morphology of the genital ducts in female crabs.pdf

8/20/2019 Morphology of the genital ducts in female crabs.pdf

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J.

L ~ ~ z I L .

OC.

ZOOZ.),

7, 312, p 1 ~ . 79-300

With

14 f i g u r e s

Printed ~reat

Britoin

April

1968

Morphology

of

the genital ducts in female crabs

BY

R . HAltTNOLL

ilIarine Biological Station, Port Erin,

I s le of

M a n

( A c c e p t e d or

p u b [ ~ c n t i o v ovember,

1967 )

Corninui xted b y t k r Editorial Secretary

The Brachyura may be separated into two groups by the position of the female genital

openings. I n th e suporfandies Gynmoplenra and DromiaceF they open on the coxae of t,he

t,hird peraeopods, while ill the Oxyst,oniata, ('orystoidea, Brachyrhynchn and Oxyrhq-ncha

they open on the sternum of the rorresponding segment. This paper deals with the str ucture

of tho genital duct s in females of the latte r group. Each duc t, leading

from

the ovary to the

exterior, consists of four regions-oviduct, spermathe ca, vagina and vulva. Two lmsic

patterns of duct, simple arid concave, are recognized by variations in the structure

of

the

vagina. Each may be elaborated by th e prf:sencc of an operculum closing the vulva . These are

described

by

chosen examples, an d some o f t he changes associated with the breeding c y c l ~re

detailed. The distr ibu tion of the two pat,teriis of duct in the various families of Brachq-ura is

examined,

and

the phylogenetic implications considered. The more impor tant of these arc tha t

the Corystoidca is rightly dcsignated a disl inct superfamily, and t1ia.t the Corystoidea-

Portunidae line forms the basic stock of th e Brachyu ra with ste rnal female openings.

COXTENTS

Introduction

.

Terminology

Material and method5

Types of genital duct

Structure and taxonomy

Discussion

Acknowledgetilent,

References

1 .4GX

279

881

18

2 8 2

191

. 298

. 299

.

300

INTRODUCTION

I n the course of investigations into the biology of several groups of crabs various struc-

tural differences in the female genital ducts were observed. At least some of these differ-

ences have a functional basis, and the structure

of

the duct can serve

as

a valuable indicator

of the periods when copulation and ovulation may occur. An understanding

of

this

phenomenon greatly facilitates the study of certain aspects of the biology of the crabs.

The necessary information

was

for the most part not available, and

so

this vork

was

undertaken. This paper deals with the structure of the oviducts, spermathacae antl genital

openings

;

he ovaries have been investigated only

so

far as is necessary to an understanding

of the associated organs.

A

second paper will deal with the functions of these organs.

Within the Decapoda the genital ducts antl spermathecae take several different forms,

which for the most part correspond with the major subdivisions of the order. These are

summarized below

so

as to place the condition found in the Brachyura in perspective.

Suborder Natantia

In all members the oviducts open on the coxae of the sixth thoracic appendages. In the

Pernaeidea there is

a

median spermatheca, linomn

as

the thelycurn. on the thoracic

sternum. This is of varying structure antl elaboration, but always laclis

arig

internal

communication with the oviducts. The rcrgestid

Lucifer,

contrary to

many

earlier

accounts, has a thelycum in the same

way as

the rest

of

the Penaeidea (Gordon, 1956;


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280 R . G.

HARTNOLL

Hartnoll, in press). Apart from the Penaeidea, the Natantia lack a spermatheca. The

spermatophore, uhere one is formed, is large and either inserted into the thelycum or

glued to tlie sternum.

Xuborder

Reptantia

Section Macrura.

The oviducts open on the coxae of the sixth thoracic appendages.

Some possess a spermatheca in the form of a median pi t in th e integument of the thoracic

sternum. The spermatophores are large and gelatinous, and are either inserted in the

spermatheca or glued to the integument. I n

Jasus lalandei

(H. Milne Edwards) it is

possible that the sperniatophores are placed in the oviducts, resulting in internal fer-

tilization (Fielder, 1964; Heydorn, pers. comm.).

Section Anomura.

The oviducts open on the coxae of the sixth thoracic appendages.

and there are no spermathecae. The spermatophores are firm-walled and pendunculate,

and are glued to the integument. A possible exception is Clibanurius

olivaceous

Henderson

in which Kamalaveni (1949)claimed th at the sperms are stored in the oviducts, so permit-

ting internal fertilization.

Section Brachyura. A few of the Brachyura have coxal oviducal openings ; hese have

separate sternal spermathecae and the spermatazoa are carried in a gelatinous matrix.

However. in the majority the oviducts open by paired apertures on the sixth thoracic

sternite, and the spermathecae are enlargements of the oviducts. I n thi s second group the

spermatophores are small rounded capsules produced in large numbers. and th e first two

pairs

of

pleopods of the male are specialized for transferring them to the spermathecae.

Here the eggs are fertilized internally, whereas in almost all other Decapoda fertilization

is external. Thus there are these two types of structu re found within the Brachyura, and

no intermediate conditions, such as sternal oviducal openings with separate sternal

spermatliecae, are known.

The earlier classificationsof the Brachyura, such as th at of Borradaile

(1908),

ncluded

three groups in which the oviducts opened

on

the coxae of tlie sixth thoracic appendages:

1. Subtribe Dromiacea.

2.

Subtribe Oxystomata, family Raninidae.

3.

Subtribe Oxystomata, family Dorippidae, subfamily Tymolinae.

The inclusion of two of these groups in the Oxystomata, together with forms in which the

oviducts opened sternally, tended to lessen the apparent significance of this variation in

genital openings. More recent research revealed further details of their structure though,

resulting in changes in their classification. Bourne (1922) re-examined the Raninidae

and removed them from the Oxystomata to a newly erected superfamily, the Gymno-

pleura. This removal is supported by the differences in the larvae of the Raninidae and

Oxystomata (Williamson, 1965). Gordon (1963, 1966) first described their spermatheca.

a median unpaired pit between the seventh thoracic sternites. Gordon (1950) also dis-

covered the spermathecae in the Dromiacea, paired pockets in the integument between

the seventh and eighth thoracic sternites. When Gordon (1963) studied the Tymolinae

she found that the y resembled the Dromiacea in the form

of

the spermathecae, and pro-

posed that they should be removed from the Oxystomata, elevated to family rank as the

Tymolidae, and placed either in or close to the Dromiacea. These redispositions have had

the effect of giving greater emphasis to the difference in genital openings, as can be seen

by considering a recent classification of the Brachyura (Monod, 1956) which divides i t

into six superfamilies :

Gymnopleura

Dromiacea

Oxystomata

Corystoidea

Brachyrhyncha

Oxyrhyncha.


