Shell amoeba, the structure of which we will consider in our article, have a number of features that significantly distinguish them from other representatives of unicellular animals. What is special about these amazing organisms?
Shell amoeba: distinctive features
Let's start with the classification of these animals. They are representatives of the sub-kingdom Unicellular, belonging to the Sarcodidae order. Their body has an unstable shape, since it is devoid of a compacted parietal layer. These cells move with the help of pseudopods - temporary protrusions of the cytoplasm. The cell has a typical amoeba structure. It consists of a membrane, cytoplasm and organelles: nucleus, mitochondria, contractile and digestive vacuoles.
Features of the amoeba shell
Most of the body of this species of amoeba is in the shell. This structure is 50 to 150 µm in size and has a round or pear shape. Through the opening, which is called the mouth, testate amoebae release pseudopods out. This is necessary for their movement. Shells can be formed by pseudochitin or organic matter.
For some, they are composed of a substancewhich is in the environment. The process of formation of such shells occurs in several stages. First, the amoeba, with the help of pseudopods, begins to draw grains of sand, fragments of diatom shells, or other solid particles into the cell. Then they stick together with the help of the cytoplasm and stand out. Anatomically, the testate amoeba cell can be divided into three parts. At the top in its cytoplasm are the nucleus and various types of inclusions - reserve nutrients. In the middle are digestive and contractile vacuoles. And closer to the mouth, the cytoplasm is devoid of both organelles and inclusions. Pseudopods are formed from it.
Relationship between structure and habitat
Test amoebae are widely distributed in fresh and s alt water bodies, silt, well-moistened soil areas, plant surfaces, marsh mosses. Their habitat affects certain structural features. For example, the testate amoeba difflugia, which is a typical inhabitant of fresh water, has one mouth. In a few inhabitants of the seas, the shell is pierced through with calcareous needles, so the pseudopods come out of a large number of holes.
Interesting research
Among freshwater inhabitants there are a number of amoebas that prefer to live only in heavily polluted water. Other species die under such conditions. This is also proved by numerous laboratory experiments. Imagine that several species were placed in moist soil at once.testate amoebae. Further, this environment is artificially polluted with oil. In a few days, the species diversity will begin to decrease significantly. Some testate amoebae begin to turn black and change shape.
Physiology of amoebas
Shell amoebas are characterized by a number of features of the course of physiological processes. The reproduction of their cells is carried out by dividing in two, like other representatives of the sub-kingdom. However, in connection with the presence of the shell, there are a number of differences. So, first, a new shell begins to form around the protruding part of the amoeba, and only then the division itself occurs. At first, the daughter organisms still remain interconnected by a cytoplasmic bridge. Next, he laces up. As a result, the daughter individuals separate and move on to independent existence.
For some species, the method of cell reproduction is multiple division. In this case, the crushing process takes place inside the shell. As a result, bare cells appear outside. They form the shell themselves in the course of their life.
Move amoebas with pseudopods. These irregular protrusions of the cytoplasm are also called pseudopodia. To move, the amoeba stretches forward the pseudopod, which is held by the support, and then pulls the whole body towards it. In nature, this type of movement is also characteristic of blood leukocytes and phagocytic cells, which is why it is called "amoeboid".
Feeding of amoebas occurs by capturing its particles with pseudopodia andsubsequent digestion in specialized vacuoles. Gas exchange occurs through the surface apparatus of the cell. The regulation of osmotic pressure is carried out by contractile vacuoles, with the help of which excess water with s alts dissolved in it is removed.
With the onset of adverse conditions testate amoebae fall into a state of cysts. Their shell thickens, and the intensity of metabolic processes is significantly reduced. When the conditions of existence change, cells return to normal functioning.
Shell amoeba: meaning in nature
These are important organisms in the ecosystem. Shell amoebae, together with other unicellular organisms, are an integral part of it. These organisms are a link in the food chain, an indicator of the degree of purity of a fresh water body. The importance of testate amoebae in the process of rock formation is invaluable. Freshwater and marine protozoa have created limestone, chalk and other sedimentary rocks as a result of their life activity.
In nature, a species of sarcode is also known, which is very dangerous for humans. The killer amoeba literally feeds on the human brain. At the moment, 23 cases of human infection with this organism have been recorded. This type of unicellular is an inhabitant of fresh water. Inside a person, it penetrates through the nasal cavity, continuing its path in the canal of the olfactory nerve to the brain. As it moves, it destroys all the tissues that serve as an obstacle to it. The person first experiencessevere headaches, chills caused by fever. Then such signs of brain destruction as fever and hallucinations begin, which inevitably leads to death.
So, representatives of the order Shell amoeba are unicellular animals belonging to the Sarcode class. Their cells have an unstable body shape and pseudopods as organelles of movement. Outside the membrane, this type of amoeba forms its own shell.
