Organisms living in the soil: fauna, bacteria, fungi and algae. Underground inhabitants. What insects can be found in the soil and should you be afraid of them? What animals live in the soil environment

There is a world hidden from us, inaccessible to direct observation - a unique world of soil animals. There is eternal darkness there; you cannot penetrate there without disturbing the natural structure of the soil. And only isolated, accidentally noticed signs show that beneath 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 holes, holes in gopher holes in the steppe or sand swallow holes in a cliff above the river, piles of earth on the path thrown out by earthworms, and the earthworms themselves crawling out after the rain, as well as masses unexpectedly appearing literally from underground winged ants or fatty larvae of chafers that are found in the ground.

As a habitat for animals, soil is very different from water and air. Try waving your hand in the air - you will notice almost no resistance. Do the same in water - you will feel significant resistance from the environment. And if you put your hand into a hole and cover it with earth, not only will it be difficult to 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 in the way, then the animal can advance only by breaking through a passage and raking the earth back or 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 to live. The conditions for breathing in soil are different than in water or air. Soil consists of solid particles, water and air. Solid particles in the form of small lumps occupy slightly more than half the volume of the soil; the rest of the volume accounts for the gaps - pores, which 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.

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

If the soil dries out, these animals secrete a protective shell and, as it were, fall asleep, falling into a state suspended animation Oxygen enters the soil air from the atmosphere: its amount in the soil is 1-2% less than in atmospheric air. Oxygen is consumed in the soil by animals, microorganisms, and plant roots through respiration. They all emit carbon dioxide. There is 10-15 times more of it in soil air than in the atmosphere. Free gas exchange between 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 have probably often observed.

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

Soil animals find their food either in the soil itself or on its surface. The life 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 substances extracted from it by plant roots to the soil.

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

Medvedka.

Not only earthworms “work” in the soil, but also their closest relatives - smaller whitish annelids (enchytraeids, or pot worms), as well as some types of microscopic roundworms (nematodes), small mites, various insects, especially their larvae, and finally woodlice, millipedes 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, and dig holes. All this increases the number of voids in the soil and facilitates the penetration of air and water into its depths. This “work” involves not only relatively small invertebrate animals, but also many mammals - moles, marmots, ground squirrels, jerboas, field and forest mice, hamsters, voles, and 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. Along these passages, especially 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, mole crickets, 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 plant bulbs. Those that attack cultivated plants or forest plantations are considered pests, for example the cockchafer. Its larva lives in the soil for about four years and pupates there. In the first year of life, it feeds mainly on the roots of herbaceous plants. But, as it grows, the larva begins to feed on the roots of trees, especially young pines, and causes great harm to the forest or forest plantations. The larvae of click beetles, darkling beetles, weevils, pollen eaters, caterpillars of some butterflies, such as cutworms, the larvae of many flies, cicadas and, finally, root aphids, such as phylloxera, also feed on the roots of various plants, greatly harming them.

Many insects that damage the above-ground parts of plants - stems, leaves, flowers, fruits - lay eggs in the soil; Here, the larvae that emerge from the eggs hide during drought, overwinter, and pupate. Soil pests include some species 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 functioning.

An antlion larva at the bottom of a sand funnel she created.

There are many predators living in the soil. “Peaceful” moles eat huge amounts of earthworms, snails and insect larvae; they even attack frogs, lizards and mice. These animals eat almost continuously. For example, a mole eats almost as much living matter in a day 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 protozoa, such as flagellates. The ciliates themselves serve as food for some roundworms. Predatory mites attack other mites and small insects. Thin, long, pale-colored centipedes are geophiles that live in cracks in the soil, as well as larger dark-colored drupes and centipedes that stay under stones and in stumps, also predators. They feed on insects and their larvae, worms and other small animals. Predators include spiders and related haymakers. Many of them live on the soil surface, in litter or under objects lying on the ground.

