Breathing of flatworms. How do flatworms breathe?

The earthworm that interests us also belongs to the oligochaete annelids. Why ringed? Yes, all because its body consists of rings, the number of which can vary, just like the size of the worm. Almost everyone, as a child (maybe an adult) wondered where the worm’s tail is and where its head is? Since it is quite difficult to do this by simply looking at him, using the figure below we can, without much effort, determine where his “belt” is located (a special thickening), with the help of which we find out where his head is located . The “belt” is not located in the middle of the worm, but is shifted to one end of the worm, this is its head, accordingly, further than the “belt” there will be a tail.

The worm has two sides, where one side is compacted - this is the head of the worm (front end), and the other side is thinner and lighter - this is the tail of the worm (rear end). I would like to note that the worm also has an upper part and a belly.

I think the question is about earthworms/earthworms/dungworms. Interesting answers, but: if you cut it, then only the head will survive, and not always. But by passing them through their teeth, they recognize whether it is a male or a female - it’s stuck, which means it’s a male (the genitals are being pushed through, it’s all a joke, of course). And so to the worms. How do you figure out where the head is and where the tail is? There are about a thousand of their species on Earth and they range from 1 cm to 3 meters. In the countries of the former USSR there are more than a hundred different species alone. Dung, rain, earth, swamp, crawl, prospector and Californian (these are bred breeds), these are the ones I have personally seen. It is easy to distinguish when a worm has a seal ring on its body - this is their uterus and it is located closer to the head. However, it is not visible in the fetid and swamp ones and the rings of the pattern along the body make them completely identical. But still the tail is lighter than the head and there is an anus there. Press down and the worm will crap itself with humus. I haven’t seen others, maybe they have their own differences. It’s interesting to see the Australian one, it grows up to 3 meters. I could have one like this for my entire vegetable garden. I would sell humus to my neighbors :-).

Among some flower gardeners, there is a widespread belief about the harm that earthworms can cause. Which (allegedly) gnaw roots in pots, gnaw at young shoots, eat seedlings, sprouts, seeds, etc. To destroy worms, they come up with different methods, the most harmless of which is freezing the soil. And what’s most offensive is that they say (especially on the Internet) all sorts of unfounded nasty and stupid things about earthworms...

Let's figure it out - how justified are such fears? And to do this, let’s carefully look at this picture (picture taken from here) to understand: how do worms feed, and do they have teeth?

Since ancient times, humanity has paid special attention to such unsightly creatures as the earthworm. And scientific minds, in the person of Charles Darwin, decades later, studied their structure and significance in agriculture for many years. And not without reason. Indeed, with the onset of spring warmth, earthworms begin painstaking work and work, without knowing it, for the benefit of people.

Variety of worms

The phylum Worms includes groups of multicellular animals that have an elongated body and no skeleton. Habitats are usually moist soil, sea and fresh water bodies. They can vary in size from those that can only be detected with a microscope, to large forms several meters long. According to the shape of the body, they are divided into: Flatworms, Roundworms and Ringworms. All types have three body layers. The germ layers - ectoderm, endoderm and mesoderm give rise to the development of all their tissues and organs.

The most striking and famous representatives of flatworms: planaria, liver fluke, pork and bovine tapeworms, echinococcus, schistosome, etc. Well-known annelids include the earthworm, oligochaete worms, leeches and mysostomids. Round protostomes are represented by the well-known roundworms, pinworms, guinea worms, trichinella, etc.

Despite the diversity of existing species of worms, their types, structural features, methods of reproduction, feeding, habitats, etc., there are a considerable number of similarities that are characteristic of all of them. For example, the respiration of flatworms, divided into aerobic and anaerobic, depending on the habitat, is also characteristic of the other two types.

Earthworms

For a more complete introduction to the topic, below is information about earthworms from a classic English biology textbook: Biology

D. Taylor, N. Green, W. Stout (DJTaylor, NPOGreen, GWStout BIOLOGICAL SCIENCE)

Earthworm

(
Lumbricus terrestris
) is an animal with a long cylindrical body, reaching a length of approximately 12–18 cm. Its anterior end is cone-shaped, and its posterior end is flattened in the dorsoventral direction.

And although the earthworm lives on land, it could not completely overcome all the problems associated with a terrestrial lifestyle. To escape drying out, it lives underground, digging a hole in damp soil, and leaves it only at night, going in search of food or a sexual partner.

Differences in the external body structure of the polychaete worm ( Nereis

) and earthworm are due to the latter’s adaptation to a terrestrial lifestyle. The earthworm's body has a streamlined shape and is devoid of any outgrowths, the presence of which could interfere with the free movement of the worm in the soil.

The prostomium (head lobe - first segment) is located above the mouth, it is small and round, there are no sensory appendages on it. All segments, with the exception of the first and last, bear four pairs of setae; two of them are located ventrally (on the ventral side), and two are located dorsolaterally.

The setae emerge from setal sacs located in the body wall. They can be pulled in or pulled out under the action of special muscles. The bristles facilitate the movement of the worm along the ground, and are also used for protection: by clinging to the walls of the burrow, the worm is firmly held in it.

The longest setae, located on segments 10–15, 26 and 32–37, are used during copulation. Another structure used in copulation is the girdle, located on segments 32–37. The epidermis of the girdle contains many glandular cells that form a certain thickening on the dorsal and lateral surfaces, resembling a saddle in shape. The girdle is involved in the processes of copulation and cocoon formation.

The mouth and anus of the worm are located at opposite ends of the body. The earthworm feeds on detritus (fragments of decaying organic material), which the worm ingests along with the soil. The vast majority of the absorbed soil passes through the intestines and is then released to the soil surface in the form of characteristic heaps.

