Animals, suborder earthworms. Body earthworm consists of annular segments, the number of segments can reach up to 320. When moving, earthworms rely on short bristles that are located on body segments. When studying the structure of an earthworm, it is clear that, unlike the whipworm, its body looks like a long tube. Earthworms are distributed throughout the planet, except for Antarctica.

Appearance

Adult earthworms are 15 - 30 cm in length. In the south of Ukraine, it can reach and large sizes. The body of the worm is smooth, slippery, has a cylindrical shape and consists of piece rings - segments. This form of the body of the worm is explained by the way of its life, it facilitates movement in the soil. The number of segments can reach 200. The ventral side of the body is flat, the dorsal side is convex and darker than the ventral side. Approximately where the front of the body ends, the worm has a thickening called a girdle. It contains special glands that secrete a sticky liquid. During reproduction, an egg cocoon is formed from it, inside which the eggs of the worm develop.

Lifestyle

If you go out into the garden after rain, you can usually see small piles of earth thrown out by earthworms on the path. Often at the same time, the worms themselves crawl along the path. It is because they appear on the surface of the earth after rain that they are called rain. These worms crawl out to the surface of the earth also at night. Usually the earthworm lives in humus-rich soil and is not distributed on sandy soils. He also does not live in swamps. Such features of its distribution are explained by the way of breathing. The earthworm breathes on the entire surface of the body, which is covered with mucous, moist skin. Too little air is dissolved in the water, and therefore the earthworm suffocates there. He dies even faster in dry soil: his skin dries up, and breathing stops. In warm and humid weather, earthworms stay closer to the surface of the earth. During prolonged droughts and cold period they crawl deep into the ground.

moving

The earthworm moves by crawling. At the same time, it first draws in the anterior end of the body and clings with the bristles located on the ventral side to the unevenness of the soil, and then, contracting the muscles, pulls up the posterior end of the body. Moving underground, the worm makes its own passages in the soil. At the same time, he pushes the earth apart with the pointed end of the body and squeezes between its particles.

Moving in dense soil, the worm swallows the earth and passes it through the intestines. The worm usually swallows the earth at a considerable depth, and throws it out through the anus at its mink. So on the surface of the earth long "laces" of earth and lumps are formed, which can be seen in the summer on garden paths.

This method of movement is possible only in the presence of well-developed muscles. Compared to the hydra, the earthworm has more complex musculature. She lies under his skin. Muscles together with the skin form a continuous musculocutaneous sac.

The muscles of the earthworm are arranged in two layers. Beneath the skin lies a layer of circular muscles, and beneath them is a thicker layer of longitudinal muscles. Muscles are made up of long contractile fibers. With the contraction of the longitudinal muscles, the body of the worm becomes shorter and thicker. When the circular muscles contract, on the contrary, the body becomes thinner and longer. Contracting alternately, both layers of muscles cause the movement of the worm. Muscle contraction occurs under the influence of the nervous system, branching out in muscle tissue. The movement of the worm is greatly facilitated by the fact that there are small bristles on its body from the ventral side. They can be felt by running a finger dipped in water along the sides and along the ventral side of the worm's body, from the rear end to the front. With the help of these bristles, the earthworm moves underground. With them, he lingers when he is pulled out of the ground. With the help of bristles, the worm descends and rises along its earthen passages.

Nutrition

Earthworms feed mainly on half-decayed plant remains. They drag, usually at night, leaves, stems and other things into their minks. Earthworms also feed on humus-rich soil, passing it through their intestines.

Circulatory system

The earthworm has a circulatory system that the hydra does not have. This system consists of two longitudinal vessels - dorsal and abdominal - and branches that connect these vessels and carry blood. The muscular walls of the vessels, contracting, drive blood throughout the body of the worm.

