Earthworm (characteristics and structure). How do earthworms move? The role of the earthworm in nature How a worm breathes

Earthworms , they are earthworms , this is not just one species, but a whole suborder of the class Oligochaete worms, belonging to the type Annelids. For earthworm most of the structural features of its type and class are characteristic.

Earthworms are ubiquitous. Our area is home to more than a dozen similar friends on another species (European earthworms), the body length of which is 10-20 cm, the number of segments is 100-180. At the same time, the Australian earthworm can reach a length of 3 meters.

During the day, earthworms crawl in the soil. At night and after rain they can come to the surface. With the onset of cold weather, they go underground, to a depth of 2 m. The back of the body is slightly flattened. When crawling out of the soil, the worm holds the edge of the hole with its rear end.

The body of an earthworm, as a representative of annelids, is divided into segments by ring constrictions. As in all oligochaetes, the parapodia are reduced, only tufts of bristles are preserved from them, which allow the worm to cling, rest against the ground and facilitate pushing the body forward. In other words, the bristles provide adhesion to the substrate.

The surface of the body is moist and covered with mucus, which facilitates movement in the soil and also facilitates the penetration of oxygen into the body.

The epithelium secretes a layer of transparent cuticle and also contains many mucous cells. Under the epithelium there are circular and longitudinal muscles. The body of an earthworm can contract and elongate. Circular muscles make the body of the worm thin and long, longitudinal muscles shorten and thicken. The longitudinal layer of muscles is more powerful. Alternate contraction of these muscles ensures movement. Each segment can change its shape separately.

The coelomic sacs of adjacent segments communicate with each other, thus the liquid in them mixes.

An earthworm often swallows soil, eating its way through. Nutrient particles are absorbed from the soil in the intestines. If the soil is soft, then it drills it with the front end. First, the front end is stretched and thinned, inserted between lumps of soil. Then the front end thickens, causing the soil to move apart. Next, the worm pulls up the back of the body.

They feed on rotting plant debris. In addition, they can drag fallen leaves from the surface. By dragging plant debris into the soil, worms contribute to their decomposition and the formation of fertile soil.

The digestive system consists of the mouth, pharynx, esophagus, crop, gizzard, midgut, hindgut, and anus. Swallowing food is done through the muscular pharynx. The stomach grinds food; in addition to the muscles of the walls, swallowed grains of sand are involved in this. On the dorsal side, the wall of the midgut forms an invagination, increasing the absorption surface. The midgut is lined with ciliated epithelium, in which there are many unicellular glands. It breaks down complex organic matter, simpler substances are absorbed into the blood. In the walls of the earthworm's midgut there is a dense network of blood vessels. The hindgut is small and ends at the anus.

A special feature of earthworms are calcareous glands, whose ducts flow into the esophagus. The substances they release neutralize the acids contained in the soil.

Breathing occurs over the entire surface of the skin. In the superficial layers of the body wall there is a dense network of blood vessels. When it rains, earthworms crawl to the surface due to lack of air in the soil.

The circulatory, nervous and excretory systems are similar to polychaetes. However, in the circulatory system there are so-called “hearts” - annular vessels capable of muscular contraction. Located in segments 7-13. In a number of species, ring vessels are present only in the anterior part of the body.

There are no metanephridia (excretory organs of annelids) in the anterior three segments.

Sense organs are poorly developed. The skin contains sensitive cells - organs of touch. There are also cells in the skin that perceive the degree of illumination.

Earthworms are hermaphrodites. The reproductive system is located in several segments of the anterior part of the body. The testes are located in front of the ovaries.

Mutual cross fertilization. Each of the mating worms transfers sperm to the partner's seminal receptacle.

In the first third of the body of earthworms there is a special belt; its glandular cells secrete mucus, which, when dried, forms a muff. Unfertilized eggs are laid in it. After mating, spermatozoa enter from the seminal receptacles. Fertilization occurs. After this, the sleeve slides off the worm's body and turns into a cocoon. Small worms develop from the eggs.

Capable of regeneration. If a predator tears off part of the worm's body, the other half completes the missing part. If the worm is divided into two parts, then you get two individuals, which can be considered asexual reproduction. However, the earthworm itself does not reproduce this way.

