Shell solid, inequivalve, inequilateral. Shape oyster-like, very variable, depending on the substratum and biotope with outline irregular, almost circular to oval. Sculpture smooth or with strong radial ribs or even with spines. Lower valve (lv) larger and sometimes prominently convex, having a large area with no sculpture at the umbo (area of attachment); its margin with plications. Upper valve (rv) almost flat with plicated margin to fit the plications of the lower valve. Hinge without teeth, Ligament internal. Muscle scar close to the pallial line, very prominent, kidney shaped. Interior shell margin of rv with prominent denticles which fit into the corresponding pits in the lv margin.
externally purple-brown; internally white with a purple-black zone in the periphery. Denticles white. Muscle scar often darker color.
common size :
40-60 mm in height in the Mediterranean (up to 130 mm in the Pacific).
Saccostrea differs from Crassostrea in having the margin crenulated and from Ostrea by crenulation present all along the shell's periphery (in Ostrea only in the anterior margin near the hinge). Because of shell plasticity, the taxonomy of Saccostrea has been problematic. Oliver (1922) thinks that Saccostrea is a monospecific genus and reports S. cucculata in the Red Sea. However molecular biology studies (mitochondrial DNA 16S sequence) of Saccostrea populations in Australia recognize at least three different species (Lam and Morton, 2001).
BIOLOGY / ECOLOGY
Epifaunal, suspension feeder. Spawning period from June to mid-October. Optimum temperature for reproduction 20-30°C. Can tolerate a wide range of temperatures, between 5 and nearly 40°C. Gametogenesis is concominant with higher salinity values (33.37-34.65‰ ) and full maturation is attained when the salinity is maximum (35‰).
high intertidal on rocky shores, cemented to rocks. In the Mediterranean, attached to rocks in harbours. At depths 1-15 m covered with macroalgae.