The circulatory system of the earthworm: description, structure and features. Common earthworm Excretory system of an earthworm drawing

Well known to all earthworms constitute large group species belonging to different families of oligochaetes.

Our common earthworm, reaching 30 centimeters in length and a centimeter in thickness, belongs to the most fully studied family of Lumbricidae, which includes about 200 species, about a hundred of which are found in Russia.

Types of earthworms

According to the characteristics of the biology of earthworms, earthworms can be divided into two types: the first includes worms that feed on the surface of the soil, the second - those that feed in the soil. In the first type, litter worms can also be distinguished, which live in the litter layer and under no circumstances (even when the soil dries out or freezes) do not sink into the ground deeper than 5-10 centimeters. This type also includes soil-litter worms that penetrate the soil deeper than 10-20 centimeters, but only under unfavorable conditions, and burrowing worms that make constant deep passages (up to 1 meter or more), which they usually do not leave, but when feeding and mating, only the front end of the body protrudes to the surface of the soil. The second type can be divided into burrowing worms, living in the deep soil horizon, and burrowing worms, which have constant moves, but feed in the humus horizon.

Litter and burrowing worms inhabit places with waterlogged soils - the banks of water bodies, swampy soils, soils of humid subtropics. In the tundra and taiga, only litter and soil-litter forms live, and in the steppes, only soil forms proper. They feel best in conditions of coniferous-deciduous forests: all types of Lumbricidae live in these zones.

Lifestyle of worms

According to the way of life, worms are nocturnal animals, and at night you can observe how they swarm everywhere in large numbers, while remaining with their tails in minks. Stretching out, they rummage around the surrounding space, grab with their mouths (at the same time, the pharynx of the worm turns slightly outward and then retracts back) damp fallen leaves and drag them into minks.

Earthworms are omnivores. They swallow great amount land from which they assimilate organic matter they eat the same way a large number of all kinds of half-decayed leaves, except for very hard or having an unpleasant smell for them. When keeping worms in pots of earth, you can watch them eat fresh leaves some plants.

Very interesting observations of earthworms were made by C. Darwin, who dedicated these animals great study. In 1881, his book "The Formation of the Vegetative Layer by the Activity of Earthworms" was published. Charles Darwin kept earthworms in pots of earth and spent interesting experiences to study the nutrition and behavior of these animals. So, in order to find out what kind of food, besides leaves and earth, worms can eat, he pinned pieces of boiled and raw meat on the surface of the earth in a pot and watched the worms picking at the meat every night, and most of pieces were eaten. They also ate pieces of dead worms, for which Darwin even called them cannibals.

Half-rotted or fresh leaves are dragged by worms through the holes of minks to a depth of 6-10 centimeters and eaten there. Darwin observed how worms capture food items. If fresh leaves are pinned to the surface of the earth in a flower pot, then the worms will try to drag them into their burrows. Usually they tear off small pieces, grabbing the edge of the leaf between the prominent upper and lower lip. At this time, a thick, powerful pharynx protrudes forward and thereby creates a fulcrum for the upper lip. If the worm comes across a flat, large surface of a leaf, it acts differently. The anterior rings of the body are slightly drawn into the subsequent rings, due to which the anterior end of the body expands, becomes blunt with a small hole at the end. The pharynx moves forward, is pressed against the surface of the sheet, and then, without detaching, is pulled back and slightly expanded. As a result, a "vacuum" is formed in the hole at the front end of the body, applied to the leaf. The pharynx acts like a piston, and the worm sticks very firmly to the surface of the leaf. If you put a thin fading cabbage leaf on the worm, then with reverse side from the worm you can see a depression just above the head end of the animal. The worm never touches the veins of the leaf, but sucks out the delicate tissues of the leaves.

Worms use the leaves not only for food, but also plug the entrances to the minks with them. To this end, they also drag pieces of stems, withered flowers, scraps of paper, feathers, and tufts of wool into holes. Sometimes bundles of leaf petioles or feathers protrude from the worm's hole.