In the world of fauna is the earthworm. He can rightfully be called an earth worker, since it is thanks to him that the soil on which we walk is completely saturated with oxygen and other minerals. By passing through various sections of the ground lengthwise and crosswise, this worm makes them loose, which then makes it possible to plant cultivated plants there, as well as to do gardening.

General characteristics of the species

The earthworm belongs to the kingdom Animalia, to the subkingdom Multicellular. Its type is characterized as Ringed, and its class is Oligochaete. The organization of annelids is very high compared to other types. They have a secondary body cavity, which has its own digestive, circulatory and nervous systems. They are separated by a dense layer of mesoderm cells, which serve as a kind of airbag for the animal. Also, thanks to them, each individual segment of the worm’s body can exist autonomously and progress in development. The habitats of these earthly orderlies are wet soil, salty or fresh water.

External structure of an earthworm

The worm's body is round in shape. The length of representatives of this species can be up to 30 centimeters, which can include from 100 to 180 segments. The front part of the worm's body has a small thickening in which the so-called genital organs are concentrated. Local cells are activated during the breeding season and perform the function of laying eggs. The lateral outer parts of the worm's body are equipped with short bristles, completely invisible to the human eye. They allow the animal to move in space and move through the ground. It is also worth noting that the earthworm’s tummy is always painted in a lighter tone than its back, which has a dark burgundy, almost brown color.

What is he like from the inside?

The structure of the earthworm differs from all other relatives by the presence of real tissues that form its body. The outer part is covered with ectoderm, which is rich in mucous cells containing iron. This layer is followed by muscles, which are divided into two categories: circular and longitudinal. The former are located closer to the surface of the body and are more mobile. The latter are used as auxiliary during movement, and also allow internal organs to work more fully. The muscles of each individual segment of the worm's body can function autonomously. When moving, the earthworm alternately compresses each ring group of muscles, as a result of which its body either stretches or becomes shorter. This allows him to dig new tunnels and fully loosen the ground.

Digestive system

The structure of a worm is extremely simple and understandable. It originates from the mouth opening. Through it, food enters the pharynx and then passes through the esophagus. In this segment, products are purified from acids released by rotting products. The food then passes through the crop and into the stomach, which contains many small muscles. Here the products are literally ground up and then enter the intestines. The worm has one midgut, which goes into the posterior opening. In its cavity, all useful substances from food are absorbed into the walls, after which waste leaves the body through the anus. It is important to know that earthworm excrement is rich in potassium, phosphorus and nitrogen. They perfectly nourish the earth and saturate it with minerals.

Circulatory system

The circulatory system possessed by an earthworm can be divided into three segments: the abdominal vessel, the dorsal vessel and the annular vessel, which combines the previous two. The blood flow in the body is closed, or circular. The annular vessel, which is shaped like a spiral, unites two vital arteries for the worm in each segment. Capillaries also branch from it, which come close to the outer surface of the body. The walls of the entire annular vessel and its capillaries pulsate and contract, due to which blood is driven from the abdominal artery to the spinal artery. It is noteworthy that earthworms, like humans, have red blood. This is due to the presence of hemoglobin, which is regularly distributed throughout the body.

Breathing and the nervous system

The earthworm's breathing process occurs through the skin. Each cell of the outer surface is very sensitive to moisture, which is absorbed and processed. It is for this reason that worms do not live in dry sandy areas, but live where the soil is always filled with water or in the reservoirs themselves. The nervous system of this animal is much more interesting. The main “lump”, in which all neurons are concentrated in huge numbers, is located in the anterior segment of the body, but its analogues, smaller in size, are present in each of them. Therefore, each segment of the worm’s body can exist autonomously.

Reproduction

Let us immediately note that all earthworms are hermaphrodites, and in each organism the testes are located in front of the ovaries. These seals are located in the front part of the body, and during the mating period (and it is cross-breeding), the testes of one of the worms pass into the ovaries of the other. During the mating period, the worm secretes mucus, which is necessary for the formation of a cocoon, as well as a protein substance that will feed the embryo. As a result of these processes, a mucous membrane is formed in which embryos develop. Afterwards they leave it, back end first, and crawl into the ground to continue their lineage.

