What do earthworms breathe? How an earthworm breathes. Internal structure of an earthworm
In annelids, which include earthworms, there are no special organs responsible for breathing. Gas exchange occurs in them through diffusion throughout the body, that is, they “breathe through their skin.”
Instructions
Worms do not need respiratory organs because ring structure and the cylindrical shape provides an optimal ratio of volume and surface area involved in oxygen production. Considering that the worms move quite little, we can say that such breathing through the skin is quite enough for them.
However, worms have a circulatory system, unlike single-celled organisms and some types of insects, in the blood earthworm hemoglobin is dissolved, which is carried throughout the body by contraction of large vessels during the movement of the worm. This distributes oxygen throughout the body, helping to maintain diffusion. Large vessels are one vein and one artery, which is exactly how many vessels the worm has (except for the capillaries located under the cuticle).
In principle, the earthworm does not have skin as such, like mammals, but has a very thin covering - the cuticle. Such skin is moistened by epithelial secretions, and due to its minimal thickness allows the worm to breathe. However, such skin is not protected from drying out, so the worms must live in some kind of moist environment in order to protect the skin from drying out. Oxygen is first dissolved in the water that covers the body of the worm, and only then is absorbed into the blood through the capillaries. If the worm's skin dries out, it cannot receive environment oxygen dies.
Since the earthworm practically does not come to the surface, such a respiration system turns out to be extremely beneficial for it - it can take oxygen directly from the soil for gas exchange. There is enough oxygen between the earth particles to supply the worm. When it rains, worms crawl out of the ground to the surface, this is due to the fact that water glues the particles of the earth together, and there is no air between them. To get the oxygen they need, the worms must rise to the surface.
To test the breath of an earthworm, you can conduct a simple experiment: pour earth into a jar and place several worms on top. Through a short time The worms will burrow into the ground, but if you pour water on the ground, they will rise to the surface. All annelids breathe in a similar way - using the skin, over the entire surface of the body.
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The earthworm (lat. Lumbricidae) belongs to the class of invertebrate animals and the suborder of earthworms (Haplotaxida). Its body consists of ring-shaped segments, the number of which can reach 320! These animals are widespread in all…
And the suborder of earthworms (Haplotaxida). Its body consists of ring-shaped segments, the number of which can reach 320! These animals are widespread in all corners of our planet. They are only absent in Antarctica. Very often children are interested in how earthworms move. In our article we will examine this issue in detail, and at the same time learn about them. appearance, lifestyle and method of reproduction.
Lifestyle of earthworms
If you walk through the garden in the morning or after rain, then, as a rule, you can see small piles of soil thrown out by worms on the ground, and in the puddles you can see them themselves. Due to the fact that these individuals crawl to the surface of the earth after rain, this name was assigned to them. (the photo above shows this invertebrate animal) also crawls onto the earth's surface at night. As a rule, it prefers soil rich in humus, so it is rarely found in sandstones. The earthworm does not like swampy soils. These features are explained physiological characteristics Lumbricidae. The fact is that worms breathe over the entire surface of their body, which is covered with a mucous epidermis. There is too little air dissolved in soil saturated with moisture. As a result, the earthworm suffocates there. By the way, this explains his behavior during the rain. Dry soil is also detrimental to representatives of Haplotaxida: their skin dries out and breathing stops. In wet and warm weather earthworms (the photo below shows Lumbricidae in all its glory) stay closer to the surface of the earth. With a decrease in temperature, as well as with the onset of a dry period, they crawl into the deeper layers of the soil.
earthworms
Adults reach 30 centimeters in length, although there are some larger specimens. The body of an earthworm is slippery, smooth, has a cylindrical shape, and consists of segments - piece rings. This constitution is explained by the way of life of Lumbricidae: such a structure facilitates the process of movement in the soil. The number of piecework rings reaches two hundred. The surface of the body, which could conventionally be called the back, is convex, the abdominal surface is flat and lighter. On the earthworm's body, where its front part ends, there is a thickening called the girdle. It contains special glands that secrete a sticky liquid. During reproduction, an egg cocoon is formed from the girdle, and eggs develop in it.
