What kind of skin does an earthworm have. Earthworm

In the world of fauna is the earthworm. He can rightly be called an earthworker, because it is thanks to him that the soil on which we walk is fully saturated with oxygen and other minerals. Passing various parts of the earth up and down, this worm makes them loose, which then allows planting cultivated plants there, as well as gardening.

General characteristics of the species

The earthworm belongs to the kingdom Animals, to the sub-kingdom Multicellular. Its type is characterized as ringed, and the class is called Small-bristle. The organization of annelids is very high compared to other types. They possess a secondary body cavity which has its own digestive, circulatory and nervous systems. They are separated by a dense layer of mesoderm cells, which serve as a kind of airbags for the animal. Also, thanks to them, each individual segment of the worm's body can autonomously exist and progress in development. The habitats of these earthly orderlies are moist soil, salty or fresh waters.

The external structure of the earthworm

The body of the worm is round. The length of representatives of this species can be up to 30 centimeters, which can include from 100 to 180 segments. The front part of the body of the worm has a slight thickening, in which the so-called genitals are concentrated. Local cells are activated during the breeding season and perform the function of laying eggs. The lateral outer parts of the body of the worm are equipped with short setae, completely invisible to the human eye. They allow the animal to move in space and touch the ground. It is also worth noting that the tummy earthworm painted always in more light tone than its back, which is maroon, almost brown.

What is it like from the inside

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

Digestive system

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

circulatory system

The circulatory system that the earthworm possesses can be divided into three segments: the abdominal vessel, the dorsal vessel and the annular vessel, which combines the two previous ones. The blood flow in the body is closed, or annular. The annular vessel, which has the shape of a spiral, combines two arteries vital for the worm in each segment. It also branches off capillaries that come close to the outer surface of the body. The walls of the entire annular vessel and its capillaries pulsate and contract, due to which the blood is distilled from the abdominal artery to the spinal one. It is noteworthy that earthworms like humans have red blood. This is due to the presence of hemoglobin, which is regularly distributed throughout the body.

Breathing and nervous system

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

reproduction

We note right away that all earthworms are hermaphrodites, and in each organism the testes are located in front of the ovaries. These seals are located in the front of the body, and during the mating period (and they have a cross), the testes of one of the worms pass into the ovaries of the other. During the mating period, the worm secretes mucus, which is necessary for the formation of a cocoon, as well as a protein substance that the embryo will feed on. As a result of these processes, a mucous membrane is formed in which the embryos develop. After they leave her rear end forward and crawl into the ground to continue their race.

It has a more complex organization than roundworms or flatworms.

In worms of the annelids species, for the first time, a secondary cavity, a highly organized blood supply system and a nervous system appear.

Earthworm: structure

In cross section, the body is almost round. The average length is about 30 cm. It is divided into 150-180 segments, or segments. The belt, located in the anterior third of the body, performs its function during sexual activity (the earthworm is a hermaphrodite). On the sides of the segments there are four stiff, well-developed small setae. They contribute to the movement of the body of the worm in the soil.

The color of the calf is reddish-brown, and on the abdomen is slightly lighter than on the back.

natural necessity

All animals have a circulatory system, starting with the secondary cavities. It was formed as a result of an increase in vital activity (compared, for example, with Life in constant motion requires stable energetic muscle work, which, in turn, causes the need for an increase in cells of incoming oxygen and nutrients, that only blood can deliver.

What is the circulatory system of an earthworm? The two main arteries are the dorsal and abdominal cavity. In each segment, looped vessels pass between the arteries. Of these, several are slightly thickened and covered with muscle tissue. In these vessels, which perform the work of the heart, the muscles, contracting, push the blood into the abdominal artery. The annular "hearts" at the exit to the spinal artery have special valves that prevent blood flow from going in the wrong direction. All vessels are divided into a large network of the thinnest capillaries. Oxygen in them comes from the air, and is absorbed from the intestines. nutrients. Capillaries located in muscle tissues give off carbon dioxide and decay products.

The circulatory system of the earthworm is closed, since it does not mix with the liquid of the cavity during the entire movement. This makes it possible to significantly increase the rate of metabolism. In animals that do not have a blood pumping system, heat transfer is two times lower.

