The nauplius stages of the cirripede Tetraclita squamosa rufotincta Pilsbry

149

J. c.\-/,.four. Biol. Ecol., 1981, Vol. 54, pp. 149-165 Elsevier/North-Holland Biomedical Press

THE NAUPLIUS STAGES OF THE CIRRIPEDE

TETRACLITA

SQUAMOSA

RUFOTINCTA

Pilsbry

MARGARET BARNES The Dunstaffnage Marine Research Laboratory,

Oban, Argyli, Scotland

and

Abstract: The nauplius stages of the cirripede Tetrwlitu syuomoso rr&tincta Pilsbry from Elat have been cultured and described. There are the usual six larval stages followed by the cypris but the increase in size during development is small compared with many other species. This small increase compares favourably with other species having very large embryos containing an excess of yolk and which do not take external food during larval development. The setation of the larval appendages is less than in other species and on the antenna and mandible does not increase after stage 111. It is suggested that the lack of setation, coupled with a reduced development of the labrum, may be a consequence of the lack of a necessity for this species to feed externally during its planktonic life.

Descriptions of the nauplius stages of cirripedes have become increasingly available in recent years; nevertheless many more remain to be described. Apart from the value to an understanding of the morphology and systematics of the Cirripedia, recognition of the free-living nauplius stages is essential for studies of the planktonic ecology of any species. According to Newman & Ross (1976), ~e~~~l~ii~ff ~q~~~z~~~ rlff~?~n~tu belongs to the subfamily Tetraclitinae of the family Tetraclitidae. The main areas of distribution are the Red Sea, East Africa, the Arabian and west coasts of India, and also islands in the west Indian Ocean (Pilsbry, 1916; Nilsson-Cantell, 1921, 1928; Kolosvary, 1941, 1943). The species is common on rocky substrata in the narrow littoral zone of the shore at Elat on the Gulf of Elat, Israel (Safriel & Lipkin, 1964; Achituv, 1972). As with other Te~ru~ii~ff species (Barnes, 1959) the adult favours situations subjected to wave action. T.s. rtlfbtinctrr Pilsbry is regarded as a tropical species and it is, therefore, somewhat surprising to find a distinct seasonal breeding cycle. A few animals (OS;,;, of the population) may be found with egg lamellae at any time of the year but the main breeding season begins in October, reaches a maximum in NovemberDecember and then declines (Achituv & Barnes, 1978a).

OO22-0981/81;0000-0000~$02.50

0 Elsevier:North-Holland

Biomedical

Press

150

MARGARETBARNESANDY.ACHlTUV MATERIAL AND METHODS

Clumps

of T.s. rujbtincta were collected

from the shore at Elat near the H. Steinitz

Marine Biological Laboratory at a time when ripe, eyed embryos were present in the egg lamellae. In the laboratory ripe egg lamellae were removed from the mantle cavity of the adult and put into beakers sea water which had passed

through

containing

a Millipore

locally

collected

filter (0.45 pm).

Mediterranean Hatching

of the

ripe embryos to the free-swimming stage I nauplius larvae was rapid, depending on the ripeness of the egg lamellae. Some nauplii were quickly removed and preserved at once in 70% alcohol. Other samples of the stage I nauplii were pipetted into 400-ml beakers containing filtered sea water. These cultures were maintained in ambient light and at a room temperature of ~22 “C. Some were fed with a suspension of Dunaliellu tertiolecta Butch., while others were allowed to develop without food. The sea water was changed daily; the nauplii were concentrated in a beam of light, pipetted into a small net (300 pm mesh), and washed with sea water before being transferred to fresh sea water in a clean 400-ml beaker. The food was renewed in those cultures being fed. Several replicates (at least three) were raised and there was no agitation of the cultures. Samples of nauplii were removed from the cultures at intervals and immediately preserved; the first (after 6 h) proved to be mainly stage II nauplii. The change from stage I to II was rapid, again depending on the ripeness of the embryos. Further samples were taken and preserved at daily intervals until it was found that the majority were stage VI. Some of these did develop further to the cypris stage. The dimensions of the various stages of nauplii were measured under a binocular microscope using a scaled ocular. The total length was measured from the frontal margin to the tip of the caudal spine. The carapace length was measured from the frontal margin to the posterior border of the carapace, and the width was taken as the greatest width of the body behind the frontolateral horns. The length of the horns and of the carapace

spines was also measured.

