Annelid worms structure drawing. Earthworms: photos, videos and descriptions of “earthly” inhabitants. Changes in acid-base balance
home Animals, suborder earthworms. Body earthworm consists of ring-shaped segments, the number of segments can reach up to 320. When moving, earthworms rely on short bristles, which are located on the body segments. When studying the structure of an earthworm, it is clear that, unlike the whipworm, its body looks like a long tube. Earthworms
distributed throughout the planet, except Antarctica.
Appearance
Adult earthworms are 15–30 cm in length. In the south of Ukraine it can reach large sizes. The body of the worm is smooth, slippery, has a cylindrical shape and consists of piece rings - segments. This shape of the worm’s body is explained by its way of life; it facilitates movement in the soil. The number of segments can reach 200. The ventral side of the body is flat, the dorsal side is convex and darker than the abdominal side. Approximately where the front part of the body ends, the worm has a thickening called the girdle. It contains special glands that secrete a sticky liquid. During reproduction, an egg cocoon is formed from it, inside which the worm eggs develop.
they crawl deep into the ground.
An earthworm moves by crawling. At the same time, it first retracts the front end of the body and clings to uneven soil with bristles located on the ventral side, and then, contracting the muscles, pulls up the rear end of the body. Moving underground, the worm makes passages in the soil. At the same time, he pushes the earth apart with the pointed end of his body and squeezes between its particles.
Moving in dense soil, the worm swallows the soil and passes it through the intestines. The worm usually swallows the earth at a considerable depth and throws it out through the anus near its burrow. This is how long “laces” of soil and lumps are formed on the surface of the earth, which can be seen on garden paths in the summer.
This method of movement is possible only with well-developed muscles. Compared to the hydra, the earthworm has more complex muscles. It lies under his skin. The muscles together with the skin form a continuous musculocutaneous sac.
The muscles of an earthworm are located in two layers. Under the skin lies a layer of circular muscles, and below them is a thicker layer of longitudinal muscles. Muscles are made up of long contractile fibers. When the longitudinal muscles contract, the body of the worm becomes shorter and thicker. When the circular muscles contract, on the contrary, the body becomes thinner and longer. By contracting alternately, both layers of muscles cause the movement of the worm. Muscle contraction occurs under the influence of the nervous system, which branches out in muscle tissue. The movement of the worm is greatly facilitated by the fact that there are small bristles on its body on the ventral side. They can be felt by running a finger dipped in water along the sides and ventral side of the worm's body, from the rear end to the front. With the help of these bristles, the earthworm moves underground. They also hold him back when he is pulled out of the ground. With the help of bristles, the worm descends and rises along its earthen passages.
Nutrition
Earthworms feed mainly on half-rotted plant remains. They drag leaves, stems, etc. into their burrows, usually at night. Earthworms also feed on humus-rich soil, passing it through their intestines.
Circulatory system
The earthworm has circulatory system, which hydra does not have. This system consists of two longitudinal vessels - dorsal and abdominal - and branches that connect these vessels and carry blood. The muscular walls of the blood vessels, contracting, drive blood throughout the worm’s body.
The blood of an earthworm is red; for the worm, as for other animals, it is very important. With the help of blood, communication between the animal’s organs is established and metabolism occurs. Moving through the body, it spreads from the digestive organs nutrients, as well as oxygen supplied through the skin. At the same time, blood is carried from the tissues into the skin carbon dioxide. Various unnecessary and harmful substances, formed in all parts of the body, enter the excretory organs along with the blood.
Irritation
The earthworm has no special sense organs. It perceives external irritations with the help of the nervous system. The earthworm has the most developed sense of touch. Sensitive tactile nerve cells located over the entire surface of his body. The sensitivity of the earthworm to various kinds of external irritation is quite high. The slightest vibrations in the soil cause it to quickly hide, crawling into a hole or into deeper layers of soil.
