Organisms living in the soil. Underground inhabitants. What insects can be found in the soil and should they be afraid Adaptations of organisms living in the soil

How animal habitat soil very different from water and air. The soil is a loose, thin surface layer of land in contact with air environment. Despite its insignificant thickness, this shell of the Earth plays essential role in the spread of life. The soil is not just a solid body, like most rocks of the lithosphere, but a complex three-phase system in which solid particles are surrounded by air and water. It is permeated with cavities filled with a mixture of gases and aqueous solutions, and therefore extremely diverse conditions are formed in it, favorable for the life of many micro- and macro-organisms. In the soil are smoothed temperature fluctuations compared to the surface layer of air, and the presence of groundwater and the penetration of precipitation create moisture reserves and provide a humidity regime intermediate between the aquatic and terrestrial environments. The soil concentrates reserves of organic and minerals supplied by dying vegetation and animal carcasses. All this determines greater saturation of the soil with life.

Every animal to live need to breathe. Conditions for respiration in soil are different than in water or air. Soil is composed of solid particles, water and air. Solid particles in the form of small lumps occupy a little more than half the volume of the soil; the rest of the volume falls on the share of gaps - pores that can be filled with air (in dry soil) or water (in soil saturated with moisture).

Moisture in the soil present in various states:

• bound (hygroscopic and film) is firmly held by the surface of soil particles;
• capillary occupies small pores and can move through them in different directions;
• gravity fills larger voids and slowly seeps down under the influence of gravity;
• vaporous is contained in the soil air.

Compound soil air changeable With depth, the oxygen content decreases sharply and the concentration of carbon dioxide increases. Due to the presence in the soil of decomposing organic matter soil air can contain a high concentration of toxic gases such as ammonia, hydrogen sulfide, methane, etc. When the soil is flooded or the plant residues rot intensively, completely anaerobic conditions can occur in places.

Temperature fluctuations cutting only on the surface of the soil. Here they can be even stronger than in the ground layer of air. However, with each centimeter deep, daily and seasonal temperature changes are becoming less and less visible at a depth of 1-1.5 m.

All these features lead to the fact that, despite the great heterogeneity of environmental conditions in the soil, it acts as fairly stable environment especially for mobile organisms. It is clear that animals can move relatively quickly in the soil only in natural voids, cracks, or previously dug passages. If there is nothing of this on the way, then the animal can advance only by breaking through the passage and raking the earth back or by swallowing the earth and passing it through the intestines.

Soil dwellers. Soil heterogeneity leads to the fact that for organisms different sizes it acts as a different environment. For microorganisms special meaning has a huge total surface of soil particles, since the vast majority of the microbial population is adsorbed on them. Due to this structure of the soil, numerous animals that breathe through their skin. Furthermore, hundreds of species of true freshwater animals inhabiting rivers, ponds and swamps. True, these are all microscopic creatures - lower worms and unicellular protozoa. They move, float in a film of water covering soil particles. If the soil dries up, these animals secrete a protective shell and, as it were, fall asleep, fall into a state of suspended animation.

Among soil animals there are also predators and those that feed on parts of living plants, mainly roots. There are in the soil, and consumers of decaying plant and animal residues; it is possible that bacteria also play a significant role in their nutrition. "Peaceful" moles eat great amount earthworms, snails and insect larvae, they even attack frogs, lizards and mice. There are predators among almost all groups of invertebrates living in the soil. Large ciliates feed not only on bacteria, but also on simple animals, such as flagellates. Predators include spiders and related haymakers

Soil animals find their food either in the soil itself or on its surface. The vital activity of many of them is very useful. Especially useful earthworms. They drag a huge amount of plant debris into their burrows, which contributes to the formation of humus and returns to the soil substances extracted from it by plant roots.

Not only earthworms “work” in the soil, but also their closest relatives:

• whitish annelids (enchytreids, or potworms),
• some types of microscopic roundworms (nematodes),
• small ticks,
• various insects,
• woodlice,
• millipedes,
• snails.

The purely mechanical work of many animals living in it also affects the soil. They make passages, mix and loosen the soil, dig holes. These are moles, marmots, ground squirrels, jerboas, field and forest mice, hamsters, voles, mole rats. The relatively large passages of some of these animals go 1-4 m deep. In some places, for example, in the steppe zone, a large number of dung beetles, bears, crickets, tarantulas, ants, and termites in the tropics dig passages and burrows in the soil.

