Helminth Taxonomy - Phylum Annelida (Segmented worms)
These are the most highly developed helminths, having segmented bodies, a circulatory system, nephridia (part of a primitive excretory system, but still much more advanced than the flame cells of, for example, the Platyhelminthes), a highly developed digestive system, and a primitive brain. Note that, for these reasons, some authorities do not group the annelids within the Helminths. They are mostly free living (such as the earthworms), but also include some ectoparasites. Only the members of the subclass Hirudinea, (The Leeches) and in particular those in the Order Gnathobdellidae, are of any medical or veterinary interest.
- Taxonomic Classification of the Annelids
Class Polychaetae - The bristle worms. Free living, mostly marine, (e.g. Nereis sp.)
Class Myzostomida - Parasites of the Crinoidea.
Class Clitellata -
Subclass Oligochaeta - Including the earthworms. Free living species (e.g. Lumbricoides sp.).
Subclass Hirudinea - The Leeches. These are ectoparasites, feeding on blood. Some may act as intermediate hosts for protozoan parasites, particularly parasites of fish such as species of trypanosomes.
Order Gnathobdellidae - oral aperture with three toothed jaws.
e.g. Hirudo medicinalis - The 'medicinal' leech
e.g. Limnatis nilotica - The horse leech
Order Rhynchobdellidae - Protrusible proboscis, no jaws.