This paper reports on the larvae development of the flat oyster, Ostrea edulis (Linnaeus, 1758), from veliger to pediveliger stage. Adult oysters were induced to spawn by thermal stimulation and large amounts of veliger larvae were obtained for study. Veliger larvae were cultured in 180-l bins at a den- sity of 3 larvae/ml. Larvae, reared at 20±2°C and fed 8-200 x 103 cells/ml of Isochrysis galbana, reached pediveliger larvae in 17 days. Shell length and width at the beginning of the pediveliger stage were 254 and 233 μm, respec- tively. Survival rate from veliger to viable pediveliger stage was 15.5%

Acarli, Sefa

Lok, Aynur

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The Open Access Israeli Journal of Aquaculture – BamidgehAs from January 2010 The Israeli Journal of Aquaculture - Bamidgeh (IJA) will be published  exclusively  as  an  on-line  Open  Access  (OA) quarterly  accessible  by  all AquacultureHub  (http://www.aquaculturehub.org)  members  and  registered  individuals and institutions.  Please visit our website (http://siamb.org.il) for free registration form, further information and instructions.  This transformation from a subscription printed version to an on-line OA journal, aims at supporting the concept that scientific peer-reviewed publications should be made available to all, including those with limited resources. The OA IJA does not enforce author or subscription fees and will endeavor to obtain alternative sources of income to support this policy for as long as possible.Editor-in-ChiefDan Mires Editorial BoardSheenan Harpaz Agricultural Research OrganizationBeit Dagan, IsraelZvi Yaron Dept. of ZoologyTel Aviv UniversityTel Aviv, IsraelAngelo Colorni National Center for Mariculture, IOLREilat, IsraelRina Chakrabarti Aqua Research LabDept. of ZoologyUniversity of DelhiIngrid Lupatsch Swansea UniversitySingleton Park, Swansea, UKJaap van Rijn The Hebrew University Faculty of AgricultureIsraelSpencer Malecha Dept. of Human Nutrition, Food and Animal SciencesUniversity of HawaiiDaniel Golani The Hebrew University of JerusalemJerusalem, IsraelEmilio Tibaldi Udine UniversityUdine, ItalyCopy Editor Ellen Rosenberg Published under auspices ofThe Society of Israeli Aquaculture and Marine Biotechnology (SIAMB), University of Hawaii at Manoa Library andUniversity of Hawaii Aquaculture Program in association withAquacultureHub http://www.aquaculturehub.org              ISSN 0792 - 156X Israeli Journal of Aquaculture - BAMIGDEH.PUBLISHER: Israeli Journal of Aquaculture - BAMIGDEH -Kibbutz Ein Hamifratz, Mobile Post 25210, ISRAELPhone: + 972 52 3965809http://siamb.org.il The Israeli Journal of Aquaculture – Bamidgeh  61(2), 2009, 114-120. 114Abstract This paper reports on the larvae development of the flat oyster, Ostrea edulis(Linnaeus, 1758), from veliger to pediveliger stage. Adult oysters wereinduced to spawn by thermal stimulation and large amounts of veliger larvaewere obtained for study. Veliger larvae were cultured in 180-l bins at a den-sity of 3 larvae/ml. Larvae, reared at 20±2°C and fed 8-200 x 103 cells/ml ofIsochrysis galbana, reached pediveliger larvae in 17 days. Shell length andwidth at the beginning of the pediveliger stage were 254 and 233 µm, respec-tively. Survival rate from veliger to viable pediveliger stage was 15.5%.IntroductionOysters are the most common of all bivalves and have been known to man as edible and deli-cious for centuries. Two oyster species have been reported along the Turkish coast: Ostreaedulis (Fischer et al., 1987) and Crassostrea gigas (Dogan et al., 2006). These species are con-siderable resources for human consumption and obtain high market prices. Earlier studies on O. edulis dealt with growth (Alpbaz et al., 1990; Alpbaz et al., 1993), repro-ductive biology (Yolkolu and Lok, 2000), and aquaculture (Hindioglu and Alpbaz, 1991; Lok andAcarli, 2006). Larvae development in several bivalve species has been studied, providing basicknowledge for the aquaculture of oysters (Loosanof and Davis, 1963; Loosanof et al., 1966;Utting and Spencer, 1991). Larvae stages in oysters were defined by Waller (1981) and Elston(1999), while shell morphogenesis was studied by Carriker and Palmer (1979).