In addition to the permanent inhabitants of the soil, among large animals can highlight a large environmental group inhabitants of holes (ground squirrels, marmots, jerboas, rabbits, badgers, etc.). They feed on the surface, but breed, hibernate, rest, and escape danger in the soil. A number of other animals use their burrows, finding in them a favorable microclimate and shelter from enemies. Norniks have structural features characteristic of terrestrial animals, but have a number of adaptations associated with a burrowing lifestyle. For example, badgers have long claws and strong muscles on the forelimbs, a narrow head, and small auricles. Compared to non-burrowing hares, rabbits have noticeably shortened ears and hind legs, a stronger skull, stronger bones and muscles of the forearms, etc.

The inhabitants of the soil in the process of evolution have developed adaptation to appropriate living conditions:

• features of the shape and structure of the body,
• physiological processes,
• reproduction and development
• ability to endure unfavourable conditions, behavior.

Earthworms, nematodes, most centipedes, the larvae of many beetles and flies have a highly elongated flexible body that makes it easy to move through winding narrow passages and cracks in the soil. Bristles in rain and others annelids, hairs and claws in arthropods allow them to significantly accelerate their movements in the soil and firmly hold in burrows, clinging to the walls of the passages. How slowly the worm crawls along the surface of the earth and with what speed, in essence, instantly, it hides in its hole. Laying new passages, some soil animals, such as worms, alternately stretch and shorten the body. At the same time, abdominal fluid is periodically pumped into the anterior end of the animal. It swells strongly and pushes the soil particles. Other animals, such as moles, clear their way by digging the ground with their front paws, which have turned into special bodies digging.

The color of animals constantly living in the soil is usually pale - grayish, yellowish, whitish. Their eyes, as a rule, are poorly developed or completely absent. But the organs of smell and touch have developed very subtly.

Many birds, mammals, reptiles, insects, etc. live on the surface of the earth. However, there are also animals that live underground. This article will talk about creatures that live almost their entire lives underground. Underground animals - who lives underground photo TOP-10 - look!

Underground animals - who lives underground photo TOP-10

Naked digger

Underground animals - who lives underground photo - naked digger

This little rodent belongs to the earthworm family. His distinctive features- cold-bloodedness, lack of sensitivity to pain and various acids. Of all the rodents, it is the naked mole rat that lives the longest - 28 years. Perhaps outwardly this baby can scare someone, but in fact this animal is not aggressive and kind.

giant mole rat

Underground animals - who lives underground photo - giant mole rat

Of all the representatives of the mole rats, the giant mole rat is the largest. In length, this giant reaches 35 centimeters, and weighs about one kilogram. The upper body is painted in a light gray or ocher-brown shade. This underground creature lives only underground, never getting out of its structures. Mole rats like to build multi-tiered entry and exit systems. Most often, they dig their feeding passages at a depth of 30-50 centimeters, usually in layers of sand. The entire length of these feed reaches 500 meters, but there are passages and less. Pantry and nesting chambers of mole rats are located at a depth of up to 3 meters. These creatures have huge teeth that can easily bite through the bayonet of a shovel, so it's best not to pick them up.

Underground animals - who lives underground photo - mole

Even small children know that the mole is an underground animal. Moles belong to mammals, to the order of insectivores. The place of residence of moles is Eurasia and North America. Moles come in both very small sizes and large ones. For example, some of them barely reach 5 centimeters, while others grow up to 20 centimeters. The weight of moles ranges from 9 grams to 170 grams. Moles are perfectly adapted to life underground. The body of these creatures is elongated, round, on which there is even and velvet fur. main feature the mole that helps him move in any direction underground is his fur coat, the villi of which grow upwards.

tuco tuco

Underground animals - who lives underground photo - tuko-tuko

Tiny rodents whose weight does not exceed 700 grams. In length, babies reach 20-25 centimeters, and the length of their tail can reach 8 centimeters. Morphological features of these animals fully indicate that they are adapted to life underground. Tuko-tuko leads an exclusively underground lifestyle, they build many intricate passages in which their pantries, latrines and nesting chambers are stored. Animals use sandy or loose soils to build their home.

