Oysters
mollusks which grow for the most part in marine or brackish water. Inside of the shell is a soft body, which is used for filtering organisms from its environment. The gills process and gather food that the stomach digests. The adductor muscles assists in keeping the shell closed.
Oysters are eaten as food, and have a reputation as an aphrodisiac. Perhaps the definitive work on oysters as food is Consider the Oyster, by M. F. K. Fisher.
True oysters
The "true oysters" are the members of the family Ostreidae, and this includes the edible oysters, which mainly belong to the genera Ostrea, Crassostrea, Ostreola or Saccostrea. Examples are the Edible Oyster, Ostrea edulis, the Olympia Oyster Ostreola conchaphila, Wellfleet oyster and the Eastern Oyster Crassostrea virginica.
Oysters can be canned, eaten raw or cooked. When caught, like all shellfish they have an extremely short shelf-life. They should be fresh when consumed or serious illness can result. Additionally, oysters can host various illness-causing pathogens. Therefore, consumption of raw oysters should be done with caution.
Pearl oysters
Although all oysters (and, indeed, many other bivalves) can secrete pearls, those from edible oysters are commercially valueless. The Pearl Oysters come from a different family, the Pteriidae (Winged Oysters). Both cultivated and natural pearls are obtained from these oysters, though some other mollusks, for example Spondylidae, the Thorny Oysters;
