THE STUDY OF LIVING THINGS INVERTEBRATES Protozoa One-celled animals, such as amoeba, belong to the protozoa phylum. Protozoa usually live in water - in the sea, in ponds or in damp places like puddles. Coelenterates Coelenterates (pronounced see-elenterates) are animals with soft, hollow bodies and tentacles. Jellyfish, sea anemones and corals are all coelenterates. Annelids Garden worms belong to a phylum called annelids. They have soft bodies, divided into rings or segments. Worms move by relaxing and contracting muscles in their bodies. Arthropods Arthropods have an exoskeleton, jointed legs and antennae. Their bodies are usually divided into three sections - head, thorax and abdomen. There are four main classes of arthropod.   1. Insects Insects have six legs, two pairs of wings, two antennae and two compound eyes. 70% of all animals are insects.   2. Arachnids Scorpions and spiders are arachnids. They have eight legs, no antennae, and simple rather than compound eyes.   3. Myriapods These are arthropods with many legs, such as centipedes and millipedes.   4. Crustaceans They have from 10 to 14 legs, two pairs of antennae and respire by means of gills. Shellfish such as crabs and prawns. Molluscs Soft-bodied animals with a single foot. Snails, slugs and mussels are all molluscs. Echinoderms Spiny-skinned animals, such as starfish and sea urchins.   The information on this site is subject to a disclaimer and a copyright notice