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Clitellata (Earthworms and Leeches)
The Clitellata consist of two groups usually treated as separate classes within the Annelida - the Hirudinea (leeches) and the Oligochaeta ("earthworms"), both with many marine taxa. The clitellates have the first segment similar in structure to the rest of the body, with segments lacking parapodia (although chaetae are often present) and the peristomium forming a complete ring.
These worms have elongate cylindrical bodies and differ from polychaetes in lacking appendages (although they have minute chaetae) and a distinct head. While they are best known because of the diverse earthworm fauna, there are also many small freshwater and marine taxa. Marine oligochaetes are particularly abundant in shallow, nutrient-rich sediments.
Marine oligochaetes have been described from Victoria (Erséus 1990a), Darwin (Coates and Stacey 1997; Erséus 1997; Healy and Coates 1997), and south-western Australia (Coates 1990; Erséus 1990b; Coates and Stacey 1993; Erséus 1993).
Erséus (1997) suggested that the genera of tubificids found in the tropics and subtropics are widely distributed in the world, and that endemicity occurs at the specific level. He also suggested that the distribution of genera differs around Australia with the genera present being determined by the available habitats (see the above papers for further discussion). While oligochaetes are present in most coastal habitats they are often not collected by routine benthic surveys using 0.5mm sieves or larger. Far smaller mesh size and other sorting techniques are required to adequately sample this fauna.
Leeches have flattened bodies and a sucker at each end. They lack chaetae or appendages. Leeches live on the land, in freshwater and in the sea, and are parasites on marine vertebrates such as fish and turtles. The marine leech fauna of Australia is poorly known. Dr Gene Burreson, of the Virginian Institute of Marine Sciences, USA is currently working on Australian marine leeches as part of a world revision and has a PEET grant from NSF, he is also collaborating with Dr Ron Davies of the University of Calgary, Canada in preparing a catalogue of Australian leeches for ABRS.
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