The infusoria-shoe lives in small stagnant reservoirs. This single-celled animal, 0.5 mm long, has a spindle-shaped body, vaguely resembling a shoe. Ciliates are constantly in motion, swimming with a blunt end forward. The speed of movement of this animal reaches 2.5 mm per second. On the surface of the body they have organelles of movement - cilia. There are two nuclei in the cell: a large nucleus is responsible for nutrition, respiration, movement, metabolism; the small nucleus is involved in the sexual process.

The structure of the shoe infusoria

The organism of ciliates is more complicated. The thin elastic shell that covers the outside of the ciliate maintains a constant shape of its body. This is also facilitated by well-developed supporting fibrils, which are located in the cytoplasm layer adjacent to the shell. About 15,000 oscillating cilia are located on the surface of the body of the ciliate. At the base of each cilium lies a basal body. The movement of each eyelash consists of a sharp stroke in one direction and a slower, smoother return to its original position. The cilia vibrate about 30 times per second and, like oars, push the infusoria forward. The wave-like movement of the cilia is coordinated. When the ciliate-shoe swims, it slowly rotates around the longitudinal axis of the body.

Life processes

Food

Slipper and some other free-living ciliates feed on bacteria and algae.

The reaction of ciliates-shoes to food

Thin elastic shell, ( cell membrane ) covering the ciliate from the outside, retains a constant body shape. About 15 thousand cilia are located on the surface of the body. On the body there is a recess - a cellular mouth, which passes into a cellular pharynx. At the bottom of the pharynx, food enters the digestive vacuole. In the digestive vacuole, food is digested within an hour, first with an acidic and then with an alkaline reaction. Digestive vacuoles move in the body of the ciliates by the current of the cytoplasm. Undigested residues are thrown out at the posterior end of the body through a special structure - powder, located behind the mouth opening.

Breath

Breathing occurs through the integument of the body. Oxygen enters the cytoplasm through the entire surface of the body and oxidizes complex organic substances, as a result of which they turn into water, carbon dioxide and some other compounds. At the same time, energy is released, which is necessary for the life of the animal. Carbon dioxide is removed through the entire surface of the body during respiration.

Selection

In the body of ciliates-shoes there are two contractile vacuoles, which are located at the anterior and posterior ends of the body. They collect water with dissolved substances formed during the oxidation of complex organic matter. Having reached the limit value, the contractile vacuoles approach the surface of the body, and their contents pour out. In freshwater unicellular animals, excess water is removed through contractile vacuoles, which constantly enters their body from the environment.

Irritability

Ciliates-shoes gather to clusters of bacteria in response to the action of the substances they secrete, but swim away from such an irritant as table salt.

Irritability is a property of all living organisms to respond to the actions of stimuli - light, heat, moisture, chemicals, mechanical influences. Due to irritability, unicellular animals avoid adverse conditions, find food, individuals of their year.

reproduction

asexual

Ciliates usually reproduce asexually by dividing in two. The nuclei are divided into two parts, and each new ciliate contains one large and one small nucleus. Each of the two daughters receives part of the organelles, while the others are formed anew.

Reproduction of ciliates-shoes

sexual

With a lack of food or a change in temperature, ciliates go to sexual reproduction, and then can turn into a cyst.

During the sexual process, an increase in the number of individuals does not occur. Two ciliates are temporarily connected to each other. At the point of contact, the shell dissolves, and a connecting bridge is formed between the animals. The large nucleus of each ciliate disappears. The small nucleus divides twice. In each ciliate, four daughter nuclei are formed. Three of them are destroyed, and the fourth is divided again. As a result, two cores remain in each. Nuclear exchange occurs along the cytoplasmic bridge, and there it merges with the remaining nucleus. The newly formed nuclei form a large and small nucleus, and the ciliates diverge. This sexual process is called conjugation. It lasts about 12 hours. The sexual process leads to renewal, exchange between individuals and redistribution of hereditary (genetic) material, which increases the viability of organisms.