How do earthworms move?
Representatives of Haplotaxida crawl. First, they extend the front end of their body and cling to irregularities with special bristles, which are located on the ventral side of the rings. earth's surface. After this, the muscles contract, and the back one is pulled forward. The movement of a worm in the ground is characterized by the fact that it makes passages in the soil. At the same time, with the pointed end of its body, it pushes the earth apart, and then squeezes between its particles. It is also interesting how earthworms move in denser layers. As they move, they swallow soil and pass it through their intestines. Worms, as a rule, swallow soil at a considerable depth, and throw it out through the anus already at the top, near their own burrow. It can often be observed in the summer on the surface of the earth in the form of lumps and elongated “laces”.
Earthworm and its biology
Worms have well-developed muscles, which make this method of movement possible. Their muscles are located under the epidermis; in fact, they, together with the skin, form a kind of musculocutaneous sac. The muscles are located in two layers. Directly below the epidermis are the circular muscles, and below them is a second, thicker longitudinal layer (consisting of long contractile fibers). When the longitudinal muscles are compressed, the earthworm's body becomes thicker and shorter. When contracting the circular muscles, on the contrary, it is long and thin. The alternate contraction of both layers of muscles, carried out under the influence of the nervous system branching in the muscle tissue, determines the movement of Lumbricidae.
The movement of worms is greatly facilitated by the presence of small bristles on the lower part of the body. They can be felt if you run a wet finger along the abdomen of the worm from the rear to the anterior end. Thanks to these bristles, earthworms not only move in the soil, but also “grab” the ground when they are tried to be pulled out. They also help to rise and fall along already made earthen passages. With this we will finish dealing with the question of how earthworms move, and move on to no less interesting facts about the life of Lumbricidae.
Circulatory system
It consists of two longitudinal vessels - abdominal and dorsal, as well as branches connecting them. Due to muscle contraction of the walls, blood moves throughout the body. The blood of earthworms is scarlet. With its help, communication is established between internal organs, and metabolism is also carried out. As the blood circulates, it carries nutritional compounds from the digestive organs, as well as oxygen coming from the skin. At the same time, carbon dioxide is removed from the tissues. In addition, the blood removes unnecessary and harmful compounds to the excretory organs.
Feeding earthworms
The basis of nutrition for representatives of Haplotaxida consists of half-rotten plant remains. As a rule, at night, earthworms drag leaves, stems, etc. into their burrows. In addition, they can pass humus-rich soil through their intestines.
Irritation of earthworms
Earthworms do not have any special features. They perceive external irritations thanks to the nervous system. Worms have a highly developed sense of touch. The nerve cells responsible for this are located over the entire surface of the skin. The sensitivity of earthworms is so great that the slightest vibrations in the soil force them to hide in burrows or in deeper layers of the earth as quickly as possible. However, the importance of sensitive nerve endings is not limited only to the function of touch. Scientists have found that with the help of these cells, earthworms are able to sense rays of light. So, if a flashlight beam is directed at a worm at night, then it will high speed will hide in a safe place.
The response of animals to any irritation, carried out thanks to the nervous system, is called a reflex. It is customary to distinguish between different types of reflexes. So, body contraction earthworm from touching it, as well as its movement in sudden lighting is a protective function. This is a protective reflex. Experiments by scientists have shown that earthworms can smell. They use their sense of smell to find food.
Reproduction
Earthworms reproduce sexually, although in general protostomes are hermaphrodites. Each member of Haplotaxida has male organs, which are called testes (sperm develop in them), as well as female organs, called ovaries (they produce eggs). The earthworm lays its eggs in a slimy cocoon. It is formed from a substance that is released through the belt. Next, the cocoon in the form of a muff slides off the body and is pulled together at the ends. It remains in the ground until the young worms emerge from it. The cocoon serves to protect eggs from dampness and other unfavorable influences.