Annelids have the following aromorphoses: 1. The body was divided into segments (metameres) with repeating sets of internal organs. 2. A secondary cavity has appeared - the coelom, which has its own mesodermal lining. 3. There was a further complication of the nervous system: the concentration of nerve cells on the abdominal side in each segment (the abdominal nerve chain was formed), a significant increase in the cerebral ganglia (nodes) (supraglottic, subpharyngeal nerve ganglia, peripharyngeal ring). 4. A closed loop has arisen circulatory system, ensuring rapid transport of substances throughout the body. 5. Appeared respiratory system, increasing the respiratory surface and the intensity of gas exchange. 6. More complicated digestive system: differentiation of the midgut into sections occurred, which led to a staged process of digestion. 7. Parapodia were formed - limbs for movement. 8. Further complication of the excretory organs occurred: a metanephridial multicellular excretory system.

Earthworm

Earthworm – Lumbricus terrestris(type Annelids, class Oligochaetes, family Lumbricidae) lives in moist, humus-rich soil. It feeds on organic matter, passing soil and plant debris through its intestines. Even Charles Darwin noted the beneficial effect of earthworms on soil fertility. By dragging the remains of plants into the burrows, they enrich it with humus. By making passages in the soil, they facilitate the penetration of air and water to the roots of plants.

Earthworms are active in warm time of the year. In winter they hibernate. Freezing kills the 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 level and the ground is saturated with rainwater, their mating season begins. They reproduce very quickly, producing about a hundred young worms per year. In summer, worms are not as active. There is very little food - dying plant debris - at this time, and the soil is deprived of moisture, which can cause the death of worms. Autumn period again characterized by worm activity. At this time, reproduction of offspring begins again, which lasts until the onset of winter.

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

So, the earthworm has an elongated, cylindrical body from 10 to 30 cm long. Dorsal side more rounded, it is darker, the dorsal blood vessel is visible through its skin. Abdominal side somewhat flattened and lighter colored. The anterior end of the body is thicker and darker in color. The body consists of rings - segments. In an adult worm, their number reaches 200. In the area of 32-37 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 segmental (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 uneven soil, the worm moves forward with the help of the muscles of the skin-muscular sac.

Veils. The earthworm's body is covered skin-muscle bag. He is educated cuticle, single layer epithelium and two layers of muscles - external circular and internal longitudinal. The skin epithelium of the worm is rich mucous glands, which produce slime, covering the entire body of the worm and protecting it from drying out. Mucus also makes crawling in burrows easier by reducing friction with the soil.

Movement of an earthworm. When a worm crawls, waves of muscle contractions run through its body, and both the length and thickness of individual parts of its body are constantly changing. The movements produced by each part of the body consist in the fact that its constituent segments either stretch and become thinner, or contract and become thicker. As a result of such alternating stretching and contraction, the worm gradually moves forward: first, its head end is pulled 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 is pushed even further forward, and thus the further advancement of the worm continues (it is convenient to observe it by letting the worm crawl along paper spread on the table).

Body cavity. Inside the skin-muscle sac of annelids there is secondary cavity body, or in general. This body cavity is not limited by muscles, as in roundworms, but has its own epithelial(coelomic) lining, i.e. the inner side of the 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 - dissepiments. The secondary cavity is divided into chambers, each segment containing a pair of coelomic sacs. The coelomic fluid is under pressure and plays a role hydroskeleton, so the worm feels elastic to the touch.

Digestive system comprises front, average 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 slit. Due to feeding on rotting plant remains and humus, the digestive system has a number of features. Its anterior section is differentiated into muscular throat, esophagus, goiter and muscular stomach. To increase the absorption surface, a fold has formed on the upper part of the intestine typhlosol(typhlozolis). Please note: differentiated sections of the foregut - pharynx, esophagus, crop, 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 worm’s body covers do not dry out, but excessive moisture (for example, very wet soil after rain) is just as destructive for them.

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

Nervous system more complex than that of flatworms and roundworms. It consists of peripharyngeal nerve ring with ganglia and abdominal nervous chains. This is the so-called nervous system ladder type. Suprapharyngeal doubles ganglion performs the functions of the brain and is more developed than subpharyngeal. The nerve chain originates from the subpharyngeal node and consists of segmentally located pairs of ganglia, connected to each other by transverse and longitudinal commissures. Nerves extend from the ganglia to various organs. The earthworm's sense organs are poorly developed: there are no eyes or tentacles, but their skin contains numerous sensory cells and nerve endings.

