The development of artificially fertilised eggs of the rock oyster,

Saccostrea cucullata (von Born) was studied in the laboratory. The

morphological and behavioural characteristics of the developing larvae

were observed. A mixed diet of single celled algae consisting of Isochrysis

galbana and Tetraselmis gracilis was fed to the larvae. The larval

developmental stages observed include trochophore, D-veliger, late

veliger, umbone stage, pediveJiger and plantigrade

Mohan Joseph, M

Sukumar, P

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Larval Development of the Rock Oyster Saccostrea cucullata (von Born) P. SUKUMAR' M. MOHAN JOSEPH College of Fisheries, University of Agircultural Sciences, Mangalore - 575 002, Karnataka. ·Present address: Fisheries College, Tamil Nadu Agricultural University, Tuticorin - 628 008, Tamil Nadu. SUKUMAR, P .. and JOSEPH, M.M., 1988. Larval development of the rock oyster Saccostrea cucuJ/ata (von Born). In: M. Mohan Joseph (Ed.) The First Indian Fisheries Forum, Proceedings. Asian Fisheries Society, Indian Branch, Mangalore. pp. 255 _ 258. Abstract The development of artificially fertilised eggs of the rock oyster, Saccostrea cucullata (von Born) was studied in the laboratory. The morphological and behavioural characteristics of the developing larvae were observed. A mixed diet of single celled algae consisting of Isochrysis galbana and Tetraselmis gracilis was fed to the larvae. The larval developmental stages observed include trochophore, D-veliger, late veliger, umbone stage, pediveJiger and plantigrade. The time taken for the development of D-veliger, umbone stage, pediveliger and plantigrade stages were 22 hours, 12 days, 18 days and 20 days after fertilisation respectively and their corresponding average length x breadth were 67 x 54 J.Lm, 109 x lOS J.Lm, 143 x 160 jl''1 and 166 x 174 ~m. The length-breadth relationship of veliger larvae was lin'!ar. Introduction Reliable techniques for laboratory rearing of bivalve larvae described by Loosanoff and Davis (1963) paved way for development of hatchery techniques for bivalve larvae in both temporal and tropical regions. Successful spat production of the Indian backwater oyster, Crassostrea madrasensis (Nayar et ai, 1982) and the pearl oyster, Pinctada fucata (A1agarswami et ai, 1983) are important works from Indian waters. The present study was under· taken with a view to following the larval development of the rock oyster, Saccostrea cucullata (von Born) upto settlement stage in the laboratory. Material and Methods Mature oysters collected from the rocky shore at Someshwar near Mangalore Clat. 74' 51 'E; long 12' 47'N) 255 were acclimatised in sea water of salinity 30%. for two days. Equal quantities of sperm and egg suspensions in sterile seawater prepared by stripping were mixed. The fertilised eggs were washed free of attached sperms and distributed in three sterile glass trays containing sterile seawater for further development. The D-veligers were transfered to and reared in round bottom glass vessels (20 I capacity) with mild aeration. Dead larvae settled at the centre of the culture vessels were siphoned off and removed daily. Filtered and autoclaved seawater was used for embryonic and early larval development upto first week beyond which filtered , boiled and cooled sea water was used. Salinity was maintained at about 30%0 and seawater changed once in 24 hours during the first week and once in 48 hours subsequently. Trimethoprim (2 mgll) and sulphamethoxazole (10 mgll) were added during every change of water. A mixed diet of fsochrysis galbana and