The importance of sensitive skin cells is not limited to the sense of touch. It is known that earthworms, without special organs of vision, still perceive light stimulation. If you suddenly shine a flashlight on a worm at night, it quickly hides.
The animal's response to stimulation, carried out using the nervous system, is called a reflex. There are different types of reflexes. Contraction of the worm's body by touch, its movement when suddenly illuminated by a lantern has protective value. This is a protective reflex. Grasping food is a digestive reflex.
Experiments also show that earthworms sense odors. The sense of smell helps the worm find food. Charles Darwin discovered that earthworms can smell the leaves of the plants they feed on.
Reproduction
Unlike hydra, earthworms reproduce exclusively sexually. It does not reproduce asexually. Each earthworm has male organs - testes, in which the worms develop, and female genital organs - ovaries, in which eggs are formed. The worm lays its eggs in a slimy cocoon. It is formed from a substance secreted by the worm's girdle. In the form of a muff, the cocoon slides off the worm and is pulled together at the ends. In this form, the cocoon remains in the earthen burrow until the young worms emerge from it. The cocoon protects the eggs from dampness and other unfavorable influences. Each egg in the cocoon divides many times, as a result of which tissues and organs of the animal are gradually formed, and, finally, small worms similar to adults emerge from the cocoons.
Regeneration
Like hydras, earthworms are capable of regeneration, in which lost body parts are restored.
Many people underestimate the importance of the work of earthworms. These representatives of the invertebrate kingdom are known primarily for the fact that in large quantities crawl out of the ground after heavy rain. They are often used as bait by numerous fishing enthusiasts. Darwin also noted the fact that worms perform an important function in nature, acting as a kind of agricultural technicians. In the process of creating an extensive system of tunnels, which the earthworm digs through, excellent aeration is formed by supplying air to the inner layers of the soil.
Thanks to excellent aeration, the respiratory activity of many plants is facilitated. Feeding on organic matter and waste, worms ensure the grinding of soil components, enriching them with their secretions. The amazing ability of representatives of this species is the ability to disinfect large areas of soil, sterilizing it from harmful bacteria. Thanks to countless holes, forming a kind of capillary system, ideal drainage and aeration of the soil is ensured.
The body of an earthworm can reach three meters in length. However, on the territory of Russia there are mainly individuals whose body length does not exceed 30 centimeters. In order to move, the worm uses small bristles that are located on different parts torso. Depending on the variety, there can be from 100 to 300 segments. The circulatory system is closed and very well developed. It consists of one artery and one central vein.
The structure of an earthworm is very unusual. Breathing is realized with the help of special hypersensitive cells. The skin produces protective mucus with a sufficient amount of natural antiseptics. The structure of the brain is quite primitive and includes only two nerve nodes. Based on the results of laboratory experiments, earthworms have confirmed their outstanding regeneration abilities. The severed tail grows back after a short period of time.
The genital organs of the earthworm are also very unusual. Each individual is a hermaphrodite. She also has male organs. Based on biological factors, all such worms can be divided into several subgroups. Representatives of one of them search for food on the surface of the soil layer. Others use the soil itself for food and emerge from the ground extremely rarely.
The earthworm is a type of annelid. Under the skin layer there is a developed muscle system consisting of muscles various shapes. The mouth opening, from which food enters the esophagus through the pharynx, is located on the front of the body. From there it is transported to the area of the enlarged crop and the small size of the muscular stomach.
Burrowing and bedding earthworms live in places with loose and moist soil. Preference is given to moist soils of the subtropics, marshy lands and the banks of various reservoirs. In steppe areas, soil varieties of worms are usually found. Litter species live in the taiga and forest-tundra. The coniferous broad-leaved strip can boast the highest concentration of individuals.
What kind of soil do worms like?