Excretory organs presented segment by segment (i.e. in each segment) arranged in pairs metanephridia. They look like convoluted tubes and begin in the body cavity as a funnel with cilia. A channel departs from the funnel, which penetrates the transverse septum and passes into the cavity of the next segment. The terminal section of the metanephridium has an extension - uric bubble, which opens outward on the side of the worm’s body (i.e., in each segment there is a pair of very small excretory holes). In addition to metanephridia, the secretion involves chloragogenous cells, covering the surface of the intestine 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 girdle can be examined only during the breeding season - in the spring. To male

type Annelids Earthworm

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

Earthworms reproduce sexually. Cross fertilization, in a cocoon. Two worms meet, tightly wrap their bodies around each other, attach their ventral sides to each other and exchange sperm, which ends up in the spermatic receptacles. After this, the worms disperse. Next, the belt forms a mucous muff, in which eggs are laid. As the coupling moves through the segments containing the spermatheca, the eggs are fertilized by sperm belonging to another individual. The muff is shed through the anterior end of the body, becomes 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 the aromorphoses of the annelid type.

Name the classification of the type Annelids.

What's it like systematic position 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 worm's circulatory system?

How does an earthworm breathe?

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

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

What structure does it have? reproductive system earthworm?

How does an earthworm reproduce?

What is the significance of an earthworm?

type Annelids Earthworm

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

Rice. Internal structure of an earthworm.

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

type Annelids Earthworm

Rice. The structure of the anterior end of the earthworm's body.

The prostomium is the protrusion of the upper part of the first segment, covering the mouth. Peristomium is the name of the first segment of the body.

type Annelids Earthworm

Rice. The structure of an 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 - ring blood vessels; 12 - abdominal blood vessel; 13 - metanephridia; 14 - ovaries; 15 - testes; 16 - seed sacs; 17 - seminal receptacles; 18 - peripharyngeal nerve node; 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 - pharynx; 3 - esophagus; 4 - goiter; 5 - stomach; 6 - intestine; 7 - peripharyngeal ring; 8 - abdominal nerve chain; 9 - “hearts”; 10 - dorsal blood vessel; 11 - abdominal blood vessel.

Rice. Reproduction of the Earthworm.

1 - mucous coupling; 2 - cocoon; 3 - emergence of young worms from the cocoon.

type annelids

Rice. Structure Polychaete worm Nereids.

type annelids

Rice. Appearance of a Medical leech.

Earthworm – Lumbricus terrestris(type Annelids, class Oligochaetes, family Lumbricidae) lives in moist, humus-rich soil. It feeds on organic matter, passing soil and plant debris through its intestines. Even Charles Darwin noted the beneficial effect of earthworms on soil fertility. By dragging the remains of plants into the burrows, they enrich it with humus. By making passages in the soil, they facilitate the penetration of air and water to the roots of plants.

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

Veils. The earthworm's body is covered skin-muscle bag. He is educated cuticle, single layer epithelium and two layers of muscles - external circular and internal longitudinal. The skin epithelium of the worm is rich mucous glands, which produce slime, covering the entire body of the worm and protecting it from drying out. Mucus also makes crawling in burrows easier by reducing friction with the soil.

Body cavity. Inside the skin-muscle sac of annelids there is secondary body cavity, or in general. This body cavity is not limited by muscles, like in roundworms, but has its own epithelial(coelomic) lining, i.e. the inner side of the 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 - dissepiments. The secondary cavity is divided into chambers, each segment containing a pair of coelomic sacs. The coelomic fluid is under pressure and plays a role hydroskeleton, so the worm feels elastic to the touch.

Digestive system comprises front, average And hindgut. Mouth located on the second segment on the ventral side of the body. Anal hole

type Annelids Earthworm

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

Nervous system more complex than that of flatworms and roundworms. It consists of peripharyngeal nerve ring with ganglia and abdominal nerve cord. This is the so-called nervous system ladder type. Suprapharyngeal paired ganglion performs the functions of the brain and is more developed than subpharyngeal. The nerve chain originates from the subpharyngeal node and consists of segmentally located pairs of ganglia, connected to each other by transverse and longitudinal commissures. Nerves extend from the ganglia to various organs. The earthworm's sense organs are poorly developed: there are no eyes or tentacles, but their skin contains numerous sensory cells and nerve endings.

