Is freshwater hydra poisonous? Movement, reproduction and nutrition of freshwater hydra

The freshwater hydra is amazing creature, which is not easy to detect due to its microscopic size. Hydra belongs to the type of intestinal cavities.

The habitat of this small predator is rivers overgrown with vegetation, dams, lakes without strong currents. The easiest way to observe a freshwater polyp is through a magnifying glass.

It is enough to take water with duckweed from the reservoir and let it stand for a while: soon you will be able to see oblong "wires" of white or brown color 1-3 centimeters in size. This is how the hydra is depicted in the drawings. This is what a freshwater hydra looks like.

Structure

The body of the hydra has a tubular shape. It is represented by two types of cells - ectoderm and endoderm. Between them is the intercellular substance - mesoglea.

In the upper part of the body, you can see the mouth opening, framed by several tentacles.

On the opposite side of the "tube" is the sole. Thanks to the suction cup, attachment to stems, leaves and other surfaces occurs.

Hydra ectoderm

The ectoderm is the outer part of the body cells of an animal. These cells are essential for the life and development of the animal.

The ectoderm is made up of several types of cells. Among them:

• skin-muscle cells they help the body move and squirm. When the cells contract, the animal shrinks or, on the contrary, stretches. A simple mechanism helps the hydra to move freely under the cover of water with the help of “tumbles” and “steps”;
• stinging cells - they cover the walls of the body of the animal, but most of concentrated in the tentacles. As soon as small prey swims next to the hydra, it tries to touch it with its tentacles. At this moment, stinging cells release "hairs" with poison. Paralyzing the victim, the hydra draws it to the mouth opening and swallows it. This simple scheme allows you to easily get food. After such work, stinging cells self-destruct, and new ones appear in their place;
• nerve cells. The outer shell of the body is represented by star-shaped cells. They are interconnected, forming a chain of nerve fibers. So educated nervous system animal;
• sex cells actively grow in the autumn. They are egg (female) germ cells and spermatozoa. The eggs are located near the mouth opening. They grow rapidly, consuming nearby cells. Spermatozoa, after maturation, leave the body and swim in the water;
• intermediate cells. they serve as a protective mechanism: when the animal's body is damaged, these invisible "defenders" begin to actively multiply and heal the wound.

Hydra endoderm

Endoderm helps hydra digest food. Cells line the digestive tract. They capture food particles, delivering it to the vacuoles. Digestive juice secreted by glandular cells processes useful substances necessary for the body.

What does a hydra breathe

Freshwater hydra breathes on the outer surface of the body, through which the oxygen necessary for its life functions enters.

In addition, vacuoles are also involved in the process of respiration.

Reproduction features

In the warm season, hydras reproduce by budding. it asexual way breeding. In this case, a growth forms on the body of the individual, which increases in size over time. From the "kidney" tentacles grow, and a mouth is formed.

In the process of budding, a new creature is separated from the body and goes into free swimming.

In the cold period of time, hydras reproduce only sexually. In the body of an animal, eggs and spermatozoa mature. Male cells, leaving the body, fertilize the eggs of other hydras.

After the function of reproduction, adults die, and the fruit of their creation is zygotes, covered with a dense "dome" in order to survive the harsh winter. In the spring, the zygote actively divides, grows, and then breaks through the shell and begins an independent life.

What does hydra eat

Hydra nutrition is characterized by a diet consisting of miniature inhabitants of reservoirs - ciliates, water fleas, planktonic crustaceans, insects, fish fry, worms.

If the victim is small, the hydra swallows it whole. If the prey is large, the predator is able to open its mouth wide, and significantly stretch the body.

Hydra regeneration

G hydra has unique ability A: She doesn't age. Each cell of the animal is updated in a couple of weeks. Even having lost a part of the body, the polyp is able to grow exactly the same, restoring symmetry.

The hydra, cut in half, does not die: a new creature grows from each part.