Life cycle of ciliates-shoes

Type Ciliates structure photo protozoan animals cell nucleus drawing vacuole organelles

Latin name Ciliophora or Infusoria

Type of infusoria- highly organized unicellular organisms with the most complex system of organelles. They are characterized by the presence of motor organelles - cilia, nuclear dualism and a special form of the sexual process - conjugation.

general characteristics

Type of ciliates unites a large number of species (over 6000) of the most highly organized protozoa.
They are characterized by the presence of cilia, which are usually present in large numbers. Cilia serve as organelles for movement and can stick together to form more complex organelles. Some sucking ciliates have cilia only in the early stages of their life cycle. All ciliates are characterized by nuclear dualism, that is, duality. This means that they have at least two cores that differ both in size and function. One of the nuclei, much larger, is called the macronucleus, and the second, small, is called the micronucleus. Some types of ciliates have several micro- and macronuclei. The micronucleus serves as a sexual, or generative, nucleus that plays a major role in the sexual process. Macronucleus is a somatic, or vegetative, nucleus that regulates all life processes, except for the sexual process.
Asexual reproduction of ciliates occurs by transverse division. The sexual process in ciliates proceeds in a peculiar way, in the form of conjugation, which is not observed in the simplest other classes. Conjugation consists in the temporary approach of two individuals and the mutual exchange of parts of their micronuclei.
Ciliates are inhabitants of mainly fresh water bodies, but are also found in brackish water and in the seas, some species have adapted to existence in moist soil. Among ciliates there are many parasites (about 1000 species) of invertebrates and vertebrates.
The class is divided into two classes:

• Ciliary ciliates (Ciliata);
• Sucking ciliates (Suctoria).

Infusoria class ciliary

Latin name Ciliatas

A - common shoe (Paramecium caudatum); 1- cilia; 2 - macronucleus; 3- micronucleus; 4 - peristome; 5 - mouth; 6 - pharynx; 7 - the formation of the digestive v, akuoln; 8 - digestive vacuoles; 9 - defecation; 10 - reservoir of contractile vacuum! > Whether; 11, 12 - adductor canals of contractile vacuoles; 13 - trichocysts; B - belly of Stylonichia mytilus; 1 - adoral membranella; 2, 3, 4 and 5 groups of frontal, abdominal, anal and caudal cirrhi; 6 - row of marginal cirrhosis; 7 - dorsal scales tpnkn; 8 - edge of the peristome; 9 - ireoral cilia; 10 - wavy membrane; 11 - peristome; 12 - adductor canal of the contractile vacuole; 13 - reservoir of the contractile vacuole; 14 - micronucleus; 15 - macronucleus; 16 - digestive vacuole; B - creeping stilonchia; 1 - adoral membranella; 2, 3, 4 and 5 - frontal, abdominal, anal and XBOCI ovy tsprra; 6 - marginal cirres; 7 - dorsal setae; 8 - leading channels; 9 - C (* reducing / vacuole.

Ciliates have a rather diverse body shape. However, in many species, due to their adaptation to a floating lifestyle, the body shape is elongated and streamlined. An example is the common slipper (Paramecium caudatum) (Fig. 2, A). The sizes are also different, some species reach quite large sizes, up to 2 mm in length (Spirostomum).
The body is covered with a thin but strong shell - pellicle, which has a rather complex structure. The pellicle is flexible and elastic, therefore it does not serve as an obstacle to some change in the body shape. Many ciliates can bend it, squeeze between various objects. In the large infusoria "trumpeter" (Stentor) (pn \ 43, A), the body is elongated in the form of a gramophone pipe, but it can be strongly compressed and take on a spherical shape.
(/P * ciliates are the organelles of the movement of ciliates. They are very thin and short numerous plasma hairs. The ultra-fine structure of cilia and flagella, studied using an * electron microscope, showed their striking similarity.
In some ciliates, cilia evenly cover the entire body. For example, a shoe has about 10,000-15,000 cilia arranged in regular rows. In others, the cilia are concentrated in certain places on the body. "The fluctuations of the cilia are essentially rowing movements, consisting of a backward blow, in which the cilium moves quickly in one shaft, and a return to its original position, when the cilium slowly doubles forward, smoothly describing a semicircle.At room temperature, the ridges make about 30 strokes per second.The movements of the cilia occur in a coordinated manner, resulting in the correct wave-like vibrations of all rows of cilia.The shoe moves at a speed of up to 2.5 mm / sec, i.e. That is, in a second it passes a distance 10-15 times the length of its body.

