In ancient mythology, the hydra was a terrible monster with several heads that quickly grew if they were chopped off. Modern representatives of the intestinal cavity are much smaller and are completely safe for humans. But they got their name precisely because of their good ability to regenerate. They are able to completely restore the body from its microscopic part. How are these amazing animals arranged?
Habitat
Hydra is a representative of the type of Intestinal, which includes about 10 thousand modern species. This is a small polyp, the size of which is about 2 cm, which lives by attaching itself to a support. As a substrate, he prefers algae or the bottom of fresh water bodies in which there is no current.
Body symmetry
The body of the hydra has a cylindrical shape. Its lower part is called the sole. At the opposite end of the body are tentacles.
Hydra is an organism that has radiation symmetry. If an imaginary axis is drawn from the mouth opening to the sole, then the tentacles will diverge like rays.
Intestinal cavity
These multicellular animals got the name of the type due to the presence of the intestinal cavity inside the cylindrical body. Food enters through the mouth opening. Here its digestion also takes place. The walls of the body of the intestinal cavity consist 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 the intestinal cavity is called ectoderm. Consider which hydra cells form it. First of all, it is cutaneous and muscular. Due to their contractions, the hydra body is able to contract and lean to the sides. Between them are nerve cells that have a stellate shape - neurons. Connecting with their processes, they form a plexus. Thanks to this structure, the whole organism is interconnected with the environment.
What hydra cells are capable of dividing? First of all, intermediate. In terms of their functions, they can be compared with the structures of the educational tissue of plants. These are non-specialized formations, during the division of which cells of all other types are formed. Their presence determines a high level of polyp regeneration - the ability to restore lost or damaged parts of the body.
Hydra Business Card
Hydra is a polyp that, like all intestinal cavities, has stinging cells. Since their presence is characteristic only for this type of animal, stinging cells are the "calling card" of polyps and jellyfish.
Its components are a capsule with a sensitive hair and a spirally twisted thread. It contains substances that paralyze the victim. When unicellular, fish fry or small mollusks touch a sensitive hair, the thread unwinds and sticks into the victim’s body. In this case, the cell itself dies. She can no longer fulfill her function. The division of hydra cells , in particular intermediate cells, ensures the continuous appearance of new stinging cells.
Endoderm
In the inner layer of the body, digestive and glandular cells predominate . Thanks to their action, organic substances are broken down. They have flagella, with the help of which a constant flow of water is created and particles of food appear inside specialized vacuoles. In them, the process of digesting food is completed.
Features of life processes
Despite the fact that hydra is an organism that leads an attached lifestyle, it is capable of movement. It resembles an acrobat in a circus. First, the hydra leans to the side, then, as it were, “stands on its head”, resting on the substrate with tentacles. Then again it lowers to the sole. Hydra can glide on a flat surface.
The breathing process is carried out through the integument. For this, the hydra uses oxygen dissolved in water.
Nerve cells are able to perceive irritation from the environment, convert it into a nerve impulse and conduct it to all parts of the body. These are the first multicellular animals capable of performing simple reflexes. If you touch the polyp with a sharp needle, his whole body will shrink. This simple protective reflex is the body's response to irritation.
Which hydra cells are capable of dividing can also be considered by the example of the multiplication of polyps. During the summer, hydra propagates vegetatively by budding. First, a slight protrusion forms on her body. Then this kidney grows, with time it separates from the mother's body and begins to exist independently. In the fall, due to lower water temperatures and lack of nutrients, budding stops. Hydra goes on to sexual reproduction. Among them, there are dioecious individuals and hermaphrodites - organisms that are capable of forming both male and female germ cells. Hydra is characterized by external fertilization. Male germ cells sperm go into the water and connect with the eggs, which remain connected to the mother's body. As a result, zygotes are formed, covered with dense shells. After that, adults die. The eggs sink to the bottom, where they hibernate. With the onset of the warm season, young polyps come out of them.
The circulatory system is absent. Isolation occurs through the cells of the outer layer, and from the inner, they first enter the intestinal cavity, from which they exit through the oral opening.
Intensive division of hydra determines their ability to regenerate. Empirically, it was proved that the polyp is able to fully recover from any part of the body: tentacles, soles, a collection of cells, as well as from suspension.
A freshwater polyp (hydra) is an organism whose study of regeneration was the beginning of a new science - experimental zoology. This animal was first described in its scientific works by the inventor of the microscope Anthony van Levenguk, and Karl Linney gave a systematic name to this species. A story is connected with him about the exploits of Hercules. According to ancient mythology, he defeated the many-headed Lernean hydra. The scientist had in mind her, since she also had the ability to regenerate. In place of the severed head, a new one immediately grew. Our hero buried it in the ground, performing one of twelve feats.
Some species are able to form symbiosis with unicellular green algae, zoochlorella. It is proved that such a polyp can exist in the world for several months without food.
Hydra is a typical representative of the type of Intestinal, a characteristic feature of which is the presence of two layers of the body, specialized cells and the cavity in which the digestion process occurs.