Structure and reproduction of infusoria-shoes

Infusoria-shoes belong to the class of the most highly organized protozoan microorganisms. They live in stagnant shallow water bodies. If we compare them with other groups of protozoa, the infusorians have a more complex structure.

Features of microorganisms

The infusoria-shoe class is considered one of the most highly organized. They are large enough: their size can reach 0,5 mm. The name they received is due to their shape, in appearance resembling the sole of the shoes.

Infusoria-shoes are always in motion. At the same time they swim bluntly forward. The speed of their movement is great - about 2.5 mm per second. This means that they overcome the distance, 5-10 times the length of their own body. In this case, the trajectory of their movement is very specific: they not only move straight, but also rotate along the longitudinal axis to the right.

Dilute these microorganisms in small aquariums. For this it is enough to fill ordinary meadow hay with water from a pond. In such a tincture, a mass of protozoan microorganisms is formed. As a rule, an infusoria-shoe can be found under the microscope. The photos of this microorganism make it possible to understand why he was given such a name.

Providing traffic

The body of these microorganisms is elongated and looks similar to the bottom of the boat shoes. The anterior end is narrow, the widest part is the posterior third. The body is evenly covered with cilia, which are arranged in rows. On the body of these microorganisms there are about 10 thousand. All of them work synchronously - they make wavy movements. Infusoria move due to these well-coordinated movements.

Each cilium at room temperature performs about 30 paddle movements per second. The oscillatory wave starts from the front of the body and goes backwards. Simultaneously, along the body of this microorganism, 2-3 waves of contraction occur. All cilia are a single functional whole - their actions are coordinated among themselves, this has long been confirmed by the science of biology. Infusoria-shoe can move in different directions and at different rates. It can react to changes in the external environment, changing the direction of motion.

External Features

One of the sides of the trunk of infusorians is conditionally called a peritoneum. On this part, a deep trough goes inside. It is a pericarp hole and is called a pincer. In its back part is the mouth and throat. On the walls of the peristome cilia are longer. This is a special hunting machine, which pushes food into the mouth of the infusoria-shoe.

The outer covering of the microorganism is a cell membrane, which is a thin elastic membrane. It is she who provides a permanent form of the body, which differs from other groups of the simplest infusoria-shoe. Grade 7 in schools is engaged in the study of these microorganisms. It is at this time that the children learn that each cilium has a rather complex structure.

Structure

With a detailed examination of the infusoria-shoe, you can see that her body is clearly divided into two layers. The outer cover is lighter. It is called ectoplasm. The inner layer is darker, it differs in granular structure. They call it endoplasma. The surface layer of ectoplasm is the membrane that is responsible for the fact that there is always one shape of the infusoria-shoe. The photo made under an electronic microscope, allows to make out a dense shell, which is called a pellicle.

In the outer layer between the cilia are perpendicular sticks. They are called trichocysts and perform a protective function. When stimulated, the trichocysts are sharply ejected outward, forming thin long strands. With their help, a predator is struck, trying to attack the shoe. In place of the trichocysts used, new ones grow.

Features of food

The infusoria-shoe class is considered one of the most voracious. The process of feeding at them stops only during breeding. The mouth opening of these microorganisms is always open. Therefore, the flow of food particles that enter the mouth is practically not interrupted.

During the movement, the cilia create a constant current of water around the body of the infusorian. With it, food gets through the oral opening into the pharynx and accumulates on its bottom. Together with an insignificant amount of water, the food particles leave the pharyngeal base and pass into the cytoplasm. This forms the digestive vacuole. Separating from the pharynx, she makes a certain way along the body of the infusorian for an hour.

First, the vacuole moves towards the posterior part of the body. After that, after describing a small arc, starts moving towards the front edge. Then the vacuole begins to move along the periphery of the body.

The processing of food in the body of these microorganisms in a certain place is being completed. It is there that undigested residues come out. This distinguishes among themselves such microorganisms as cilius-shoe, euglena green, amoeba. The first of them has a precisely defined place in which the selection process takes place. This is the so-called abdominal wall. But, for example, in an amoeba, the process of defecation can take place anywhere.