For examination of the morphological details the nauplii were sometimes, although not always, cleared in lactic acid (Humes & Gooding, 1964) and then dissected

under

a binocular

polyvinyl lactophenol. squares and detailed microscope.

microscope

and

stained

lightly

with lignin

pink

in

Drawings were made to scale using an eyepiece ruled in examination was then made under a Reichart binocular

RESULTS The time of development from stage I to stage VI nauplius was 68 days depending on the ripeness of the original embryos and this was the same for the starved as well as the fed cultures. It is well known that stage I nauplius larvae of cirripedes do not feed but in the present instance there was no evidence of feeding

NAUPLIUS

STAGES

in any stage. No green colour nauplii.

No difference

OF TETRACLITA

SQUAMOSA

from the food was ever seen within

was found

between

the nauplii

151

RUFOTINCTd4

from starved

the body of the and fed cultures

and so all results were pooled. GENERAL

FEATURES

OF THE NAUPLII

It was possible to distinguish six nauplius stages and the various dimensions, based on several individuals in each case are given in Table I. The nauplii are bulky TNILE I

Tetrrrclirn squamostr rufbrinrtu:sizes of the six nauplius stages and sample in parentheses. Total Stdge

the cyprid

(pm)

and

Width

horns

Spines

Length

..__ I II III IV V VI Cyprid

508.8 548.0 634.7 679.5 748.5 771.2

+ 13.9 + 7.0 rf: 16.5 + 5.1 i: 18.2 + 6.4

(IO) (4) (9) (15) (9) (5)

336.0 358.4 364.8 371.2 397.3 419.2

+ 10.1 + 7.8 k 12.0 * 19.6 zk 4.5 + 6.4

(10) (5) (5) (44) (36) (5)

457.8 497.8 534.4 589.8

+ k k +

31.0 16.0 16.3 16.3

(44) (36) (5) (7)

75.7 + 3.7 (7) 101.3 k 8.2 (9) 115.2 k 6.4 (5)

_

73.8 94.1 95.7 98.9 98.9 103.2

k 3.4 (7) * 5.3 (14) + 5.2 (9) + 11.5 (8) + 3.2 (6) k 3.X (6)

and the carapace is notably convex particularly in the earlier stages (see Fig. 2). This makes it difficult to keep the nauplii lying evenly on their dorsal surface during measurements. Outlines of the six stages lying on their dorsal side are shown in Fig. 1 and in lateral view in Fig. 2. In stage I the body is more or less ovoid and, as in many newly liberated balanid stage I nauplii, the frontolateral horns are directed posteriorly and appressed to the sides of the body. The caudal

spine and abdominal

process

are very short and of

equal length; no frontal filaments were seen. In this, as in all stages, a median eye is present. In stage II the general outline is still ovoid but the frontolateral horns are less appressed to the body. The abdominal process is still almost equal in length to the caudal

spine and the former

caudal spine in stages 1 and Frontal filaments are present In stage III and later stages to the long axis of the body.

in

Frontolateral

Carapace

length

number

&SD;

now bears a pair of tiny spines

(Fig.

3). The

II is directed more dorsally than in the later stages. in stage II and all subsequent stages. the frontolateral horns project almost at right angles The general shape in stage III is still ovoid although

the frontal margin is a little less rounded. The caudal spine is now longer and the pair of tiny spines on the abdominal process are more obvious. The abdominal process arises in a mid-ventral position and projects ventrally and posteriorly. It is separated from the caudal spine by a notch. The process itself forms at its posterior extremity a well-defined furca the diverging rami of which are slender and straight.

152

MARGARET

BARNES

AND Y. ACHITUV

The posterior border of the carapace is first clearly delimited in stage IV and as a result the nauplius becomes less rounded, The carapace bears a pair of fairly

Fig.

1.

Tetruc/ifu

squamo.w

side showing

ru~~tjncf~: outline drawings of the six nauplius stages lying on their dorsal the shape and more important spinous processes: scale bar = 200 pm.

short carapace spines. The abdominal process bears a further pair of small spines anterior to the first pair that appeared in stage II (Fig. 3). The abdominal process becomes considerably enlarged in stages V and VI. In stage V there is a third pair of spines on the abdominal process and in stage VI the cirriform appendages can be clearly seen underneath the exoskeleton (Figs. 2 and 3). In some stage V’s it is also possible to see where these cirriform appendages will appear. In addition to

NAUPLIUS

the median

eye found

stage VI ; the intensity

STAGES

OF TETRACLITA

in all earlier

stages

of the pigmentation

convex shape of the nauplii

SQUAMOSA

paired

lateral

of these lateral

makes a comparison

153

RUFOTINCTA

eyes are also present

in

eyes may vary. The very

of the lengths of abdominal

process

Q IV

Fig. 7. Tetrtrditcr squrrmoscr rufo/inc~/t/: lateral

and caudal

spine difficult

than the former.

