The following 21 mid-body segments each contain a nerve ganglion, and between them contain two reproductive organs, a single female gonopore and nine pairs of testes. England, 1830–1870.
Your email address will not be published. Among the true leeches, Euhirudinea, the smallest is about 1 cm ( ⁄2 in) long, and the largest is the giant Amazonian leech, Haementeria ghilianii, which can reach 30 cm (12 in). In most species, an albumin-filled cocoon is secreted by the clitellum and receives one or more eggs as it passes over the female gonopore. Pharmacy leech jar with airholes in the lid. , In the proboscisless leeches, the jaws (if any) of Arhynchobdellids are at the front of the mouth, and have three blades set at an angle to each other.  These achieve a wide variety of goals useful to the leech as it feeds, helping to keep the blood in liquid form and increasing blood flow in the affected area. , Leech secretions contain several bioactive substances with anti-inflammatory, anticoagulant and antimicrobial effects. , The leech appears in Proverbs 30:15 as an archetype of insatiable greed.  The Hirudinidae and Erpobdellidae can swim rapidly with up-and-down or sideways undulations of the body; the Glossiphoniidae in contrast are poor swimmers and curl up and fall to the sediment below when disturbed. Another factor has been the replacement of horses in farming (horses were medicinal leeches' preferred food source) and provision of artificial water supplies for cattle. A minority of leech species are predatory, mostly preying on small invertebrates. From these, ducts typically lead to a urinary bladder, which empties to the outside at a nephridiopore. [a] Lithograph by F.-J.-V. Broussais from a cartoon by J. J. Grandville, c. 1832, William Wordsworth's 1802 poem "Resolution and Independence" describes one of the last of the leech-gatherers, people who travelled Britain catching leeches from the wild, and causing a sharp decline in their abundance, though they remain numerous in Romney Marsh.  More generally, a leech is a persistent social parasite or sycophant. Some species aestivate during droughts, burying themselves in the sediment, and can lose up to 90% of their bodyweight and still survive. The bacteria are passed from parent to offspring in the cocoon as it is formed.
 Each cocoon is fixed to a submerged object, or in the case of terrestrial leeches, deposited under a stone or buried in damp soil.  The oldest leech fossils are from the Jurassic period around 150 million years ago, but a fossil with external ring markings found in Wisconsin in the 1980s, with what appears to be a large sucker, seems to extend the group's evolutionary history back to the Silurian, some 437 million years ago. The eggs are enclosed in a cocoon, which in aquatic species is usually attached to an underwater surface; members of one family, Glossiphoniidae, exhibit parental care, the eggs being brooded by the parent. In ancient Greece, bloodletting was practised according to the theory of humours found in the Hippocratic Corpus of the fifth century BC, which maintained that health depended on a balance of the four humours: blood, phlegm, black bile and yellow bile. The leech secretes an anticoagulant, hirudin, in its saliva which prevents the blood from clotting before ingestion.  Not all leeches feed on blood; the Erpobdelliformes, freshwater or amphibious, are carnivorous and equipped with a relatively large, toothless mouth to ingest insect larvae, molluscs, and other annelid worms, which are swallowed whole.  The glossiphoniids brood their eggs, either by attaching the cocoon to the substrate and covering it with their ventral surface, or by securing the cocoon to their ventral surface, and even carrying the newly hatched young to their first meal.
If present in great numbers on a host, these can be debilitating, and in extreme cases, cause death. Both groups are hermaphrodites and have a clitellum, but leeches typically differ from the oligochaetes in having suckers at both ends and in having ring markings that do not correspond with their internal segmentation. , Leeches move using their longitudinal and circular muscles in a modification of the locomotion by peristalsis, self-propulsion by alternately contracting and lengthening parts of the body, seen in other annelids such as earthworms. The Branchiobdellida are sister to the leech clade Hirudinida, which approximately corresponds to the traditional subclass Hirudinea. Such leeches are often ambush predators that lie in wait until they can strike prey with the proboscises in a spear-like fashion.
, The name for the subclass, Hirudinea, comes from the Latin hirudo (genitive hirudinis), a leech; the element -bdella found in many leech group names is from the Greek βδέλλα bdella, also meaning leech. Hi, I'm Tim and I want to welcome you to wanttoknowit.com.  The use of leeches began to become less widespread towards the end of the 19th century. , Leeches live in damp surroundings and in general respire through their body wall. Some 680 species of leech have been described, of which around 100 are marine, 480 freshwater and the remainder terrestrial.
