Leeches are commonly known as a kind of animals that suck blood, and there is fresh water, terrestrial and marine leeches. Scientifically it is categorized as annelids, which is segmented worms comprising the subclass Hirudinea. It is closely related to earthworms, and it is hermaphrodites that have both male and female reproductive organs.
Bodies of all leeches are divided into the same number of segments, with 34 altogether. They have powerful clinging sucker at each end. The mouth is in the anterior sucker and the anus is on the dorsal surface that is just in front of the rear sucker. The mouth of leech has 3 jaws, so the bite by the leeches will show a Y-shape mark.
When leeches bite and feeding with blood, there is a kind of secretion from the body of leech called hirudin will prevent the blood from clotting. Hirudin is a substance that gives valuable usage in medicine. It breathes through the skin by exchange of oxygen from the dissolved gases in the water. It tends to move to the surface when the oxygen content in the water is low.
The head and body surface of leech has the sensory organ to detect change in light intensity, vibration and temperature. It also has the chemical receptors on the head to detect smell. It could have one or more pairs of eyes.
Even though leeches have both male and female sex organs, they still need to mate for reproduction purpose. This involves intertwining of bodies where each deposits sperm in the others' clitellar area. The clitellum secretes a tough gelatinous cocoon that contains nutrients, and this is where the eggs are deposited.
Most leeches are sanguivorous, they suck the blood of the host as food. They can ingest the amount of blood that is several times of their body weight. They can feed on the blood of mammals, frogs, fish and other parasitize. When they bite the host, their saliva contains anti-coagulant will keep the blood continue flowing. The wound will continue bleeding for a few hours even after the leeches detached. The best way to take out the leech when it bites us is by applying some salt or vinegar on to it, this will make it detach immediately. Some people use tobacco leaves to achieve the same purpose.
Leech has got a lot of medical usage be it in pharmaceutical or traditional medicine. Since its population is getting lesser due to the use of insecticide and herbicide, some people start to rear leech to supply to the factories. They are so many benefits that we can get from it and more study is needed to find out how it can help us to improve our health.