The labrum

view of the six nauplius

to assess but it appears (Fig. 4) shows practically

stages;

that the latter

scale bar = 200 pm

is slightly

longer

no change from stage I to VI.

The cyprid (Fig. 4) is brownish in colour, has the characteristic anteriorly, and has no distinctive features.

shape being rounded

MARGARET

154

BARNES AND Y. ACHITUV

I

I

Fig. 3. Tetraclitu squumosu rujidncta: outline drawings of anterior part of the six nauplius stages showing the abdominal process and caudal spine; in stages IV to VI the anterior margin of the carapace and the carapace spines are shown: scale bar = 100 pm.

“’ Fig. 4. Tetruclita

squumosa

r@tincta:

scale bar for cyprid

v

left, outline drawing of cyprid; right, labrum of stages = 200 pm; scale bar for labrum = 100 pm.

I and VI:

NAUPLIUS

STAGES

OF TETRACLITA

SQL’AMOSA

155

RUFOTINCTA

APPENDAGES

Paired

antennules,

antennae,

and mandibles

are present

Figs. ,5, 6 and 7 show the setation

of these appendages

formulae,

of Bassindale

adopting

the notation

in all stages

I to VI.

and their form. The setation

(1936), are given in Table

II. An

TAHLF II

Tr~~tditu squtrnzosc~ mj!fbrincru: setation Stage

Antennule

I II III IV V VI

04211 042 I I 0421 1 1421 1 1142111 11142121

formulae

of the six nauphus

stages (after Eksindale,

Antenna

1936)

Mandible 013-032226 014-032326 014-032336 014-03233G 014 03233G 014-03233G

014 03222G 014-032226 0255032226 0255032226 025 032226 025 -032226

TABLE III ~c~rrtrc~lirtr .sy~rrmostr rufofincttr: setation formulae of the six nauplius stages (after Newman. S, simple seta; P, plumose seta ; sizes of seta decrease in order SSss and PP. respectively. Antenna Stage

Antennule

I

pPPPPs s SPPSPS p SSPSPS p .% SSPS Ps s ss SPPS Psss .css SSPS Pspss

II III IV V VI

s s s s s s

Exopodite

Endopodite

s s SP pP PP PP

PPP PP PP PPSPS Ps PPSPS ss PPS Ps ss PPSPS ps PPS Ps ps

SPPP PPPS PPPPS PPPPS PPPPP PPPPP

1965):

Mandible Exopodite s P P P P P

PSP PPPS PPPS PPPS PPPS PPPS

Endopodite PPP PPS PPS PPS PPS PPS

Pp Ps Ps Ps Ps Ps

p,, Pss Pss Pss Ps.s P.r.c

P/J pp p.w p.rs p.rs ,lSS

attempt was also made (Table III) to comply with the method of quoting the setation fsuggested by Newman (1965). It is, however, felt that this has drawbacks because lthe method of indicating the size of the seta by the large and small capital letters and either in italics or not can only apply to a particular appendage. What is a long seta on an appendage in an early larval stage may be a short seta in a later stage. In addition, when the method is extended as in Sandison (1967) it becomes loo confusing for quick comparison between species. Although the general pattern of setation follows that found in nauplii of other cirripedes there are some striking differences which cannot be doubted as they are consistent in all the material examined. In the antennule of T.s. mfbtincm a preaxial seta does not appear until stage IV with a further one being added in both stage V and stage VI. It is more usual in other species for the first preaxial seta to appear

156

MARGARET

BARNES

ANDY.

