Cancer magister

The Dungeness crab, Metacarcinus magister (the naming convention recognised by WoRMS) or Cancer magister (the naming convention recognised by ITIS), is a species of crab that inhabits eelgrass beds and water bottoms on the west coast of North America. It typically grows to 20 cm (7.9 in) across the carapace and is a popular seafood prized for its sweet, moist and tender flesh. Its common name comes from the port of Dungeness, Washington. The carapace widths of mature Dungeness crabs may reach 25 centimetres (9.8 in) in some areas off the coast of Washington, but are typically under 20 cm (7.9 in). They are a popular delicacy, and are the most commercially important crab in the Pacific Northwest, as well as the western states generally. The annual Dungeness Crab and Seafood Festival is held in Port Angeles, Washington each October. Dungeness crabs have a wide, long, hard shell, which they must periodically moult to grow; this process is called ecdysis. They have five pairs of legs, which are similarly armoured, the foremost pair of which ends in claws the crab uses both as defense and to tear apart large food items. The crab uses its smaller appendages to pass the food particles into its mouth. Once inside the crab's stomach, food is further digested by the 'gastric mill', a collection of tooth-like structures. M. magister prefers to eat clams, other crustaceans and small fish, but is also an effective scavenger. Dungeness crabs can bury themselves completely in the sand if threatened. Mature female crabs generally molt between May and August, and mating occurs immediately after the female has molted and before the new exoskeleton hardens. Males are attracted to potential mates by pheromones present in the urine of females. Upon locating an available female, the male initiates a protective premating embrace that lasts for several days. In this embrace, the female is tucked underneath the male, oriented such that their abdomens touch and their heads face each other. Mating occurs only after the female has molted, and the female signals her readiness to molt by urinating on or near the antennae of the male. The female extrudes the eggs from her body several months later; however, they remain attached under her abdomen for three to five months until they hatch. Young crabs are free-swimming after hatching, and go through five larval stages before reaching maturity after about 10 molts or two years. Juvenile crabs develop in eelgrass beds and estuaries where salinity levels tend to be low. The hyposaline conditions of the estuaries are lethal to some of the crab's symbionts, such as Carcinonemertes errans which consumes a brooding female's live eggs. Dungeness crabs surveyed in Coos Bay were less likely to be infected by C. errans and have fewer worms present on their carapace when inhabiting less saline waters farther inland. The Dungeness crab is named after Dungeness, Washington, which is located approximately 5 miles (8.0 km) north of Sequim and 15 miles (24 km) east of Port Angeles. Its typical range extends from Alaska's Aleutian Islands to Point Conception, near Santa Barbara, California, while it is occasionally found as far south as Magdalena Bay, Baja California Sur, Mexico. A genetic analysis of adult Dungeness crabs indicated that there is one population across the California Current System, but it is likely that interannual variation in physical oceanographic conditions (such as ocean circulation patterns) influence larval recruitment among regions, causing genetic diversity to change through time. Dungeness crabs have recently been found in the Atlantic Ocean, far from their known range, raising concern about their possible effects on the local wildlife.