What are worms for?
This section will be useful for those who think that earthworms are only needed for fishing. Of course, a fisherman has nothing to do on the river without them, but this is not all the benefit from representatives of Lumbricidae. The role of the earthworm in nature is so great that it cannot be overestimated. They promote the decomposition of organic matter in the soil. In addition, earthworms enrich the earth with the most valuable fertilizer - humus. They are also a kind of indicator: if the soil contains a lot of worms, it means it is fertile.
A full understanding of the role of Haplotaxida came to humanity relatively recently. However, even now many farmers prefer to use chemical fertilizers, despite the fact that they kill all living things. Today, an alternative to chemicals has been found - vermicompost and vermicompost. Essentially this is Magic wand for the earth, because they contain a large number of phosphorus, potassium, nitrogen, that is, precisely those substances that are vital for plants for their full growth.
Conclusion
Earthworms are an important link in soil formation. Let's look at the process. In autumn, leaves fall from the trees and cover the entire surface of the earth. Immediately after this, they get down to business and decompose the leaves to the compost stage. And then the baton is picked up by worms, which process the foliage to the vermicompost stage. This way, the most valuable fertilizers get into the soil.
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. Specialized bodies in essence, they do not need them, 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, in annelids available 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.
Thin skin of an 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.
A. Tracheal system in locusts. B. The structure of the insect trachea.Respiratory system of insects - locusts.
Gas exchange in insects carried out through a system of tubes, the so-called trachea. This system allows oxygen to flow from the air directly to the tissues and there is no need for its transportation by blood. It's much more quick way, rather than the diffusion of dissolved oxygen through tissue; Such gas exchange creates conditions for high metabolic rate.
Spiracles- paired openings located on the second and third thoracic and on the first eight abdominal segments of the insect’s body lead to air cavities. Branched tubes - tracheas - extend from these cavities. Each trachea is lined by an epithelium that secretes a thin layer of chitinous material. Typically, this tough layer is further reinforced by spiral and annular thickenings, due to which the airways remain open even if the pressure in the lumen of the trachea is negative (compare with the cartilaginous rings in the human trachea and bronchi). In each body segment, the trachea branches into numerous smaller tubes called tracheoles; tracheoles also branch, penetrating the tissues of the insect, and in the most active tissues, for example in the flight muscles, they end blindly inside individual cells. The degree of branching of tracheoles can vary depending on the metabolic needs of the tissues.
Tracheoles have chitinous lining absent. At rest they are filled with watery fluid; at this time, oxygen diffuses through them to the tissues (and CO 2 - into reverse direction) at a speed quite sufficient to satisfy the needs of the insect. IN active state increased metabolic activity of muscles leads to the accumulation of certain metabolites, in particular lactic acid, and the osmotic pressure in the tissues increases accordingly. When this happens, the fluid from the tracheoles, under the influence of osmotic forces, is partially absorbed into the tissues, and more air enters the tracheoles, and therefore more oxygen, and this oxygen is supplied directly to the tissues just when they need it.
Conditions created in insect tissues at rest and in an active state (work of tracheoles).
The overall air flow passing through the insect's body is regulated by a mechanism closing the spiracles. The opening of each spiracle is equipped with a system of valves controlled by very small muscles. The edges of this opening are covered with hairs, which prevent foreign particles from entering the spiracles and prevent excessive loss of moisture. The size of the hole is adjusted depending on the amount of CO 2 in the insect’s body.
Increased activity leads to increased formation of CO 2. Chemoreceptors they catch this and the spiracles open. The same stimulus can also cause ventilation movements of the body, especially in large insects, such as locusts. The dorsoventral muscles, contracting, make the insect's body flatter, as a result of which the volume of the tracheal system decreases and air is pushed out of it (“exhalation”). Air absorption (“inhalation”) occurs passively when the body segments, due to their elasticity, return to their original shape.
Judging by some data, thoracic and abdominal spiracles open and close alternately, and this, combined with the ventilation movements of the body, creates a unidirectional flow of air that enters the insect's body through the thoracic region and exits through the abdominal region.
