Shell large, heavy almost equivalve, stongly inequilateral; beaks near the anterior margin. Shell more or less compressed with a triangular projection at the anterior end. Outline almost circular, as hight as broad, with dorsal area straight, yet shorter than length; posterior margin slightly curved, anterior margin flexous. Rough sculpture of concentric ridges which are usually more projecting at the margins and radial rows of wide appressed scales. Hinge without teeth. Ligament in a single triangular depression.
externally greyish green with white or yellowish radial rows of scales. Internally very pearly with a pale blue or violet cast. Margins brown to black.
common size :
to 200 mm in height. 250 mm in the Pacific (Cernohorsky, 1972).
Very similar to P. radiata from which it differs in size, color and shape of the adductor muscle scar: shell of P. radiata is smaller, thinner, tan-colored, usually with reddish to black markings (Oliver, 1992).
BIOLOGY / ECOLOGY
Epifaunal suspension feeders. Because of their commercial interest, population dynamics of both wild and cultured oysters have been studied in various parts of the world. Suspension feeders have a high ability to acquire energy under low phytoplankton conditions. The optimal conditions for maximun survival and growth were 26-29°C and salinity 28-32‰. Temperature of 35°C or greater were lethal for larvae and at all temperatures tested larvae growth and survival were lowest at a salinity of 40‰.
in the Indo-Pacific, lives attached by byssus to hard substrata (under stones, in crevices of rocks, algae), intertidal and subtidal (Cernohorsky, 1972). In Egypt, at depths less than 18m.