ACHITUV

in stage III with further additions in stages IV and V. Postaxial setae remain as four until stage V when one more is added and another in stage VI. In stage VI the penultimate segment of the antennule is swollen as is usual in many species. There are also signs of this swelling in stage V; it will become the position of the cyprid sucker. The setation of the antenna is remarkably constant throughout nauplius development. The only change is the addition of one terminal seta on the exopodite first seen in stage III. The setation of the mandible is almost as constant. There is the

Fig. 5. Tetraclitu squamom rz&~rincta: outline drawings of the antennules scale bar = 100 pm.

of the six nauplius

stages;

NAL’PLIUS

addition stage

STAGES

of one segment

there

endopodite.

is also

an

OF TETRACLITA

157

RC’FOTIMCTA

with its seta to the exopodite

first seen in stage II. In this

increase

penultimate

of one

In stage III and subsequent

in the third group

SQUAMOSA

on the endopodite.

seta

in the

group

stages there are three instead The presence

or absence

on

the

of two setae

of setules

on the

setae of the appendages did not appear to show any regular pattern and the presence of a plumose structure in one stage did not mean that after the moult to the next stage this particular seta would again be plumose. Several examples of this can be seen in Table III.

MARGARET BARNES ANDY. ACHITUV

Fig. 7. ~~r~~~~j~~~~~~~~~s~~ r~~~rj~~ra: outline drawings of the mandibles of the six nauplius stages: scale bar = 100 pm.

DISCUSSION It is well known that it is difficult to distinguish different species of cirripede nauplii by their setation formulae alone. Such formulae are very similar and may show slight variability even within species. Even so they are useful in separating the nauplius stages within a single species and it is possible to do this for T.s. rqfotincta from Elat (see Table II). The nauplius larvae of T. serrufa from South Africa and T. ~urpu~ffscens from New Zealand have been described by Griffths (1979) and Barker (197~3, respectively. Sandison (19.54) also gives the setation of stages I and II of South African T. serrata. The setation of the antennule, but not of the antenna and mandible, of the six nauplius stages of Tetraclitella karandei from India has been given by Karande (1974). For ease of comparison this information is tabulated in Table IV together with that obtained in the present work for Tetr~c~~t~squ~~os~ rz~f~t~ncta. In the antennule there is agreement in all cases except stages III, TV and V in T.s. rvfotincta. Here there is one less preaxial seta in each stage than in the other species.

II III IV V VI

I

Antennule I 11 III IV V VI Antenna I II III IV V VI Mandible

II

013 032226 014p03232G 014 032336 014-032336 014-032336 014-032336

I

work)

014~032226 014 032226 025-032226 025SO3222G 025-032226 025-03222G

0421 042 04211 14211 1142111 11142121

(present

rufotinctu

Tetrarlita squamosu

of the setation

0421 04211 14211 114211 11142111 11142121

(Karande,

1

1974)

Tetruclitelln karandei

Comparison

IV

014-032226 025-032226

04211 04211

Tetraclitn species.

1954)

013 03222G 014-032326 014 032326 014m 043326 015-044436 015~044436

1 1 1

1979)

014~032226 014~032226 025 032246 036-053246 038~05324G 038~05324ci

0421 0421 1421 114211 11142111 11142121

(Griffiths,

Tetruclitu .wwtu

of several

(Sandison,

formulae

TABLE

013 032226 014 03232G 014-033330 014 043436 015m04443G 015-044436

1 1 1

1976)

014m03222G 025 032236 025-032246 036-053246 037 053246 037 053246

0421 0421 1421 114211 11142111 11142121

(Barker,

T~~trcrclitu purpuruscens

160

MARGARET

Only in stage I is there agreement Griffiths’

(1979) results

T. serrata The setation

and

BARNES AND Y. ACHITUV

in all species on the setation

do agree with the present

T. purpurascerzs,

of the mandible

the number

agrees,

in those

work

of the antenna,

but

in stage II. Thereafter,

of setae

increase

species

for which

with there

each

in

stage.

is data,

in

stages I and II; in later stages the number of setae increases in T. serrata and T. purpurascens but in T.s. ryfotincta, as with the antenna, there is no change from stage III onwards. Nauplius stage I usually relies on residual yolk from the egg for nutriment but later stages are known to feed and in fact need to be fed if laboratory cultures are to be successful. In the wild the larvae hatch and begin their planktonic life at the time when food is available in the surrounding sea water. In the northern hemisphere, particularly, it is well known that the time of hatching is synchronized with the spring diatom outburst and that the success of the larval stages depends on this (Barnes, 1956, 1957). The antenna and mandible are involved in the feeding process (Lochhead, 1936) and it is by their movement and the setae on them that food particles are directed towards the labrum. It may be, therefore, that the reduced number of seta on the appendages of T.s. ryfktincta indicate a reduced need to feed. The eggs of the Elat population of this species are very large. By the time they contain the eyed embryo and are ready to hatch they have a volume of 32.7 x 10mhml per egg. Other Tetraclita species have much smaller eggs, e.g. T. squumox~, 6.07 x 10eh ml, T. rubescens, 3.28 x 10Whml, and T. serrata, 3.63 x lo-” ml (Achituv & Barnes, 1978a). The stage much larger than those of boreo-arctic species such as volumes of 8.74 x 10m6 and At the end of its embryonic