Tracheal system, of course, is very effective in terms of gas exchange, however, it should be borne in mind that gas exchange in most insects is determined solely by the diffusion of oxygen through the tissues of the insect. Diffusion, as is known, is effective only over short distances, and this imposes severe restrictions on the size that insects can reach. These small distances at which diffusion is quite effective do not exceed 1 cm; therefore, although there are insects up to 30 cm long, their body should not be more than 2 cm thick.
In the section on the question how do earthworms breathe? given by the author European the best answer is There are no special respiratory organs: they breathe over the entire surface of the body. The thin cuticle and tenderness of the skin, the rich network of skin blood vessels provide the ability to absorb oxygen from the environment. The cuticle is well wetted by water, and oxygen first dissolves in water. This entails the need to keep the skin moist.
Earthworms (lat. Lumbricidae) are a family of worms from the class Oligochaeta, a type of annelids (Annelida). This family includes rather large worms (from 10 to 30 cm in length) with thick skin, red blood and no eyes; in each ring two pairs of small hooked bristles protrude from each side.
The genera and species of this family differ in the shape of the head (the so-called upper lip), in the position of the girdle and in the number of rings; In Russia there are several species of earthworms from the genera: Lumbricus, Dendrobaena and Allolobophora.
Earthworms live in the ground, in which they dig long tubular tunnels; at night they come to the surface of the earth; they drag various organic remains into their passages - particles of leaves and other plant parts. They feed on decaying organic substances. The feces of earthworms, containing a lot of crushed earth particles, are deposited on the surface of the earth. By doing this, earthworms help increase the arable layer of the soil, while with their burrows they loosen the soil, and by pulling out plant residues they increase its content with organic parts.
The importance of earthworms in the process of soil formation was first indicated by Darwin.
Fertilization occurs at night, on the surface of the earth, and is mutual; both individuals fit tightly to each other, turning with opposite ends, and the seed of one individual flows into the seed receptacles of the other; in this case, both individuals are connected to each other by a ring formed by the secretion of special glands of the so-called girdle; At the end of the act, the ring is reset.
Earthworms are used as bait for fishing.
Earthworm – Lumbricus terrestris(type Annelids, class Oligochaete worms, family Lumbricidae) lives in moist, humus-rich soil. It feeds on organic matter, passing soil and plant debris through its intestines. Even Charles Darwin noted the beneficial effect of earthworms on soil fertility. By dragging the remains of plants into the burrows, they enrich it with humus. By making passages in the soil, they facilitate the penetration of air and water to the roots of plants.
Earthworms are active in warm time of the year. In winter they hibernate. Freezing kills the worms instantly, so they must burrow deeper into the ground, where low temperatures do not penetrate. In the spring, when the temperature reaches a suitable level and the ground is saturated with rainwater, their mating season begins. They reproduce very quickly, producing about a hundred young worms per year. In summer, worms are not as active. There is very little food - dying plant debris - at this time, and the soil is deprived of moisture, which can cause the death of worms. Autumn period again characterized by worm activity. At this time, reproduction of offspring begins again, which lasts until the onset of winter.
Earthworms live relatively long. Some manage to live for about ten years if they do not become victims of birds and moles. Another threat to their life is the pesticides that are so widely used in gardening today.
So, the earthworm has an elongated, cylindrical body from 10 to 30 cm long. Dorsal side more rounded, it is darker, the dorsal blood vessel is visible through its skin. Abdominal side somewhat flattened and lighter colored. The anterior end of the body is thicker and darker in color. The body consists of rings - segments. In an adult worm, their number reaches 200. In the area of 32-37 body segments there is belt, rich in mucous glands. External segmentation corresponds to the division of the body cavity by partitions into separate chambers and segmental (i.e. in each segment) row arrangement internal organs. On each segment 8 bristles(they are easy to detect if you run your finger along the body of the worm in the direction from the rear end of the body to the front). The setae are arranged in four pairs on the lateral sides of the segments. Clinging to uneven soil, the worm moves forward with the help of the muscles of the skin-muscular sac.