Many predatory insects live in the soil. These are ground beetles and their larvae, which play a significant role in exterminating pest insects, many ants, especially larger species, which destroy large numbers of harmful caterpillars, and, finally, the famous antlions, so named because their larvae hunt ants. The antlion 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 buries itself in the sand at the bottom, with only its jaws wide open. Small insects, most often ants, that fall on the edge of the funnel roll down. Then the antlion larva grabs the victim and sucks it out. Adult antlions resemble dragonflies in appearance, their body length reaches 5 cm, and their wingspan reaches 12 cm.

In some places, a predatory... mushroom is found in the soil! The mycelium of this fungus, which has the tricky name “didimozoophage,” forms special trapping rings. Small soil worms - nematodes - get into them. With the help of special enzymes, the fungus dissolves the rather durable shell of the worm, grows inside its body and eats it out completely.

In the process of evolution, the inhabitants of the soil have developed adaptations to the corresponding living conditions: features of the shape and structure of the body, physiological processes, reproduction and development, the ability to tolerate unfavorable conditions, and behavior. Earthworms, nematodes, most millipedes, and the larvae of many beetles and flies have a highly elongated flexible body that allows them to easily move through winding narrow passages and cracks in the soil. Bristles in earthworms and other annelids, hairs and claws in arthropods allow them to significantly accelerate their movements in the soil and stay firmly in burrows, clinging to the walls of passages. Look how slow

a worm crawls along the surface of the earth and at what speed, essentially instantly, it hides in its hole. When making new passages, some soil animals, such as worms, alternately extend and contract their bodies. In this case, cavity fluid is periodically pumped into the front end of the animal. It swells strongly and pushes away 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 that constantly live 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 animal world of the soil is very rich. It includes about three hundred species of protozoa, more than a thousand species of roundworms and annelids, tens of thousands of arthropods, hundreds of mollusks and a number of vertebrate species. Among soil animals there are both beneficial and harmful. But most of them are still listed under the “indifferent” heading. It is possible that this is the result of our ignorance. Studying them is the next task of science.

What animals live in the soil? and got the best answer

Answer from Yatyan[active]
Living organisms - inhabited soils
Various living organisms live in the soil - bacteria, microscopic fungi, small animals. Life in the soil is associated with a lack of light, difficulties in movement, high humidity or lack of water, and a large number of dying plant roots and plant debris on its surface.
Living organisms living in the soil have various adaptations to the soil environment. A mole, for example, has short front legs and faces not downwards, like those of land animals, but to the sides: the wide hands are turned back. The fingers with strong, sharp claws are connected by a leathery membrane. With such legs, the mole easily loosens the soil and makes holes in it. The mole's eyes are underdeveloped and hidden by fur. With them he distinguishes only light from darkness. The insect mole cricket has front legs, like those of a mole, digging, and the eyes are less developed than those of the cockchafer.
Moles and mole crickets constantly live in the soil. They can move from layers in which unfavorable living conditions are created to other layers of the soil. During drought and winter they move to deeper layers. In contrast, gophers, marmots, badgers, and rabbits feed on the surface of the soil, and in the burrows they make in the soil they reproduce, out of danger and bad weather.
Plants have developed adaptations, including root systems, to the dryness or moisture of the soil. On soils with a lack of moisture, plants form powerful roots that reach groundwater. Camel thorn, which grows in deserts, has roots that go down to a depth of 20 m.
In plants growing in highly humid places, the roots are located close to the surface of the soil, since in deeper layers, where water displaces all the air, the plant roots do not have enough air.
The soil is constantly inhabited by many invertebrate animals - ants, centipedes, worms, mites, beetles, larvae of beetles and flies, slugs, etc. All of them have adapted to life in the soil environment in their own way and play an important role in soil formation processes. Among them, the largest mass is made up of earthworms. The total mass of earthworms on Earth is 10 times greater than the mass of all humanity!

Answer from Yoman Lazarev[active]
moles, for example...

Answer from Joni[guru]
moles!