*  Corresponding author. Tel.: +90-232-3884000, ext. 1306, fax: +90-232-3883685, e-mail: sefa.yolkolu.acarli@ege.edu.trLarvae Development Stages of the European Flat Oyster(Ostrea edulis)Sefa Acarli* and Aynur LokDepartment of Aquaculture, Fisheries Faculty, Ege University, Bornova 35100, Izmir, Turkey(Received 22.2.08, Accepted 9.8.08)Key words: flat oyster, Ostrea edulis, larvae stages, larvae development, pediveligerFull article available to e-journal subscribersonly at http://www.siamb.org.il115The aim of the present study was to describe development stages, growth, and survival ratesof O. edulis larvae from the veliger to the pediveliger stages.Materials and MethodsRipe adult individuals of O. edulis were obtained from Mersin Bay in the Aegean Sea, Turkey, in2003. To induce spawning, oysters were cleaned of encrusting organisms, left out of the waterovernight (Satuito et al., 1994), and submitted to a thermal shock of 26°C. Immediately afterrelease from the pallial cavity of the parent oyster, larvae were transferred to three 180-l tanksat a rate of 3 larvae/ml and cultured in 20±2°C sea water, filtered at 1 µm and sterilized by ultra-violet treatment. The larvae were fed 8-200 x 103 cells/ml Isochrysis galbana obtained from theexperimental hatchery of the Fisheries Faculty at Ege University. Microalgae were cultivated inbatch cultures at 25-27°C. Only cultures in the log phase of growth were used for feeding. Larvaewere fed by the method of Tibile and Singh (2003).Trials were initiated with normally developed veligers at a density of 3,000 larvae per liter.The larvae cultures were maintained at a salinity of 36-36.2% and 20±2°C, the optimal temper-ature for larvae development (Davis and Calabrase, 1969; Beiras et al., 1995). The culturemedia was completely changed every 48.h, when 50 larvae from each tank were sampled torecord length (anterior-posterior), width (dorsa-ventral), and morphological changes in the velumand umbo area. Larvae were measured with an ocular micrometer according to Satuito et al.(1994).The instantaneous growth rate (K) was calculated according to the formula: K = (lnLt - lnL0)/t(Brown and Robert, 2002), where Lt is the measured length at time t, L0 is the length at the startof the experiment, and t is the number of days since the start of the experiment. The relationshipbetween shell length and width was described by the linear equation: L = a + bW, where L is theshell length, W is the width, and a and b are fitted parameters.Three 1-ml samples were taken to determine mean survival according to the formula: sur-vival = (Nt/N0) x 100, where Nt is the number of live larvae at time t and N0 is the number of livelarvae at the beginning of the experiment.Data were pooled for regression analysis and analyzed with one-way ANOVA to examine theeffects of each passing day on growth. Survival data were arcsine transformed before statisticaltreatment and analyzed by Chi-square (χ2). Differences were considered significant whenp<0.05. All statistics were executed using SPSS software.ResultsFour larval stages were observed during the 17-day experiment: veliger, early