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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 .
The first body segment (segment number 1) features both the earthworm's mouth and, overhanging the mouth, a fleshy lobe called the prostomium, which seals the entrance when the worm is at rest, but is also used to feel and chemically sense the worm's surroundings. Some species of earthworm can even use the prehensile prostomium to grab and drag ...
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.
Polychaeta (/ ˌ p ɒ l ɪ ˈ k iː t ə /) is a paraphyletic [1] class of generally marine annelid worms, commonly called bristle worms or polychaetes (/ ˈ p ɒ l ɪ ˌ k iː t s /). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. More than 10,000 species ...
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).
Leech anatomy in cross-section: the body is solid, the coelom (body cavity) reduced to channels, with circular, longitudinal, and transverse muscles making the animal strong and flexible. [ 26 ] Like most annelids, with a few exceptions like Sipuncula , Echiura and Diurodrilus , [ 27 ] the leech is a segmented animal, but unlike other annelids ...
Earthworms are a classic example of biological homonymous metamery – the property of repeating body segments with distinct regions. In biology, metamerism is the phenomenon of having a linear series of body segments fundamentally similar in structure, though not all such structures are entirely alike in any single life form because some of them perform special functions. [1]
This segmented worm is long and slender. For example, a worm with 110 segments was 55 mm (2.2 in) in length and 1.6 mm (0.06 in) in width, exclusive of appendages. The prostomium (head) has a single tentacle ventrally. Behind the head are two long palps which can be extended forward, or coiled loosely, and which may be half the length of the body.