The biological significance of freshwater hydra

Freshwater hydra is an indispensable element in the food chain. This unique animal plays an important role in the cleansing of water bodies, regulating the population of its other inhabitants.

Hydras are a valuable object of study for scientists in biology, medicine and science.

Hydra - protozoan from the order Intestinal. This freshwater polyp lives in almost every reservoir. It is a translucent gelatinous body, similar to a self-moving stomach, where the hydra digests food.

How hydra eats

The size of this simplest organism rarely exceeds 2 cm. Outwardly, the hydra resembles a mucous tube of a greenish or brown color. Its color depends on the food eaten. With one end of the body, it is attached to plants, stones or snags in the water, and with the other it catches prey. Basically, it is small invertebrates - daphnia, cyclops, oligochaetes-naidids. Sometimes small crustaceans, as well as fish fry, serve as food.

The mouth opening of the hydra is surrounded by tentacles, of which there are six to twenty pieces. They are in constant motion. As soon as the victim touches them, located in the tentacles, they immediately throw out a pointed thread containing poison. Plunging into an approaching animal, she paralyzes it and, pulling it up with tentacles, brings it to her mouth. At the same time, it seems that her body, as it were, is put on the victim, who thus finds herself in the intestines, where the digestion of food begins in the hydra. The poison stinging capsule can only be used once, after which it is replaced with a new one.

The structure of the digestive system

The body of the hydra is very similar to a two-layer bag, which is called the ectoderm, and the inner one is the endoderm. Between them is a structureless substance called mesoglea.

The composition of the inner layer, where the hydra digests food, is mainly glandular and digestive cells. The first secrete digestive juice into the intestinal cavity, under the influence of which the food eaten is liquefied and breaks up into small particles. Other cells in the inner layer grab these pieces and pull them in.

Thus, the process of digestion begins in the intestinal cavity, and ends inside the cells of the endoderm. All the remnants of food that could not be digested are thrown out through the mouth.

How does the hydra

The digestive cells of the inner layer have from 1 to 3 flagella at the end, with the help of which small particles food is drawn in and digested. The absence of a transport system in the hydra body complicates the task of providing ectoderm cells nutrients, given that the mesoglea is quite dense. This problem is solved due to the existing outgrowths on the cells of both layers. They cross by connecting through gap junctions. Organic molecules in the form of amino acids and monosaccharides, passing through them, provide nutrition to the ectoderm.

When the waste products of cellular metabolism remain where the hydra digests food, it contracts, resulting in emptying.

The first person who saw and described the hydra was the inventor of the microscope and the greatest naturalist of the 17th-18th centuries A. Leeuwenhoek.

Examining aquatic plants under his primitive microscope, he saw strange creature with "hands in the form of horns." Leeuwenhoek even managed to observe the budding of the hydra and see its stinging cells.

The structure of freshwater hydra

Hydra (Hydra) is a typical representative of intestinal animals. The shape of her body is tubular, at the front end there is a mouth opening, surrounded by a corolla of 5-12 tentacles. Immediately below the tentacles, the hydra has a slight narrowing - a neck that separates the head from the body. The rear end of the hydra is narrowed into a more or less long leg, or stalk, with a sole at the end. A well-fed hydra has a length of no more than 5-8 millimeters, a hungry one is much longer.

The body of the hydra, like all coelenterates, consists of two layers of cells. In the outer layer, the cells are diverse: some of them act as organs for killing prey (stinging cells), others secrete mucus, and still others have contractility. Nerve cells are also scattered in the outer layer, the processes of which form a network covering the entire body of the hydra.

Hydra is one of the few representatives of freshwater coelenterates, the bulk of which are inhabitants of the sea. In nature, hydras are found in various water bodies: in ponds and lakes among aquatic plants, on the roots of duckweed, a green carpet covering ditches and pits with water, small ponds and river backwaters. In reservoirs with clean water hydras can be found on bare stones near the shore, where sometimes they form a velvety carpet. Hydras are photophilous, therefore they usually stay in shallow places near the coast. They are able to distinguish the direction of the flow of light and move towards its source. When kept in an aquarium, they always move to a lighted wall.