Why do earthworms love sandy loam and loam soils? Such soil is characterized by low acidity, which is the most in the best possible way suitable for their life. Acidity levels above pH 5.5 are detrimental to the organisms of these representatives of the ringed type. Wet soils– one of the prerequisites for population expansion. During dry and hot weather, worms go deep underground and lose the opportunity to reproduce.
Character and lifestyle of the earthworm
The active and productive life of an earthworm occurs at night. As soon as night falls, many individuals crawl to the surface of the ground in search of food. However, the tail usually remains in the ground. By morning, they return to their holes with prey, dragging pieces of food into them and masking the entrance to their shelter with blades of grass and leaves.
The role of earthworms in nature is difficult to overestimate. The worm literally passes an incredible amount of soil mixture through itself, enriching it with beneficial enzymes and killing harmful substances and bacteria. The worm moves by crawling. Retracting one end of the body and clinging to the roughness of the ground with its bristles, it pulls up the back part, making its many passages in a similar way.
How do earthworms survive winter?
During the winter, the vast majority of individuals hibernate. A sharp drop in temperature can instantly destroy worms, so they try to burrow into the soil to a depth in advance, often exceeding one meter. Earthworms in the soil perform the most important function of naturally renewing it and enriching it with various substances and microelements.
Benefit
In the process of digesting semi-fermented leaves, the worms’ body produces specific enzymes that contribute to the active generation of humic acid. Soil that has been loosened by earthworms is optimal for a wide variety of representatives of the plant kingdom. Thanks to a system of intricate tunnels, excellent aeration and ventilation of the roots is ensured. Thus, earthworm movement is an important factor in the recovery task. useful qualities soil.
The earthworm is in fact very useful for humans. It makes the soil layers fertile and enriches them with all kinds of nutrients. However, the total number of individuals in many regions of Russia is rapidly declining. This happens due to the uncontrolled introduction of pesticides, fertilizers and mineral mixtures into the soil. Earthworms are also hunted by numerous birds, moles, and various rodents.
What do earthworms eat?
At night, the earthworm crawls to the surface and pulls the half-rotten remains of plants and leaves into its shelter. Also, its diet includes soil rich in humus. One representative of the species can process up to half a gram of soil per day. Considering that up to several million individuals can live simultaneously on an area of one hectare, they are capable of acting as irreplaceable soil converters.
After rain, you can see on the asphalt and soil surface a large number of worms, what makes them crawl out? Even the name “earthworms” indicates that they love moisture very much and become more active after rain. Let's look at a few possible reasons Why do earthworms crawl out to the surface of the earth after rain?
Soil temperature
It is believed that worms crawl to the surface in search of warmth, since after rain the soil temperature drops by several degrees, which causes discomfort for them.
Changes in acid-base balance
Another theory says that the worms crawl to the surface due to a change in the acid-base balance of the soil after rain, it becomes more acidic, which negatively affects these diggers. According to researchers, emergency evacuation to the soil surface saves them from death in an acidic environment.
Lack of air
The third theory explains that after rain there is more oxygen in the top layer of the soil, so the worms crawl up en masse. Water enriches the upper layers of the earth with oxygen, and many species of worms love moisture and vitally need sufficient oxygen. And through the surface of the body, oxygen is absorbed best in a humid environment.
Trips
British scientist Chris Lowe suggested that worms crawl to the surface of the earth during rain in order to make a long journey to new territory. On the surface, worms are able to crawl much further than underground, and dry soil causes discomfort when moving, strong friction is created, and grains of sand stick to the surface of the worm’s body, injuring it. And after rain, the surface of the earth is highly moistened, which allows them to freely travel to new areas of the ground.
Sounds of the rain
Another scientist, Professor Joseph Gorris from the USA, suggested that earthworms They are frightened by the sound of rain, since the vibrations it creates are similar to the sound of the approach of their main enemy - the mole. That is why some fishermen use a technique to lure bait to the surface: they insert a stick into the ground, attach a sheet of iron to its surface and pull it so as to create a vibration, which will be transmitted into the ground through the stick. When frightened, the worms climb to the surface of the earth and become easy prey for experienced fishermen.