Leaves dragged into the burrows of worms are always crumpled or folded into a large number of folds. When the next leaf is pulled in, it is placed on the outside of the previous one, all the leaves are tightly folded and pressed against each other. Sometimes the worm enlarges the hole of its mink or makes another next to it in order to collect even more leaves. The worms fill the gaps between the leaves with moist earth thrown out of their intestines in such a way that the minks are completely clogged. Such clogged minks are especially common in the autumn before the wintering of the worms. The upper part of the passage is lined with leaves, which, according to Darwin, prevents the worm's body from contacting the cold and wet ground near the soil surface.

Darwin also described how earthworms dig holes. They do this either by pushing the earth in all directions, or by swallowing it. In the first case, the worm pushes the narrow front end of the body into the gaps between the particles of the earth, then inflates and contracts it, and thereby the soil particles move apart. The front end of the body works like a wedge. If the earth or sand is very dense, compacted, the worm cannot push the soil particles apart and acts in a different way. It swallows the earth, and, passing it through itself, gradually sinks into the ground, leaving behind a growing pile of excrement. The ability to absorb sand, chalk or other substrates completely devoid of organic matter is a necessary adaptation in the event that the worm, plunging into the soil from excessive dryness or cold, finds itself in front of unbroken dense layers of soil.

Minks of worms go either vertically or a little sideways. Almost always they are lined from the inside with a thin layer of black earth processed by animals. Lumps of earth ejected from the intestines are compacted along the walls of the mink by the vertical movements of the worm. The lining thus formed becomes very hard and smooth and closely adheres to the body of the worm, and the setae curved back have excellent points of support, which allows the worm to move forward and backward very quickly in the hole. The lining, on the one hand, strengthens the walls of the mink, on the other hand, protects the body of the worm from scratches. Minks leading down usually end with an extension, or a chamber. Here the worms spend the winter, singly or weaving into a ball of several individuals. The mink is usually lined with small stones or seeds, which creates a layer of air for the worms to breathe.

After the worm swallows a portion of the earth, whether it is done for food or for digging a passage, it rises to the surface to throw the earth out of itself. The discarded earth is saturated with intestinal secretions and, as a result, becomes viscous. After drying, lumps of excrement harden. The earth is thrown out by the worm not randomly, but alternately in different directions from the entrance to the hole. The tail works like a shovel. As a result, a kind of tower of excrement lumps is formed around the entrance to the burrow. Such turrets in worms different types have different shape and height.

Earthworm exit

When the worm protrudes from the mink to throw out excrement, it stretches its tail forward, but if it is to collect leaves, it puts out its head. Therefore, worms have the ability to roll over in their burrows. Worms do not always throw excrement on the surface of the soil. If they find some kind of cavity, for example, near the roots of trees, in newly dug up earth, they deposit their excrement there. It is easy to see that the space under stones or fallen tree trunks is always filled with small pellets of earthworm excrement. Sometimes animals fill the cavities of their old minks with them.

Life of earthworms

Earthworms in the history of the formation of the earth's crust played a much more important role than it might seem at first glance. They are numerous in almost all humid areas. Due to the digging activity of the worms, the surface layer of the soil is in constant motion. As a result of this “digging”, soil particles are rubbed against each other, new layers of soil brought to the surface are exposed to carbon dioxide and humic acids, which contributes to the dissolution of many minerals. The formation of humic acids is due to the digestion of semi-decomposed leaves by earthworms. It has been established that worms contribute to an increase in the content of phosphorus and potassium in the soil. In addition, passing through intestinal tract worms, earth and plant residues are glued together with calcite, a derivative of calcium carbonate secreted by the calcareous glands of the digestive system of worms. The excrement compressed by contractions of the intestinal muscles is thrown out in the form of very strong particles, which are washed out much more slowly than simple lumps of earth of the same size and are elements of the granular structure of the soil. The amount and mass of excrement produced annually by earthworms is enormous. During the day, each worm passes through its intestines the amount of earth, approximately equal to weight his body, i.e. 4-5 grams. Every year, earthworms throw a layer of excrement 0.5 centimeters thick onto the surface of the earth. C. Darwin counted them up to 4 tons of dry matter per hectare of pastures in England. Near Moscow, in a field of perennial grasses, earthworms annually form 53 tons of excrement per hectare of land.

