Leeches that eat. The external and internal structure of the leech. Leeches nutrition and propagation

Leech class (Hirudinea)

Leeches ... This word usually causes an unpleasant feeling: the imagination draws long, dark worms living in marshy ponds, attacking a person and sucking his blood. Many people know only one leech - medical, used in the treatment of certain diseases, often very serious. Meanwhile, there are about 400 species of leeches on the globe, their structure is diverse, they live not only in marshy ponds, but also in rivers, lakes, mountain streams and even in seas and oceans. Bloodsucker leeches do constitute the majority of this class of annulus type, but they live on different animals (representatives of all classes of vertebrates, soft-bodied, crustaceans, aquatic insects, worms, etc.), and not just mammals and humans. And very few people know that many types of leeches cannot suck blood, but belong to the number of predators that swallow small or whole animals in part. True, predatory forms evolved from blood-sucking animals and retained the main characteristics of their ancestors, but they With regard to leeches sucking the blood of mammals and humans, there are a fair number of them in the tropics, but in our country there are only two or three of these species (out of 50 freshwater species) and they are distributed mainly in the southern regions.

Affiliation leeches  to type of annelids   no doubt. Their body is segmented, the central nervous system consists of head nodes, periopharyngeal cords and the abdominal chain; the skin-muscle bag has the same basic elements as the other rings, the transfer of substances is carried out using the circulatory system, the excretory organs are metanephridia, the intestine is through, ending with the anus, is muscular, abundantly equipped with blood vessels, etc. at the same time, many features are characteristic of leeches, which make it easy to distinguish them from other groups of the type.

Due to the need to attach to the body of other animals to suck blood, leeches developed two suction cups (front, surrounding mouth, and back), the body became more or less flattened. There are no bristles, with one exception, as these worms crawl with the help of suction cups. The number of segments, or somites, unlike other annuli, is constant in all species, with the exception of one, is 33, of which the last seven form the posterior sucker. A relatively small number of segments probably reduced the flexibility of the body, and leeches developed a very characteristic secondary ring of the body: somites are divided into a certain number of rings for each group of species. At medical  and other maxillary leeches in somite five rings, in cochlear  and the vast majority of species family of flat leeches  - three, etc. Secondary ringing affects only the external integument and does not extend to internal organs. The central ring is the one that carries the node of the abdominal nerve chain.

The digestive apparatus has undergone significant changes. All leeches, with the exception of one ancient species, are divided into two detachment: proboscis and jaw (spineless).The former developed a muscular trunk in the anterior part of the digestive tube, while the latter developed the jaws (usually there are three), seated with denticles. With the help of a trunk or jaws, blood-sucking species damage the skin or mucous membranes of their victims. In predatory maxillary leeches, swallowing their prey entirely, the jaws decrease or even completely disappear. Behind the pharynx, which serves to suck blood, and the short esophagus is the stomach, the volume of which in blood-sucking species is greatly increased due to paired lateral processes. In predatory species, the processes of the stomach completely or partially disappear. The assimilation of food takes place in the intestine that follows the stomach, which also has processes in many leeches. Feces are removed through the hind gut and anus located on the dorsal side, at the back of the sucker.

It is well known that after bites of leeches, wounds bleed for a long time. This is because in the wounds of the salivary glands that open into the oral cavity of leeches, a special protein substance hirudin  (from the Greek word "hirudo" - leech), which prevents blood coagulation. If hirudin were not secreted, then blood clots (blood clots) would quickly form and blood sucking would become impossible. Thanks to hirudin and other substances secreted by the salivary glands, blood is stored for months in the stomach of leeches in a liquid state, without undergoing rotting.

All leeches of hermaphrodite (in adult worms both male and female genital organs are developed) and reproduce only sexually. On the ventral side of these worms, above the middle part of the body, two genital openings are quite clearly visible: the anterior, the larger - the male, the posterior - the female. The distance between these holes, measured by the number of rings, varies for different species and is important for determining the types of leeches. Fertilization, i.e., the fusion of gum and ovum, occurs inside the body. Seed is transmitted through sexual intercourse in two ways. In some species (including the medical one), it is inserted into the female genital opening with the help of an aggregate organ that looks like a thin thread, while in the rest, livestock are secreted in special sacs (spermatophores) that attach to the skin of another leech in different places. Zhivichki through wounds that form on the skin after attachment of spermatophores penetrate the body, look for mature eggs and fertilize them.

Fertilized eggs are secreted in cocoons, the structure of which will be described later. In sexually mature leeches, as well as in small-bristled worms, a "girdle" is formed in the genital area on the skin, often clearly visible. From the secretions of the gland glands the walls of cocoons are formed. At the end of development, which usually lasts several weeks, small worms emerge from the cocoons, mostly similar to adults.

Leeches are common in all parts of the world. Each zoogeographic region is characterized by its composition of the species of these worms. There are very few species living in two or more areas. Sea leeches are divided into a number of groups, each of which is characteristic of a certain region of the World Ocean and the adjacent seas. In the Black Sea, there are no leeches at all, since its salinity (two times less than the salinity of the ocean) is insufficient for real sea leeches and is too large for species that live in fresh and brackish waters.

Leeches are of practical importance, both useful and harmful, which will be briefly described in the description of individual species.

Subclass ancient leeches (Archihirudinea)

In the forties of the last century, the outstanding Russian naturalist A.F. Middendorf collected paledi, or cheese  (Coregonus peled - from whitefish, salmon family ), strange worms corroding the soft parts of the dorsal fin. Already a superficial study of these worms, conducted by the famous zoologist E. Grube, showed that in their organization the signs of small-worm worms and leeches are surprisingly combined. At the front end of their body, there are bristles that act as an anterior sucker (absent in these worms) and, together with an imperfect posterior sucker, serve to attach to the host body. Grube attributed the worms he described to the new genus Acanthobdella, which means “armed leech,” and gave the species name by the name of the fish from which they were taken. Afterwards acanthobella, or bristle leech, was thoroughly studied by the famous Russian zoologist N.A. Livanov, who found out that in the internal structure it is also observed a combination of signs of small-worm worms and leeches, but the signs of the latter prevail, and the acanthobella was assigned to a special, lower group of the leech class. Now the bristle leeches are isolated in a special subclass of ancient leeches whose existence is a brilliant confirmation of evolutionary theory.