Reproduction and lifespan of earthworms
The earthworm is a hermaphrodite. It has both female and male genital organs. However, it is not capable of self-fertilization. With the onset of warm temperatures required for reproduction climatic conditions individuals crawl in pairs, touching each other with their abdominal region, and perform a kind of exchange of seed. Afterwards, the muff is transformed into a cocoon, in which the eggs develop.
Some varieties are different asexual reproduction. The worm's body splits in two, with one part regenerating the front end and the other regenerating the back end. There are also species of worms that reproduce without spermatheca by laying spermatophores. The lifespan of worms can exceed ten years.
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 at the roots in pots, eat seedlings, sprouts, seeds...”, etc. Therefore, to destroy worms, a wide variety of methods are invented, the most harmless of which - soil freezing. And they say all sorts of nonsense about earthworms. I myself communicated with such people, convincing them of the opposite, namely, what invaluable help and benefit these tireless workers bring.
So, let's start studying the earthworm to understand how its vital functions are maintained.
To absorb food, worms have an organ called pharynx. It works on the principle of a rubber bulb: when compressed and then unclenched, a vacuum is created, thanks to which food is drawn inside. It is clear that there are no teeth in the mouth, therefore, the worm is not able to gnaw or bite anything.
In order to pass through the rather small mouth opening, food must be sufficiently soaked or softened. Therefore, plant food (shoots, leaves) should not be freshly picked (or freshly bitten), 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.
Goiter- This is a large thin-walled cavity in which swallowed food accumulates. What happens next? What to do without teeth? It turns out that the worm has them too, only they are located... in the stomach!
Stomach- this is a muscular thick-walled chamber, inner surface which consists of hard tooth-like projections. When the walls of the stomach contract, they crush (grind) food into fine particles. And already in this state, the 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 is constructed in a similar way in crocodiles and most birds.
The peculiarities of their digestion make earthworms detritivorous, that is, they eat detritus- decaying plant organic matter located on the surface of the earth or in their underground burrows, as well as in the soil itself, in contact with the soil itself. Therefore, the coprolites that the earthworm leaves behind are lumps of soil enriched with nitrogen, microelements, and having low acidity thanks to the alkaline environment of his intestines.
If you carefully examine the picture, you will see that the worm has a brain, nerves, and a heart (of which there is not even one, but five!). That is, the earthworm feels and understands everything, but it cannot say. Here's another tragic secret, still not understood by biologists and not revealed by criminologists: why do they crawl out onto footpaths after the rain and then die en masse?
The earthworm has its own "Achilles' heel", its own weakness. the whole point is that worms require energy for normal functioning. And they get it through respiration (and oxygen oxidation), which requires gas exchange between the body and the environment.
The structure of an earthworm is such that special body for gas exchange (such as lungs or gills) the worm does not have, so it breathes skin. To do this, it must be thin and constantly moisturized. Since worms do not have any protective shell, the most common reason for their death is desiccation.
The body of earthworms consists of many ring-shaped segments (from 80 to 300), which can be easily seen. The worm can be both slippery and rough. He resists bristles- they are on each ring and are visible with a regular magnifying glass.
Bristles - main support in the life of a worm, it is very convenient for them to grab onto tiny unevenness in the soil, which is why it is so difficult to pull the worm out of the hole - it would rather allow itself to be torn in half. Thanks to the bristles, it is inactive on the surface and deftly evades danger.
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, which constitutes as much as 80% of the total weight in the worm.
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. But this doesn't always happen. So let's take care of our underground architects, the "angels of the earth", and create favorable conditions for them. And they, in turn, will thank us with healthy soil on our plots and a generous harvest.
The body of the earthworm is round in shape; the length of most representatives of this genus is no more than 15 centimeters, occasionally more than twenty, and the length of the largest is slightly more than thirty centimeters.
