• 1 Origin
• 2 Taxonomy
• 3 Use of Hirudo medicinalis in medicine
• 4 The anatomy of medicinal leeches
• 5 Reproduction
• 6 Nutrition of leeches
• 7 The effects of leech bites
• 8 Removal and Treatment
• 9 Prevention
• 10 References
• 11 External links

Origin

The leeches are presumed to have evolved from the Oligochaeta, most of which feed on detritus. However, some species in the Lumbriculidae are predaceous and have similar adaptations to the leeches.

Taxonomy

True leeches, of the subclass Euhirudinea, with both anterior and posterior suckers, are divided into two groups:

Use of Hirudo medicinalis in medicine

The leech has long been used in medicine, although today its use is mainly limited to limb reattachment procedures instead of the wide-ranging medical use of the past. The word leech either comes directly from or was influenced by the Old English word for "physician", lǣce, which is related to Old High German lāhhi and Old Irish liaig.

The anatomy of medicinal leeches

The anatomy of medicinal leeches may look simple, but more details are found beyond the macro level. Externally, medicinal leeches tend to have a brown and red striped design on an olive colored background. These organisms have two suckers, one at each end, called the anterior and posterior sucker. The posterior is mainly used for leverage while the anterior sucker, consisting of the jaw 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 incise the host.

Reproduction

Leeches are hermaphrodites, meaning they are organisms that have both female, ovary, and male, testes, sexual reproductive organs.

Nutrition of leeches

Starting from the anterior sucker is the jaw, the Pharynx which extends to the crop, which leads to the Intestinum, where it ends at the posterior sucker. The crop is a type of stomach that works like an expandable storage compartment. The crop allows a leech to store blood up to five times its body size; because of this ability to hold blood without the blood decaying, due to bacteria living inside the crop, medicinal leeches only need to feed two times a year.

The effects of leech bites

A Leech attaches itself when it bites, and it will stay attached until it has had its fill of blood. Due to an anticoagulant (hirudin) that leeches secrete, bites may bleed more than a normal wound after the leech is removed. The effect of the anticoagulant will wear off several hours after the leech is removed and the wound is cleaned. The amount of blood loss from a leech bite is more of a nuisance than a danger for humans.

Removal and Treatment

Many people believe that it is best not to remove a leech but to wait for the leech to have its fill and detach itself. This does prevent the risk of additional damage or complications from removal, but concerns about leaving portions of the leeches sucker attached to the wound are exaggerated. It is generally considered preferable to remove the leech promptly.

Prevention

There is no guaranteed method of preventing leech bites in leech-infested areas. The most reliable method is to cover exposed skin. The effect of insect repellents is disputed, but it is generally accepted that strong (maximum strength or tropical) insect repellents do help prevent bites.

References

• Sawyer, Roy T. 1986. Leech Biology and Behaviour. Vol 1-2. Clarendon Press, Oxford