Worms nai in the best way they prepare the soil for the growth of plants: they loosen it so that there is no lump larger than they can swallow, they facilitate the penetration of water and air into the soil. Dragging the leaves into their burrows, they crush them, partially digest them and mix them with earthen excrement. Evenly mixing the soil and plant residues, they prepare a fertile mixture, like a gardener. The roots of plants move freely in the soil along the paths of earthworms, finding rich nutritious humus in them. It is impossible not to be surprised when you think that the entire fertile layer has already passed through the bodies of earthworms and will pass through them again in a few years. It is doubtful, Darwin believes, that there are still other animals that would occupy such a prominent place in the history of the earth's crust as these essentially lowly organized creatures.

Thanks to the activity of worms, large objects, stones gradually sink deep into the earth, and small fragments of stones are gradually ground in their intestines to sand. Darwin, describing how abandoned castles in old England were gradually sinking underground, emphasized that archaeologists should be indebted to earthworms for the preservation of a large number of ancient objects. After all, coins, gold jewelry, stone tools, etc., falling on the surface of the earth, are buried under the excrement of worms for several years and are thus reliably preserved until the earth covering them is removed in the future.

Earthworms, like many other animals, are affected economic activity person. Their numbers are declining due to the excessive use of fertilizers and pesticides, cutting down of trees and shrubs, under the influence of overgrazing of livestock. 11 species of earthworms are included in the Red Book of the Russian Federation. Successful attempts have been repeatedly made to relocate and acclimatize worms of different species to those areas where they are not enough. Such activities are called zoological reclamation.

earthworms, they are earthworms, this is far from one species, but a whole suborder of the class Small-bristle worms, belonging to the type Annelids. For earthworm most of the structural features of its type and class are characteristic.

Earthworms are ubiquitous. More than a dozen live in our area. similar friend on another species (European earthworms), whose body length 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 on to the edge of the mink with its hind end.

The body of an earthworm, as a representative of annelids, is divided into segments by annular constrictions. As in all oligochaetes, the parapodia are reduced, only tufts of setae have been 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, 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, it also contains many mucous cells. Under the epithelium are circular and longitudinal muscles. The body of an earthworm can contract and lengthen. The circular muscles make the body of the worm thin and long, the longitudinal muscles shorten and thicken. The longitudinal layer of muscles is more powerful. Alternate contraction of these muscles provides locomotion. Each segment can change its shape separately.

The coelomic sacs of neighboring segments communicate with each other, thus, the liquid in them is mixed.

An earthworm often swallows the soil, eating its own way. Nutrient particles are absorbed from the soil in the intestines. If the soil is soft, then it drills with its front end. First, the front end is stretched and thinned, pushed between the lumps of soil. After the front end thickens, as a result, the soil moves apart. Next, the worm pulls up the back of the body.

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

Digestive system consists of their mouth, pharynx, esophagus, goiter, muscular stomach, middle and hindgut, anus. Swallowing food is produced by the muscular pharynx. The stomach grinds food, in addition to the muscles of the walls, swallowed grains of sand participate in this. From the side of the back, the wall of the middle intestine forms an invagination that increases the suction surface. The midgut is lined with ciliated epithelium, in which there are many unicellular glands. It breaks down complex organic substances, absorbs more simple substances. In the walls of the midgut of the earthworm there is a dense network of blood vessels. The hindgut is small, ending in the anus.

A feature of earthworms are calcareous glands, whose ducts empty into the esophagus. Substances released by them neutralize the acids contained in the soil.

Breathing is carried out by 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 come to the surface due to lack of air in the soil.

The circulatory, nervous, and excretory systems are similar to polychaete. However, in the circulatory system there are so-called "hearts" - annular vessels capable of muscular contraction. Located in 7-13 segments. A number of species have annular vessels only in the anterior part of the body.

In the anterior three segments, there are no metanephridia (organs of excretion of annelids).

The sense organs are poorly developed. In the skin there are sensitive cells - organs of touch. Also in the skin there are cells 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 testicles are in front of the ovaries.

Fertilization is mutual cross. Each of the mating worms transfers spermatozoa 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 clutch. Unfertilized eggs are laid in it. After mating, spermatozoa enter here from the spermatozoa. Fertilization takes place. After that, the clutch slips off the body of the worm and turns into a cocoon. The eggs develop into small worms.

