties of defining the loci of individual receptors. It

has also been demonstrated by Laverack (1964) and Laverack & Ardill (1965)

that the outer flagellum of Panulirus argus is chiefly concerned with chemo-

reception and that each aesthetasc is supplied by as many as 350 neurones,

while the guard hairs and the companion hairs are probably doubly innervated.

2. STATOCYSTS

The paired balancing organ or statocyst, which has been examined in

various decapod Crustacea by Farre (1843), Prentiss (1901), Panning (1924),

Lang & Yonge (1935), Cohen (1955), Dijkgraaf (1955, 1956) and others, is

distal setae

ridges | :

% rats

statocyst

no bat Z

3 ate

3 A

arthrodial ke

membrane

Fic. 67. Dorsal view of base of right antennule.

182 ANNALS OF THE SOUTH AFRICAN MUSEUM

located in the proximal segment of each antennule. In Fasus its position is

marked by a paler, dorsal area bounded by definite ridges and, as in other

Macrura, it is an open vesicle. The small external aperture (figs 60, 67) occurs

in a depression between the medial and lateral ridges, and the short, slightly

oblique entrance is overlapped by the dorsal wall of the antennule. Associated

with the statocyst are three sets of conspicuous, external setae (fig. 67): latero-

distal to the aperture there is a row of approximately 22 relatively long, plumed

setae; along the lateral ridge is a group of about 16, more or less alternating

long, stiff, unplumed bristles and shorter plumose setae; and the medial

border of the statocyst area is fringed with two or more rows of numerous,

fairly long, feathered setae, the anterior and posterior pinnules of which are

often unequal in length.

The statocyst (figs 60, 68) is a thin-walled, transparent, fluid-filled, oval

sac, measuring about 4:1 mm long by 1:75 mm wide in medium-sized speci-

mens, and having a rounded anterior margin and a more pointed posterior

extremity. It projects inward and downward at an angle slightly inclined to the

horizontal plane and, being dorso-ventrally flattened, its longer, curved, lateral

and shorter medial margins are pronounced. Its walls, which may conveniently

be described as dorsal and ventral, are lined with about 500 delicate, plumose

hairs which are directed into the lumen and belong to the category of tactile

sensory elements.

Position of aperture

WM, Ni es . statolith hairs

\ \ ‘ \ { (

Ni!) oa / l

Re) S\ - Ss ; ae

AAV

|= *\ =\

dorsal hairs eS Se aN

(thread hairs)

antero-dorsal hairs

(group hairs)

Sin J/; ro-medial

(pa —vent

cane Ye ZT. hairs

= ( (free-hook hairs)

J vS

\ / x //

sx eld

lateral hairs

(free-hook hairs)

DORSAL WALL VENTRAL WALL.

Fic. 68. Inner views of walls of bisected left statocyst from which the statoliths have been removed.

Although the arrangement of the statocyst hairs hardly corresponds with

any of the patterns so far reported in other species, four structural types, com-

parable with those of Carcinus maenas (Prentiss, 1901; Dijkgraaf, 1956), Maja

THE ANATOMY OF THE CAPE ROCK LOBSTER 183

verrucosa (Dijkgraaf, 1956), and Homarus americanus (Cohen & Dijkgraaf, 1961),

may be differentiated.

The middle of the ventral wall of the statocyst is slightly convex and raised

into a somewhat crescentic area, termed the sensory cushion by Prentiss (1901).

This is furnished with two main and an additional third scanty row of rather

small and relatively stout statolith or hook hairs (figs 68, 69), the plumose tip of

each of which is characteristically bent at an acute angle on the proximal part

of the shaft. Resting on the statolith hairs are numerous small sand grains or

statoliths (fig. 60) which are bound together by a mucous adhesive, said by

Prentiss (1901), Lang & Yonge (1935), and Cohen & Dijkgraaf (1961) to be

secreted by special glands situated beneath the walls of the statocyst. Experi-

ments described by Cohen (1955), Dijkgraaf (1956), and Cohen & Dijkgraaf

(1961) demonstrate that the statolith hairs react to movements of the statoliths

resulting from the force of gravity; they are considered to serve as position

receptors, whose response is mainly to displacement about the transverse axis,

but also partly to postural changes about the longitudinal axis.

0.1 mm.

DORSAL THREAD HAIR

LATERAL FREE-HOOK HAIR

Fic. 69. Sensory hairs of statocyst.

Thread hairs (figs 68, 69), which are long and slender with a tapering

plumed tip, are distributed over the dorsal wall. Similar hairs in other decapods

are stimulated, not by positional changes, but by movements of the fluid

contents of the statocyst; they have been defined by Dijkgraaf (1956) and Cohen

& Dijkgraaf (1961) as rotation receptors which are sensitive to movements

about vertical and horizontal axes.

The longest hairs (figs 68, 69) within the statocyst occur usually in pairs

along the lateral and medial margins of both walls, and each is distinguished

by a fine, tapering, slightly curved, plumose tip. They are probably comparable

with the free-hook hairs mentioned by Dijkgraaf (1956) and Cohen & Dijkgraaf

(1961), who have suggested that they may assist in governing the rotatory

reflexes initiated by the responses of the thread hairs to stimulation. .

The group hairs described by Prentiss (1901) in proximity to the statocyst

aperture of Carcinus maenas differ from the other kinds of hairs in being short.

coarse, and unplumed. This definition does not apply to any of the statocyst

184. ANNALS OF THE SOUTH AFRICAN MUSEUM

hairs of 7. lalandii, but in a position corresponding to that of the group hairs of

Carcinus maenas there is an obvious antero-dorsal field (fig. 68) with numerous

comparatively stout, medium-sized hairs, each of which (fig. 69) is jointed,

heavily fringed at the tip, and directed towards the aperture. In the statocyst

of other species Farre (1843) and Panning (1924) have also indicated that

there is a triangular field of sensory hairs guarding the aperture. Although

their function has not yet been determined, Prentiss (1901) suggested that the

group hairs of Carcinus might be modified tactile hairs that had been invaginated

during the formation of the statocyst.

3. EYES

The main visual organs of adult decapod Crustacea are a pair of stalked,

lateral, compound eyes, but in some species a small unpaired or median eye,

which is characteristic of malacostracan larvae, may be retained in the adult.

(a) Median eye

According to Gilchrist (19136), a median eye-spot, as well as lateral

compound eyes, occurs in the recently-hatched naupliosoma larva of 7. lalandit,

and Von Bonde (1936) has indicated that it is a feature of an even younger

prenaupliosoma stage but that ‘it disappears and is lost’ (p. 18) after the

3-8 mm stage of the phyllosoma larva. However, in the course of the present

study close inspection of the phyllosoma and puerulus stages proves that the

small median eye is still visible through the transparent exoskeleton; moreover,

it also persists in the adult. It projects mid-dorsally from the brain immediately

below the fused eyestalks of the compound eyes and, on exposure of the anterior

part of the nervous system of juvenile and more mature specimens (fig. 61), it

is easily detected by its mass of reddish pigment. In sections of the puerulus

stage (fig. 70) the bulk of the pigment is seen to be arranged in two crescentic

layers along the medial borders of a pair of obvious, closely-apposed lateral

cups composed of sensory cells with relatively large nuclei; ventral to these

pigment —

Ss ———

eee Sane

apical nerve

V4 lateral nerve

“ay

Fic. 70. Semi-diagrammatic vertical section of

median eye of puerulus stage. The lateral nerves

and lower parts of apical nerves were added from

a section 30 uw behind that passing through the three

cups of the eye.

THE ANATOMY OF THE CAPE ROCK LOBSTER 185

there is a smaller median cup occupied by three large cells. The three portions

of the median eye are innervated independently by very short, fairly broad

nerves that converge at the frontal margin of the protocerebrum midway

between. the apical nerves to which the lateral nerves are adjacent. The several

nerves can be seen mid-dorsally in the cellulae anteriores superiores (fig. 58),

but presumably have deeper centres in proximity to the pons cerebri. The whole

structure lies between the median ophthalmic artery and the brain about 130 p»,

in front of the section drawn in figure 58. It has apparent distal connexions

with the mid-dorsal epidermis, the cells of which are modified and considerably

elongated; the lateral extensions encircle the ophthalmic artery, but another

one appears to pass directly upward through the middle of the artery.

The median or nauplius eye has been carefully investigated in a variety

of adult Decapoda by Elofsson (1963), who has concluded that broadly speaking

it is a combination of the nauplius eye sensu stricto and the dorsal frontal organ.

The latter is represented by a pair of large postero-lateral cups, and the lateral

nerves are formed by the axons of its cells. The perfect nauplius eye s.s., as

described by Elofsson in some Natantia, consists of the ventral cup and two

antero-lateral cups above the dorsal frontal organ, each of which contains

three sensory cells. Elofsson has also indicated that, as the axons of the three

nerves leave the proximal ends of the sensory cells and pass through the pig-

ment, the eye is of the everse type. A similar arrangement holds good for Fasus,

in which the median fibres extend vertically downward while the fibres forming

the lateral nerves curve outward from the inner frontal ends of the cells in the

posterior two-thirds of the lateral cups and usually enter the brain some distance

in front of the median nerve. Although the antero-lateral cups of the nauplius

eye s.s. and the dorsal frontal organ are not clearly differentiated in the eye of

Jasus, it is assumed that the whole of the lateral cup represents an intimate

association of the two parts. A paired ventral frontal organ, extending between

the brain and the epidermis, is manifest in many of the species studied by

Elofsson, but no definite conclusions have been reached as to its identity in

Jasus.

No observations of the median eye of Palinuridae were made by Elofsson

(1963) but, owing to its prevalence in other adult Reptantia, he suggested

that it might be present in Palinura and Astacura. From his account and

illustrations it is evident, however, that the median eye of Zasus bears a closer

resemblance to that of some of the Natantia than to any of the Reptantia he

has examined. He has disclosed that a median eye is exceptional in adult

Brachyura and that, while in other Reptantia it is reduced and located either

on or under the epineurium, in various Natantia it projects above the brain,

much as has been observed in Jasus. Elofsson has mentioned that it is a photo-

sensitive organ but, so far as is known, the function of the median eye of marine

Decapoda has not been fully investigated. However, Baylor & Smith (1957)

have demonstrated that in the fresh-water branchiopods, Daphnia magna and

Eubranchipus, it is correlated with some of the movements observed during

186 ANNALS OF THE SOUTH AFRICAN MUSEUM

vertical migration, a positive geotaxis and a negative phototaxis being induced

under ultra-violet and violet light stimulation. The reversal of this behaviour

may apply to the planktonic naupliosoma and young phyllosoma larvae of

f. lalandii, which Gilchrist (1913@) found to be strongly attracted to the source

of bright illumination, while older larvae persistently avoided light.

(b) Compound eyes

From examinations of serial sections it is apparent that the microscopic

details of the paired eyes of the adult and the puerulus stage are comparable

to those of other Decapoda. Those of the puerulus stage, however, are more

nearly related to the traditional model, and have therefore been selected as

the basis of the following remarks.

In describing the musculature (p. 65), it was indicated that the eyes are

lommatidia a eS te Ee Ee crystalline cone

retinular cel!

Tid

LOS Sw!)

SAC So Me

neh tt

Sep eae

rhabdome

basement membrane

peripheral Sinus

= WR nternal chiasma

sinus gland

i = aS Sh Tinea

\ = \ \ sinus gland

lamina ganglionaris

external chiasma

neurosecretory ceils

medulla externa

ventral retractor

muscle

fibre tract

Ve retractor

muscle

neuroSse-

cretory cells

medulla terminalis

oculomotor I

oculomotor II

optic nerve

Fic. 71. Puerulus stage: longitudinal section of compound eye; only half the number of

ommatidia are represented.

THE ANATOMY OF THE CAPE ROCK LOBSTER 187

normally perpendicular to the long axis of the body and that each is located in

a spheroidal cup supported by a movable two-segmented stalk or peduncle.

The numerous visual elements are similar, cylindrical, radiating structures, the

ommatidia, which are closely aggregated in a deeply-pigmented, somewhat

reniform area. A transparent cornea covers the surface of the eye and is

demarcated into regular rows of minute, contiguous, square facets, each repre-

senting the periphery of an underlying ommatidium.

Apart from the eye muscles and blood vessels, the optic cup is largely

occupied by the Jobus opticus which consists of four ganglia (figs 59, 61, 71, 74),

termed the lamina ganglionaris, the medulla externa, the medulla interna, and the

medulla terminalis. The latter is the largest mass and is connected to the brain

by the pedunculus lobi optict or optic nerve (figs 31, 57-59, 61, 71, 74). According to

Hanstrém (1939), the first three are primary optic ganglia, while the medulla

terminalis represents a portion of the protocerebrum which, together with the

optic centres, has migrated into the peduncle. The three medullae consist of

layers of neuropiles surrounded by neurones, but the lamina ganglionaris is

distinguished by the fact that it seems to be composed of parallel structures,

the neurommatidia (fig. 72 A), each of which is considered by Hanstrém (1947)

and other observers to be formed by the axons of several primary optic fibres

coming from the ommatidia. The three distal ganglia are linked by the external

and internal chiasmata (fig. 71), but there is no distinct chiasma between the

medulla interna and the medulla terminalis, and these two regions are broadly

united and merge almost imperceptibly into each other.

(1) The ommatidia

The component parts of the ommatidia of other Crustacea have been so

fully described by authors such as Huxley (1881), Parker (1890, 1891), Exner

(1891), Pearson (1908), Demoll (1917), Debaisieux (1944), Ramadan (1952),

Mayrat (1956), Kampa (1963), and Kampa, Abbott & Boden (1963), that a

brief outline of the elements of a single ommatidium observed in longitudinal

and transverse sections of the eye of the puerulus stage will suffice.

