What is hydra? Hemopoies of the class of hydroids

From this article you will learn what hydra is. This representative of coelenterates is distinguished by more complex processes of vital activity in comparison with the first multicellular organisms - sponges. With what features of the structure is it related? Let's figure it out together.

What is Hydra in Mythology

This biological species got its name because of similar features with the mythological hero - the Lernaean hydra. According to legend, it was a snake-like monster with poisonous breath. The body of the hydra had several heads. It could not be defeated by anyone - several new ones immediately grew up on the spot of the felled head.

The Lerna hydra in Lerna Lake, where she guarded the entrance to the underground kingdom of Hades, was inhabited. And only Hercules could chop off her immortal head. Then he buried it in the ground and filled it with a heavy stone. This is the second feat of Hercules from the twelve.

Hydra: Biology

A high ability to restore lost parts of the body or regeneration is also characteristic of freshwater hydra. This animal is a representative type of coelenterates. So what is hydra? It is a single freshwater polyp, which leads an exclusively attached lifestyle.

General characteristics of coelenterates

Like all coelenterates, hydra is an aquatic creature. She prefers small puddles, lakes or rivers with a small current that allow them to attach to plants or benthic objects.

The classes of coelenterates are represented by hydroids, jellyfish and coral polyps. All of their representatives are characterized by radial, or radial symmetry. This feature of the structure is associated with a sedentary lifestyle. At the same time, in the center of the animal's body, it is possible to put an imaginary point, from which to draw rays in all directions.

All coelenterates are multicellular animals, but they do not form tissues. Their body is represented by two layers of specialized cells. Inside there is an intestinal cavity in which digestion of food takes place. Different classes of coelenterates differ in a way of life:

• Hydroids are attached to the substrate with the help of soles and are single.
• Coral polyps are also immobile, but they form colonies, in which there are hundreds of thousands of individuals.
• Jellyfish actively swim in the water column. At the same time, their bell is shortened and water is pushed out with force. This motion is called reactive.

Body structure

The body of the freshwater hydra looks like a stalk. Its base is called the sole. With its help, an animal is attached to underwater objects. At the opposite end of the body is a mouth opening, surrounded by tentacles. It leads to the intestinal cavity.

The body walls of hydra consist of two layers of cells. The outer is called the ectoderm. It consists of skin-muscular, nervous, intermediate and stinging cells. The inner layer, or endoderm, is formed by their other types - digestive and glandular. Between layers of the body is a layer of intercellular substance, which has the appearance of a plate.

Types of cells and life processes

Since no tissues or organs are formed in the body of the hydra, all physiological processes are carried out with the help of specialized cells. So, epithelial-muscular provide movement. Yes, despite the attached lifestyle, the hydroids are capable of moving. At the same time, the epithelial-muscular cells of one side of the body are contracted first, the animal "bends down", rises on the tentacles and again sinks to the sole. This movement is called walking.

Between the epithelial-muscular nerve cells are star-shaped. With their help, the animal perceives irritations from the environment and responds to them in a certain way. For example, if you touch the hydra with a needle, it contracts.

The ectoderm also contains intermediate cells. They are capable of surprising transformations. If necessary, cells of any type are formed from them. They are responsible for the high level of regeneration of these animals. It is known that the hydra can completely recover from 1/200 of its part or the mushy state.

From the intermediate cells are formed and sex. This happens with the onset of autumn. In this case, the ovules and spermatozoa merge, forming a zygote, and the mother's organism dies. In the spring of these young individuals develop. In summer the hydra multiplies by budding - on its body a small tubercle is formed, which increases in size, acquiring the features of an adult organism. As it grows, it splits off and goes on to independent existence.

The endoderm of coelenterates contains digestive cells. In them, there is a splitting of nutrients. A glandular cells release into the intestinal cavity enzymes, under the influence of which the food breaks up into pieces. Thus, the hydra is characterized by two types of digestion. They are called intracellular and cavitary.

Streptococcal cells

It is impossible to answer the question, what is a hydra, if one does not get acquainted with the peculiarities of stinging cells. In nature, they are found only in coelenterates. With their help, protection, defeat and retention of production are carried out. Therefore, their main quantity is located on the tentacles.

The cage consists of a capsule with a spirally twisted thread. On the surface of this structure is a sensitive hair. It is he who is affected by the prey passing by. As a result, the thread unwinds and bites into the victim's body, paralyzing it.

According to the type of nutrition, coelenterates, hydra in particular, are heterotrophic predators. They feed on small aquatic invertebrates. For example, daphnia, cyclops, oligochaetes, tulips, fleas, mosquito larvae and fish fry.

Significance of coelenterates

The meaning of hydra in nature is primarily that it plays the role of a biological filter. It purifies water of suspended particles that it uses for food. This is an important link in the supply chains of fresh water bodies. Hydrides feed on some of the branchy crayfish, turbellarians and fish, whose size exceeds 4 cm. Malka hydra itself affects the poison of stinging cells.

But scientists on the question of what a hydra, for sure answer that this is a known object of laboratory research. On these coelenterates study the features of the processes of regeneration, the physiology of the lower multicellular, budding.

So, the freshwater hydra is a representative of the class of the Hydroid type of the Gut. This multicellular two-layered animal with radiation symmetry, whose body consists of several types of specialized cells.