Excretory organs presented segment by segment (i.e. in each segment) arranged in pairs metanephridia. They look like convoluted tubes and begin in the body cavity as a funnel with cilia. A channel departs from the funnel, which penetrates the transverse septum and passes into the cavity of the next segment. The terminal section of the metanephridium has an extension - bladder, which opens outward on the side of the worm’s body (i.e., in each segment there is a pair of very small excretory holes). In addition to metanephridia, the secretion involves chloragogenic cells, covering the surface of the intestine 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 girdle can be examined only during the breeding season - in the spring. To male

type Annelids Earthworm

the reproductive system includes two pairs of testes, located in segments 10 and 11, four vas deferens, which merge in pairs and open outwards paired male genital opening, located in the 15th segment. The female reproductive system includes pair of ovaries located in segment 13, oviducts, which open outwards in the 14th segment a pair of female genital orifices. There are two pairs in segments 9 and 10 spermatheca, each of which opens outward with an independent hole.

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 the aromorphoses of the annelid type.

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 worm's circulatory system?

How does an earthworm breathe?

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

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

What structure does the reproductive system of an earthworm have?

How does an earthworm reproduce?

What is the significance of an earthworm?

type Annelids Earthworm

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

Rice. Internal structure of an earthworm.

type Annelids Earthworm

Rice. The structure of the anterior end of the earthworm's body.

The prostomium is the protrusion of the upper part of the first segment, covering the mouth. Peristomium is the name of the first segment of the body.

type Annelids Earthworm

Rice. The structure of an earthworm.

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

type Annelids Earthworm

Rice. Longitudinal section of the body of an earthworm.

And the suborder of earthworms (Haplotaxida). Its body consists of ring-shaped segments, the number of which can reach 320! These animals are widespread in all corners of our planet. They are only absent in Antarctica. Very often children are interested in how earthworms move. In our article we will examine this issue in detail, and at the same time learn about them. appearance, lifestyle and method of reproduction.

Lifestyle of earthworms

If you walk through the garden in the morning or after rain, then, as a rule, you can see small piles of soil thrown out by worms on the ground, and in the puddles you can see them themselves. Due to the fact that these individuals crawl to the surface of the earth after rain, this name was assigned to them. (the photo above shows this invertebrate animal) also crawls onto the earth's surface at night. As a rule, it prefers soil rich in humus, so it is rarely found in sandstones. The earthworm does not like swampy soils. These features are explained physiological characteristics Lumbricidae. The fact is that worms breathe over the entire surface of their body, which is covered with a mucous epidermis. There is too little air dissolved in soil saturated with moisture. As a result, the earthworm suffocates there. By the way, this explains his behavior during the rain. Dry soil is also detrimental to representatives of Haplotaxida: their skin dries out and breathing stops. In wet and warm weather earthworms (the photo below shows Lumbricidae in all its glory) stay closer to the surface of the earth. With a decrease in temperature, as well as with the onset of a dry period, they crawl into the deeper layers of the soil.

earthworms

Adults reach 30 centimeters in length, although there are some larger specimens. The body of an earthworm is slippery, smooth, has a cylindrical shape, and consists of segments - piece rings. This constitution is explained by the way of life of Lumbricidae: such a structure facilitates the process of movement in the soil. The number of piecework rings reaches two hundred. The surface of the body, which could conventionally be called the back, is convex, the abdominal surface is flat and lighter. On the earthworm's body, where its front part ends, there is a thickening called the girdle. It contains special glands that secrete a sticky liquid. During reproduction, an egg cocoon is formed from the girdle, and eggs develop in it.

How do earthworms move?

Representatives of Haplotaxida crawl. First, they extend the front end of their body and cling to irregularities with special bristles, which are located on the ventral side of the rings. earth's surface. After this, the muscles contract, and the back one is pulled forward. The movement of a worm in the ground is characterized by the fact that it makes passages in the soil. At the same time, with the pointed end of its body, it pushes the earth apart, and then squeezes between its particles. It is also interesting how earthworms move in denser layers. As they move, they swallow soil and pass it through their intestines. Worms, as a rule, swallow soil at a considerable depth, and throw it out through the anus already at the top, near their own burrow. It can often be observed in the summer on the surface of the earth in the form of lumps and elongated “laces”.

