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Larval Development of the Rock OysterSaccostrea cucullata (von Born)

P. SUKUMAR'M. MOHAN JOSEPHCollege 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 rockoyster Saccostrea cucuJ/ata (von Born ). In: M. Mohan Joseph (Ed.)The First Indian Fisheries Forum, Proceedings. Asian FisheriesSociety, Indian Branch, Mangalore. pp. 255 _ 258.

AbstractThe 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 larvaewere observed. Amixed diet of single celled algae consisting of Isochrysisgalbana and Tetraselmis gracilis was fed to the larvae. The larvaldevelopmental stages observed include trochophore, D-veliger, lateveliger, umbone stage, pediveJiger and plantigrade. The time taken for thedevelopment of D-veliger, umbone stage, pediveliger and plantigradestages were 22 hours, 12 days, 18 days and 20 days after fertilisationrespectively and their corresponding average length x breadth were 67 x54 J.Lm, 109 x lOS J.Lm, 143 x 160 jl''1 and 166 x 174 The lengthbreadth relationship of veliger larvae was lin'!ar.

IntroductionReliable techniques for laboratory rearing of bivalvelarvae described by Loosanoff and Davis (1963) paved wayfor development of hatchery techniques for bivalve larvaein both temporal and tropical regions. Successful spat

production of the Indian backwater oyster, Crassostreamadrasensis (Nayar et ai, 1982 ) and the pearl oyster,Pinctada fucata (A1agarswami et ai, 1983) are importantworks from Indian waters. The present study was undertaken with a view to following the larval development ofthe rock oyster, Saccostrea cucullata (von Born ) uptosettlement stage in the laboratory.Material and Methods

Mature oysters collected from the rocky shore atSomeshwar near Mangalore Clat. 74 ' 51 'E; long 12' 47'N)255

were acclimatised in sea water of salinity 30%. fordays. Equal quantities of sperm and egg suspensionsterile seawater prepared by stripping were mixed. fertilised eggs were washed free of attached spermsdistributed in three sterile glass trays containing stseawater for further development. The D-veligers transfered to and reared in round bottom glass vesselsI capacity) with mild aeration. Dead larvae settled acentre of the culture vessels were siphoned offremoved daily. Filtered and autoclaved seawater was for embryonic and early larval development upto first wbeyond which filtered, boiled and cooled sea wa terused. Salinity was maintained at about 30%0 and seawchanged once in 24 hours during the first week and on48 hours subsequently. Trimethoprim (2 mgll )sulphamethoxazole (10 mgll ) were added during echange of water. A mixed diet of fsochrysis galbanaTetraselmis gracilis was fed (at 37.5 to 50 mill of cuwater) at a ratio (by voL) of 2:1 during first four days1:1 thereafter.

Results and DiscussionDetails of the early development are presented in

1-3. The embryonic development of the fertilised eggsobserved soon after the extrusion of polar bodies. Rotblastula (48 to 55 ~ m ) stage was reached in about 3min. Late trochophore (50 to 55 ~ m appeared by 15 h.morphometry of developing larvae is given in Table 1straight hinge veliger (D -veliger) 67 ~ m x 54transparent valves hinged dorsally was obtained at a22 hours. The notched veligers appeared on the seday. Conspicuous changes in shape and structure noticed during the late veliger stages from day 3 to daThe shell shape changed from 'D' to globular and theof the velum increased as the growth proceeded. Thday old late veligers with slightly elevated umbo reathe umbone stage (109 fLm x 108 ~ m ) . Larvae withdeveloped umbo were obtained on days 15 and 16.larvae developed to the Pediveliger stage through an stage. Pediveligers (143 ~ m x 160 ~ m obtained on dacrawled around on foot. The digestive diverticustomach and intestine were clearly visible. Plantiglarvae of 20 days old ceased crawling, had velar retramuscles d e g e n ~ r a t e d and had calcium crystals overshell and measured upto a maximum size of 220 ~ m x

(average 160 ~ m x 174 ~ m There was no settlemelarvae on the cultch materials provided. The relation

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256between the ,ength and breadth of veliger larvae was linear(Fig. 4).

