what are crabs

Crabs are crustaceans —usually short-tailed decapod animals with a hard shell, jointed legs, and the ability to move sideways. In everyday speech, “crabs” can also mean pubic lice , which are tiny parasites, so the meaning depends on context.

Quick Scoop

For the animal, crabs live in many environments: oceans, fresh water, and even land in some species. They range from tiny pea crabs to giant spider crabs, and many species are important scavengers or predators in their habitats.

Main Features

• They have a hard outer shell, called an exoskeleton.

• They have ten legs, including claws.

• Many walk sideways, though not all do.

• They molt as they grow, shedding the shell and forming a new one.

Common Types

Type| What it is
---|---
True crabs| The main crab group, called Brachyura. 13
Hermit crabs| Crab-like animals that often use empty shells for protection. 3
King crabs / porcelain crabs| Crab-like forms that evolved a crab shape independently. 1

In Simple Terms

If you mean the animal, a crab is a shell-covered sea or shore creature with claws and a sideways walk. If you mean the health term, “crabs” refers to pubic lice, a parasite that lives on coarse body hair and feeds on blood.

Bottom Line

So, “crabs” can mean either a marine arthropod or a human parasite , depending on the topic. The animal version is the more common meaning in nature and biology.