The coelomic fluid released through the dorsal pores and mucus secreted by the glandular cells of the epidermis constantly moisturize the thin cuticle. As a result, the cuticle is prevented from drying out, gas exchange is facilitated and a kind of lubricant is created that facilitates the movement of the worm in the soil. It is through the cuticle that gas exchange occurs by diffusion - a process dependent on the presence of an extensive network of capillaries in the epidermal layer.

All segments, with the exception of the first three and one last, carry a pair of nephridia - tubules that perform the functions of excretion and osmoregulation. They open into pores on the surface of the body.

The reproductive system of the earthworm, as well as the behavior associated with reproduction, is highly complex, which may be explained by its terrestrial lifestyle and the need to protect gametes and fertilized eggs from drying out. Lumbricus is hermaphrodite (that is, each individual has both male and female reproductive organs).

Contact of earthworms with each other occurs very rarely, but when this happens, any two individuals can mate, since they are both hermaphrodites. As a result, sperm are exchanged and both worms are fertilized. The reproductive organs of earthworms are concentrated at the anterior end of the body. External signs associated with sexual reproduction are shown in the figure below. Mating and subsequent laying of fertilized eggs is a very complex process. Mating individuals are located next to each other in mutually opposite directions, so that the head of one of the partners is directed towards the tail of the other and vice versa (see photo).

The anterior end of an earthworm (ventral view) Reproduction of earthworms 1. Scheme of the structure of the head of an earthworm

Note. Photo and illustration from the Biology

(Peter H. Raven, Kenneth A. Mason, Jonathan B. Losos Susan R. Singer)

Earthworms feed on detritus

Detritus

is fresh or decomposed organic matter typically found on the soil surface. Organisms that feed on detritus are called detritivores or detritivores. An example of such animals are earthworms. Detritivores are usually involved in the first stage of processing dead material and therefore play an important role in the ecosystem.

The earthworm consumes fragments of detritus, especially plant remains found on the soil surface or in a burrow where they are dragged by the animal. Pieces of food are crushed, moistened with an alkaline secretion secreted by the pharynx, and swallowed. Earthworms can also feed on organic matter in the soil, which they ingest while digging burrows.

The earthworm's digestive tract looks like a straight tube that extends from the mouth to the anus. Each section has its own specialization in the digestion and absorption of ingested food. Any undigested material is excreted through the anus in the form of characteristic pellets.

Charles Darwin was the first to draw attention to the important role of earthworms in maintaining the structure and fertility of the soil. Fertile soil can contain up to two million earthworms per hectare. Passing through the intestines of the worm, the soil is crushed and enriched with various elements, and then carried to the surface in the form of excrement. This improves its structure and provides a kind of plowing. According to rough estimates, this soil turnover is about 50 tons per hectare per year. The end products of the worms' nitrogen metabolism in turn add nutrients to the soil; these substances can later be used by plants.

Binding excess calcium in the form of its salts reduces soil acidity, which generally improves plant growth. The tunnels dug by worms provide good soil aeration and drainage, resulting in more oxygen reaching the plant roots. By dragging detritus from the soil surface into their burrows, earthworms increase the overall rate of organic matter decomposition and ecosystem productivity.

Gas exchange in earthworms

The earthworm belongs to the group of annelids. It does not have any special organs specifically designed for gas exchange, and gas exchange occurs by diffusion across the entire surface of the body. In essence, they do not need specialized organs, since, due to the cylindrical shape of the body, their surface area to volume ratio is large, and with their relatively low activity, they do not consume much oxygen.

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

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

Earthworm circulatory system

Annelids are characterized by the presence of a secondary body cavity (coelom), due to which the body walls are separated from the internal organs; this ensures relative independence of movements of, for example, the internal structures of the animal, such as the intestine. However, with the development of the coelom, the need arose for the development of a transport system that ensures communication of all parts of the body with each other, as well as with the external environment. Therefore, it is at the level of the secondary cavities that the circulatory system first appears, connecting the intestine and the body wall. An earthworm, for example, has a well-developed circulatory system, and blood circulates throughout the body in a closed system of blood vessels.

There are two main vessels running along the entire length of the earthworm’s body: the dorsal (dorsal) and the ventral (ventral). In each segment they are connected to each other by transverse bridges. At the anterior end of the animal, five pairs of such transverse vessels are capable of contracting rhythmically and play the role of pumps. However, the main vessels also perform a certain pumping function.

Blood contains the red pigment hemoglobin, which is dissolved in its plasma, and is not concentrated in special cells (red blood cells, or erythrocytes), as in vertebrates. Hemoglobin carries oxygen throughout the body.

Nervous system of an earthworm

In annelids (an example is the earthworm), the union of neurons led to the formation of a nervous system consisting of one longitudinal cord running along the entire length of the body - the ventral nerve cord. This chain consists of segment-by-segment paired nodes (ganglia) connected by nerve cords. Segmental nerves extend from each node to the organs and tissues of this segment.

Due to the unidirectional method of locomotion (movement), these animals have a separate head. This structure helps to find and swallow food and, since it is the first to encounter new elements of the environment, it is in it that the main sensory organs that perceive information from the outside are concentrated. The increased flow of information from these organs into the nervous system led to the thickening of the anterior nerve ganglia, i.e., the formation of a kind of primitive “brain”.

This concentration of foraging, sensory and nervous structures in the head region is called cephalization

, i.e. simply by the development of the head.
It should be noted that this term refers to the development of all the features that distinguish the head from the rest of the body, not just the development of the brain. In the latter case they talk about encephalization
.

