Eastern oyster

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Eastern oyster

Oyster bed on Cockspur Island, Georgia, US.

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 Puget Sound, Washington, where it is known as the Totten Inlet Virginica. ^[1] Eastern oysters are and have been very popular commercially, so much so that only 1% of the number that existed when the early colonists came to America in the sixteenth century now remains^{[citation needed]}. The Eastern oyster is the state shellfish of Connecticut,^[2] and its shell is the state shell of Virginia and Mississippi.

1 Description
2 Commercial value
3 Diseases
4 See also
5 References

[edit] Description

Main article: Oyster#Physical characteristics

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.

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. One oyster can filter up to 48 gallons of water in 24 hours.

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.

[edit] Commercial value

Main article: Oyster#Oysters as food

The Eastern oyster used to be of great commercial value. Due to the steep decline in the number of oysters in various traditionally harvested areas due to pollution, overfishing, and diseases; the annual harvest has significantly declined. In Maryland, the current catch is about 35,000 to 40,000 bushels (1,200 to 1,400 m³) of oysters a year^{[citation needed]}. Other regions of the east coast of the United States have successful oyster farms, including most notably Cotuit and Wellfleet on Cape Cod, in Massachusetts.

[edit] Diseases

"Dermo" (Perkinsus marinus) is a 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.

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 transmissible 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 Chesapeake Bay in 1959. The parasite has been found from Florida to Maine but has not been associated with mortalities in all areas. About 30 years ago, MSX was described in oysters from Connecticut waters.

MSX arrived with the Pacific oyster, C. gigas, which was introduced into Chesapeake Bay in the 1950's to restock the Chesapeake Bay's declining oyster population. The introduction of MSX further damaged the oyster populations, which are now barely viable. Currently, researchers are looking at the potential of introducing a disease-resistant Asian species of oyster into the Chesapeake Bay.