Larval development of ovi parous pelecypods follows thesame pattern with trochophore as the first larval stagewhich develops into ve liger which metamorphoses toacquire adult structure (Raven , 1964; Sastry, 1979).D-veligers have been reported in 48 hours after fe rtilisationin S. cucullata (Awati and Rai, 193 1) and 20 hours in C.madrasensis (Nayar et ai, 1982) while in the present studyit took 22 hours. The umbone stage was reached in 12 days,eyed stage in 17 days, pediveliger in 18 days andplantigrade in 20 days. In C. madrasensis (Nayar et ai, 1982 )the corresponding periods were 7, 17, 18 and 19 days. Thepediveligers of S. cuculla ta prior to the complet ion ofpelagic life was about 153 x 168 flm whereas thepediveligers of C. madrasensis mEoasured 350 x 310 flm(Nayar et ai, 1982 ). Variations in the size and in timecourse in larval development in different species ofoysters have been observed by several workers (Loosanoffand Davis. 1963; Chanley and Dinamani, 1978; Walne, 1979;Alagarswami et ai., 1983). The variation in the growth rate oflarvae under unifrom conditions has also been discussedby Chanley (1955 ), Ansell ( 1962 ), and Loosanoff and Davis(1963). Complexity in the morphology and anatomy of theveliger larvae increases as development proceeds. Lepennec (1980) presented the distinguishing characters oflarval and post larval shell morphology of eighteen bivalvefamilies . The importance of umbo characteristics in thesystematics of closely related species of Crassostrea andOstrea was stressed by Carriker and Palmer (1979) andWaller (1981 ). The time of metamorphosis is considered tobe critical in the life history of bivalves when grossmorphJ logical changes such as disappearence of velum,iormation of labial palps and the reorientation of organs inthe manUe cavity take place (Bayne, 1976). Remarkablestructural changes in the 20 days old plantigrade larvae inthe present study indicate their pre-metamorphic stage.

Hadfield (1984) considers that some degree ofsubstratum chemical specificity is necessary to inducesettlement and metamorphosis in a number of molluscanspecies. The larvae are known to respond to variousstimuli such as light, gravity, current ve locity and contactwith solid surfaces (Prytherch , 1934; Hopkins, 1935:Schaefer, 1937; Cole and Knight-Jones, 1939 and Korringa ,1941 ). Chemical basis and chemical specificity ofgregarious settlement of oyster larvae of species such as 0.edulis (Cole and Knight-Jones , 1939 and Bayne, 1969), C.virginica (C risp, 1967) and S. commercialis (Nell andHolliday, 1986) are well known. Thus, the absence of one ora combination of factors might have resulted in the nonsettlement of S. cucullata la rvae in the present study.

AcknowledgementsThe authors arE: grat'!fui to Prof. H.P.C. Shetty, DIrec tor of Instruc

(Fisheries) for encouragement. The Junior Research fellowship awardethe first author by the Indian Council of Agricultural Research , New Dduring the tenure of which the study was carried out is grateacknowledged.

ReferencesAlagarswami. K . Dharmaraj, 5 . Velayudhan, TS., Chellam,A.. Victor, Aand Gandhi, AD. , 1983. Larval rearing and production 01 sp

pear! oyster Pinetada lueata (Gould). Aquaculture, 34(3287-301.Ansell. A.D. , 1962. The functional morphology 01 the larva and

post-larval development of Venus striatuJa (Da Costa). J. mar.Ass . U.K ., 42, 419443.

Awati, r. and Rai , H5., 1931. Oslrea cucuJJata(The Bombay oyster) InZool. Memoir., 3: 107 pp .

Bayne, B.L. 1969. The gregarious behaviour of the larvae of Ostrea eL. at settlement. J. mar. bioI. Ass. U.K., 49 : 327-356.

Bayne , B.L., 1976. Marine Mussels : 111eir Ecology and Phys ioCambridge University Press , London.

Carriker, MR and Palme r , RE., 1979. Ultrastructural morphologenesprodissoconch and early dissoconch valves of the oyCra.sssostrea virginica . Proc. Nat!. Shelifish Assoc., 69: 103-128

Chanley, PE ., 1955. Possible causes of growth variations in clam laProc. Natl. Shellfish Ass ., 45: 84-94.

Chanley, P. and Dinaman i. P., 1978. Larval development studies.species reared in expe riments. Catch '78 5(10) : 28-31.

Col e. HA . and Kn ight-Jones . E,W., 1939. Some observationsexperiments on the setting be haviour of larvae of Ostrea eduJCons. int oExpJor. Mer., 14: 86 -105.

Crisp. OJ. 1967. Chemical fac tors inducing settlements in Crassosvirginica (Gmelin). J. Animal. Ecol., 36: 329-335.

