This amazing animal lives exclusively in fresh waters, leads a predatory or parasitic lifestyle, and is widely used in medicine. It's about a leech. The structure of the body, the features of life and the beneficial properties of this organism will be considered in our article.
Systematic position
According to morphological characteristics, it is rather difficult to classify this organism. The external structure of the leech (the photo below demonstrates it) resembles that of slugs, which are representatives of mollusks. Leeches are actually ringworms.
The external structure of the leech
The maximum length of this worm reaches 15 cm. The structure of the leech body is characterized by the presence of suction cups, which are located at both ends of the body. The ventral side is always flat and the dorsal is convex.
Leeches are attached to the substrate by one or the other suction cup. Thus they carry out "step" movements. Leeches are great swimmers. Thanks to the wave-like bending of the body, they can cover significant distances.
Where leeches live
The structural features of leeches and the way of feeding determine the habitat of this species of worms. They prefer fresh water: swamps, lakes, small rivers and even puddles. One of the necessary conditions for leeches is cleanliness. They breathe oxygen dissolved in water. Inside the body, it penetrates through the integument of the animal. And the most productive process takes place in clean water.
Some species live on land. They burrow into moist earth, clay, moss. But without the presence of water, their life is impossible, since they are not adapted to breathing atmospheric air.
Diversity
Currently, taxonomists know 400 types of leeches. The most common of them are terrestrial, fish, and Lozhnonsk. But out of all the diversity, only one species has healing properties. This is a medical leech.
By the way of feeding, these worms are predators and parasites. There are three jaws in the leech's mouth. On each of them are numerous chitin cloves. Their leeches are used to cut through the victim's integument. After that, the leech absorbs blood with a maximum volume of 15 ml.
Features
The structure of a medical leech has its own characteristic features. Due to this, this species is easy to distinguish from "non-therapeutic." Her body is dark green. On the dorsal side, which is darker, narrow orange stripes are clearly visible. In their extensions are black spots of irregular shape, the number of which varies widely.
The integument of the medical leech is smooth. They do not have hairs, setae or other outgrowths. The body is flattened in the dorsal-abdominal region, almost flat. It consists of 33 segments. The number of rings is small - up to five. The front suction cup is for power. The back is much larger. It is used to attach to the substrate and move.
The integument is represented by cuticle. This substance is inextensible. Therefore, the growth process is accompanied by periodic molting.
The leech's internal structure
The active movement of these annelid worms is possible due to the developed muscular system. It is represented by four layers of fibers. Thanks to the external, blood is swallowed. Movement in space is provided by diagonal and deep longitudinal layers. Body contraction is the result of the work of the spinal-abdominal muscles. Outside, the fibers are covered with a dense layer of connective tissue.
The structure of the leech is characterized by increased sensitivity of the integument. She is able to perceive a whole gamut of sensations: temperature and pressure drops, the influence of chemicals. Five pairs of eyes are located on the head. They are composed of pigment photosensitive cells. Due to such a variety of receptors, leeches easily navigate in space, find their own food and respond to changes in the environment.
The nervous system of annelids is a ganglion type. It consists of an abdominal chain, which forms a knot in each ring of the body. From here, nerve fibers depart to each organ.
Digestive system of the through type. It begins with a mouth opening with jaws, passes into the muscular stomach and intestines, which opens outward through the anus. Excretory organs include numerous nephridia. Excretion of urine occurs with the help of nephropores. In the stomach of leeches, symbiotic bacteria constantly live. They have bactericidal properties, keep the sucked blood liquid, digest it.
All leeches are hermaphrodites. This means that in each individual male and female gametes are formed. Despite this feature, these animals are incapable of self-fertilization. A new organism develops as a result of mating of two individuals.
Beneficial features
In medicine, the structure of a leech and its practical application is studied by a separate science - hirudology. The beneficial properties of this organism have been known since ancient times. As early as the 5th century BC, the ancient Greek scholar Hippocrates described them in his writings.
The widespread use of leeches for medical purposes was promoted by the theory of "bad blood". She dominated in the 17-18 centuries in Europe. In this regard, the bloodletting method was widely used. Doctors used tens of millions of leeches per year for this purpose.
Over time, this theory was recognized as erroneous. The use of leeches has practically stopped. And only in the 19th century their beneficial properties were scientifically substantiated.
What is hirudin
Officially, the therapeutic effect of leeches was confirmed by the English scientist John Haycraft. In the blood of these rings, he discovered a chemical compound that has an anticoagulant effect. It consists in preventing blood coagulation and the formation of blood clots.
The hirudin substance possesses such properties. It is secreted in the salivary glands of leeches and is a natural heparin. In nature, it is also found in bee venom and some species of snake. Currently, artificially synthesized hirudin has been created. However, compared with natural, its effectiveness is several times lower.
By chemical nature, this substance is a polypeptide chain, which consists of amino acid residues. It stops the activity of the thrombin enzyme, thereby stopping blood coagulation.
The effect of hirudin extends to the blood, which is located in the digestive system of leeches. It can be stored for a long time in special extensions of the intestines. If necessary, this can continue up to six months. Therefore, the leech can be fed again after a long period of time.
Mechanism of action
Leech bites stimulate the human immune system. How is this possible? Hirudin causes the release of blood lymph. As a result, the lymph nodes become irritated and lymphocytes begin to stand out. These are blood cells that have a protective effect - increase local and general immunity.
The body perceives this situation as a threat. Therefore, there is a mobilization of its protective functions. The ability of phagocytic cells to digest foreign microorganisms increases dramatically.
Hirudotherapy is used to reduce and normalize blood pressure. Moreover, the result remains for several days.
The ability of leeches to break down lipids is widely used, which significantly reduces the manifestation of signs of atherosclerosis. Such activity is used as a means to combat cellulite.
But especially important leeches in the fight against blood clots. This is due to the fact that the hirudin interrupts some links in the process of their formation. But if blood clots have already formed, this substance contributes to their gradual dissolution. As a result, vascular patency is normalized.
As a result
The leech, the structure of which we examined in our article, is a representative of the type of annelid worms. The habitat of these animals is fresh water bodies and moist soils. Leeches have long been used for medical purposes. Their salivary glands contain a special substance - hirudin. Its main property is to prevent blood coagulation and the formation of blood clots inside the vessels.
Animals of the class Leeches have the following characteristics:
- the body is flattened in the dorso-abdominal direction;
- the presence of the oral and posterior suction cups;
- the absence of bristles on the integument, which are represented by inextensible cuticles;
- all representatives are hermaphrodites with a direct type of development;
- by type of food they are predators, parasites or blood-sucking species.