Oyster

For the smartcard used in London, England, see Oyster card.

The name oyster is used for a number of different groups of mollusks which grow for the most part in marine or brackish water. Inside a usually highly-calcified shell is a soft body. The gills filter plankton from the water. Strong adductor muscles are used to hold the shell closed.

Oysters are highly prized as food, both raw and cooked, and have a reputation as an aphrodisiac due to the high content of zinc they contain. 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 (others are just as edible); the Olympia Oyster Ostreola conchaphila; Wellfleet oyster and the Eastern Oyster Crassostrea virginica.

Oysters as edibles

Oysters can be eaten raw, or boiled, fried, roasted, stewed, canned, pickled, or broiled. Preparation can be as simple as opening the shell, while cooking can be as spare as adding butter and/or salt, or can be very elaborate.

Like all shellfish, oysters have an extremely short shelf-life, and should be fresh when consumed. Precautions should be respected when eating them (see below). Purists insist on eating oysters raw, with no dressing save perhaps lemon juice or vinegar. Raw oysters are regarded like wines in that they have complex flavors that vary greatly among varieties and regions: some taste sweet, others salty or with a mineral flavor, or even like melon. The texture is soft and fleshy, but crisp to the tooth.

Oysters are generally an expensive food in places where they aren't harvested, and often they are eaten only on special occasions, such as Christmas. Whether oysters are predominantly eaten raw or cooked is a matter of cultural preference. In the United States today, oysters are usually cooked before consumption; canned smoked oysters are widely available as preserves with a long shelf life. Raw oysters were, however, once a staple food along the East Coast of the US, and are still easily found in states bordering the ocean. Oysters are nearly always eaten raw in France.

Fresh oysters must be alive just before consumption. There is a simple criterion: oysters must be tightly closed; oysters that are already open are dead and must be discarded. Opening oysters requires skill, for live oysters, outside of the water, shut themselves tightly with a powerful muscle. The generally used method for opening oysters is to use a special knife (called a shucking knife), with a short and thick blade, inserting the blade (with some moderate force and vibration if necessary) at the hinge in the rear of the shell, and sliding it upward to cut the adductor muscle (which holds the shell closed). Inexperienced cooks can easily slip and injure themselves; this is said to be a significant cause of domestic accidents in the Christmas season in France.

An alternative to opening raw oysters before consumption is to cook them in the shell – the heat kills the oysters and they open by themselves. Cooked oysters are savory and slightly sweet-tasting, and the varieties are mostly equivalent.

A piece of folk wisdom concerning oysters is that they are only safe to eat in months containing the letter 'r.' This is because oysters spawn in the warmer months, from roughly May to August. They are safe to eat at all times of the year, although their flavor when eaten raw can be somewhat watery and bland during spawning season. Oysters from the Gulf of Mexico spawn throughout the year, and are generally best cooked.

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 freshwater mussels, also yield pearls of commercial value.

Dermo

"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.

Other molluscs named "oyster"

A number of other molluscs not falling into either of these groups have common names that include the word "oyster", usually because they either taste or look like oysters, or because they yield noticeable pearls. Examples include:

• the family Spondylidae, the Thorny Oysters;
• the Pilgrim oyster, a kind of scallop.

See also

• Oyster sauce

External links

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• Family tree of Molluscs (http://www.perlas.com.mx/Ingles/famtree.htm)da:Østers

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