This article will familiarize the reader with the structure of protozoa, namely, focuses on the structure of the contractile vacuole, which performs an excretory (and not only) function, tells about the significance of protozoa and describes how they exist in the environment.
Contractile vacuole. The concept
Vacuole (from the French. Vacuole, from the Latin word vacuus - empty), spherical-shaped small cavities in plant and animal cells or unicellular organisms. Contractile vacuoles are primarily common among the simplest organisms that live in freshwater, for example, among protists, such as amoeba protea and ciliates, which got its original name because of the shape of the body, similar to the shape of the sole of the shoe. In addition to the listed protozoa, identical structures were also found in the cells of various freshwater sponges, which belong to the Badiagov family.
The structure of the contractile vacuole. Her features
The contractile vacuole is a membrane organoid that ejects excess fluid from the cytoplasm. The localization and structure of this apparatus varies among different microorganisms. From a complex of vesicular or tubular vacuoles, called spongii, the fluid enters the contractile vacuole. Thanks to the continuous operation of this system, a stable cell volume is maintained. The protozoa have contractile vacuoles, which are an apparatus that regulates the osmotic pressure, and also serves to isolate decay products from the body. The body of protozoa consists of only one cell, which, in turn, carries out all the necessary vital functions. Representatives of this sub kingdom, such as the ciliates, slippers, common amoeba, and other unicellular organisms possess all the properties of an independent organism.
The role of protozoa
The cell performs all vital functions: excretion, respiration, irritability, movement, reproduction, metabolism. Protozoa are ubiquitous. The largest number of species lives in marine and fresh waters, many inhabit moist soil, can infect plants, live in the bodies of multicellular animals and humans. In nature, protozoa perform a sanitary role, they also participate in the circulation of substances, are food for many animals.
Contractile vacuole in common amoeba
Common amoeba - a representative of the class of the root root, does not, unlike other representatives of the constant body shape. Movement is carried out using pseudopods. Now we will understand what function the contractile vacuole performs in the amoeba. This is the regulation of the osmotic pressure level inside her cell. In amoeba protea, it can form in any part of the cell. Through the outer membrane, water from the environment enters osmotically. The concentration of solutes in the amoeba cell is higher than in the environment. Thus, a pressure difference is created inside the protozoan cell and beyond. The function of the contractile vacuole in an amoeba is a kind of pumping apparatus that removes excess water from the cell of a simple organism. Amoeba protea can throw out the accumulated liquid into the environment in any part of the body surface.
This function of the contractile vacuole is acceptable for the simplest organisms living in freshwater. In parasitic and marine forms that live in an environment where the osmotic pressure is higher than in fresh water, these primitive devices are reduced very rarely or are usually absent. Around the contractile vacuole in the simplest organisms, mitochondria are concentrated, delivering energy to perform osmotic work.
In addition to osmoregulatory, it performs the function of respiration in life, as as a result of osmosis, the incoming water delivers oxygen dissolved in it. What other function does the contractile vacuole perform? It also performs an excretory function, namely, together with water, metabolic products are released into their environment.
Respiration, secretion, osmoregulation in the ciliates
The body of the protozoa is covered with a dense shell, which has a constant shape. It feeds on both bacteria and algae, including some protozoa. The organism of the ciliates has a more complex structure than that of the amoeba. Two contractile vacuoles are located in the shoe cage in front and behind. In this apparatus, a reservoir and several small tubules are distinguishable. Contractile vacuoles are constantly located, due to this structure (from microtubules), at a constant place in the cell.
The main function of the contractile vacuole in the life of this representative of the protozoa is osmoregulation, it also removes excess water from the cell, which penetrates the cell due to osmosis. First, the lead channels swell, then the water from them is pumped into a special tank. The reservoir is reduced, separated from the supply channels, through the pores water is discharged out. In the infusorian cell there are two contractile vacuoles, which, in turn, act in antiphase. Due to the operation of two such devices, a continuous process is ensured. In addition, water is continuously circulating due to the activity of contractile vacuoles. They are compressed alternately, and the frequency of contractions depends on the ambient temperature.
So, at room temperature (+18 - +20 degrees Celsius), the frequency of contraction of vacuoles is, according to some sources, 10-15 seconds. And considering that the shoe’s natural habitat is any fresh water reservoirs with standing water and the presence of decomposing organic substances in it, the temperature of this medium varies by several degrees depending on the time of year and, therefore, the frequency of contractions can reach 20-25 seconds. In an hour, the contractile vacuole of the simplest organism is able to throw out water in an amount from the cell. commensurate with its size. They accumulate nutrients, undigested food residues, end products of metabolism, oxygen and nitrogen can also be detected.
Wastewater treatment protozoa
The influence of protozoa on the cycle of substances in nature is of great importance. In reservoirs, due to the discharge of wastewater, bacteria multiply in large numbers. As a result, various simple organisms appear that use these bacteria as food and thus contribute to the natural cleansing of water bodies.
Conclusion
Despite the simple structure of these unicellular organisms, the body of which consists of one cell, but performs the functions of a whole organism, surprisingly adapted to the environment. This can be observed even on the example of the structure of the contractile vacuole. To date, the great importance of protozoa in nature and their participation in the cycle of substances has already been proven.