Crab

Crab, crustacean with 10 pairs of legs, the first pair usually modified as pincers. Crabs start life as small, swimming larvae that look more like lobsters. After molting several times the larva settles on the bottom and becomes an adult crab, with the typical rounded shell protecting the body. Most crabs are marine or live in brackish water, feeding on small animals and carrion that are torn up with the pincers. The smallest is the pea crab, which lives in the shells of bivalve mollusks. The giant crab of the Pacific is a spider crab with a shell measuring over 1 ft (.03 m) across; like all spider crabs, it has very long legs, the record being a 12-ft (4-m) span. Some crabs spend a considerable amount of time out of water. The fiddler crab, with one large, colored claw, lives in holes on mudflats. Robber crabs climb trees but, contrary to belief, do not appear to be able to open coconuts. Hermit crabs, which shelter in the disused shells of mollusks, are a separate group of crustaceans.