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Genital

duct5 i j ~e m u l e

crabs

281

The classification

as

given by

blonod

is changed by transferring tlie Tymolinac (repre-

sented by CymoiLomus from the Oxystomata to the Dromiacea. Then thc first two of

these superfamilies contain only forms in which tlie oviducts open coxally, and there are

separate sternal sperniathecae. The last four contain only crabs with sternal oviducal

openings, and with spermathecae

as

enlargements of the oviducts. Regarding those with

sternal openings, there

is

still debate as to the niimber and content of the superfamilies

into which they should be divided

;

there

i 4

little doubt, however, that together they form

a natura l and probably rnonopliyletic group. n hicli could be regarded as the ‘aclranced’

Brachyura. As for the

(3)

mnopleura aiitl Droiniacea, they are not closely

allied

to the

other four superfamilies. and on the ba of theii~ emale genital organs there are no

grounds for regarding tlicm as closely relatctl to each other, nor as primitive Hracli~wira

(Gordon, 1963). Othe r structures, however. indicate that both superfamilies are bracliy-

uran

rather than anoniuran i n their levcl

of

development (Gordon, 19BG

In

atldition.

Williamson (1965) considers, from larval characters, t hat both tlie Honiolirlae And the

Raninidae have affinities with the primitire brachyuran stock. Further discuwion of the

relationships of these ‘pr imitive’ superfanlilies

is

beyond the scope

of

this

paper.

as

it

is

concerned only

n

t11 the four superfainilies of ‘advanced’ Brachpnra-Ox .stor~iata.

Corystoidea, Bracliyrhyncha and Oxyrhyncha.

TEltMIKOLOOY

Previous vorliers have

used

a variety

of’

ternis to describe the parts of the female

reproductive duct s, in some cases giving tliffwent meanings to thc same term. Thus before

proceeding to the descriptive parts

of

the paper it is essential to decidc upon rinrnes for

the structures. and to make their usage clear. In forms such as the Drorniacea, in whicli

the oviducts

and

spcrniatliecae open separately. the terminology is relativcly obvious

/Ovary

Ovary,,

Spamathem

Sperrnathecal

opening

Vulva

Fig.

1 .

Diugrarnrnat

ic

transverse section

o f

t

lir

thoracic region

t o

sliow 1he fcniale genital

organs.

The

left side represents a brachyiiriril with coxal openings, tlie riglit, side one with

sterna l openings.

(Fig 1 . It is in tlie advanced Brarhyiira. nliere the spermatheca is an enlargcwicnt of

the genital duct , that some confusion has arisen. I n these crabs the genital duct leads

from the ovary to t he exterior and consists of fonr regions. First a short region leading

from the ovary. next an enlarged portion 111 which the sperms are stored, then a tube

passing ventrally to the stcrnum and, finally, the opening on the sternite of the sixth

thoracic segment.

The first region, short . narrow and hidden between the ovary and the follm ing enlarged


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282 R.

G. HARTNOLL

region, is the oviduct. It s function is the passage

of

eggs, and the structure of i ts walls

differentiates it from the outer wall of the ovary. Spalding (1942)and Ryan (in press) so

described it, but others have termed

it

the germinal cord (Cronin,

1942;

Hard,

1942)

considering its function the production of oocytes. Although Cronin realized tha t it also

gave rise to the passage from the ovary to the spermatheca.

The enlarged region for the storage of sperms has been variously termed the copulatory

pouch (Broekhuysen, 1936),seminal receptacle (Pyle

&

Cronin, 1950; Ryan, in press) and

sperm sac (Churchill, 1919). The most widely employed name is spermatheca and it is

used in this paper.

The part of the duct leading from the spermatheca to the sternum has been called the

oviduct (Churchill, 1919; Hiatt, 1948; Pearson, 1908; Ryan, in press) and the vagina

(Spalding, 1942). It could perhaps be justifiably regarded as

a

modified portion of the

oviduct, but on the same basis

so

might the spermatheca.

It

is functionally more than

an oviduct, also playing a role in copulation. The term vagina implies this dual function,

and is therefore adopted.

The opening of the vagina on the sternum is sometimes termed the vulva (Broekhuysen,

1936;Hiatt, 1948;Knudsen, 1964;Ryan, in press), but generally referred to as the genital

opening. Vulva, like vagina, has the advantage of specifying the dual role in copulation

and ovulation, and is used in this paper. ‘Genital opening’ is nevertheless a useful term

when it is desired to refer to the Decapoda as a whole, in which both vulvae and oviduct

openings are found. The terminology used in this paper is summarized in Fig. 1 .

MATERIAL AN D METHODS

Representatives of most of the families

of

Brachyura were examined. Most material

Port Royal Laboratory, University of the

W.I. ,

Jamaica; Portaferry Laboratory,

Queens University, Belfast ;Stazione Zoologica, Naples.

In addition some preserved material was examined of families which

I

was unable to

collect. I am grateful to the following for specimens:

Dr

R. B. Manning, U.S. National

Museum-Palicidae ;

Dr

A. L. Rice, British Museum (Natural History)-Hymenoso-

matidae

;

Dr T. R. Williams, Liverpool University-Potamonidae. Complete details

of

the species examined are given in the section dealing with the relation of structure t o

taxonomy.

The form

of

the genital ducts was investigated by dissection, where possible of fresh

material. In smaller specimens he relevant parts were dissected out, stained in Grenacher’s

alum carmine and cleared in xylene. The dissection was then continued under a stereo-

scopic microscope, the fine structures having been rendered much more clearly visible.

Some of the material was sectioned; it was fixed in Bouin

or

Susa, embedded in esterwax

or paraffin wax, and sectioned at 7 to

10 p

on a rotary microtome.

It

was impossible to

obtain good sections of some material due to the thick cuticle, although this had been

decalcified. Celloidin embedding would probably have overcome this difficulty, but the

necessary equipment was not available. Most sections were stained with Mallory triple

stain, which gave good differentiation for histological studies. Others were stained with

haemalum and eosin for cytological detail. Usually serial sections were cu t to enable fine

details to be reconstructed.

was collected personally while working a t the following marine laboratories

:

TYPES

OF

GENITAL DUCT

All members

of

the four superfamilies under consideration have paired vulvae on

the

sixth thoracic sternite.