umbo, umbo, andpediveliger (Fig. 1).Veliger stage. When newly released from the pallial cavity of the adult oysters, the veliger lar-vae had a mean size of 147±5.0 x 126±7.2 µm (SE = 3.28, n = 50). The veliger stage is alsoknown as the straight hinge or ‘D’ shell stage. During this stage, larvae are semi-transparent andthe velum protrudes, creating a strong ciliary current. This stage lasted 5 days during which nomortality was observed (Table 1, Fig. 2). When the air flow was closed, veliger larvae swam nearthe surface of the tanks. Early umbo (veliconcha). On the fifth day, the first larvae entered the early umbo stage. Theshape of the larvae changed and resembled a ball. The umbo became slightly oval. At this stage,larvae were less mobile than in the veliger stage and swam through the water column. Some ofthe larvae shells were broken. Larvae measured 210±8.99 x 185±12.11 µm.Umbo stage. At the end of the eighth day, the first larvae entered the fully-developed umbostage. The umbo area was distinctly observed and larvae averaged 239±30.32 x 208±29.26 µm.Larvae swam more slowly than in earlier stages. The cilary part of the velum was also lessactive. The majority of larvae reached the umbo stage by day 14.Larvae development of the European flat oysterPediveliger stage. The firstlarvae reached the pediveligerstage by day 17. A functionalfoot and eye spot were easilyobserved in this stage. Larvaecongregated deeper in thewater column and near sub-strates, moving along surfacespropelled by their prominentfoot and beginning to seek suit-able attachment grounds. Atthe end of the 17-day experi-ment, larvae ranged 240-300µm in length and averaged254±33.37 x 233±33.83 µm.Growth rates. The averagegrowth rate was 7.87 µm/dayfrom veliger to early umbostage, 4.57 µm/day from early umbo to umbo stage, and 5 µm/day from umbo to pediveligerstage. The best instantaneous growth rates for shell length and width were observed on days 8(0.04475) and 10 (0.044228), respectively (Fig. 3). Growth sharply dropped on day 12. Shellshad a total increase of 107 µm in both length and width. The average daily growth was 6.29µm/day. The relationship between shell length (L) and shell width (W) was linear and described116 Acarli and LokTable 1. Development of Ostrea edulis larvae.Larvae stage (%)Day Veliger Early umbo Umbo Pediveliger1 100 - - -2 100 - - -5 100 - - -8 28.71 28.71 42.58 -10 23.81 19.04 57.15 -12 14.89 14.89 70.22 -14 9.52 - 90.48 -17 - 6.6 71.2 22.2Fig. 1. Larvae stages in the European oyster (Ostrea edulis): (a) veliger, (b) early umbo, (c) umbo, and(d-f) pediveliger.a b cd e f117by the equation L = 1.068W + 13.143, r = 0.9313 (Fig. 4). The effect of day on larvae growth sig-nificantly differed between days (p<0.01).Survival. Survival to the pediveliger stage was 15.5%. Mortality significantly differed fromveliger to pediveliger (p<0.05). Mortality was heavy between days 10 and 12. Larvae development of the European flat oysterFig. 3. Instantaneous growth rate of Ostrea edulis larvae during thestudy period.Fig. 2. Survival, shell length, and shell width of Ostrea edulis larvaecultured for 17 days from the veliger to the pediveliger stage.DayLarvae size (µm)Survival (%)280240200160120804001201008060402000 2 5 8 10 12 14 17Shell lengthShell widthSurvival rateGrowth rate (K)0.050.0450.040.0350.030.0250.020.0150.010.0050Day2 5 8 10 12 14 17Length Width118 Acarli and LokFig. 