The cornea (figs 71, 72 A) is a convex, transparent, exoskeletal layer,

composed of numerous, delicate, horizontal laminae and visible externally

as a square facet.

The rather flat corneagen cells (fig. 72 A), of which there are two per omma-

tidium, secrete the cornea and are considered to be epidermal in origin.

The crystalline cone cells underlie the corneagen cells, and in transverse

sections (fig. 72 B) it is evident that there are four in each ommatidium.

The crystalline cone (figs 71, 72 A), which is secreted by the cone cells, is a

hyaline, refringent body which is rectangular and quadripartite in transverse

section (fig. 72 C’). It is more or less pyramidal in outline, with its broad base

adjacent to the cone cells and its apex directed inward to become associated

with a more delicate, long, tapering crystalline cone stalk (figs 71, 72 A). The

latter is also squarish and quadripartite in cross section.

188 ANNALS OF THE SOUTH AFRICAN MUSEUM

5 = corneagen cells

2/\el— 2

crystalline cone cell

nucleus of distal pigment cell

distal pigment cell

cone

Rye) — |

crystalline cone

[F-———-distal pigment cell

crystalline cone Stalk

0.1 mm.

retinulaor cells

retinular cells rhabdomes

H i =

= proximal pigment

de —. [EE

H \e :

nucleus of tapetal pigment cell

tapetal pigment

Primary optic fibres

Subretinal blood vessels

cell bodies of neurones

of lamina ganglionaris

faomind ganglionaris

(neurommatidia)

Fic. 72. Puerulus stage: A, longitudinal section of two

ommatidia; B, transverse section of cone cells; C, transverse

section of cones; D, transverse section of rhabdomes.

The retinula is composed of seven, similar, elongate retinular cells (figs 71,

72 A, D) arranged around an axial rod, the rhabdome. The retinular cells

extend from the level of the proximal end of the cone stalk to the basement

membrane (figs 71, 72 A) which is a convex connective-tissue network separating

the eye proper from the optic cup. The somewhat bulbous distal end of each

retinular cell accommodates a conspicuous nucleus, behind which the cell

THE ANATOMY OF THE CAPE ROCK LOBSTER 189

narrows appreciably and is prolonged as a primary optic fibre. The primary

optic fibres (fig. 72 A) pierce the basement membrane and, becoming asso-

ciated in bundles, are said to synapse with the neurones of the lamina ganglion-

aris. In addition to the seven main retinular cells, there is a less obvious,

eccentric eighth or accessory retinular cell, which is chiefly recognizable by

its distinct oval nucleus.

The rhabdome (figs 71, 72 A, 72 D), which is a refractive fusiform body, is in

direct contact with the proximal end of the cone stalk, and is now considered

to be the main photoreceptor of the ommatidium. In longitudinal sections it

seems to consist of about 30 to 40 superimposed transverse plates which give it

a peculiar stratified appearance. A study of the ultrastructure of the rhabdome

of Homarus by Rutherford & Horridge (1965) has revealed that each plate or

layer of the rhabdome consists of closely fitted tubules or microvilli, which are

so arranged that the tubules of adjacent layers are at right angles to one

another. According to Parker (1891), Kampa (1963), and Kampa, Abbott &

Boden (1963), the rhabdome is usually composed of four rhabdomeres, three

of which have been shown by Parker (1891) to be located opposite six of the

retinular cells, while the fourth is bordered by the seventh retinular cell.

As in other Decapoda, the retinal pigment is distributed in three groups of

cells which have been described as the distal, the proximal, and the reflecting

or tapetal pigment cells by Welsh (1930) and subsequent investigators. On

the outside of each crystalline cone are two right-angled distal pigment cells

(fig. 72 A) which contain brownish pigment. In transverse sections (fig. 72 C)

it is apparent that the cells are placed diagonally opposite each other and are

in such close proximity to those of neighbouring ommatidia that they form a

frame of screening pigment around the individual cones. Approximately at the

middle level of the cone, each cell has a small, but distinct, nucleus, while

distally and proximally the cell is reduced to delicate processes which extend

respectively to the cornea and to the retinular cells. The dark brown proximal

pigment (fig. 72 A), which is located in the seven functional retinular cells,

forms a sheath around the rhabdome and is continued into the primary optic

fibres. The reflecting or tapetal pigment (fig. 72 A) occurs in irregular cells

which occupy the proximal parts of the interommatidial spaces. Each is

characterized by a small, distinct, oval nucleus (fig. 72 A) near the level of the

proximal end of the rhabdome and, in certain circumstances, the dense granular

contents and also the proximal pigment may pass through the basement mem-

brane. In this connexion, Mayrat (1956) has concluded that the normal position

of the tapetal cells is probably at the distal end of the ocular peduncle, and he

and other investigators have emphasized the fact that the pigment is white in

reflected light, but yellowish-brown in transmitted light.

(ii) General remarks

Excellent accounts of the function of the various elements of the crustacean

compound eye have been given by Exner (1891), Demoll (1917), Kleinholz

190 ANNALS OF THE SOUTH AFRICAN MUSEUM

(1961), and Waterman (1961) and, although no critical experimental tests have

been performed on the eyes of Jasus, some of the results obtained in other

species are pertinent to the present observations. From his comprehensive study

of the compound eyes of a variety of arthropods, Exner (1891) concluded that

it was possible to recognize two main functional types, the apposition and the

superposition eye, the former being characteristic of diurnal, littoral, and terrestrial

animals and the latter of nocturnal, deep-sea, and subterranean forms. Identi-

fying the cornea and the crystalline cone as the dioptric apparatus of the

ommatidium, and expounding the principles of lens cylinders, he and later

Demoll (1917) have shown that, whereas in the apposition eye the axial length

of the lens cylinder is about equal to its focal distance and the resultant image

is inverted, in the superposition eye the axial length of the cylinder is double

that of its focal length so that inversion of the image takes place about the

middle of the cylinder and there is a further reversion more proximally. Among

important structural differences between the two types noted by these authors

are the long, slender rhabdomes in contact with the cones in the apposition

eye, compared to which the rhabdomes of the superposition eye are short and

fusiform and remote from the cones. Furthermore, the physical adaptation of

the apposition eye to high intensities of light is manifest in the sheath of distal

and proximal pigments along the length of the ommatidium, which is thus

effectively isolated from neighbouring units. Diffusion of light from one unit

to another is prevented, and the stimulation of any one rhabdome is effected

only by light rays passing down the main axis of its particular ommatidium.

The result has been assumed to be the formation of separate minute images

which, like the contiguous pieces of a mosaic, combine to produce a complete

impression of the object in the visual field, but Waterman (1961) has suggested

that this theory may not be strictly applicable to all apposition eyes. On the

other hand, in the superposition eye, which functions in light of low intensity,

the retinal pigments are normally retracted from the cones and rhabdomes

and, consequently, oblique light rays entering a number of adjacent ommatidia

are refracted by the several cones and are capable of stimulating a single

rhabdome. In this way the superposition eye makes full use of available light

rays, but visual acuity may be inferior to that of the apposition eye. Based on

Exner’s (1891) deductions, it has generally been supposed that the images

formed by this type of eye overlap one another, but this does not appear to

have been confirmed in recent observations of superposition eyes (Waterman,

1961). The tapetal pigment, which occurs near the basement membrane in

most superposition eyes, probably contributes to the reflection of light towards

the rhabdomes, particularly when the proximal pigment is withdrawn.

It has been indicated by Kleinholz (1961) that chemical analyses of the

retinal pigments demonstrate that the proximal and distal pigments are mela-

nins in some species but ommochromes in others, while the tapetal pigment,

which was formerly thought to be guanin, is now known to contain five com-

pounds, identified as pteridines and purines. Two additional items of general

THE ANATOMY OF THE CAPE ROCK LOBSTER IOI

interest mentioned by Waterman (1961) are, firstly, the presence of the photo-

sensitive pigment rhodopsin, presumably in the rhabdomes of Homarus ameri-

canus, Nephrops norvegicus, and Meganyctiphanes norvegica, and, secondly, the fact

that light sensitivity is not restricted to the eyes, but is also evinced by the sixth

abdominal ganglion of some Macrura.

Exner’s (1891) observations have also established that, whereas the retinal

pigments of most apposition eyes are usually fixed in position and vision is

limited to daylight, in superposition eyes all three sets of pigment are freely

movable and their distribution is an important factor in adapting the eyes to

both nocturnal and diurnal vision. More recent support for this concept has

been provided by Debaisieux (1944) and other investigators who, after exposing

experimental animals to periods of bright illumination or total darkness, have

found that in light-adapted eyes the distal and proximal pigments migrate

around the cones and rhabdomes, providing them with a complete mantle,

similar to that in a typical apposition eye. In dark-adapted eyes, however, the

pigments move away from the rhabdome and the condition is comparable to

that of a normal superposition eye.

In connexion with some of the foregoing remarks, it may be noted that the

specimens of the puerulus stage of Fasus used in the present study were collected

by Dr. A. E. F. Heydorn at night, but had been attracted to the nets by the

beam of a powerful searchlight. They were fixed immediately in a well-

illuminated laboratory on board the research vessel belonging to the Division

of Sea Fisheries. Some response to this illumination seems to be reflected in the

subsequent sections of their eyes (fig. 72 A) inasmuch as the greatest condensa-

tion of distal pigment occurs around the junction of the cones and the cone

stalks, and the rhabdomes are at least partially screened by the proximal

pigment. The extent of the tapetal pigment is less readily ascertained as it is

somewhat obscured by the proximal pigment, but it appears to be distributed

above and slightly below the basement membrane. In serial sections of the

adult eye it is evident that the position of the distal pigment is similar to that

of the puerulus stage and that the retinular cells are heavily charged with

proximal pigment. Moreover, as there is little indication of proximal pigment

below the basement membrane, it may be assumed that the eyes approximate

the light-adapted condition. Contrasted with this is Waterman’s illustration

(fig. 2C’, 1961) of a section of the eye of a young Panulirus argus in which

response to dark-adaptation is shown in the concentration of the proximal

pigment on both sides of the basement membrane.

Another interesting phenomenon which has been observed by a number of

investigators and particulars of which are given by Brown (1961) is that, in

animals kept for relatively long periods under continuous illumination or

darkness, a regular diurnal rhythm takes place in the activity of the retinal

pigments. Apparently, however, the details differ according to the species but,

despite somewhat inconsistent responses witnessed in both diurnal and noc-

turnal animals, the significant fact emerging from the observations is that this

192 ANNALS OF THE SOUTH AFRICAN MUSEUM

recurrent daily migration of one or more of the retinal pigments is quite

independent of constant experimental conditions. It has been seen to coincide

with natural daily changes in light intensities and possibly other environmental

factors at sunrise and sunset, and the investigators have concluded that it is

therefore caused by some internal agents.

The mechanisms controlling the migrations of the retinal pigments have

not yet been fully elucidated, but it has been suggested by Welsh (1930) that

the movements of the distal pigment may be effected by the contractility of

three or four fibrils contained in the distal pigment cells, while cytoplasmic

streaming may account for the mobility of the proximal and tapetal pigments.

Furthermore, the results of interesting experiments detailed by Welsh (1939,

1941), Carlisle & Knowles (1959), Kleinholz (1961), and Kleinholz et al (1962)

are regarded as proof that the movements of the distal pigment are regulated

by a hormone which is released from the sinus gland when the eyes are illu-

minated. There is also some evidence that the tapetal pigment is likewise

under endocrine control, but the source of the hormone is somewhat con-

jectural. There also appears to be no experimental proof that any hormone

produced in the eyestalk is concerned with the movements of the proximal

pigment, but Kleinholz (1961) has suggested two possibilities, either that an

activating hormone is processed outside the eyestalk, or that the retinular cells

are ‘independent effectors’.

Some of the structural differences between the eyes of shallow-water and

deep-sea Crustacea examined by Beddard (1890), Welsh & Chace (1937, 1938),

and Ramadan (1952) may be interpreted as important modifications correlated

with the adaptations of the eyes to the particular environment of the animals

concerned. Considerable morphological variation is shown, however, in deep-

sea forms, some having proportionally large eyes with presumably functional

elements, while in others the eyes are degenerate or even absent. According

to Welsh & Chace (1937, 1938), this apparent anomaly may be explained by

the fact that luminescent organs and a thick layer of reflecting pigment are

often associated with large eyes. In some instances the only obvious difference

between the eyes of nocturnal deep-sea and shallow-water species is the reduc-

tion in the former of the amount of distal and proximal retinal pigment, while

degenerate eyes, which are remarkable for the loss of screening pigments and

also of rhabdomes, are furnished with a large quantity of reflecting pigment.

Ramadan’s (1938, 1952) studies of the eyes of representative Penaeidae

have revealed, not only that the eyestalk is less complex in deep-sea species,

but also that in certain structural details the ommatidia differ markedly from

those of related shallow-water species. While the nuclei of the crystalline cone

cells of the latter are said to be angled and located in the corners of the cells

and the rhabdomes conform to the typical decapod structure, in deep-water

forms the nuclei of the crystalline cone cells are rounded and centrally placed

and the rhabdomes are non-striated and peculiarly branched in transverse

sections. Although the reason for these differences is obscure and Ramadan

THE ANATOMY OF THE CAPE ROCK LOBSTER 193

(1952) has concluded that they cannot be accepted as indications of adaptive

modifications, they are, nevertheless, of interest in a consideration of the eyes

of Fasus.

Compared with the puerulus stage, the ommatidia of the adult eye have

proportionally longer cone stalks, but this may be merely a normal incident in

the transformation of the larva into the adult state, for Kampa, Abbott &

Boden (1963) have observed that a similar elongation of the cone stalks takes

place between the zoaea and the adult stages of Homarus gammarus (vulgaris).

