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European medicinal leech

Hirudo medicinalis

Photo: European medicinal leech
Weights and measures
Length from 100 to 150 mm
State of endangerment
Non Endangered
Animal description
The European medicinal leech, scientifically known as Hirudo medicinalis, is a fascinating species of annelid worm that belongs to the family Hirudinidae. This species has garnered significant attention throughout history for its medical applications, hence the name 'medicinal' in its nomenclature. The European medicinal leech is an intriguing creature, both in terms of its physical characteristics and its ecological and historical significance.

Physically, the European medicinal leech typically measures between 10 to 20 centimeters in length when fully extended, although size can vary. Its body is predominantly dark green or brownish in color, adorned with a series of red or orange stripes and spots, which serve as camouflage in its natural aquatic environments. The body is dorsoventrally flattened and segmented, allowing for flexibility and mobility in water. One of the most distinctive features of Hirudo medicinalis is its possession of two suckers, one at each end of its body. The anterior (front) sucker is used for feeding and attachment to hosts, while the posterior (back) sucker aids in locomotion.

The European medicinal leech has a complex mouth structure that is equipped with three sharp jaws, each lined with numerous tiny teeth. This configuration allows the leech to make a precise Y-shaped incision in the skin of its host. The leech secretes saliva containing a cocktail of bioactive substances, including anticoagulants such as hirudin, local anesthetic compounds, and vasodilators. These substances prevent the host's blood from clotting, reduce pain at the bite site, and increase blood flow, thereby facilitating the leech's feeding process.

Hirudo medicinalis is found in various freshwater environments across Europe and parts of Asia. Its habitats include ponds, marshes, and slow-moving streams, where it preys on the blood of vertebrates, including amphibians, reptiles, waterfowl, and mammals. Despite its parasitic feeding habits, the European medicinal leech is an important component of its ecosystem, contributing to the control of host populations and serving as food for predators.

Historically, the European medicinal leech has been used in medicine for thousands of years. Its application in bloodletting and other therapeutic practices dates back to ancient Egypt and was widely practiced in medieval and early modern medicine. Leech therapy, known as hirudotherapy, has seen a resurgence in modern times for various medical conditions, including venous congestion and microsurgery, owing to its anticoagulant and bloodletting properties.

Despite its medical utility, the population of Hirudo medicinalis has declined significantly due to overharvesting, habitat loss, and pollution. As a result, it is now considered a protected species under various conservation laws and regulations in many countries. Efforts are being made to sustainably manage and conserve this species to ensure its survival and continued availability for medical research and treatments.

In conclusion, the European medicinal leech, Hirudo medicinalis, is a species of considerable interest due to its unique biological features, ecological role, and historical and contemporary medical applications. Its conservation presents a challenge but also an opportunity to balance human medical needs with ecological preservation.
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