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About leeches

There are 300 known leech species divided into 4 orders. The Hirudo medicinalis leech is part of the Hirudinea Class, the Gnathobdellida order. It is an amphibian animal of small or medium size, requiring for its living both soil and water, living exclusively in fresh water.
The medicinal leech has a cylindrical body provided at the extremities with a suction cup, slightly flattened dorsoventral and divided into a number of 33 to 34 segments. The shape of the body varies with the condition of the individual, the muscular contraction or the digestive system filled with blood.
The exertile tube has a strong musculature, and in the bottom of the mouth 3 razor like prominences , disposed in a Y-shape, one anterior and median and two lateral slightly back which are moved by the musculature. Numerous channels of unicellular salivary glands, which produce hirudin, an anticoagulant that prevents clotting of the aspirated blood from the host, are opened among the teeth. Blood is stored in the stomach, separated by strangulations.
The amount of blood drawn into a turn is 5 times greater than its body weight. The size of the leeches varies between 5-14 cm and the weight generally ranges from 1g to 3.5g. It can withstand without food for 18-24 months. When it does not feed it is attached to stones or plants.
Using the suction cups, she can move. It extends the body to the maximum, attaches itself to the cranial suction cup, then releases the caudal suction cup and pulls its body forward. They are sensitive to noises and odors of chemicals. Temperatures influence their life and pace of development.
At temperatures below 15 degrees they enter hibernation.