Portunidae
Portunidae is a family of crabs distinguished by a flattened, paddle-like final pair of legs in many species, adapted for swimming.
Decapoda: An order of crustaceans with five pairs of walking legs, including crabs, lobsters, and shrimp. Portunidae belongs to this broad group of ten-legged crustaceans.
Swimming crab: A crab adapted for swimming, commonly using flattened rear legs as paddles. This common name describes the locomotor adaptation characteristic of many portunids.
Blue crab: Callinectes sapidus is a large portunid crab native to the western Atlantic and Gulf of Mexico. It is a commercially important member of the family and a familiar example of its swimming ability.
Atlantic rock crab: Cancer irroratus is a crab of the northwestern Atlantic, not a member of Portunidae. It provides a useful comparison with portunid crabs in overlapping coastal habitats.
Brachyura: The infraorder of true crabs, characterized by a reduced abdomen folded beneath the thorax. Swimming crabs are true crabs within this infraorder.
Carcinization: The repeated evolution of a crab-like body form in several crustacean lineages. Portunids have the compact crab form that supports movement and protection.
Asian paddle crab: Charybdis japonica is a portunid crab native to the western Pacific and introduced elsewhere. Its spread beyond its native range illustrates the ecological effects of portunid introductions.
Portunus trituberculatus: A portunid crab native to the northwestern Pacific and a major seafood species in East Asia. Its high-volume aquaculture and fishery use make it a prominent family member.
Crustacean: An arthropod with a segmented body, jointed limbs, and a hard exoskeleton, usually bearing two pairs of antennae. Portunids share the defining body plan of crustaceans.
Crab: A decapod crustacean with a broad body, short abdomen, and usually a pair of claws. Portunidae is one family within the broader diversity of crabs.