An

apparent exception is the Palicidae, a family

of

the Brachy-

rhyncha which is alleged to have the vulvae on the fifth thoracic sternite (Borradaile,


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Genital

ducts

in feninle

crabs

283

1908; Bouvier, 1940 and Rathbun,

1918

as the Cymopoliidae). This is discussed below

and i t is shown by a more detailed examination that the openings are present after all

on the sixth segment. In all members the vulva leads via a vagina to a spermathwa, and

this communicates by a short oviduct with the ovary. However there are conxidcrable

differences in the form of these parts, and after examining a variety

oT

crabs

it

became

apparent tha t there were two basic patterns. Most crabs exhibit one of these patterns,

although there are a few atypical cases.

In

this section selected representatives are des-

cribed in detail, while in a later section the other species which were examined are men-

tioned briefly, and their special features of interest pointed out . The two basic patterns

are ‘siniple’ and ‘concave’, and either may be elaborated by the presenceof an operculum

which is either normally mobile or imniobilr. The chosen examples are as folloa.;.

SIMPLE

: Carcinus

maenas

(L. ) .

CONCAVE:i y a s

aratzeus (L.),Hyas coarctatus

Leach.

CONCAVE,

MOBILE OPERCULUM

:

Cyclograpsus integer

(Milne Edw.) .

CONCAVE,MMOBILE OPERCULUM

:Pac hyyra qms marmoratus

Fabr.

All of the descriptions are based upon mature specimens. The structure

of

ininiature

females may differ considerably.

Simp le Pattern

This

is

the only one

of

the three which has previously been described in detail. I t occurs

in

Carciizus m aenu s,

and also in two other species which have been extensively studied,

Cancer pagu rus L.

and

Callinectes sap idus

Rathbun. The reproductive organs of

C‘aizcer

pagurus

were described by Williamson (1899,1904)and Pearson (1908), but not in sufficient

detail to be useful here Those of

Callinectes sap idus

were described by Churchill (1919)

Ovary

VuJvo

Fig. 2.

Carcinu,s W I C I L ( / S . The

female

genital organs

of

the right side

in

postero-lateral

view.

and Cronin (194 ), hile those

of

C a ~ c ~ i n u snuenas have previously been described by

Broekhuysen (1936)and Spalding

(1942),

he la tter giving some details of the spermatheca

and vagina. However, the only comprehensive study of the fernale reproductive organs

of a crab is tha t of

Por tunus sanguinolentus

(Herbst)by Ryan (in press).

A

description of

the organs of

Carciizus maenas

follows. and these results are discussed

~1

ith reference

to

the findings of Bpalding and Ryan.

The general form

of

the reproductire duct is shown in Fig. 2 . The vagina extends


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284

R .

HARTNOLL

dorsally from the vulva as a straight tube, and gradually widens to form the spermatheca.

This is attached to several parts of the arthrophragmal skeleton, and in specimens which

have not recently mated is flattened in the longitudinal plane of the crab. The posterior

arm of the ovary dips ventrally to ru n along the median face of the spermatheca, and then

continues posteriorly. The oviduct

is

hidden between the ovary and spermatheca, and is

only visible in sections. The structure of such a specimen

is

further elaborated in Fig.

3A,

m m

vu

Fig.

3.

C crrc inus

nutenas;

sections in th e transverse plane of the crab, median side to th e left.

A, Female which has not recently mated.

B,

Female which has recent,ly mated.

col, Columnar epithelium; cut, cuticle; epi, upper limit

of

epicuticle;

inus,

muscles sur-

rounding vagina; ov ovary; ovid, oviduct ;

sp,

sperniatheca,;

st,r,

stratified epi thelium; VB,

vagina ; vu, vulva.

a section in the transverse plane

of

the crab. Immediately after copulation the sperm-

atheca is greatly distended by the sperm plug, composed

of

sperms and secretions of the

male reproductive ducts. The appearance changes to that in Fig.

3B, a

section comparable

to the upper part of Fig.

3A.

The sperm plug slowly disintegrates af ter copulation, and

the spermatheca reverts to its flattened form. Thc four regions of the genital duct are

now described in detail.

The oviduct was studied by sections in the transverse and frontal planes of the crab.

It

consists

of

a

convoluted sheet

of

cells lying in connective tissue, one end extending into

the ovary, the other into the stratified epithelium of the spermatheca. The sheet is for the

most par t one cell in thickness, between 7 and 10p thick , and composed of roughly cubical


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Genital

ducts

irr

fevrinle

crubs

285

cells with large oval nuclei. Figure

4

rom a transverse section, shows this convoluted

sheet clearly: the form and extent of the folding varies from section to section. Within

the ovary the oviduct links n th one of thc syncytial germinative zones-a feature

also

observed in other series of sections. This, together wi th its un-ductlilie appearance,

explains why some

of

the previous workers termed i t the germinal cord (Cronin, 1942;

Hard, 1942). Cronin appreciated that the germinal cord found in immature C a l h e c t e s

supidus split to form a tuhular oviduct in the :tdnlt,but was of the opinion tha t this change

was permanent.

Hoii

ever. the careful serial sectioning of several adult females of

Carcirius

0.5 nm

Fig. 4.Carc~tccto u e ~ 1 5 .

An enlarged view o f

portion of

Fig.

3B to show the oviduct.

The

inset in the t op left

i i

a detail of the ovidud wlls.

ovid, Oviclurt

;

str, stratified cpitheliuni

of

rperinntheca

;

syn,

syiicytial zone

of ovary.

failed

t'o

demonstmtc a passage between the luriicns of the ovary and spermatheca. The

reason for this becomes apparent once

t hc

paper by Rya n (in press) was available. He

demonstrated. tha t in Portunus sa,nguiriolentu.y the oviduct is, for most. of the

t

iitie, a f lat

sheet of cells which does

riot'

afford

a

passage for the ova. Shortly before ovulation this

sheet splits to form a wide

tube,

which closes again soon after ovulabiori has occurred.

None of the fclmales of

Cai.cirz.us

sectionetl were near to ovlxlntion, but presumably

a.

sequence of changes occurs similar to t,hose in P . sangu ino len tus .

X

histological c>xamina-

tion

of Corystes c n s n i e e l a u ~ ? z ~ s

ennant rcvealetl that, in this species also thc oviduct, is

of cells, which splits only teniporarily to form a tube at tlhe tiinc

of

ovulation.

The

nail

of

t,he sperniat,heca is of twn parts: tlie upper portion is coinposed of a thick

stratified epitheliuni,

tlie

lower of a chitin la8yerunderlain by a columnar epithelium

(Fig.

3).

The upper part is capable

of

considerable extension to accommodate the sperm


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286

R.