The blood of the earthworm is red, it is very important for the worm, as well as for other animals. With the help of blood, the connection between the organs of the animal is established, metabolism occurs. Moving through the body, it carries nutrients from the digestive organs, as well as oxygen entering through the skin. At the same time, the blood carries carbon dioxide out of the tissues into the skin. Various unnecessary and harmful substances formed in all parts of the body, together with the blood, enter the excretory organs.

Irritation

The earthworm does not have special sense organs. He perceives external stimuli with the help of the nervous system. The earthworm has the most developed sense of touch. Sensitive tactile nerve cells are located all over the surface of his body. Earthworm sensitivity to different kind external irritation is quite large. The slightest vibrations of the soil make him quickly hide, crawling into a mink or into deeper layers of soil.

The value of sensitive skin cells is not limited to touch. It is known that earthworms, without having special bodies vision, yet perceive light stimuli. If at night you suddenly illuminate the worm with a lantern, it quickly hides.

The response of an animal to stimulation, carried out with the help of the nervous system, is called a reflex. There are different types of reflexes. The contraction of the body of the worm from touch, its movement when suddenly illuminated by a lantern, has a protective value. This is a protective reflex. Grabbing food is a digestive reflex.

Experiments also show that earthworms smell. The sense of smell helps the worm find food. Charles Darwin also established that earthworms can smell the leaves of the plants they feed on.

reproduction

Unlike the hydra, the earthworm reproduces exclusively sexually. asexual reproduction he doesn't have. Each earthworm has male organs - the testes, in which the gums develop, and the female genital organs - the ovaries, in which the eggs are formed. The worm lays its eggs in a slimy cocoon. It is formed from a substance secreted by the girdle of the worm. In the form of a clutch, the cocoon slides off the worm and is pulled together at the ends. In this form, the cocoon remains in the earthen burrow until young worms emerge from it. The cocoon protects the eggs from moisture and other adverse effects. Each egg in the cocoon divides many times, as a result of which tissues and organs of the animal are gradually formed, and, finally, small worms similar to adults emerge from the cocoons.

Regeneration

Like hydras, earthworms are capable of regeneration, in which lost parts of the body are restored.

Earthworm belongs to the group annelids. He doesn't have any special bodies, designed specifically for gas exchange, and gas exchange occurs by diffusion through the entire surface of the body. In essence, they do not need specialized organs, since, due to the cylindrical shape of the body, their surface area to volume ratio is large, and with their relatively low activity, they do not consume so much oxygen.

However, in annelids there is a circulatory system (unlike some simpler animals and unicellular organisms), and the respiratory pigment hemoglobin is dissolved in their blood. Contractions of large blood vessels drive the blood along with the gases dissolved in it throughout the body; this also contributes to the maintenance of steep diffusion gradients.

Thin skin of an earthworm(cuticle) is constantly moistened by the secretion of the glands located in the epithelium. Capillaries are located in the epithelium directly under the cuticle. The distance between the blood vessels and the surface of the body is small and this ensures the rapid diffusion of oxygen into the blood. Earthworms are practically not protected from drying out and therefore try to stay only in a humid environment.

Respiratory system of insects - locusts.

In insects, gas exchange carried out through a system of tubes, the so-called trachea. Such a system allows oxygen to flow from the air directly to the tissues and there is no need to transport it through the blood. It's much more fast way than the diffusion of dissolved oxygen through tissues; such gas exchange creates conditions for a high metabolic rate.

spiracles- paired openings on the second and third thoracic and on the first eight abdominal segments of the insect's body lead to the air cavities. Branched tubes - tracheas - depart from these cavities. Each trachea is lined with epithelium secreting a thin layer of chitinous material. Usually this rigid layer is further reinforced by spiral and annular thickenings, due to which the airways remain open, even if the pressure in the lumen of the trachea is negative (compare with the cartilaginous rings in the human trachea and bronchi). In each segment of the body, the tracheae branch into numerous smaller tubes called tracheoles; tracheoles also branch, penetrating the tissues of the insect, and in the most active tissues, for example, in the flying muscles, they end blindly inside individual cells. The degree of branching of the tracheoles can vary depending on the metabolic needs of the tissues.