Tetraselmis gracilis was fed (at 37.5 to 50 mill of culture water) at a ratio (by voL) of 2:1 during first four days and 1:1 thereafter. Results and Discussion Details of the early development are presented in Figs 1-3. The embryonic development of the fertilised eggs was observed soon after the extrusion of polar bodies. Rotating blastula (48 to 55 ~m) stage was reached in about 3 h, 40 min. Late trochophore (50 to 55 ~m) appeared by 15 h. The morphometry of developing larvae is given in Table 1. The straight hinge veliger (D-veliger) 67 ~m x 54 ~m) with transparent valves hinged dorsally was obtained at about 22 hours. The notched veligers appeared on the second day. Conspicuous changes in shape and structure were noticed during the late veliger stages from day 3 to day 11. The shell shape changed from 'D' to globular and the size of the velum increased as the growth proceeded. The 12 day old late veligers with slightly elevated umbo reached the umbone stage (109 fLm x 108 ~m). Larvae with well developed umbo were obtained on days 15 and 16. The larvae developed to the Pediveliger stage through an eyed stage. Pediveligers (143 ~m x 160 ~m) obtained on day 18 crawled around on foot. The digestive diverticulum, stomach and intestine were clearly visible. Plantigrade larvae of 20 days old ceased crawling, had velar retractor muscles degen~rated and had calcium crystals over the shell and measured upto a maximum size of 220 ~m x 230 ~m. (average 160 ~m x 17 4 ~m ). There was no settlement of larvae on the cultch materials provided. The relationship 256 between the ,ength and breadth of veliger larvae was linear (Fig. 4). Larval development of oviparous pelecypods follows the same pattern with trochophore as the first larval stage which develops into veliger which metamorphoses to acquire adult structure (Raven , 1964; Sastry, 1979). D-veligers have been reported in 48 hours after fertilisation in S. cucullata (Awati and Rai, 193 1) and 20 hours in C. madrasensis (Nayar et ai, 1982) while in the present study it took 22 hours. The umbone stage was reached in 12 days, eyed stage in 17 days, pediveliger in 18 days and plantigrade in 20 days. In C. madrasensis (Nayar et ai, 1982) the corresponding periods were 7, 17, 18 and 19 days. The pediveligers of S. cucullata prior to the completion of pelagic life was about 153 x 168 flm whereas the pediveligers of C. madrasensis mEoasured 350 x 310 flm (Nayar et ai, 1982). Variations in the size and in time course in larval development in different species of oysters have been observed by several workers (Loosanoff and Davis. 1963; Chanley and Dinamani, 1978; Walne, 1979; Alagarswami et ai., 1983). The variation in the growth rate of larvae under unifrom conditions has also been discussed by Chanley (1955), Ansell ( 1962), and Loosanoff and Davis (1963). Complexity in the morphology and anatomy of the veliger larvae increases as development proceeds. Le pennec (1980) presented the distinguishing characters of larval and post larval shell morphology of eighteen bivalve families . The importance of umbo characteristics in the systematics of closely related species of Crassostrea and Ostrea was stressed by Carriker and Palmer (1979) and Waller (1981 ). The time of metamorphosis is considered to be critical in the life history of bivalves when gross morphJ logical changes such as disappearence of velum, iormation of labial palps and the reorientation of organs in the manUe cavity take place (Bayne, 1976). Remarkable structural changes in the 20 days old plantigrade larvae in the present study indicate their pre-metamorphic