A more remarkable difference in 7. lalandii is the apparent structural resem-

blance of the short rhabdomes of the adult eye to those of deep-sea Penaeidae

examined by Ramadan (1952). While Parker (1891) was somewhat doubtful

as to the presence of rhabdomes in Palinurus (probably Panulirus), Exner (1891)

remarked that the eyes of Palinurus may be compared to those of Palaemon and

Sicyonia, but that ‘die Sehstabe sind hier ziemlich klein’ (p. 124). In sectioned

material of the eye of 7. lalandii, differentially stained with Heidenhain’s iron

haematoxylin and phloxine, the rhabdomes are visible as short, clear, cerise

structures which are sharply contrasted with the surrounding, narrow, heavily-

pigmented retinular cells. The latter are uniformly constructed throughout

their length, and in distal transverse sections (fig. 73) they are disposed around

the rhabdome, but this is quite unlike the striated, fusiform structure observed

retinular cells

Fic. 73. Transverse

section of rhabdomes

of adult eye.

in the puerulus ommatidium. It is composed of seven branched rays which

correspond with the seven main retinular cells, and in dissections of bleached

preparations superficially resemble the curved staves of a minute barrel.

Proximally the rhabdome appears to taper off, but the rosette formation of the

retinular cells is maintained up to the basement membrane. A similar stellate

configuration of the proximal ends of the retinular cells is also evident in the

sectioned eye of young Panulirus argus (Waterman, 1961), in Pleuroncodes planipes

(Kampa, 1963), and in Homarus gammarus (Kampa, Abbott & Boden, 1963),

and probably represents the characteristic grouping of the axons of the seven

normal retinular cells in most Decapoda.

The marked difference between the rhabdomes of the puerulus stage and

those of the adult suggests that the onset of adult life in Zasus evokes a trans-

formation of the eyes from a condition typical of pelagic and shallow-water

194 ANNALS OF THE SOUTH AFRICAN MUSEUM

Decapoda to one approximating that of benthic species. To some extent this

seems to be supported by the presence in the puerulus stage of a fairly con-

spicuous eye-papilla (fig. 74) which Hanstrém (1939, 1947) has stated is well

developed in pelagic and bathypelagic Macrura Natantia and may function as

a tactile organ. It projects ventrally towards the antenna as an evagination of

the frontal wall of the optic cup; in section it is more or less oval in outline and

contains a number of distinct bipolar sensory neurones, the axons of which

pass into the medulla terminalis and become associated with the larger elements

of Hanstrém’s X-organ, or the sensory papilla X-organ (SPX) as it is now

designated by Carlisle & Knowles (1959) and Passano (1960). Although the

sensory papilla is absent in the adult, its former position seems to be indicated

by an obvious transparent area, which may be comparable with the so-called

sensory pore of other Crustacea, but in sections of the eye there is no noticeable

thinning of the cuticle over this region.

In preference to including details of the optic blood vessels in the general

account of the vascular system, it has been deemed expedient to deal with

them briefly after considering some aspects of the structure of the eye. Informa-

tion concerning these blood vessels in other Crustacea has been supplied mainly

by Baumann (1921), Debaisieux (1944), Mayrat (1956), and Mauchline

(1958), whose accounts clearly indicate that a fairly uniform plan underlies

their distribution in different Crustacea.

It has already been intimated (p. 145) that the blood supply to the eye

muscles is derived from a delicate oculomotor artery, while that to the optic gan-

glia stems from the optic artery, which itself is one of the terminal branches of

the median ophthalmic artery. The course of the optic artery may be traced

in dissections of injected adult specimens or, more precisely, in serial sections

of the eye but, as most of the delicate endings of the arteries and veins form a

complex network within the lobus opticus and merge so imperceptibly into one

another, it is often difficult to ascertain where one system terminates and the

other begins. By reconstructing serial sections of the smaller eyes of the puerulus

stage and omitting the intricate ramifications and anastomoses within the

lobus opticus, it is possible, however, to obtain a general impression of the main

arterial and venous channels (fig. 74).

The optic artery is a wide vessel which runs through the eyestalk parallel

to the optic nerve and, passing frontally, divides into four main branches which

are substantially similar to those observed in Astacus by Baumann (1921). The

first branch arises at the base of the lobus opticus, where it immediately enters

the proximal part of the medulla terminalis, subsequently irrigating this region

and giving off a few small vessels to the distal end of the optic nerve. Curving

over the optic ganglia, the main stem of the optic artery courses distally, giving

rise to the second branch which subdivides and transports a copious supply of

blood to the distal part of the medulla terminalis and the medulla interna. The

THE ANATOMY OF THE CAPE ROCK LOBSTER 195

“Wu SG

fourth branch

third branch

radial sinuses Im sd

admindg ganglionaris

medulla externa

medulla interna

eye papilla

second branch

medulla terminalis

first branch

optic artery

peripheral Se

optic hs es

Fic. 74. Diagrammatic reconstruction of main blood vessels of left eye of puerulus

stage.

medulla externa receives its main share of blood from the distal offshoot of the

third branch, but this vessel also serves the two chiasmata and may send addi-

tional tributaries into the medulla interna and the medulla externa from its

proximal subbranch. The terminal portion of the optic artery represents the

fourth branch which bifurcates, one vessel passing along the distal margin of the

lamina ganglionaris and the other dividing into a series of fine channels in the

subretinal region in close proximity to the basement membrane of the eye. In

partial agreement with the findings of Debaisieux (1944) and Mayrat (1956),

there is no marked circulation to and from the lamina ganglionaris, but it is,

however, traversed by occasional delicate anastomoses which connect the

196 ANNALS OF THE SOUTH AFRICAN MUSEUM

vessels on its proximal and distal margins. Contrasted with this, the lamina

ganglionaris, as well as the three medullae of some crustacean eyes examined

by Mauchline (1958), is provided with a rich supply of blood.

While it is generally accepted that the interommatidial spaces of the eye

contain blood and most observers have reported the presence of a regular

series of minute arteries on the proximal side of the basement membrane, the

actual passage of blood into the eye has proved difficult to determine with

accuracy. Close to the distal end of the optic artery in Palaemon (Leander)

squilla, however, Mauchline (1958) has detected an opening in the basement

membrane which would allow of the entrance of arterial blood into the inter-

ommatidial spaces. No such aperture was observed in Jasus, and the impression

gained from an examination of serial sections of the eyes of the adult and the

puerulus stage was that some of the fine terminal frontal arteries radiating

between the primary optic fibres in the subretinal region might penetrate the

basement membrane and so introduce blood into the eye.

Within the several parts of the lobus opticus, the various branches of the

optic artery resolve into numerous delicate vessels from which the blood enters

a system of ramifying venous passages. Along these the blood is directed out of

the lobus opticus into radial sinuses which are associated with the three distal

ganglia and empty into a large peripheral sinus. It is also evident that, communi-

cating with the latter, there are one or more conspicuous venous channels from

the medulla terminalis. Although the arterial supply to the visual part of the

eye cannot be demonstrated satisfactorily, there are indications that, as in

Meganyctiphanes (Mauchline, 1958), the deoxygenated blood leaves the inter-

ommatidial spaces and enters the peripheral sinus through a relatively wide

ventro-lateral passage. The peripheral sinus lies in the space between the lobus

opticus and the wall of the optic cup and envelops the eye muscles. After the

confluence of the two eyestalks, the blood from both eyes flows into the anterior

cephalothoracic sinus around the brain.

J. ENpDocrInE ORGANS

A comprehensive discussion of crustacean endocrinology is beyond the

scope of the present study, but the increasing interest shown in this discipline

during the past thirty years warrants some mention, at least, of the presence

and the arrangement of the main endocrine organs observed in 7. lalandu.

Instructive reviews of research on crustacean hormones by Hanstrém (1939),

Kleinholz (1942), Brown (1944), Gabe (1954), Carlisle & Knowles (1959), and

Welsh (1961) provide evidence of the progress made since Hanstrém’s dis-

covery of the sinus gland in Decapoda in 1933; and the gradual solution of

cytological and physiological problems has resulted in the interpretation by

Bliss (1951), Passano (1951), Bliss & Welsh (1952), and Bliss, Durand & Welsh

(1954) of the sinus gland and the X-organ as functionally interrelated parts of

an extensive neurosecretory system from which hormones, synthesized in its

specialized neurones, are released into the blood stream.

THE ANATOMY OF THE CAPE ROCK LOBSTER 197

Several types of neurosecretory cells have been described in various regions

of the nervous system, particularly in the optic ganglia and brain by Enami

(1951), Bliss & Welsh (1952), Carlisle & Passano (1953), Bliss, Durand &

Welsh (1954), Durand (1956), and Carlisle (1959). Hormones have also been

reported in the post-commissure organs and in fine fibres termed the peri-

cardial organs by Alexandrowicz (1953), Alexandrowicz & Carlisle (1953), and

Maynard & Welsh (1959).

There has been an almost unanimous acceptance of the conclusions of

Bliss (1951), Passano (1951), Bliss & Welsh (1952), and Bliss, Durand &

Welsh (1954) that the different hormones secreted in the central nervous

system travel along axons which eventually terminate in the sinus gland

located in each eyestalk. Accordingly, the earlier hypothesis that the sinus

glands are endocrine organs is no longer considered to be valid, and most

authorities now regard them as reservoirs from which neurosecretions are

subsequently distributed to the body by the circulating blood. Gabe (1954),

however, has questioned the value of some of the histological techniques used

to determine the presence of neurosecretions and, while conceding that neuro-

secretions are conveyed to and stored in the sinus gland, he is convinced that

the sinus gland itself is also the site of active secretion. In this connexion,

Carlisle & Knowles (1959) have remarked that biochemical changes of the

substances stored in the sinus gland are possible, but that secretion of material

by the sinus gland has yet to be proved.

The number of hormones produced is not known, but information supplied

by various investigators suggests that the pericardial organs influence the

pulsation of the heart and that the blood-borne neurosecretions released from

the sinus gland control manifold activities such as chromatophore responses,

retinal pigment migration, growth, water balance, moulting, sexual differentia-

tion, and the female reproductive cycle. According to Carlisle (1959) and

Welsh (1961), five or six distinct types of neurosecretory cells have been

detected in the X-organ which is located in the lobus opticus, while Carlisle

(1959) has distinguished at least four constituents in the tissue of the sinus gland.

From this it has been concluded that the X-organ alone probably produces

several different kinds of neurosecretions, the best known of which is the moult-

inhibiting hormone.

I. PERICARDIAL ORGANS

A detailed examination of the bilateral pericardial organ of Jasus was not

undertaken, but part of it, the lateral pericardial plexus, has been described

briefly (p. 167) and depicted diagrammatically (fig. 64). Since the discovery

by Alexandrowicz (1953) of a system of delicate, ramifying nerve fibres in the

pericardial cavity of a variety of crustaceans and their designation as peri-

cardial organs, evidence has been provided by Alexandrowicz & Carlisle (1953)

and Maynard & Welsh (1959) that they are the source of certain substances

which stimulate the acceleration of the heart-beat. The fine plexuses making

198 ANNALS OF THE SOUTH AFRICAN MUSEUM

up the pericardial organs usually extend over the branchio-pericardial openings

and surround the suspensory ligaments of the heart, and it has been concluded

by the above investigators that they are neurosecretory in function and that

active substances are released from their nerve endings into the blood before

it enters the heart.

2. POST-COMMISSURE ORGANS

In addition to the X organ-sinus gland complex, Carlisle & Knowles

(1959) have supplied details of other neurosecretory centres called the post-

commissure organs. It is stated that they have not yet been found in Brachyura,

but they have been described in Penaeus braziliensis, Palaemon (Leander) serratus,

and Sqguilla mantis as a pair of small, thin lamellae arising from the post-

oesophageal commissure. In these species a fine nerve passes from each lamella

to a dorso-ventral muscle, and the lamella itself contains a number of delicate,

branched nerve fibres, some of which are apparently neurosecretory and are

connected with fibre tracts from the brain. From histological and experimental

evidence, these investigators have suggested that chromactivating substances

manufactured in the brain are passed to the post-commissure organs and

released into a neighbouring haemal sinus.

Post-commissure organs superficially resembling those of Palaemon serratus

are present in the puerulus stage and the adult of asus (fig. 61). They are

continuous, however, with the anterior rather than with the posterior margin

of the post-oesophageal commissure, and are not interconnected by a transverse

lamella. Each is a minute triangular plate with its base attached to the post-

oesophageal commissure, from which it receives several fibres; the latter ramify

within the lamella and are dotted with elongate-oval nuclei. Projecting forward

and upward towards the posterior wall of the oesophagus, the lamella tapers

to a delicate nerve which curves round the ventral pyloric dilator muscle of the

fore-gut and may give off a delicate branch to the oesophageal wall. In front of

the ventral pyloric dilator muscle it turns outward and upward and becomes

applied to the anterior dorso-ventral muscle, to which in some dissections it

seemed to supply several fine fibres. Its termination was not determined, but

the overall impression was that it was associated with a delicate plexus lying

on the anterior dorso-ventral muscle, and anterior to this it appeared to extend

to connective tissue strands in the vicinity of the mandibular minor abductor

muscle or even to a nerve plexus on the bladder of the antennal gland.

The physiology of the post-commissure organs of Jasus is unknown, and

any speculation as to their purpose can only be based on the conclusions of

Carlisle & Knowles (1959) concerning their probable function in other species.

Experiments performed by these authors and other investigators cited by them

indicate that colour changes in a number of crustaceans are regulated by blood-

borne hormones. Activating substances have been extracted from the sinus

glands and the post-commissure organs and, apart from their effect on chro-

matophores, certain hormones are apparently implicated in the regulation of

THE ANATOMY OF THE CAPE ROCK LOBSTER 199

movements of the retinal pigments. Extracts of the sinus gland have been found

by Kleinholz (1961) to influence the migration of the distal retinal pigment of

Palaemonetes, but probably only evoke movements of the pigment from a dark-

adapted to a light-adapted position. On the other hand, evidence that the post-

commissure organs are a possible source of a dark-adapting hormone for the

distal retinal pigment and also of one controlling movements of the reflecting

or tapetal pigment of the eye has been discussed by Carlisle & Knowles (1959)

and Kleinholz (1961). Assuming that similar principles broadly prevail in

Jasus, it seems likely that some hormones destined to control movements of

retinal pigments may be released from the post-commissure organs.