Subclass real leeches (Euhirudinea)

This subclass includes all types of leeches, except for the bristle. The anterior suction cup is always well developed; there are no bristles; all the features that distinguish leeches from small-worms are well expressed. The subclass is divided into two groups: trunk squad   and jaw force , or helpless.

Squad of proboscis leeches (Rhynchobdellae)

The name of the detachment speaks of the main feature of the species included in its composition: they all have a trunk. It’s very difficult to notice the trunk of a living leech; sometimes it sticks out of the mouth of dead worms. The detachment, in turn, is divided into two sharply different families: familyleeches  and leech family .

Family Flat leeches , or Glossiphonides (Glossiphonidae). The Russian name of this family is not entirely successful, since a flattened body is generally characteristic of leeches. True, glossossonids (or, as they were previously called, klepsin) flattening is especially pronounced, but there are exceptions. It would be more correct to call these leeches wide or leaf-shaped, because their body is relatively wide, tapering to the ends. The sizes of glossifonids are usually insignificant (from a few millimeters to several centimeters). Do not swim. They suck blood (and some species and liquefied tissues) of various animals - invertebrates and vertebrates.

All types of glossifonids take care of the offspring. Leeches cover with their bodies the thin-walled shapeless cocoons laid by them, in which many eggs are enclosed. After hatching, young leeches attach to the mother’s belly and move with it. In case of danger, the leech mother stops moving, protecting the children with her body. Growing up, the young go to an independent life, first temporarily, then completely.

The first glossyphonids, like the ancient leeches, probably sucked the blood of fish. In our water bodies, a rather mobile Hemiclepsis marginata is found, which is sometimes found on different fish. It is easy to distinguish it from other glossyphonids by the greatly expanded front end of the body, which helps it to stay on quickly moving hosts. Its length is up to 30 mm, the body color is greenish with an admixture of brown. She also willingly sucks the blood of amphibians.

Hemiclepsis is especially numerous in the Amur basin. In this regard, it should be noted that it lives in South Asia.

Within our country there are two types of Protoclepsis: widespread common bird leech  (R. tessulata) (it is also known in the Americas) and spotted bird leech  (P. maculosa), found in the northern half of Europe and in North Asia. Mostly the first is dangerous. Interesting features of the life of bird leeches, studied mainly from the second of them. The first time it sucks the blood of birds 1-1.5 months after leaving the cocoon, the second time - 20-30 days after the first feeding and the third time - 1.5-2 months after the second. 4-6 months after the third feeding, protoclepsis becomes sexually mature and multiplies. After laying cocoons, leeches can live for some more time, but they no longer suck blood. Only those who, for whatever reason, have not laid cocoons, can eat for the fourth time.

Common bird leech lays three to five cocoons. The total number of eggs laid varies widely: from 65 to 611. The young can live on the body of the mother's body for up to two to three months.

Southern origin and glossiphonides belonging to the genus Batracobdella ("batrachos" in Greek - frog, "bella" - leech) They suck the blood of amphibians. In Crimea, there is a large quantity of a small (usual length of about 8 mm) greenish-brown leech with a pair of large eyes - B. algira. She spends most of her life on large frogs and leaves them only when the breeding season begins (compare with a turtle leech). It was first found in Algeria, which explains its species name, and is common in northern Africa, in Asia Minor, and in Europe - on the Iberian Peninsula and southern Balkan. In our country, except for the Crimean peninsula, it has not been found anywhere. It is believed that once Crimea was connected with Asia Minor. It is possible that it was then that this interesting leech penetrated the Crimea. Another species of the same genus - the four-eyed Batracobdella paludosa - also gravitates to the south of Europe, but it comes quite far to the north (England, Poland, etc.) and never meets the first species. The main source of food for this leech is frogs and other amphibians, but it also sucks the blood of coils (from gastropod mollusks), which, like vertebrates, have red blood, that is, they contain hemoglobin.

The most famous representative of glossifonids in our fresh water bodies, by the generic name of which the whole family is named, is a snail leech (Glos-siphonia complanata). Her body, whose length rarely exceeds 15-20 mm, is relatively very wide. The color is greenish-brown, very variable, sometimes very mottled. On the dorsal side are three pairs of longitudinal rows of papillae, of which the median ones are better developed than others. An adult leech is extremely lazy and lies motionless for a long time, sucking on underwater objects and broadleaf plants *. Due to its color and stillness, often covered with particles of silt, it is almost or completely invisible. Its main victims are mainly pulmonary gastropods, soft-bodied (prudoviks, etc.), which often after her attack die as a result of loss of blood and other juices or obstruction of the respiratory opening. Mastering a leech by its victims is facilitated by the slowness of these mollusks.

* (If snail leeches are separated from the substrate, then they, like some other glossyphonids, coagulate like hedgehogs.)

Snail leech lives about two years. Propagated twice: at the end of the first and second years of life. Lays up to 120 eggs, 20 in each cocoon. After the second egg laying, leeches usually die, only a few of them can reach the age of three. G, complanata also lives in North America.

It is even more common in our reservoirs, especially in stagnant, small (normal length - 5-6 mm) grayish-white glossifonida - Helobdella stagnalis. Its distinguishing feature is a lenticular plate of yellow or brown color, located on the back between the 12th and 13th rings. Therefore, in Russian it should be called lamellar leech. Eye one pair, rather large. In contrast to the cochlear leech, N. stagnalis is very mobile, which facilitates its attack on the larvae of aquatic insects, crustaceans, small-bristle worms, other leeches and small invertebrates, which it often sucks out entirely. At the same time, due to its mobility, it much more often than a cochlear leech enters the stomachs of fish. The lamellar leech lives all year. The leeches hatched from cocoons in the spring grow quickly and can already breed in July - August; then, next spring, they again lay their eggs and die. In one clutch of 7 to 37 eggs, which are in two cocoons. N. stagnalis is one of the most common leeches: in addition to the northern half of Asia, Europe and northern Africa, it lives in North and South America, where there are at least two dozen species of the same genus, while from other parts of the world it is known by 1 - 3 types. It is possible that we have such a common leech of South American origin.

In conclusion, a review of flat leeches should briefly dwell on the Baikal species of this family, of which there are only three: Baicaloclepsis grubei, B. echinulata, Paratorix baicalensis.