Answer from ABRAM[guru]
small, gray, lives 3 meters underground and eats stones

Answer from VladCo[guru]
All animals live in the ground, because they have burrows there, but most of them lead a terrestrial lifestyle. Moles, shrews, and dormice are almost always underground (3/4 years)

Answer from Olga Perminova[newbie]
for example: mole, earthworm

Answer from Kristina Protopopova[newbie]
Thank you!!! very detailed and clear

Answer from Lika[newbie]
Not only earthworms “work” in the soil, but also their closest relatives - smaller whitish annelids (enchytraeids, or pot worms), as well as some types of microscopic roundworms (nematodes), small mites, various insects, especially their larvae, and finally woodlice, millipedes 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, and dig holes. All this increases the number of voids in the soil and facilitates the penetration of air and water into its depths. This “work” involves not only relatively small invertebrate animals, but also many mammals - moles, marmots, ground squirrels, jerboas, field and forest mice, hamsters, voles, and 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. Along these passages, especially 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, mole crickets, crickets, tarantula spiders, ants, and in the tropics - termites.

Answer from Yorgey Blinov[newbie]
Worms, mole crickets, ants, mole, antlion....

Answer from Marina Karpushkina[newbie]
Well, for example, a bear, a mole, a dormouse, and a fox

Answer from Jurassic blue[newbie]
moles

Answer from Natalie[newbie]
mole worm spider bugs...
well, I do not know

Answer from Polina Yakovleva[newbie]
centipede, mole cricket, mole, earthworm.

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 overwhelming majority of the microbial population is adsorbed on them. The complexity of the soil environment creates a wide variety of conditions for a wide variety of functional groups: aerobes and anaerobes, consumers of organic and mineral compounds. The distribution of microorganisms in the soil is characterized by fine focality, since even within a few millimeters different ecological zones can change.

For small soil animals (Fig. 52, 53), which are combined under the name microfauna (protozoa, rotifers, tardigrades, nematodes, etc.), soil is a system of micro-reservoirs. Essentially, these 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 also live in ordinary bodies of water. However, soil forms are much smaller than freshwater ones and, in addition, are distinguished by their ability to remain in an encysted state for a long time, waiting out unfavorable periods. While freshwater amoebas have sizes of 50-100 microns, soil amoebas 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 their body shape.

Rice. 52. Testate amoebas feeding on bacteria on decaying leaves of the forest floor

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

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

To slightly larger air-breathing animals, the soil appears as a system of small caves. Such animals are grouped under the name mesofauna (Fig. 54). The sizes of soil mesofauna representatives range from tenths to 2-3 mm. This group includes mainly arthropods: numerous groups of mites, primary wingless insects (collembolas, proturus, two-tailed insects), small species of winged insects, symphila centipedes, etc. They do not have special adaptations for digging. They crawl along the walls of soil cavities using their limbs or wriggling like a worm. Soil air saturated with water vapor allows breathing through the covers. Many species do not have a tracheal system. Such animals are very sensitive to drying out. The main means of escape from fluctuations in air humidity is to move deeper. But the possibility of deep migration through soil cavities is limited by a rapid decrease in pore diameter, so movement through soil holes is accessible only to the smallest species. Larger representatives of the mesofauna have some adaptations that allow them to tolerate 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 ensures respiration.

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

1 - false scorion; 2 - gama new bell-bottom; 3-4 oribatid mites; 5 - centipede pauroioda; 6 - chironomid mosquito larva; 7 - a beetle from the family. Ptiliidae; 8-9 springtails

Representatives of the mesofauna survive periods of soil flooding in air bubbles. Air is retained around the body of animals due to their non-wettable integument, which is also equipped with hairs, scales, etc. The air bubble serves as a kind of “physical gill” for a small animal. Respiration 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 move down from layers exposed to negative temperatures.

Larger soil animals, with body sizes from 2 to 20 mm, are called representatives macrofauna (Fig. 55). These are insect larvae, centipedes, enchytraeids, 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 tunnels. Both methods of movement leave an imprint on the external structure of animals.

