European medicinal leech
General information
The European medicinal leech (Hirudo medicinalis) is one of the UK’s most remarkable invertebrates and the only one of the country’s 21 leech species with jaws strong enough to feed on the blood of mammals, so there’s no need to worry about the others. These fascinating animals have 34 body segments and five pairs of eyes, and each segment contains a small cluster of nerve cells often described as a “mini brain,” helping the leech move and sense its surroundings with surprising precision. To feed, they use three powerful jaws lined with around 100 tiny teeth to latch onto a host, while releasing a natural anticoagulant called hirudin that prevents the blood from clotting. Because a single meal is so substantial, a medicinal leech may not need to feed again for 12–18 months, making it an extraordinary example of adaptation and survival.
Medicinal leeches have been used by humans since the time of the ancient Egyptians, although their use only became widespread in Britain during the Middle Ages. Even today, they still play an important role in modern medicine, where they are used to encourage blood flow during reconstructive and reattachment surgery, improve circulation to damaged tissue, and have even been studied for their pain-relieving properties.
Latin name - Hirudo Medicinalis.
Class - Clitellata.
Order - Arhynchobdellida.
Family - Mustelidae.
IUCN Status - Near threatened.
Habitat - Ponds, lakes and small pools.
Distribution - Across much of Europe and into Asia.
Average Lifespan
Up to 20 years in captivity.
Threats
Collection from the wild for the medical trade over the years has caused the leech population across Europe to become fragmented and go locally extinct in many regions. In the UK it is restricted to only 20 isolated populations and fully extinct in Ireland, one of these populations being in the new forest.
Pollution and drainage of waterways has restricted the leeches habitat
Habitat loss fragmentation caused by urbanisation and farming.
Decline of amphibian populations reduces food sources and the use of various veterinary medication in livestock can poison leeches.
Fun fact
There is a similar looking species of leech in the UK known as the horse leech. This species however cannot suck the blood of mammals and instead feeds off mainly amphibian blood. The name is thought to derive from an old English version of the word false, as these would be sold to doctors as medicinal leeches but would obviously not suck blood. This word is also where the name for the horse chestnut comes from, as horse chestnuts cannot be eaten like the sweet chestnut!
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