The nervous system of annelids is built according to a plan typical of all other invertebrate animals. The expanded anterior part of the nerve chain forms a pair of cerebral ganglia (head nodes), located above the pharynx and connected to the abdominal nerve chain by peripharyngeal cords.

Locomotion in an earthworm

The movement of an entire living organism from one place to another is called locomotion.

.

Locomotion with the help of muscles is possible only in the presence of a skeleton. In annelids, such as earthworms, it is hydrostatic, i.e. formed by coelomic fluid, the pressure of which maintains and changes the shape of the body.

The body cavity (whole) of the earthworm is surrounded by walls consisting of two layers of antagonist muscles: the outer annular and the inner longitudinal. Intersegmental septa divide the animal's circular muscles into independent units, while the longitudinal muscles extend through several segments. Locomotion is accomplished through the coordinated activity of both muscle layers, as well as the muscles that move the setae located on the underside of the worm's body.

When an earthworm moves forward, contraction of the annular muscles begins at the anterior end of the body and, seizing segment by segment, spreads in a wave through the entire body. The contracted muscles in each segment press on the coelomic fluid, which stretches the relaxed longitudinal muscles and changes the shape of the segment - it becomes longer and thinner. Thanks to this, the front end of the worm moves forward. The setae, present on all segments of the body except the first and last, are retracted during contraction of the annular muscles and thus do not interfere with the forward movement of the body.

As the front end of the body moves, the longitudinal muscles at its rear end contract, and this part of the body, thickening, is pressed against the surrounding soil. The bristles here come out and help this section stay in place. This is of particular importance when digging, since as the worm moves forward, it can put forceful pressure on the soil. Following the circular muscles, the longitudinal ones quickly begin to contract, and this wave of contraction also passes along the entire length of the body.

Thus, at different times, different parts of the body can move forward (with contraction of the circular muscles) or remain motionless (with contraction of the longitudinal muscles). The net effect is a smooth peristaltic wave of contractions running along the entire body of the worm as it moves forward. By changing the sequence of muscle contractions (i.e., the direction of the wave), the worm is able to crawl backward.

Muscle function is controlled by a complex network of intra- and intersegmental neurons. The abdominal nerve chain passes through the segments, and each of them has its own segmental nerves. This allows you to control the work of each individual segment and the entire organism as a whole. The ventral nerve cord contains a giant axon that stretches along the entire body of the animal and conducts impulses from the anterior end to the posterior. When the sensitive receptors of the head are irritated, impulses travel along the giant axon to the longitudinal muscles, causing them to contract and, as a result, the anterior end of the body moves away from the stimulus. The ventral chain also contains two longitudinal lateral fibers that conduct impulses from the posterior end to the head. If the stimulus acts in the region of the posterior end, then impulses along the lateral nerves are transmitted to the head end and ensure that the posterior part of the body is pulled forward. This is the basis of avoidance reactions in earthworms.

Locomotion of an earthworm Segmental innervation of the longitudinal muscles of an earthworm (view from the dorsal side). The circular muscles are innervated in a similar way.

Flatworms

Let's start with the general characteristics of worms. Flatworms are invertebrate animals belonging to the protostomes. These creatures belong in the taxonomic hierarchy to animals of the multicellular type, having an elongated body shape and the absence of an internal skeleton. Zoology of the type Flatworms is a description of the structure, life processes and physiology of these creatures. They are inhabitants of salt and fresh water bodies; other representatives can survive in places with high humidity. The remaining classes are engaged in parasitism, living on a variety of animals, including vertebrates and invertebrates. Currently, approximately 25,000 species have been described; over three thousand species live on the territory of the Russian Federation.

The organ system of flatworms is represented by a number of main structural components, united by common functional characteristics and type of structure. The main systems include: respiratory, reproductive, excretory, muscular, nervous and integumentary.

Some representatives of flatworms, for example, planaria, inhabit fresh water bodies. Among eyelash worms, this is the most famous. Parasites include flukes, for example, liver and cat flukes, schistosomes, as well as tapeworms (broad tapeworms, bovine and pork tapeworms, echinococci).

Previously, a number of other taxonomic elements characterized by worm-like forms, lack of body cavities, and considered invertebrates were assigned to the class of ciliated protostomes.

The body shape of any type has a bilaterally symmetrical shape, in which the head and tail ends are pronounced, both ends are slightly flattened, however, in large species, the flattening is strongly pronounced. The organ system of flatworms for respiration and blood circulation is absent. A body cavity does not develop, but this is true for all representatives except tapeworms and flukes in certain life cycles.

Without the return of the earthworm to the field, humanity will not survive

Earthworms are large soil invertebrate animals, the most ancient and numerous on Earth.

They belong to the rain family, the order of higher oligochaetes, the class of oligochaetes, the subtype of zonules, the type of annelids, the subkingdom of metazoans, the animal kingdom.

Worms are an important part of soil biota and are found throughout the world. They live on all continents except Antarctica.

The total biomass of earthworms is greater than the biomass of all living creatures on our planet. There are more than 1,500 species on Earth, 35 species are common in Europe, and about 100 in the former USSR. The common earthworm and the dung worm are probably the most famous species. All other species of earthworms are biologically similar to them, with the exception of certain characteristics.

Small earthworms reach a length of only 1-2 cm, medium ones - 10-20 cm, while for the giant worm Megacolices australis (Australia) a length of up to 3 meters with a diameter of 2.5 cm has been recorded.

Earthworms differ not only in families, genera and species, but also in types of food and habitat in the soil:

1) feeding on organic matter on the soil surface, among them:

• surface-dwelling, living in the ground litter of fallen leaves, dead grass, half-rotten branches, as well as in composts,
• digging deep holes (up to a meter or more),

2) feeding on soil humus or the soil itself, among them:

• living in the upper part of the soil,
• living at medium depths (20-40 cm),
• burrowers living in deep layers of soil.