4. Relationship between shell length and width of Ostrea edulislarvae.Shell length (µm)420370320270220170120100 150 200 250 300 350Shell width (µm)L = 1.068W + 13.143R2 = 0.8681   r=0.9313DiscussionBivalve broodstock can be induced to spawn by thermal or chemical stimulation of the sperm oregg, or electric or mechanic shock (Loosonoff and Davis, 1963). Thermal stimulation is preferredsince temperature fluctuation induces spawning with less injury. In the present investigation, O.edulis were induced to spawn by fluctuating water temperature from 18°C to 26°C. This methodof spawning bivalve species was also reported by Myers and Boisvert (1988). In general, morphological features of pediveligers, such as a functional foot, presence of aneye-spot, and shell size, are important indicators of competent metamorphosis in bivalve larvae(Utting and Spencer, 1991; Helm and Bourne, 2004). In our study, larvae grew from veliger topediveliger within 17 days. In contrast, larger pediveliger larvae of O. edulis (280-290 µm inlength) have been obtained within 9 or 10 days (Walne, 1966). In Crassostrea gryphoides, lar-vae similarly reached the pediveliger stage on day 18 (at 23°C) but at 300-350 µm (Tibile andSingh, 2003) or on day 20 at 280-300 µm (Utting and Spencer, 1991).Larvae of bivalves have exponential growth (Gosling, 2007) and growth rates are likely to beinfluenced by genetic factors, endogenous and exogenous nutrition, and culture conditions(Doroudi and Southgate, 2003). The activity of bivalves is generally controlled by water temper-ature (Tomaru et al., 2002). In O. edulis, shell growth is especially affected by water tempera-ture (Wilson, 1987). High temperatures and frost are not tolerated by O. edulis (Bardach et al.1972; Korringa, 1976). Larvae have been successfully reared from veliger to pediveliger at 18-20°C (Russell, 1963) while salinity within the range 25-35‰ has little effect on growth of O.edulis larvae (Davis and Ansell, 1962). Because of this, water temperature and salinity were keptat 20±2°C and 36‰ in our study. Survival was 100% during the first five days and only 15% at the end of the experiment. Thisrelatively poor survival contrasts with the findings of Davis and Calabrese (1969) who reported70% of cultured O. edulis larvae reached pediveliger larvae stage in hatchery trials. Larvae of O.edulis are more sensitive than larvae of other oyster species such as C. gigas or C. virginica.119Therefore the success of culturing O. edulis larvae is low. In the present study, survival and thegrowth rate sharply decreased on day 12. The reason for the decline can be morphologicalchanges in larvae from veliger to umbo stage or unknown changes in the water quality.In conclusion, larvae developmental stages were defined using standard culture methods.Further research is required to establish feeding standards (algae species and densities) duringdifferent larvae stages, determine the effects of salinity and temperature on larvae growth/sur-vival, and examine the biochemical composition of broodstock and larvae. ReferencesAlpbaz A., 1993. Kabuklu ve eklembacaklilar yetistiriciligi. E.U. Su Urunleri Fakultesi Yayinlari,26:82-130 (in Turkish).Alpbaz A., Onen M. and I. Corus, 1990. Investigation on oysters (Ostrea edulis) collected fromIskele-Urla. E.U. Su Urunleri Dergisi, 7(25-28):116-126 (in Turkish).Bardach J.E., Ryther J.H. and W.O. McLarney, 1972. Aquaculture: The Farming andHusbandry of Freshwater and Marine Organisms. Wiley Interscience, New York. pp. 674-742.Beiras R., Perez-Camacho A. and M. Albentosa, 1995. Short-term alterations in the energybudget of young oyster Ostrea edulis L. in response to temperature. J. Exp. Mar. Biol. Ecol.,186:221-236.Brown M. and R. Robert, 2002. Preparation and assessment of microalgal concentrates asfeeds for larval juvenile Pacific oyster (Crassostrea gigas). Aquaculture, 207:289-309.Carriker M.R. and R.E. Palmer, 1979. Ultrastructual morphogenesis of