The T. rex and other bloodsucking leeches

leeches

There are between 700 and 1,000 species of leeches throughout the world.  Most prey on insects, snails and other small creatures.  Some swallow their prey whole.  Others have an extendible proboscis, which they use to spear their prey and suck up their juices.

And then there are the “bloodsuckers.”  These sanguivorous (blood-feeding) leeches feed on fish, reptiles, waterfowl, small mammals, earthworms (their closest biological relatives) and, yes — humans.  Sanguivorous leeches generally have either two or three jaws, which contain small teeth or a sharp cutting edge.  A bite from a two-jawed leech leaves a V-shaped bite, while that of the three-jawed variety results in a Y-shaped one.

In 2010, however, scientists working in the remote Peruvian Amazon discovered a new single-jawed species of leech.  They dubbed itTyrannobdella rex (tyrant leech king), and not just because it can grow up to three-inches long.  The T. rex also has large teeth, which it uses to saw into the tissues of mammals’ orifices – including eyes, noses, urethras, rectums, and vaginas.  While this generally isn’t deadly, the T. rex can stay in the body for weeks, possibly presenting a choking (not to mention a freak-out) hazard.

t-rex-leech-face_18988_600x450

Tyrannobdella rex (tyrant leech king)

The good news is that leech bites aren’t terribly painful.  When it bites, the leech releases an anesthetic enzyme, which numbs the skin.  Leech saliva also contains the anti-coagulant hirudin, which keeps the blood from clotting so the leech can keep sucking down its food.  After a full meal, a leech can expand to as much as 10 times its normal weight.  Some may not need to eat again for up to a year.  But even after the leech is detached, the host will continue to bleed for up to 48 hours.  And it is this property that has made the leech so valuable in medicine.

By some estimates, leeches have been used for therapeutic purposes since 3500 BCE. One of the earliest depictions comes from a 16th century BCE mural painting from a tomb from the 18th dynasty in Thebes (Egypt).  It shows a nurse applying leeches to a patient’s forehead.  The first written reference dates from the second century BCE and deals with the treatment of poisonous bites. The use of leeches in antiquity is likewise well-documented.  The 1st century Roman naturalist Pliny the Elder recommended them for the treatment of phlebitis and hemorrhoids.

During the Dark Ages, leeches were used to treat cervical lacerations. And from the Middle Ages right on through the Classical period, leeches conditioned to be used for conditions as varied as laryngitis, ophthalmic problems, cerebral apoplexy, obesity, and mental disorders. By the time leeching fell into disuse in the 19th century, however, French marshland had become depopulated, and Hirudo medicinalis – the leech most commonly used in medicine — was extinct in many parts of its range.

Recently, however, the leech has been making a comeback, especially in reconstructive surgery to reattach severed fingers, toes, ears and nasal tips.  Pharmaceutical companies, too, are interested in leeches as they search for anticoagulants to prevent blood clotting during microsurgery.  And new salivary compounds from leeches are constantly being isolated and synthesized.

So who knows?  Someday a T. rex might crawl up your nose and camp there for a week.  Or it just might save your life.

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