Annelids are any of the roughly 9,000 segmented worms that make up the Phylum Annelida. Only a few species are known to the average person. These include dew, rain and earthworms commonly found in the soil, lugworms used by fisherman, and smaller redworms used to feed aquarium fish and leeches.
The bodies of annelids are bilaterally symmetrical and contain three separate sections: a prosomium, a trunk and a pygidium. Annelids have a true, closed circulatory system and lack true respiratory organs. Found almost everywhere in the world, the segmented worms have existed on Earth for at least 120 million years.