Consists of 100-180 segments. The segments have small, fairly elastic bristles that are practically invisible, but if you run your finger from the rear tip to the front, you can immediately feel it. The worm needs bristles so that it can cling to uneven ground surfaces while moving.
On the front of the worm's body there is a small thickening that serves as the place where the genital organs are located. The cells located in this thickening are activated during reproduction to lay eggs. If you look closely, you will notice that the belly of the earthworm is somewhat lighter than the rest of the parts. The worm has not only a circulatory system, but also a nervous and tactile system. digestive system.
What environment do earthworms live in?
During the daytime, worms prefer to stay in the soil of the swarm, with passages in it. Light soil, the worm drills with its front tip. To do this, he first compresses the front part so that it becomes thinner, and tries to push it forward between the soil lumps. Subsequently, the front tip becomes thicker, the lumps move apart, and the worm pulls up the back part. In hard soil, raincoats make passages for themselves, passing them through the intestinal tract. Earthen heaps are often visible on the surface of the earth - these are traces of the night activity of worms. They emerge from their burrows after heavy rainfall (that’s why they are called rainfall). IN summer time worms prefer to stay in the upper layers of the soil, and in winter, to escape the cold, they dig holes, the depth of which can be more than two meters.
As the temperature drops, they become less active and their circulatory system circulates more slowly.
Taking a worm in your hands, you will find that its skin is moist, and it itself is covered with mucus, which makes it easier to move in the ground. Apart from this, only through the moist skin does the oxygen required for respiration find its way into his body. This is how the worm breathes.
Directly below skin There are circular muscles fused with it, and longitudinal ones underneath them. Those. An earthworm is a kind of skin-muscular sac. Thanks to the circular muscles, the body of the worm becomes thinner and longer, and thanks to the longitudinal muscles, it shortens and thickens. Due to the alternate functioning of these data, the muscle and the worm move.
How does an earthworm work?
The structure of an earthworm, when compared with the organisms of other animals, is quite primitive, but it has quite interesting features. Under the skin-muscular pouch there is a fluid-filled cavity of the body, and it contains the internal organs. When compared with roundworms, the body cavity of a roundworm is divided by septa, the number of which is equal to the number of segments. They have their own separate walls and are located under the skin-muscular pouch.
Now let's take a closer look at all the available organs of the worm.
Digestive system
The earthworm's mouth is located at the front. The puffball prefers rotting vegetation, swallowing it with soil. Likewise, he often drags fallen leaves into his hole. Swallowing is accomplished through the pharynx. Next, the food ends up in the intestines. Food that has not had time to be digested comes out through the anus located at the back. This is how the digestive system works in almost all types of worms. The worm also needs its mouth in order to drag various small objects to which it simply sticks. As you can see, the digestive system is quite primitive and lacks the organs that higher beings have.
The earthworm has a closed circulatory system, but there are some peculiarities. It is based on two main vessels, the dorsal and the abdominal, which are connected to each other using ring vessels, in some ways very similar to arteries and veins. Depending on the species, the blood of worms can be colorless, red or even green.
Speaking about the circulatory system of the earthworm, the dorsal vessel, which pulsates blood throughout the body, deserves special attention.
Special vessels that cover the intestines and are located in all segments, distill blood into the cavity of the abdominal vessel, which cannot pulsate on its own. The worm's blood flow is from front to back. In addition to these blood flows, there are also vessels that carry blood from the dorsal to the parapodial vessels. In them, the blood oxidizes when it comes into contact with environmental oxygen.
The skin of an annelid worm also has its own vessels, which are connected to the general circulatory system. Those. The circulatory system of worms is quite complex, but it is thanks to it that worms survive in rather difficult conditions.
