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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 .
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.
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).
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 ...
In other taxa, there is some evidence of segmentation in some organs, but this segmentation is not pervasive to the full list of organs mentioned above for arthropods and annelids. One might think of the serially repeated units in many Cycloneuralia, or the segmented body armature of the chitons (which is not accompanied by a segmented coelom). [1]
The earthworm, the worms you commonly see after it rains, belongs to the segmented worm family. Des Moines has seen a little more than 2 inches of rain in April, according to the National Weather ...
Annelida, consists of the segmented worms, with bodies divided into segments or rings. Among these worms are the earthworms and the bristle worms of the sea. Familiar worms include the earthworms, members of phylum Annelida. Other invertebrate groups may be called worms, especially colloquially.
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 ...