Earthworm and its biology

Worms have well-developed muscles, which make this method of movement possible. Their muscles are located under the epidermis; in fact, they, together with the skin, form a kind of musculocutaneous sac. The muscles are located in two layers. Directly below the epidermis are the circular muscles, and below them is a second, thicker longitudinal layer (consisting of long contractile fibers). When the longitudinal muscles are compressed, the earthworm's body becomes thicker and shorter. When contracting the circular muscles, on the contrary, it is long and thin. The alternate contraction of both layers of muscles, carried out under the influence of the nervous system branching in the muscle tissue, determines the movement of Lumbricidae.

The movement of worms is greatly facilitated by the presence of small bristles on the lower part of the body. They can be felt if you run a wet finger along the abdomen of the worm from the rear to the anterior end. Thanks to these bristles, earthworms not only move in the soil, but also “grab” the ground when they are tried to be pulled out. They also help to rise and fall along already made earthen passages. With this we will finish dealing with the question of how earthworms move, and move on to no less interesting facts about the life of Lumbricidae.

Circulatory system

It consists of two longitudinal vessels - abdominal and dorsal, as well as branches connecting them. Due to muscle contraction of the walls, blood moves throughout the body. The blood of earthworms is scarlet. With its help, a connection is established between internal organs, and metabolism is also carried out. As the blood circulates, it carries nutritional compounds from the digestive organs, as well as oxygen coming from the skin. At the same time, carbon dioxide is removed from the tissues. In addition, the blood removes unnecessary and harmful compounds to the excretory organs.

Feeding earthworms

The basis of nutrition for representatives of Haplotaxida consists of half-rotten plant remains. As a rule, at night, earthworms drag leaves, stems, etc. into their burrows. In addition, they can pass humus-rich soil through their intestines.

Irritation of earthworms

Earthworms do not have any special features. They perceive external stimuli thanks to nervous system. Worms have a highly developed sense of touch. The nerve cells responsible for this are located over the entire surface of the skin. The sensitivity of earthworms is so great that the slightest vibrations in the soil force them to hide in burrows or in deeper layers of the earth as quickly as possible. However, the importance of sensitive nerve endings is not limited only to the function of touch. Scientists have found that with the help of these cells, earthworms are able to sense rays of light. So, if a flashlight beam is directed at a worm at night, then it will high speed will hide in a safe place.

The response of animals to any irritation, carried out thanks to the nervous system, is called a reflex. It is customary to distinguish between different types of reflexes. Thus, the contraction of the earthworm's body when touched, as well as its movement under sudden illumination, is a protective function. This is a protective reflex. Experiments by scientists have shown that earthworms can smell. They use their sense of smell to find food.

Reproduction

Earthworms reproduce sexually, although in general protostomes are hermaphrodites. Each member of Haplotaxida has male organs, which are called testes (sperm develop in them), as well as female organs, called ovaries (they produce eggs). The earthworm lays its eggs in a slimy cocoon. It is formed from a substance that is released through the belt. Next, the cocoon in the form of a muff slides off the body and is pulled together at the ends. It remains in the ground until the young worms emerge from it. The cocoon serves to protect eggs from dampness and other unfavorable influences.

What are worms for?

This section will be useful for those who think that earthworms are only needed for fishing. Of course, a fisherman has nothing to do on the river without them, but this is not all the benefit from representatives of Lumbricidae. The role of the earthworm in nature is so great that it cannot be overestimated. They promote the decomposition of organic matter in the soil. In addition, earthworms enrich the earth with the most valuable fertilizer - humus. They are also a kind of indicator: if the soil contains a lot of worms, it means it is fertile.

A full understanding of the role of Haplotaxida came to humanity relatively recently. However, even now many farmers prefer to use chemical fertilizers, despite the fact that they kill all living things. Today, an alternative to chemicals has been found - vermicompost and vermicompost. Essentially this is Magic wand for the earth, because they contain a large number of phosphorus, potassium, nitrogen, that is, precisely those substances that are vital for plants for their full growth.

Conclusion

Earthworms are an important link in soil formation. Let's look at the process. In autumn, leaves fall from the trees and cover the entire surface of the earth. Immediately after this, they get down to business and decompose the leaves to the compost stage. And then the baton is picked up by worms, which process the foliage to the vermicompost stage. This way, the most valuable fertilizers get into the soil.