Veils. The earthworm's body is covered skin-muscle bag. He is educated cuticle, single layer epithelium and two layers of muscles - external circular and internal longitudinal. The skin epithelium of the worm is rich mucous glands, which produce slime, covering the entire body of the worm and protecting it from drying out. Mucus also makes crawling in burrows easier by reducing friction with the soil.
Movement of an earthworm. When a worm crawls, waves of muscle contractions run through its body, and both the length and thickness of individual parts of its body are constantly changing. The movements produced by each part of the body consist in the fact that its constituent segments either stretch and become thinner, or contract and become thicker. As a result of such alternating stretching and contraction, the worm gradually moves forward: first, its head end is pulled forward, and then the posterior segments of the body are gradually pulled towards it; after this, the rear end of the body remains in place, and the head end is pushed even further forward, and thus the further advancement of the worm continues (it is convenient to observe it by letting the worm crawl along paper spread on the table).
Body cavity. Inside the skin-muscle sac of annelids there is secondary body cavity, or in general. This body cavity is not limited by muscles, as in roundworms, but has its own epithelial(coelomic) lining, i.e. the inner side of the longitudinal muscles is lined with epithelium of mesodermal origin, and there is also an epithelial lining on the side of the intestine lying in the body cavity. Due to the coelomic epithelium, internal two-layer transverse partitions are formed between the segments - dissepiments. The secondary cavity is divided into chambers, each segment containing a pair of coelomic sacs. The coelomic fluid is under pressure and plays a role hydroskeleton, so the worm feels elastic to the touch.
Digestive system comprises front, average And hindgut. Mouth located on the second segment on the ventral side of the body. Anal hole
type Annelids Earthworm
At the posterior end of the body, it looks like a small slit. Due to feeding on rotting plant remains and humus, digestive system has a number of features. Its anterior section is differentiated into muscular throat, esophagus, goiter and muscular stomach. To increase the absorption surface, a fold has formed on the upper part of the intestine typhlosol(typhlozolis). Please note: differentiated sections of the foregut - pharynx, esophagus, crop, stomach - were absent in previous types of worms.
Breath. An earthworm breathes over the entire surface of its body due to the presence of a dense subcutaneous network of capillary blood vessels. Therefore, it is important that the worm’s body covers do not dry out, but excessive moisture (for example, very wet soil after rain) is just as destructive for them.
Circulatory system closed, that is, blood moves through the vessels without spilling into the body cavity. The movement of blood is determined by the pulsation of large vessels, mainly surrounding the esophagus. These are kind of hearts. Blood supplies all organs and tissues with nutrients, transporting them from the intestines, and oxygen entering the skin capillaries from external environment. By spinal vessel blood moves from the back end of the body to the front, and along abdominal vessel- in the opposite direction. An earthworm's blood is red. An iron-containing protein, similar to vertebrate hemoglobin and transporting oxygen, is found in a dissolved state in the blood plasma, and red blood cells are absent.
Nervous system more complex than that of flatworms and roundworms. It consists of peripharyngeal nerve ring with ganglia and abdominal nerve cord. This is the so-called nervous system ladder type. Suprapharyngeal paired ganglion performs the functions of the brain and is more developed than subpharyngeal. The nerve chain originates from the subpharyngeal node and consists of segmentally located pairs of ganglia, connected to each other by transverse and longitudinal commissures. Nerves extend from the ganglia to various organs. The earthworm's sense organs are poorly developed: there are no eyes or tentacles, but their skin contains numerous sensory cells and nerve endings.
