Abstract

• Pearl oyster of Pinctada maxima is the largest species in genus Pinctada and commonly found in Myeik Archipelagic waters. Morphology of Pinctada maxima mainly based on shell features such as external scale sculpture, internal features of shell. Its internal organs, especially anal papilla had different shape from other Pinctada taxa. Mantle was enclosing all soft tissues and organs. The adductor muscle was strongest and controls the closing of valves.The fundamental function of mantle is to secrete shell valves and ensure their growth. Gills performed the sieving and sorting of food particles. Labial palps accepted the food particles that filtered from gills or released the unnecessary particles as pseudofeces. The adductor muscle is strongest and controls the closing of valves.