3) There are also amphibian worms.

Thus, the root systems of plants in living soil are located in the layer that is the natural habitat of earthworms (drillosphere). Scientists have proven that the soil adjacent to the hole left by the worm is populated by microorganisms to a layer thickness of about 2 mm. And the inner surface of the passages in living soil (at the entire feeding depth of earthworms ) can be 5 m2 per 1 m2 of soil surface.

As for the depth of their penetration, a thick and surprisingly strong worm , whose passages pierce the ground to a depth of eight meters.

Worms inhabit all layers of the soil. Therefore, all dead plant organic matter passes through their intestines more than once and itself turns into soil, thanks to the amazing properties of earthworms .

Earthworms can feed on any food containing organic matter. They can eat fallen leaves, dead herbaceous plants, rotted manure and the soil itself. By digesting dead plant organic matter, they convert it into small soil lumps. These earthworm are called coprolites (from the ancient Greek “κοπροζ” (droppings) and “λίθοζ” (stone)).

Coprolites of natural worm populations contain 11–15% humus per dry matter. Due to the mucus that envelops them, they are durable and water does not wash them away, but only wets them and seeps further into the soil. Coprolites contain increased amounts of nitrogen, phosphorus and potassium. Worms transfer these elements necessary for plants from an inaccessible form to an accessible one. During the digestion of plant residues, humic substances are formed in the digestive tract of worms . They differ in chemical composition from humus formed in the soil with the participation of microflora in that in the digestive canal of worms the processes of polymerization of low-molecular-weight decay products of organic substances develop and molecules of humic acids are formed. These acids enter into complex compounds with the mineral components of the soil, forming stable aggregates that remain in the soil for a long time. In this way, worms create loose, fertile soil saturated with air, moisture and nutrients available to plants.

There are no more powerful humus formers in nature. It is not yet possible to create humus and restore soil fertility in other ways.

Over the past two decades, their main merit has been proven not only in the formation of fertile soil, but also in its neutralization from pathogenic flora and many toxic substances, including radionuclides and heavy metals. Having passed through the intestines of any worm , all this pathogenic flora (bacteria, algae, fungi with their spores, protozoa of the animal world, including nematodes) is destroyed, and radionuclides and heavy metals are converted into insoluble compounds inaccessible to plants and they are already safe , remain in the soil for eternal storage. The intestinal microflora of the earthworm produces fungicidal and bactericidal substances. At the same time, the organic mass processed by the worms loses its odor, takes on the form of granules and a pleasant smell of earth. These are real deodorizers and sanitary workers, soil improvers. No one and nothing can compare with earthworms The more earthworms in the soil, the healthier and more functional it is, the more humus it contains - the most valuable and most necessary fertilizer for it.

One hectare of soil not destroyed by chemicals and plowing can contain from 1 to 200 million earthworms , and the weight of biomass ranges from 2 to 10 tons per hectare, i.e. 10 times more than all land animals in the same area. If earthworms are weighed, then on a hectare of well-groomed pasture the scales will tip in their direction, even if on the opposite side there is an entire herd of cows grazing in the meadow. If we take into account that a worm passes through its body per day an amount of soil equal to its weight, then with an average weight of a worm of half a gram and their number is 100 pieces. / sq. m (i.e. 1 million per hectare), it turns out that per day they pass through themselves 50 g of earth per square meter. Taking into account the fact that the activity of the worm in the middle zone is 200 days a year, during the season this figure increases to 10 kg / sq. m. or 100 t/ha – no comments needed!!! And this is with a minimum number of them...

As a matter of fact, only thanks to the multimillion-year activity of thousands of different species of worms, soil appeared on our mother Earth, neutralized from the products of volcanic eruptions, fires, and natural radioactivity. Earthworms this kind of work on land all over the globe, and no one can replace them in this role.

Earthworms do not get sick and are not subject to any epidemics.

Ultraviolet radiation from the sun is harmful to earthworms . Therefore, twilight and darkness are their constant companions. Many enemies have taught them to be extremely cautious and timid. The soil is their home. Some species hardly appear on the surface. Others do this often, but only at night, remaining in their burrows during the day. Climbing up, the earthworm is securely attached to the burrow by its tail bristles, so that in case of danger it can instantly be drawn into it. The front part of its body is capable of stretching into a thin sensitive proboscis. With it, the worm carefully probes the space around itself. Earthworms can move (at night and during rain during the day) quite long distances not only along the horizontal surface of the soil, but also along vertical obstacles up to several meters high, at a speed of up to 1 meter per minute. But the rate of natural spread of earthworms is only a meter per year.

Earthworms reproduce slowly. Those with red pigmentation lay no more than a hundred cocoons per year, and the 30-centimeter inhabitant of the soil, popularly called a crawler, lays even less - 40 cocoons. The life span of a crawl is also short - 5...6 years.

In 1985, near the city of Bass (Australia), John Matthews created the Museum - an attraction for the giant earthworm (as it is called in Australia). This worm can reach 3-4 m long! It is the largest invertebrate in the world. A museum to match a worm: a huge 100-meter building in the shape of an earthworm. In this Museum you can travel through the worm's passages and inside the worm itself. Not only to literally come face to face with the largest known animal living in the mysterious underground world, but also to get to know it from the inside.

Charles Darwin established that “ earthworms pass through the entire arable layer of soil in a few years ( they passed through them in Darwin’s time ). They enrich depleted lands with fresh humus, loosen them, and at the same time fertilize them with their secretions. Burrowing in the ground and swallowing it, they create a strong lumpy “soil-air” structure, and moisture penetrates deeper into the soil better. Countless worm holes, like a capillary network of living tissue, provide ideal drainage and ventilation of the soil.”