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

1 - earthworm; 2 - woodlice; 3 - centipede; 4 - two-legged centipede; 5 - ground beetle larva; 6 - click beetle larva; 7 - mole cricket; 8 - Khrushchev larva

The ability to move through thin holes, almost without resorting to digging, is inherent only in species that have a body with a small cross-section, capable of bending strongly in winding passages (centipedes - drupes and geophiles). Moving apart soil particles due to the pressure of the body walls, earthworms, larvae of long-legged mosquitoes, etc. move. Having fixed the rear end, they thin and lengthen the front, penetrating into narrow soil crevices, then secure the front part of the body and increase its diameter. In this case, in the expanded area, due to the work of the muscles, a strong hydraulic pressure of the non-compressible intracavitary fluid is created: in worms - the contents of the coelomic sacs, and in tipulids - the hemolymph. Pressure is transmitted through the body walls to the soil, and thus the animal expands the well. At the same time, the rear passage remains open, which threatens to increase evaporation and persecution of predators. Many species have developed adaptations to an ecologically more advantageous type of movement in the soil - digging and blocking the passage behind them. Digging is carried out by loosening and raking away soil particles. The larvae of various insects use for this the anterior end of the head, mandibles and forelimbs, expanded and strengthened by a thick layer of chitin, spines and outgrowths. At the rear 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 and in bark beetles, which also use them to clog passages with drill flour. Closing the passage behind them, the animals that inhabit the soil are constantly in a closed chamber, saturated with the vapors of their own bodies.

Gas exchange of most species of this ecological group is carried out with the help of specialized respiratory organs, but at the same time it is supplemented by gas exchange through the integument. It is even possible to perform exclusively cutaneous respiration, for example in earthworms and enchytraeids.

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

Megafauna soils are large shrews, mainly mammals. A number of species spend their entire lives in the soil (mole rats, mole rats, zokora, Eurasian moles, golden moles

Africa, marsupial moles of Australia, etc.). They create entire systems of passages and burrows in the soil. The appearance and anatomical features of these animals reflect their adaptability to a burrowing underground lifestyle. They have underdeveloped eyes, a compact, ridged body with a short neck, short thick fur, strong digging limbs with strong claws. Mole rats and mole rats loosen the ground with their incisors. Soil megafauna also includes large oligochaetes, especially representatives of the family Megascolecidae, living in the tropics and the Southern Hemisphere. 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 inhabitants (gophers, marmots, jerboas, rabbits, badgers, etc.). They feed on the surface, but reproduce, 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. Burrowers have structural features characteristic of terrestrial animals, but have a number of adaptations associated with the burrowing lifestyle. For example, badgers have long claws and strong muscles on the forelimbs, a narrow head, and small ears. Compared to hares that do not dig holes, rabbits have noticeably shortened ears and hind legs, a more durable skull, more developed bones and muscles of the forearms, etc.

For a number of ecological features, soil is a medium intermediate between aquatic and terrestrial. The soil is similar to the aquatic environment due to its temperature regime, low 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, and rather sharp changes in the temperature regime of the surface layers.

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

Many animals and insects live under the surface of the earth, we present to your attention the rating of the Top 10 creatures that live underground

A small burrowing rodent of the mole rat family. It is distinguished by a unique social structure for mammals, cold-bloodedness, insensitivity to acids, insensitivity to pain, and tolerance to CO2 concentrations. It is the longest-living of rodents, up to 28 years. Look at him - he's terrible.

2.

The largest representative of the mole rat subfamily: its body length is 25-35 cm, weight reaches 1 kg. The color of the upper body is light, gray-fawn or ocher-brown. Leads a strictly underground, sedentary lifestyle, building multi-tiered systems of passages. It digs the ground mainly with its incisors. Underground feeding passages (11-16 cm in diameter) are laid at a depth of 20-50 cm, often in layers of sand. On the surface of the earth they are indicated by soil emissions in the form of truncated cones 30-50 cm high, weighing 10 kg or more. The total length of the feed tunnels reaches 500 meters. Nesting chambers and storerooms are located at a depth of 0.9 to 3 m. I have come across such a comrade, he has terrible teeth, don’t even try to pick him up, with his teeth he is able to bend the bayonet of a shovel.

class mammals order insectivores. Widely distributed in Eurasia and North America. These are small and medium-sized insectivores: body length from 5 to 21 cm; weight from 9 to 170 g. Moles are adapted to an underground, burrowing lifestyle. Their body is elongated, round, covered with thick, smooth, velvety fur. The mole coat has a unique property - its pile grows straight, and is not oriented in a certain direction. This allows the mole to easily move underground in any direction.