The fauna of Baikal is amazing and attracts the attention of zoologists for over a hundred years. The vast majority of animals living in this deepest and oldest lake on the globe are found only here and are very different from animals of the same groups inhabiting the water bodies of Siberia. Many Baikal species belong to special genera and even families. These leeches also belong to genera that do not have representatives outside Lake Baikal. Of particular interest is Baicaloclepsis echinulata. Its specific name ("black") is well-deserved: the entire back is covered with papillae, and this grayish-white leech (its length is not more than 15 mm) has a furry appearance. Larger (length up to 40 mm) - Baicaloclepsis grubei is yellowish in color with a pale pink tint, has six rows of large papillae on the dorsal side. The first leech has no eyes at all, and the second they are poorly developed. The underdevelopment or lack of eyes and the whitish color of the body of both leeches is probably due to the fact that they live at a fairly large depth, where there is very little light. The third, the Baikal glossifonida (Paratorix baicalensis), probably lives in better light, as its color is brownish and its eyes are developed. There are no reliable data on the nutrition, reproduction and development of these interesting leeches. All of them have small posterior suckers and, obviously, suck the blood of sedentary animals, which is unknown. Like almost all Baikal animals, they can live only in cold water, well saturated with oxygen.

Quite small baikal trachelobdella  (Trachelobdella torquata), the usual length of which is 4-6 mm. Its owners are small crustaceans and bull-calves, i.e., the most numerous groups of Baikal animals.

Baikal trachelobdella is very numerous in the coastal zone of Baikal. This is the only Baikal leech that occurs outside the lake, in the Angara flowing from it, but only in the very upper part of the river, where the water is still cold and very saturated with oxygen. In this part of the Angara, ordinary leeches are not found. In general, the species of both groups (ordinary and Baikal) do not live together. It should be noted that Baikal animals are very sensitive to changes in living conditions (deterioration of the oxygen regime, runoff of various chemicals, siltation of soils, etc.). So, for example, after the construction of the dam of the Irkutsk hydroelectric power station, the Baikal trachelobdella is almost not found in the Irkutsk reservoir, which was formed in the upper part of the Angara, where this leech was numerous. In the named reservoir, the water is relatively clean, but the bottom began to silt and the current velocity sharply decreased. This shows how dangerous various changes in the regime of Lake Baikal are, the fauna of which is unique and must be preserved at all costs.

Of the species of the considered family that live in our northern and Far Eastern seas, we mention only a few.

On the shrimp  (Sclerocrangon boreas) and, possibly, on the gobies find a small leech (length 10-20 mm) - Platybdella fabricii, found from the Greenland to the Sea of \u200b\u200bJapan. She usually attaches cocoons to carapace shells.

Recently, a number of species of ichthyobdellides have also been found in Antarctic waters. In general, representatives of this family live in all oceans.

Detachment maxillary, or spineless, leeches (Gnathobdellea, Arhynchobdellea)

The species of this order do not have a trunk, but the jaws are developed, which in predatory forms are less developed or completely rudimentary.

Jaw Leech Family   (Gnathobdellidae). Large (length over 100 mm) or medium size (length over 30 - 50 mm) worms. The eye is usually five pairs arranged in an arc. There are three jaws in the oral cavity. Somite is five-ringed. There is a copulatory body. Cocoons with eggs are laid in moist soil in the coastal strip. Most species are bloodsuckers living at the expense of different vertebrates, a minority are predators who swallow their prey.

The most famous member of this family is medical leech (Hirudo medicinalis), which already in ancient times was used to treat people. Its average length is about 120 mm (with a width of about 10 mm), but it can reach significantly larger sizes (250-300 mm), and in the laboratory of the famous Soviet specialist in these worms G. G. Shchegolev by intensive feeding was grown for one and a half years a giant leech in the length of 440 mm!

This shows that it is not always possible to judge the age of a leech by its size. Meanwhile, it was previously believed that medical leeches that have reached maximum sizes have an age of about 20 years. Now this assumption needs to be verified. For medical purposes, relatively small worms, several centimeters in length, are usually consumed. The color of Hirudo medicinalis is very variable, and its many color forms are described. The main background of the dorsal side can be brown (different shades), reddish, olive-black, olive-greenish, etc. But no matter how great the variability of color, a medical leech can always be recognized by two longitudinal patterned narrow stripes on the back, which noticeable even in very dark specimens. Lateral margins (dorsal and ventral) yellowish-orange. The belly is usually very mottled, but it can also be monophonic. The surface of the body is covered with very small papillae. The body is quite dense. The posterior sucker is large, its diameter exceeds half the largest body width. Leeches bite through the skin with three jaws, seated at the edges with sharp teeth (up to 100 on each jaw). The anus is small.

Medical leeches usually live in small shallow ponds. They can tolerate drying if the soil remains moist enough. Representatives of all classes of vertebrates suck blood, but the main sources of their nutrition are frogs and mammals (most often cattle coming to a watering place). Experiments in the laboratory showed that when feeding on frogs, leeches reach a state that allows their use after 17-20 months, and when feeding on rabbits or first on frogs, and then on rabbits - after 8-10 months. Leeches can reach puberty when fed by cold-blooded animals, but then their development takes a very long time, they lay only one cocoon (instead of three to eight) and with fewer eggs. The most effective, apparently, combined feeding, i.e., on frogs and mammals, which happens in nature. Thus, the evolution of the medical and a number of other maxillary leeches occurred in close connection with mammals.

Medical leeches  - very mobile worms, especially when hungry. They, like most maxillary leeches, swim well, making wave-like movements. They must be kept in a well-closed container (with gauze, net, etc.), for they crawl out of the water. If there is not enough oxygen in the water, then they, like many unwilling leeches, strengthened by the back suction cup, make breathing movements similar to swimming ones. These leeches respond well to various irritations. So, if you make noise in the water with a stick, lowering the plywood sheet, just walking, then they quickly sail to the noise source. If two identical objects are thrown into a vessel with leeches, one of which was in the hands of a person, and the other is not, then more worms accumulate near the first than about the second. On some odors (for example, cologne), they react negatively. They prefer a warm surface to a cold one. It is clear that sensitivity to various irritations helps these bloodsuckers to look for their victims.