chitin lining in tracheoles is absent. At rest, they are filled with a watery fluid; at this time, oxygen diffuses through them to the tissues (and CO 2 - in the opposite direction) at a rate that is quite sufficient to satisfy the needs of the insect. In the active state, increased metabolic activity of the muscles leads to the accumulation of certain metabolites, in particular lactic acid, and the osmotic pressure in the tissues increases accordingly. When this happens, the fluid from the tracheoles is partially absorbed into the tissues by osmotic forces, and more air enters the tracheoles, and therefore more oxygen, and this oxygen is supplied directly to the tissues just when they need it.

The total flow of air passing through the body of an insect is regulated by a mechanism closing spiracles. The opening of each spiracle is equipped with a system of valves controlled by very small muscles. The edges of this opening are covered with hairs, which prevent foreign particles from entering the spiracles and prevent excessive loss of moisture. The size of the hole is adjusted depending on the amount of CO 2 in the body of the insect.

Increased activity leads to increased formation of CO 2 . Chemoreceptors catch it and the spiracles open. The same stimulus can also cause ventilation movements of the body, especially in large insects such as locust. Dorsoventral muscles, contracting, make the body of the insect flatter, as a result of which the volume of the tracheal system decreases and air is pushed out of it (“exhalation”). The suction of air ("inhalation") occurs passively, when the segments of the body, due to their elasticity, take their original shape.

According to some data, thoracic and abdominal spiracles open and close alternately, and this, combined with the ventilation movements of the body, creates a unidirectional airflow that enters the body of the insect through thoracic region and exits through the abdomen.

Tracheal system, of course, is very effective in terms of gas exchange, however, it should be borne in mind that gas exchange is determined in most insects solely by the diffusion of oxygen through the tissues of the insect. Diffusion, on the other hand, is known to be effective only at short distances, and this imposes severe limits on the size that insects can reach. These small distances, at which diffusion is sufficiently effective, do not exceed 1 cm; therefore, although insects up to 30 cm long are found, their body should not be more than 2 cm thick.

annelids have the following aromorphoses: 1. The body was divided into segments (metamers) with repeating sets internal organs. 2. A secondary cavity appeared - the whole, which has its own mesodermal lining. 3. There was a further complication of the nervous system: concentration nerve cells on the ventral side in each segment (the ventral nerve chain formed), a significant increase in the brain ganglia (nodes) (supraesophageal, subesophageal nerve ganglia, peripharyngeal ring). 4. A closed circulatory system arose, which ensured the rapid transport of substances throughout the body. 5. Appeared respiratory system, which increased the respiratory surface and the intensity of gas exchange. 6. Made it harder digestive system: there was a differentiation of the middle intestine into sections, which led to step by step process digestion. 7. Parapodia formed - limbs for movement. 8. There was a further complication of the excretory organs: a metanephridial multicellular excretory system was formed.

• Earthworm

Earthworm – Lumbricus terrestris(type Annelids, class Small-bristle worms, Lumbricidae family) lives in moist, humus-rich soil. It feeds on organic matter, passing earth with plant debris through the intestines. Ch. Darwin also noted useful influence earthworms on soil fertility. Dragging the remains of plants into the mink, they enrich it with humus. Laying passages in the soil, they contribute to the penetration of air and water to the roots of plants.

Earthworms are active warm time of the year. In winter they hibernate. Freezing kills worms instantly, so they must burrow deeper into the ground where low temperatures do not penetrate. In the spring, when the temperature reaches a suitable value and the ground is saturated with rainwater, they have a mating season. They reproduce very quickly, producing about a hundred young worms a year. In summer, the worms are not so active. Food - dying plant residues - is very scarce at this time, and the soil is devoid of moisture, which can cause the death of worms. The autumn period is again characterized by the activity of worms. At this time, the reproduction of offspring begins again, which lasts until the onset of winter.

