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The annelids (/ ˈ æ n ə l ɪ d z /), also known as the segmented worms, are animals that comprise the phylum 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 ...
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 ...
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).
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 ...
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.
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.
Earthworm with clitellum lablelled. Close-up of the clitellum of a Lumbricus rubellus The clitellum is a thickened glandular and non-segmented section of the body wall near the head in earthworms and leeches that secretes a viscid sac in which eggs are stored. [ 1 ]