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

Everyone knows earthworms, they make up a large group of different species belonging to the oligochaete family.

The common earthworm belongs to the most famous family of Lumbricidae, consisting of about 200 species, and about 100 of them are found in our country. The body length of an ordinary earthworm reaches 30 centimeters.

Types of earthworms

Depending on the biology of earthworms, they are divided into 2 types: worms that feed in the soil and worms that feed on the soil surface.

Soil-feeding worms include litter worms that live in the litter layer and do not descend to a depth of less than 10 centimeters even when the soil freezes or dries up.

This type also includes soil-litter worms, which, under adverse conditions, can penetrate to a depth of up to 20 centimeters. This also includes burrowing worms that constantly live at a depth of 1 meter or more. These worms rarely leave their burrows, and when mating and feeding, they stick out only the front part of the body to the surface. In addition, burrowing worms belong to this type; they spend their lives in deep layers of the soil.

Burrowing and litter worms live in areas with waterlogged soils: on the banks of water bodies, in swampy areas, in humid subtropical zones. Litter and soil-litter worms live in the taiga and tundra. And soil worms live in the steppes. The most favorite habitat for all types of earthworms is coniferous-deciduous forests.

Lifestyle of worms

Earthworms are nocturnal. At night, they can be found swarming in large numbers in various places.

At the same time, they leave their tails in the minks, and the body is pulled out and explored the surrounding space, grabbing the fallen leaves with their mouths and dragging them into the minks. During feeding, the pharynx of the earthworm turns outward a little, and then retracts back.

Earthworm nutrition

Worms are omnivores. They swallow a large amount of soil and absorb organic matter from it. In the same way, they eat half-rotted leaves, except for hard leaves or leaves that are suitable for worms. bad smell. If the worms live in pots of earth, then you can see how they eat fresh plant leaves.

Darwin researched worms, he spent a lot scientific work and made interesting observations in the course of it. In 1881, Darwin's book, The Formation of the Vegetation Layer by the Activity of Earthworms, was published. The scientist kept worms in pots of earth and studied how they behave everyday life and eat. For example, in order to find out what else worms eat besides earth and leaves, he attached pieces of boiled and raw meat with pins and watched how every night the worms plucked at the meat, while eating some of the pieces. In addition, pieces of dead worms were used, so Darwin concluded that they were cannibals.

The worms drag half-decayed leaves into burrows to a depth of about 6-10 centimeters and eat them there. The scientist observed how earthworms grab food. If a leaf is pinned to the soil with a pin, then the worm will try to drag it underground. Most often, they grab small pieces of the sheet and tear them off. At this point, the thick pharynx protrudes outward and creates a fulcrum for the upper lip.

If the worm comes across a large flat surface of a leaf, then its strategy is different. It slightly presses the anterior rings into the subsequent ones, as a result of which the anterior end becomes wider, it acquires a blunt shape, and a small hole appears on it. The pharynx comes forward, attaches to the surface of the leaf, and then pulls back and expands slightly. As a result of such actions, a vacuum is obtained in the hole in the front of the body, which is attached to the sheet. That is, the pharynx acts as a piston, and the worm is tightly attached to the surface of the sheet. If the worm is given a thin cabbage leaf, then on its reverse side it will be possible to notice a recess located above the worm's head.

Earthworms do not eat leaf veins, they only suck out delicate tissues. They use the leaves not only for food, but also close the entrances to their holes with their help. Fading flowers, pieces of stems, wool, feathers, paper are also suitable for this. Often tufts of leaf petioles and feathers can be seen from earthworm burrows. To drag a leaf into a mink, the worm crushes it. The worm tightly folds the leaves to each other and squeezes. Sometimes the worms widen the holes of the burrows or make an extra move to gain new leaves. The space between the leaves is filled with moist earth from the intestines of the worm. So the minks are completely clogged. Such closed minks are most often caught in the autumn, before the worm leaves for the winter.

Earthworms lay leaves on the upper part of the mink, Darwin believed that they do so that their bodies do not touch the cold ground. In addition, Darwin learned about various ways digging minks. Worms do this either by swallowing the earth or pushing it apart in various directions. If the worm pushes the soil apart, then it pushes the narrow end of the body between the soil particles, then inflates it, and then contracts it, due to which the earth particles move apart. That is, he uses the front of his body as a wedge.

