The annelids are a large phylum of over 17,000 ringed worm species including ragworms, earthworms, and leeches. They are bilaterally symmetrical, have a true coelom body cavity, and possess a through gut with mouth and anus. Annelids exist in a variety of marine, freshwater, and terrestrial environments and can be distinguished by their segmented bodies and trochophore larva stage of indirect development. Examples of annelid classes include polychaetes, which have multiple hairs and parapodia limbs, as well as clitellates like oligochaetes including earthworms and hirudinea including leeches.