Marcia opima has a small, glossy, puffed-up shell which ranges from a creamish-brown to grey colour. There are radial dark markings on the shell running from the umbo to the shell margin. Inner surface of the shell is white. Hinge has three teeth and a long ligament. Anterior lateral teeth is absent in left valve, but corresponding depression is present on the right valve

Xavier, Biji

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173Marcia opima (Gmelin, 1791)Biji XavierI D E N T I F I C A T I O NSource of image : RC of CMFRI, TuticorinLocal names: Njavala kakka (Malayalam)MORPHOLOGICAL DESCRIPTIONMarcia opima has a small, glossy, puffed-up shell which ranges from a creamish-brown to greycolour. There are radial dark markings on the shell running from the umbo to the shell margin.Inner surface of the shell is white.  Hinge has three teeth and a long ligament. Anterior lateral teethis absent in left valve, but corresponding depression is present on the right valve.Order : VeneridaFamily : VeneridaeCommon/FAOName (English) : Venus shell174Prioritized species for Mariculture in IndiaP R O F I L EGEOGRAPHICAL DISTRIBUTIONThe species is distributed in Indo-Pacific region from northwest Indian Ocean and the Aden Gulf toIndonesia. Marcia opima is abundantly present along the estuaries and backwaters of South India. Itprefers river-mouths and is found burrowing in the mudflats of Gulf of Mannar, Ashtamudi andKayamkulam Lakes, Ratnagiri, north Kanara, Bombay and Chennai coasts.HABITAT AND BIOLOGYIt is found in muddy-sandy substratum at depths of 1 m. It prefers high salinity and is mostly seen nearbarmouths. Size at first maturity is 18-20 mm. Two spawning peaks are recorded, one in November-January and the other in May-June. Maximum shell length recorded is 58 mm. It grows to 26-33.8 mmin one year and life span is about 3 years. Sexual maturity is observed at size of 11-12 mm, when it is3 months old.175BREEDING IN CAPTIVE CONDITIONSThe broodstock development, breeding and larval rearing of Marcia opima was carried out on anexperimental basis at Tuticorin R. C. of CMFRI.  Shells of 30-48 mm length collected from wildwere used as brooders. They were fed with Isochrysis galbana and Chaetoceros sp. They wereinduced to spawn by raising the temperature to 32 °C for about half an hour. Diameter of thefertilized eggs ranged from 43 to 59 µm. The fertilized eggs and morula were collected in a 40 µmsieve and transferred to larval rearing tanks (1,000 l capacity), after passing through a 100 µmsieve for removing the debris.LARVAL REARINGLarvae ('D' shape) were stocked at densities varying from 0.2-1.2 larvae/ml. Larvae were fedwith Isochrysis galbana at concentration of 5,000 cells/larva/day. The early and late umbo stageswere reached on 5th and 7th day, respectively. Subsequently, feeding was increased to 8,000 cells/larvae/day. Settlement started on day 9 and 10 post-fertilization. Settlement was completed by 11thday, when the larvae measured 273 x 260 µm. At settlement, feeding was increased to 10,000cells/spat/day. On 18th and 20th day, feeding was gradually increased to 12,000 and 20,000 cells/spat/day, respectively. On day 45, the juvenile size varied from 1.7 mm to 3.4 mm.NURSERY REARINGInformation not availableGROW OUTInformation not availableFOOD AND FEEDINGIt is a filter feeder, feeding mostly on marine phytoflagellates.GROWTH RATEInformation not availableDISEASES AND CONTROL MEASURESInformation not availableP R O D U C T I O N  S Y S T E M S176Prioritized species for Mariculture in IndiaPRODUCTIONInformation not availableMARKET AND TRADEGood export market for frozen clam meat exists for Marcia opima. The shells are utilized forcalcium carbide industry.Standardisation of seed production technology for mass scale propagation is a challenge. Themain researchable issues, which have to be sorted out for this species in India, are (i) Larval rearingprotocol: standardization of larval rearing by environmental and nutritional manipulation (ii) Nurseryrearing protocols and (iii) Suitable farming methods.The species is having good local market demand as well as export value. However breeding andseed production as well as farming technology needs to be popularized further. Popularizing thetechnology already developed by CMFRI among fish farmers can go a long way in ensuring theirlivelihood security.Lovatelli, A. 1988. Status of mollusc culture in selected Asian countries. FAO, Rome, 96 pp.Maqbool, T. K. 1993. Studies on the Biology of the clam Marcia opima Gmelin from KayamkulamLake. Ph. D. Thesis. Cochin University of Science and Technology, Cochin, 134 pp.Muthiah, P. 2004. Molluscan Culture: Clam. Ocean-Life, Food and Medicine Expo 2004, p. 1-9.Muthiah, P., Rodrigo, J. X. and Suja, N. 2002. Larval rearing and spat production of Marcia opima(Gmelin). Aquaculture, 211: 393-401.Suja, N. and Muthiah, P. 2005. Parasitic infestation of the clam, Marcia opima (Gmelin). J. Bom.Nat. His. Soc., 102(3): 361-362.Suja, N. and Muthiah, P. 2007. The reproductive biology of the baby clam, Marcia opima, from twogeographically separated areas of India. Aquaculture, 273: 700-710.Suja, N. and Muthiah, P. 2009. Effect of starvation and temperature on gonad development of babyclam, Marcia opima (Gmelin). J. Mar. Biol. Ass. India, 51(1): 21-25.P R O D U C T I O N ,  M A R K E T  A N D  T R A D EC H A L L E N G E S  T O  M A R I C U L T U R EF U T U R E  P R O S P E C T SS U G G E S T E D  R E A D I N G

Marcia opima (Gmelin, 1791)

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Marcia opima (Gmelin, 1791)

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