The Probert Encyclopaedia of Nature

OYSTER

The oyster is a bivalve mollusc of the genus Ostrea constituting the family Ostreidae, or true oyster, family, having the upper valve flat, the lower concave, hinged by an elastic ligament. The mantle, lying against the shell, protects the inner body, which includes respiratory, digestive, and reproductive organs. They are usually found adhering to rocks or other fixed objects in shallow water along the seacoasts, or in brackish water in the mouth of rivers. Oysters commonly change their sex annually or more frequently; females may discharge up to a million eggs during a spawning period.
Research Oyster