I nauplius of T. squamosa rgfbtinctu is, therefore, also other Terracfita species. It is also larger than those of B&anus balunoides and B. balanus which have eyed egg 8.45 x lo-’ ml, respectively (Achituv & Barnes. 1978a). development Tetraclitcr squamosa rujiltincta contains

far more nutrient material (1.92 kcal/unit vol.) than some other cirripede embryos, e.g. Balanus ha/anodes, 0.64 kcal/unit vol. (Achituv & Barnes, 1978b). This nutrient material is, therefore, available to the stage I nauplius and much will still be present in stage II and possibly

even carried

over to stage III. Achituv

& Barnes

(1978b)

suggested that this excess nutrient might serve to allow survival and further larval development in the nutrient-poor waters of the Gulf of Elat. The lack of any difference in size or time of development in the present work between fed and unfed cultures and the relatively small increase in size of the larvae from stages I to VI, coupled with a reduced development of the labrum, strongly suggest that Tetraclita squamosa rgfbtincta larvae do not feed and that the food reserves of the unusually large embryos are enough to sustain them throughout their larval life, This has been confirmed by Achituv (1981) who has determined the biochemical changes in these nauplii during development. The larvae of many cirripedes have now been described and using the data available it is possible to calculate the percentage increase in total length (frontal

NAUPLIUS

margin

to tip of caudal

to VI (Table the percentage

V). Apart increases

STAGES

OF TETRACLITA

spine) and/or from

T.s. ryfotincta,

in total

length

Pollicipes

range

from

161

RC’FOTINCTA

total width of the various

TABLE

The total length of stage stage I to VI in cirripedes

SQUAMOSA

larvae from stage I

spinosus,

and Iblu cumingi

108 to 308 and in total width

V

I nauplii and the percentage

increases in total length and width in development from for which data are available: numbers in heavy type are for those species showing percentage increases of -C 100; *, final width estimated.

stageI

Percentage increase

totallength (rm)

509 300 773 240 309 180 275 200 240 333 350

Total length 51

Width

15’)

Moyse. 1961

2X8

Sandison. 1954

129

Costlou & Bookhout.

Knrande. 1974

Karande. 1974

142 ?OY-244

\\ ork

Barker. 1976 (,rlt’firhs. lY7Y

I40 150

I’resxt

25 207 22’)

225 lb0

Reference!,

195X

Karande. 1974 I82 215

Basindale,

1936. Pyeiinch. 194X;

Crisp. I962a

370 382 2.32 2X0 2 I0 442 265 1x0- 195 200 266 279~180 266

l4Y- 1X8

100 144

213

246

225

Barnes & Co~tlow. 1961. Crisp. 196221 Molenock & Gomez, 1972 Pyefinch. 1948. 1949

I71

I21

Costlow & Bookhout.

254

301

Criq,

Barnes & Barnes. 1Y59a

308

267

206- 220

333- 283

II3

104

Karande, 1979 Barnes & Barnes, 1959b

300

322

20X-214

364 167

I I9

I40

Buchholr.

lY5l

Bassindale. 1936: Norris

307- 400

200

431

Barker. 1976

215

255

Barker. 1976

2X9

Bwindale,

Zlb

IOR

190

I58

205 220 250

134 13x

& Crkp.

195.3

1980

Sandison, 1954: Barker. 1976

197b

1936

Karande. 1974; Karande & Thomas, 1976 196-242

67

Knight-Jones & Waugh. 1949: Barker. 1976 Barker, I976 Karande. 1974

210

180

Crisp. 1Y54

Karandc. 1974: Kurande & Thoma\,

253

310

: Jones &

Wenxia & Xingqian.

220 240

300

lY57

IY62b

Sandison. 1954

710

16

300

172

204

Moysc. 1961

270

I56

20X

Ba\\mdale.

