If undisturbed, O. virginica may remain in good condition for about four months in air at a temperature a few degrees above freezing. Oysters feed on minute algae and other microorganisms. O. virginica and other oysters may change sex during the winter. Young O. virginica are predominantly males, but toward the end of the first year some of them change into females and a one to one ratio is established. Also present are sodium, potassium, calcium, magnesium, chlorine, bromine, phosphorus and sulphur as well as many heavy metals including iron, copper, zinc, manganese and iodine.
Oyster farming is ancient.
Long before the Christian era the Chinese were cultivating oysters and Romans successfully used artificial methods of growing them. Concern about depletion of oyster supplies has become increasingly strong over the pst five decades. Edible oysters have no true pearls. True pearl oysters of the genus Pinctada inhabit warm waters of the tropics. They differ from edible oysters by the presence of byssus by which they attach themselves to the substratum and by a number of other characters.