Atlantic Blue Crab

C. sapidus is a decapod crab of the swimming crab family Portunidae. The genus Callinectes is distinguished from other portunid crabs by the lack of an internal cartilaginous spine on the carpus (the middle segment of the claw), as well as by the T-shape of the male abdomen. Blue crabs may grow to a carapace width of 23 cm (9 in). C. sapidus individuals exhibit sexual dimorphism. Males and females are easily distinguished by the shape of the abdomen (known as the "apron") and by color differences in the chelipeds, or claws. The abdomen is long and slender in males, but wide and rounded in mature females. A popular mnemonic is that the male's apron is shaped like the Washington Monument, while the mature female's resembles the dome of the United States Capitol. Claw color differences are more subtle than apron shape. The immovable, fixed finger of the claws in males is blue with red tips, while females have orange coloration with purple tips. A female's abdomen changes as it matures: an immature female has a triangular-shaped abdomen, whereas a mature female's is rounded. Other species of Callinectes may be easily confused with C. sapidus because of overlapping ranges and similar morphology. One species is the lesser blue crab (C. similis). It is found further offshore than the common blue crab, and has a smoother granulated carapace. …

C. sapidus is native to the western edge of the Atlantic Ocean from Cape Cod to Argentina and around the entire coast of the Gulf of Mexico. It has recently been reported north of Cape Cod in the Gulf of Maine, potentially representing a range expansion due to climate change. It has been introduced (via ballast water) to Japanese and European waters, and has been observed in the Baltic, North, Mediterranean, and Black Seas. 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 decreasing as a result of overfishing. In Italy, public awareness of the detrimental impact of this species on local mollusks is rapidly growing and, especially in the Po delta area and on the Adriatic Sea coast, eradication efforts are undergoing, both by local authorities and by local fishermen. In 2023, Italy's Ministry of Agriculture appointed a "commissioner for the blue crab" to coordinate efforts to address the species' spread in Italian waters. Representatives of the agricultural and fishing industries have attributed significant losses in clam fisheries to blue crab predation, with some industry estimates putting the economic damage at up to €100 million since the infestation began.

Some of the natural predators of C. sapidus include eels, drum, striped bass, spot, trout, some sharks, humans, cownose rays, and whiptail stingrays. C. sapidus is an omnivore, eating both plants and animals. It typically consumes thin-shelled bivalves (such as clams, mussels, and oysters), crustaceans, annelids, small fish, plants (such as eelgrass), and nearly any other item it can find, including carrion, other C. sapidus individuals, and animal waste. In salt marshes, C. sapidus will eat marsh periwinkles, Littoraria irrorata during high tides. Although an aquatic predator, C. sapidus will remain in shallow pits in salt marshes at low tide and ambush intertidal prey such as fiddler crabs (e.g., Minuca pugnax) and purple marsh crabs (Sesarma reticulatum) 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 abundant. C. sapidus is subject to a number of diseases and parasites. These include a number of viruses, bacteria, microsporidians, ciliates, and others. The nemertean worm Carcinonemertes carcinophila commonly parasitizes C. sapidus, especially females and older crabs, although it has little adverse effect on the crab. A trematode that parasitizes C. …

The genus name Callinectes comes from Ancient Greek κάλλος (kállos), meaning 'beautiful', and νήκτης (nḗktēs), meaning 'swimmer'. The specific epithet sapidus is Latin for 'savory'. A common name for crabs in Kikitowämank is tuttascuc, used by the Powhatan people, and in Nanticoke, tah'quah.