If the soil is too dense, then it is difficult for the earthworm to push the particles apart, so it changes its tactics of behavior. He swallows the earth, then passes it through himself, thus plunging gradually into the ground, and a pile of excrement grows behind him. Earthworms can absorb chalk, sand and other non-organic substrates. This feature helps the worms to sink into the ground when it is too dry or when it freezes.

Earthworm burrows are located vertically or slightly deeper. From the inside, they are almost always covered with a thin layer of black processed soil. The worm throws out the earth from the intestine and rams it along the walls of the hole, making vertical movements. As a result, the lining is smooth and very durable. The bristles located on the body of the worm are adjacent to the lining, they create a fulcrum, as a result of which the worm moves quickly in its hole. The lining not only makes the walls of the hole more durable, but also protects the body of the worm from getting scratched.

Minks that lead down tend to end in an extended chamber. Earthworms hibernate in these chambers. Some individuals spend the winter alone, while others are intertwined with each other in a ball. Mink worms are lined with seeds or small stones, resulting in a layer of air and the worm can breathe.

After the earthworm swallows the earth, feeding on it or swarming, it rises to the surface and throws it out. These lumps of earth are saturated with secretions from the intestines, so they are viscous. When the lumps dry, they harden. Worms throw out the earth not randomly, but in turn in different directions from the entrance to the mink. The worm's tail is used during this work as a shovel. Thus, a tower of excrement is formed around the entrance to the burrow. All turrets of worms of different species differ in height and shape.

Earthworm exit

To lean out of the hole and throw out excrement, the worm stretches its tail forward, and if the worm needs to collect leaves, then it sticks its head out of the ground. That is, in burrows, earthworms can roll over.

Earthworms do not always throw out the earth near the surface, if they find a cavity, for example, in plowed earth or near the roots of trees, then they throw excrement into this cavity. Between many stones and under fallen tree trunks there are small lumps of earthworm excrement. Sometimes worms fill their old burrows with excrement.

Life of earthworms

These small animals have played a significant role in the history of the formation of the earth's crust. They live in large numbers in damp places. Since worms dig the earth, it is constantly in motion. As a result of digging activity, soil particles rub against each other, new layers of soil fall to the surface, are exposed to humic acids and carbon dioxide, and most minerals dissolve. Musk acids are formed when worms digest half-decomposed leaves. Earthworms help increase the amount of potassium and phosphorus in the soil. In addition, the earth that has passed through the intestines of the worm is glued together with calcite, which is a derivative of calcium carbonate.

The excrement of the worms is tightly compressed and comes out in the form of solid particles that do not erode as quickly as ordinary lumps of soil of a similar size. These excrements are elements of the granular structure of the soil. Earthworms annually produce a huge amount of excrement. For a day, each earthworm leaves about 4-5 grams of earth, that is, this amount is equal to the body weight of the worm itself. Every year, earthworms throw a layer of excrement to the surface of the soil, the thickness of which is 0.5 centimeters. Darwin calculated that for 1 hectare of pastures in England there are up to 4 tons of dry matter. Near Moscow, in the fields of perennial grasses, worms form 53 tons of excrement per 1 hectare of land every year.

Worms prepare the soil for plant growth: the soil is loosened, small lumps are obtained, which improves the access of air and water penetration. In addition, earthworms drag leaves into their burrows, partially digesting them and mixing them with excrement. Thanks to the activity of the worms, the soil is evenly mixed with plant residues, thus, a fertile mixture is obtained.

It is easier for plant roots to spread in the passages of worms, moreover, they contain nutritious humus. It is difficult not to be surprised by the fact that the entire fertile layer has been processed by earthworms, and in a few years, they will process it again. Darwin believed that there were no more animals that had the same significance in the history of the formation of the earth's crust, although worms are lowly organized creatures.