16*

Batham, I946 I’)36

from 100 to 431. T.s. ufotincta increases in total length by only 517: and in width by 25’>j,. Pollicipes spinosus and Ibla cumingi increase in total length by 16 and 67”,,, respectively; no data are available for increases in width.

TABLE VI

(pm)

509 350 382 190 250

462 710 300 270

Species

Tetraclita squamosa rufotincta Balanus balanoides B. balanus Chthamalus stellatus Elminius modestus

Ibla quadrivalvis Pollicipes spinosus Pyrgoma anglicum Verruca stroemia

Total length

312 565 165 120

336 220 213 90 125

(pm)

Width

Stage I

23.6 118.7 4.3 1.0

30.1 8.9 9.1 0.8 2.1

Volume (pm’ x IOh)

438 825 817 690

771 1150 1100 490 595

(pm)

Total length

338 655* 501 370

419 620 520 350 370

(pm)

Width

Stage VI

26.2 185.3 107.4 49.5

70.9 231.5 155.7 31.4 42.7

Volume (pm3 x IOh)

1.1 1.6 25.0 24.8

2.4 26.0 17.1 39.3 20.3

Ratio of volumes stage VI to stage I

575 850 695 530

590 940 810 410 550

pm

Cypris length,

Present work Bassindale, 1936 Crisp, 1962a Bassindale, 1936 Knight-Jones & Waugh, 1949 Anderson, 1965 Batham, 1946 Moyse, 196 1 Bassindale, 1936

Reference

Volumes of nauplius stages I and VI of a selection of cirripedes: relative increase in volume shown as the ratio of stage VI to stage 1 Volume; cypris length included for comparison with total length of stage I; heavy type indicates results for species known not to take and probably not taking external food during larval development; *, final width estimated.

NAUPLIUS STAGES OF TETRACLITA

SQUAMOSA

RC’FOTfNCTA

163

has a very large egg and consequently a very large stage 1 nauplius of total length 710 Frn (Batham, 1946) compared with 509 pm in Tetrf~~iitff sqz~a~~o~surz~i~tj~zcta. She also indicates that no intestine develops until the end of the nauplius stages and that the specialized larval development when compared with many other cirripedes appears to be connected with the amount of yolk in such a large egg. According to Batham the excess yolk allows larval development without taking external food and this obviates the need for a food canal in the larva. Dependence on yolk also probably prevents any great increase in size from stages I to VI (Batham, 1946). Anderson (1965) found a similar situation in Zblu qu~~r~~J~f~~~.s; the differentiated gut remained unchanged during larval development although the mouth and anus remained open in spite of no external food being taken. Anderson does not quote any dimensions for the larval stages but estimates can be made from his drawings. SimilarIy, some estimates have to be made to obtain complete data from Batham’s (1946) paper. Using these figures and assuming the volume of a nauplius is approximately that of a prolate spheroid the values given in Table VI can be calculated. Comparison with the few other species quoted shows clearly that once again Tetmclitu sqtramosa rgfutinctcl (ratio of final : initial volume = 2.4) has to be classed with the “non-feeding” ~~~~~c~~~s ~~p~~~)su.~ and Ibin qu~~riil~~~~~.s which have ratios of I .6 and I. I, respectively. All other species quoted have ratios of from 17.2 to 38.8. The reduced growth in the “non-feeding” species ensures that the cypris comes within the size range of all the other species (see Table VI), Unfortunately neither Batham (1946) nor Anderson (1965) give any setation formulae for the larvae of the species they considered and these cannot be deduced from their drawings. Anderson and Batham both indicate that rudiments of the cypris stage appear earlier in larval development in the species they studied than is usual in those species feeding externally. Tetraclita squamosa rujbtinctcr also shows these earlier signs of cypris development. In stage V the penultimate segment of the antennule is distinctly swollen (see Fig. 5) and in some cases the cirriform appendages can be seen underneath the exoskeleton of the abdominal process of stage V. Usually such signs of cyprid development are not visible until stage VI. In future work it is hoped to confirm that the larvae of T.s. rgfbtincta do not take external food and in the meantime it is postulated that this may be the reason for the lack of any increased setation on the antenna and mandible during larval development after stage III. Poiliciprs

spinosus

ACKNOWLEDGEMENT

The assistance of Dr. A. Kolorni in the collection of the adult animals is greatly appreciated.

164

MARGARET

BARNES

AND Y. ACHlTUV

REFERENCES

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SQIIAMOSA

RC’FOTINCTA

165

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