In nature, Hirudo medicinalis reaches puberty, apparently only in the third year of life and lays cocoons once a year, in the summer. Under laboratory conditions, mature leeches can be grown in 12-18 months and kept at 18-22 ° C in winter and 24-27 ° C in summer, forced to breed at any time and lay cocoons every 6-8 months. In a natural setting, leeches lay cocoons slightly higher than the water level in the coastal strip, for which they need to overcome great soil resistance. A case is known when cocoons were found a hundred meters from a reservoir. Cocoons are very similar to cocoons of silkworms, their wall consists of woven fibers secreted by the glands of the girdle, the average length of the cocoon is 20 mm, width 16 mm, the color is reddish-gray. In one cocoon, an average of 15-20 eggs, the duration of development is about a month. Hatched leeches are called “thread”, their length is only 7-8 mm, their jaws are still very weak, and they are not able to bite through the skin of mammals, but can soon bite through the skin of amphibians and suck their blood.

Medical leech  southern origin. In our country, it is distributed mainly in Moldova, the Ukraine, the Caucasus and Central Asia (although it does not exist in Turkmenistan). In the northern half of the European territory of the USSR, almost throughout Western Siberia, throughout Eastern Siberia and the Far East, it is absent.

For many centuries, Hirudo medicinalis has been used in the treatment of a wide variety of diseases, it was one of the favorite remedies of traditional medicine and doctors. Back in the middle of the last century, hundreds of millions of these worms were imported from Eastern Europe to Western countries, where leech stocks were depleted. For example, in 1850, about 100 million units were imported into France. Export of leeches from Russia was considered the most profitable income item. In the second half of the XIX century. as scientific medicine developed, the use of leeches by doctors began to decline rapidly and they almost ceased to be used, although they continued to be used in folk medicine. However, in the 20s of this century, leech treatment began to revive. Various studies by physicians and physiologists have shown that hirudin and other substances secreted by leeches and possibly other substances have a beneficial effect in some diseases, especially thrombophlebitis, hypertension, etc. Of course, leeches are not now considered as a panacea for all ailments, as was believed when Something, but in some cases their use is advisable. The demand for leeches has recently increased again, and often pharmacies cannot satisfy it. In this regard, Moscow experts have developed methods for the rapid cultivation of laboratory leeches, both caught in nature and obtained from cocoons in the laboratory. The widespread use of methods for the artificial cultivation of leeches does not exclude their systematic catch in natural reservoirs, but it is necessary to protect these useful worms from complete extermination, ensuring their reproduction.

Medical leeches sometimes cause harm. In some shallow reservoirs in the south, people may be subjected to massive attacks by these bloodsuckers. In such cases, you need to immediately get out of the water and remove the worms, while it is better not to tear them off, but sprinkle with salt or grease with alcohol, iodine, etc., after which they themselves will disappear. With careless maintenance of leeches used for treatment, they can creep into the mouth and other openings of a person and even stick to the eye.

Another jaw leech poses a serious danger to humans and domestic mammals - limnatis  (Limnatis nilotica). They call her in Russian horse  or nile, egyptianalthough it sucks the blood of various mammals and lives not only in Egypt, but in all Mediterranean countries, in Abyssinia, Congo, Tanganyika, here in Transcaucasia and Central Asia. In adulthood, it reaches almost the same size as Hirudo medicinalis. Her back is greenish-brown, the belly, unlike other leeches, is colored darker than the dorsal side and casts blue or purple. There are yellow stripes on the sides of the body. The posterior sucker is large, its diameter noticeably exceeds half the largest body width. The jaws are small and weak and cannot bite through the skin. Therefore, limnatis can suck blood only from the mucous membranes, which explains its serious harmfulness. It lives in springs, in various other small reservoirs and enters the oral cavity, and then into the pharynx, nasopharynx, larynx of mammals and humans, when they drink water directly from reservoirs. In some cases, a leech can clog the larynx and cause suffocation. During the bathing of people in the reservoirs where the described leech is found, it can penetrate into the urinary and female genital organs, into the conjunctival sac of the eyes. The presence of limnatis causes hemoptysis and bleeding, often profuse. According to some reports, in Central Asia sometimes up to 30% of cattle driven to slaughter is infected with it. Similar data are provided for Bulgaria, Central Asian countries, etc. The penetration of limnatis into human and animal organisms is facilitated by the fact that the surface of her body is very smooth and emits a huge amount of mucus, and thanks to the powerful posterior suction cup it is firmly held in various organs. A case is known when this leech was in a person for 3 months and 20 days. A leech can also suck frogs. Its reproduction and development is in many ways similar to the same processes of Hirudo medicinalis.

Maxillary bloodsucking leeches are numerous in hot countries. So, in Africa (south of the Sahara) 9 species of the genus Hirudo and 14 species of the genus Limnatis are described.

Among the species of the described family, there are a fairly large number of necro-sucking, predatory leeches. In the reservoirs of the USSR, only one such species is widespread - great Loch cone leech  (Haemopis sanguisuga). It was called Lozhnokonskaya to distinguish it from limnatis, which it looks like in appearance, and large - unlike some pharyngeal leeches, called (see further). In size, it is not inferior to a medical leech, and often surpasses it. The back of an adult N. sanguisuga is black with a brownish tint, dark spots can be scattered on its surface, and in young specimens the main background of the back is lighter than in adults, and the correct pattern is often visible on it. The belly is gray or greenish-gray, side yellow ribbons are often absent. The posterior sucker is small (less than half the largest body width). Her jaw is much worse developed than that of H. medicinalis. The anus is large, as large pieces of undigested food stand out through it. The Great Lozhkonskaya leech is a strong and voracious predator eating worms (including leeches), soft-bodied, larvae of aquatic insects and other aquatic invertebrates, as well as small vertebrates (for example, tadpoles), which it can overcome. Sometimes you can observe how two predators from two opposite ends try to swallow a long worm. If they can not cope with the prey, then tear pieces from it.

Great False Leech  lives mainly in shallow reservoirs, often in puddles that sometimes dry out, but their bottom remains wet; It also occurs in the coastal zone of lakes and rivers. The described species is widespread throughout our country (up to the Komi Autonomous Soviet Socialist Republic and the north of Siberia), but is rarely found in colder areas and lives in larger bodies of water, because small bodies of water in the harsh climate freeze to the bottom. Especially numerous are N. sanguisuga in the south of the USSR (Moldova, Ukraine, the Caucasus, etc.). Reproduction and its development are similar to the same processes of medical leeches. The desman, and possibly other aquatic vertebrates, willingly eat this large leech.