. H~RTNOLL

plug a t the time

of

copulation. Its wall is normally 100 to

200

p thick, and made

up

of

10

to

20

layers of cells. These cells have large rounded nuclei; the outer layers are tight,ly

packed, but the inner layers are loosely held together and are in the process

of

being

str

COI

1mm

spec

I I

Fig. 5 . Carcinus maenas: section of th e spermatheca in th e frontal plane of the crab, th e median

side to t he top.

A,

Region

of

the oviduct, with

a

detail of the stratified epithelium of the

spermatheca.

B, Junction of stratified and cuticular regions.

C

Cuticular region, with

detail

of

its wall.

ar, Arthrophragm; col, columnar epit.helium; cut, cuticle; mus, muscle; ovid, oviduct;

sper, sparmatazoa; str, stratified epithelium.

sloughed

off

into the lumen of the spermatheca (Fig.

5A).

This upper part

of

the sperm-

atheca is shown

in

Fig. 5A,

a

section

on

the frontal plane

at

the level

of

the oviduct.

Figure

5B is

a similar section a t a lower level, with the chitin-lined portion

of

the sperm-

athecal wall showing a t the anterior and posterior margins of the spermathecae. The

chitin layer stains blue with Mallory, and is continuous with and apparently identical to

the procuticle

of

the integument. Beneath it is a single layer

of

columnar cells,

80 to 100 ”


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Genital ducts in emale crabs

287

long and with large oval nuclei. I n still lower sections

(Fig.

5C) the chitin lines the whole

circumference of the spermatheca. This chitinous lining is folded, with particularly com-

plex undulations at the anterior and posterior margins, where the deposits of sperm are

rnus

,-----I

cut

Fig. 6.

Carcmus

m i e n u s . A, Section througli upper pa rt

of

vagina. B, Section through lower

par t

of

vagina.

C

Sternum In ventral viow.

col, Columnar ep ith elu m; cut, cuticle ;mus, muscle; ts 6, sixth thoracic sternite ;vu, vulva.

concentrated. Outside the columnar epithelium is

a

layer

of

connective tissue, which

binds the spermatheca to the arthrophragms (Fig. 5C) . This connective tissue contains

scattered strands of muscle. Ventrally the spermatheca joins the vagina ; a t the junction

the chitin is thrown into large folds, the

most

prominent

of

which arises from the lateral

margin (Fig.

3B).


10/22

288 R. .

HARTNOLL

Cronin 1942)sta ted th at ‘The columnar cells of the ridge between th e dorsal and ventral

cavities are ciliated, and the ridge is crenated’. He was referring t o the region of sperm-

athecal wall in Callinectes between the upper stratified and lower chitin-lined epithelia.

This is very interesting in view of the presumed absence of cilia from the Arthropoda

(if the Onychophora be excluded from the phylum), and accordingly a careful examination

was made of the corresponding rcgion in Carcinus. A study of sections indicated that a

small band of columnar epithelium in this region might be ciliated, just dorsal to the

termination of the chitin layer

;

however, staining with Haedenhain’s haeinotoxylin failed

to demonstrate

a

layer of typical basal bodies. Some freshly removed spermathecae were

opened and examined under sea-water, and there appeared to be a feeble transportation

of surface particles in this region, though by no means amounting to a distinct current,

A definite decision could be obtained only by electron microscopy, and material mas

sectioned and photographed by Dr L. T. Threadgold of the Zoology Department, Queens

University, Belfast. The results showed th at the cells in question have the outer boundary

prolonged into numerous microvilli and pseudopodia, which explain the light microscope

observations, but cilia were definitely not present.

It

assumed th at similar structures in

Callinectes sapi dus were responsible for Cronin’s observations.

The vagina runs straight down from the spermatheca to the vulva, and is lined through-

out by the chitinous procuticle and columnar epithelium which form the lower part of the

spermatheca. The portion nearest the vulva has in addition,

as

its innermost layer, &thin

layer of epicuticle (staining red with Mallory) continuous with that of the integument

(Fig,3A). The lumen of the vagina is irregular dorsally (Fig .6A) but becomes smoothly

oval ventrally (Fig. 6B). Throughout i ts length the vagina is sheathed by a layer of con-

nective tissue containing numerous blocks of spiral muscle. Near the vulva these muscles

run parallel to the vagina rather than spirally, and those on its lateral side are attached to

the sternurn some distance from the vulva (Fig. 3A).

The vulvae are transverse slits in the sterni te of the sixth thoracic segment (Fig. 6C) .

Each is rounded laterally and pointed medially, and in

a

female of

70

mm carapace width

measures

2 . 5

mm by

0.8

mm. The margin of the vulva is the rigid integument of the

sternum, while the lumen is normally blocked by bulges of the flexible integument which

comprises the lining

of

the vagina.

The above description confirms the account of Spalding

(1942)

in most respects, while

entering into considerably greater detail. The only major point of difference is th at

Spaldirig implies tha t the ovary is open to the spermatheca

at

all times, although in his

account i t is not clear which structures he refers to as the oviduct. The present work, on

the other hand, demonstrates that there is not a permanent opening. Ry an (in press)

deals with Por tunu s sanguinolentus, like Carcinus a member of the Portunidae, and des-

cribes a very similar series of structures. He gives details

of

the cyclical changes affecting

the reproductive ducts during moulting and ovulation, and there is reason to believe th at

cssentially the same phenomena occur in Carcinus.

Concave pattern

This form of genital duct has only been previously described once to my knowledge.

by Hoestlandt (1948) n his study of Eriocheir

sinensis

Milne Edw. : ‘L’extrkmiti ventrale

de cet oviducte s’achkve en un conduit chitineux et calcifii de 4 mni de longeur qui aboutit

I’orifice sexuel. Cette extrkmite est formBe par la paroi cylindrique de l’oviducte dont

la face extkrieure est fortement calcifike; le c6tB opposi reste plus souple, s’invagine et

s’accole la face interne du pri ci dent. Les muscles vont de l’exo-sequelette

ii

la paroi

invagin6e. Leur contraction peut permettre d’ &carter ces deux parties l’une de l’autre

pour le passage des oeufs et, si le pression n’est pas assez forte,

pour

la pkn6tration du

sperme.’ This description summarizes neatly the two distinctive features of th e concave

pat tern, namely the invagination of one side of the vaginal wall into the other, and the

concentration of the vaginal muscle to one side and i ts attachment t o the invaginated


11/22

Genital duc fs in fenicxle crabb

289

wall.

The

folloa ing account

IS

based on llicl

t \\

o 13ritish specic'h of tlic ,pitlei -crab I l y n s ,

H . uraneus

(L.)and

H . coarctatus

Leach

The general structu re is shown in Fig.