Hadfield, G.M., 1984. Settlement requirements of molluscan larvae: Adata on chem ical and genetic roles . Aquaculture, 39: 283-298.

Hopkins. A.E., 1935. Attachment of larvae of the Olympia oyster . OsJlJrida to plane su rfaces, Eco logy, 16 : 82-87.

Ko rri nga. P., 1941. Expe riments and obse rvations on swarming , pelagicand setting in the European flat oyster Ostrea edulis. Arch. nZool. VT . 5 , 1-249 .Le Pennec , M., 1980 . The larval and post-larval hinge of some familiebivalve molluscs. 1. mar. bioI. Ass. U.K., 60(3) : 601-617.

Loosanoff, VL and Davis, H.C., 1963. Rearing of Bivalve MolluscsAd vances in Marine Biology !F.5. Russel (Editor) Vol. I AcadePress. LondonlNew York.

Nayar. KN . Rajapand ian, M.E., Gandhi, AD. and Go pinathan, C.P., 1Induced spawning and larval rea r ing of Crassostrea madrase(Preston) in the laboratory. Mar. Fish . Infor. Se r. T&E Ser.,1416.

Nell, JA., Holliday. J.E., 1986. Effects of Potassium and Copper onsettling rate of Sydney rock oyster (Saccostrea commercilarvae. Aquaculture . 58 (3 -4): 263-267.

Prytherch, H.F., 1934. The role of copper in the setting me tamorphosesdistribution of the American oyster Ostrea virginica, Ecol. Mon4, 47107.

Raven , CP., 1964. Development In : Physiology of Mollusca, K.M. W. and eM . Yonge (Editors) Vol. 1p.p : 165-169 Academic Press,York.

Sastry. AN . 1979. Pelecypoda (Excluding Ostreidae ) In : ReproductioMarine Invertebrates A.C. Giese and J5. Pearse (Editors ). VoMolluscs: Pelecypods and Lesse r Classes pp : 113-292 AcadePress New YorklSan Francisco/London.

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Schae fer, MB., 1937. Attachment of the larvae of the Os trea gigas. theJapanese oyster, to plane surfaces. Ecology. 18 : 523 572 .

Walne P.R., 1979. Culture of bivalve molluscs: 50 years experience atConwy. Fishing News Books Ltd., England.

Table I Morphomt'try 01de-.10p ing larvae of S. cucullata Figures in parenthesis denote the ranges.Days afterler1 ilisation0.92

89W1213141516171819202122

A

SO)..lm

G

Stages 01De\'eJopment[).\'eh gerNotched VeligerLate Veliger

Umbone 5l.ase

Eyed StagePedi\'eligerPlantigrade

E

0"'. .. ., .'" : . .'.- . .'. ' ,SO,IJ m @. :.- ..... " .... :. . ',

257Waller . T.R., 1981. Functional morphology and development of velige

larvae of the European oyster. Ostrea edulis. Smithson. ContribuZoo!.. 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- I20 J109 (105-110)118 (110-130)128 t1 2fi.I30131 (12fi.14:')140 (13Q. I:i01143 (130- 1:.D)143 (12Q.. 150)1;:1 {130-1i5)166 (150-220 )163 (1 50-200)113 (165-180)

,

o

Mean Dre.ldth(""""0""68289"UiWIlOSlOS12313i10lSi160'68l i 4Ii:'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 iO-200)

~

,Fig . 1. Came ra lucida drawings showing the embryonic and early larval development of S. cucuJJata AB - Unfertilised eggs. C- Fertilised egg , D _ Fertilisedegg 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 oldveliger. P - Nine days old veliger .

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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 ol d veliger. B - Sixteen days old veliger withwell developed Umbo. C - PediveJiger. 19 Qa)'!' old, 0 - Plantigrade larva,20 days old.In: Intestine : St: Stoma ch: Oi: Digestive dive rt iculum; Ft: Foot CC: CalciumCrystals: RV = Right valve ; LV = Left Valve.

- M _ _ _ _ _ _ _ _ _

tH.fAOTH C,.AJ m)Fg. 4. The length - breadth relationship of \'eligers of S. cucu/lata.

E

Fig. 3. Photomicrographs of veliger larvae 01 S. cucullalliA - 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 57 0)E - Free swimming Pediveliger, 18 days old (x 570)F - Plantigrade larva, 20 days old ex 1440)