In the Amur basin, especially in the south of Primorsky Krai, the predatory maxillary leech Whitmania leavis, which sometimes reaches even greater magnitude than N. sanguisuga, is often found in small bodies of water. It differs from the latter by a strongly narrowed front end of the body, a reddish-brown patterned color, which varies greatly with age. This species and other species of the same genus are common in China, Japan and South Asia. In this regard, it should be noted that several types of leeches are known in the Amur basin, originating from Southeast Asia and absent in the rest of the USSR. A significant number of species of predatory jaw leeches lives in the Americas. In greater numbers than in Europe and North Asia, they are found in Africa, South and Southeast Asia. Some of these species in the humid tropics lead a semi-terrestrial lifestyle.

Terrestrial maxillary bloodsucking leeches . These leeches are especially numerous in South and Southeast Asia, and also live in southern Japan, in Australia, on the island of Madagascar, in South and Central America. The most famous species of the genus Haemadipsa. They live where the humidity is so high that drying does not threaten them. Their size in comparison with other maxillary leeches is insignificant (average length 30-40 mm). They find shelter in the bushes, trees, in the grass, where, being hungry, they sit in a wait-and-see attitude, attaching themselves to the rear suction cup. Possessing a keen sense of smell, they easily find their prey - mammals and humans. These are extremely unpleasant bloodsuckers, climbing into different crevices of clothes. Recently, special chemicals (repellents), which are used to soak clothes, have been invented to deter leeches. Even after several washings, such clothes protect people from the attack of leeches.

Terrestrial maxillary bloodsucking leeches, probably distant "relatives" of tropical species, are found in the mountains of Austria and Yugoslavia. Their two species belong to the genus Xerobdella ("xeros" in Greek - dry) They are believed to suck the blood of salamanders * in the mountains. It is possible that in past geological eras, when the climate in Europe was warmer and wetter, these leeches were widespread, and after deteriorating climatic conditions they remained only in mountainous areas, protected due to isolation from the struggle for existence with other leeches or competitors from different groups animals.

Pharyngeal Leech Family (Nerpobdellidae). All species of this family - predators and blood do not suck. They undoubtedly descended from the jaw leeches, as evidenced by the vestiges of the jaws in many of them. Stomach without appendages. The arrangement of the eyes is very characteristic: four are located on the edge, and two on the sides of the front end of the body. Somite five or more rings. Fertilization occurs with the help of spermatophores. Cocoons are most often oval, brown in color, attached to underwater plants, stones, etc. Swim and breathing movements (see. "Medical leech"). A large number of species of this family live in the reservoirs of the USSR (about 28% of the total number of species of our freshwater and brackish-water leeches), and almost everywhere in the number of specimens they come first. However, they are not in Baikal. It should also be noted that only three or four species of the family in question are widespread in our country, and the rest are found only in some places in the south. The vast majority of pharyngeal leeches that live on the territory of the USSR belong to the genus Herpobdella (other names of the genus: Erpobdella and Nephelis). All species of this genus are called small pseudo-horse leeches.

We have the most famous pharyngeal leech - common herpes  (Herpobdella octoculata). She is the most common and numerous leech in Europe and North Asia. Its length rarely exceeds 40-50 mm. The typical form has a brown or grayish-brown back, covered with transverse rows of yellow spots. However, the dark pigment can disappear to one degree or another, and the spots remain visible only on part of the back or are completely absent, as a result of which the dorsal surface becomes monochromatic, grayish, on which dark spots remain in some places. The life cycle of H. octoculata is similar to the cycle of Glossiphonia complanata (see above), i.e. this leech lives for about two years. Her brownish-yellow cocoons are often found on aquatic plants and various underwater objects. The number of eggs in one cocoon can reach 24, on average it is 11 -12. This leech eats small worms, insect larvae and especially mosquitoes chironomide. She herself is attacked by various predatory invertebrates; find it in the stomachs of fish. Dwarf (the length of sexually mature individuals is on average 16-17 mm), an almost uniform form of the described pharyngeal leech species lives in Lake Sevan. This lake, despite its high mountain location, is very rich in leeches, however, represented by the three most common species: in addition to Herpobdella octoculata, there are previously described Glossiphonia complanata and Helobdella stagnalis, which are also small in size and light in color.

Another species of the same kind - herpobella linear  (Herpobdella lineata), so named because it has two longitudinal narrow black stripes in the middle of its back, it is often found in large numbers in the south and lives in puddles, often quite dry. Two peculiar leeches are related to her: herpobella cave  (Herpobdella absoloni) and caspian archaeobdella  (Archaeobdella esmonti).

The first leech that lives in the caves of the Balkan Peninsula and recently found in the caves of Georgia, like most animals living in complete darkness, is whitish and devoid of eyes. The same signs characterize the second leech, an ordinary inhabitant of silt in the Caspian Sea, that is, also living in the dark or almost without light. The most characteristic feature of archeobdella, distinguishing it from all leeches, on the basis of which it was singled out in a special genus, is an almost complete reduction of the posterior sucker. She moves in the thickness of the silt, bending her worm-shaped body, and the back suction cup has become redundant. Archeobdella cocoons are similar to herpobdell cocoons.

Archeobdella is also found in the mouths of the rivers of the Azov-Black Sea and Caspian basins.

Among the pharyngeal leeches there are also large worms, which in size are not inferior to the large maxillary leeches and even surpass them. All of them are of southern origin.

In the floodplains of the Dniester, not far from Odessa, a huge (length up to 250 mm!) trochaeta (Trocheta subviridis), which is distributed throughout southern Europe and northern Africa. Her body color is brown or gray. This is a strong muscular leech, capable of digging deep into the damp earth of the coastal strip in search of the earthworms that it devours. Some birds, and probably other vertebrates, eat it. So, in the goiter of one loaf, many large trochets were found. These worms are also used as excellent fish bait. Trochet cocoons are similar to herpobdell cocoons, but, of course, larger than them. It is interesting to note that another species of the same genus, Trocheta bykowskii, is adapted for life in mountain streams (for example, in the Carpathians) and small fluid reservoirs (in England, Holland, and other Western European countries). Recently, it is indicated for Afghanistan and is likely to be found in the Crimea and the Caucasus. The two more primitive species are close to the more primitive Fadejewobdella quinqueannulata, found only in some places in Ukraine and in the north-west of the Caucasus. She lives in puddles and, like trochets, suffers drying up of water bodies, if the soil of the latter remains wet enough. A significant number of species of large pharyngeal leeches, leading a semi-terrestrial lifestyle, are known in Japan and Southeast Asia, where the climate is very humid.