7 A

The posterior branch

of the ovary

gives

off

a ventral projection which lies along the median side of the sperinatheca The sperinatheca

and vagina

are

clearly demarcated. the forrncr being swollen or flattened according to the

length

of

time since copulation The vagina

runs

from th e sperniatlicca t o the ste rnum,

and one

face is invaginatecl into the

othei*.

he tx o

bcing

kno nn as the inner and

oiitcr

alls respectively. The inuscles run diawiial ly from the inner

u

all to tlir sternuiii.

Figure

7B

is a scction of

t h ~ b ~

arth in

tlrc.

ti;mswrre plane

of

the c r a h

mus

Big. 7. Hycin coctrc tr t / t rs .

fririale genital

orgatis. A, Lateral view. B, Section in

transverse plane

of

of

crab,

median

side

t o

t he

right.

eol, Coluiiinar epit,heliiini

;

r u t , rut

iclc :

Inus, muscle; ov, ovary

:

ovid, ~~v ir l i i c t sp,

sperniatheca,; str, stratitied rpit,helium;

VEI,

vagina;

vu,

vulva.

Kone

of

the specimens sectioned \%ere ear to ovulation, and therefore, as

i n C'arci) ius ,

the oviduct

was

not observed

as a

passage Iwtween thc ovary and the spermatheca The

oviduct is visible only in sections (Fig

7B ) .

ant1 its structure is most clearly shoni i by a

series of frontal sections Figs

8

and

9)

I t

is composed

of a coluninar epithclium uliich

forins

a

tube leading from the

basc

of tht. ovary, where its lumen is continuous n i th the

central cavity of the

ovary-,

to the a~all

f

the spermatheca. The epithelium is foltlerl,

and

is in some parts only

one

cell thick,

in other

parts several.

It joins tlic

spermathem just

dorsal to the junction of the stratified and chitinous regions

of

its wall, but its lunien does

not commuiiicate

ni th

the cavity

of tlic

hperrnatheca a t this

stage

of

the

owllatory

cycle.

The upper part of the wall of the qpcrmatheca (Fig.

7B)

is composcd of a stratified


12/22

290

R . G. HARTNOLL

epithelium 20

or

more cells in thickness. This region expands to accommodate the sperm

plug

on

copulation. The lower pa rt is lined by cuticle, a thick layer of procuticle with a

thin layer of epicuticle. The cuticle is folded, particularly a t the junction

of

the sperm-

stheca and vagina, and is underlain by columnar epithelium.

The vagina is U-shaped in section (Fig.

10A, B),

with th e open end of the

U

facing

laterally.

It

is composed of cuticle and epithelium similar to that forming the lower par t

of the spermatheca. The cuticle of the outer wall is thick and inflexible, that of the inner

wall (which is invaginated into the outer) is thinner and flexible. Normally the lumen of

the vagina is occluded as a result of this invagination. The muscles are restricted to the

lateral side of the vagina, and are attached t o the inner wall : from here they run ventro-

laterally and are attached a t their other end to the sternum (Fig.7B). Upon contraction

they pull the invaginated wall laterally and

so

open the lumen of the vagina, as they have

partially done in Fig.

10,

presumably due to the muscles contracting during fixation.

The vulva is a rounded opening (Fig. 1OC) covered by a hood-like projection of the

0

0 2

m

A

2 mm

Fig. 8. H y n s amneus

A,

Section of ovary and spermatheca in th e frontal plane of the crab.

B, Detail to show th e oviduct.

ep, Epithelium of ovary; lu, lumen of ovary ;ov, ovary ;ovid, oviduct; sp, spermatheca;

str, stratified epithelium.

sternum (Fig. 7B). The opening is normally closed by a flexible membrane which is con-

tinuous with the inner wall of the vagina. This membrane can be easily displaced, and

will in any case tend to be pulled aside by contractions of the vaginal muscles.

The two main differences between the ducts of

H ya s

and Carcinus are in the forms

of

the oviduct and vagina. I n both, the oviduct was observed

at

a phase of the omlatory

cycle when it

did

not form a passage from the ovary to the spermatheca'; in

Carcinus

it

was a plate of cells,in

H ya s

a blind-ending tube.

It

is not certain whether these are actual

differences,

or

merely phases observable at different periods of the ovulatory cycle. The

differences in the vagina are undoubtedly both permanent and radical. Compared with

Carcinus,the vagina of H y a s has one face invaginated into the other, and the musculature

restricted to the invaginated face. The muscular arrangement could be regarded as an

extreme development of the condition found in

Carcinus,

in which the muscles on the

lateral side of the vagina are inserted on the sternum some distance from the vulva.


13/22

Genital

ducts

i r i ,female

crabs 291

Concave pattern with operculurn

This is a modification of the concave type, from which it differs by possessing

a

calcified

operculum which closes the vulva. This operculum has been briefly described in earlier

papers (Hartnoll, 1964, 1965). In

some

species the operculum is freely mobile a t all times,

and thus will not offer any obstacle to copulation or ovulation. I n others the operculum

cannot normally be moved without breaking either it or the surrounding integunlent ;

0.5 nrn

b

I

Fig. 9.

H y n a arnne7cs. Sections of the ovidurt

111

the frontal plane, from

A

to

C

progressively

more ventral than

Flg.

8.

lu,

Lumen of

o v a q

;ov, ovary; ovid,

ot iduct

;

str,

stratified epithelium.

with opercula

of

this t-ype, copulation and ovulation are restricted to certain periods (as

described below) when the opercula become temporarily mobile. An example of each

type, in both cases a grapsid, is described below.

A Jamaican species,

Cydograpsuo integer,

is the example of the first type . Figure 11 is

a section of the vagina and vulva in the transverse plane of the crab ; the thick cuticle of

the operculum and

the

sternal border of the vulva contrasts with the thin cuticle of the

hinge. I n the vagina both the inner and outer walls are thin and flexible, a contrast to the

condition in H y a s . The muscles are attached to the inner wall

of

the vagina and the

operculum. Figure 11A is the condition when these muscles are relaxed; on contraction


14/22

292 R. G . HARTNOLL

they will tend to dilate tlie vagina and open the operculum, with the result shown in

Fig. 11B.

The example of a species in which the operculum is normally immobile is the common

European grapsid,

Pachygrapsus

rnarmoratus. Figure 12A is a section in the transverse

plane of the crab. The reasons for the immobility of the operculum were investigated.

One possibility was that either the hinge or the inner wall of the vagina was inflexible,

but

from Fig. 12A it is evident that both regions possess a thin cuticle, and dissection

showed th at they were quite flexible. This dissection revealed th at the cause was the

Fig. 10.