Excretory organs presented segment by segment (i.e. in each segment) arranged in pairs metanephridia. They look like convoluted tubes and begin in the body cavity as a funnel with cilia. A channel departs from the funnel, which penetrates the transverse septum and passes into the cavity of the next segment. The terminal section of the metanephridium has an extension - bladder, which opens outward on the side of the worm’s body (i.e., in each segment there is a pair of very small excretory holes). In addition to metanephridia, the secretion involves chloragogenic cells, covering the surface of the intestine with a thin brown-yellow coating. Chlorogenic cells accumulate excretion products. Filled with metabolic products, these cells die, and their contents enter the body cavity, from where they are removed by metanephridia.
Reproduction. Earthworms hermaphrodites. The reproductive organs and girdle can be examined only during the breeding season - in the spring. To male
type Annelids Earthworm
the reproductive system includes two pairs of testes, located in segments 10 and 11, four vas deferens, which merge in pairs and open outwards paired male genital opening, located in the 15th segment. The female reproductive system includes pair of ovaries located in segment 13, oviducts, which open outwards in the 14th segment a pair of female genital orifices. There are two pairs in segments 9 and 10 spermatheca, each of which opens outward with an independent hole.
Earthworms reproduce sexually. Cross fertilization, in a cocoon. Two worms meet, tightly wrap their bodies around each other, attach their ventral sides to each other and exchange sperm, which ends up in the spermatic receptacles. After this, the worms disperse. Next, the belt forms a mucous muff, in which eggs are laid. As the coupling moves through the segments containing the spermatheca, the eggs are fertilized by sperm belonging to another individual. The muff is shed through the anterior end of the body, becomes compacted and turns into an egg cocoon, where young worms develop.
Regeneration. Earthworms are characterized by a high ability to regenerate, i.e. From each piece of the torn body of an earthworm, a whole worm is restored.
Questions for self-control
Name the aromorphoses of the annelid type.
Name the classification of the type Annelids.
What's it like systematic position earthworm?
Where do earthworms live?
What body shape do earthworms have?
What is the body of an earthworm covered with?
What body cavity is characteristic of an earthworm?
What is the structure of the worm's digestive system?
What is the structure of the worm's circulatory system?
How does an earthworm breathe?
What structure does it have? excretory system worm?
What is the structure of the worm's nervous system?
What structure does it have? reproductive system earthworm?
How does an earthworm reproduce?
What is the significance of an earthworm?
type Annelids Earthworm
Rice. Earthworm, its passages in the ground and movement.
Rice. Internal structure of an earthworm.
1, 16 - intestine; 2 - partitions; 3 - epithelial lining of the secondary body cavity; 4 - dorsal (back) blood vessel; 5 - ring blood vessel; 6 - skin-muscle bag; 7 - cuticle; 8 - skin epithelium; 9 - whole; 10 - metanephridium; 11 - eggs; 12 - ring muscles; 13 - longitudinal muscles; 14 - ventral (abdominal) blood vessel; 15 - abdominal nerve cord.
type Annelids Earthworm
Rice. The structure of the anterior end of the earthworm's body.
The prostomium is the protrusion of the upper part of the first segment, covering the mouth. Peristomium is the name of the first segment of the body.
type Annelids Earthworm
Rice. The structure of an earthworm.
A - head end; B - internal structure; B - nervous system.
1 - mouth opening; 2 - male genital opening; 3 - female genital opening; 4 - belt; 5 - pharynx; 6 - esophagus; 7 - goiter; 8 - stomach; 9 - intestines; 10 - dorsal blood vessel; 11 - ring blood vessels; 12 - abdominal blood vessel; 13 - metanephridia; 14 - ovaries; 15 - testes; 16 - seed sacs; 17 - seminal receptacles; 18 - peripharyngeal nerve node; 19 - peripharyngeal nerve ring; 20 - abdominal nerve cord; 21 - nerves.
type Annelids Earthworm
Rice. Longitudinal section of the body of an earthworm.
1 - mouth; 2 - pharynx; 3 - esophagus; 4 - goiter; 5 - stomach; 6 - intestine; 7 - peripharyngeal ring; 8 - abdominal nerve chain; 9 - “hearts”; 10 - dorsal blood vessel; 11 - abdominal blood vessel.