Previously, the medical leech lived in almost every corner of Europe, but now, its number has declined sharply. This happened because active fishing in the past, as well as draining of swamps, significantly reduced the population.

The body of a medical leech is flattened, round, having two suckers that grow on the front and rear ends. The front suction cup is crowned with a mouth opening.

In natural habitat, the leech attaches to various underwater plants, where it waits for the victim. The leech is very gluttonous, with a weight of about 2 g, it can easily suck up to 15 ml of blood in one go, while the body weight increases by almost 10 times.

The blood that the leech from the victim has sucked does not clot and can remain in a liquid state for several months. The period that she can live from the first meal to the next is about 2 years.

To digest the blood and keep it in its original liquid form, special bacteria called Aeromonas hydrophila are found in the leech gut. Leeches have a symbiotic relationship with these microorganisms. This means that both participants in the tandem benefit for themselves. In addition, if unwanted bacteria appear in the leech stomach, the symbiont destroys them, cleansing the blood contained in the worm.

The use of leeches in domestic medicine is directed against diseases such as varicose veins, bleeding (hemorrhage), and an ulcer. In the west and in Europe, with the help of these worms, they fight with venous stasis, which is formed during tissue transplantation. Some medicines contain leech extract. To date, technological advances have made attempts to create an artificial leech.

Distribution area for medical leeches

They live in large numbers in the north to the border with Scandinavia, in the south - to Algeria and Transcaucasia. There is an assumption that, within the boundaries of their habitat, they live in isolated populations, avoiding contact with groups of other leeches. The form of leeches used in medicine lives mainly in Azerbaijan and the Caucasus. Another form, pharmacy, lives in the Krasnodar Territory, Stavropol Territory.

Typical leech habitat

Leeches are adapted to the aquatic and air environment. To pump from one reservoir to another, they are able to cover a long distance on land. They live only in fresh waters. Do not tolerate salty water sources. The usual place where they live is lakes or ponds, the bottom of which is lined with silt. They prefer clean water, where frogs live and reeds grow densely.

The International Union for Conservation of Nature (IUCN) classifies medical leeches as animals with vulnerable numbers. Some habitats that have long been familiar to leeches are no longer their distribution zones. The reason for the decline is the massive ebb for medical purposes. To date, the intensity of depletion of the population has decreased, due to the fact that the method of bloodletting has become irrelevant.

Also, biofactories are created in which leeches are artificially grown, however, this does little to restore the population. Also a clear factor that leads to the death of a large number of these animals is the reduction in the number of frogs. They are the main source of nutrition for small leeches, not able to suck out to larger animals.

Features of the structure of the body of leeches

As mentioned earlier, a medical leech has an elastic body, elongated, with well-developed muscles. It is divided into 33 segments. It has two suction cups, the back is larger than the front, its function is to harden on the substrate. Each segment is divided into a certain number of segments (3 or 5), in the central ring of each segment there are sensory papillae.

The abdomen and back are different in color, the back is dark, with brown stripes. Outside, the body has a cuticle, it is repeatedly discarded during growth. By the intensity with which the animal sheds, one can determine the state of health of the leech.

A leech has four layers of muscle. The first consists of circular fibers, responsible for swallowing blood, followed by a layer of diagonal and deep longitudinal fibers, they provide a contraction of the body, the last layer - the dorso-abdominal muscles, they serve to make the body flat. Connective tissue is very elastic, dense, it covers both muscle fibers and organs.

The nervous system consists of the ganglia and segmental nerves emanating from them. At the anterior and posterior ends of the body, the ganglia combine to form a pair of synganglia, one pharyngeal and one anal.

The receptors that are located on each segment are divided according to the type of sensitivity into three types: baroreceptors, thermoreceptors and chemoreceptors. All of them serve for food search and orientation in space. In addition to that, on the first five segments there are five pairs of eyes, including special pigment cells, with their help a leech can distinguish light from darkness.

The digestive system includes: the mouth, in the central part of the anterior sucker, the jaw - one upper and two lower, on each there are 100 cloves of chitin, they can damage the skin of the body to which it is sucked. A special secret also enters the oral opening, which prevents blood from clotting at the time of absorption. The stomach is presented in the form of an elastic tube, which has 11 paired pockets. The muscular sphincter separates the stomach from the intestines. In the latter, stool is accumulated, during the removal of which the water turns dark.

The urine that forms in the leech's body is secreted through the nephropores. By the type of hermaphrodite breeding, she cannot fertilize herself alone; she still needs a couple.

Leeches nutrition and propagation

It feeds mainly on the blood of warm-blooded animals, but sometimes it can attack frogs and fish. The duration of blood absorption always varies from the state of the leech.

A starving individual can take blood for 2 hours.

Propagated once a year, in the summer. The copulation process takes place on land, leeches wrap around each other and stick, after fertilization, the leech lays 5 cocoons, of which in 2 weeks babies will be born.

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  Leeches belong to a subclass of annelid worms, and they, in turn, belong to the class of girdle. In Latin, a leech sounds like a "hirudinea" (Hirudinea). Around the world, there are about 500 species of leeches, in Russia about 62 species.

But for treatment use only a medical leech. Among medical leeches, two subspecies are distinguished:

Healing Leech (Hirudina medicinalic)

Pharmaceutical Leech (Hirudina officinalic)

Color. It can vary from black to reddish brown. The abdomen is mottled. The sides are green with an olive tint.

The size. About 3 - 15 cm - length, about 1 cm - width.

Life span. Up to 20 years.

Habitat. They are found mainly in Africa, Central and Southern Europe, as well as Asia Minor. In Russia, they are not so numerous, mainly spread in the south of the European part of the country. Although there is evidence that individual individuals of the species were found in the southern and eastern parts of Siberia.