3. SINUS GLAND

In both the puerulus stage and the adult of Fasus the sinus gland is clearly

defined as a flat object which is slightly thicker distally. In dissections of the

adult eye it stands out against the other tissues as a snowy white, spongy disc,

measuring roughly 800 to goo y in diameter and go p thick in an eye with an

optic cup 4 mm long and, excluding the eyestalk, a total length of 7-25 mm.

Compared with the puerulus stage (fig. 71), the optic ganglia of the adult

(figs 59, 61) occupy a smaller area of the optic cup, being proportionally

narrower and rather more widely separated from one another; but, as in Pyle’s

(1943) observations of various developmental stages of Homarus, this structural

change has no effect on the location of the sinus gland. Brown (1944) has

indicated, however, that its position relative to the optic ganglia varies with the

species, and from his remarks it would appear that the site of the sinus gland of

jasus corresponds more with the arrangement in certain Brachyura than with

that of other Macrura. It is more prominent in the adult (figs 59, 61) than in

the puerulus stage, but in both it is situated dorso-laterally on the inner wall

of the peripheral haemal sinus near the proximal radial sinus and in line with

the medulla interna and the distal part of the medulla terminalis.

Microscopic examination of thin serial sections of the adult sinus gland

gives the impression of a histologically nondescript object enclosed in a flat

connective tissue sheath. Its main components are variously sized, compactly

arranged, homogeneous masses, which have staining properties somewhat

similar to the neuropiles of the lobus opticus and are doubtless comparable to

the swollen endings of the axons of the neurosecretory cells described in other

decapods by Bliss & Welsh (1952), Bliss, Durand & Welsh (1954), Carlisle

(1959), Passano (1960), and Welsh (1961). They seem to be partly interlaced

by a delicate, loose connective tissue and interspersed by a number of nuclei

which may be associated with the connective tissue. The presence of nuclei

in the sinus gland has sometimes been disputed, but Gabe’s (1954) recognition

of their reality has been confirmed by Carlisle (1959) and Carlisle & Knowles

(1959). In striking contrast to the bulk of the tissue are intensively stained,

oval or rod-shaped aggregations of basophilic particles; these are rather

irregularly distributed throughout the gland, but tend to accumulate towards

200 ANNALS OF THE SOUTH AFRICAN MUSEUM

its proximal end and, following the conclusions of the aforementioned autho-

rities, may be considered as manifestations of the passage of neurosecretions

into the gland.

The organ is slightly separated from the neurilemma of the lobus opticus

but joined to it by connective tissue strands and, although it lacks the obvious

radiating, digitiform processes of other Decapoda mentioned by Hanstrém

(1939), Welsh (1941), and Pyle (1943), there is evidence of a few slender

prolongations extending into the haemal sinus from its distal more swollen end.

As in previously investigated forms, the proximal part of the sinus gland and the

neurosecretory cells of the X-organ in the medulla terminalis are interconnected

by a conspicuous tract of nerve fibres (figs 59, 71) which is well defined in

proximity to the gland by the presence of basophilic granules and can be

traced into the substance of the gland. Based on similar staining effects and their

correlation with experimental evidence, Bliss & Welsh (1952) and Bliss,

Durand & Welsh (1954) have confirmed the earlier suggestion made inde-

pendently by Bliss (1951) and Passano (1951) that the sinus gland fibre tract

conveys hormonal material from the X-organ to the sinus gland where it is

stored and later circulated to parts of the body by the haemal system.

4. X-ORGAN

Clusters of neurosecretory cells, linked by fibre tracts with the sinus gland,

occur in the lobus opticus, particularly in the medulla terminalis, and certain

of these constitute the X-organ. From various publications, it is evident that

the X-organ varies with the species and that it frequently consists of two por-

tions. In an endeavour to resolve some of the confusion concerning the precise

identification of the X-organ in different Crustacea, Carlisle & Passano (1953)

proposed that the two parts be called the pars distalis X-organi and the pars

ganglionaris X-organi, but it has been indicated by Carlisle & Knowles (1959)

and Passano (1960) that these terms were later changed respectively to the

sensory papilla X-organ or the sensory pore X-organ (SPX) and the medulla

terminalis ganglionaris X-organ (MTGX). The former is homologous to the

X-organ which Hanstrém (1939) found to be closely associated with the

sensory papilla or sensory pore, and which he postulated was a modification

of the sensory cells of the eye papilla. On the other hand, the MTGX, which is

comparable to the X-organ described by Bliss & Welsh (1952) in Gecarcinus

lateralis, is usually located ventro-proximally in the medulla terminalis and is

typically connected with the sinus gland by the previously mentioned obvious

fibre tract.

Cytological and functional differences are also attributed to the two

portions of the X-organ. The SPX is said by Carlisle & Knowles (1959) and

Passano (1960) to contain the sensory cells of the sensory papilla or pore,

certain secretory cells and, more characteristically, the so-called ‘onion bodies’.

Although its precise function is problematic, these authors have indicated that

in some species it may act as a storage and release centre for a moult-accelerating

THE ANATOMY OF THE CAPE ROCK LOBSTER 201

hormone which is produced in the MTGX and the central nervous system, but

is only effective during the proecdysis stage of the moult cycle. The MTGX is

distinguished from the SPX by its large neurosecretory cells, the chief deriva-

tive of which is apparently the moult-inhibiting hormone that prevents

initiation of proecdysis.

Three types of neurosecretory cells, alpha, beta and gamma, have been

described by Enami (1951) in the central nervous system and optic ganglia

of the crab, Sesarma haematocheir, while Durand (1956) has detected four distinct

kinds, Types 1 to 4, in the crayfish Orconectes virilis, and in Pandalus borealis

Carlisle (1959) has differentiated five kinds, of which Type IV is characteristic

of female and non-sexual specimens. Durand has shown that his cellular

Types 1 and 2 occur respectively in the distal and proximal regions of the

X-organ of Orconectes, and that the other two types are distributed elsewhere

in the optic ganglia and the brain. As only giant beta neurosecretory cells

were found by Enami in the X-organ of Sesarma, Durand has concluded that

these are comparable to his Type 2 cells and that Types 3 and 4 are similar to

the alpha and gamma neurosecretory cells described by Enami. Specific

variation could account for cytological differences in the X-organ of these two

decapods, or they could be explained by the observations of Carlisle & Passano

(1953) and others that in Natantia and in Reptantia (except Brachyura) the

SPX and MTGX are disconnected entities, whereas in Brachyura they are

combined in a single mass. Although the two parts of the X-organ were not

specified by Durand (1956), the regional localization of Types 1 and 2 neuro-

secretory cells might be interpreted as a possible differentiation of SPX and

MTGX components of the X-organ in Orconectes. This conjecture seems to be

invalidated, however, by Passano’s (1960) illustration of two kinds of neuro-

secretory cells in the MTGX of Sesarma reticulatum and, as these have been

likened provisionally to Durand’s first two types of cells, it appears that there is

little cytological difference between the X-organ of the species of Brachyura and

Astacura so far investigated. To some extent this conclusion is compatible with

Carlisle & Knowles’ (1959) statement that in these two groups the SPX is

either reduced or absent.

An investigation of the neurosecretory system of asus was not originally

intended but, even with routine staining procedures, the large neurosecretory

cells are easily distinguished from the smaller, normal ganglionic cells. They

were observed in sections of the lobus opticus of the adult, and in the lobus

opticus, the brain, and the ganglia of the ventral nerve cord of the puerulus

stage (figs 58, 71), and may also occur in the peripheral zone of the superior ven-

tricular ganglion and in the oesophageal ganglion of the stomatogastric nervous

system of the puerulus. In the absence of critical differentiation of cytological

details in the present preparations, illustrations of the cells have been omitted,

but they are generally similar to those described in other decapods, and a brief

survey of their association with the optic ganglia may not be inappropriate. It

is immediately apparent that there are several clusters of neurosecretory cells,

202 ANNALS OF THE SOUTH AFRICAN MUSEUM

some of which are located dorsally and ventrally at different levels in the

medulla terminalis, while others occur more distally around the medulla

interna and the medulla externa. Although differing in detail, the scattered

distribution of these groups of neurosecretory cells (fig. 59) is somewhat similar

to that mapped out by Bliss & Welsh (1952) and Bliss, Durand & Welsh (1954)

for Gecarcinus lateralis and Orconectes (Cambarus) virilis but, on the whole, the

arrangement seems to be closer to that of the former than that of the latter

species. Owing to the irregular occurrence of basophilic granules along the

axonal tracts from the various cell groups, not all of them were determined

even in sections counterstained with phloxine; but it is evident that most of

the tracts lead by devious routes to the sinus gland and that the one connecting

the neurosecretory cells of the MTGX with the sinus gland is the most con-

spicuous.

As the eye papilla is obvious in the puerulus stage, it is possible to differen-

tiate between the distal SPX and the proximal MTGX portions of the X-organ

in sections through the medulla terminalis. Numerous subepidermal sensory

cells, with their axons passing inward towards the medulla terminalis, make up

the core of the eye papilla, and nearer its base there is an outer, well-defined

band of deeply stained nuclei which eventually becomes confluent with the

neurilemma of the medulla terminalis. Anteriorly the eye papilla is provided

with a medial, hyaline membrane, but in more posterior sections through the

base of the papilla this seems to break down and continuity between the eye

papilla and the distal region of the medulla terminalis is established. At this

point, which is some distance from the proximal neurosecretory cells that

presumably constitute the MTGX of the puerulus stage, further cellular ele-

ments become apparent at the distal edge of the medulla terminalis. These

comprise a number of fairly large secretory cells and several conspicuous,

rounded or oval bodies measuring approximately 33 to 35 p or less across. Most

of the latter contain concentric lamellae, and it is assumed that they are

analogous to the so-called ‘onion bodies’ of the SPX of other decapods which,

according to Carlisle & Knowles (1959) and Passano (1960), are regarded

either as the coiled terminations of the axons of the MTGX and the brain

neurosecretory cells or as accumulations of secretory products.

With the disappearance of the eye papilla, the SPX is more difficult to

determine in the adult, but in a position comparable with that of the SPX of

the puerulus stage certain cellular structures are differentiated at the frontal

and distal part of the medulla terminalis. They occupy an area which is

approximately 270 to 300 y» thick and has maximum length and breadth

measurements of 330 » and 290 » and, as is diagrammatically indicated in

figure 59, it is not connected with the outer surface of the optic cup. It is partly

surrounded by a delicate membrane and contains a number of probable

sensory cells, but is largely filled by conspicuous, oval or irregularly-shaped,

contiguous elements, measuring from 46 to 60 p» long by 26 to 40 » wide. In

several of these the contents are slightly laminated, but the concentric layers

THE ANATOMY OF THE CAPE ROCK LOBSTER 203

of typical SPX ‘onion bodies’ are not discernible and the majority most closely

resemble the epithelioid cells in the SPX of Lysmata seticaudata (Carlisle &

Knowles, 1959). Some of them are markedly vacuolated and in others the

cytoplasm contains basophilic granules which, by analogy with the staining

reactions of the sinus gland, may demonstrate the presence of secretory material.

As in other species described by Carlisle (1959) and Carlisle & Knowles (1959),

an X-organ connective is probably present, but it seems to be obscured by

blood vessels.

The neurosecretory cells in different parts of the adult lobus opticus (fig.

59) are impressive by their size, which ranges from 27 to 66 y». Some are almost

spherical in section but many which show the conspicuous axon are more or

less pyriform in outline. Each is characterized by a large spherical nucleus

which may or may not be concentric and varies in size with the cell body,

being from 8 to 15 » in diameter. The nuclear membrane is distinct and

encloses a clear nucleoplasm which commonly contains a single deeply-staining

body, probably a karyosome, and sometimes a number of chromatin granules.

The cells forming a cluster proximo-ventrally in the medulla terminalis (fig. 59)

and partly separated from the SPX by normal neurones are most obviously

connected with the sinus gland and are considered to correspond to the MTGX

cells of other decapods. The majority of the cells in this cluster are somewhat

pyriform in shape and vary from 32 to about 40 y» in length; the nucleus is

11 to 15 » in diameter and may contain chromatin granules as well as a large,

slightly eccentric karyosome. The cytoplasm of these neurosecretory cells is

decidedly flocculent in appearance and resembles the ‘mulberry’ formations

described by Carlisle (1959) in the neurosecretory cells of Pandalus borealis.

In the neurosecretory cells of other groups the cytoplasm is only slightly flaky

and tends to be more homogeneous with a fine network of granular inclusions.

The MTGX cells are by no means the largest of the neurosecretory cells, for a

few rounded cells, 60 » in diameter, and couple of ‘giant’ pyriform cells, 66 »

long, were observed among average-sized neurosecretory cells near the distal

margin of the medulla terminalis in longitudinal sections passing approxi-

mately through the middle of the lobus opticus. In these cells the cytoplasm is

not markedly flocculent; the nucleus measures about 13-3 to 15 yw in diameter,

its sharply defined karyosome is eccentric, and there are no obvious chromatin

granules in the nucleoplasm. The similarity between the neurosecretory cells

observed in Jasus and those described by Enami (1951) and Durand (1956) is

uncertain, but it is probable that the MTGX neurosecretory cells are com-

parable with the cells of Durand’s Type 2, and those in other groups may con-

form to his Type 3. Although there are few, if any, corresponding to his Type 4

cells, a cluster of neurosecretory cells lying proximo-ventral to the sinus gland

contains several small rounded cells, 15-5 to 22 w in diameter, in some of which

a deeply-stained basophilic mass almost fills the cell body, obscures the nucleus,

and extends into the axon.