If you collect more aquatic plants in a vessel with water, then you can observe hydras crawling along the walls of the vessel and the leaves of plants. The sole of the hydra secretes a sticky substance, due to which it is firmly attached to stones, plants or the walls of the aquarium, and it is not easy to separate it. Occasionally, the hydra moves in search of food. In the aquarium, you can mark daily with a dot on the glass of the place of its attachment. Such experience shows that in a few days the movement of the hydra does not exceed 2-3 centimeters. To change place, the hydra temporarily sticks to the glass with its tentacles, separates the sole and pulls it up to the front end. Having attached its sole, the hydra straightens up and again rests its tentacles one step forward. This method of movement is similar to how the caterpillar of moth butterflies, colloquially called "surveyor", walks. Only the caterpillar pulls the rear end to the front, and then again moves the head end forward. Hydra, with such walking, constantly turns over its head and thus moves relatively quickly. There is another, much slower way to move - sliding on the sole. By the force of the musculature of the sole, the hydra barely noticeably moves from its place. For some time, hydras can swim in the water: having detached from the substrate, spreading their tentacles, they slowly fall to the bottom. A gas bubble may form on the sole, which drags the animal upward.

How do freshwater hydras eat?

Hydra is a predator, it feeds on ciliates, small crustaceans - daphnia, cyclops and others, sometimes larger prey comes across in the form of a mosquito larva or a small worm. Hydras can even harm fish ponds by eating fish fry that have hatched from eggs.

Hydra hunting is easy to observe in an aquarium. Spreading their tentacles wide so that they form trapping net, hydra hanging tentacles down. If you watch a sitting hydra for a long time, you can see that its body is slowly swaying all the time, describing a circle with its front end. A cyclops swimming by touches its tentacles and starts to fight to free itself, but soon, struck by stinging cells, it calms down. Paralyzed prey is pulled by a tentacle to the mouth and consumed. With a successful hunt little predator swells from swallowed crustaceans, the dark eyes of which shine through the walls of the body. Hydra can swallow prey larger than itself. At the same time, the mouth of the predator opens wide, and the walls of the body are stretched. Sometimes a piece of unplaced prey sticks out of the hydra's mouth.

Reproduction of freshwater hydra

At good nutrition hydra quickly begins to bud. The growth of a kidney from a small tubercle to a fully formed, but still sitting on the body of the maternal individual, hydra takes several days. Often, while the young hydra has not yet separated from the old individual, the second and third kidneys are already formed on the body of the latter. This is how asexual reproduction occurs. sexual reproduction observed more often in autumn with a decrease in water temperature. Swellings appear on the body of the hydra - sex glands, some of which contain egg cells, and others - male sex cells, which, floating freely in water, penetrate into the body cavity of other hydras and fertilize immobile eggs.

After the formation of eggs, the old hydra usually dies, and young hydras emerge from the eggs under favorable conditions.

Freshwater hydra regeneration

Hydras have an extraordinary ability to regenerate. A hydra cut into two parts grows tentacles on the lower part and a sole on the upper very quickly. In the history of zoology, remarkable experiments with hydra, carried out in the middle of the 17th century, are famous. Dutch teacher Tremblay. He not only managed to get whole hydras from small pieces, but even spliced ​​halves of different hydras together, turning their body inside out, getting a seven-headed polyp similar to the Lernean hydra from myths Ancient Greece. Since then, this polyp has been called hydra.

In the reservoirs of our country there are 4 types of hydras, which differ little from each other. One of the species is characterized by a bright green color, which is due to the presence in the body of hydra symbiotic algae - zoochlorella. Of our hydras, the most famous are the stalked or brown hydra (Hydra oligactis) and the stemless or common hydra (H. vulgaris).

freshwater hydra- extremely unwanted settlers in the aquarium where they are kept shrimps. Unfavorable conditions can cause hydra breeding, a hydra regeneration from the smallest remains of her body makes her almost immortal and indestructible. But still, there are effective methods fighting hydra.

