Callinectes sapidus

Appearance

''Callinectes sapidus'' may grow to a carapace width of 230 mm . It can be distinguished from a related species that occurs in the same area by the number of frontal teeth on the carapace; ''C. sapidus'' has four, while ''C. ornatus'' has six.

Male and females of ''C. sapidus'' can be distinguished by the sexual dimorphism in the shape of the abdomen . It is long and slender in males, but wide and rounded in mature females; one popular mnemonic is that the male's is shaped like the Washington Monument, while the female's resembles the dome of the United States Capitol. A female's abdomen changes as it matures: an immature female has a triangular shaped abdomen, whereas a mature female's is rounded.

The blue hue stems from a number of pigments in the shell, including alpha-crustacyanin, which interacts with a red pigment, astaxanthin, to form a greenish-blue coloration. When the crab is cooked, the alpha-crustacyanin breaks down, leaving only the astaxanthin, which turns the crab red-orange.

Distribution

''Callinectes sapidus'' is native to the western edge of the Atlantic Ocean from Nova Scotia to Argentina and around the entire coast of the Gulf of Mexico. It has been introduced to Japanese and European waters, and has been observed in the Baltic Sea, North Sea, Mediterranean Sea and Black Sea. The first record from European waters was made in 1901 at Rochefort, France. In some parts of its introduced range, ''C. sapidus'' has become the subject of crab fishery, including in Greece, where the local population may be reducing as a result of overfishing.

Behavior

In the Chesapeake Bay, ''C. sapidus'' undergoes a seasonal migration. After mating, the female crab travels to the southern portion of the Chesapeake, using ebb tide transport to migrate from areas of low salinity to areas of high salinity. fertilizing her eggs with sperm stored from her only mating months or almost a year before. Up to two million eggs may be produced in a single brood, and a single female can produce over 8,000,000 eggs in her lifetime. After brooding the eggs as an orange mass on her pleopods for around two weeks, the female crab releases her eggs in November or December. The crabs hatch into larvae and float in the mouth of the bay for four to five weeks, after which the juvenile crabs make their way back into the bay.

Habitat

The natural predators of ''C. sapidus'' include eels, drum, striped bass, spot, trout, some sharks, humans, and cownose sting rays. ''C. sapidus'' is an omnivore, eating both plants and animals. ''C. sapidus'' typically consumes thin-shelled bivalves, annelids, small fish, plants and nearly any other item it can find, including carrion, other ''C. sapidus'' individuals and animal waste. ''C. sapidus'' may be able to control populations of the invasive green crab, ''Carcinus maenas''; numbers of the two species are negatively correlated, and ''C. maenas'' is not found in the Chesapeake Bay, where ''C. sapidus'' is most frequent.

''Callinectes sapidus'' is subject to a number of diseases and parasites. They include a number of viruses, bacteria, microsporidians, ciliates, and others. The nemertean worm ''Carcinonemertes carcinophila'' commonly parasitizes ''C. sapidus'', espcially females and older crabs, although it has little adverse effect on the crab. A trematode that parasitizes ''C. sapidus'' is itself targeted by the hyperparasite ''Urosporidium crescens''. The most harmful parasites may be the microsporidian ''Ameson michaelis'', the amoeba ''Paramoeba perniciosa'' and the dinoflagellate ''Hematodinium perezi'', which causes "bitter crab disease".