The activity of earthworms leads to the fact that stones and large objects eventually go deep into the earth, and small fragments of the earth are gradually digested and turn into sand. Darwin stressed that archaeologists should be indebted to worms for their contribution to the preservation of ancient objects. Items such as gold jewelry, tools, coins and other archaeological treasures are gradually buried under the excrement of earthworms, thanks to which they are securely preserved for future generations, which will remove the layer of earth covering them.

Damage to earthworms, like many other animals, is caused by developing human economic activity. The use of pesticides and fertilizers leads to a decrease in the number of worms. To date, there are 11 species of earthworms in the Red Book. Many times people have been relocated different kinds earthworms in areas where they are scarce. Worms were acclimatized, and these attempts were successful. These activities, called zoological reclamation, allow you to save the number of earthworms.

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Many people underestimate the importance of the work of earthworms. These representatives of the invertebrate kingdom are known primarily for the fact that they crawl out of the ground in large numbers after heavy rain. They are often used as bait by numerous fishing enthusiasts. Darwin also noted the fact that worms perform an important function in nature, acting as a kind of agricultural technicians. In the process of creating an extensive system of tunnels that the earthworm breaks through, excellent aeration is formed through the flow of air to the inner layers of the soil.

Thanks to excellent aeration, the respiratory activity of many plants is facilitated. Feeding on organic matter and waste, worms ensure the grinding of soil components, while enriching them with their secretions. Amazing Ability representatives of this species is the ability to disinfect huge areas of soil, sterilizing it from harmful bacteria. Thanks to countless burrows that form a semblance of a capillary system, perfect drainage and ventilation of the soil is ensured.

The body of an earthworm can reach three meters in length. However, on the territory of Russia, there are mainly individuals whose body length does not exceed 30 centimeters. In order to move, the worm uses small bristles that are located on different parts torso. Depending on the variety, there can be from 100 to 300 segments. The circulatory system is closed and very well developed. It consists of one artery and one central vein.

The structure of the earthworm is very unusual. Breathing is realized with the help of special supersensitive cells. The skin produces a protective mucus with a sufficient amount of natural antiseptics. The structure of the brain is quite primitive and includes only two nerve nodes. According to the results of laboratory experiments, earthworms have confirmed their outstanding ability to regenerate. A severed tail grows back after a short period of time.

The genital organs of the earthworm are also arranged in a very unusual way. Each individual is a hermaphrodite. She also has male organs. According to biological factors, all such worms can be divided into several subgroups. Representatives of one of them are looking for food on the surface of the soil layer. Others use the soil itself as food and are extremely rarely shown from the ground.

Earthworm belongs to the ring type. Under the skin layer is a developed system of muscles, consisting of muscles various shapes. The mouth opening, from which food enters the esophagus through the pharynx, is located on the front of the body. From there it is transported to the area of ​​the enlarged goiter and not large sizes muscular stomach.

Burrowing and litter earthworms live in places with loose and moist soil. Preference is given to wet soils of the subtropics, swampy lands and the banks of various reservoirs. In the steppe territories, soil varieties of worms are usually found. Litter species live in the taiga and forest-tundra. The coniferous broad-leaved strip can boast of the highest concentration of individuals.

What kind of soil do worms like?

Why do earthworms love sandy and loamy soils? Such soil is characterized by low acidity, which is best suited for their life. The level of acidity above pH 5.5 is detrimental to the organisms of these representatives of the annular type. Wet soils is one of the prerequisites for population expansion. During dry and hot weather, worms go deep underground and lose the ability to reproduce.

The nature and lifestyle of the earthworm

The active and productive life of the earthworm falls on the dark time of the day. As soon as night falls, many individuals crawl out to the surface of the ground in search of food. However, the tail usually remains in the ground. By morning, they return to their burrows with prey, dragging pieces of food into them and masking the entrance to their shelter with blades of grass and foliage.

The role of earthworms in nature is difficult to overestimate. The worm literally passes through itself an incredible amount of soil mixture, enriching it with beneficial enzymes and killing harmful substances and bacteria. The worm moves by crawling. Pulling in one end of the body and clinging with bristles to the roughness of the earth, it pulls up the rear part, making its many passages in this way.

How do earthworms survive winter?

On the winter period the vast majority of individuals hibernate. A sharp drop in temperature can instantly destroy the worms, so they try to burrow into the soil in advance to a depth often exceeding one meter. Earthworms in the soil perform the most important function of its natural renewal and enrichment. various substances and micronutrients.

