Crustaceans are invertebrate animals that do not possess a backbone, just like spiders and insects. Crustaceans include crabs, lobsters, crayfish, shrimps, water fleas, barnacles and woodlice.

Crustaceans belong to a very large family of creatures called ‘arthropods’ because they have hard jointed limbs and a hard external skeleton (exoskeleton) made out of chitin. This exoskeleton needs to be shed from time to time to allow the animal to grow which is a process called ‘ecdysis’. Most crustaceans have two pairs of antennae and often five pairs of legs. The head and thorax are fused into one piece called a ‘cephalothorax’. The cephalothorax forms a protective sheath over the animal. It is this sheath of ‘crust’ that gives these animals the name ‘crustacean’.

Most crustaceans live in water and breathe through gills. Millions of minute crustaceans (such as copepods) live around the surface of the open sea where they make the principal food for other large animals which are mostly fish.

Other crustaceans live in the deeper layers of the sea, like lobsters and some crabs. Many crustaceans such as sandhoppers, barnacles, shrimps, prawns and some crabs live on coasts and beaches. Others like the White- clawed Crayfish and the Fairy Shrimp live in freshwater. The study of crustaceans is called ‘carcinology’ or ‘crustacelogy’.