What is a hydra?

Hydra(hydra) - freshwater polyp, ranging in size from 1 to 20 mm. Its body is a stem-leg, with which it attaches to any surfaces in the aquarium: glass, soil, snags, plants, and even snail egg laying. Inside the body of the hydra - the main organ that makes up its essence - the stomach. Why essence? Because her womb is insatiable. long tentacles, crowning the body of the hydra, are in constant motion, capturing numerous small, sometimes invisible to the eye, living creatures from the water, bringing it to the mouth, which ends the body of the hydra.

In addition to the insatiable belly in the hydra, her ability to recover is frightening. Like , she can recreate herself from any piece of her body. For example, hydra can regenerate from cells left after rubbing it through mill gas (such a finely porous mesh). So rubbing it on the walls of the aquarium is useless.

The most common types of hydras in domestic reservoirs and aquariums:

- common hydra(Hydra vulgaris) - the body expands in the direction from the sole to the tentacles, which are twice as long as the body;

- hydra thin(Hydra attennata) - the body is thin, of uniform thickness, the tentacles are slightly longer than the body;

- hydra longstemmed(Hydra oligactis, Pelmatohydra) - the body is in the form of a long stem, and the tentacles exceed the body length by 2-5 times;

- hydra green(Hydra viridissima, Chlorohydra) is a small hydra with short tentacles, whose body color is provided by unicellular chlorella algae living in symbiosis with it (that is, inside it).

Hydra breed by budding (asexual variant) or by fertilization of an egg by a spermatozoon, as a result of which an “egg” is formed in the body of the hydra, which, after the death of an adult, waits in the wings in the ground or moss.

Generally hydra- an amazing creature. And if it were not for the obvious threat on her part to the small inhabitants of the aquarium, she could be admired. So, for example, scientists have been studying hydra for a long time, and new discoveries not only amaze them, but also make an invaluable contribution to the development of new medicines for humans. So, in the body of the hydra, the protein hydramacin-1 was found, which has wide range action against gram-positive and gram-negative pathogenic bacteria.

What does hydra eat?

Hydra hunts for small invertebrates: cyclops, daphnia, oligochaetes, rotifers, trematode larvae. In her bringing death"paws" can also please fish fry or young shrimp. The body and tentacles of the hydra are covered stinging cells, on the surface of which there is a sensitive hair. When it is irritated by a passing victim, a stinging thread is thrown out of the stinging cells, entangling the victim, piercing into it and letting out poison. Maybe hydra sting a snail crawling by or a shrimp swimming past. The ejection of the thread and the launch of the poison occur instantly and take about 3 ms in time. I myself have repeatedly seen how a shrimp that accidentally landed in a hydra colony bounced off like scalded. Numerous "shots" and, accordingly, large doses of poison can adversely affect adult shrimp or snails.

Where does the hydra come from in the aquarium?

There are many ways to bring hydra into an aquarium. With any object of natural origin, immersed in an aquarium, you can host this "infection". You will not even be able to establish the very fact of introducing eggs or microscopic hydras (remember, at the beginning of the article, their size is from 1 mm) with soil, snags, plants, live food, or even milligrams of water in which shrimp, snails or fish were purchased. Even with the apparent absence of hydras in the aquarium, they can be detected by examining any section of driftwood or stone under a microscope.

The impetus for their rapid reproduction, in fact, when hydra become visible to the aquarist, there is an overabundance of organic matter in the aquarium water. Personally, I found them in my aquarium after overfeeding. Then the wall closest to the lamp (I don’t have fluorescent lamps, but a table lamp) was covered with a “carpet” of hydras, appearance belonging to the species "thin hydra".

How to kill a hydra?

