Crabs

This group gathers Crustaceans subcategory members belonging to the true crabs, decapod crustaceans of the infraorder Brachyura, recognizable by a short, broad, rounded body carried tucked beneath the shell and, in most species, a tail folded flat against the underside rather than extended behind the animal as in a lobster or shrimp. Crabs walk and swim sideways more often than forward, a gait shaped by legs that hinge most freely in that direction, and use a pair of pincer-like claws, often unequal in size, for feeding, defense and, in male fiddler crabs, an oversized signaling display used to attract mates and warn off rivals. Found in oceans worldwide from the intertidal zone to the deep sea, and in freshwater and terrestrial habitats too, crabs range from tiny pea crabs living inside the shells of other animals to the Japanese spider crab, whose leg span can exceed three meters, the largest of any living arthropod.