As of date, more than 650 species of leeches have been identified scientifically. Nearly all people react unusually to the mere mention of leeches. However, to the surprise of all, these crawly creatures are widely-used for medical purposes. In the last few decades, their popularity for medical use has increased significantly. Interesting Facts about Leeches Leeches are brown or black-colored worms having a segmented body (34 segments). They possess a special sucker on both ends. In majority of the species, the mouth encloses three jaws, each equipped with small teeth. Leeches move from one place to another by walking in a looping manner. Classification: Because of their segmented body, leeches are categorized under the phylum Annelida, thus sharing the phylum with earthworms and lugworms. They belong to the class Hirudinea, which is assigned due to the presence of hirudin in their salivary secretions. Thus, they share a lot of annelida characteristics with the other worms belonging to that phylum. Habitat: Leeches prefer to live in warm, swampy areas. You can find them under rocks, in marshy areas, or swimming in shallow lakes and rivers. Many times, they are also found tightly attached to the vegetation and tree trunks of thick forests. It is assumed that one-fifth of leeches are marine and live in the sea. Diet: Some species of leeches are parasitic bloodsuckers, attaching themselves and feeding on the blood of birds, animals, and humans. You can also find scavenger leeches foraging on decaying plants for food. Many are predators that swallow whole earthworms and insects as their diet. Leeches living in the sea feed on small fish and other worms. Adaptability: Unlike other annelids, leeches can tolerate very low percentage of oxygen. Some species are known to survive even when they are exposed to concentrated chemical pollutants. Another interesting leeches fact is that they can survive even after losing nine-tenths of their total body weight. In Medicine: It is the hirudin, an anticoagulant substance present in the saliva of leeches, that is pharmacologically important. Treatment that involves using medicinal leeches is collectively referred to as a hirudotherapy. Almost all species can be used for bloodletting, a method of drawing blood from a patient. Nevertheless, the most popularly used medicinal leech is Hirudo medicinalis, commonly known as European medicinal leech. Previously, in the medieval and early modern period, leeches were frequently used for bloodletting. At present, they are employed to stimulate circulation (particularly in fingers, ears, and eyelids), reduce blood coagulation, and get relief from venous pressure. The therapeutic importance of leeches is steady and continuous blood flow is maintained after their detachment from the skin. Nevertheless, there are also side effects of hirudotherapy such as allergic reactions, infections at the leech attachment site, and excess bleeding. Leeches Bites: Leeches are voracious blood suckers; once coming in contact with human skin, they begin feeding on the blood. It can happen to anyone, during angling on a lake or trekking in a jungle. The tricks to remove leeches are using salt, soap, and insecticidal spray over them. You can also burn them with a lighted match or cigarette. However, the best way is to take hold of one properly and detach it. Quick Facts about Leeches

• The largest leech recorded till date measures about 16 inches in length. On an average, the size of leeches is between 7-80 mm.
• Like earthworms, leeches are hermaphrodites, meaning that a single leech has both male and female sexual organs.
• Leech bite is painless, which is due to the anesthetic present in their saliva secretion.
• Leeches have the ability to feed in large amounts (about 5 times their body weight) and store nutrients for future use.
• Many species can survive for about one year after having a blood meal. They use the preserve food for survival.
• Some species (e.g. hirudo) lay their young ones in cocoons, while others (e.g., Amazon leech) keep their babies (as many as 300) in the stomach.

Commercial rearing of leeches has become a booming industry in recent times with an increasing interest in these creatures for medical purposes. However, it is to be remembered that the hirudo leech is included in the endangered list.