Crabs are crustaceans. They have a very short tail. A crab's tail is folded under its body. It might not be visible at all, unless you turn the crab around. Usually they have a very hard exoskeleton. This means they are well protected against predators. Crabs are armed with a single pair of claws. Crabs can be found in all the oceans. Some crabs also live in fresh water, or live completely on land[1]. The smallest known crab is the pea crab. Some are only a few millimeters wide. The biggest known crab is the Japanese spider crab. It lives in the Pacific, between 300 and 400 metres deep. The crabs that were found had a leg span of up to 4 metres[2], were up to 37 centimetres large, and had a weight of up to 20 kilograms.
Crabs are omnivores, they eat anything they find. Most often this is algae. It might also be molluscs, other crustaceans, worms, fungi and bacteria[3].
The closest relatives of the crabs are anomurans, a crustacean group which includes animals such as hermit crabs, king crabs and squat lobsters. They look a lot like crabs and many have the word "crab" in their name, but are not true crabs. Anomurans can be told apart by the number of legs: crabs have ten legs, including claws, while the last pair of an anomuran's legs is hidden inside the shell, so that only eight legs are visible.
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