Common Atlantic Oyster
Crassostrea virginica Gmelin, 1791
“Oysters on the half shell, anyone?” Most people recognize the Common Atlantic Oyster as being the individual plate for each raw oyster one might order in a restaurant. The shell is heavy, and somewhat pear-shaped, or at least elongated.
Sometimes the oysters-au-naturel fancier may find a small soft crab nestled up against his “'erster.” This little commensal creature, the Oyster Crab (Pinnotheres ostreum), entered the oyster as a larva and became a permanent resident.
A fresh oyster shell is a pale gray-white on the outside, and white on the inside. Often there is a purple margin and a purple muscle scar on the inner surface of the shell. The shell may reach a length of 10 inches. It is found all the way from the Gulf of St. Laurence to Florida.
The living oyster, a bivalve, attaches itself to a rock, dock piling, or other hard surface. There it pulls in, using its gills, an average of 3½ gallons of water per hour, in order to absorb oxygen and trap plankton, its food. Meanwhile, the mollusk is growing daily by adding successive layers to its shell. The growth of the plump creature inside is the joy of oystermen and diners.