His work, “The Formation of the Vegetative Layer by the Activity of Earthworms,” is one of the most interesting and significant in natural history.

How do worms and do they have teeth? Figure 1 shows a fragment of an earthworm device.

The pharynx is an organ for absorbing food, working on the principle of a rubber bulb: when compressed and then unclenched, a vacuum is created, due to which food is drawn inside.

It is clear that there are no teeth in the mouth, so the worm is not able to gnaw or bite. In addition, the food must be sufficiently soaked or softened so that it can pass through the rather modest size mouth opening. Therefore, plant foods (grass, leaves) should not be freshly picked (or freshly cut), but already dried, with softened fibers. That’s why earthworms love to live and feed so much in half-rotted humus, under last year’s fallen leaves, in mowed or cut vegetation that has lain for quite a long time on the surface of the soil.

A goiter is a large thin-walled cavity in which swallowed (absorbed) food accumulates. But what happens to her next? And how can one manage without teeth? There is no need to doubt: the worm has teeth, but they are located in the stomach.

The stomach is a muscular, thick-walled chamber, the inner surface of which consists of hard, tooth-like projections. When the walls of the stomach contract, they crush (gnaw, chew, grind) food into small particles. And already in this state, food enters the intestines, where it is digested under the action of digestive enzymes, and the nutrients released are absorbed. By the way, the stomach of crocodiles and most birds is structured in a similar way.

The peculiarities of digestion make earthworms detritivorous, i.e. they feed on detritus - decaying plant organic matter found on the surface of the earth or in their underground burrows, as well as in the soil itself, in contact with the soil itself. the earthworm leaves behind are lumps of soil enriched with nitrogen, microelements, and having low acidity due to the alkaline environment of its intestines.

The earthworm has an “Achilles heel” (each of us has a weak spot...). The problem is that a worm requires energy to live. And he gets it through respiration (and oxygen oxidation), and this requires gas exchange between the body and the environment. The worm does not have a special organ for gas exchange (lungs, gills, etc.), so it breathes through the skin. To do this, it must be very thin and constantly moisturized.

The lack of a protective shell leads to the fact that the most common reason for their natural death is drying out.

The body of earthworms consists of many ring-shaped segments (from 80 to 300), which are easy to see.

If necessary, the body of the worm is covered with abundant mucus, which serves as an excellent lubricant for squeezing through the ground. This same mucus prevents the body from wasting water, of which there is a lot in the worm - about 80% of the total weight.

Under certain conditions, worms can restore missing body parts. For example, the back part will grow back if it is torn off in an accident. However, this does not always happen.

Worms , awakened from hibernation, enter the mating season and begin to lay cocoons (one cocoon approximately once a week) for 3 months. Juveniles reach sexual maturity in the fall, when hibernation time is already approaching; in winter, some young worms may die.

Earthworms are skilled and fast builders of passages and chambers in the soil.

Worm burrows in the soil can be one-time or permanent. Disposable ones are laid in loose soil, where it is easy to squeeze between lumps in any direction. Constant passages forming a system of burrows dig in both loose and dense soil. In the latter , the worm swallows the earth and passes it through itself.

Worm tunneling increases soil aeration, soil water infiltration, nitrogen availability to plants, and soil microbial activity. It has been established that by drilling the soil with worms, the number of nitrifying bacteria increases. The increased amount of nitrogen found in the drilosphere may be one of the reasons for the growth of roots in the channels made by worms . Earthworm tunnels can remain unchanged for decades, which helps to increase the density of plant roots, stabilize soil aggregates and reduce the likelihood of soil erosion. Moving tail first, it reaches the surface or cavity in the soil, where it deposits soil in the form of coprolites. Then he returns, swallows the next portion and everything repeats. Not all types of worms can master dense soil. Many always remain in the loose layer and do not tolerate its artificial compaction well. This must always be remembered when organizing the movement of machines across the field. Worm tunnels play a huge role in the life of plants, because they supply oxygen to the living soil.

For optimal root growth, the soil needs to contain 10-15% air. If the soil is compacted, the consequence will be a decrease in yield. In compacted layers after precipitation, as a rule, moisture accumulates, which leads to oxygen deficiency in the root zone. Oxygen is a necessary energy supplier for the absorption and transport of nutrients. If there is a lack of oxygen, problems arise with the absorption of potassium, calcium, magnesium, phosphorus and iron, and the transport of these ions into the plant becomes much more difficult.

An important role in this is played by the activity of earthworms , whose activity is manifested in the supply of a sufficient amount of organic biomass. In the course of their life, worms make passages through which the roots of cultivated plants can then grow. In this way, the deep growth of the root system and its branching are supported.

Worms need moist soil to live so that it does not suck the moisture out of them. For people who constantly work with soil, the skin on their hands dries and cracks. The worms are not in any better position. Although their body is protected by constantly secreted moisturizing mucus, in dry soil there is nowhere to get moisture for its formation. If there is not enough water, the worms go deeper into wetter layers of soil or fall asleep (enter diapause). They build chambers for this purpose and conveniently roll them up into pretzels or tie them in intricate knots, hiding their “noses” and tails inside the rings.

Chambers in the soil are built by worms both to wait out drought and for wintering. The chambers of shallow-living worms can be found at a depth of 20-30 cm, and those that dig deep holes can be found at a depth of 50-70 cm. They also occur at a depth of two meters. Worms often wait out drought and winter in twos or in groups.