204 ANNALS OF THE SOUTH AFRICAN MUSEUM

5. Y-ORGAN

This term was proposed by Gabe (1953, 1956) for a paired organ which

he observed in fifty-eight species of Malacostraca and considered to be similar

to the prothoracic or moulting gland of insects. He has shown that in Decapoda

and other Malacostraca in which the adult excretory organs are antennal

glands the Y-organ occurs in the second maxillary segment, but is found in the

antennal segment in forms having maxillary excretory organs in the adult.

Specific variations in its size, shape, and microscopic details have been reported,

but it is generally located near the ventral body wall and has been interpreted

by Gabe as a thickening of the hypodermis. Since Gabe’s discovery, the Y-organ

has been described in certain species by other investigators. According to

Chaudonneret (1956), in Orconectes limosus (Cambarus affinis) it is an elongated

mass situated between the mandible and the first maxilla and measures 1-6 mm

long, 0-6 mm wide, and 0-7 mm high: Passano (1960) has mentioned that the

Y-organ of Carcinus maenas is an ovoid structure which measures about 0-5 mm

across and is located near the anterior end of the branchial chamber ventral

to the mandibular posterior (external) adductor muscle.

In the adult 7. lalandi the Y-organ is about 8 mm long by 4 mm high, but

even in immature specimens with a cephalothoracic length of 33 mm it is

larger than that of either Orconectes or Carcinus and measures approximately

2-5 mm long by 0-75 mm wide. In the puerulus stage it is proportionally

smaller, being about 310 to 370 uw long and 90 pz wide in specimens having a

cephalothoracic length of g mm. It seems to be less compact than that of

Carcinus maenas (Passano, 1960), and in surface view (fig. 75) has the appearance

of whitish, convoluted ridges arranged in a slight crescent towards the posterior

Joluaysod

Fic. 75. Surface view of left Y-organ as

seen on a portion of the body wall at the

junction of the branchial and pre-

branchial chambers in a juvenile speci-

men with a cephalothoracic length of

33 mm.

end of the prebranchial chamber. It lies almost horizontally near the anterior

limit of the epimeral attractor muscle and is also close to the maxillary epimera

and the base of the second maxilla. Unlike that of Carcinus maenas (Passano,

1960), it is some distance from the mandibular posterior adductor muscle, but

the posterior dorso-ventral muscle is inserted directly above it, and adjacent

THE ANATOMY OF THE CAPE ROCK LOBSTER 205

to its inner margin (fig. 76) the lateral diverticulum of the dorsal lobe of the

digestive gland bulges into the anterior part of the branchiostegite.

Gabe (1953) has stated that the Y-organ is innervated from the sub-

oesophageal ganglion, while Chaudonneret’s (1956) assertion that in Orconectes

it is supplied by a branch of the first maxillary nerve would seem to imply that

it is a derivative of the first and not of the second maxillary segment. Despite

repeated search, no nerve supply to the Y-organ was detected in F. lalandii. The

nearest nerve is the first dorsal, but this bends back to the epidermis and the

epimeral attractor muscle at the posterior edge of the Y-organ without

branching to it. Nevertheless, this observation is consistent with Passano’s

(1960) remarks that, although two nerves from the suboesophageal ganglion

run close to the Y-organ of Carcinus maenas, there is no evidence that either of

them innervates it.

Sections of the puerulus stage indicate that the Y-organ (fig. 76) is a

folded, somewhat villiform invagination of the inner epidermis of the branchio-

digestive gland

epidermis

cuticle

Fic. 76. Section of inner wall of branchiostegite of

puerulus stage showing position of Y-organ.

stegite and that it apparently consists of elongate, compressed cells with small,

rounded or oval, basal nuclei. Unlike Gabe’s (1956) preparations, the cell

membranes are indistinct, but they are probably delineated by numerous

faint striations between the nuclear stratum and the cuticle.

Cytological changes in the Y-organ during the moult cycle were observed

by Gabe (1953, 1956), and his surmise that the Y-organ plays an important

role in regulating ecdysis has been confirmed experimentally in brachyurans

by Echalier (1954, 1955), Carlisle (1957), and Carlisle & Knowles (1959). It

has been shown by Carlisle (1957) that the spider crab, Maja squinado, habitually

ceases to moult on attaining sexual maturity, and this is directly correlated

with the atrophy of the Y-organ after the last moult. Contrasted with this,

sexually mature Carcinus maenas undergo several additional ecdyses before they

206 ANNALS OF THE SOUTH AFRICAN MUSEUM

reach a stage in which moulting is permanently stopped, probably owing to the

suppression of the activity of the Y-organ by the increased production of the

moult-inhibiting hormone in the X organ-sinus gland complex. From these

and other observations mentioned by Passano (1960), the various investigators

have suggested that the crustacean Y-organ serves as a moulting gland which

initiates certain histological and physiological changes during the proecdysial

stage. Apparently, active secretion by the Y-organ is checked by the moult-

inhibiting factor produced in the X organ-sinus gland complex, but it may be

stimulated by the moult-accelerating hormone released from the SPX organ.

In addition to deliberations on its function as a moulting gland, there has

been some speculation concerning the significance of the Y-organ during

gametogenesis in Brachyura. Arvy, Echalier, & Gabe (1956) have demon-

strated that, while ablation of the Y-organs in mature Carcinus maenas had no

obvious effect on the gonad, removal of the Y-organs in juvenile crabs resulted

in atrophy of the gonads and tardy gametogenesis in both sexes. There is some

doubt, however, as to whether the gonadal changes in juvenile forms lacking

Y-organs are caused by post-operational disturbance of the general metabolism,

or whether they indicate that the Y-organ is the source of a gonadotropic

hormone that is indispensible to gametogenesis but becomes ineffectual once

the gonad is mature.

Differentiation of the sexes and the development of secondary sexual

characters in Malacostraca have been proved by Charniaux-Cotton (1960)

to be governed by other endocrine secretions. Male sexual features seem to be

contingent on a substance produced by a paired androgenic gland which

occurs on the distal part of the vas deferens. On the other hand, it has been

concluded by Carlisle & Knowles (1959) and Charniaux-Cotton (1960) that

the female reproductive cycle is regulated by the activities of the MTGX

neurosecretory cells, while the development of the female secondary sexual

characters is promoted by a hormone secreted by the ovary.

K. REPRODUCTIVE SYSTEM

Structural differences between the two sexes mentioned in connexion

with various aspects of the external features may now be collated and sum-

marized. The males are usually larger than the females, have a broader cara-

pace and commonly stronger first pereiopods; the genital apertures are on the

fifth pereiopods and the pleopods are uniramous. In the female the abdomen

is broader than that of the male, the genital openings are on the third pereio-

pods, the fifth pereiopods are chelate, and the pleopods are biramous.

Accounts of the reproductive anatomy of asus have previously been

presented by Von Bonde & Marchand (1935), Von Bonde (1936), Fielder

(19645), and Heydorn (1965), and the general configuration of the organs

resembles that of other Palinuridae described by Matthews (1951) and Lindberg

(1955).

The gonads of the two sexes are paired and broadly similar in position

THE ANATOMY OF THE CAPE ROCK LOBSTER 207

and form in juveniles, but differ considerably in size and structure in the

mature state. Even though there are no external indications of sexual dimor-

phism in the puerulus stage, the developing gonads are faintly recognizable in

serial sections (fig. 37), but they are so delicate and histologically indeterminable

that the sex can only be ascertained by tracing the gonoducts towards their

future external openings. In juvenile males and females with a cephalothoracic

length of from 30 to 40 mm the gonads are better defined and similar in

appearance, the ovaries, however, being more distinct than the testes. The

paired immature gonads of either sex are whitish, elongate, narrow, straight

tubes which are interconnected in the mid-line by a short transverse bridge

behind the fore-gut and below the median ophthalmic and antennary arteries.

Combined thus, they are roughly H-shaped in outline with relatively short

anterior and much longer posterior horns. The former lie ventro-laterally in

the cephalothorax, curving on either side between the mandibular posterior

adductor muscle and the cardiac fore-gut, to the wall of which their anterior

extremities are secured by delicate connective strands. As they converge

towards the transverse bridge, the two gonads are located more dorsally above

the anterior part of the hind-gut or intestine. Immediately behind the trans-

verse bridge, the posterior horns invariably encircle the hepatic arteries and,

travelling beneath the pericardial septum, they tend to diverge somewhat to

the sides of the hind-gut. They continue towards the hinder end of the cephalo-

thorax and their posterior extremities are usually attached by thin strands in

the first abdominal segment. In the males of Panulirus penicillatus (Matthews,

1951) the testes are likewise anchored anteriorly and posteriorly by delicate

mesenteries.

I. MALE

The mature testes (figs 10, 77) are long, white, highly-convoluted tubes

which are also linked by a narrow transverse bridge and tend to be almost

contiguous for some distance above the anterior region of the hind-gut, The

vas deferens (fig. 77), which runs from each testis to the male aperture, is wider,

more translucent, and less convoluted than the testis. It arises about half way

along the posterior horn of the testis, approximately opposite the fourth pereio-

pod and commonly just anterior to the level of the sternal and the genital

arteries. Its proximal portion is somewhat twisted, but gradually enlarges into

a wider distal part that travels laterally over the first anterior oblique muscle

and the outer slip of the first posterior oblique muscle. It then turns downward,

passing in front of the posterior endosternite in the eighth thoracic segment,

and proceeds between promotor c and levator a and over depressor a muscle

of the fifth pereiopod. Its terminal portion is partly overlapped by the medial

fibres of depressor a muscle that are attached to the proximal rim of the coxopo-

dite. It opens ventrally on the coxopodite of the fifth pereiopod (fig. 2), and its

aperture is guarded by a curved, backwardly-directed, slightly tumid flap.

208 ANNALS OF THE SOUTH AFRICAN MUSEUM

antennule antenna

rostrum

frontal tubercle

pedate process

anterior gastric muscle

proventriculus

dorsal lobé digestive gland—__"# ~NESS Sule posterior gastric muscles

dorsal! dilator of pyloric fore-gut

post. lobe digestive gland

right testis

dorsal abdominal artery

branchiostegite

- Res

segmental artery. BS Nia

Pies

SS ——

central muscle

branchial membrane

vas deferens

ant. oblique muscle

abdom. seg.1

hind-gut (intestine)

uxiliary muscles

“ww OS

ant. oblique muscles

abdom. seg. 6

ventral rotator uropodos

V2,

va part of dorsal

vy rotator uropodos

Saat

v v

¥- ¥

ah eae A

Ww.

y Vv

Fic. 77. Dorsal view of dissection of small male; the heart and the extensor and mandibular

muscles have been removed.

THE ANATOMY OF THE CAPE ROCK LOBSTER 209

2. FEMALE

The ovaries are always more conspicuous than the testes, but are also

suspended anteriorly to the cardiac fore-gut and posteriorly in the abdomen

and are similarly more or less H-shaped (fig. 79). In juvenile animals they are

whitish, narrow, and practically straight tubes which terminate in the first

abdominal segment. As the eggs ripen, the ovaries gradually change in colour

and shape, and in mature specimens they are bright coral-red in colour and so

greatly enlarged that their convolutions fill most of the cephalothoracic cavity

and almost reach the bases of the antennae (figs 31, 78). The proportionally

hind-gut

Fic. 78. Dorsal view of partly dissected female; the oviducts are represented diagrammatically.

longer posterior horns are often apparently asymmetrical, that of the right side

being continued into the second (fig. 78) or the third abdominal segment

(fig. 31); but this asymmetry generally results from differences in the con-

tortions of the right and left organs and their accommodation in the body

210 ANNALS OF THE SOUTH AFRICAN MUSEUM

cavity, for, when they are displaced and fully spread out, they are almost

similar in length and width. After extrusion of the eggs, the spent ovaries

(fig. 79) are considerably reduced in size, collapsed, and greyish-white in colour.

anterior horn

of right ovary -

left ovary

transverse bridge

Posterior horn

of left ovary right oviduct

left oviduct

Fic. 79. Diagram of spent ovaries of ovigerous female, removed

from body and with the oviducts somewhat laterally extended.

Each oviduct is a relatively short, broad, thin-walled, transparent tube

which passes outward about midway along the posterior horn of the ovary

opposite the third pereiopod. It runs horizontally across the posterior lobe of

the digestive gland and curves downward over the lateral margin of the anterior

thoracic muscle. In most specimens it enters the base of the third pereiopod

anteriorly and describes a course comparable with that of the vas deferens in

the fifth walking leg of the male. Travelling between the promotor and levator

limb muscles, it opens on the ventral base of the coxopodite of the third

pereiopod (fig. 80).

3. SPECULATIONS CONCERNING FERTILIZATION OF THE EGGS

From previous remarks on the external evidences of sexual dimorphism,

it is obvious that the male has no intromittent organs. For this and other reasons

the process of fertilization of the eggs is problematic. In most Macrura sperma-

tophores of some sort or another are deposited on the ventral surface of the

female usually in proximity to the genital apertures, and insemination 1s

assumed to take place as the eggs pass over the spermatophores to their attach-

ment on the setae of the pleopods. The spermatozoa apparently remain viable

within the spermatophores for periods that vary according to the species.

Lloyd & Yonge (1947) have reported that in Crangon crangon (vulgaris) the eggs

are laid within two days of mating, while, according to Hughes & Matthiessen

THE ANATOMY OF THE CAPE ROCK LOBSTER PINE

(1962), the interval between the two processes in Homarus americanus may be

as long as thirteen months.

