Hydra is a genus of freshwater sessile coelenterates of the class cnidarian

In ancient mythology, the Hydra was a terrible monster with multiple heads, which quickly grow if they are cut off. Modern representatives of coelenterates is much smaller and for a person is quite safe. But the name they received thanks to a good ability to regenerate. They are able to fully restore the body of its microscopic parts. How is these amazing animals?

Habitat

Hydra is representative of the type of the Coelenterates, which includes about 10 thousand modern species. It is a small polyp, the size of which is about 2 cm, which lives attached to the support. The substrate he prefers seaweed or the bottom of freshwater reservoirs, in which there is no current.

The symmetry of the body

The body of the Hydra has a cylindrical shape. Its lower part is called the sole. On the opposite end of the body are tentacles.

Hydra is an organism that has radial symmetry. If from the mouth to the sole to hold the imaginary axis, then the tentacles will diverge like rays.

Intestinal cavity

The name of the type, these multicellular animals was due to the presence of a cylindrical body inside the intestinal cavity. It through the mouth receives food. Here is her digestion. The body wall of coelenterates consists of two layers of the body: external and internal. Between them is a layer of intercellular substance, which has the form of a thin plate.

Ectoderm

The Outer layer of the body of coelenterates is called the ectoderm. Consider the cells of a Hydra form it. First of all, this skin-muscle. Thanks to their cuts, the body of the Hydra is able to shrink and lean to the side. Between them there are nerve cells having star-shaped neurons. Connecting their processes, they form a plexus. Due to this structure is the relationship of the organism with the environment.

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The cells of a Hydra are able to divide? First of all intermediates. Of functions they can be compared with the structures of the educational plant tissue. This specialized education, in the division which formed the cells of all other types. Their presence results in a high level of regeneration of polyps - the ability to restore lost or damaged body parts.

"Business card" Hydra

Hydra is a polyp, which, like all coelenterates, has stinging cells. Because their presence is characteristic only for this type of animals, the stinging cells are "hallmark" of polyps and jellyfish.

Components of a capsule with sensitive hairs and a spiral thread. It contains a substance that paralyzes the victim. When unicellular, the fry of fishes, small mollusks touch sensitive thread, the thread unwinds and bites into the victim's body. However, the cell dies. She no longer can perform its function. Cell division Hydra, in particular, the staging provides a continuous emergence of new stinging cells.

Endoderm

In the inner layer of the body is dominated by the digestive and glandular cells. Thanks to their action are broken down organic matter. They have flagella, which create a constant flow of water and food particles to be inside specialized vacuoles. In them the process of digestion is completed.

Vital processes

Despite the fact that the Hydra is an organism that lead an attached mode of life, she is able to travel. It looks like an acrobat in the circus. First, the Hydra leans to the side, then as it "stands on its head", based on the substrate the tentacles. Then again, it descends to the sole. On a flat surface the Hydra can slide.

The Process of respiration is via the skin. To do this, the Hydra uses the oxygen dissolved in the water.

Nerve cells are able to perceive irritation from the environment, convert it to a nerve impulse and carried out in all parts of the body. This is the first multicellular animals capable of simple reflexes. If you touch the polyp with a sharp needle, his body will shrink. This simple protective reflex is the response the body's response to irritation.

The cells of a Hydra are able to divide, can be considered on the example of reproduction of polyps. During the summer of Hydra vegetatively propagated using budding. First, her body formed a small protrusion. Then this kidney grows and eventually separates from the mother's body and begins an independent existence. In the fall, because of lower water temperature and lack of nutrients, the budding ceases. Hydra switches to sexual reproduction. Among them are individuals of dioecious and hermaphrodite organisms which are capable of forming both male and female sex cells. HY characterized by external fertilization. Male sex cells the sperm out into the water and combine with eggs, which remain connected with the parentbody. The result is the formation of a zygote, covered with thick shells. After that the adults die. The eggs sink to the bottom, where they overwinter. With the onset of warm time of the year have young polyps.

The Circulatory system is missing. The selection occurs through the cells of the outer layer and from the inner first arrive in the intestinal cavity, from which through the mouth come out.

Intense division Hydra determines their ability to regenerate. Experimentally it was proved that the polyp is able to completely recover from any body part: tentacles of the sole, of a set of cells and from the slurry.

The Freshwater polyp (Hydra) is an organism, the study of regeneration which was the beginning of a new science of experimental Zoology. This animal was first described in their scientific works, inventor of the microscope Anthony van Leeuwenhoek and systematic name of the species gave Carl Linnaeus. It is associated with the story of the labors of Hercules. According to ancient mythology, he defeated the multi-headed Lernaean Hydra. And it meant the scientist, because she also had the ability to regenerate. In place of the severed head immediately grew a new one. Its our hero buried in the ground, having made one of the twelve labors.

Some species capable of forming symbiosis with unicellular green algae zoochlorellae. It is shown that the polyp may be several months for the world to exist without food.

Hydra is a typical representative of a type of Cnidarian, which is characterized by the presence of two layers of the body, specialized cells and cavities in which the process of digestion.