Nutrients absorbed by the intestines during the movement of the worm are distributed through a well-formed circulatory system.

Its scheme is quite complicated for this type of animal. Vessels run above and below the intestines along the entire body. The vessel passing in the back is supplied with muscles. It, contracting and stretching, pushes the blood in waves from the back to the front of the body. In the anterior segments (in certain types worms are 7-11, in others - 7-13) the vessel running along the back communicates with several pairs of vessels passing transversely to the main one (usually there are 5-7 of them). The circulatory system of the earthworm imitates hearts with these vessels. Their muscles are much more developed than the others, so they are the main ones in the entire system.

Functional features

An earthworm is similar to the hemodynamic functions of vertebrates. The blood that comes out of the hearts enters the vessel located in the abdominal cavity. It moves towards the posterior end of the body of the worm. On its way, this blood carries nutrients through smaller vessels located in the walls of the body. During puberty, blood also enters the genitals.

The structure of the circulatory system of the earthworm is such that the vessels in each organ pass into the smallest capillaries. The blood from them flows into the vessels located across the main ones, from which the blood flows into the spinal artery. Musculature is in all blood vessels, even the smallest. This allows the blood to not stagnate, especially in the peripheral part of the blood supply system of this type of annelids.

Intestines

In this part of the body of the worm there is a particularly dense plexus of capillaries. They seem to entangle the intestines. Part of the capillaries brings nutrients, the other part carries them throughout the body. The muscles of the vessels surrounding the intestines of this annular species are not as strong as those of the dorsal vessel or the heart.

Composition of the blood

The circulatory system of the earthworm is red in the light. This is due to the fact that in the blood there are substances that are similar in their chemical structure to hemoglobin, which is part of the blood composition of vertebrates. The difference lies in the fact that these substances are in the plasma (the liquid part of the blood composition) in a dissolved form, and not in the blood cells. The blood of the earthworm itself is cells without color, of several types. They are similar in structure to the colorless cells that make up the blood of vertebrates.

Transportation of oxygen cells

Oxygen cells in vertebrates transport hemoglobin from the respiratory organs. In the blood of earthworms, a substance similar in composition also brings oxygen to all the cells of the body. The only difference is that worms do not have respiratory organs. They "inhale" and "exhale" the surface of the body.

The thin protective film (cuticle) and epithelium of the skin of the worm, together with a large capillary network of the skin, guarantee a good absorption of oxygen from the air. The capillary cobweb is so large that it is even in the epithelium. From here, the blood moves through the wall vessels of the body and transverse vessels to the main stem channels, due to which the whole body is enriched with oxygen. The reddish tint of the body of this type of annelids is given precisely by a large capillary network of walls.

Here it must be taken into account that the thinnest film covering the body of the earthworm (cuticle) is very easily moistened. Therefore, oxygen is first dissolved in water droplets, which are retained by the skin epithelium. From this it follows that the skin should always be moisturized. Thus, it becomes clear that the humidity environment- one of important conditions for the life of these animals.

Even the slightest drying of the skin stops breathing. For the circulatory system of the earthworm does not bring oxygen cells. It can not last very long in such conditions, using internal water supplies. The glands located in the skin help out. When the situation becomes really acute, the earthworm begins to utilize the cavity fluid, splashing it out in parts from the pores located on the back.

Digestive and nervous systems

The digestive system of earthworms consists of the foregut, midgut and hindgut. Due to the need to live more actively, earthworms have gone through several stages of improvement. The digestive apparatus has departments, each of which has a specific function.

The main organ of this system is the intestinal tube. It is divided into the oral cavity, pharynx, esophagus, stomach (muscular body), middle and hind intestines, anus.

The ducts of the glands go into the esophagus and pharynx, which affect the pushing of food. In the midgut, food is chemically processed and the products of digestion are absorbed into the blood. The rest comes out through the anus.

Along the entire length of the body of the worm, from the side of the peritoneum, there is a nerve chain. Thus, each segment has its own developed nerve lumps. In front of the neural chain is an annular jumper, consisting of two connected nodes. It is called the peripharyngeal nerve ring. A network of nerve endings radiates from it throughout the body.

The digestive, circulatory and nervous systems of the earthworm are much more complicated, due to the progress of the entire type of annulus. Therefore, in comparison with other types of worms, they have a very high organization.