Underground animals - who lives underground photo - gopher

The next creature reaches a length of 10-35 centimeters, and its tail is 5-15 centimeters. The weight of the gophers barely reaches one kilogram. Animals spend most of their lives in their intricate passages, which they lay on various soil horizons. The tunnels can be up to 100 meters long.

spotted snake

Underground animals - who lives underground photo - spotted snake

This species belongs to the genus Cylindrical. The snake is quite small in size, but very dense. The color of the snake is black with brown spots arranged in two rows. Lives only underground, and feeds on earthworms.

Underground animals - who lives underground photo - simple crucian

This fish almost always lives in a bottom mule, but when the pond dries up, it burrows underground. Carp can dig from 1 to 10 meters, and they can live underground for several years.

Medvedka

Underground animals - who lives underground photo - bear

This insect is one of the largest. In length, the bear can grow up to 5 centimeters. The belly of this creature is three times larger than the cephalothorax, soft to the touch, the diameter reaches 1 centimeter. At the end of the belly there are filiform paired appendages, the length of which is 1 centimeter. Like other creatures on this list, the mole cricket leads an underground lifestyle, however, there are times when an insect gets out to the surface, usually at night.

Chafer

Underground animals - who lives underground photo - cockchafer

Adult individuals of the eastern type reach 28 millimeters in length, and 32 millimeters in the western type. Their body is painted black, and their wings are dark brown. May beetles live underground, but in May they get to the surface and live there for about two months. Two weeks later, the mating process takes place, as a result of which the female lays eggs underground at a depth of 20 centimeters. The process of laying eggs can be carried out in several stages at once, as a result of which the female lays about 70 eggs. As soon as the clutch comes to an end, the female immediately dies.

Earthworm

Underground animals - who lives underground photo - earthworm

In length, the worms grow up to 2 meters, and their body consists of a huge number of annular segments. Moving, the worms rely on special bristles that are located on each ring, with the exception of the front one. Approximate number of setae on each segment ranges from 8 to several tens. Earthworms can be found everywhere except Antarctica, since they do not live there. Despite the fact that they lead an underground lifestyle, worms crawl out to the surface of the earth after rain, which is why they got their name.

Soil dwellers. We had to consider the land in the yard, in the garden, in the field, on the banks of the river. Have you seen small bugs swarming in the ground? The soil is literally saturated with life - rodents, insects, worms, centipedes and other living organisms live in it at different depths. If these inhabitants of the soil are destroyed, then the soil will not be fertile. If the soil becomes infertile, then in winter we will have nothing to eat.

Soil dwellers. Everyone is familiar with these animals - both adults and children. They live right under our feet, although we do not always notice them. Lazy earthworms, clumsy larvae, nimble centipedes are born from earthen lumps crumbling under a shovel. Often we squeamishly throw them aside or immediately destroy them as pests of garden plants. How many of these creatures inhabit the soil and who are they our friends or enemies? Let's try to figure it out...

About the most inconspicuous ... The roots of plants, myceliums of various fungi penetrate the soil. They absorb water and mineral salts dissolved in it. Especially a lot of microorganisms in the soil. So, in 1 sq. cm soil contains tens and even hundreds of millions of bacteria, protozoa, unicellular fungi and even algae! Microorganisms decompose the dead remains of plants and animals into simple minerals, which, dissolving in soil water, become available to plant roots.

Multicellular inhabitants of the soil Live in the soil and larger animals. These are, first of all, various ticks, slugs, and some insects. They do not have special devices for digging passages in the soil, so they live shallow. But earthworms, centipedes, insect larvae can make their own way. The earthworm pushes the soil particles apart with the head section of the body or “bites in”, passing it through itself.

And now - about the largest ... The largest of the permanent inhabitants of the soil are moles, shrews and mole rats. They spend their whole lives in the soil, in complete darkness, so they have undeveloped eyes. Everything they have is adapted for life underground: an elongated body, thick and short fur, strong digging front legs in a mole and powerful incisors in a mole rat. With their help, they create complex systems of moves, traps, pantries.

The soil is home to a huge number of living organisms! So, many organisms live in the soil. What difficulties do they face? First, the soil is quite dense, and its inhabitants must live in microscopically small cavities or be able to dig, make their way. Secondly, light does not penetrate here, and the life of many organisms passes in complete darkness. Thirdly, there is not enough oxygen in the soil. But it is fully provided with water, it contains a lot of mineral and organic substances, the stock of which is constantly replenished due to dying plants and animals. In the soil there are no such sharp temperature fluctuations as on the surface. All this creates favorable conditions for the life of numerous organisms. The soil is literally saturated with life, although it is not as noticeable as life on land or in a reservoir.