Rice. 3. The structure of the pellicle and the ciliary apparatus
A - the structure of the body surface of Paramecium nephridiatum; 1 - pairs of sitting cilia; 2 - neuroplasmic reticulum; 3 - pellicle ribs; 4 - trichocysts; 5 - opening of the trichocyst - B ciliary apparatus of the peristome of stylonichia (Stylonichia mytilus) from the ventral side; The same in cross section; 1 - preoral cilia; 2 - oral cilia; 3 - preoral wavy membrane; 4 - internal wavy membrane; 5 - oral wavy membrane; 6 - membranella; 7 - dorsal setae.

In addition to simple cilia, they have larger formations, usually surrounding the mouth cavity or located on other parts of the body. These are the so-called membranella (Fig. 2, B). Each membranella is a row of cilia that stick together into one plate, often triangular in shape (Fig. 3, B), and if a longer row of cilia sticks together, a wavy / membrane, or membrane, is formed. Such membranes are present in many in the mouth recess or in the pharynx. The structure of the ciliary apparatus and the location of various ciliary formations serve as important systematic features.
The cytoplasm of ciliaries is clearly divided into an outer, lighter and denser layer - ectoplasm and a more liquid and granular inner layer - endoplasm (Fig. 2).

Rice. 4. Trichocysts of a common shoe (Paramecium caudatum): A - discarded trichocysts of shoes killed with purple ink; B - the front end of the shoe (cut at high magnification); 1 - macronucleus; 2 - cilia; 3 - trichocysts; B - individual trichocysts.

Ectoplasm has a complex structure, forming a large number of organelles. It highlights on its surface the previously mentioned elastic pellicle. At the shoe, the pellicle has a complex sculpture: it is formed by regular hexagons, in the center of which cilia are placed. Apparently, such a structure increases the strength of the outer shell. Ectoplasm also owns cilia and membranella along with basal bodies. In the ectoplasm of many ciliates, the so-called trichocysts are located in large numbers (Fig. 4). These are elongated rod-shaped bodies that strongly refract light. When irritated, trichocysts are ejected through special tubules outward in the form of the thinnest stream of liquid, which solidifies in water as a thin elastic thread. Trichocysts - organelles of attack and defense. Predatory with the help of trichocysts paralyze prey; "Peaceful" - protect themselves from the attack of predators. By origin, trichocysts are a modification of motor organelles and are formed from basal bodies.
In ectoplasm, with appropriate processing, one can detect a network of the thinnest fibers lying near the basal bodies and trichocysts (Fig. 3, A). It is believed that these fibers - neurofans - conduct irritation and determine the coordinated work of the ciliary apparatus. However, in many cases, such fibrils are of reference value. It was stated above that many of them can change the shape of the body. This is due to the fact that special contractile threads, or myonemes, are located in the ectoplasm. Thus, in the trumpeter (Stentor) and some others, the system of contractile myonemes consists of many longitudinally arranged fibers running along the body and lining the perioral depression (Fig. 5 A). The myoneme system in Caloscolex from the ruminant stomach, described by Prof. V. A. Dogel (Fig. 5, B). The sessile ciliates of the suvoek have a rather complex arranged stalk, inside of which myonemes also pass. When suvoeks are irritated, their stalk coils into a spiral (Fig. 45).
A certain shape of the body, sometimes quite bizarre, is due to the presence of dense skeletal formations in the ectoplasm. Most often, this is a whole system of supporting fibrils (Fig. 5, C).

The digestive organelles of ciliates begin with a mouth, or cytostome, which is an opening in the pellicle. In many, the mouth is placed at the bottom of a special depression - the perioral cavity, or peristome (Fig. 26, A). In many that feed on small organisms (bacteria), the peristome is surrounded by a spirally arranged corolla of membranella (razor-ciliated and round-ciliated). An undulating membrane may be located in the peristome (Fig. 26 and 3, B).

