Leech

:This page is about the blood sucking animal leech. For other uses, see Leech (disambiguation).

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Arhynchobdellida or

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Rhynchobdellida

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There is some dispute as to whether Hirudinea should be a class itself, or a subclass of the Clitellata.

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The leeches are annelids comprising the subclass Hirudinea. There are freshwater, terrestrial and marine leeches. Like their near relatives, the Oligochaeta, they share the presence of a clitellum. Many species of leech are haemophagic parasites, living on occasional meals of blood obtained by attaching themselves to fish, amphibians (frogs etc.), and mammals. The medicinal leech, Hirudo medicinalis, which is native to Europe, has been used for clinical bloodletting for thousands of years. Most leech species are predators and feed on small worms or other invertebrates.

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The leeches are clitellate when breeding and are derived from some oligochaete ancestor. They attach to their hosts and remain there until they become full, at which point they fall off to digest. Leeches' bodies are composed of 34 segments. They all have a ventral sucker formed from the last six segments of their body, which is used to connect to a host for feeding. They use a combination of mucus and suction (caused by concentric muscles in those six segments) to stay attached. Like earthworms, leeches are hermaphrodites.

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Some species of leech will nurture their young, providing food, transport, and protection, which is unusual behavior in an invertebrate.http://www.enn.com/news/2004-08-10/s_25691.asp

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Oligochaeta: : For the plant genus Oligochaeta from the sunflower family (Asteraceae): see Oligochaeta (plant)...

Clitellum: In earth worms and other annelids, the Clitellum is a thickened glandular section of the body wall that secretes a viscid sac in which the eggs are deposited. Once the eggs have been deposited in the sac, the clitellum slides off of the earthworm's (annelid's) body. The clitellum also secretes muco...

Haemophagic: redirect hematophagy...