The enemies of earthworms are birds that eat them, arthropods and their larvae, toads, frogs, newts, moles, hedgehogs, shrews, badgers, raccoon dogs, foxes, fish, wild boars.

How many years do earthworms ? Little is known about this. There is evidence that no more than 10 years. However, in nature, few worms manage to live for so long - their living conditions are very difficult. Sudden changes in temperature and soil moisture lead to mass death of these animals. Numerous enemies lie in wait everywhere: worms are a very nutritious food, and they have no defense weapons other than the ability to quickly hide in a hole.

However, enemy No. 1 for worms is an unreasonable person and his illiteracy in soil science.

The first blow is dealt by repeated deep, up to 35 cm, plowing and digging of the soil, turning over the layer and destroying all living things. But the conditions of arable land are especially difficult for worms . In hot weather, unshaded, plowed soil easily heats up and dries out, and the worms die. In the spring, tractors turn up the earth with worms for the birds to eat. In late autumn, the minks are opened, when the worms have already settled down for the winter.

But the man does not calm down, as if he is purposefully waging a war to destroy his assistant and friend.

On arable land, where people take the entire harvest, where the soil structure is destroyed by heavy machines, and nutrients in the form of crop residues are briquetted and burned in the fireplaces of “successful” people, worms are doomed to extinction.

People treat crops with chemical fertilizers and pesticides. This leads to massive death of earthworms and other soil fauna, without which arable land is dead. However, we must not forget: if you apply fertilizer to arable land where worms have been destroyed by humans, this will not give the desired effect. This can be observed by the reduction in the use of basic fertilizers by plants under arable technology compared to soil-saving technology. Thus, arable technology uses 28% nitrogen, 20% phosphorus and 32% potassium, and soil conservation technology uses 50, 20 and 50%, respectively. With arable technology, there is no one to turn fertilizer into soil. worms no longer live , consists of dense blocks, which, even after harrowing, are broken into pieces that are more reminiscent of shale than clods of earth. The soil inside them is dense, drained, without any signs of life. There are no passages or coprolites.

Such activities lead to the mass death of great workers.

In the old days, peasants judged the fertility of the soil by the number of red worms living on the plot. When cultivating the land, worms ; they knew where there were more of them, the harvest of vegetables, berries and fruits would be richer, and the products would be tastier. The work of underground plowmen - earthworms - is still highly valued by experienced farmers today.

Nowadays, after the boom in agricultural chemicalization, people are turning to agriculture based on attention to the inhabitants of the soil and their role in its creation. If nature intended for the worm to loosen, fertilize and treat the soil, then returning them to the fields will save the farmer from many problems.

It is clear that no-till technology is the way to return the earthworm to the field , and “aerobatics” for the agronomist is the transition to no-till technology, which will be discussed in the next section.

It is No-till that is the green light for the earthworm to return to the field, because under the mulch moisture is retained, which is so important for the skin of the “angels of the earth”, the soil is protected from overheating, weathering, and freezing. The lower, decomposing layer of mulch is a wonderful dining room for worms .

But switching to no-till is very difficult, and if, if necessary, the agronomist decides to loosen the soil, then the treatment should be no deeper than 5 cm! This will preserve the structure created by the worms , their passages and holes. And after a while you will be surprised at the depth to which your soil will become light and fluffy without any cultivation.

The experience of agronomists who switched to no-till ten or more years ago shows that the chemical load on the soil is significantly reduced. Saving plants with chemicals is the same as being treated with pills: it removes the symptoms, but does not eliminate the cause... Weakened plants grow in sick soil, susceptible to diseases and pests. It makes more sense to improve the soil, and worms will do this best of all, simultaneously enriching it with vermicompost. Well, if soil fertility does not decrease, but increases every year, then chemistry may be needed only in emergency cases.

Vermicompost.

One would like to say that “a real agronomist is one who has a good sense of humus.” It has been established that the application of 6 t/ha of vermicompost is equivalent in its effect on productivity to the application of peat manure compost in the amount of 60 t/ha!

Vermicompost is a product of the processing by earthworms . It is a loose, finely granulated mass with granule sizes of 1-3 mm.

Properties of vermicompost.

Since vermicompost contains a large amount (up to 32% by dry weight) of humic substances - humic acids, fulvic acids and humins - this gives the organic fertilizer high agrochemical and growth-stimulating properties. All nutrients are found in it in a balanced combination, worked out by nature itself, and in a form available to the plant. In terms of the content of basic plant nutrients, vermicompost surpasses all known organic fertilizers.

Worms increase the absorption of potassium, phosphorus, and microelements by plants. For example, the nitrogen released by worms is absorbed by plants by more than 95% , while nitrogen from fertilizers is only 30-40%.

Vermicompost is also a microbiological fertilizer; it contains a unique community of microorganisms that create soil fertility. It does not contain pathogenic microorganisms, helminth eggs, weed seeds and heavy metals. Moreover, it contains a unique community of microorganisms beneficial to the soil and plants, which, when vermicompost enters the soil, populate it, secrete phytohormones, antibiotics, fungicidal and bactericidal compounds, which leads to the displacement of pathogenic microflora. All this ultimately improves the health of the soil and eliminates many common plant diseases.

In addition, vermicompost has exceptional physical and chemical properties: water strength of the structure (95-97%) and complete moisture capacity (200-250%). This allows us to consider it as an excellent ameliorant and soil improver.

Vermicompost is especially effective in protected soil.

The effectiveness of vermicompost.

