Amusium japonicum   (Gmelin,  1791) (Scallop)
Organism information awaits expert curation
Class: Bivalvia

Image copyrights: b. e. vaughan

Size: 14.0 cm SL

Color: Outside of left valve is reddish brown, with variable shades along the concentric growth marks. Outer colour pattern of subspecies balloti also has small, yellowish and dark brown spots along radial lines on umbonal area, often with a few irregular, larger dark spots towards periphery. Interior of left valve glossy to pale yellow externally and internally. Subspecies balloti has an additional external brown scattering along some concentric growth marks.

Shell thin, medium to large sized (commonly exceeding to 10 cm in length), laterally compressed, almost circular in outline, gaping anteriorly and posteriorly. Both valves somewhat convex, the right (lower) valve only a little more inflated and larger than the left (upper) valve. Ears small, subequal in size and shape, with the right anterior ear faintly sinuated at anteroventral margin and devoid of ctenolium. Surface of left valve with 2 broad and very shallow depressed areas radiating from the umbo to anteroventral and radial lines. Interior of both valves with distinct radial ribs, usually in pairs, much narrower than the flat interspaces and becoming obsolete on umbonal area. Right valve with 42 to 54 internal radial ribs (46 to 54 in the typical subspecies A. japonicum, and 42 to 48 in the southern A. japonicum balloti).

Sexes separate. Spawning occurs in the cool season, from June to November. Growth is relatively rapid (about 7 to 8 cm in the first year), but the number of individuals reaching a 3 or 4 years age is small, because of a high rate of natural mortality.

Synonym (s)
Ostrea japonia Gmelin, 1791
Amusium japonicum formosum Habe, 1964
(Original combination)
Amusium balloti (Bernardi, 1861)
(Junior synonym)
Amusium japonicum taiwanense Dijkstra, 1988
(Junior synonym)

Common Name (s)
Economic Importance and Threats
Importance:  Commercial
Cultured:  Yes

Habitat:  Demersal,Sandy,Muddy


• Andaman and Nicobar Islands, Andaman Islands (Lat: 10) (Long: 93) INDIA

Literature Source(s)
  • Subba Rao, NV and Dey, A (2000) Catalogue of marine molluscs of Andaman and Nicobar Islands Occasional paper no 187 Records of the Zoological Survey of India ZSI 1-323 Available at - NCL, Pune
  • Sealifebase Available at -
  • Poutiers, JM (1998) Bivalves FAO species identification guide for fishery purposes. The living marine resources of the western central Pacific. Volume 1: Seaweeds, corals, bivalves and gastropods FAO, Rome 1 686 pp Available at -
  • Gladys Archerd shell collection Washington State University tri-cities Natural History Museum Available at -
  • Society for the Management of European Biodiversity Data (2009) World Register of Marine Species (WoRMS) Available at -

Page last updated on:2010-05-19

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