Longitudinal and circular muscles in the body wall are supplemented by diagonal muscles, giving the leech the ability to adopt a large range of body shapes and show great flexibility. The posterior end is attached to the substrate, and the anterior end is projected forward peristaltically by the circular muscles until it touches down, as far as it can reach, and the anterior end is attached.  Medical use of leeches was discussed by Avicenna in The Canon of Medicine (1020s), and by Abd-el-latif al-Baghdadi in the 12th century. If you have a question you can search for the answer below! Devices called "mechanical leeches" that dispense heparin and perform the same function as medicinal leeches have been developed, but they are not yet commercially available. , The bodies of predatory leeches are similar, though instead of a jaw many have a protrusible proboscis, which for most of the time they keep retracted into the mouth. , In 2012 and 2018, Ida Schnell and colleagues trialled the use of Haemadipsa leeches to gather data on the biodiversity of their mammalian hosts in the tropical rainforest of Vietnam, where it is hard to obtain reliable data on rare and cryptic mammals.  An externally attached leech will detach and fall off on its own accord when it is satiated on blood, which may take from twenty minutes to a few hours; bleeding from the wound may continue for some time. , 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. The Asian medical leech is Hirudinaria manillensis, and the North American medical leech is Macrobdella decora. The sperm is liberated and passes to the ovisacs, either through the coelomic channels or interstitially through specialist "target tissue" pathways. I hope you find an answer to your question, but if your don't then please send me your question via email, comment or via Google+ and I'll try and answer it. The majority of leeches live in freshwater habitats, while some species can be found in terrestrial or marine environments. Not all leeches can bite and those that do not bite instead feed on decomposing organisms or open wounds in other animals, such as frogs, fish, birds and mammals. Hirudo medicinalis, the European medicinal leech, is one of several species of leeches used as "medicinal leeches". Their range extends over almost the whole of Europe and into Asia as far as Kazakhstan and Uzbekistan. Except for Antarctica, leeches are found throughout the world but are at their most abundant in temperate lakes and ponds in the northern hemisphere.  In turn, leeches are prey to fish, birds, and invertebrates. Oligochaetes evolved from polychaetes and the leeches branched off from the oligochaetes. Leeches are segmented parasitic or predatory worms that belong to the phylum Annelida and comprise the subclass Hirudinea. Any sickness that caused the subject's skin to become red (e.g. Most leeches have a sucker at both the anterior (front) and posterior (back) ends, but some primitive leeches have a single sucker at the back.
 Leeches were traditionally divided into two infraclasses, the Acanthobdellidea (primitive leeches) and the Euhirudinea (true leeches). Want to Know it? The first description of leech therapy, classified as blood letting, is found in the Sushruta Samhita, an ancient Sanskrit medical text.  Leech usage declined with the demise of humoral theory, but made a small-scale comeback in the 1980s after years of decline, with the advent of microsurgery, where venous congestion can arise due to inefficient venous drainage. It leads successively into the pharynx, a short oesophagus, a crop (in some species), a stomach and a hindgut, which ends at an anus located just above the posterior sucker. , Leeches are unusual in that they do not produce amylases, lipases or endopeptidases. By 1863, British hospitals had switched to imported leeches, some seven million being imported to hospitals in London that year. , Leeches show a remarkable similarity to each other in morphology, very different from typical annelids which are cylindrical with a fluid-filled space, the coelom (body cavity).
What do leeches eat?
A nerve cord runs backwards from this in the ventral coelomic channel, with 21 pairs of ganglia in segments six to 26. The main subdivision of leeches is into the Rhynchobdellida and the Arhynchobdellida, though the Acanthobdella are sister to the clade that contains these two groups. A leech can be removed from the skin by breaking the seal between the leeches sucker and the skin. As a result, this species is now considered near threatened by the IUCN, and European medicinal leeches are legally protected through nearly all of their natural range. The cocoon of Hemibdella soleae is attached to a suitable fish host.
Species that feed on warm-blooded hosts move towards warmer objects. Medicinal leeches have been found to secrete saliva containing about 60 different proteins.  Other clinical applications of medicinal leech therapy include varicose veins, muscle cramps, thrombophlebitis, and osteoarthritis, among many varied conditions. The penis passes a spermatophore into the female gonopore and sperm is transferred to, and probably stored in, the vagina. Hirudin (and related substances) are synthesised using recombinant techniques. , A deficiency of digestive enzymes and of B complex vitamins is compensated for by enzymes and vitamins produced by endosymbiotic microflora. Leeches feed on the blood of other organisms, which is an attribute known as hematophagy or by the common name bloodsucker. Leeches are best known for attaching themselves to their food, including humans, with their strong jaws. A recorded use of leeches in medicine was also found during 200 B.C.  Other clinical applications include varicose veins, muscle cramps, thrombophlebitis, and joint diseases such as epicondylitis and osteoarthritis. Of these segments, the first five are designated as the head and include the anterior brain, several ocelli (eyespots) dorsally and the sucker ventrally. Some marine species however remain attached until it is time to reproduce. Most species of leeches eat small invertebrates, such as insects, and these are commonly eaten whole.
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