There is a world hidden from us, inaccessible to direct observation - a kind of world of soil animals. There is eternal darkness, you cannot penetrate there without violating the natural structure of the soil. And only a few, accidentally noticed signs show that under the surface of the soil among the roots of plants there is a rich and diverse world of animals. This is sometimes evidenced by mounds above mole burrows, holes in gopher burrows in the steppe or burrows of sand martins in a cliff above a river, heaps of earth on a path thrown out by earthworms, and they themselves, crawling out after rain, as well as masses suddenly appearing literally from under the ground. winged ants or fat larvae of May beetles that come across in the ground.

As a habitat for animals, soil is very different from water and air. Try to wave your hand in the air - you will not notice almost any resistance. Do the same in water - you will feel a significant resistance of the environment. And if you put your hand into the hole and cover it with earth, not only move it, but it will be difficult to pull it back out. It is clear that animals can move relatively quickly in the soil only in natural voids, cracks, or previously dug passages. If there is nothing of this on the way, then the animal can advance only by breaking through the passage and raking the earth back or by swallowing the earth and passing it through the intestines. The speed of movement in this case, of course, will be insignificant.

Every animal needs to breathe in order to live. Conditions for respiration in soil are different than in water or air. Soil is composed of solid particles, water and air. Solid particles in the form of small lumps occupy a little more than half the volume of the soil; the rest of the volume falls on the share of gaps - pores that can be filled with air (in dry soil) or water (in soil saturated with moisture). As a rule, water covers all soil particles with a thin film; the rest of the space between them is occupied by air saturated with water vapor.

Earthworm.

Due to this structure of the soil, numerous animals live in it, which breathe through the skin. If they are taken out of the ground, they quickly die from drying out. skin. Moreover, hundreds of species of real freshwater animals inhabiting rivers, ponds and swamps live in the soil. True, these are all microscopic creatures - lower worms and unicellular protozoa. They move, float in a film of water covering soil particles.

If the soil dries up, these animals secrete a protective shell and, as it were, fall asleep, fall into a state of suspended animation. Oxygen enters the soil air from the atmosphere: its amount in the soil is 1-2% less than in the atmospheric air. Oxygen is consumed in the soil by animals, microorganisms, and plant roots during respiration. They all emit carbon dioxide. In the soil air it is 10-15 times more than in the atmosphere. Free gas exchange of soil and atmospheric air occurs only if the pores between solid particles are not completely filled with water. After heavy rains or in the spring, after the snow melts, the soil is saturated with water. There is not enough air in the soil, and under the threat of death, many animals leave it. This explains the appearance of earthworms on the surface after heavy rains, which you probably often observed.

Among soil animals there are both predators and those that feed on parts of living plants, mainly roots. There are also consumers of decaying plant and animal residues in the soil; it is possible that bacteria also play a significant role in their nutrition.

Soil animals find their food either in the soil itself or on its surface. The vital activity of many of them is very useful. Earthworms are especially useful. They drag a huge amount of plant debris into their burrows, which contributes to the formation of humus and returns to the soil substances extracted from it by plant roots.

In forest soils, invertebrates, especially earthworms, recycle more than half of all leaf litter. For a year on each hectare they throw up to 25-30 tons of processed earth to the surface, thus creating a good, structural soil. If you distribute this land evenly over the entire surface of a hectare, you get a layer of 0.5-0.8 cm. Therefore, earthworms are rightly considered the most important soil formers.

Medvedka.

Not only earthworms “work” in the soil, but also their closest relatives - smaller whitish annelids (enchytreids, or potworms), as well as some types of microscopic roundworms (nematodes), small mites, various insects, especially their larvae, and finally woodlice, centipedes and even snails.

