Leech

Leeches are segmented parasitic or predatory worms that belong to the phylum Annelida. They are closely related to the oligochaetes, which include the earthworm, and like them have soft, muscular, segmented bodies that can lengthen and contract. The majority of leeches live in freshwater habitats, while some species can be found in terrestrial or marine environments. Leeches have been used in medicine from ancient times until the 19th century to draw blood from patients.

About Leech in brief

Summary Leech Leeches are segmented parasitic or predatory worms that belong to the phylum Annelida and comprise the subclass Hirudinea. They are closely related to the oligochaetes, which include the earthworm, and like them have soft, muscular, segmented bodies that can lengthen and contract. The body is muscular and relatively solid, and the coelom, the spacious body cavity found in other annelids, is reduced to small channels. The majority of leeches live in freshwater habitats, while some species can be found in terrestrial or marine environments. Leeches have been used in medicine from ancient times until the 19th century to draw blood from patients. In modern times, leeches find medical use in treatment of joint diseases such as epicondylitis and osteoarthritis, extremity vein diseases, and in microsurgery, while hirudin is used as an anticoagulant drug to treat blood-clotting disorders. Some 680 species of leech have been described, of which around 100 are marine, 480 freshwater and the remainder terrestrial. Among Euhirudinea, the true leeches, the smallest is about 1 cm long, and the largest is the giant Amazonian leech, Haementeria ghilianii, which can reach 30 cm. Except for Antarctica, leech are found throughout the world but are at their most abundant in temperate lakes and ponds in the northern hemisphere.

Some species aestivate during droughts, burying themselves in the sediment, and can lose up to 90% of their bodyweight and still survive. Among the freshwater leeches are the Glossiphoniidae, dorso-ventrally flattened animals mostly parasitic on vertebrates such as turtles. The terrestrial Haemadipsidae are mostly native to the tropics and subtropics, while the aquatic Hirudinidae have a wider global range; both of these feed largely on mammals, including humans. A distinctive family is the Piscicolidae, marine or freshwater ectoparasites chiefly of fish, with cylindrical bodies and usually well-marked, bell-shaped, anterior suckers. The name for the leech group, hirudo, comes from the Latin element -bdella, which means leech; the Greek word for leech is βδάξa, which is also found in many leech species, including the Rhynchobellida and Acanthobellidae. The EuhIRudinea are divided into the proboscis-bearing Rhynobellidae and the Acracobellidea, including some jawed and jawed species, such as the Acacobellids, Acracodidae, Acacododidae and Acracopodidae. In freshwater species, some species are carnivorous and equipped with a relatively large, toothless mouth to ingest insect larvae, molluscs, worms and other invertebrates, which are swallowed whole.