Leeches are annelids comprising the subclass Hirudinea. There are fresh water, terrestrial, and marine leeches. Like their near relatives, the Oligochaeta, they share the presence of a clitellum. Like earthworms, leeches are hermaphrodites. There are 650 known species of leeches. The Hirudo leech has three jaws with 100 teeth on each jaw - making 300 teeth in all. The Medicinal leech, Hirudo medicinalis, which is native to Europe, and its congeners have been used for clinical bloodletting for thousands of years. |