On the Medicinal Leech
We are studying the life cycle, diseases, development and reproduction of these animals under natural and synthetic conditions. We have bred leeches for many years, and know them well. The more a modern person knows about medicinal leeches, the more useful they might be.
Medicinal leeches (Hirudo Medicinalis) are one of numerous representatives of the leech class. They differ from their close relatives in that they feed on warm-blooded animals’ blood. Others feed on fish or reptiles. There are also carnivorous leeches that eat larvae and small (or sometimes even comparatively large) water animals. Medicinal leeches usually attack when their victim is drinking or bathing. Besides, they can drink the blood of frogs, fish, birds.
As the leech sucks, it inserts into the wound the secretion of the salivary glands, which contains over 20 components. It provides for the destruction of microscopic vessels, prevents blood coagulation and blocks bodily defense reactions. It, for example, anesthesizes the wound, which allows the leech to suck enough blood. Since coagulation is prevented, blood usually seeps from the wound for quite some time. The leeches usually stay in the water for a long time without movement, awaiting their victim. They are well equipped for rare feedings – they digest blood very slowly and can go without food for over a year. When full, a leech attempts to hide, as it becomes less active and can become easy prey for natatorial birds, carnivorous fish or animals.
Leeches couple when the weather is warm. They are hermaphrodites, and each possesses both a male and a female reproductive system. Still, two leeches are needed for coupling, as they are not capable of self-fertilization. The fertilized leech lays cocoons with fertilized eggs into the ground. The cocoon contains proteins that provide nourishment for the germs. A month after the laying of cocoons 5 to 20 newborn leeches come out. In about three years they reach a sexually active state.