Nervous system
The nervous system of annelids consists of two nerve trunks. Nerve nodes are formed in the segments on them. those. a kind of nerve chain emerges. In front, two nodules are connected to each other by circular bridges - a perioral nerve ring is formed. Nerves go from the nodules to various organs.
Organs of touch
Worms do not have special organs of touch, but sensitive cells in the skin allow it to feel touch and distinguish when it is light and when it is dark.
Reproductive system
As you know, and we have already talked about this, worms are hermaphrodites, that is, they can do without mating. But most often, reproduction occurs after contact between two individuals and the exchange of sperm between them. Then they spread out, and mucus begins to secrete from a kind of coupling located in front. Into which the eggs subsequently arrive. Then the lump of mucus slides off the worm's body, forming a cocoon. From which small worms are subsequently obtained.
This video talks about the structural features of earthworms.
In the world of fauna is the earthworm. He can rightfully be called an earth worker, since it is thanks to him that the soil on which we walk is completely saturated with oxygen and other minerals. By passing various sections of the ground lengthwise and crosswise, this worm makes them loose, which then allows them to be planted there. cultivated plants and also do gardening.
General characteristics of the species
The earthworm belongs to the kingdom Animalia, to the subkingdom Multicellular. Its type is characterized as Ringed, and its class is Oligochaete. The organization of annelids is very high compared to other types. They have 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 airbag for the animal. Also, thanks to them, each individual segment of the worm’s body can exist autonomously and progress in development. The habitats of these earthly orderlies are wet soil, salty or fresh water.
External structure of an earthworm
The worm's body is round in shape. 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 worm's body has a small thickening in which the so-called genital organs are concentrated. Local cells are activated during the breeding season and perform the function of laying eggs. The lateral outer parts of the worm's body are equipped with short bristles, completely invisible to the human eye. They allow the animal to move in space and move through the ground. It is also worth noting that the earthworm’s tummy is always painted in a lighter tone than its back, which has a dark burgundy, almost brown color.
What is he like from the inside?
The structure of the earthworm differs from all other relatives 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 are divided into two categories: circular 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 you to work more fully. internal organs. The muscles of each individual segment of the worm's body can function autonomously. When moving, the earthworm alternately compresses each ring group of muscles, as a result of which its body either stretches or becomes shorter. This allows him to dig new tunnels and fully loosen the ground.
Digestive system
The structure of a worm is extremely simple and understandable. It originates from the mouth opening. Through it, food enters the pharynx and then passes through the esophagus. In this segment, products are purified from acids released by rotting products. The food then passes through the crop and into the stomach, which contains many small muscles. Here the products are literally ground up and then enter the intestines. The worm has one midgut, which goes into the posterior opening. In its cavity, all useful substances from food are absorbed into the walls, after which waste leaves the body through the anus. It is important to know that earthworm excrement is rich in potassium, phosphorus and nitrogen. They perfectly nourish the earth and saturate it with minerals.
Circulatory system
The circulatory system possessed by an earthworm can be divided into three segments: the abdominal vessel, the dorsal vessel and the annular vessel, which combines the previous two. The blood flow in the body is closed, or circular. The annular vessel, which is shaped like a spiral, unites two vital arteries for the worm in each segment. Capillaries also branch from it, which 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 blood is driven from the abdominal artery to the spinal artery. It is noteworthy that earthworms like humans they have red blood. This is due to the presence of hemoglobin, which is regularly distributed throughout the body.
Breathing and the nervous system
The earthworm's breathing process occurs 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. Nervous system This animal is much more interesting. The main “lump” in which all the neurons in the a huge number, is located in the anterior segment of the body, but its analogues, smaller in size, are in each of them. Therefore, each segment of the worm’s body can exist autonomously.
Reproduction
Let us immediately note 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 part of the body, and during the mating period (and it is cross-breeding), 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 will feed the embryo. As a result of these processes, a mucous membrane is formed in which embryos develop. Afterwards they leave it, back end first, and crawl into the ground to continue their lineage.