The flickering movements of cilia and membranella cause currents of water, with which food particles (bacteria, etc.) are brought to the mouth. Many carnivores do not have a peristome, and they swallow food with a strongly expanding mouth (Fig. 40, C).
The mouth leads to the "pharynx", or cytopharynx, which is a short canal, sometimes also lined with cilia. At the inner edge of the pharynx, a bubble is formed, consisting of a drop of liquid secreted by the endoplasm, into which food particles accumulating at the bottom of the pharynx fall. This is how the digestive vacuole is formed (Fig. 2, A).
In a shoe with an abundance of food, a new digestive vacuole is formed approximately every minute. Food-containing vacuoles break away from the pharynx and move in the endoplasm of the ciliates, making a certain path. So, in a shoe, each digestive vacuole first describes a small circle in the back half of the body, and then a large circle, reaching the front end of the body. During movement in the vacuole, food is digested and the digested food is absorbed into the endoplasm. The endoplasm secretes enzymes into the digestive vacuoles.

Rice. 6. Predatory ciliates that feed on other ciliates
A - Bursaria truncatella; B - Dileptus unser; B - Spathidium spatula; D - Didinium, devouring the slipper.

It has been established that on different stages digestion, the acidity of the contents of the vacuole is different. Initially, the contents of the vacuole are acidic, then alkaline.

Vacuoles containing undigested food residues approach the surface of the ectoplasm. In many ciliates, at a certain place in the body, closer to the posterior end, there is a special opening in the pellicle - the cytoproct, through which defecation occurs (Fig. 2, A). The process of defecation occurs much less frequently than the process of formation of digestive vacuoles (after 7-10 minutes), since before defecation several vacuoles with undigested food residues merge into one. The entire process of digestion in a shoe, from the formation of vacuoles to defecation, lasts from 1 to 3 hours, depending on the temperature.

As mentioned above, among ciliates there are many predators that feed on others (Fig. 6). For example, the large predatory Bursaria swallows slippers and others, driving them down the throat with the movement of the membranes. Other predators swallow differently. Their mouth is highly extensible, and they swallow and draw in rather large ciliates. Some carnivores can eat ciliates that are much larger than their own size. So, relatively small Didinium (Fig. 40, D) attack shoes, kill them with a special proboscis, then gradually draw in and digest.
Excretory organelles are represented by one, two or more contractile vacuoles located in certain parts of the body (Fig. 2). Contractile vacuoles often have a rather complex structure (Fig. 7). In addition to the vacuole itself, periodically contracting (the state of systole) and expanding (diastole), leading channels located in the endoplasm lead to it. Due to this, the released substances enter the contractile vacuole from various parts ciliate bodies. An excretory duct leads from the vacuole to the pellicle, opening with a special opening outward (Fig. 7).

Rice. 7. The structure of contractile vacuoles
A - contractile vacuoles and adductor canals of Paramecium caudatum; B - contractile vacuoles of Campanella umbellaria in diastole (left) and systole (right); C - diagram of the structure of the contractile vacuole of Cycloposthium; the vacuole opens to the outside with a permanent canal surrounded by special myonemes-terminators (2); 2 - pellicle; D - contractile vacuole of Paramecium trichium with a convoluted excretory canal (2).

If there are two vacuoles (for example, in a shoe), they contract alternately. At 16°C, each vacuole contracts after 20-25 seconds (near the shoe).