The spermatophoric matter of Astacus was described by Huxley (1881)

as whitish, vermiform filaments adherent to the posterior thoracic and the

anterior abdominal sterna. Similar whitish, thread-like spermatophores were

reported on the ventral surface of females of American fresh-water crayfishes

by Andrews (1931), who suggested that some secretion released by the female

during oviposition might act on the sperm capsule and so effect liberation of

the spermatozoa. Elongate, complex spermatophoric masses are also known to

occur in Natantia (Lloyd & Yonge, 1947) and in Anomura (Matthews, 1956),

female gonopore

20 mm.

Fic. 80. Thoracic sternum of female, showing position of genital apertures on

third pereiopods.

while even in Brachyura, in which internal fertilization is customary, spermato-

phores have been described by Spalding (1942) as minute, simple, oval struc-

tures that are introduced into the female vagina together with a sperm plug.

One of the first accounts of spermatophores in Palinura is to be found in

Allen’s (1916) article on the habits of Panulirus interruptus (Randall), in which

the spermatozoa are embedded in twisted, tubular spaces in a putty-like mass

which is plastered by the male on to the thoracic sternum between the last

three pairs of pereiopods of the mature female. This seminal mass was stated to

change rapidly in colour and consistency from a whitish, soft material to a

black, hard substance, and an almost identical porous spermatophore has been

described for Panulirus argus (Latreille) by Crawford & De Smidt (1922). In

more recent studies, Matthews (1951, 1954a, 1954b, 1954c) has shown that

mature females of Panulirus penicillatus (Olivier), three species of Scyllaridae, and

Enoplometopus occidentalis (Randall) probably also carry sperm masses for some

time before oviposition begins. From the pitted condition of one spermatophoric

mass examined by him, Matthews considered it likely that the ‘specialized

212 ANNALS OF THE SOUTH AFRICAN MUSEUM

claws’ in the female were used to scrape the hard surface and so release the

spermatozoa.

No such external spermatophores have been reported in F. lalandii and,

as it is not known how fertilization is effected, the matter is still subject to

speculation. Nevertheless, inspection of whole mounts of vasa deferentia,

stained with acetic acid alum-carmine and cleared in oil of wintergreen,

demonstrates that the enlarged distal portion of the duct is filled with an

apparently double, intricately-folded, lacy ribbon; innumerable, minute,

rounded cells, presumably mature spermatozoa, are arranged along the edge

of the frill, and the whole presents some similarity to the spermatophore

described by Matthews (1951) in the vas deferens of Panulirus penicillatus.

As in many other decapods, mating doubtless occurs in secluded places

at night, but it seems to have been witnessed in captive animals by Gilchrist

(19134, 1918) and Von Bonde (1936). The latter investigator assumed that the

seminal fluid was introduced into the female genital apertures, and his con-

clusion that fertilization takes place in the oviducts was based on the absence of

external spermatophores and on an examination of recently laid eggs before

cleavage had started. These eggs were enveloped by a thin inner chorion and a

firmer, outer, ‘chitinous’ membrane; the latter was thought to have been

secreted in the distal part of the oviduct, and Von Bonde therefore suggested

that impregnation could only be effected higher up in the oviduct. According

to Herrick (1911), however, the mature eggs of Homarus are provided with a

single transparent membrane, the chorion, the properties of which were

determined by Yonge (1937) to be those of the endocuticle (‘chitin’). The

outer coat, which is laid down after external fertilization, is epicuticular

(‘cuticular’), and is probably a derivative of the secretion from the tegu-

mentary or cement glands on the pleopods. (It has been pointed out by Dennell

(1960) that the terms ‘cuticle’ and ‘chitin’, used by Yonge and some other

workers, refer more precisely to the epicuticle and the endocuticle respectively.)

The above statements concerning the eggs of 7. lalandit and Homarus are more

or less in accordance with Burkenroad’s (1947) conclusion that in all decapods

fertilization precedes the formation of the egg membranes: but he established

that, of four such membranes in Palaemonetes, the first is produced by the

unfertilized eggs when they are extruded into the sea water, and the third is

only developed in late stages of cleavage.

Although Von Bonde (1936) has mentioned an additional ‘cuticle’, the

outer egg-capsule of 7. lalandii is probably comparable to that of Homarus and

other decapods, in which, as has been indicated above, it is considered to be

formed externally by the tegumentary secretion which also serves to attach the

eggs to the pleopods. Even if this suggestion is correct, it nowise minimizes the

difficulty of attempting to formulate a plausible theory as to how and where

impregnation of the eggs of 7. lalandii takes place. So far as is known, there has

been no direct observation of the process of fertilization in any marine macruran,

but in those Palinura with visible spermatophoric masses and in such forms as

THE ANATOMY OF THE CAPE ROCK LOBSTER 213

the fresh-water crayfish, Cambarus, and the lobster, Homarus, in which the male

has copulatory stylets and the female has an external sperm receptacle, it is

fairly easy to imagine how external fertilization is accomplished. At the same

time, Lloyd & Yonge (1947) have shown that in Crangon crangon spermatophoric

masses are successfully deposited on the ventral surface of the female, even

though the male has no copulatory organs.

In a recent article dealing with the problem of fertilization in Jasus,

Fielder (1964c) has compared certain of its structural features with those of

Panulirus cygnus George, and has concluded that internal impregnation in

Jasus is feasible. However, unlike Brachyura in which internal fertilization

is practised, no spermathecal enlargements were observed on the oviducts, nor

were any spermatophores or spermatozoa detected in the oviducal lumina.

While Fielder’s deductions are well founded, possibly some of them require

elaboration, and a consideration of the variations in the genital apparatus of

other species of Palinura might be useful. He has suggested that the outer

sclerotized rim of the male gonopore in Jasus is erectile and capable of being

used as an intromittent organ. Nevertheless, the aperture is not located at the

tip of this protuberance as would be expected if the structure served as a

genital papilla. Moreover, the chance of its being inserted accurately into the

female aperture seems remote in view of Von Bonde’s (1936) statement that

the brief mating period lasts only 30 to 60 seconds. In this connexion, it is of

interest to note that Lloyd & Yonge (1947) have observed that an even shorter

period of five seconds 1s all that is required in Crangon crangon for the application

of the spermatophores, while the time given by Hughes & Matthiessen (1962)

for the completion of mating in Homarus americanus is five minutes. The male

genital apertures of 7. lalandit and those of the Natal rock lobster, Palinurus

gilchristi Stebb., are relatively small and markedly different from those of the

east coast rock lobster, Panulirus homarus (L.), in which, as in Panulirus cygnus

(Fielder, 1964c), the coxopodite of the fifth pereiopod of the male is modified

ventrally behind the large transverse gonopore and has a broad oval pad with

folded walls, antero-medial to which there is usually a forwardly-projecting

brush of setae. Presumably this is an adaptation in Panulirus for the application

of the spermatophoric matrix to the thoracic sternum of the female, but it

does not seem to be a feature of all species that are known to deposit sperm

packets. As previously mentioned, Matthews (19544, 1954c) has reported hard

spermatophoric masses in Scyllaridae, and an examination of available South

African species belonging to this family indicates that the fifth pereiopods of

the males are unmodified and resemble those of Jasus.

Another interesting feature discussed by Fielder is the difference between

the surface of the thoracic sternum of Jasus and that of Panulirus, from which he

inferred that the smooth sternum of the latter is more suitable for the reception

of a spermatophoric mass than the setose sternum of Jasus. At the same time,

the argument does not seem to be fully upheld by the structure of the thoracic

sternum of Projasus parkeri (George & Grindley) which, apart from the charac-

214 ANNALS OF THE SOUTH AFRICAN MUSEUM

teristic median spines, is practically devoid of setae; admittedly this cannot be

regarded as positive evidence, for the method of fertilization in this species is

unknown, and it is only assumed to be similar to that of Jasus. In available

literature there is also little precise information concerning the mating behaviour

in the genus Palinurus, and again it is supposed that external spermatophores

occur. When compared with 7. lalandii, the thoracic sternum of Palinurus

gilchristt Stebb. is seen to be more tuberculated and less setose, and the valve

over the male genital aperture is somewhat larger, but these dissimilarities are

not considered important enough for assuming that the two species have

different methods of fertilization. Further elucidation of this point may be

derived from an examination of some Scyllaridae in which the female thoracic

sternum seems to be variable. Although it is fairly smooth in Scyllarus martensi

Pfr., it is tuberculate in Scyllarides elisabethae (Ortm.) and setose in Jbacus incisus

(Peron), and, following Matthews’ (19544, 1954c) observations of the habits of

other Scyllaridae, any one of these types of surface is presumably capable of sup-

porting a spermatophoric mass. It was also noticed in S. elisabethae that between

the last two sternal plates there is a medial recess rather resembling a sperm

receptacle, but this is common to both sexes and probably simply represents

a depression caused by a sternal apodeme, such as occurs in 7. lalandit.

Relative to Fielder’s conclusion that the chelae of the fifth pereiopods of

the females of Fasus are too weak to pinch the surface of a hard spermatophoric

mass, the Scyllaridae may be of further significance. In describing the diagnostic

features of South African Decapoda, Barnard (1950) has indicated that in

female Scyllaridae, with the exception of Thenus Leach, there is a small chela

on the fifth pereiopod, and Matthews (19542) considered that it could be used

in Parribacus antarcticus Lund to scarify the hard surface of the spermatophoric

mass. The chelae of South African scyllarids do not appear to be appreciably

stronger than those of 7. lalandii, but, assuming as Fielder suggests, that the

small chelae in asus are only used for grooming the ovigerous pleopods, it is

nevertheless probable that in many Scyllaridea the pointed dactylopodites

would also be able to puncture the spermatophoric mass and so disperse the

spermatozoa.

These remarks contribute little towards the solution of the problem of the

fertilization of the eggs in Jasus, but they demonstrate the variability of struc-

tural details in those Scyllaridea which are thought to produce spermatophoric

masses and, if this is any guide, it would seem that the possibility of external

fertilization occurring in Jasus cannot be excluded. The time lag between

mating and oviposition in 7. lalandii would perhaps provide a significant clue

but, unfortunately, the only records available are conflicting. On the one hand,

the statement by Von Bonde & Marchand (1935: 14) that ‘the eggs appear

beneath the female’s tail immediately after fertilization’, seems to suggest that

mating and oviposition are practically synchronous. On the other hand,

Gilchrist (1918) and Von Bonde (1936) have remarked that oviposition takes

place two or three days after mating: to fulfil the implications of this observa-

THE ANATOMY OF THE CAPE ROCK LOBSTER 215

tion, some form of storage and protection for the spermatozoa would be required

for a period of up to three days. Despite persistent search in this and other

countries, no spermatophores have yet been discovered, and lack of information

on this particular biological detail is the main obstacle to the solution of the

problem. In the absence of copulatory organs and internal spermathecae, it

seems unlikely that Zasus has internal fertilization, but further investigations

into the mating process, the nature of the spermatophores, and the structure of

the spermatozoa are essential before the matter can be settled. A step in this

direction has been taken by Heydorn (1965), who has described the spermatozoa

observed in smears of the contents of the vasa deferentia, and has used com-

parative sperm counts to determine the stage of puberty and to estimate the

reproductive potential of mature males. As has already been indicated, Fielder

(1964c) has presented some interesting arguments in support of Von Bonde’s

(1936) assumption that fertilization in asus is internal. It considered, however,

that studies of the external anatomy of available South African Scyllaridea

suggest that fertilization in 7. lalandii may be external, and that observations

on the mating behaviour of the Natal rock lobster, Palinurus gilchristi Stebb.,

might provide decisive clues.

DEVELOPMENT

It is easy to confirm Von Bonde’s (1936) observation that the fertilized

eggs are provided with stalks which are twisted intricately around bundles of

the long non-plumose setae on the endopodites of the female pleopods. From

Herrick’s (1911) remarks on Homarus and those of Lloyd & Yonge (1947) on

Crangon crangon, it may be assumed that the stalks and the egg-capsules are

secreted by tegumentary glands on the pleopods, but the eggs of 7. lalandi

remain discrete, whereas those of Homarus are agglutinated. While the eggs are

thus anchored to and protected by the female’s abdomen, embryonic develop-

ment proceeds for several months until the first free-swimming larval stage

escapes by rupturing the egg-capsule. It has been established by Von Bonde

(1936) that the time between oviposition and hatching is about 95 days and

that there is an interval of two and a half years in females and five years in

males between hatching and the fully mature state. As yet, there is no published

information concerning the time required for the completion of larval life in

F. lalandu, but Lindberg (1955) has reported that the larvae of Panulirus

interruptus remain planktonic for at least six to nine months, while Balss (1957)

has adduced that the duration of larval development in Palinurus elephas is three

months. The latter period seems to be too short to cover the successive larval

phases of 7. lalandii, and it is probable that the time required will be about the

same as that observed by Lindberg (1955) in Panulirus interruptus.

A cursory examination of the early embryonic development was first made

by Gilchrist (1918), who also gave illustrated particulars (19135, 1916, 1920)

of the sequence of steps in post-embryonic life. A fuller account of the embry-

216 ANNALS OF THE SOUTH AFRICAN MUSEUM

ology and a review of post-embryonic stages later appeared in Von Bonde’s

(1936) article and, as the ontogeny of a number of Scyllaridea is well known,

only the salient features concerning 7. lalandii need be related here.

It has been inferred by both Gilchrist (1913-20) and Von Bonde (1936)

that the stage corresponding to the nauplius is passed in the egg and that the

emergent larva represents a more advanced type in the developmental cycle.

