Although crabs come in a variety of shapes and sizes they all have the same general body plan.
All crabs have one pair of chelipeds and four pairs of walking legs .
Also referred to as claws, nippers or pincers, the chelipeds are the first pair of legs on a crab and their most distinguishing structure. Chelipeds are used for holding and carrying food, digging, cracking open shells and warning off would be attackers. The carapace is the hard cover or exoskeleton which protects the internal organs of the head, thorax and gills. Visible on the underside of a crab are the mouthparts and the abdomen . The gills through which the animal obtains oxygen cannot be seen.