Process of food processing

During the movement in the vacuole, digestive enzymes constantly flow, and the digested food is already absorbed into the cytoplasm. Several stages in the digestion process are singled out by biology. Infusoria-shoe after the formation of a special vacuole begins to produce special enzymes.

If in the first moments the contents of the digestive organ does not differ from the environment, then after a while it changes. The environment in the vacuole becomes acidic - the digestion process begins. After that, the picture changes. Within the vacuoles, the medium becomes slightly alkaline. These conditions are necessary for the continuation of digestion. The ratio of the duration of the acidic and alkaline phases can vary depending on the nature of the food. But as a rule, the first part is not more than ¼ of the entire period of digestion of food. The process of absorbing food stops at the time when the infusoria-shoe multiplies.

Excretory system

In the body of the infusoria-shoe are not only digestive vacuoles. There are also special excretory organs. They are called contractile vacuoles. All infusorians can detect two such excretory organs: one is in the first, and the second - in the last third of the trunk. Each of them has a special structure.

Vacuoles consist of a central reservoir and suitable leading channels. The cycle of their work begins with filling the liquid with radially located channels. Their contents are poured into the tank, and from it through a special time it comes out.

At this time, the channels again begin to fill with liquid. In this case, the anterior and posterior vacuoles are contracted in turn. The intensity of their work depends on the conditions of the external environment. At room temperature, this cycle takes 10-15 seconds.

Functional features

Like other simple microorganisms, the infusoria-shoe has a cell nucleus. But in structure it is noticeably different. The nuclear apparatus is noteworthy in that the infusorians have two different types of nuclei. This is one of the main differences between them and other microorganisms. In the center of the body (in the region of the peristome) is a large nucleus. It usually is egg-shaped. It is also called macronucleus. Close to it is another core, which is several times smaller than its size. It is called micronucleus. But the difference is not only in size, their structure also differs markedly.

In macronucleus, the number of chromosomes is several hundred times greater than in the micronucleus. Therefore, the amount of chromosomal substance (chromatin) in them varies considerably. By the way, when studying the reproduction of infusoria-shoes, you can find out that both nuclei participate in this process.

Only one microorganism is enough to produce the offspring. But under certain conditions, the conjugation process begins. This is the name of sexual reproduction of infusorians-shoes. It should be noted that this process is quite long.

Asexual reproduction

The method of reproduction of the infusoria-shoe was studied experimentally. When transplanting a single individual into a separate aquarium in a day, two or four microorganisms can already be found there. The period of active swimming and feeding is completed by the fact that the body of the infusoria extends in length. Precisely in the middle there is a deepening constriction, which serves as a place for the separation of one microorganism into two. The whole process of division under favorable conditions lasts for about an hour.

The asexual reproduction of the infusoria-shoe goes as follows: even before the body appears a constriction, the nuclear apparatus begins to double. The first to share micronuclei, then the turn comes to macronuclei. In this case, the process of dividing a small nucleus resembles mitosis, and the large one - amitosis.

During this process there is a noticeable deep restructuring of the body. Two pharynxes are formed, two oral openings and two peristomas. Also the basal nuclei of the cilia are covered. Due to this, the bodies of the educated individuals are tightly covered.

Sexual reproduction

In some cases, the conjugation process can be observed. This sexual reproduction of infusoria-shoes. It occurs as follows: two microorganisms close together, applying to each other abdominal walls. In this form they continue to swim for about 12 hours. Then they diverge. In the body of infusoria, a large nucleus disintegrates and gradually dissolves in the cytoplasm. Micronuclei first divide, but part of the nuclei formed in this case almost immediately disintegrates. In each infusoria involved in the process, there are 2 nuclei. One of them remains in place, and the other moves to the partner and merges with the core, which already had an infusoria-shoe.

The form of reproduction that passes this way provides cross fertilization. The sexual nuclei of cells merge . As a result, a special structure is formed in the infusoria, called the Sincarion. This is a complex nucleus that is divided one or more times and turns into macronuclei. After the restoration of the normal nuclear apparatus of infusoria, the process of asexual reproduction continues.

It is important to understand that such a method of reproduction of the infusoria-shoe does not lead to an increase in the population, but to an increase in the hereditary variety.