The blue crab's carapace (shell) varies in color from bluish to olive green, and can reach up to 9 inches across. The carapace has nine marginal teeth on each side; the ninth teeth are strong spines. Its claws are bright blue, and those on mature females feature red tips. Blue crabs have three pairs of walking legs and paddle-shaped rear swimming legs. Males have a strongly tapered abdomen, or "apron," that resembles an inverted T, mature females have a broad, rounded abdomen, and immature females have a triangular abdomen.
Blue crabs will feed on nearly anything they can find, including clams, oysters, mussels, smaller crustaceans, freshly dead fish, and plant and animal detritus. They will even eat smaller and soft-shelled blue crabs.
Predators include large fish like croakers and red drum; fish-eating birds like great blue herons; and sea turtles.
Blue crabs mate from May through October in the brackish waters of the Pamlico Sound. Before mating, males cradle a soft-shelled female in their legs, carrying her for several days while he searches for a protected area for her final molt. Once she molts, the pair mates. After mating, the male continues to cradle the female until her shell hardens. Males eventually leave to search for another mate, while females migrate to the saltier waters.
Females develop an external egg mass, or sponge, beneath their aprons. Each bright orange egg mass may contain between 750,000 and two million eggs. The egg mass darkens as the developing larvae consume the orange yolk. Few blue crabs live longer than three years.
The blue crab’s scientific name comes from the Greek words for “beautiful” and “swimmer.”
Male blue crabs are known as “jimmies,” while mature females are called "sooks.