Earthworms live relatively long lives. Some manage to live for about ten years if they do not become victims of birds and moles. Another threat to their lives is the pesticides so widely used in horticulture today.

So, the Earthworm has an elongated, cylindrical body from 10 to 30 cm long. dorsal side more rounded, it is darker, a dorsal blood vessel shines through its skin. Abdominal side somewhat flattened and lighter colored. The anterior end of the body is thicker and darker colored. The body is made up of rings segments. In an adult worm, their number reaches 200. In the area of ​​\u200b\u200b32-37 body segments there is belt rich in mucous glands. External segmentation corresponds to the division of the body cavity by partitions into separate chambers and the segment-by-segment (i.e., in each segment) arrangement of a number of internal organs. On each segment 8 bristles(they are easy to detect if you run your finger along the body of the worm in the direction from the rear end of the body to the front). The setae are arranged in four pairs on the lateral sides of the segments. Clinging to the unevenness of the soil with them, the worm moves forward with the help of the muscles of the skin-muscular sac.

Covers. The body of an earthworm is covered skin-muscle sac. He is educated cuticle, single layer epithelium and two layers of muscles - external ring and internal longitudinal. The skin epithelium of the worm is rich mucous pieces of iron that produce slime covering the entire body of the worm and protecting it from drying out. The mucus also makes it easier to crawl in burrows by reducing friction on the soil.

Earthworm movement. When the worm crawls, waves run through its body muscle contractions, and both the length and thickness of individual sections of his body are constantly changing. The movements produced by each part of the body consist in the fact that the segments that make up it are either stretched out and at the same time become thinner, then they contract and become thicker. As a result of such alternating extensions and contractions, the worm gradually moves forward: first, its head end is extended forward, and then the posterior segments of the body are gradually pulled towards it; after this, the rear end of the body remains in place, and the head end sticks even further forward, and thus the further advancement of the worm continues (it is convenient to observe it by letting the worm crawl along the paper spread on the table).

• body cavity. Inside the skin-muscular sac in annelids is located secondary cavity body, or in general. This body cavity is not limited by muscles, as in roundworms, but has its own epithelial(coelomic) pavement, i.e. inner side longitudinal muscles is lined with epithelium of mesodermal origin, and there is also an epithelial lining on the side of the intestine lying in the body cavity. Due to the coelomic epithelium, internal two-layer transverse partitions are formed between the segments - dissipations. The secondary cavity is divided into chambers, each segment contains a pair of coelomic sacs. The coelomic fluid is under pressure and plays a role hydroskeleton, so the worm is elastic to the touch.

Digestive system consists of front, middle and rear guts. Mouth located on the second segment on the ventral side of the body. anal hole

type Annelids Earthworm

At the posterior end of the body, it looks like a small gap. Due to the nutrition of rotting plant remains and humus, the digestive system has a number of features. Its anterior section is differentiated into a muscular throat, esophagus, goiter and muscular stomach. To increase the suction surface, a fold has formed on the upper part of the intestine typhlosol(typhlozolis). Please note: differentiated parts of the foregut - pharynx, esophagus, goiter, stomach - were absent in previous types of worms.

Breath. An earthworm breathes over the entire surface of its body due to the presence of a dense subcutaneous network of capillary blood vessels. Therefore, it is important that the integuments of the worm's body do not dry out, but excessive moisture (for example, very wet soil after rain) is just as detrimental to them.

Circulatory system closed, that is, the blood moves through the vessels without spilling into the body cavity. The movement of blood is determined by the pulsation of large vessels, mainly encircling the esophagus. These are kind of hearts. Blood supplies all organs and tissues with nutrients, transporting them from the intestines, and oxygen entering the capillaries of the skin from external environment. By dorsal vessel blood moves from the back end of the body to the front, and along abdominal vessel- in the opposite direction. The blood of an earthworm is red. An iron-containing protein, close to vertebrate hemoglobin and transporting oxygen, is contained in a dissolved state in the blood plasma, and erythrocytes are absent.

