Leech (Medicinal) / Hirudo verbena

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A medicinal leech can go a year between meals Leeches were first used in Medicine in 1000 BC, probably in India An average meal consists of 5-15 ml of blood. Large adult leeches can consume 10 times their body weight in a single meal.

The 650 or more species of leech, belong in the Phylum Annelida meaning they are in the same group of animals as earthworms and segmented marine worms like ragworms. The medicinal leech has a body divided in to 33 – 34 segments with two suckers, one at each end, called the anterior and posterior suckers. It is found in small pools with muddy bottoms and surrounded by reeds where it feeds on the blood and tissue of a wide range of animals such as fish, amphibians and mammals.

The posterior sucker of the leech is used mainly for attaching itself to substrates and in moving whilst the anterior sucker, consisting of the jaws and teeth, is where the feeding takes place. Medicinal leeches have three jaws that look like little saws, and on them are about 100 sharp teeth used to pierce the hosts skin.. The incision leaves a mark that is an inverted Y inside of a circle. After piercing the skin and injecting an anticoagulant (hirudin) and anaesthetics, they suck out the blood on which they feed..

Medicinal leeches are hermaphrodites (each animal contains male and female reproductive organs) that reproduce by sexual mating, each animal laying eggs in clutches of up to 50 near (but not under) water, and in shaded, humid places.

In mediaeval and early modern medicine, the medicinal leech was used to remove blood from a patient. Sicknesses that caused the subject’s skin to become red (e.g. fever and inflammation), were thought to have arisen from too much blood in the body and so it had to be removed by leeching. Similarly, any person whose behaviour was hyperactive was also thought to be suffering from an excess of blood.

Today thousands of leeches are used for medical emergencies every year. The leech’s blood sucking accelerates healing on any deep wound but especially after re-attaching a severed limb or any other deep wound. The leech feeds off the oxygenated blood that would otherwise cause swelling and gangrene. The sucking assists the flow of blood and an anticoagulant in the leech prevents scabbing. The sucking is painless because the leech also releases an anaesthetic.