The rain church has an elongated, 10-16 cm long body. In cross section, the body is rounded, but, unlike roundworms, it is divided into 100-180 segments by annular constrictions. Each segment has small elastic setae. They are almost invisible, but if you run your fingers from the back end of the worm's body to the front, then we will immediately feel them. With these bristles, the worm clings to the unevenness of the soil when moving.

Figure: earthworm and the movement of the worm in the soil

Earthworm habitat

During the day, the worms stay in the soil, making passages in it. If the soil is soft, then the worm bores it with the front end of the body. In doing so, he first compresses the front end of the body, so that it becomes thin, and pushes it forward between the lumps of soil. Then the front end thickens, pushing the soil apart, and the worm pulls up the back of the body. In dense soil, the worm can eat its own way, passing the earth through the intestines. Heaps of earth can be seen on the surface of the soil - they are left here by worms at night. They also come to the surface after heavy rain(hence the name - rain). In summer, the worms stay in the surface layers of the soil, and for the winter they dig minks up to 2 m deep.

Skin-muscular sac

If we take the worm in our hands, we will find that its skin is moist, covered with mucus. This mucus facilitates the movement of the worm in the soil. In addition, only through wet skin there is a penetration into the body of the worm of oxygen necessary for respiration.
Under the skin are located circular muscles fused with it, and under them a layer of longitudinal muscles - a skin-muscular sac is obtained. The circular muscles make the body of the worm thin and long, while the longitudinal muscles shorten and thicken. Thanks to the alternating work of these muscles, the movement of the worm occurs.

The body cavity of an earthworm

Picture: internal structure earthworm

Under the skin-muscle sac is a fluid-filled body cavity in which the internal organs are located. This body cavity is not continuous, as in roundworms, but is divided by transverse septa according to the number of segments. It has its own walls and is located under the skin-muscle sac.

Earthworm digestive organs

Picture: digestive system earthworm

The mouth is located at the anterior end of the body. The earthworm feeds on decaying plant remains, which he swallows along with the earth. It can also drag fallen leaves from the surface. Swallowing is done with a muscular pharynx. The food then enters the intestines. Undigested residues, together with the earth, are ejected through the anus at the posterior end of the body.

Figure: earthworm circulatory system

The circulatory system of the earthworm serves to carry oxygen and nutrients primarily to the muscles. An earthworm has two main blood vessels: dorsal blood vessel through which blood moves from back to front, and abdominal blood vessel through which blood flows from front to back. Both vessels in each segment are connected to annular vessels. Several thick annular vessels have muscular walls, due to the contraction of which blood moves. Thinner ones depart from the main vessels, then branching into the smallest capillaries. Oxygen from the skin and nutrients from the intestines enter these capillaries, and these substances are released from other similar capillaries branching in the muscles. Thus, the blood moves all the time through the vessels and does not mix with the cavity fluid. Such circulatory system called a closed circulatory system.

Excretory system of the earthworm

Liquid waste, processed substances enter the body cavity. Each segment contains a pair of tubules. Each tube has a funnel at the inner end, processed unnecessary substances enter it and are removed through the tube through the opposite end to the outside.

Figure: The nervous system of an earthworm

A pair of nerve trunks runs along the entire body of the worm along the ventral side. In each segment they have developed nerve knots- it turns out nerve chain. In the front part, two large nodes are connected to each other by ring bridges - a parapharyngeal nerve ring. From all nodes, nerves depart to various organs.

Sense organs of the earthworm

There are no special sense organs, but sensitive cells in the skin allow the earthworm to feel touch on its skin and distinguish light from darkness.

Reproductive system and reproduction of the earthworm

earthworms- hermaphrodites. Before laying eggs, two worms touch for a while and exchange seminal fluid - sperm. Then they diverge, and mucus is released from the thickening (girdle) on the front of the worm. Eggs enter this mucus. Then a lump of mucus with eggs slides off the body of the worm and freezes in cocoon. Young worms emerge from the cocoon.