Small rodents whose weight reaches 700 g. Body length 17-25 cm, tail 6-8 cm. Morphological characteristics show a high degree of adaptability to the underground lifestyle. They lead an underground lifestyle, building complex branched systems of passages with nesting chambers, storerooms and latrines. For construction, tuco-tucos prefer loose or sandy soils.

The body length of gophers is from 9 to 35 cm, the tail is from 4 to 14 cm. The weight of some Central American species can reach a kilogram. Gophers spend most of their lives in complex underground passages laid in different soil horizons. The length of such tunnels reaches 100 meters.

Snake of the cylindrical family. It is small in size and has a dense constitution. The body is black in color with two rows of large brown ones. Leads an underground lifestyle, feeding on earthworms.

A fish that spends most of its time in the bottom mule, and when the reservoir dries up, crucian carp burrows into the silt to a depth of 1 to 10 meters and can live in this state for several years.

a large insect, body length (without antennae and cerci) up to 5 centimeters. The abdomen is approximately 3 times larger than the cephalothorax, soft, fusiform, with a diameter in adults of about 1 cm. At the end of the abdomen, paired thread-like appendages are noticeable - cerci, up to 1 cm long. The insect leads a predominantly underground lifestyle, but flies well and runs on the ground and floats. It rarely comes to the surface, mainly at night.

The length of adult individuals (imago) of the eastern species is 25-28 mm, of the western species 26-32 mm. The body is black, with red-brown elytra. In the adult stage (imago), the beetles appear on the surface of the earth at the end of April or May and live for about 5-7 weeks. After approximately 2 weeks, mating occurs, after which the female begins to lay eggs, placing them underground at a depth of 10-20 cm. This process can occur in several stages, and a complete clutch is 60-80 eggs. Having finished laying, the female cockchafer immediately dies.

The body of earthworms is up to 2 m long and consists of many ring-shaped segments 80 - 300. When moving, earthworms rely on short bristles located on each segment except the front one. The number of bristles varies from 8 to several dozen. Earthworms live on all continents except Antarctica, but only some species originally had a wide geographic range, the rest were introduced by humans.

4.3.2. Soil inhabitants

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 overwhelming majority of the microbial population is adsorbed on them. The complexity of the soil environment creates a wide variety of conditions for a wide variety of functional groups: aerobes and anaerobes, consumers of organic and mineral compounds. The distribution of microorganisms in the soil is characterized by fine focality, since even within a few millimeters different ecological zones can change.

For small soil animals (Fig. 52, 53), which are combined under the name microfauna (protozoa, rotifers, tardigrades, nematodes, etc.), soil is a system of micro-reservoirs. Essentially, these 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 also live in ordinary bodies of water. However, soil forms are much smaller than freshwater ones and, in addition, are distinguished by their ability to remain in an encysted state for a long time, waiting out unfavorable periods. While freshwater amoebas are 50-100 microns in size, soil amoebas 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 their body shape.

Rice. 52. Testate amoebas feeding on bacteria on decaying leaves of the forest floor

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

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

To slightly larger air-breathing animals, the soil appears as a system of small caves. Such animals are grouped under the name mesofauna (Fig. 54). The sizes of soil mesofauna representatives range from tenths to 2–3 mm. This group includes mainly arthropods: numerous groups of mites, primary wingless insects (collembolas, proturus, two-tailed insects), small species of winged insects, symphila centipedes, etc. They do not have special adaptations for digging. They crawl along the walls of soil cavities using their limbs or wriggling like a worm. Soil air saturated with water vapor allows breathing through the covers. Many species do not have a tracheal system. Such animals are very sensitive to drying out. The main means of escape from fluctuations in air humidity is to move deeper. But the possibility of deep migration through soil cavities is limited by a rapid decrease in pore diameter, so movement through soil holes is accessible only to the smallest species. Larger representatives of the mesofauna have some adaptations that allow them to tolerate 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 ensures respiration.