Hydra bothers many aquarists, or rather, the inhabitants of their aquariums. On the forum website the theme of "Hydra in the shrimp" has already been brought up three times. Having studied the reviews on the fight against hydra in the vast domestic and foreign Internet, I have collected the most effective (if you know more, supplement) methods for destroying hydras in an aquarium. After reading them, I think everyone will be able to choose the most appropriate method in his situation.

So. Of course, you always want to destroy uninvited guests without harming other inhabitants of the aquarium, primarily shrimp, fish and expensive snails. Therefore, salvation from hydras is mainly sought among biological methods.

Firstly, the hydra also has enemies that eat it. These are some fish: black molly, swordtails, from labyrinths - gourami, cockerels. They feed on hydra and large pond snails. And if the first option is not suitable for a shrimp because of the threat from fish to shrimp, especially young ones, then the option with a snail is very suitable, only you need to take snails from a trusted source, and not from a reservoir in order to avoid introducing another infection into the aquarium.

Interestingly, Wikipedia refers to creatures capable of eating and digesting hydra tissue as turbellarians, which include planaria. Hydras and planarians, like "Tamara and I go together", really often find themselves in the aquarium at the same time. But for planarians to eat hydras, aquarists are silent about such observations, although I have read about this more.

The main diet of hydra is also for cladoceran Anchistropus emarginatus. Although his other relatives - daphnia - hydras themselves are not averse to swallowing.

VIDEO: hydra tries to eat daphnia:

Used to fight the hydra and its love of light. It is noticed that hydra is located closer to the light source, moving to that place with steps from foot to head and from head to foot. Inventive aquarists came up with a peculiar hydra trap. A piece of glass is tightly leaning against the wall of the aquarium, and a light source (lamp or lantern) is directed to that place in the dark. As a result, during the night the hydras move to a glass trap, which is then pulled out of the water and doused with boiling water. This remedy can rather be called control over the number of hydras, since this method does not give complete disposal of hydras.

Poorly tolerated hydra and elevated temperature. The method of heating the water in the aquarium is useful if it is possible to catch all the inhabitants of the aquarium valuable to you and transplant them into another container. The water temperature in the aquarium is brought to 42 ° C and kept for 20-30 minutes, turning off the external filter or removing the filler from the internal filter. Then the water is allowed to cool or diluted with hot settled cold water. After that, the living creatures are returned home. Most plants tolerate this procedure well.

Remove hydra and safe if dosages are observed 3% hydrogen peroxide. However, to achieve the desired effect, a solution of hydrogen peroxide at the rate of 40 ml per 100 liters of water must be infused daily for a week. Shrimps and fish tolerate this procedure well, but plants do not.

Of the radical measures - the use of chemistry. For the destruction of hydra, drugs are used, the active substance of which is fenbendazole: Panakur, Febtal, Flubenol, Flubentazole, Ptero Aquasan Planacid and many others. Such drugs are used in veterinary medicine for the treatment of helminthic invasions in animals, and therefore they should be looked for in pet stores and veterinary pharmacies. However, you should pay attention to the fact that the composition of the drug does not include copper or other active substance in addition to fenbendazole, otherwise the shrimp will not survive such treatment. The preparations are available in powder or in tablets, which must be crushed into powder and try to dissolve as much as possible, you can use a brush, in a separate container with water collected from the aquarium. Fenbendazole dissolves poorly, so the resulting suspension, when poured into the aquarium, will give cloudy water and sediment on the ground and on objects in the aquarium. Undissolved particles of the medicine can eat up shrimp, but this is not scary. After 3 days, it is necessary to change the water by 30-50%. According to aquarists, this method is quite effective against hydras, but snails do not tolerate it well, and in addition, biobalance in the aquarium may be disturbed after therapy.

When applying any of the above methods, it is necessary to pay special attention to the organic purity in the aquarium: do not overfeed the inhabitants, exclude feeding invertebrates with daphnia or brine shrimp, do water changes on time.