26.01.2018

Dear colleagues! Today we will continue the topic "earthworms", in which we will consider the structure of an earthworm. Who knows, maybe among those reading these lines there are those who consider earthworms to be harmful such as: "they gnaw roots in pots, eat seedlings, sprouts, seeds ...", etc. Therefore, a variety of methods are invented to destroy worms, the most harmless of which - freezing of the soil. And they talk all sorts of nonsense about earthworms. I myself talked with such people, convincing them of the opposite, namely, of the invaluable help and benefit these tireless workers bring.

So, let's start studying the earthworm in order to figure out how its vital activity is supported.

To absorb food, worms have an organ called pharynx. It works on the principle of a rubber pear: when compressed and then unclenched, a vacuum is created, due to which food is drawn inward. It is clear that there are no teeth in the mouth, therefore, the worm is not able to gnaw or bite something.

In order to pass through a rather small mouth opening, the food must be sufficiently soaked or softened. Therefore, plant foods (shoots, leaves) should not be freshly picked (or freshly bitten), but already dried, with softened fibers. Therefore, earthworms so love to live and feed in half-rotted humus, under last year's fallen leaves, in mowed or cut vegetation that has lain on the surface of the soil for a long time.

Goiter- This is a large thin-walled cavity in which swallowed food accumulates. What happens next? How to be without teeth? It turns out that the worm also has them, only they are located ... in the stomach!

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

Features of digestion make earthworms detritivorous, that is, they feed on detritus- decaying plant organic matter located on the surface of the earth or in their underground burrows, as well as in the soil itself, biting into the soil itself. Therefore, the coprolites that the earthworm leaves behind are lumps of soil enriched with nitrogen, microelements, and having low acidity due to the alkaline environment of his intestines.

Upon careful examination of the picture, you will see that the worm has a brain, and nerves, and a heart (which is not even one, but five!). That is, the earthworm feels and understands everything, but it cannot say. Here is another tragic secret, still not understood by biologists and not revealed by forensic scientists: why do they crawl out onto the footpaths after the rain, and die en masse there?

The earthworm has its own "Achilles heel", its own weakness. the thing is that worms need energy for normal life. And they get it due to respiration (and oxygen oxidation), and it requires gas exchange between the body and the environment.

The structure of the earthworm is such that the worm does not have a special organ for gas exchange (such as lungs or gills), so it breathes skin. To do this, it must be thin and constantly moisturized. Because worms lack any protective shell, then the most common cause of their death is drying.

The body of earthworms consists of many annular segments (from 80 to 300) that can be easily seen. A worm can be both slippery and rough at the same time. He rests bristles- they are on each ring and are visible in an ordinary magnifying glass.

The bristles are the main support in the life of the worm, they are very convenient to grab hold of the tiny unevenness of the soil, which is why it is so difficult to pull the worm out of the mink - it will rather let itself be torn in half. Thanks to the bristles, inactive on the surface, it deftly eludes danger.

If necessary, the body of the worm is covered with abundant mucus, which serves as an excellent lubricant for squeezing through the ground. The same mucus does not allow the body to waste water, which in the worm is as much as 80% of the total weight.

Under certain conditions, worms can restore missing parts of the body. For example, the back will grow back if it is torn off in an accident. But this does not always happen. So let's take care of our underground architects, "angels of the earth", and create favorable conditions for them. And they, in turn, will thank us with improved soil on the plots and a generous harvest.

Since ancient times, mankind has drawn Special attention on such unsightly creatures as the earthworm. And scientific minds, in the person of Charles Darwin, decades later, for many years studied their structure and significance in agriculture. And for good reason. Indeed, with the onset of spring warmth, earthworms begin painstaking work and work, without knowing it, for the benefit of people.

Features and habitat

Earthworm , he is ringed - a well-known resident on any personal plot. And it would seem, absolutely imperceptible, useless creation.

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

It belongs to the family of annelid worms, low-bristle class. Its entire long body consists of many rings. There may be seventy, or there may be three hundred. Since in length it grows more than twenty-five centimeters.

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

Also, on each ring, or it is also called a segment, there are bristles. In our ordinary garden worms, as a rule, eight bristles grow. They are classified as low-bristle.

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

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

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

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

With their help, the worm becomes as long as possible. And the stronger muscles are longitudinal. They shorten, reduce the body. So, sometimes lengthening, sometimes shortening, the animal moves.