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

1 – false scorion; 2 – gama new bell-bottom; 3–4 oribatid mites; 5 – centipede pauroioda; 6 – chironomid mosquito larva; 7 - beetle from this family. Ptiliidae; 8–9 springtails

Representatives of the mesofauna survive periods of soil flooding in air bubbles. Air is retained around the body of animals due to their non-wettable integument, which is also equipped with hairs, scales, etc. The air bubble serves as a kind of “physical gill” for a small animal. Respiration 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 move down from layers exposed to negative temperatures.

Larger soil animals, with body sizes from 2 to 20 mm, are called representatives macrofauna (Fig. 55). These are insect larvae, centipedes, enchytraeids, 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 tunnels. Both methods of movement leave an imprint on the external structure of animals.

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

1 - earthworm; 2 – woodlice; 3 – centipede; 4 – two-legged centipede; 5 – ground beetle larva; 6 – click beetle larva; 7 – mole cricket; 8 - Khrushchev larva

The ability to move through thin holes, almost without resorting to digging, is inherent only in species that have a body with a small cross-section, capable of bending strongly in winding passages (centipedes - drupes and geophiles). Moving apart soil particles due to the pressure of the body walls, earthworms, larvae of long-legged mosquitoes, etc. move. Having fixed the rear end, they thin and lengthen the front, penetrating into narrow soil crevices, then secure the front part of the body and increase its diameter. In this case, in the expanded area, due to the work of the muscles, a strong hydraulic pressure of the non-compressible intracavitary fluid is created: in worms - the contents of the coelomic sacs, and in tipulids - the hemolymph. Pressure is transmitted through the body walls to the soil, and thus the animal expands the well. At the same time, the rear passage remains open, which threatens to increase evaporation and persecution of predators. Many species have developed adaptations to an ecologically more advantageous type of movement in the soil - digging and blocking the passage behind them. Digging is carried out by loosening and raking away soil particles. The larvae of various insects use for this the anterior end of the head, mandibles and forelimbs, expanded and strengthened by a thick layer of chitin, spines and outgrowths. At the rear 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 and in bark beetles, which also use them to clog the passages with drill flour. Closing the passage behind them, the animals that inhabit the soil are constantly in a closed chamber, saturated with the vapors of their own bodies.

Gas exchange of most species of this ecological group is carried out with the help of specialized respiratory organs, but at the same time it is supplemented by gas exchange through the integument. It is even possible to perform exclusively cutaneous respiration, for example in earthworms and enchytraeids.

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

Megafauna soils are large shrews, mainly mammals. A number of species spend their entire lives in the soil (mole rats, mole rats, zokora, Eurasian moles, golden moles

Africa, marsupial moles of Australia, etc.). They create entire systems of passages and burrows in the soil. The appearance and anatomical features of these animals reflect their adaptability to a burrowing underground lifestyle. They have underdeveloped eyes, a compact, ridged body with a short neck, short thick fur, strong digging limbs with strong claws. Mole rats and mole rats loosen the ground with their incisors. Soil megafauna also includes large oligochaetes, especially representatives of the family Megascolecidae, living in the tropics and the Southern Hemisphere. 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 inhabitants (gophers, marmots, jerboas, rabbits, badgers, etc.). They feed on the surface, but reproduce, 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. Burrowers have structural features characteristic of terrestrial animals, but have a number of adaptations associated with the burrowing lifestyle. For example, badgers have long claws and strong muscles on the forelimbs, a narrow head, and small ears. Compared to hares that do not dig holes, rabbits have noticeably shortened ears and hind legs, a more durable skull, more developed bones and muscles of the forearms, etc.

For a number of ecological features, soil is a medium intermediate between aquatic and terrestrial. The soil is similar to the aquatic environment due to its temperature regime, low 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, and rather sharp changes in the temperature regime of the surface layers.

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