They love fresh clean water - lakes, ponds, quiet rivers, as well as damp places near the water - clay shores, moist moss. Leeches live in stagnant water - flowing for them is unfavorable.

Lifestyle and behavior. Most of the time a medical leech spends, hiding in a thicket of algae, hiding under snags or stones. This is a shelter, and an ambush.

Leeches love warm sunny weather and even tolerate heat very well, it is in these conditions that they are most active. They are not afraid of drought either - they either crawl away from the drying up reservoir or burrow deeper in the coastal silt. Leeches are able to stay on land for a long time in hot and humid weather.

With worsening conditions (lowering air temperature, windy weather), medical leeches become lethargic and passive. Leeches hibernate, buried in coastal silt or bottom soil. Freezing is fatal for them.

The body of the leech is very flattened and stretched when swimming, and the posterior sucker acts as a fin. The wave of leech moves in the water.

For medical leeches, an instant reaction to external stimuli is quite characteristic: smell, temperature, surge.

The hungry leech can be recognized by the characteristic position of the body - it is sucked by the back suction cup to the plant or stone - the front one makes circular motions.

Enemies: Desman, water rat, cutter, bedbugs, dragonfly larvae.

Nutrition. As food, medical leeches use the blood of worms, mollusks and vertebrates, and in their absence insect larvae, ciliates, and mucus of aquatic plants can eat. A leech bites through the victim’s skin and sucks a small amount of blood, about 10-15 ml. When a leech is full, it can remain without food for a sufficiently long time - on average six months, since the blood in its body is digested slowly. However, a record fasting period of 1.5 years was noticed.

Reproduction. Medical leech - hermaphrodite. They begin to lay their leech eggs in the warm period, approximately two weeks before the end of August or in the middle of September. Under adverse weather conditions, this period begins earlier, or is delayed.

In the process of propagation, the leech creeps out on land, digs a small depression in the silt, then buy special leeches, buy medical leeches, buy leeches, buy leeches in Perm, the cover of the leech - a belt - releases a foamy cocoon into which eggs are laid. This cocoon contains albumin - a protein that serves as food for embryos. The egg incubation period is about two months.

Newborn medical leeches are transparent and resemble adults, they still spend some time in a cocoon, eating albumin, but soon crawl out. Small leeches that have not reached puberty attack tadpoles, snails, frogs.

If a leech within three years from the moment of leaving the cocoon does not drink the blood of a mammal, it will never reach puberty.

In previous centuries, leeches were widely used to cleanse human blood. However, in the last century there was a peak of popularity on these worms, as a result of which their collection and intensive destruction of the natural range of leeches led to a reduction in their numbers. Today, the propagation of worms for medical purposes is carried out in specialized laboratories.

Characteristics

The body of the leech has a ring-shaped appearance, but slightly flattened than that of worms. And the stomach is a modified middle intestine. Most species of these worms have eyes, but all have a closed circulatory system.

Each individual has two suction cups:

• back;
• front

Using these suction cups, the worm is attached to the victim, as well as to surrounding objects. With their help, the leech moves.

Diet

What do leeches eat in nature? In most cases, leeches feed on the blood of mollusks, vertebrates and other representatives of the animal world. It is these types (not all) that are used for medical purposes.

Medical leeches have three jaw plates, on which a huge number of small and very sharp teeth. The jaws themselves are an accumulation of thick muscles. At the beginning, a leech pierces the skin with teeth, then tears the tissue and sucks the blood. After a bite, a protein substance called hirudin is released from the sebaceous glands of the worm sucker. It does not allow blood to coagulate, but on the contrary, provokes its flow to the wound. In addition, saliva with anesthetic properties is released, so the worm manages to go unnoticed for a long time.

One of the representatives of this subspecies is a fish leech, which swims beautifully, unlike a medical leech. What do leeches of this species eat? Tissue fluid of fish.

These are quite large worms and can reach 50 centimeters in length. They do not disdain almost any type of fish, on one you can find more than 100 worms.

When a leech does not eat, it swims calmly in a pond or "sits" on aquatic plants. For a person, it does not carry any danger. In winter, these worms do not hibernate, and without fish can live up to 3 months.

The habitat - Eurasia, lakes and large rivers, is very rare, but is found in wastewater. Prefers fish from the genus of cyprinids.

By the way, this worm can appear in the aquarium. What do leeches eat in such cases? All the same tissue fluid. It is quite difficult to cope with such a problem in a closed reservoir, most likely, complete disinfection and disinfection will be required. They can get into the aquarium with live food.

The cochlear leech also belongs to the proboscis annelids. This is a very slow creature that does not even move independently, but completely relies on the current. What do leeches eat? Mostly blood of pulmonary freshwater mollusks, and these are, first of all, prudoviks. After the attack of the worm, as a rule, the snail dies, since the leech causes airway obstruction. Worms also get into the aquarium with live food.

The closest relatives of these species are bird leeches - species that “feast on” the blood of Kamchatka crab and shrimp.

These worms are also called Nile or Egyptian. They live in Central Asia and the Mediterranean, in Transcaucasia. They prefer fresh water bodies of small size.

What do leeches eat in the pond? The equestrian species also prefers blood, but does not have a developed jaw, therefore it is attached to the mucous membranes of the victim when it bathes in a pond. Most often, horses become victims, but the worm does not disdain other artiodactyls, amphibians, and even representatives of the human race. They can even stick to the conjunctiva of the eye. The most dangerous thing about these worms is that, once they enter the body, they increase in size and if they get through the mouth, they can cause obstruction of the airways and, as a result, asphyxiation.

Predatory leeches

The most common species in Asia and Europe is the small Lozhkonsky leech. What do leeches eat in bodies of water with stagnant water? Oddly enough, but they use invertebrate representatives of the animal world. These are insect larvae - microscopic worms. The very small Lozhnokonskaya leech extends to a maximum of 6 centimeters in length, and itself can become a victim of a fish or invertebrate predator.

The leech of erpobella is doing the same. It is quite large and can be seen from afar. This is a wonderful swimmer, but the worm does not have a proboscis, but the body is equipped with a powerful mouth. What do leeches eat? All the same invertebrates, these are mollusks and fish fry, crustaceans, insect larvae. This worm does not disdain even carrion.

After a bite of a medical leech, blood may not stop for a whole day. The largest leech in size has a length of 30 centimeters.