Benefit

In the process of digestion of semi-fermented leaves, the body of the worms produces specific enzymes that contribute to the active generation of humic acid. The soil that has been loosened by earthworms is optimal for a wide variety of representatives of the plant kingdom. Thanks to the system of intricate tunnels, excellent aeration and ventilation of the roots is provided. Thus, the movement of the earthworm is an important factor in the task of recovery useful qualities soil.

The earthworm is in fact very useful for humans. It makes the soil layers fertile and enriches them with all sorts of nutrients. However total individuals in many regions of Russia is rapidly declining. This happens due to the uncontrolled introduction of pesticides, fertilizers and mineral mixtures into the soil. Numerous birds, moles, and various rodents also prey on earthworms.

What do earthworms eat?

At night, the earthworm crawls to the surface and pulls the half-decayed remains of plants and leaves into its shelter. Also, his diet includes soil rich in humus. One representative of the species can process up to half a gram of soil per day. Considering that up to several million individuals can be located simultaneously on an area of ​​one hectare, they are able to act as indispensable soil converters.

After the rain, a large number of worms can be seen on the asphalt and soil surface, what makes them crawl out? Even the name "earthworms" indicates that they are very fond of moisture and become more active after rain. Consider a few possible causes why do earthworms crawl out after rain to the surface of the earth.

soil temperature

It is believed that the worms crawl to the surface in search of warmth, since after rain the soil temperature drops by several degrees, which causes discomfort for them.

Change in acid-base balance

Another theory says that the worms come to the surface due to a change in the acid-base balance of the soil after rain, it becomes more acidic, which negatively affects these diggers. According to researchers, emergency evacuation to the soil surface saves them from death in acidic environment.

Lack of air

The third theory explains that after rain, there is more oxygen in the upper layer of the soil, so the worms crawl out en masse. Water enriches the upper layers of the earth with oxygen, and many types of worms love moisture and vitally need enough oxygen. And through the surface of the body, oxygen is absorbed best in a humid environment.

Travels

British scientist Chris Low suggested that worms come to the surface of the earth during rain in order to make an extended journey to new territory. On the surface, worms can crawl much further than underground, and dry soil causes discomfort when moving, strong friction is created, grains of sand stick to the surface of the worm's body, injuring it. And after the rain, the surface of the earth is highly moistened, which allows them to freely travel to new areas of soil.

Sounds of the rain

Another scientist, Professor Joseph Gorris from the USA, suggested that earthworms are frightened by the sound of rain, since the vibrations that it creates are similar to the sound of the approach of their main enemy, the mole. That is why some fishermen use a technique to lure the bait to the surface: they insert a stick into the ground, fix a sheet of iron on its surface and pull it so as to create vibration, while the short is transmitted to the ground through the stick. Frightened, the worms get to the surface of the earth and become easy prey for experienced fishermen.

Reproduction and lifespan of earthworms

The earthworm is a hermaphrodite. It has both female and male reproductive organs. However, he is not capable of self-fertilization. With the onset of warm temperatures required for reproduction climatic conditions individuals crawl in pairs, attaching to each other with the abdominal region, and produce a kind of seed exchange. After that, the clutch is transformed into a cocoon, in which the eggs develop.

Some species differ in asexual reproduction. The body of the worm is divided in two, with one of the parts regenerating the anterior end, and the other regenerating the posterior end. There are also species of worms that reproduce without seed receptacles by laying spermatophores. The lifespan of worms can exceed ten years.

Animals, suborder earthworms. The body of an 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 the 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 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. The earthworm usually lives in humus-rich soil and is not common in 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 a prolonged drought, as well as during a 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 nervous system branching 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.

Food

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 circulatory system which 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 an earthworm is red, it has a very importance. With the help of blood, the connection between the organs of the animal is established, metabolism occurs. Moving through the body, it spreads from the digestive organs nutrients, as well as oxygen entering through the skin. At the same time, blood is carried from the tissues to the skin carbon dioxide. 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 located all over the surface of his body. The sensitivity of the earthworm to various kinds of external irritation is quite high. 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, having no special organs of vision, still 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.