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The annelids (/ ˈ æ n ə l ɪ d z /), also known as the segmented worms, comprise a large phylum called Annelida (/ ə ˈ n ɛ l ɪ d ə /; from Latin anellus 'little ring'). [3] [a] The phylum contains over 22,000 extant species, including ragworms, earthworms, and leeches.
Phyllodocida are segmented worms and range in size from a few millimetres long to over a metre. Each segment bears a pair of paddle-like parapodia.The prostomium generally has one or two pairs of eyes, a dorsal pair of antennae, a ventral pair of sensory palps and a pair of organs on the neck.
Clitellate annelids are segmented worms characterised by the clitellum or girdle which is located near the head end of mature individuals. The mouth is on the ventral surface and is overhung by the prostomium (proboscis). The brain is not located in the head but in one of the body segments.
Oligochaetes are well-segmented worms and most have a spacious body cavity (coelom) used as a hydroskeleton.They range in length from less than 0.5 mm (0.02 in) up to 2 to 3 metres (6.6 to 9.8 ft) in the 'giant' species such as the giant Gippsland earthworm (Megascolides australis) and the Mekong worm (Amynthas mekongianus).
Worms vary in size from microscopic to over 1 metre (3.3 ft) in length for marine polychaete worms (bristle worms); [1] 6.7 metres (22 ft) for the African giant earthworm, Microchaetus rappi; [2] and 58 metres (190 ft) for the marine nemertean worm (bootlace worm), Lineus longissimus. [3]
For much of the year, these worms look like any other burrow-dwelling polychaete, but as the breeding season approaches, the worm undergoes a remarkable transformation as new, specialized segments begin to grow from its rear end until the worm can be clearly divided into two halves. The front half, the atoke, is asexual.
Leeches are segmented parasitic or predatory worms that comprise the subclass Hirudinea within the phylum Annelida.They are closely related to the oligochaetes, which include the earthworm, and like them have soft, muscular segmented bodies that can lengthen and contract.
Marine worms are known to inhabit many different environments, having been found in both fresh and saltwater habitats globally. [citation needed] Some marine worms are tube worms, of which the giant tube worm lives in waters near underwater volcanoes and can withstand temperatures up to 90 °C (194 °F). They share this space with fellow ...