• vermicompost quickly restores the natural fertility of the soil, improves its structure and health;
• vermicompost does not have an inert action: plants and seeds immediately react to it;
• vermicompost is a long-acting organic fertilizer: its effectiveness remains for 4-7 years;
• vermicompost reduces the germination time of seeds and increases their germination rate, accelerates the growth and flowering of plants, and shortens the ripening time;
• vermicompost provides strong immunity to plants, increasing their resistance to stressful situations, adverse weather conditions, bacterial and putrefactive diseases;
• vermicompost binds heavy metals and radionuclides in the soil and prevents plants from accumulating nitrates;
• vermicompost provides a stable, high, environmentally friendly harvest.

In the soils of Ukraine, the humus varies in different zones, but the range of its content is from 0.8 to 6.5%. The thickness can range from 10-15 cm to 1 meter or more. The main source of humus is the aboveground part of plants and their roots, which are amenable to humification. The processes of humification are complex, their speed and nature depend on many soil and climatic conditions, the composition of vegetation, the microbial and animal world of the soil, as well as on economic activities.

Ukraine has a huge reserve of fertile soil. 60% of all lands are chernozems, this share of the world's areas is 6.7%. A hundred years ago, the black soils of Ukraine contained 4-6% humus , today – 3.2%. The formation of humus is a long process. An increase in its content in the soil by 1% occurs in 300-400 years. It turns out that in a hundred years we have lost the proportion of humus in the soil that had accumulated for more than 1000 years.

humus in the soil than 2.5%, then it is not black soil.

Table No. 1 shows for comparison the areas of chernozems in different countries and their share of the world area.

Table No. 1. Area of ​​black soils in different countries.

Moreover, the quality of the chernozems of the listed countries is inferior in the amount of humus to the chernozems of Ukraine.

Today, the annual decrease in the proportion of humus in the fields of Ukraine is 500-700 kg per hectare. The application of mineral fertilizers splits humus , and this leads to a decrease in its content in the soil. The most “aggressive” are nitrogen, some types of potassium and complex fertilizers.

Humus is also called the soil's immune system, since it maintains basic functions and ensures the health of the soil environment. Humus activates the natural defense of plants against diseases and pests. Harmful substances (pesticide residues, heavy metal salts, radionuclides, toxicants, etc.) decompose or are deactivated in colloids and do not pose a danger to soil fauna and plants. Humus plays an important ecological role for the entire living world (plants, animals and people). It absorbs and binds harmful substances like a sponge and therefore can be called a “buffer of the planet.”

Among the means that are aimed at ensuring a deficit-free balance of humus , stubble and root residues are important. Therefore, minimizing soil cultivation and growing green manure play a vital role in maintaining the level of humus , and in the future, increasing its proportion in the soil.

Humus is the plant’s bread; it accumulated in the soil (in our latitudes) throughout the post-glacial period. Stopping the decline in soil fertility, and, in the long term, its restoration lies through the return of the earthworm to the soil , which means abandoning the plow and a difficult but necessary path to direct sowing technology.

This is exactly what will be discussed in the next section.

The structure of the body

The breathing of a flatworm is carried out precisely through the surface of the body of the organism, therefore it is connected with the structure of the integument of the body. The outside of the body is covered with a single layer of epithelium. Ciliated worms (turbellarians) have an epithelium consisting of cells that bear cilia. Parasitic flatworms, flukes, as well as representatives of monogeneans, cestodes and tapeworms do not have ciliated epithelium during the main part of their lives. Ciliated cells can be found in larvae. The body integument of these three types is presented in the form of teguments, which bear microvilli or chitinous hooks. Tegument holders are called representatives of the Neodermata group. Flatworms are able to restore about 6/7 of their body components through regeneration.

Getting to know the muscles

The muscle tissue of flatworms is represented by a muscular sac, which lies under the epithelium. It consists of a number of layers of muscle-type cells that are not divided into muscles. However, some differentiation is observed in the areas of the pharynx and reproductive system. The outer part of the cells of the muscle layers are oriented transversely, and the inner ones are oriented along the posterior-anterior axis of the body. The outer muscles are called the annular layer, and the inner ones are called the longitudinal muscles layer.

Breathing methods

Now we will try to understand the question of how flatworms breathe? The detailed description of breathing processes is described only superficially. It is only important to know that flatworms breathe through the cavity of the entire body. It follows from this that they do not have special respiratory organs, characteristic of many animals. However, this applies to parasitic forms of worms and free-living species, and endoparasites living in an environment with a small amount of oxygen can respire anaerobically.

Respiration of aerobic flatworms is carried out by diffusion - the interpenetration of, for example, gases, with the aim of leveling them throughout the entire volume of the body. Anaerobic glycolysis of endoparasites is a self-sufficient process, which is characterized by the presence of three conditions: the arrival of glucose, the presence of ATP, in almost any quantity, and the restoration of the lost supply of NAD.

Features and habitat

The earthworm , also known as the ringed one, is a well-known resident of any garden plot. And it would seem an absolutely invisible creature that no one needs.

However, any person who is at least somehow connected with the land will be very happy to have such inhabitants of his garden. There are no more than a hundred species of earthworm in the Russian Federation. But all over the world there are one and a half thousand varieties of them.

It belongs to the family of annelids, the oligochaete class. Its entire long body consists of many rings. There may be seventy of them, or maybe all three hundred. Since it grows more than twenty-five centimeters in length.

But there are also the smallest ones, two or three centimeters. The Australian earthworms reach two and a half meters in size. Its color is literally gray-brown - crimson.

Also, on each ring, or it is also called a segment, there are bristles. Our ordinary garden worms, as a rule, grow eight bristles. They are classified as oligochaetes.

However, there are also tropical, polychaete species of worms in which the villi grow in dozens. The bristles help the worms crawl, absolutely over all soil tubercles or burrow into holes.

