Crabs - Brachyura

Characteristics:

Crabs have a thick armored carapace, usually wider than long, as their major protection. Like other decapods they have ten legs. The two front claws are used to catch prey or pickup scavenges from the sea-floor. They usually have a very short "tail". The abdomen is small or hidden under the body. Males often have larger claws than the females. Crabs vary in size from the tiny pea crab of only a few millimeters to the Japanese spider crab with a leg span of more than 4 meters.

Taxonomy:

The true crabs should not be confused with anomurans like hermit crabs and king crabs, although they are all decapods. There almost 7000 species, mostly marine, but there are about 850 fresh-water and/or terrestrial species.