The purely mechanical work of many animals living in it also affects the soil. They make passages, mix and loosen the soil, dig holes. All this increases the number of voids in the soil and facilitates the penetration of air and water into its depth. Such "work" involves not only relatively small invertebrates, but also many mammals - moles, marmots, ground squirrels, jerboas, field and forest mice, hamsters, voles, mole rats. The relatively large passages of some of these animals go 1–4 m deep. The passages of large earthworms also go deep: in most of them they reach 1.5–2 m, and in one southern worm even 8 m. in denser soils, plant roots penetrate deeper. In some places, for example, in the steppe zone, a large number of passages and holes are dug in the soil by dung beetles, bears, crickets, tarantula spiders, ants, and in the tropics - termites.

Mole. Its front paws are well adapted for digging.

Many soil animals feed on roots, tubers, and bulbs of plants. Those who attack cultivated plants or on forest plantations are considered pests, such as the cockchafer. Its larva lives in the soil for about four years and pupates there. In the first year of life, she feeds mainly on roots. herbaceous plants. But, growing up, the larva begins to feed on the roots of trees, especially young pines, and brings to the forest or forest plantations great harm. Larvae of click beetles, dark beetles, weevils, pollen eaters, caterpillars of some butterflies, such as nibbling scoops, larvae of many flies, cicadas, and, finally, root aphids, such as phylloxera, also feed on the roots of various plants, severely damaging them.

Many insects that damage the aerial parts of plants - stems, leaves, flowers, fruits, lay eggs in the soil; here, the larvae hatched from the eggs hide during the drought, hibernate, and pupate. Soil pests include some types of mites and centipedes, naked slugs and extremely numerous microscopic roundworms - nematodes. Nematodes penetrate from the soil into the roots of plants and disrupt their normal life.

An ant lion larva at the bottom of a sandy crater constructed by her.

Many predators live in the soil. "Peaceful" moles eat a huge amount of earthworms, snails and insect larvae, they even attack frogs, lizards and mice. These animals eat almost continuously. For example, a mole per day eats almost as much living creatures by weight as it weighs itself.

There are predators among almost all groups of invertebrates living in the soil. Large ciliates feed not only on bacteria, but also on simple animals, such as flagellates. The ciliates themselves serve as food for some roundworms. Predatory mites attack other mites and tiny insects. Thin, long, pale-colored centipedes - geophiles, living in cracks in the soil, as well as larger dark-colored drupes and centipedes, holding under stones, in stumps, are also predators. They feed on insects and their larvae, worms and other small animals. Predators include spiders and haymakers close to them. Many of them live on the surface of the soil, in bedding or under objects lying on the ground.

Many live in the soil predatory insects. These are ground beetles and their larvae, which play a significant role in the extermination of pests, many ants, especially more large species, exterminating a large number of harmful caterpillars, and, finally, the famous ant lions, so named because their larvae prey on ants. The ant lion larva has strong sharp jaws, its length is about 1 cm. The larva digs a funnel-shaped hole in dry sandy soil, usually at the edge of a pine forest, and burrows into the sand at its bottom, exposing only wide-open jaws. Small insects, most often ants, falling on the edge of the funnel, roll down. Then the ant lion larva grabs the victim and sucks it out. Adult antlions outwardly resemble dragonflies, their body length reaches 5 cm, and the wingspan is 12 cm.

In some places, a predatory ... mushroom is found in the soil! The mycelium of this fungus, which bears the tricky name "didimozoophagus", forms special trapping rings. They get small soil worms - nematodes. With the help of special enzymes, the fungus dissolves the rather strong shell of the worm, grows inside its body and eats it clean.

The inhabitants of the soil in the process of evolution developed adaptations to the corresponding living conditions: features of the shape and structure of the body, physiological processes, reproduction and development, the ability to endure adverse conditions, behavior. Earthworms, nematodes, most centipedes, the larvae of many beetles and flies have a highly elongated flexible body that makes it easy to move through winding narrow passages and cracks in the soil. The bristles of earthworms and other annelids, the hairs and claws of arthropods allow them to significantly speed up their movements in the soil and hold firmly in burrows, clinging to the walls of the passages. See how slowly

the worm crawls on the surface of the earth and with what speed, in essence, instantly, it hides in its hole. Laying new passages, some soil animals, such as worms, alternately stretch and shorten the body. At the same time, abdominal fluid is periodically pumped into the anterior end of the animal. It swells strongly and pushes the soil particles. Other animals, such as moles, clear their way by digging the ground with their front paws, which have turned into special digging organs.

The color of animals constantly living in the soil is usually pale - grayish, yellowish, whitish. Their eyes, as a rule, are poorly developed or completely absent. But the organs of smell and touch have developed very subtly.

