Having over 17,000 species, Phylum Annelida is a large phylum. Annelids are also known as ringworms or segmented worms. They exist in various environments including marine waters, fresh waters and also in moist terrestrial areas. The size of the annelids can range from a few millimetres to an amazing three metres in length. The Australian earthworm measures around 3 metres. Furthermore some species from this phylum exhibit some unique shapes and brilliant colours.
Annelids exhibit bilateral symmetry and are invertebrate organisms. They are coelomate and triploblastic. The body is segmented which is the most distinguishing feature of annelids.