stage. Hadfield (1984) considers that some degree of substratum chemical specificity is necessary to induce settlement and metamorphosis in a number of molluscan species. The larvae are known to respond to various stimuli such as light, gravity, current velocity and contact with solid surfaces (Prytherch, 1934; Hopkins, 1935: Schaefer, 1937; Cole and Knight-Jones, 1939 and Korringa, 1941). Chemical basis and chemical specificity of gregarious settlement of oyster larvae of species such as 0. edulis (Cole and Knight-Jones , 1939 and Bayne, 1969), C. virginica (Crisp, 1967) and S. commercialis (Nell and Holliday, 1986) are well known. Thus, the absence of one or a combination of factors might have resulted in the non-settlement of S. cucullata lar vae in the present study. Acknowledgements The authors arE: grat'!fui to Prof. H.P.C. Shetty, DIrector of Instruction (Fisheries) for encouragement. The Junior Research fellowship awarded to the first author by the Indian Council of Agricultural Research, New Delhi during the tenure of which the study was carried out is gratefully acknowledged. References Alagarswami. K .. Dharmaraj, 5 .. Velayudhan, T S., Chellam, A.. Victor, A.C.C. and Gandhi, AD., 1983. Larval rearing and production 01 spat of pear! oyster Pinetada lueata (Gould). Aquaculture , 34(3,4) 287-301. Ansell. A.D., 1962. The functional morphology 01 the larva and the post-larval development of Venus striatuJa (Da Costa). J. mar. bioI. Ass . U.K., 42, 419·443. Awati, r. and Rai , H5., 1931. Oslrea cucuJJata(The Bombay oyster) Indian. Zool. Memoir., 3: 107 pp. Bayne, B.L. 1969. The gregarious behaviour of the larvae of Ostrea eduJis L. at settlement. J. mar. bioI. Ass. U.K., 49: 327-356. Bayne, B.L., 1976. Marine Mussels : 111eir Ecology and Physiology Cambridge University Press, London. Carriker, MR and Palmer, RE., 1979. Ultrastructural morphologenesis of prodissoconch and early dissoconch valves of the oyster Cra.sssostrea virginica. Proc. Nat!. Shelifish Assoc., 69: 103-128. Chanley, P .E ., 1955. Possible causes of growth variations in clam larvae. Proc. Natl. Shellfish Ass ., 45: 84-94. Chanley, P. and Dinamani. P., 1978. Larval development studies. Four species reared in experiments. Catch '78 5(10) : 28-31. Cole. HA. and Knight-Jones. E,W., 1939. Some observations and experiments on the setting behaviour of larvae of Ostrea eduJis. J. Cons. into ExpJor. Mer., 14: 86-105. Crisp. OJ. 1967. Chemical factors inducing settlements in Crassostrea virginica (Gmelin). J. Animal. Ecol., 36: 329-335. Hadfield, G.M., 1984. Settlement requirements of molluscan larvae: A new data on chemical and genetic roles. Aquaculture, 39: 283-298. Hopkins. A.E., 1935. Attachment of larvae of the Olympia oyster . Ostrea JlJrida to plane surfaces, Ecology, 16 : 82-87. Korringa. P., 1941. Experiments and observations on swarming, pelagic life and setting in the European flat oyster Ostrea edulis. Arch. neer. Zool. VT. 5 , 1-249. Le Pennec, M., 1980. The larval and post-larval hinge of some families of bivalve molluscs. 1. mar. bioI. Ass. U.K., 60(3) : 601-617. Loosanoff, VL and Davis, H.C., 1963. Rearing of Bivalve Molluscs in : Advances in Marine Biology !F.5. Russel (Editor) Vol. I Academic Press. LondonlNew York. Nayar. KN .. Rajapandian, M.E., Gandhi, AD. and Gopinathan, C.P., 1982, Induced spawning and larval rear ing of Crassostrea madrasensis (Preston) in the laboratory. Mar. Fish. Infor. Ser. T&E Ser., 44 : 14·16. Nell, JA., Holliday. J.E., 1986. Effects of Potassium and Copper on the settling rate of Sydney rock oyster (Saccostrea commercialis) larvae. Aquaculture. 