Leeches (Latin: Hirudinea) are a subclass of annelid worms in the class Clitellata. Most representatives live in fresh water bodies. Some species have mastered terrestrial and marine biotopes. About 500 species of leeches are known, and 62 species are found in Russia.[1]
Content
1 Etymology
2 Structure
3 Nutrition
4 Movement
5 Reproduction and life cycle
6 Hirudotherapy
7 Biology of the organism
8 History of medical use
9 Notes
10 Literature
Etymology
The Russian word "leech" goes back to proto-Slavic * pjavka (cf. Czech. pijavka, Polish: pijawka), formed from the verb *pijati, a verb of the multiple form from *piti "to drink". At the same time, in Russian the form *pyavka (cf. Ukr. p'yavka), and the letter and in this case are explained by a secondary convergence with the verb "to drink" according to folk etymology.
In Latin hirūdō, the same suffix is found as in testūdō "turtle", but the etymology of the root causes difficulties. Possible relatives include hīra "small intestine" and haruspex "garuspik".
Structure
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Hirudo medicinalis anatomy by Syme.png
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The body length of different representatives varies from a few millimeters to tens of centimeters. The largest representative is Haementeria ghilianii (up to 45 cm).
The front and back ends of the leech body are carried by suckers. The anterior is formed by the fusion of 4-5 segments, the posterior - 7, and therefore it is more powerful, the anus is located above the posterior suction cup. The parenchyma predominates in the body cavity. It forms tubules - the remains of the whole (secondary body cavity) - lacunae. The circulatory system is mainly reduced, its role is performed by the lacunar system of coelomic tubules. The skin forms a cuticle, devoid of parapodia and generally bristles. The nervous system is similar to the nervous system of small-bristle worms. At the bottom of the front suction cup is the mouth opening leading into the pharynx. In proboscis leeches (order Rhynchobdellida), the pharynx is able to extend outward. In jaw leeches (for example, a medical leech), the oral cavity is armed with three mobile chitinous jaws that serve to cut through the skin. Basically, leeches have up to 400 teeth. Respiration in most species occurs through the integuments of the body, but some species have gills. The excretory organs are metanephridia.
Nutrition
Leeches feed on the blood of vertebrates, mollusks, worms, etc., there are also predatory species that do not feed on blood, but swallow prey whole (for example, mosquito larva, earthworm).
There are types of leeches that eat other food. For example, some eat the blood of amphibians and plant foods.
Movement
An interesting way of movement of leeches: at both ends of the leech's body there are suckers with which it can attach to underwater objects. The leech is attached to them with the front end and, bending into an arc, moves.
Leeches can swim, undulatingly bending the body.
Reproduction and life cycle
Leeches are hermaphrodites. Two individuals are involved in copulation, secreting seed material. Before laying eggs, a specialized part of the worm's integuments - the girdle - separates the mucous cocoon containing the albumin protein. During the discharge from the body of the worm into the cocoon, fertilized eggs enter from the female genital opening. In the future, the mucous tube closes and forms a shell that protects the embryos and subsequently young worms. Albumin acts as a food source.
Hirudotherapy
Main article: Hirudotherapy
Hirudotherapy - treatment with leeches. A sucked leech causes local capillary bleeding, which can eliminate venous congestion, increase blood supply to a part of the body, in addition, substances that have an analgesic and anti-inflammatory effect enter the bloodstream. As a result, blood microcirculation improves, the likelihood of thrombosis decreases, edema subsides. A reflexogenic effect is assumed.
In medical practice, the leech after use is removed by applying an alcohol swab to its head end. Getting rid of an unwanted leech is quite simple - you need to pour a little salt on the suction cup.
It should also be noted that leeches, attacking a person, cause hirudinosis. Typically, leeches leave their prey at the moment of saturation, which can take anywhere from 40 minutes to several hours.
Biology of the organism
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The body is elongated or oval, more or less flattened in the dorso-abdominal direction, clearly divided into small rings, which in number 3-5 correspond to one body segment; in the skin there are numerous glands that secrete mucus; at the posterior end of the body there is usually a large suction cup, often at the front end there is a well-developed suction cup, in the center of which the mouth is placed; more often, the mouth serves for suction. At the anterior end of the body there are 1-5 pairs of eyes, arranged in an arc or pairwise one after another. Powder on the dorsal side above the posterior suction cup.