Ciliates, like other protozoa, are able to respond to a variety of external stimuli. Unlike many flagellated ciliates, they do not have light-sensitive organelles. The role of sensitive organelles is played mainly by cilia and membranella. In some, the cilia retain their motor function; in others, such as Stilonychia, the dorsal cilia serve only as tactile organelles.
The reaction to irritation is expressed in slowing down or accelerating, as well as in changing the direction of movement (shoes), in folding the peristome and compressing the body (stentors, suvoys), in reducing the stalk
(suvoyki), etc. Ciliates are very sensitive to the slightest touch of foreign objects. They are also very sensitive to changes in the chemical composition of the environment, and different substances act on them differently, causing either a positive or negative reaction. The ability to react differently to different chemicals great importance in the life of ciliates when finding the food they need and the most favorable conditions for existence. For breathing, oniums need a sufficient amount of oxygen dissolved in water. They are,
like other protozoa, they breathe the entire surface of the body. Therefore, ciliates react positively to an air bubble entering a drop of water, gathering near it. Ciliates react positively or negatively to changes in the temperature of the environment, and each species is characterized by adaptability to a certain
it consists of one or more macronuclei of various shapes (Figs. 2 and 43) and one or more micronuclei. In details, the structure of the nuclear apparatus varies greatly. Thus, the common shoe (Paramecium caudatum) has one large macronucleus and one micronucleus, which fits into the recess of the macronucleus. Another species of the same genus, P. aurelia, has two micronuclei. The macronucleus of the horseshoe has a horseshoe-shaped macronucleus, while the trumpeter, in addition to a very elongated bead-like macronucleus, has several micronuclei (Fig. 43). The differentiation of the nuclear apparatus into the vegetative nucleus - the macronucleus and into the sexual, or generative, nucleus - the micronucleus is characteristic of all ciliary ciliates.
The micronucleus differs from the macronucleus not only in size, but also in the number of chromosomes. While the micronucleus has a diploid set of chromosomes, the macronucleus is polyploid, i.e., the set of chromosomes is repeated many times in it. Thus, in the slipper Paramecium caudatum, the macronucleus is 80-ploid (according to other sources, 160-ploid), and in the closely related species P. aurelia, it is 1000-ploid. In some, the degree of ploidy can reach up to 10-15 thousand.
Thus, ciliary ciliates, in comparison with other protozoa, have a very complex structure. It gets more complicated in two ways. We have seen that ciliates have big number various organelles, often forming entire systems, for example, a system of digestive, excretory organelles, etc. On the other hand, ciliates are characterized by multiplication, or polymerization, of many organelles. Undoubtedly, cilia with basal bodies correspond in origin to the flagellar apparatus of the flagellates. But compared with the polymerization of locomotor organelles in polyflagellates, in ciliates, polymerization goes much further. Developing a complex system an organelle consisting of a huge number of cilia, partly turning into membranella, cirri, etc. At the same time, the complexity of the organization is expressed in the coordinated functioning of the entire motor apparatus. For ciliates, the multiplication of the number of nuclei is also characteristic. They have at least two cores. However, unlike polyflagellates, this process is further complicated by the differentiation of the nuclei.

Suctoria sucking ciliates

Rice. Sucking ciliates
A - sucking Dendrocometes paradoxus; 1 - caught prey; 2 - branched tentacles; 3 - contractile vacuole; 4- macronucleus; B - sucking tentacle of Dendrocometes; 1 - pellicle; 2- tubules; 3- cytoplasm; B. Sphaerophrya, sucking several cilia. Infusoria shoe belongs to the type of ciliates (Infusoria), which has over 7 thousand species. Compared with other groups of protozoa, ciliates have the most complex structure, being the pinnacle of the organization of unicellular animals. The infusoria-shoe lives in almost all freshwater reservoirs and is an integral part of the "dust". They can be easily detected under a microscope among silt particles and the remains of rotting plants taken from an aquarium.

Among the simplest ciliates, shoes are rather large organisms, the sizes of which usually range from 0.1 to 0.3 mm. The ciliate shoe got its name due to the shape of its body, reminiscent of a lady's shoe.

It maintains a constant body shape due to the fact that the outer layer of its cytoplasm is dense. The entire body of the ciliate is covered with longitudinal rows of numerous small cilia that perform undulating movements. With their help, the shoe floats with the blunt end forward. A groove with longer cilia runs from the anterior end to the middle of the body. At the end of the groove there is a mouth opening leading to the pharynx. Infusoria feed mainly on bacteria, driving them to the mouth with cilia. The mouth opening is always open. Small food particles penetrate through the mouth into the pharynx and accumulate at its bottom, after which the food lump, together with a small amount of liquid, comes off the pharynx, forming a digestive vacuole in the cytoplasm. The latter makes a complex path in the body of the ciliates, during which the digestion of food is carried out.

In addition to bacteria, ciliates feed on yeast and algae. When feeding them with algae, direct influence should be avoided. sunlight, since the oxygen released by freshly swallowed algae can break the ciliates. It should be borne in mind that ciliates can filter and swallow any particles, regardless of their nutritional value. Therefore, the presence of foreign suspended particles in the vessel with ciliates should be avoided, since if the ciliates overflow their oral opening with foreign suspension, the ciliates may die.

