Anomia achaeus   Gray,  1849 (Oyster)
Organism information awaits expert curation
Class: Bivalvia

Image copyrights: Government of India

Size: 20 mm; length 16.40-25.10 mm; width 21.50-28.15 mm.

Color: Golden yellow.

The shell of adult oyster is free, very much compressed, slightly unequal, sub-orbicular in shape, the height and length approximately equal. The shell valves are slightly unequal, very flat, rounded and translucent. The inner surface of the valves is pearly. The adductor impression is at about center. The umbo is small. Two thin ridge like teeth diverge from the umbo making a characteristic inverted V shape angle. It bears numerous concentric line of growth on the exterior consisting of slightly projecting lamellae the margins of which are minutely uneven with finger-like or spatulate processes.

The body is very much laterally compressed and is covered by two folds of mantle. Anteriorly on either side of the visceral mass is a pair of elongated, narrow labial pulps between which is the mouth. There is a pair of gills on either side of the visceral mass. The foot is cylindrical and its tip has a cuplike sucker, which facilitates dispersal of foreign matter settling on the body. The alimentary canal consists of a slit-like mouth, esophagus, a large stomach surrounded by the digestive gland, well-developed pyloric caecum with crystalline style, a short intestine, a rectum which ends by anus in the center of the broad ventricle membranous collar. The vascular system consists of the heart with a ventricle and two auricle, a single aorta, the anterior aorta, arteries and venous sinuses. The nervous system consists of a pair of widely separated and asymmetric cerebral ganglia, a pedal ganglion formed by the fusion of paired pedal ganglia and single parieto-splanchnic ganglion, from which nerves lead to different parts of the body. The excretory system is composed of a pair of asymmetric nephridia which are connected dorsally by a short, transverse channel. The right nephridium has a long caecum posteriorly while the left one has only a short caecum. The nephidia open separately to the exterior. The gonad opens into the inter-nephridial passage by a small aperture.

Sexes are separate. The sex of the oyster is determined by the age and sea condition.

Synonym (s)
Anomia achaeus Gray, 1850
Anomia argyritis Reeve, 1859
Anomia malleata Reeve, 1859
Anomia plenilunium Reeve, 1859
Anomia sol Reeve, 1859
Anomia achaeus Gray, 1849
Anomia achaeus Reeve, 1859
Anomia achaeus Kundu, 1965

Common Name (s)
Economic Importance and Threats
Importance:  Commercial
(Shells are used for glazing windows and doors and as decorative pieces. Pearls can be obtained, though of poor quality.)

Habitat:  Demersal,Rocky,Muddy


• Gujarat, Gulf of Kachchh (Lat: 22.6) (Long: 69.5) INDIA
• Andhra Pradesh, Godavari Estuary (Lat: 16.63) (Long: 82.3) INDIA
• West Bengal, Digha Coast (Lat: 21.61) (Long: 87.53) INDIA
• Orissa, Chilika Lagoon (Lat: 19.77) (Long: 85.33) INDIA
• Orissa, Chilika Lake INDIA (Record: 1986)
• West Bengal INDIA
• Maharashtra INDIA
• Gujarat INDIA
• Karachi PAKISTAN
• West Bengal, Digha INDIA
• West Bengal, Medinipur INDIA
• Andhra Pradesh INDIA
• Kerala INDIA
• Persian Gulf
• Gulf of Aden
• Maharashtra, Mumbai INDIA

Literature Source(s)
  • (2001) Fauna of Godavari estuary, Andhra Pradesh Estuarine ecosystem series 4 ZSI, Kolkata 1-166 Available at - ZSI, Pune
  • OBIS Indo-Pacific molluscan database Available at -
  • Ramakrishna; Sarkar, J and Talukdar, S (2003) Marine invertebrates of Digha coast and some recomendations on their conservation Records of the Zoological Survey of India ZSI, Kolkata 101(3-4) 1 Available at - NCL, Pune
  • Subba Rao, NV and Sastry, DRK (2005) Fauna of Marine National Park, Gulf of Kuchchh (Gujarat) ZSI 79 pp Available at - NCL, Pune
  • Goswami, BCB (1992) Marine fauna of Digha coast of West Bengal, India Journal of Marine Biological Association of India The Marine Biological Association of India, Cochin 34 115-137 Available at - NIO, RC Kochi
  • Sealifebase Available at -
  • Branch, GM; Griffiths, CL; Branch, CL and Beckley, LE (2008) Two oceans: A guide to the marine life of Southern Africa Struik Publishers 359 pp Available at -
  • Dholakia, AD (2004) Window pane oyster fishery Fisheries and aquatic resources of India Daya Books 413 pp Available at -
  • Rao, NVS; Rao, KVS and Manna, RN (1995) Mollusca Wetland ecosystem series 1: Fauna of Chilka lake ZSI, Calcutta 391-468 Available at - NIO, Goa
  • Society for the Management of European Biodiversity Data (2009) World Register of Marine Species (WoRMS) Available at -
  • Subba Rao, NV; Dey, A and Barua, S (1992) Estuarine and marine molluscs Fauna of West Bengal Part 9 (State fauna series 3) ZSI, Calcutta 129-268 Available at - NIO, Goa
  • Jaiswar, AK and Kulkarni, BG (2001) Vertical distribution of molluscs in the intertidal area in and around Mumbai, India Journal of Indian fisheries association Indian fisheries association, Mumbai, India 28 93-100 Available at - NIO, Goa

Page last updated on:2010-12-29

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