Nervous system more complex than that of flat and roundworms. It consists of nerve parapharyngeal ring with ganglia and abdominal nervous chains. This so-called nervous system ladder type. supraesophageal double ganglion performs the functions of the brain and is more developed than subesophageal. The nerve chain originates from the subpharyngeal node and is a segment-by-segment pairs of nerve nodes, connected to each other by transverse and longitudinal commissures. From the ganglia, nerves depart to various organs. The sense organs are poorly developed in the earthworm: eyes and tentacles are absent, but numerous sensory cells and nerve endings are embedded in their skin.

excretory organs are presented segment by segment (i.e., in each segment) by located paired metanephridia. They look like convoluted tubules, begin in the body cavity with a funnel with cilia. A channel departs from the funnel, which penetrates the transverse partition, passes into the cavity of the next segment. The final department of metanephridium has an extension - uric bubble, which opens outward on the lateral side of the body of the worm (i.e., each segment has a pair of very small excretory openings). In addition to metanephridia, the excretion involves chloragogenic cells covering the intestinal surface with a thin brown-yellow coating. Chlorogenic cells accumulate excretion products. Filled with metabolic products, these cells die, and their contents enter the body cavity, from where they are removed by metanephridia.

Reproduction. earthworms hermaphrodites. The reproductive organs and the girdle can only be seen during the breeding season - in the spring. To male

type Annelids Earthworm

reproductive system include two pairs of testicles located in segments 10 and 11, four vas deferens, which merge in pairs and open outward doubles male sexual hole located in segment 15. The female reproductive system includes pair ovaries located in segment 13, oviducts, which open outward in segment 14 couple women's genital holes. There are two pairs in segments 9 and 10 seminal receptacles, each of which opens outwards with an independent opening.

Earthworms reproduce sexually. Cross fertilization, in a cocoon. Two worms meet, wrap their bodies tightly around each other, attach themselves to each other with their ventral sides and exchange sperm, which enters the spermatic receptacles. After that, the worms disperse. Further, the girdle forms a mucous sleeve, eggs are laid in it. When the clutch is advanced through the segments containing the seed receptacles, the eggs are fertilized by sperm belonging to another individual. The clutch is shed through the front end of the body, compacted and turns into an egg cocoon, where young worms develop.

Regeneration. Earthworms are characterized by a high ability to regenerate, i.e. from each piece of the torn body of an earthworm, a whole worm is restored.

Questions for self-control

Name aromorphoses of the type Annelids.

Name the classification of the type Annelids.

What is the systematic position of the earthworm?

Where do earthworms live?

What body shape do earthworms have?

What is the body of an earthworm covered with?

What body cavity is characteristic of an earthworm?

What is the structure of the worm's digestive system?

What is the structure of the circulatory system of the worm?

How does an earthworm breathe?

What is the structure of the excretory system of the worm?

What is the structure of the worm's nervous system?

What structure does reproductive system earthworm?

How does an earthworm reproduce?

What is the significance of the earthworm?

type Annelids Earthworm

Rice. Earthworm, its moves in the ground and movement.

Rice. The internal structure of the earthworm.

1, 16 - gut; 2 - partitions; 3 - epithelial lining of the secondary body cavity; 4 - dorsal (back) blood vessel; 5 - annular blood vessel; 6 - skin-muscular sac; 7 - cuticle; 8 - skin epithelium; 9 - whole; 10 - metanephridium; 11 - eggs; 12 - circular muscles; 13 - longitudinal muscles; 14 - ventral (abdominal) blood vessel; 15 - abdominal nerve chain.

type Annelids Earthworm

Rice. The structure of the anterior end of the body of an earthworm.

The prostomium is a protrusion of the upper part of the first segment that covers the mouth. The peristomium is the name of the first segment of the body.

type Annelids Earthworm

Rice. The structure of the earthworm.