This was described by Gilchrist (19136, 1916) as the naupliosoma, which super-

ficially resembles a nauplius and uses its large, biramous antennae to swim

strongly to the surface of the water during its brief period of existence of only

four to six hours. Its body, which measures 1-7 mm long by 0:72 mm in maxi-

mum width (Von Bonde, 1936), differs from that of a nauplius in being demar-

cated into three tagmata and in having appendages on all but the last two

thoracic segments and the abdominal region: a carapace and conspicuous,

stalked, compound eyes are other distinctive features. An even younger free-

swimming stage, introduced into the cycle and called the prenaupliosoma by

Von Bonde (1936), was observed to last about eight hours before moulting

into the naupliosoma. Reporting the recent discovery of planktonic pre-

naupliosoma larvae, probably referable to Panulirus argus, Sims (1965) has

discussed the question of whether or not these early larvae are normal free-

swimming stages. He has cited a number of instances of their having been

observed in some Scyllaridae and Palinuridae, but has also indicated that

there is no evidence that they are typical of the ontogeny of Panulirus argus. He

has shown, however, that these stages will emerge from developing eggs if the

egg-capsules are broken either accidentally or intentionally, or if the rupture

is effected by unnatural osmotic pressure when the eggs are immersed in dilute

sea water. His suggestion is that in some species they may represent advanced

embryonic stages which are sometimes able to survive if, by chance, they are

released prematurely.

The majority of Scyllaridea hatch in the characteristic phyllosoma or “glass

crab’ stage, which is considered by Calman (1909) and other authorities to be

a peculiar modification of the ‘schizopod’ or ‘mysis’ phase in the developmental

pattern of other decapods. The phyllosoma larva is admirably adapted to

planktonic life, the abdomen being rudimentary and its body consisting mainly

of a dorso-ventrally flattened, highly transparent, somewhat bipartite cephalo-

thorax with three pairs of long, slender, projecting, biramous pereiopods, in

addition to more anterior appendages. The phyllosoma larvae examined by

Gilchrist (1916) and Von Bonde (1936) had a size range of from 1-5 or 1-7 to

37 mm, but the time required for the development of the incipient larva seems

to be variable. While Gilchrist (1913b, 1916) reported that some artificially-

reared, free-swimming naupliosomas moulted at the surface into the first-stage

phyllosoma within four to six hours, the smallest phyllosoma recorded by Von

Bonde (1936) appeared about eight days after the emergence of the pre-

naupliosoma. Apart from the fact that the antennae are no longer locomotory,

the phyllosoma of Fasus has all the essential features of Gilchrist’s naupliosoma,

THE ANATOMY OF THE CAPE ROCK LOBSTER 217

and successive periods of ecdysis and growth are accompanied by improve-

ments in the construction of the anterior appendages, the gradual growth of the

fourth and fifth pairs of pereiopods, and, in later stages, the development of

the abdomen. Gilchrist’s (1916, 1918) conclusion that only the smallest phyllo-

somas are surface dwelling and that after a few days they migrate to the bottom

for an unknown period is reflected in Von Bonde & Marchand’s (1935) tabular

dntennulary flagellay dntenndl flagellum

pereiopods

gastric region of head

cardiac region of carapace

branchiostegite

branchio-cardiac groove

1st abdominal Segment

10 mm.

telson 2k,

Fic. 81. Dorsal view of 22 mm long puerulus stage.

218 ANNALS OF THE SOUTH AFRICAN MUSEUM

summary of events. Using the larval anatomy as a criterion, however, the

accuracy of this deduction seems questionable, but Gilchrist’s qualifying remarks

are less cryptic and are perhaps a truer interpretation of the habits of the larvae.

He observed that the smaller forms were plentiful in inshore waters during the

summer months, while the larger, less abundant stages were collected only in

deeper waters and probably submerged to greater depths at times coinciding

with periodic moulting. It may be suggested that this seems fairly consistent

with the structural characteristics of an organism that is obviously better

equipped for flotation and drifting than for benthic life. Like many other

planktonic forms, the phyllosoma larvae probably perform marked vertical

movements and migrate towards the surface at night; diurnal fluctuations in

depth are therefore to be expected, and records of vertical distribution will

vary in accordance with the times of collection of the samples.

After an undetermined period, the largest phyllosomas undergo radical

anatomical modifications and moult into the first post-larval phase, the

puerulus (fig. 81). A total body length of from 22 to 26 mm for this stage has

been recorded by Gilchrist (1916), who later (1918) mentioned that it frequents

inshore waters. The puerulus differs markedly from the phyllosoma in having

a more compact body which is demarcated into a cephalothorax and a well-

developed abdomen. In all essentials it is a miniature of the adult, but the body

is transparent and relatively smooth, and the carapace is rather flat dorsally

and less rounded laterally than in the adult. It is also a natant, probably a

nektonic form, with the pleopods (fig. 6) capable of being linked together in

pairs by hooks on the appendices internae of the endopodites when they are

thought to function as swimming organs. In a key to the puerulus stage of some

palinurids, Gordon (1953) has indicated that one of the distinguishing features

of the puerulus of Jasus is the absence of a flagellum on the short exopodite of

the third maxilliped. Gilchrist (1916) also described and figured the exopodite

of this appendage as a small unsegmented structure and, while close

inspection of present material confirms its rudimentary condition, there is

evidence of several, incipient, apical annulations which are somewhat similar to

the divisions on the longer, more distinct flagella of the first and second

maxillipeds.

In preparation for the assumption of adult life, the puerulus is succeeded

by a stage differentiated by Gilchrist (1918, 1920) as the fost-puerulus, the

largest of which reared by Von Bonde (1936) measured 32 mm long. As the

coupling hooks of the pleopods have now disappeared, the post-puerulus

presents an even greater likeness to the adult than the puerulus but, as yet, the

pleopods are not sexually dimorphic. Subsequently, calcification of the exo-

skeleton sets in and marks the end of larval life; it is assumed that the animal

then gradually becomes adapted to sublittoral conditions and continues its

activities as a young rock lobster.

THE ANATOMY OF THE CAPE ROCK LOBSTER 219

SUMMARY

The various systems of organs of Jasus lalandii (H. Milne Edwards) have

been studied, and most of the findings have been compared with published

descriptions of the anatomy of other species of decapod Crustacea.

In discussing the external features, an attempt has been made to define

some of the characteristic sclerites in the head region.

The functional significance of the appendages has been touched upon, and

observations of living animals have given an impression of the use of some of the

mouth-parts during feeding.

The parts of the endophragmal skeleton have been described, and an

examination of the cast shells or exuviae, which were obtained after numbers

of captive animals had moulted, shows that certain endoskeletal structures are

resorbed in preparation for ecdysis.

There is a broad resemblance between the complex trunk and appendicular

musculature and that of the few other species of Decapoda of which accounts

are available. Several differences have been noted, and the functions of the

muscles in the movements of the body and the appendages have been indicated.

No important differences were observed between the alimentary tract

and that of related decapods.

Dissections and sections of the antennal glands demonstrate that the end

sac is embedded in the labyrinth. As in other marine Decapoda, a nephridial

canal is absent, and the antennal glands are probably not important in

osmoregulation.

The gills belong to the trichobranchiate type and their serial arrangement

is typical of the Palinuridae. The presence of nephrocytes along certain

branchial channels suggests that the gills are partly excretory in function.

Specimens injected with black indian ink were used to study the main

arteries and the venous sinuses, and from observations of serial sections of the

gills it seems likely that the blood is oxygenated twice as it flows through the

gill filaments. Pericardial pouches, which are important storage organs for

water absorbed during moulting, are continuous with the posterior end of the

pericardial cavity.

An account has been given of the ganglia and the peripheral nerves of

the central nervous system, and the ramifications of the delicate stomatogastric

nervous system have been traced.

Some of the details of the more obvious sense organs, such as the antennu-

lary setae, the statocysts and the compound eyes, have been noted. As in some

other species of Decapoda, a median eye persists in the adult.

In view of recent intensive research on crustacean neurosecretions, some

preliminary observations of the endocrine organs have been included.

The male and female reproductive organs are essentially similar to those

of other Palinuridae. No spermatophores have yet been detected in 7. lalandit,

and it is not known whether fertilization of the eggs takes place internally or

externally.

220 ANNALS OF THE SOUTH AFRICAN MUSEUM

Based mainly on information published by other workers and partly on

direct observations of ecdysis in a number of experimental animals, some facts

concerning the moulting cycle and its relation to the breeding season have

been mentioned, and reference has also been made to early descriptions of the

post-embryonic stages of 7. lalandit.

ACKNOWLEDGEMENTS

The foundation of much of this work was laid in the Zoology Department,

University of Cape Town, and grateful acknowledgements are made of the

facilities enjoyed and the material provided. Completion of the observations

was supported by a grant from the Council for Scientific and Industrial

Research, kindly sponsored by the Director of the South African Museum,

and sincere thanks are tendered for this favour. Warm appreciation is expressed

to Dr. A. E. F. Heydorn, formerly of the Division of Sea Fisheries, Cape Town,

for collecting a number of 22 mm puerulus post-larvae, for supplying several

living adult specimens, and for many interesting discussions on the ecology

and biology of 7. lalandii. Special thanks are also due to Mr. M. J. and Dr.

Mary-Louise Penrith of the Department of Marine Biology, South African

Museum, for some juvenile males and females which they collected in South

West Africa. Tribute must also be paid to Mrs. M. E. Schuster of the Jagger

Library, University of Cape Town, and to Mrs. 8. M. Bruins, the Librarian at

the South African Museum, for assiduous and valuable assistance in tracing

and procuring on loan many publications which were unobtainable in Cape

Town. It is also a pleasure to thank Dr. Isabella Gordon of the British Museum

(Natural History) and Dr. L. B. Holthuis of the Rijksmuseum van Natuurlijke

Historie, Leiden, for their ready response to requests for information concerning

the orthography of Fasus lalandiu (H. Milne Edwards).

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INDEX

Numbers in italics denote pages on which items are illustrated

Abdomen, 6-8, 14, 15, 18, 217

aesthetascs, 27, 162, 180, 181

afferent branchial vessels, 131, 134, 151, 153,

154, 155, 156

afferent filamentar channels, /3/, 132, 153,

154, 156

alae cordis, 137, 139

antennal flagellum, 7, 15, 25, 27, 73, 217

antennal glands, 119-127, 120-123

antennal peduncle, 7, 15, 25, 27, 72, 73

antennulary flagella, 7, 25, 26, 27, 71, 179-

181, 217

antennulary peduncle, 25, 26, 70

anterior fascia, 50

anus, 37, 63, 106, 107, 149

apodemes, 17, 19, 20, 25, 28, 29, 43, 46, 78,

120

appendix interna, 7, 25, 34, 101, 151, 218

apposition eye, 190, 191

arteries:

antennary, 49, 106, 120, 137-139, 140, 141,

142-144, 145

antennulary, /4/, 144

anterior gastric, 141, 143, 145

anterior genital, 145, 146

anterior intestinal, /4/, 143, 145

anterior renal, 120, 141, 144

branchial, 73/, 154, 155

branchiostegal, 14/, 142

cerebral, 142

dorsal abdominal, 49, 106, 137, 138, 140,

141, 145, 146-148, 151, 208, 209

epimeral, /4/, 142

genital, 138, 141, 146

hepatic, 117, 137, 138, 140, 145, 146

lateral abdominal, /41, 146, 147

mandibular, /4/, 143

oculomotor, 144, 158, 194

oesophageal, 144

ophthalmic, 49, 106, 137-139, 140, 141,

145, 158, 174,176, 209

optic, 140, 141, 186, 194, 195, 196

pedal, 148, 749, 150

pleopedal, 141, 147

pleural, 141, 147

posterior gastric, 116, 141, 143

posterior intestinal, /4/, 148

posterior renal, 120, 121, 144

ramus externus, 1/4], 142-145

ramus internus, 141, 142, 143

sternal, 106, 137, 138, 140, 146, 148, 149,

169

subneural, 148, 149, 150

tegumentary, 141, 142, 143

telso-uropedal, 141, 148

arteries (continued)

ventral abdominal, 106, 148, 149, 150, 151

ventral thoracic, 106, 148, 149, 151

vesicular, 120, 144

arthrodial membranes, 9, 15, 18, 20, 23, 25,

26, 32, 46, 64, 65, 69, 70, 73, 79, 92, 98, 102,

106

arthrophragms, 17, 19, 42, 43, 44

autospasy, 35, 36

autotilly, 35, 36

autotomy, 35, 36, 94

Blood circulation (summary), 134, 156

brain, 156, 158

branchial chamber, 16, 128, 129, 132, 151, 155

branchial formula, 130

branchial membrane, 47, 49, 128, 133, 208

branchio-cardiac groove, 10, 15, 16, 217

branchio-pericardial orifices, 50, 155, 156, 198

branchio-pericardial vessels, 57, 52, 134, 151,

1555156

branchiostegite, 10, 15, 16, 17, 49, 128, 129,

TIE ACY ANZ

bulbus arteriosus, 137, 139, 140, 141

Carapace, 7, 8, 10, 15, 16, 120, 217

cephalic apodeme, 19, 44, 46, 51, 58, 78

cephalization, 19

cephalothorax, 7, 9, 13, 16, 17

cervical groove, 8, 10, 15, 16, 47

circum-oesophageal connectives,

163, 164, 174

coelom, 14, 41

colour, 8

compound eyes, 186-194, 186, 188

cor frontale, 67, 140, 741, 159, 174, 175

cuticular setae, 8, 9, 27, 129, 130, 177-184,

179-183 :