A,

Section through upper part

of

tlie vagina

of Hyus coarctatus. B,

Section through

lower pa rt of the vagina of H y n s conrctntus . C, Ventra l view of sternum of H y a s urrtne7~s.

col,

Columnar

epithelium; cut, cuticle; mus, inusrle; vu, vulva.

relationship of th e operculuni to the rigid base

of

the outer wall

of

the vagina; Fig. 12B,

C

contrast these structures in Cyclograpsus integer and Pachygrapsus marmoratus respec-

tively. In the former, movement of the operculum is not restricted by the vagina but , in

the latter. movement is not possible unless the outer wall is either broken or rendered

flexible. Decalcification of the vulvar region with dilute hydrochloric acid produced

the required flexibility, and the operculum then became mobile. As in Cyclograpsus the

muscles are attached to the operculum and the inner wall of th e vagina, bu t as the muscles

run postero-laterally from the vagina to the sternum, only short portions are present in a

transverse section (Fig. 12A).

As

already stated above,

in

species such as Puchygrapsus marmoratus both copulation

and ovulation are limited to those periods when the opercula become mobile. One such

time is immediately following ecdysis, before the new integument has hardened, and in

some earlier papers (Hartnoll, 1964, 1965)I assumed that this was the only such time.


15/22

Genital

duc ts

i ~ iemale

crabs

293

Doubts about th is view uere caused by records

of

the ovulation of Y iarmoratus which

indicated tha t many specimens had laid in the middle of the interinoult period (l'ernet-

Cornubert, 1958), proving that the opercula must have become mobile a t

a

time other

than ecdysis. An effort to investigate this mas made a t the Stazione Zoologica, Naples,

but none of my captive females

of

P.

mccrmoratus

either ovulated or developed rnohile

opercula. Bu t interesting results were obtained from two females

of

Dorippe

Zaiiuta

L.,

another species with iminobile opercula. The first specimen died while bearing eggs which

were just about

to

hatch. It had ripc ovaries

i n

whicli the ova were ready

t o

be laid. and

Fig. 11 .

Cyclogrcipsus

I , t t e y w : sections

of

v i i lw and vagina, in the transverse plane.

A,

Oper-

culum shut .

B,

Operculuin open.

col, Columnar epitheliuin; epi, epicuticle; hi, hinge; mus, muscle

;

op, operculurn; pro,

procuticle;

va,

vagina.

although the crab was not in proecdysis the vnlvae had undergone a local decalcification.

The sternum an d outer mall of the vagina were unaffected, but t he operculum, hinge and

inner wall of the vagina were decalcifit~l,wit,h the effect of rendering the operculum

mobile. The second specimen hatched one batch of eggs, and relaid within 12 hours.

Shortly after laying t he operculum was still mobile, b ut after 36 hours it had become

immobile (at

a

water temperature of

24

to 2 5 ° C ) . Thus in Dorippe ovulation is possible

in mid-intermoult because the

vulvar

region

is

locally decalcified shortly before laying,

and recalcified again soon afterwards. Some similar observations have also been made in

the case of

Gorystes cassivelaun us,

which has ducts of the simple pattern with heavily

calcified immobile opercula. I n the breeding season, which occurs in May arid Jun e at

Port Er in, the opercula become decalcified and flexible for a period

of

from 12 to 20 days;

19


16/22

294 R . G. HARTNOLL

during this time copulation and ovulation occur. Neither process occurs in females

which have just moulted-the other period when the opercula are flexible. Presumably

a similar temporary decalcification takes place in

Pachygrapsus marmoraatw,

and perhaps

generally in all species with immobile opercula. It has been mentioned above that ovula-

tion occurs during the intermoult in

P . mar tora tus ,

and there are also records that copula-

tion takes place in hard females (Vernet-Cornubert,

1958),

presumably during the same

periods

of

decalcification.

Fig. 12.

A, PUChygTUpSUS m r m o r u t u s ,

section of vulva and vagina in the transverse plane.

B, Cyclogrupsus integer,

section

of

operculum and base of vagina in the frontal plane. C

Puchygrupsus marrnomtus,

section of operculum and base

of

vagina in the frontal plane.

col, Columnar epithelium; epi, epicuticle; hi, hinge; Inus, muscle; op, operculum; out, outer

wall

of

vagina;

pro,

procuticle.

STRUCTURE

AND TAXONOMY

A number of species were examined to discover whether t he various patterns of genital

duct were distributed on a taxonomic basis. The results are given in turn for each of the

superfamilies in

Monod’s

classification.

Superfa mily Oxystomata

Family Leucosiidae. Ebalia tuberosa

Pennant and Ilia

nucleus

L. Both have ducts of

the concave pattern, with the outer wall of the vagina rigid and the inner wall flexible.


17/22

Genatul

ducts in

female

crabs 295

However there are differences

from

the structure clescribed for H y as : in

Ilia

the vaginal

muscles run posteriorly rather than laterally (Fig. 13C), while in Ebalia the vagina is

parallel with rather than perpendicular to the sternum (Fig.

13H) .

Family Dorippidae. Ethusu

mascarone

Herbst has ducts of the concave pattern, with

both walls of the vagina flexible, and the vaginal muscles running anteriorly (Fig. 13D).

Dorippe lanata has them of the concave pattern with immobile opercula, with the outer

wall of the vagina rigid, the inner wall flexible, and the muscles running medially.

Family Calappidae. Calappa granulata

L.

was the only species examined, and it has

ducts of the simple pat tern. However, the vaginal muscles are concentrated towards the

lateral wall and a large bundle of them is attached to the soft basal portion of this wall

which normally occludes the opening of the vulva.

Ventral view

Posterior view

Fig.

13. The

orientation of

the

vaginaand

i ts musculature. A,

H y a s

aruneus;B, Pnchygrupszts

nuzwnoratus:

C Ilia riucleus; D, Ethusn

~rruscrrro?~e;

, Dm’ppe lanatffi; , lffiguszadepressrt;

G, Hyas

a r u i i e u s ;H, Ebolin

tuberosa

fluperfamily Corystoidea

Five species were examined, each from a different family. In four

of

these-Ate1ecyclu.s

rotundatus (Olivi), Cancer pagurus, Thia residua (Herbst) and Pirimela denticukta

(Montagu)-the ducts are of the simple pat tern. In the fifth, Corystes cassivelaunus

Penn., the vagina is similarly of the simple patt ern with the muscles distributed around

i t ; but the vulva is closed by an immovable operculum, to which a large bundle of the

vaginal muscles is attached.

Superfamily Brachyrhyncha

Some authorities divide this superfanlily into two series of families. Of those considered

here the Portunidae, Xanthidae and Potamonidae are usually placed in the series Cyclo-

metopa, the others in the Catometopa.