The nervous system consists of a two-lobed suprapharyngeal ganglion, or brain, connected to it by short commissures of the subpharyngeal node (originating from several fused nodes of the abdominal chain) and the abdominal chain itself, which fits in the abdominal blood sinus and has about 32 nodes. The head node innervates the sense organs and pharynx, and 2 pairs of nerves depart from each node of the abdominal chain, innervating their corresponding body segments; the lower wall of the intestine is equipped with a special longitudinal nerve that gives branches to the blind sacs of the intestine.
The digestive organs begin to serve to cut through the skin when sucking blood in animals with a mouth, or armed with three chitinous toothed plates (jaw leeches - Gnathobdellidae), or a proboscis capable of protruding (in proboscis leeches - Rhynchobdellidae); numerous salivary glands open in the oral cavity, sometimes secreting a poisonous secretion; the pharynx, which plays the role of a pump when sucking, is followed by an extensive strongly stretched stomach, equipped with side sacs (up to 11 pairs), of which the posterior ones are the longest; the hindgut is thin and short.
The circulatory system consists partly of real, pulsating, vessels, partly of cavities - sinuses, which are a remnant of the secondary body cavity and are interconnected by ring channels; the blood in proboscis leeches is colorless, in jaw leeches - red due to hemoglobin dissolved in the lymph.
Special respiratory organs are available only in representatives of the genus Branchellion, in the form of leaf-shaped appendages on the sides of the body.
The excretory organs are arranged according to the type of metanephridia, or segmental organs of annelid worms, and most leeches have a pair of them in each of the middle segments of the body.
Leeches are hermaphrodites: the male genital organs consist in most of the vesicles (testes), a pair in 6-12 middle segments of the body, connected on each side of the body by a common excretory duct; these ducts open outward with a single opening lying on the ventral side of one of the anterior rings of the body; the female genital opening lies one segment behind the male and leads into two separate oviducts with sac-like ovaries. Two individuals copulate, each simultaneously playing the role of a female and a male. Leech during egg laying secretes glands lying in the genital area, thick mucus surrounding the middle part of the body in the form of a cover; eggs are laid in this cover, after which the leech crawls out of it, and the edges of its holes are brought closer, glued together and thus form a capsule with eggs inside, attached usually to the lower surface of the algae leaf; embryos, leaving the facial membrane, sometimes (Clepsine) for some time stay on the underside of the mother's body.
All leeches lead a predatory lifestyle, feeding on the blood of mostly warm-blooded animals or mollusks, worms, etc.
They live mainly in fresh waters or in wet grass, but there are also marine forms (Pontobdella), just like terrestrial forms (in Ceylon).
Hirudo medicinalis - medical leech, up to 10 cm in length and 2 cm in width, black-brown, black-green, with a longitudinal patterned reddish pattern on the back; the belly is light grey, with 5 pairs of eyes on 3, 5 and 8 rings and strong jaws; it is distributed in the swamps of southern Europe, southern Russia and the Caucasus.
In Mexico, Haementaria officinalis is used in medicine; the other species, N. mexicana, is poisonous; in tropical Asia, Hirudo ceylonica and other related species living in humid forests and grass are common, causing painful bleeding bites to humans and animals.
Nephelis vulgaris - a small leech with a thin narrow body, gray in color, sometimes with a brown pattern on the back; equipped with 8 eyes, located in an arc at the head end of the body; related to it is the original Archaeobdella Esmonti, pink in color, without a rear suction cup; lives on silt bottom in the Caspian and Azov Seas.
Clepsine tessel ata - Tatar leech, with a broad-oval body, greenish-brown in color, with several rows of warts on the back and 6 pairs of triangular eyes, located one after another; lives in the Caucasus and the Crimea, where it is used by the Tatars for medicinal purposes.
A transitional place to the order of bristly-footed (Chaetopoda Oligochaeta) worms is occupied by Acanthobdella peledina, found in Lake Onega.