The earthworm belongs to the secondary cavity animals. Therefore, it has a complete closed circulatory system. Because they are active.

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

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

In each ring, or as it is also called, a segment, there is a pair of tubules. The funnels at their ends open and feces are discharged through the bottom. earthworm. This is how the excretory system works.

As for nervous system, it is nodal. Its components are the ventral nerve chain and the peripharyngeal nerve ring. These endings consist of fibers, and those, in turn, respond to the urges of the contracted muscles of the worm. Thanks to them, the worm can eat, purposefully move, multiply, and develop.

In the building earthworm organs, there are no those responsible for smell, touch, sight, sensation. But there are certain cells, they are located along the entire body of the invertebrate. With their help, the worm navigates in the dark and impenetrable land.

Character and lifestyle

Even Charles Darwin suggested that earthworms have intelligence. Watching them, he noticed that when he dragged a dry leaf into his dwelling, it was turned with its narrow side. This facilitates the passage of the leaf through a dense, earthy hole. But spruce needles, on the contrary, take it as a base so that they do not bifurcate.

All day, all rain life worm scheduled by the minute. He now and then 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.

If the ground is too hard. And then leaving their biological waste. Or, pushes it with its refined end, in different sides, and makes moves. The passages are obliquely vertical.

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

BUT why earthworms come to the surface in great numbers. This means he can't breathe. This usually happens after heavy rains. The earth is clogged with moisture, and there is no oxygen at all. Upon the arrival of cold earthworm goes deep into the soil.

Earthworm food

The food of the worm is quite typical. Swallowing large quantities of earth along with food. For food, they are suitable for wilted and slightly rotten leaves, mushrooms. But it should not have an unpleasant odor, otherwise the worm will not eat it.

It turns out that earthworms even build whole pantries for themselves, and put food there for the winter. They eat it only in case of critical need. For example, in winter time when the ground is completely frozen, and there can be no talk of any terrestrial food.

Having sucked food together with a lump of earth, through the pharynx, with muscular movements, then expanding his body, then narrowing, he pushes it to the back of the esophagus into the goiter. After, it enters the stomach. From the stomach it is sent to be overetched in the intestines, thanks to enzymes, it comes out with the most useful biomass.

Making moves, and at the same time snacking, rainy worm need crawl out periodically to the surface to throw off the ground. At the same time, he adheres to the hole with his edge of the tail, as if holding on to it.

And after, there are always earthen slides. The soil processed by the worm turns out to be sticky. Notice it dries up, and becomes small, with a match head balls.

These balls are saturated with vitamins, enzymes, organic substances, which, as a result, kill all bacteria in the ground, prevent decay, which is very important for plant roots. And they also act on the composition of the earth as an antiseptic, disinfecting it.

Reproduction and lifespan

Earthworms can be of different sexes, and hermaphrodites. All earthworms have thickenings on the front third of their body. They contain the ovary and testis. Hermaphrodites let the seed into each other. Already mature testicles, within ten pieces, are inseminated. And crawl away in different directions.

When a female is ready for reproduction, she approaches her partner and copulates. Something like a cocoon is formed on it, consisting of several dozen thickened segments.

It is separated by a kind of belt. This cocoon receives all the nutrients necessary for the brood. After fertilization, the worm removes this burden from itself, it simply slides off the animal.

The edges on the cocoon, on both sides, are quickly pulled together so that future offspring do not dry out before they are born. Then, for four weeks, small worms mature and hatch.

Once born, they spread in all directions. And already from the first days of their lives, they begin active work, processing the land. And already at the age of three months, grown children reach the size of adults.

Another fact about earthworms is the ability to regenerate. If someone or something divides it into two halves. Over time, each of the halves will become a full-fledged individual. This is one of the ways of reproduction, but not sexually.

The role of the earthworm very important in agriculture. Firstly, they saturate the soil with oxygen, which is so necessary for everything growing on it. With their moves, they help the roots to fully develop.

Moisture is evenly distributed, and the soil is well ventilated, loosened. Due to the constant movement of the earth, with the help of worms, stones are extracted from it.

Also, with their recycled sticky residues, they stick the soil together, preventing it from eroding. Well, of course, they fertilize the earth when they drag leaves, insect larvae into it. It all rots and serves as excellent, natural bio-additives.