Segmented worms: Leeches

Code LH000000

Hirudinea (leeches) are annelid worms. The body is internally segmented and the body surface is annulated. There is a small sucker at the anterior and a larger sucker at the posterior end of the body. Movement is generally by looping.

Some of the smaller aquatic leeches may rather easily be mistaken for flatworms. Some ectoparasitic flatworms have anterior and/or posterior adhesive zones or suckers and could well be mistaken for leeches. Flatworms are not annulated or internally segmented and do not possess the closed circulatory system and ganglionated ventral nerve cord of the leech.

Leeches occur in marine, terrestrial and freshwater habitats. Five families of freshwater leeches are recorded in Australia. The Key to Platyhelminthes (Flatworms) and Allied Forms gives further detail.