From: itannman@boris.ucdavis.edu (Ann Mansker) Subject: Critter of the Week: Hirudo medicinalis Date: 1999/03/09 Newsgroups: ucd.life The European Medicinal Leech (Hirudo medicinalis) was once found throughout Europe and the British Isles, but is now endangered in the wild due to overcollection and habitat destruction. There are only 20 small natural populations left in the UK, where it is protected. As a species, however, the medicinal leech is far from endangerd, as it is useful both medically and in neurological research. H. medicinalis is primarily aquatic, swimming with a graceful undulation, but it lays its cocoon of eggs on land at the water's edge. On land, it moves with a looping motion like an inchworm. Wild leeches feed rarely, surviving for six months or more on a single meal. They manage this by eliminating most of the water from the blood they acquire, then storing the remainder in pockets in their gut. They secrete a powerful anticoagulant, hirudin, which keeps the stored blood liquid, while a particular bacterium in their gut acts as a preservative. They typically feed on pond fauna, but will willingly take contributions from warm-blooded passers-by as well, attaching with a sucker at each end and biting a y-shaped wound with their 3 toothy jaws. Though medical technology has advanced considerably since barbers treated a variety of ills with bloodletting, the use of medicinal leeches is coming back into favor for relief of blood congestion in plastic surgery and reattachment of severed extremities. They are used when arterial flow to an area is good, but the venous return that should drain deoxygenated blood is disrupted. Though the leech itself provides immediate reduction of swelling by removing 15 to 30ml of blood, its most important contribution is the injection of hirudin that keeps the wound seeping for another 10 hours on average. European medicinal leeches are dark brown to black, with several stripes running nose-to-tail: http://www2.hmc.edu/www_common/biology/florafauna/leeches.html