Eastern oyster

Eastern oyster
Oyster bed on Cockspur Island, Georgia
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Bivalvia
Order:	Ostreoida
Family:	Ostreidae
Genus:	Crassostrea
Species:	C. virginica
Binomial name
Crassostrea virginica Gmelin, 1791

The Eastern oyster (Crassostrea virginica), also known as the American oyster, Atlantic oyster, or the Virginia oyster, is a species of oyster that is native to the Eastern Seaboard of North America. It is also farmed in the Puget Sound of Washington, where it is known as the Totten Inlet Virginica.

Like all oysters, Crassostrea virginica is a hard shellfish that comes in several different sizes, usually 5 to 15 cm (2 to 6 inches) long. It has hard edges that supply a tough shield against predators. They are popular on the market, so much so that only 1% of the number that existed when the early colonists came to America in the sixteenth century now remains.

This particular type of oyster has an important environmental value. Like all oysters, Crassostrea virginica is a filter feeder. They suck in water and filter out the plankton and detritus to swallow, then spit the water back out, thus cleaning the water around them and getting rid of much of the eastern Chesapeake Bay's notorious water pollution.

People catch and eat these oysters, mainly in the spring, and (in Maryland) catch about 35,000 to 40,000 bushels (1,200 to 1,400 m³) of oysters a year. This has resulted in the decline of the numbers of C. virginica.

"Dermo" (Perkinsus marinus) is marine disease of oysters, caused by a protozoan parasite. It is a prevalent pathogen of oysters, causing massive mortality in oyster populations and poses a significant economic threat to the oyster industry.

The Eastern oyster, like all members of the family Ostreidae, can make small pearls to surround particles that enter the shell. However these pearls are insignificant in size and of no value; the Pearl Oyster, from which commercial pearls are harvested, is of a different family.

The Eastern oyster shell is the state shell of Virginia, Mississippi and Connecticut.

Another disease which has decimated the Eastern oyster is MSX (Haplosporidium nelsoni). MSX is a single-celled Protozoan parasite. It is not known to be harmful to humans but it is transmissable from oyster to oyster. How this is done is not known because the life cycle of this parasite is not fully understood. MSX disease caused massive oyster mortalities in Delaware Bay in 1957 and in the Chesapeake Bay in 1959. The parasite has been found from Florida to Maine but has not been associated with mortalities at all areas. About 30 years ago, MSX was described in oysters from Connecticut waters.