Crustaceans have a hard, jointed external skeleton, called an exoskeleton, that protects them like armour. They have five pairs of jointed legs, and in some species, the front pair of legs are modified to form strong pincers. Crustaceans have compound eyes (made up of lots of lenses) on stalks and two pairs of antennae, which help them to sense predators. Most crustaceans live in water, but some, such as woodlice, live in damp places on land.
Most crustaceans live in water. There are more than 45,000 species in seven classes, including:
(fairy shrimps, water fleas)
Features: small, free-living, filter feeders with bristled mouthparts