18/22

296 R. . HARTNOLL

Family Portunidae.

It

is mentioned above that the female genital ducts of several

portunids have previously been described, all being of the simple pattern-Callinectes

sapidus, Carcinus maenas and Portunw sanguinolentus. Two other species were found to

be similar-Porturnnus latipes Pennant and Macropipus arcuatus (Leach).

Family Xanthidae. Pilumnus

hirtellus

(L.)

and Xantho

Jloridus

Mont. both have ducts

of the concave pattern , with the inner and outer walls of th e vagina stiff bu t flexible.

Family Potamonidae.

A

number of species of the African genus Potarnonautes were

examined, and the ducts appear to be derived from the simple pattern. A large vulva

opens into a wide vestibule with flexible walls, from the roof of which a narrow vagina

runs dorsally to the spermat,heca. The vagina is lined with thick cuticle which is flexible

bu t not elastic, an d on reaching the spermatheca this expands into a rosette-like structure.

The vagina is very narrow

:

n an unidentified species producing eggs of 1.6 mm diameter

t'he external diameter of' the cuticular lining of the vagina was 0-1 mm in non-ovigerous

females. However in ovigerous specimens t'he vaginal lining was wider and thinner, so

evidently changes occur in the vagina during the ovulatory cycle.

Family Goneplacidae. Goneplax rhomboides

(L.)

has ducts intermediate in pattern

between the simple and the concave. The vagina is C-shaped in section, bu t both inner

and outer walls are quite flexible, and there is no prominent localization of the vaginal

muscles.

Family Pinnotheridae. Pinnotheres pisum

(L.)

has ducts of the concave patte rn; the

vaginais almost parallel with the sternum in a manner similar to that of Ebalia (Fig.

13H).

Family Palicidae. Palicus ohesus A . Milne-Edw.) has ducts of the concave pattern.

Although otherwise quite normal, a t first sight the position of the vulvae appears excep-

tional. Thus Borradaile

(1908)

states ha t in the Palicidae there are 'female openings on the

sternal segment corresponding to th e first pair of walking legs'. Similarly Rathbun (1918)

states with regard to Cymopolia =Palicus) tha t 'I n the female the genital openings are

on

the second segment of the sternum close to the suture between it and the first

'. A

mature

female of Palicus obesus was obtained, and on a superficial examination the vulvae did

appear to open on the fifth thoracic sternite just posterior t o the suture with the fourth.

However, this impression is due to the poor development of the sternal sutures in Palicus;

this is clear from Fig.

14

which contrasts the condition in mature females of Carcinus,

Hyas and Palicus. In Carcinus each of the third to eighth sternites is clearly demarcated.

In Hyas the sutures between the fourth to the eighth sternites no longer reach the midline,

bu t the vulvae lie in the par t which is divided and clearly open on the sixth segment.

In Palicus the sutures are still less developed and the vulvae lie in the undivided median

portion of the sternum; the fact that they lie anteriorly in this portion is not condusive

evidence th at they are

in

the fifth sternite. The nervous system was dissected to provide

further evidence,

A

pair of large nerves runs from the thoracic nerve mass to the appen-

dages of each segment, and in Carcinus the nerves of the sixth segment (supplying the

second walking legs)

run

anteriorly to t,lie vagina. In Palicus the nerves to the sixth

thoracic appendages likewise run anteriorly to the vaginae (Fig. 14C),and so the vulvae

must be regarded as belonging not to the fifth segment, but to the sixth as in other

Brachyura. The confusion has arisen as a result of the incomplete segmentation of the

sternum in Palicus.

Family Ocypodidae.

Uca

pugnax yapax (Smith) has ducts of the concave pat tern with

immobile opercula, with the vaginal muscles running laterally. Ocypode albicans Bosc is

similar, but with a slightly atypical structure. The outer wall of the vagina is thin and

flexible, the inner wall thick, rigid, and not clearly demarcated from the operculum with

which it is continuous.

Family G'rapsidae. Eighteen species were examined. Two of these, Brachynotus

sexdentatus

Risso

and Percnon

gibbesi

(Milne-Edw.),have duc ts of the concave type, the

others of the same type but with opercula. Four of these have mobile opercula-cyclo-

grapsus integer, Metopaulias depressus Rathbun, Pachygrapsus transversus (Gibbes) an d


19/22

Genital

ducts i n

emale

crabs

Plagusia

depressa (Pabricius)

;

in P. trat~sversus he operculum is

calcification which lies in the flexible membrane occluding the vulva

which have immobile opercula are listed

:

d r a t u s

pisoi~ii(Jiilne-Edw.)

Geograpsics lividus

(Milne-Edw.) ;

297

reduced t o a small

The 12 other species

Goniopsis cruentata

.

(Latreille)

;

Grapsus grapsus (L.) P a c h y q t u p ~ u ~raci1i.s

(Saussnre)

;

P.

~ n a r m o r a t u s ;

Planes m i n u t u s (L

)

; Sesnrnza

angustipes Dana

;

8 b iden ta tum Bencdict ;

S urucaoense

de Man;

S .

ricordi Milne-Eclw. S. eerleyi Rathbun.

Fami ly

Gecarciwicloe. A West Indian l a i r t l crab. Gecarciii1i.s ruricoln L.),has ducts of

the concave pattern

it11

immobile

operciila

n 6

10 m m

I

I

Fig.

14.

Veritr;rl

vit:w

of

the

sternum. A,

C r r r c i ~ u s

m en a s ;

B, Hyus

~ i r u ~ ~ e w ;

, f r r l i c u a

obesus, wit.11the posit ion

of

the

t,horacic

irrrve itlass and the fourth to eightll segmental nerves

shown.

6, Nerve to appendage of the

sixtli

tlroriicie segment;

ts

6,

sixth

thoracic \ ternitr ; vu ,

vulva.

Superfamily

xyrhyuchu

Fa mi ly Hymenosoniat idae .

Halicarcin

us plunat us (Fabricius) has a very

sliort

vagina

of

the concave type ; the vaginal muscles are localized against,

and

extend postero-laterally

from, the inner wall of th e vagina.

Fa mi ly Par thenopidae.

Lainbrus

anguli frons

Latr.

has

ducts of a slightly unusual con-

cave pat tern. The vulva is a large round opening closed by a flexible membrane in the

centre of which is a C-shaped aper ture . This is the opening

of

the vagina,

a

sliort tube

C-shaped in section, with the walls quite flexible. The vaginal muscles are reduced, but

are localized along the inner wall of the va,'wia .


