This freshwater class of annelids is commonly called leeches. An example of a leech is Hirudo.

Leeches have no setae or parapodia and they have anterior and posterior suckers for attachment.

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Leech (Hirudo Medicinalis)

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Although leeches have a reputation as being blood suckers from vertebrate hosts, most are predacious.

Mouth's of blood-sucking leeches with chitinous teeth and secrete anticoagulant

Leeches have been used traditionally in the medicine since they can alleviate the accumulation of blood around a muscle after operations.