You can find them by holding the worm in your hands and running your finger from back to front. But since it is difficult for an inexperienced person to determine where his butt is, you can simply run your hand lightly along the body and back. You can feel it right away. In one direction the worm will be absolutely smooth, and in the opposite direction it will be rough.

Anyone who has ever picked up a worm knows that it is covered with not very pleasant mucus, which is vital for it. Firstly, mucus helps the invertebrate move freely in the ground. Secondly, since the worm does not have lungs, it breathes through the skin. And thanks to the moisture found on the mucus, the body is saturated with oxygen.

The body of the earthworm itself consists of two groups of muscle tissue. They are longitudinal and transverse. The transverse muscles are located under the protective top layer of the worm's skin.

With their help, the worm becomes as long as possible. And the stronger muscles are longitudinal. They cut and make the body smaller. This is how the animal moves, sometimes lengthening, sometimes shortening.

The earthworm belongs to the secondary cavity animals. Consequently, he has a complete closed circulatory system. Because their life activity is active.

The muscles contract many times more often than in protocavitary worms. To do this, they need blood to provide the worm with all the nutrients and oxygen.

In the structure of an earthworm there are a pair of blood vessels, one of them is called dorsal, the second is abdominal. Ring vessels connect them to each other. Blood flows through them from back to front, and vice versa.

Familiarization with the pharynx and intestines

All groups of flatworms are characterized by the presence of a pharynx, which leads to the intestine. The exceptions are cestodes and tapeworms. This intestine opens into the parenchyma intended for digestion, closes blindly and is connected with the outside world only by the mouth opening. Some large turbellarians have anal pores, however, this is an exception only for some subjects of the species. Small forms are characterized by a straight intestine, while large ones (planaria, fluke) may have a branched one. The pharynx is located on the surface of the abdomen and can often be found in the middle or closer to the back of the body. In some groups of worms the pharynx moves forward.

Character and lifestyle

Charles Darwin also suggested the presence of intelligence in earthworms. Watching them, he noticed that when dragging a dry leaf into his home, it was turned with the narrow side. This makes it easier for a leaf to pass through a dense, earthy burrow. But on the contrary, he takes spruce needles by the base so that they do not fork.

The whole day, the whole life of an earthworm, is scheduled minute by minute. Every now and then he climbs in the ground, makes moves, swallowing it. The worm digs holes in two ways. He or, as already mentioned, swallows the earth, gradually moving forward.

In case the ground is too hard. And then leaving behind their biological waste. Or, he pushes it with his delicate end in different directions, and makes moves for himself. The passages are obliquely vertical.

The same earthworm , hunting in the soil , drags into its holes, for insulation, various leaves, veins from leaves, thin pieces of paper and even scraps of wool. Its burrows are up to one meter deep. And the worms are larger in size, and all ten meters. The worm works mainly at night.

Why do earthworms crawl to the surface in huge numbers? This means he can't breathe. This usually happens after heavy rains. The earth is clogged with moisture, and there is no oxygen for him at all. When cold weather arrives, the earthworm goes deep into the soil.

Features of the nervous system and sensory organs

Characterizing the nervous system of flat protostomes, it is worth noting that they are characterized by the presence of nerve ganglia located in front of the body, and also have ganglia of the brain and nerve columns branching off from them, which are connected by jumpers. Sensitive organs include individual skin cilia, which are processes of nerve-type cells. There are free-living species that have special, light-sensitive eyes of a pigmented nature. Such organs serve as a primitive adaptation to the sense of balance and allow vision, albeit primitively.

Extraction system

Flatworms have an excretory system that takes the form of protonephridia. With their help, the process of osmoregulation and metabolism occurs. The selection system takes the form of channels that branch and combine into 1-2 channels. Initially, these are stellate-type cells, which, branching into tubules, open a lumen for the passage of a bundle of flagella. Merging, the tubules form a larger structure and are brought out in the form of excretory pores to the surface of the body. Such excretory systems are called protonephridial. Metabolic products that are dangerous to the life of the worm are excreted along with fluids through the above-mentioned protonephridia, as well as with the help of special parenchyma cells - atrocytes, which play the role of “storage buds”.

Hermaphrodite is not a dirty word

All adult earthworms simultaneously carry the characteristics of the sex cells and glands of the male and female. The scientific name of such an animal is hermaphrodite . Representatives of such species can reproduce if there are only two living organisms. It doesn't matter to them what gender these organisms are. Thanks to this property, this species is distributed everywhere and is very numerous, moreover, it has many related species.

Reproduction of earthworms occurs in several stages. First, individuals exchange seminal fluid, which will be stored for a certain number of days for each species in mucus secreted by special cells of the girdle. When the sperm mature, the same girdle again secretes mucus, which forms a cocoon. The worm removes it from itself through the head, and during the movement, eggs enter the cocoon from the genital segments. And only now their fertilization . The removed cocoon, filled with viable eggs, is stored in the ground, where it develops new earthworms. When the right time comes, small but already fully formed worms emerge from such a capsule.

Reproduction

Among flatworms, hermaphrodites predominate; only some species are dioecious, for example, schistosomatidae. The reproductive system, both male and female, can differ greatly between species in terms of the shape of the structure of the testes and ovary. The same applies to the rest of the components of the reproductive system. Certain groups of ciliated worms and all representatives of parasites have an ovary divided into 2 parts:

1. Germarium is the ovary itself. Produces eggs that are poor in yolk but capable of development.
2. Vitellaria - sometimes called vitellaria, it produces abortive type eggs, they are rich in yolk.

These composite reproductive systems form complex, or exolecithal, eggs. The common membrane may contain one egg or a number of yolk spherules secreted by accessory glands.