The soil animal world is very rich. It includes about three hundred species of protozoa, more than a thousand species of round and annelids, tens of thousands of arthropods, hundreds of mollusks and a number of vertebrate species. Among soil animals there are both useful and harmful. But most of them are still listed under the heading "indifferent". Perhaps this is the result of our ignorance. Studying them is the next task of science.

4.3.2. Soil dwellers

The heterogeneity of the soil leads to the fact that for organisms of different sizes it acts as a different environment. For microorganisms, the huge total surface of soil particles is of particular importance, since the vast majority of the microbial population is adsorbed on them. Complexity soil environment creates a wide variety of conditions for a variety of functional groups: aerobes and anaerobes, consumers of organic and mineral compounds. The distribution of microorganisms in the soil is characterized by small foci, since even over a few millimeters different ecological zones can be replaced.

For small soil animals (Fig. 52, 53), which are combined under the name microfauna (protozoa, rotifers, tardigrades, nematodes, etc.), the soil is a system of micro-reservoirs. Essentially, they are aquatic organisms. They live in soil pores filled with gravitational or capillary water, and part of life can, like microorganisms, be in an adsorbed state on the surface of particles in thin layers of film moisture. Many of these species live in ordinary water bodies. However, soil forms are much smaller than freshwater ones and, in addition, they are distinguished by their ability to stay in an encysted state for a long time, waiting out unfavorable periods. While freshwater amoebas are 50-100 microns in size, soil ones are only 10-15. Representatives of flagellates are especially small, often only 2-5 microns. Soil ciliates also have dwarf sizes and, moreover, can greatly change the shape of the body.

Rice. 52. Testate amoeba feeding on bacteria on decaying forest floor leaves

Rice. 53. Soil microfauna (according to W. Dunger, 1974):

1–4 - flagella; 5–8 - naked amoeba; 9-10 - testate amoeba; 11–13 - ciliates; 14–16 - roundworms; 17–18 - rotifers; 19–20 – tardigrades

For air-breathers of slightly larger animals, the soil appears as a system of shallow caves. Such animals are grouped under the name mesofauna (Fig. 54). The sizes of representatives of the soil mesofauna range from tenths to 2–3 mm. This group includes mainly arthropods: numerous groups of ticks, primary wingless insects (springtails, protura, two-tailed insects), small species of winged insects, centipedes symphyla, etc. They do not have special adaptations for digging. They crawl along the walls of soil cavities with the help of limbs or wriggling like a worm. Soil air saturated with water vapor allows you to breathe through the covers. Many species do not have a tracheal system. Such animals are very sensitive to desiccation. The main means of salvation from fluctuations in air humidity for them is movement inland. But the possibility of migration deep into the soil cavities is limited by the rapid decrease in the diameter of the pores, so only the smallest species can move through the soil wells. Larger representatives of the mesofauna have some adaptations that allow them to endure a temporary decrease in soil air humidity: protective scales on the body, partial impermeability of the integument, a solid thick-walled shell with an epicuticle in combination with a primitive tracheal system that provides breathing.

Rice. 54. Soil mesofauna (no W. Danger, 1974):

1 - false scorion; 2 - Gama new flare; 3–4 shell mites; 5 – centipede pauroioda; 6 – chironomid mosquito larva; 7 - a beetle from the family. Ptiliidae; 8–9 springtails

Representatives of the mesofauna experience periods of flooding of the soil with water in air bubbles. The air is retained around the body of animals due to their non-wetting integuments, which are also equipped with hairs, scales, etc. The air bubble serves as a kind of "physical gill" for a small animal. Breathing is carried out due to oxygen diffusing into the air layer from the surrounding water.

Representatives of micro- and mesofauna are able to tolerate winter freezing of the soil, since most species cannot go down from layers exposed to negative temperatures.

Larger soil animals, with body sizes from 2 to 20 mm, are called representatives macro fauna (Fig. 55). These are insect larvae, centipedes, enchytreids, earthworms, etc. For them, the soil is a dense medium that provides significant mechanical resistance when moving. These relatively large forms move in the soil either by expanding natural wells by pushing apart soil particles, or by digging new passages. Both modes of movement leave an imprint on external structure animals.