A - head end; B - internal structure; B - nervous system.

1 - mouth opening; 2 - male genital opening; 3 - female genital opening; 4 - belt; 5 - pharynx; 6 - esophagus; 7 - goiter; 8 - stomach; 9 - intestines; 10 - dorsal blood vessel; 11 - annular blood vessels; 12 - abdominal blood vessel; 13 - metanephridia; 14 - ovaries; 15 - testes; 16 - seed bags; 17 - seed receptacles; 18 - peripharyngeal ganglion; 19 - peripharyngeal nerve ring; 20 - abdominal nerve chain; 21 - nerves.

type Annelids Earthworm

Rice. Longitudinal section of the body of an earthworm.

1 - mouth; 2 - throat; 3 - esophagus; 4 - goiter; 5 - stomach; 6 - gut; 7 - peripharyngeal ring; 8 - abdominal nerve chain; 9 - "hearts"; 10 - dorsal blood vessel; 11 - abdominal blood vessel.

Rice. Reproduction of the earthworm.

1 - mucous sleeve; 2 - cocoon; 3 - exit of young worms from the cocoon.

type annelids

Rice. Structure polychaete worm Nereids.

type annelids

Rice. Appearance of a medical leech.

Necatoriasis is a helminthic invasion, characteristic of countries with a warm climate. It affects the organs of the gastrointestinal tract, lungs and circulatory system, causing severe complications in the absence of competent and timely treatment. How does the disease manifest itself, by what methods is it recognized, and is it possible to protect yourself from necatoriasis?

Description of the disease

Today, necatoriasis is common, mainly in Africa, South America and some Asian countries. Helminths for the next period of development need warm, moist soil, therefore, in temperate climate they don't live. And the risk of contracting necatoriasis in Russia is minimal (only in exceptional cases: for example, during a blood transfusion).

Pathogen

Infection with necatoriasis most often occurs through contaminated soil. If a person walks barefoot on it, the larvae can attach to the skin flakes, and then penetrate through the microcracks and reach circulatory system. You can also become infected by eating unwashed fruits and vegetables.

Symptoms

Symptoms of necatorosis can be divided into groups, depending on which stage life cycle helminth passes. But general state weakness almost always persists.

If a child (under 6 years of age) has contracted necatoriasis, there is a risk of a decrease in his mental development due to anemia. The kid will become lethargic and irritable, lose interest in learning and games. It is urgent to show the child to the doctor so as not to start the process.

Curious! Necatoriasis has another characteristic symptom inherent in black people. Their skin may become pigmented, i.e. lighten up in places.

Diagnostics

Additional research methods (X-ray, fluorography, MRI) are used to diagnose not so much necatorosis as complications that have developed as a result of a long course of invasion.

Treatment

Treatment of necatorosis, as well as other helminthic invasions, is based on the principle of deworming. Those. it is necessary to drive the worms out of the body. This can be done with the help of anthelmintic drugs. To destroy nematodes, use:

• Vermox;
• Naftamon;
• Decaris.

All of these drugs are highly toxic. On the one hand, this is good, because the treatment will last only a few days, and all helminths will die. But on the other hand, it will bring a lot side effects, including vomiting, diarrhea, nervousness and other similar manifestations of necatorosis itself.

Auxiliary treatment is necessary to restore the body. The patient is prescribed Hemofer, Ferronal or other medicines to replenish the level of iron in the blood. Antihistamines are necessary for those who suffer allergic manifestations necatorosis. In some cases, you have to resort to hormone therapy. It is possible to say that necatoriasis has been completely cured only after three “clean” analyzes taken within a month.

Prevention

In tropical countries, prevention is intensified: you should not walk barefoot on the ground and drink water from dubious sources. Better to buy bottled. In order not to become infected with necatoriasis in Russia, you do not need to walk near Wastewater, because the sewage waste may contain the feces of an infected person who has recently arrived from a southern country.