Evolution and Medicinal Uses of Leeches


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Recent advances in DNA sequencing and analysis, as well as computational biology have allowed parasitologists such as Dr. Mark Siddall to unravel the mystery of leech evolution. Sequence data suggest that the blood-sucking parasites evolved from harmless freshwater worms which feed on the surface of fish or crustaceans. Gradually, they evolved the characteristics which we now associate with leeches – things such as an appendage which can be inserted into the flesh of their host to suck blood, up to three sets of jaws for clamping on to skin, and chemicals which can thin blood, prevent clotting and suppress inflammation. As you might imagine, pharmaceutical companies are trying to cash in on many of these chemical properties.

Some of the other interesting (and, some would say, bizarre) aspects of leech research revealed in this article include the fact that there is not an effective way to "trap" leeches, and most research samples are acquired by wading in leech-infested water and then plucking the parasites off of bare skin. Another source of one especially large species is the rear end of a hippopotamus, the preferred residence of this particular leech. Leeches can have up to ten “eyespots” on their heads, giving them excellent vision which they use for identifying their targets. The article concludes with a discussion of the medicinal applications of leeches, dating as far back as ancient Rome and as recently as 2004, when the Food and Drug Administration approved them as "medical" devices.


Mark Siddall's website

Website of the American Society of Parasitology