Oysters

Posted in Coastal Animals

Oysters

Scientific Name: Crassostrea virginica

The eastern oyster feeds on plankton and algae. It has numerous predators, including birds such as the American oystercatcher, ocean dwellers such as sea anemones, sea stars, sea nettles, some parasites, and humans. About seven weeks after hatching, the eastern oyster reaches sexual maturity. Spawning season is from late spring to early fall during warm weather. Females may release more than 100 million eggs during a season. Only about one percent of the fertilized eggs reach the next stage of maturity.

Within hours of mixing with sperm, the fertilized eggs develop a shell and begin to move on their own. Oyster larvae, each about the size of a grain of pepper, use tiny, probing feet to find a suitable place to attach. Once settled, the foot excretes a cement-like glue. The oyster glues itself in place and spends the rest of its life there. Its lifespan varies, depending on freshwater inflow and predation. 

The valve or shell length of the eastern oyster reaches up to 8 inches (20 cm). It's two shells (called "valves," hence the name bivalve) attach together at one end by a natural hinge and by a single large muscle. The pale white to gray shell is rough with ridges or bumps.

Oysters are protandric-in the first year, they spawn as males, but as they grow larger and develop more energy reserves, they spawn as females. Oysters are also filter-feeders. They feed by using their gills to filter tiny food particles out of the water. Oysters have been found attached to bricks, boats, cans, tires, bottles, crabs, and turtles, but they prefer to attach to other oysters. When a large number of oysters join together, it's called an "oyster reef".



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The Coastal Resources Division of Georgia DNR is the state agency entrusted to manage Georgia’s marshes, beaches, Marine waters and marine fisheries for the benefit of present and future generations.

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