Rice. 55. Soil macrofauna (no W. Danger, 1974):

1 - earthworm; 2 – woodlice; 3 – labiopod centipede; 4 – bipedal centipede; 5 - beetle larva; 6 – click beetle larva; 7 – bear; 8 - grub larva

The ability to move along thin holes, almost without resorting to digging, is inherent only in species that have a body with a small cross section that can strongly bend in winding passages (millipedes - drupes and geophiles). Pushing the soil particles apart due to the pressure of the body walls, earthworms, larvae of centipede mosquitoes, etc. move. Having fixed the posterior end, they thin and lengthen the anterior one, penetrating into narrow soil cracks, then fix the anterior part of the body and increase its diameter. At the same time, strong hydraulic pressure of the incompressible intracavitary fluid is created in the expanded area due to the work of the muscles: in worms, the contents of coelomic sacs, and in tipulids, hemolymph. The pressure is transmitted through the walls of the body to the soil, and thus the animal expands the well. At the same time, an open passage remains behind, which threatens to increase evaporation and the pursuit of predators. Many species have developed adaptations to an ecologically more beneficial type of movement in the soil - digging with clogging the passage behind. Digging is carried out by loosening and raking soil particles. For this, the larvae of various insects use the anterior end of the head, mandibles and forelimbs, expanded and reinforced with a thick layer of chitin, spines and outgrowths. At the posterior end of the body, devices for strong fixation develop - retractable supports, teeth, hooks. To close the passage on the last segments, a number of species have a special depressed platform, framed by chitinous sides or teeth, a kind of wheelbarrow. Similar areas are formed on the back of the elytra in bark beetles, which also use them to clog passages with drill flour. Closing the passage behind them, the animals - the inhabitants of the soil are constantly in a closed chamber, saturated with the evaporation of their own body.

Gas exchange of most species of this ecological group is carried out using specialized bodies respiration, but along with this is supplemented by gas exchange through the integument. It is even possible exclusively skin respiration, for example, in earthworms, enchitreid.

Burrowing animals can leave layers where unfavorable conditions arise. In drought and winter, they concentrate in deeper layers, usually a few tens of centimeters from the surface.

Megafauna soils are large excavations, mainly from among mammals. A number of species spend their whole lives in the soil (mole rats, mole voles, zokors, moles of Eurasia, golden moles

Africa, marsupial moles of Australia, etc.). They make whole systems of passages and holes in the soil. Appearance And anatomical features of these animals reflect their adaptability to a burrowing underground lifestyle. They have underdeveloped eyes, a compact, valky body with a short neck, short thick fur, strong digging limbs with strong claws. Mole rats and mole voles loosen the ground with their chisels. Large oligochaetes, especially representatives of the Megascolecidae family living in the tropics and the Southern Hemisphere, should also be included in the soil megafauna. The largest of them, the Australian Megascolides australis, reaches a length of 2.5 and even 3 m.

In addition to the permanent inhabitants of the soil, a large ecological group can be distinguished among large animals. burrow dwellers (ground squirrels, marmots, jerboas, rabbits, badgers, etc.). They feed on the surface, but breed, hibernate, rest, and escape danger in the soil. A number of other animals use their burrows, finding in them a favorable microclimate and shelter from enemies. Norniks have structural features characteristic of terrestrial animals, but have a number of adaptations associated with a burrowing lifestyle. For example, badgers have long claws and strong muscles on the forelimbs, a narrow head, and small auricles. Compared to non-burrowing hares, rabbits have noticeably shortened ears and hind legs, a stronger skull, stronger bones and muscles of the forearms, etc.

For a range of environmental features soil is an intermediate medium between water and land. WITH aquatic environment the soil is brought closer by its temperature regime, the reduced oxygen content in the soil air, its saturation with water vapor and the presence of water in other forms, the presence of salts and organic substances in soil solutions, and the ability to move in three dimensions.

The soil is brought closer to the air environment by the presence of soil air, the threat of drying out in the upper horizons, quite drastic changes temperature regime surface layers.

The intermediate ecological properties of the soil as a habitat for animals suggest that the soil played a special role in the evolution of the animal world. For many groups, in particular arthropods, the soil served as a medium through which initially aquatic life were able to switch to a terrestrial way of life and conquer the land. This path of evolution of arthropods was proved by the works of M. S. Gilyarov (1912–1985).