58 (3-4): 263-267. Prytherch, H.F., 1934. The role of copper in the setting metamorphoses and distribution of the American oyster Ostrea virginica, Ecol. Monogr .. 4, 47·107. Raven, CP., 1964. Development In : Physiology of Mollusca, K.M. Wilbur . and eM. Yonge (Editors) Vol. 1 p.p : 165-169 Academic Press, New York. Sastry. AN .. 1979. Pelecypoda (Excluding Ostreidae) In: Reproduction 01 Marine Invertebrates A.C. Giese and J5. Pearse (Editors ). Vol. V .. Molluscs: Pelecypods and Lesser Classes pp : 113-292 Academic Press New YorklSan Francisco/London. Schaefer, MB., 1937. Attachment of the larvae of the Ostrea gigas. the Japanese oyster, to plane surfaces. Ecology. 18 : 523·572. Walne P.R., 1979. Culture of bivalve molluscs: 50 years experience at Conwy. Fishing News Books Ltd., England. Table I Morphomt'try 01 de-.10ping larvae of S. cucullata Figures in parenthesis denote the ranges . Days after ler1 ilisation 0.92 8 9 W » 12 13 14 15 16 17 18 19 20 21 22 A SO)..lm G Stages 01 De\'eJopment [).\'ehger Notched Veliger Late Veliger Umbone 5l.ase Eyed Stage Pedi\'eliger Plantigrade E 0"'·' .. .. . , .'" : . . ~: '.- . . . '. ' , SO,IJ m @; '. : .-.... . " .. ~ - -.-.. : :. . ' , 257 Waller. T.R., 1981. Functional morphology and development of veliger larvae of the European oyster. Ostrea edulis. Smithson. Contribu. Zoo!.. 328. Mean length ( Ilm) 61 (60.go) 70 (70) 80 (SO) 76 (7()"8U) 88 (KO-9U) " (90-95) 94 (90-100) '" (90- 100) W; ( 1()O. 1I0) »0 {lOO- I20J 109 (105-110) 118 (110- 130) 128 t1 2fi.I30 131 (12fi. 14:') 140 (13Q. I:i01 143 (130- 1:.D) 143 (12Q.. 150) 1;:1 {130-1i5) 166 (150-220) 163 (1 50-200) 113 ( 165-180) , • o Mean Dre.ldth (""" " 60 " " 16 82 89 " lUi WI lOS lOS 123 13i 1;0 lSi 160 ' 68 l i 4 Ii:' 188 k 100 t\Jm (- , (60l (6().70) (60..70) ( 70-80) (80-85) (83-93 (85--95) (95": 10) ( !Q.I I (! ) (100-110) (100-120) (l?IJ.1Jij) ( 120-1 601 ( lJO..I65) ( 14()"IBG) (160) (l 4().. I!lOJ (15IJ...23Q) (160-200) ( l i O-200) ~ W L , Fig . 1. Camera lucida drawings showing the embryonic and early larval development of S. cucuJJata A·B - Unfertilised eggs. C - Fertilised egg, D _ Fertilised egg with polar body. E - T ..... o ceJled stage. F - Four celled stage. G - Cap of micromeres over a large macromere. H - Blastula stage. I - Late Trochophore. J - 0 - veliger. 22 hold. K - Notched veliger. 2 days old . L - Three days old veliger. M - Four days old veliger. N - Seven days old veJiger. 0 - Eight days old veliger. P - Nine days old veliger . 258 A G1?,?, )!':', " (/./ .' \ '// . - . . . IOO)Jm B •• IOO"ur'n Fig. 2. Camera lucida drawings showing the larval development of S. cucuJ/ata. A - Twelve days old veliger. B - Sixteen days old veliger with well developed Umbo. C - PediveJiger. 19 Qa)'!' old, 0 - Plantigrade larva, 20 days old. In: Intestine: St: Stomach: Oi: Digestive divert iculum; Ft: Foot CC: Calcium Crystals: RV = Right valve; LV = Left Valve. •• - M _ _ _ _ _ _ _ _ _ tH.fAOTH C,.AJ m) Fig. 4. The length - breadth relationship of \'eligers of S. cucu/lata. E Fig. 3. Photomicrographs of veliger larvae 01 S. cucullalli A - 0 - veliger. 22 h old ( x 570) B - Late veJiger, 4 days old (x 1440) C - Late veliger, 10 days old (x 1440) 0- Veliger with well developed umbo, 16 days old ex 570) E - Free swimming Pediveliger, 18 days old (x 570) F - Plantigrade larva, 20 days old ex 1440) . 

Larval development of the Rock Oyster Saccostrea cucullata (von Born)

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Larval development of the Rock Oyster Saccostrea cucullata (von Born)

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