Added on 01/05/19: Dear fellow hobbyists, the author of this article did not test the effect of the preparations indicated in the article on shrimp that are sensitive to changes in water parameters (Sulawesi shrimp, Taiwan bee, Tigerbee). Based on this, the proportions indicated in the article, as well as the use of drugs itself, can be detrimental to your shrimp. As soon as the necessary and verified information on the use of the preparations given in the article in aquariums with shrimp Sulawesi, Taiwan bee, Tigerbee is collected, we will definitely make adjustments to the material presented.

P.s. It is a pity that at the moment there are no veterinary clinics that aquarists could contact. Indeed, today every family has pets, and their owners, at least once, could use the services of a veterinary clinic. Imagine a competent veterinarian treating your aquarium pet - it's a pity that these are only dreams!

From this article you will learn everything about the structure of freshwater hydra, its lifestyle, nutrition, reproduction.

The external structure of the hydra

Polyp (which means "many-legged") hydra is a tiny translucent creature that lives in the clear transparent waters of rivers with slow flow, lakes, ponds. This coelenterate animal leads a sedentary or attached lifestyle. The external structure of freshwater hydra is very simple. The body has an almost regular cylindrical shape. At one of its ends is a mouth, which is surrounded by a crown of many long thin tentacles (from five to twelve). At the other end of the body is the sole, with which the animal is able to attach itself to various objects under water. The body length of freshwater hydra is up to 7 mm, but the tentacles can be greatly stretched and reach a length of several centimeters.

Beam symmetry

Let's take a closer look external structure hydras. The table will help to remember their purpose.

The body of the hydra, like many other animals leading an attached lifestyle, is inherent. What is it? If we imagine a hydra and draw an imaginary axis along the body, then the tentacles of the animal will diverge from the axis in all directions, like the rays of the sun.

The structure of the hydra's body is dictated by its lifestyle. It is attached to an underwater object with a sole, hangs down and begins to sway, exploring the surrounding space with the help of tentacles. The animal is hunting. Since the hydra lies in wait for prey that can appear from any direction, the symmetrical radial arrangement of the tentacles is optimal.

intestinal cavity

Let's consider the internal structure of the hydra in more detail. The body of the hydra looks like an oblong bag. Its walls consist of two layers of cells, between which there is an intercellular substance (mesogley). Thus, inside the body there is an intestinal (gastric) cavity. Food enters through the mouth. It is interesting that the hydra, which in this moment does not eat, the mouth is practically absent. Ectoderm cells close and fuse in the same way as on the rest of the body surface. Therefore, every time before eating, the hydra has to break through the mouth again.

The structure of the freshwater hydra allows it to change its place of residence. On the sole of the animal there is a narrow opening - the aboral pore. Through it, liquid and a small bubble of gas can be released from the intestinal cavity. With the help of this mechanism, the hydra is able to detach itself from the substrate and float to the surface of the water. In such a simple way, with the help of currents, it settles in a reservoir.

ectoderm

The internal structure of the hydra is represented by ectoderm and endoderm. The ectoderm is said to form the body of the hydra. If you look at an animal through a microscope, you can see that several types of cells belong to the ectoderm: stinging, intermediate, and epithelial-muscular.

The most numerous group is skin-muscle cells. They are in contact with each other by the sides and form the surface of the body of the animal. Each such cell has a base - a contractile muscle fiber. This mechanism provides the ability to move.

With the contraction of all fibers, the body of the animal contracts, lengthens, and bends. And if the contraction occurred only on one side of the body, then the hydra leans. Thanks to this work of cells, the animal can move in two ways - “tumbling” and “walking”.

Also in the outer layer are star-shaped nerve cells. They have long processes, with the help of which they come into contact with each other, forming a single network - the nerve plexus, braiding the entire body of the hydra. Nerve cells are also connected with skin-muscle cells.

Between the epithelial-muscular cells are groups of small, round-shaped intermediate cells with large nuclei and a small amount of cytoplasm. If the body of the hydra is damaged, then the intermediate cells begin to grow and divide. They can transform into any

stinging cells

The structure of the hydra cells is very interesting, the stinging (nettle) cells with which the entire body of the animal, especially the tentacles, are strewn, deserve special mention. have a complex structure. In addition to the nucleus and cytoplasm, the cell contains a bubble-shaped stinging chamber, inside which is the thinnest stinging thread rolled into a tube.

