Crab

A crab is a sea animal with a hard shell, ten legs, and two claws. Crabs belong to a group of animals called crustaceans, which also includes lobsters and shrimp. Most crabs live in the ocean, but some live in rivers, some live on land, and a few even climb trees. Scientists have named more than 6,000 different kinds of crabs.

A crab's body is covered by a hard shell called a carapace. The shell protects the soft body inside like a suit of armor. A crab has ten legs in total. The front two legs end in claws, called pincers. Crabs use their pincers to grab food, fight other crabs, and defend themselves. The other eight legs are used for walking. Most crabs walk sideways because of how their leg joints bend.

Crabs eat almost anything. They munch on small fish, worms, clams, dead animals, and bits of plants. This makes them important cleaners of the ocean floor. A crab's eyes sit on short stalks and can turn in different directions. Its mouth has several small parts that tear food into tiny pieces before eating.

Crabs have one problem: they cannot grow bigger inside a hard shell. So they molt. The crab splits open its old shell and wriggles out. Underneath is a new, soft shell that has been forming. Over the next few hours, the new shell hardens. During this time, the crab hides, because it has no armor and almost anything can eat it. A crab may molt dozens of times during its life.

Crabs come in amazing sizes. The pea crab is smaller than a fingernail. The Japanese spider crab, the giant of the group, can stretch 12 feet from claw to claw. That is wider than most cars are long. The coconut crab, which lives on tropical islands, can crack open coconuts with its claws and climbs trees to reach them.

People have eaten crabs for thousands of years. Blue crabs, Dungeness crabs, king crabs, and snow crabs are popular foods in many countries. Crab fishing is a huge industry, but catching too many crabs can hurt their numbers. Many places now have rules about how many crabs can be caught and how big they must be.

The next time you walk along a beach, look closely at the wet sand. The small holes you see may be crabs, watching the world go by from inside their tunnels.