prodissconch and earlydissoconch valves of oyster Crassostrea virginica. Proc. Nat. Shellfish Assoc., 69:103-128.Davis H.C. and A.D. Ansell, 1962. Survival and growth of larvae of the European oyster, Ostreaedulis, at lowered salinities. Biol. Bull., 122:33-39. Davis H.C. and A. Calabrase, 1969. Survival and growth of larvae of the European oyster(Ostrea edulis L.) at different temperatures. Biol. Bull., 136:193-199.Dogan A., Onen M. and B. Ozturk, 2006. Ildir korfezi (Izmir-Cesme) Bivalvia (Mollusca)Faunasi. Turkish J. Aquat. Life, 3-5(5-8):27-35 (in Turkish).Doroudi M.S. and P.C. Southgate, 2003. Embryonic and larval development of Pinctada mar-garitifera (Linnaeus, 1758). Moll. Res., 23:101-107. Elston R.A., 1999. Health Management, Development and Histology of Seed Oysters. WorldAquac. Soc., Baton Rouge, LA. 110 pp. Fischer W., Bauchot M.L. and M. Schneider, 1987. Mediterranee et Mer Noire, Zone de Peche37, rev. 1, vol. 1 Vegetauxet Invertebres. Rome, 631 pp.Gosling E., 2007. Bivalve Molluscs: Biology, Ecology and Culture. Fishing News Books, Oxford.443 pp.Helm M.M. and N. Bourne, 2004. Hatchery Culture of Bivalves. FAO, UN, Rome. 168 pp.Hindioglu A. and A. Alpbaz, 1991. Istiridye (Ostrea edulis, L 1758) larvasi uretimi uzerine ara-stirmalar. pp. 578-589. In: A.G. Elbek (ed.). Fish. Aquac. Symp., November 12-14, Izmir. 751 pp(in Turkish).Korringa P., 1976. Farming the Flat Oysters of the Genus: Crassostrea. Elsevier Sci. Publ. Co.,New York. 219 pp. Lok A. and S. Acarli, 2006. Preliminary study of settlement of flat oyster spat (Ostrea edulis L.)on oyster and mussel shell collectors. Isr. J. Aquac. - Bamidgeh, 58(2):105-115.Loosanoff V. and H.C. Davis, 1963. Rearing of bivalve larvae. Adv. Mar. Biol., 1:1-136. Loosanof V., Davis H.C. and P.E. Chanley, 1966. Dimensions and shapes of larvae of somemarine bivalve mollusks. Malacologie, 4:351-435.Myers J.A. and R.N. Boisvert, 1988. The Economics of Hatchery Produced Algae and BivalveSeed. Dept. Agric. Econ., NY State College of Agric. Life Sci., 88-7. 94 pp.Russell F.S., 1963. Advances in Marine Biology. Acad. Press, London. 409 pp.Larvae development of the European flat oysterSatuito C.G., Natoyama K., Yamazaki M. and N. Fusetani, 1994. Larval development of theMytilus edulis gallopravincialis cultured under laboratory conditions. Fish. Sci., 60(1):65-68.Tibile R.M. and H. Singh, 2003. Larval rearing and spat production of edible oyster Crassostreagryphoides (Schlotheim). Aquac. Res., 34:785-792.Tomaru Y., Kumatabara Y., Kawabata Z. and S. Nakano, 2002. Effect of water temperatureand chlorophyll abundance on shell growth of the Japanese pearl oyster, Pinctada fucatamartensii, in suspended culture at different depths and sites. Aquac. Res., 33:109-116.Utting S.D. and B.E. Spencer, 1991. The Hatchery Culture of Bivalve Mollusk Larvae andJuveniles. Laboratory leaflet 68, Min. Aquac., Fish. Food Directorate of Fish. Res. 31 pp.Waller T.R., 1981. Functional morphology and development of veliger larvae of the Europeanoyster Ostrea edulis Linne. Smithsonian Contrib. Zool., 328:1-71.Walne P.R., 1966. Experiments in the Large-Scale Culture of the Larvae of Ostrea edulis L. Fish.Invest., Ser. 2, 25(9):1-53.Wilson J.H., 1987. Environmental parameters controlling growth of Ostrea edulis L. and Pectenmaximus L. in suspended culture. Aquaculture, 64:119-131.Yolkolu (Acarli) S. and A. Lok, 2000. 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Larvae Development Stages of the European Flat Oyster (Ostrea edulis)

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Larvae Development Stages of the European Flat Oyster (Ostrea edulis)

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