A sensitive hair comes out of the cell. If the prey or the enemy touches this hair, then there is a sharp straightening of the stinging thread, and it is thrown out. The sharp tip pierces the body of the victim, and poison enters through the channel passing inside the thread, which can kill a small animal.

As a rule, many stinging cells are triggered. Hydra captures prey with tentacles, draws to the mouth and swallows. The poison secreted by stinging cells also serves to protect. More large predators do not touch painfully stinging hydras. The poison of the hydra in its action resembles the poison of the nettle.

Stinging cells can also be divided into several types. Some threads inject poison, others wrap around the victim, and still others stick to it. After triggering, the stinging cell dies, and a new one is formed from the intermediate one.

Endoderm

The structure of the hydra also implies the presence of such a structure as the inner layer of cells, the endoderm. These cells also have muscular contractile fibers. Their main purpose is to digest food. Endoderm cells secrete digestive juice directly into the intestinal cavity. Under its influence, prey is split into particles. Some endoderm cells have long flagella that are constantly in motion. Their role is to pull food particles up to the cells, which in turn release prolegs and capture food.

Digestion continues inside the cell, which is why it is called intracellular. Food is processed in vacuoles, and undigested residues are thrown out through the mouth opening. Respiration and excretion occurs through the entire surface of the body. Consider again cellular structure hydras. The table will help visualize this.

reflexes

The structure of the hydra is such that it is able to feel changes in temperature, chemical composition water, as well as touch and other irritants. Animal nerve cells are capable of being excited. For example, if you touch it with the tip of a needle, then the signal from those who felt the touch nerve cells will be transmitted to the rest, and from nerve cells to epithelial-muscular ones. The skin-muscle cells will react and contract, the hydra will shrink into a ball.

Such a reaction - bright This is a complex phenomenon, consisting of successive stages - the perception of the stimulus, the transmission of excitation and the response. The structure of the hydra is very simple, and therefore the reflexes are uniform.

Regeneration

The cellular structure of the hydra allows this tiny animal to regenerate. As mentioned above, intermediate cells located on the surface of the body can transform into any other type.

With any damage to the body, intermediate cells begin to divide very quickly, grow and replace the missing parts. The wound heals. The Hydra's regenerative abilities are so high that if you cut it in half, one part will grow new tentacles and a mouth, and the other a stem and sole.

asexual reproduction

Hydra can reproduce both asexually and sexually. Under favorable conditions in summer time a small tubercle appears on the body of the animal, the wall protrudes. Over time, the tubercle grows, stretches. Tentacles appear at its end, a mouth erupts.

Thus, a young hydra appears, connected to the mother's organism by a stalk. This process is called budding because it is similar to the development of a new shoot in plants. When a young hydra is ready to live on its own, it buds off. Daughter and mother organisms are attached to the substrate with tentacles and stretch in different directions until they separate.

sexual reproduction

When it starts to get colder and adverse conditions are created, the turn of sexual reproduction comes. In the fall, hydras from intermediate germ cells begin to form, male and female, that is, egg cells and spermatozoa. Hydra egg cells are similar to amoebas. They are large, strewn with pseudopods. Spermatozoa are similar to the protozoan flagella, they are able to swim with the help of a flagellum and leave the body of the hydra.

After the sperm cell enters the egg cell, their nuclei fuse and fertilization occurs. The pseudopods of the fertilized egg cell retract, it rounds, and the shell becomes thicker. An egg is formed.

All hydras in the fall, with the onset of cold weather, die. The mother organism disintegrates, but the egg remains alive and hibernates. In the spring, it begins to actively divide, the cells are arranged in two layers. With the onset warm weather a small hydra breaks through the shell of the egg and begins an independent life.