Crab any of the members of decapod crustaceans belonging to the suborder Brachyura with a broad, rather round, upper carapace and a small abdomen tucked beneath the body living in marine, brackish, or freshwaters. Though they differ from species to species in size, shape, colour and structure, they closely resemble each other in general morphology and biology. Sixteen species of crabs have been so far reported from Bangladesh waters, of which the common ones are Scylla serrata, Portunas pelagicus, P. sanguinolentus, Charybdis feriata, Charybdis rostrata, Matuta lunaris, M. planipes, Clappa lophos, C. pustulosa, Varuna litterata, Sartorina spinigera, Ocypoda cratopthalma, and Gelasimus annulipes. The six important genera used as food crabs are Scylla, Portunus, Charybdis, Matuta, Varuna and Sartorina.