157, 159,

Deutocerebrum, /58, 159, 161

digestive gland, 16, 49, 105, 106, 117, 118,

119, 120, 145, 151, 205, 208, 209

distribution, 2, 3, 8

dorsal caecum, 107, 108, 117

Ecdysis, 9-13, 136

efferent branchial vessels, 1/37, 134, 151, 154,

155, 156

efferent filamentar channels, /3/, 132, 153,

154, 156

eggs, 34, 212, 215

endopleurites, 1/7, 19, 42, 43, 44, 151

endosternites, 17, 19, 42, 43, 44, 151

end sac, 119, 121, 122, 127

epibranchial space, 129, 132, 133

229

230

epimera, 16, 17, 18, 19, 22, 23, 42, 71, 162

epipodites, 24, 25, 31, 32, 34, 129, 130, 133,

USI, HSS

epistoma, 7, 17, 19, 20-22, 23, 25, 71, 74, 106

excretory apertures, 15, 17, 23, 28, 37, 120,

125, 129

excretory bladder, 119, 120, 121, 124-126

exhalant apertures, 17, 23, 28, 30, 37, 129, 132,

133

eye papilla, 194, 195, 202

Feeding mechanism, 38—40

female chela, 7, 25, 33, 206, 214

female gonopores, 37, 206, 210, 211

filter chamber, //6, 117

food, 37, 38

food grooves, 107, 108, 109, 114-117

fore-gut, 105, 107, 108, 107-118, 120

fracture plane, 35, 36, 69

Ganglia:

abdominal, 106, 157, 158, 169-173, 171

cardiac, 168, 174

cerebral, 106, 157, 158, 163, 174

frontal, 163, 175

oesophageal, 106, 163, 173, 174

optic, 159, 160, 163, 186, 187, 194, 195,

196, 199-203

paroesophageal, 106, 163, 164, 173, 174

suboesophageal, 44, 157, 164, 174

superior ventricular, 174, 175, 176

thoracic, 157, 158, 164, 168, 169

gastric mill, 105, 707, 108, 115, 117, 118

gill filaments, 130, 737, 134, 153, 154, 156

aU YR i), Pe Pelle Pe eee Ith fe) ilet0)

TEE Nesey, TRE Hae)

Haemocoel, 41, 134, 150

haemocyanin, 134

head segmentation, 13, 14

heart, 47, 49, 106, 134, 135, 137-140, 137,

138, 139, 141, 145, 151, 156, 209

hepatic duct, 105, 106, 108, 117, 118

hind-gut (intestine), 106, 107, 108, 111, 145,

151, 208, 209

hypobranchial space, 129, 132, 133

Jomts; 15,24, 25, 31-33; 69.73, 92,'95

Labrum, 19, 23, 36, 40, 46, 106

labyrinth, 119, 121-125, 120, 121, 123, 127

lamina ganglionaris, 160, 163, 186, 187, 188,

189, 195

Male gonopores, 17, 25, 37, 206, 207, 213

mantle canals, 13], 154, 156

median eye, 1/63, 184, 184-186

medulla externa, 160, 163, 186, 187, 195

medulla interna, 160, 163, 186, 187, 195

ANNALS OF THE SOUTH AFRICAN MUSEUM

medulla terminalis, 1/60, 163, 186, 187, 195

medulla terminalis ganglionaris X-organ

(MTGX), 160, 200-203, 206

mesophragms, 19, 42, 43, 151

metastoma, 22, 23, 36, 40

mid-gut, 105, 107, 108, 111, 117

mouth, 23, 36, 105, 106

muscles:

abdominal superficial ventral, 46, 58, 63,

64, 151

alary, 135, 170

anal compressor, 46, 58, 63, 103, 171, 208

anal dilatator, 46, 58, 63, 103, 171

anterior dorso-ventral, 46, 52

anterior oblique, 46, 49, 51, 55, 56, 57, 58,

59, 64, 106, 151, 208, 209

anterior thoracic, 46, 50, 57, 58, 151

apical, 53, 54, 162, 163

appendicular, 36, 46, 5/, 55, 68-105, 71J,

74, 78, 79, 81, 84, 86, 89, 93, 97, 99, 101,

103, 120, 171

auxiliary, #9, 51, 55, 56, 59, 64, 208

cardiac, 139, 140, 170

central, 46, 51, 52, 55, 56, 58, 59, 60, 208

deeper extensor, 46, 49, 55, 56, 106, 151

deeper thoraco-abdominal, 46, 47, 48, 49,

50, 151

dorsal arthrodial, 54, 55

dorso-lateral, 5/, 56, 58, 61, 62

epimeral attractor, 46, 47, 49, 58, 129, 136,

fore-gut, 111-115, 712, 118°

lateral abdominal, 5/, 55, 65

lateral thoraco-abdominal, 46, 47, 48, 49,

55, 136, 151

ocular, 46, 66, 65-68

oblique transverse, 5/, 56, 58, 61

pericardial pouch, 135, 136

posterior dorso-ventral, 46, 52

posterior oblique, 46, 51, 52, 56, 58, 62, 64,

151

superficial dorsal thoraco-abdominal, 46,

48, 49, 55

superficial extensor, 46, 49, 55, 56, 106, 151

superficial ventral thoraco-abdominal, 46,

53, 58

telson, 62, 63, 103, 171

thoracic superficial ventral, 46, 53, 58

transverse, 46, 51, 56, 58, 60, 61, 151

ventral cephalic, 44, 46, 52, 53

Naupliosoma larva, 26, 27, 184, 186, 216

nephrocytes, 128, 131, 132

nephrostome, 120, 121, 123

nerves:

anal 157. 7a NS

antennary, 106, 157, 158, 159, 162, 163

antennulary, 106, 158, 159, 161, 162

anterior, 157, 171

THE ANATOMY OF THE CAPE ROCK LOBSTER

nerves (continued)

apical, 159, 163

cardiac accelerator, 1/64, 166-168, 174

cardiac inhibitor, 1/64, 166-168, 174

dorsal, 164, 166, 167, 174

dorsal cardiac, 138, 168, 174

dorsal telson, 157, 171, 172

dorsal ventricular, 174, 176

dorso-lateral, 151, 157, 170

genital, 169

hepatic, 174, 176

inferior oesophageal, 163, 173, 174

inferior stomatogastric, 163, 175

inferior ventricular, 163, 174

inner mandibular, /64, 165, 174

intestinal, 157, 171, 173

labral, 163, 173

lateral pericardial plexus, 167, 174, 197

lateral ventricular, 174, 176

Lemoine’s, 1/74, 176

ligamental plexus, 168, 174

maxillary, maxillipedal, 1/64, 166

nervi segmentales aortae, 170

nervi segmentales cordis, 169, 170

oculomotor, 157, 158, 159-161, 160, 163,

186

optic (compound eyes), 106, 157, 158, 159,

160, 163, 186, 187, 195

optic (median eye), 158, 159, 184, 185

outer mandibular, /63, 165, 174

paragnathal, /64, 165, 166

pedal, 157, 164, 169

pleopedal, 157, 170

sinus gland, 1/60, 161

sinus gland fibre tract, 160, 186, 200

statocyst, 161, 162

superior oesophageal, 163, 174, 175

superior stomatogastric, 163, 174, 175

tegumentary, 157, 159, 162, 163

thoracic, 164, 169, 174

uropedal, 157, 171, 172

ventral, 157, 170, 171

ventral telson, 157, 171, 172

vesicular, 163, 174

neurosecretory cells,

200-203

158, 160, 186, 197,

Oesophagus, 105, 107, 108, 116

ommatidia, 186, 188, 187-193

ossicles of fore-gut, 107, 108, 107-111, 118

ostia of heart, 106, 134, 137-139, 151, 155

ovaries, 106, 209, 210

oviducts, 209, 210

oviposition, 11, 12, 214

Paragnaths, 22, 23, 36, 40

paraphragms, 19, 42, 43, 44, 78

pedate processes, 7, 16, 19, 20, 49, 162, 208

pericardial cavity, #7, 134, 135, 151, 155, 156

231

pericardial organs, 167, 197, 198

pericardial pouches, 47, 135, 136, 155

pericardial septum, 135, /5/

phyllosoma larva, 26, 27, 39, 130, 184, 186,

216-218

pleura, 15, 18, 151

pleural muscle chamber, 17, 42, 43

post-commissure organs, 163, 164, 197-199

post-oesophageal commissure, 157, 163, 164

post-puerulus stage, 26, 38, 218

prebranchial chamber, 23, 129, 132, 133

prenaupliosoma larva, 184, 216

press, 107, 108, 110, 116, 117

procephalic processes, 7, 19, 45, 46

protocerebrum, 158, 159, 163

proventriculus, 49, 105, 106, 208, 209

puerulus stage, 26, 34, 129, 130, 184, 194,

217, 218

pyloric ampullae, 107, 108, 110, 116

Respiratory current, 82, 132, 133

retinal pigments, 186, 188, 189-192, 199

rhabdomes, 186, 188, 189, 190, 193

rostrum, 6, 7, 15,16, 19) 49, 162) 208

Scaphognathite, 25, 30, 129, 133

sensory papilla X-organ (SPX), 160, 194,

200-203, 206

setiferous processes, 17, 24, 25, 31, 32, 34, 42,

AON HSS)

sexual dimorphism, 8, 16, 18, 33, 34, 37, 180,

206

sinuses:

abdominal sternal, /5/, 152, 153

branchial, 15/7, 152, 153, 156

cephalic, 150, 158

dorsal abdominal, /5/, 152, 153

dorsal thoracic, 150, 15/7, 152, 156

infrabranchial, 15/, 152, 153, 156

pedal, 7/51, 152, 153, 156

peripheral of eye, 195, 196

pleural, 15/7, 152, 153

radial of eye, 195, 196

thoracic sternal, 134, 150, 757, 152, 156

sinus gland, 11, 160, 161, 163, 186, 192,

196-200

size, 8, 206

sound production, 7, 177

spermatophores, 210-215

squamae, 3, 8, 9, 15, 27

statocyst setae, 182, 183, 184

statocysts, 26, 7/, 162, 178, 181-184, 182

statoliths, 162, 183

sterna, 15, 16, 17, 18, 19, 20-22, 42, 71, 78,

106, 211

sternal canal, 19, 43, 106, 148, 158

sternal muscle chamber, 17, 42, 43

superposition eye, 190, 191

supralabral ridge, 20, 21, 23

232 ANNALS OF THE SOUTH AFRICAN MUSEUM

suspensory ligaments of heart, 47, 137, 138,

139, 198

Tail-fan, 6, 14, 18, 35, 39, 63, 104, 105

teeth of cardiac fore-gut, 107, 108, 109, 116,

118

telson, 7, 14, 15, 35, 49, 58, 103, 106, 171, 208,

PAG

terga, 15, 18, 47

testes, 49, 207, 208

tritocerebrum, 159, 1/63

Wreteryl 205 124125

Valves:

antennal gland, /2/, 123

arterial, 170

cardio-arterial, 139, 140, 170, 176

cardio-pyloric, 107, 108, 111

pyloric, 107, 108, 111, 117

vas deferens, 207, 208

ventral nerve cord, 106, 156, 157, 158, 164,

164-173

X-organ, 11, 760, 196, 197, 200-203

Y-organ, 11, 204, 205, 206

INSTRUCTIONS TO AUTHORS

Based on

CONFERENCE OF BIOLOGICAL EDITORS, COMMITTEE ON FORM AND STYLE, 1960.

Style manual for biological journals. Washington: American Institute of Biological Sciences.

MANUSCRIPT

To be typewritten, double spaced, with good margins, arranged in the following order:

(1) Heading, consisting of informative but brief title, name(s) of author(s), address(es) of

author(s), number of illustrations (plates, figures, enumerated maps and tables) in the article.

(2) Contents. (3) The main text, divided into principal divisions with major headings; sub-

headings to be used sparingly and enumeration of headings to be avoided. (4) Summary.

(5) Acknowledgements. (6) References, as below. (7) Key to lettering of figures. (8) Explana-

tion to plates.

ILLUSTRATIONS

To be reducible to 4? in. x 7 in. (74 in. including caption). A metric scale to appear with

all photographs.

REFERENCES

Harvard system (name and year) to be used: author’s name and year of publication given

in text; full references at the end of the article, arranged alphabetically by names, chronologi-

cally within each name, with suffixes a, 5, etc. to the year for more than one paper by the

same author in that year.

For books give title in italics, edition, volume number, place of publication, publisher.

For journal articles give title of article, title of journal in italics (abbreviated according to

the World list of scientific periodicals. 4th ed. London: Butterworths, 1963), series in

parentheses, volume number, part number (only if independently paged) in parentheses,

pagination.

Examples (note capitalization and punctuation)

BuLtoucH, W. S. 1960. Practical invertebrate anatomy. 2nd ed. London: MacMillan.

FiscHeR, P.-H. 1948. Données sur la résistance et de le vitalité des mollusques. 7. Conch., Paris

83: 100-140.

Fiscuer, P.-H., Duvat, M. & Rarry, A. 1933. Etudes sur les échanges respiratoires des littorines.

Archs Zool. exp. gén. 74: 627-634.

Koun, A. J. 1960a. Ecological notes on Conus (Mollusca: Gastropoda) in the Trincomalee

region of Ceylon. Ann. Mag. nat. Hist. (13) 2: 309-320.

Koun, A. J. 19606. Spawning behaviour, egg masses and larval development in Conus from

the Indian Ocean. Bull. Bingham oceanogr. Coll. 17 (4): 1-51.

THIELE, J. 1910. Mollusca: B. Polyphacophora, Gastropoda marina, Bivalvia. In Schultze, L.

Zoologische und anthropologische Ergebnisse einer Forschungsreise im westlichen und zentralen Siid-

Afrika. 4: 269-270. Jena: Fischer. Denkschr. med.-naturw. Ges. Jena 16: 269-270.

ZOOLOGICAL NOMENCLATURE

To be governed by the rulings of the latest International code of zoological nomenclature issued

by the International Trust for Zoological Nomenclature (particularly articles 22 and 51).

The Harvard system of reference to be used in the synonymy lists, with the full references

incorporated in the list at the end of the article, and not given in contracted form in the

synonymy list.

Example

Scalaria coronata Lamarck, 1816: pl. 451, figs. 5 a, 6; Liste: 11. Turton, 1932: 80