20/22

298

R.

G.

HARTNOLL

Fam ily Majidae. Inach us dorsettensis (Pennant),Ma j a squinado (Herbst) and Micro-

phry s bicornutus (Latreille) were examined in addition to the two species of H y m already

described. All have ducts of the concave pattern.

DISCUSSION

The functional significance of the structure of the genital duct will not be considered

here; i t will be discussed in a later paper dealing with the related phenomena of courtship,

copulation and ovulation. A subject that can usefully be examined here, however,

is

whether the various differences in the form of the genital duct are of any phylogenetic

importance in the Brachyura. These differences are basically three in number: whether

the vagina is of the simple or concave type, whether an operculum is present and, if so,

whether the operculum is normally mobile or immobile. The last two of these can be

readily shown to be of little phylogenetic value. Thus the mobile type

of

operculum is

movable throughout the intermoult, the immobile type for only a short period; this is

a

minor difference

only,

and both types can be found within the same genus,

for

example

Pachygrapsus.

Similarly with the presence of absence of a n operculum. Opercula have

evolved independently a t least three times

in

the Brachyura, once from the simple type

in Corystes, and twice from the concave type

in

Dorippe, and in the group comprising the

Grapsidae, Ocypodidae and Gecarcinidae. There are closely related pairs of genera such

as

Dorippe

and

Ethusa, Plagusia

and

Percnon,

in which only one of the genera possesses

opercula. There remains for consideration the contrast between the simple and concave

types

of

vagina, a rather more fundamental difference, though one which could quite

conceivably have had a polphyletic origin. The available data show that the two types of

vagina are not found within the same family. The occurrence of the two types

is

listed in

Table

1,

but i t must be emphasized tha t only a very few species have been examined in

some families, and hence the table may well need future amendment.

Table 1 .

The occurrence of simple and concave patterns of genital

duct

in the familie s of

Brachyura

OXYSTOMATA CORYSTOIDEA BRACHYRH YNCH-4 OXYRHYNCH A

SIMPLE

Calappidae Atelecyclidae Potamonidae

Cancridae Portunidae

Corystidaa

Pirimelidse

Thiidae

Goneplacidae?

CONCAVE Dorippidae

Leucosiidae

Gecarcinidae Hymenosomatidae

Grapsidae Majidae

Ocypodidae Parthenopidae

Palicidae

Pinnotheridae

Xanthidae

Table 1 shows that of the four superfamilies considered here, only the Oxyrhyncha and

Corystoidea exhibit uniformity in the basic structure of the vagina. I n the case

of

the

Oxyrhyncha there is general agreement tha t the Majidae and Parthenopidae are closely

related, but there have been doubts expressed as to the inclusion of the Hymenosomatidae

(Gurney,

1942).

The form of their vaginae indicates that they could well belong in the

Oxyrhyncha, but th at

on

the basis of this character they could equally well have affinities

with the Leucosiidae

or

Pinnotheridae as Gurney

(1942)

suggests.

As

for the Corystoidea,

there is some disagreement as to whether they are a related assemblage and should


21/22

Genital duct8

female

crabs

299

constitute a separate superfamily, although Bouvier (1942)presents a detailed case to this

end. The structure of the genital ducts supports the homogeneity of the Corystoidea,

and also supports certain of Bouvier's pliylogenetic conclusions which are discussed

below.

In

the case of t,he Oxystomata the two types of vagina are found, but too few species

have

becn

examined to permit any generalizations. Thus it does not help to resolve the

various doubts regarding the affinit,iesand the homogeneity of this superfamily.

If the Corystoidea are considered a separate superfamily, the remaining families of the

Brachyrhyncha are generally divided into two groups. The Cyclornetopa contains the

Portunidae, Potamonidae and Xanthidae, while the Goneplacidae, Pinnotheridae,

Palicidae, Grapsidae, Ocypodidae and Gecarcinidae are placed in the Catometopa. The

Goneplacidae are often regarded

as

being transitional between the two groups. The

structure of the vagina does not support, this division of the Brachyrhyncha. The Por-

tunidae, and possibly also the specialized Potanionidae, have affinities with the Cory-

stoidea by t'he common possession of ducts of the simple pat'tern. The Xant,hidae, with

concave ducts, have affinities with the Catometopa rather than with the Portunidae.

There is not sufficient. evidence to comment on the Goneplacidae.

It

remains to consider the evolutionary relationship of the simple and concave types of

duct, and the phylogenetic implications of any conclusion. There are

no

living inter-

mediates between Brachyura in which the female genital ducts open coxally, and those

in which they open sternally. Weit,her does the position or structure of the ducts seem to

be discernible in fossil crabs. Thus it seems unlikely th at any data will become available

on the evolution of the sternally opening genital ducts, thereby providing evidence as to

whether the simple or concave type is the primitive form. I n the absence

of

such evidence,

however, it would nevertheless seem more probable that the simple type is primitive,

and tha t the concave type evolved from it, on one

or

several occasions. If t,his is the case,

then the distribution of the simple and concave types supports Bouvier (1942)in his view

of the affinities of the Corystoidea. He regards the Corystoidea as

a

natural group, as the

most primitive of the Brachyura with sternal female genital openings, and as the basic

stock

of

that group. All of these postulates are supported by the fact tha t all members of

the Corystoidea examined have ducts of t,hesimple type. Also he is of the opinion that the

Corystoidea have close links with the Brachyrhyncha, especially with the Portunidae

;

this is supported by both having ducts of the simple type. Thus this study supports

Bouvier's concept tha t the Corystoidea-Portunidae group is the basic stock of the higher

Brachyura, but like Bouvier it contributes little on the relationships of the other families

to this basic stock.

It

would be presumptuous to change the existing classification of the Brachyura on the

evidence of this study of only one series of organs-the female genital ducts. However,

it

does appear from this work tha t the present classificationsof the Brachyura above the

family level are unsatisfactory in some respects, and tha t a reappraisal based on a wider

morphological study has become necessary.

ACKNOWLEDQEMENTS

I

am grateful to the many people who either helped me to collect material or sent me

specimens, and

to Dr L.

T. Threadgold

of

Queens University, Belfast, who carried out

the electron microscopy. Dr E. P.Ryan of East Carolina College, U.S.A., and Dr A. E.

F.

Heydorn of the South African Association for Marine Biological Research, Durban,

generously allowed me to see unpublished manuscripts.

I wish to thank Dr

D.

I.

Williamson of the Marine Biological Station, Port Erin, for reading the manuscript, and

for his valuable comments and suggestions.


22/22

300

R. G. HARTNOLL

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morphology of the genital ducts in female crabs.pdf

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