For the first time, they began to grow annelids for medical purposes in Wales, from where leeches are supplied today. But the most interesting is that there are leeches, which in addition to invertebrate fauna species consume vegetation.

Leech treatment arose in ancient times. For example, drawings depicting the use of leeches are on the walls of ancient Greek tombs. The treatment with leeches in their writings described the ancient Greek and Roman doctors, such as: Hippocrates  and Galen. The use of leeches for medical purposes was mentioned in his writings by the great Arab doctor Avicenna.

History of hirudotherapy

Hirudotherapy  literally translated from the Latin language means “leech treatment”, since “giruda” is translated as a leech, and “therapy” means treatment.

The most common treatment with leeches was in Europe. And although in Europe for hundreds of years hiruds were used for medical purposes, the peak fell on the XVII - XVIII centuries. This is due, first of all, to the fact that it was at this time in Europe in medical circles that a rather interesting concept of the so-called "bad blood" appeared. In general, Europe was very fond of bleeding. And there were two methods of bloodletting - vein  and hirudny.  The latter was popular for bloodletting from inaccessible places and so-called “tender” places (for example, gums).

Sometimes doctors could simultaneously put up to 40 leeches on a patient! Leeches at this time were very hot commodities. In London at that time, with a population of about 3 million people a year, about 7 million leeches were used. And you need to consider that not everyone could call a doctor, since the treatment was expensive. Russia delivered up to 70 million leeches per year to Europe. It was a very lucrative export item of the time.

However, after the second half of the 19th century, the concept of "bad blood" left Europe. The bloodletting came to naught. At the same time, studies began on the substance contained in the saliva of hiruda. In 1884, an enzyme was discovered by John Haycraft hirudin,  contained in the saliva of leeches. This discovery gave a strong impetus to the further study and application of leeches in medicine on a scientific basis. In 1902, the first drugs were obtained on the basis of hirudin.

At present, hirudotherapy is undergoing a rebirth. This is due to several factors. In the 20th century, a real revolution took place in traditional medicine: fundamental discoveries were made, many diseases were defeated, many drugs were invented and put into mass production. But by the end of the 20th century, discoveries in medicine began to occur less and less. The effect of many drugs on the human body was studied and it turned out that not always their beneficial properties overpowered the negative impact. The world hobby for hirudotherapy in Asia, especially China and Japan, also played a role. For these countries, a philosophy of harmony with the environment is characteristic, and the positions of alternative medicine are strong in them. All this in aggregate gave an impetus to the revival of hirudotherapy.

A bit about leeches

Leeches feed on blood. Blood is digested in the intestines of the leech for an extremely long time, therefore, feeding the leech alone is enough to remain without food for a very long time. Leeches are hermaphrodites. They move with the help of special suction cups, which are located at both ends of their worm-shaped body.

Stages of treatment

1. Bite

The bite process is as follows: a leech is attached to the desired area on the patient's body using suction cups. After the leech feels that it is firmly entrenched, it carries out a skin bite. Its depth is usually 1.5 to 2 millimeters. After a bite, a leech introduces its saliva into the resulting wound, which, as is already known, contains hirudin, which prevents blood coagulation.

2. Feeding

A leech is usually on the patient’s body for 20 to 60 minutes, depending on the disease. During this time, one leech is able to "drink" from 5 to 15 milliliters of blood.

3. Stop the bloodsucking

In most cases, the leech should itself depart after its saturation occurs. However, often it is necessary to prematurely remove leeches from the patient's body. For this, a swab moistened with alcohol or iodine is usually used. As a rule, the leech instantly disappears after such a reception. Also practice
  the use of starting tobacco smoke on a leech, sprinkling the leech with salt or snuff, watering the leeches with wine or lemon juice, sometimes vinegar.

If all these methods did not cause the leech to “lag behind” the patient, then take a scalpel. It is important to remember that a specialist will never cut a leech in half, as this will not stop her, and the process will continue. The front suction cup is separated with a scalpel, letting air under it. When using the surgical method, the leech will precisely “fall off” from the patient.

After the bite, there will be a wound that will secrete blood and lymph for 6 to 16 hours. This is normal because the hirudin is in the wound. Normally, blood loss from a single wound can range from 50 to 300 milliliters of blood.

Therapeutic effect:

• blood undergoes renewal, since dosed hemorrhage occurs (the same effect is present during the blood donation procedure);
• the action of biologically active substances contained in the leech saliva is triggered;
• there is a set of responses of the body to blood loss, the bite itself and active biological substances that fall into the wound with leech saliva.

Active biological substances contained in leech saliva have the following properties:

• anti-inflammatory;
• painkiller;
• fibrinolytic.

In this regard, with the help of hirudotherapy, you can
  reduce the risk of thrombosis, fight thrombophlebitis, relieve swelling from affected areas of the body (for example, with venous congestion), improve blood circulation in internal tissues with osteochondrosis, relieve pain, and remove toxic substances from the body.

Leeches are actively used in microsurgery to save transplanted skin. They are also widely used in the treatment of varicose veins, are used to relieve muscle cramps and help in the treatment of arthrosis.

Warnings and contraindications

In hirudotherapy, there is a risk of transmission of an infection with leech saliva from the pathogenic environment of her stomach. The risk is minimal if more than 4 months have passed since the last feeding of the hirud, since at that time there is a very small amount of “drunk” blood in its stomach, and the growth of pathogenic bacteria is suppressed by the symbiont bacterium, which the leech itself produces. Reliable protection is the use of so-called “sterile” leeches, that is, leeches grown in an artificial environment, where by definition there can be no pathogenic flora.

The following contraindications to treatment with hirudas are:

• low blood coagulability (the use of leeches can be fatal);
• diseases that are accompanied by bleeding due to poor blood coagulability (hirudin will increase bleeding);
• anemia (anemia);
• hemolysis (destruction of red blood cells with the release of hemoglobin into the environment);
• low blood pressure;
• extreme weakening or exhaustion of the body (for example, against the background of a long or severe illness);
• weakened immunity (infection with a leech titer is possible);
• individual allergic reaction of the body to leech enzymes;
• pregnancy period;
• lactation period;
• childhood.

Only a specialist can prescribe treatment with leeches. It is he who must determine the risk of using hirudotherapy in each case.

Remember, the benefits should always exceed the possible harmful effects!