Infusoria slipper mobile enough. The speed of its movement at room temperature is 2.0 - 2.5 mm/sec. This is a high speed: in 1 second the shoe covers a distance exceeding the length of its body by 10-15 times. This circumstance must be taken into account when feeding small, inactive larvae of some spawning fish, which, even with a high concentration of ciliates, can remain hungry.

For breeding ciliates at home, it is better to use a pure culture, after making sure it is clean under a microscope. In the absence of a pure culture, you can get it yourself. To do this, a few drops of a suspension of silt with plant residues taken from the bottom of the aquarium are placed on the glass, to which a drop of milk or a grain of salt is added. Next to it from the side of the world, a drop of fresh, settled water is dripped. Both drops are connected by a water bridge using a sharpened match. The shoe rushes towards fresh water and light at a faster speed than all other microorganisms. Shoes reproduce very quickly: to reach their maximum concentration of 40 thousand ind./cm from a single individual, under optimal cultivation conditions, less than a month is needed.

For breeding shoes, all-glass vessels with a volume of 3 liters or more are usually used. Good results are achieved at room temperature, but the peak of reproduction of ciliates is observed at 22 - 26°C. In the first days of cultivation, a weak purge is desirable, but at the same time, sediment should not rise from the bottom of the jar. In the presence of a purge, the ciliates are located at the bottom of the jar, and with a lack of oxygen, they rush to the surface of the water. This property is usually used to concentrate ciliates before feeding them to their larvae.

As food for ciliates, you can use hay infusion, dried peels of banana, pumpkin, melon, yellow swede, sliced ​​​​carrots, fish feed pellets, milk, dried lettuce, liver pieces, yeast, algae, i.e. those substances that are either directly consumed by shoes (yeast, algae), or are a substrate for the development of bacteria.

When using hay, take 10 g of it and place it in 1 liter of water, boil for 20 minutes, then filter and dilute with an equal amount or two-thirds of settled water. During boiling, all microorganisms die, but bacterial spores remain. After 2-3 days, hay sticks develop from spores, serving as food for ciliates. As needed, the infusion is added to the culture. The infusion is stored in a cool place for a month.

The shoe can be bred on dried lettuce leaves or liver pieces placed in a gauze bag.
The peel of ripe, intact bananas, melons, swedes, pumpkins is dried and stored in a dry place. Before entering the culture, take a piece 1-3 cm in size, rinse and pour 1 liter of water. Hydrolytic yeast is added at the rate of 1 g per 100 liters. Most in a simple way is the cultivation of shoes on skimmed, boiled or condensed (without sugar) milk: it is introduced into the culture 1 - 2 drops per 1 liter) once a week. Shoes use lactic acid bacteria.

When using the above feeds, it is important not to overdose on nutrition. Otherwise, rapidly multiplying bacteria will leave the ciliates without oxygen. When ciliates are grown on bacteria, they have positive phototaxis, i.e. yearn for the light. You can breed ciliates on stagedesmus and chlorella algae. Good results can be achieved when cultivating ciliates with weak blowing, when 1 granule of carp compound feed is added per 1 liter of algae. Ciliates fed with algae have negative phototaxis: they tend to darkness. This property can be used when feeding shade-loving fish larvae. Use the culture of ciliates, as a rule, no longer than 20 days. To maintain the culture at all times, it is charged in two cans at weekly intervals, with each can being recharged every two weeks. For long-term storage of ciliates culture, it is placed in a refrigerator and stored at a temperature of + 3°- + 10°C.

The collection of ciliates is carried out in places of their highest concentration using a rubber hose. Concentration of ciliates can be done by carefully introducing a saline solution into the culture, which, sinking to the bottom of the jar, causes the ciliates to concentrate at the surface. An easier way to collect ciliates is to introduce milk into the culture while turning off the purge. After 2 hours, the ciliates are concentrated at the surface on the illuminated side of the jar.

Particularly good results can be achieved if the culture is placed in a cylinder, adding milk and salt to it. In this case, cotton wool is placed on the surface of the liquid, and then fresh water is carefully added to the cotton wool, while the upper part of the cylinder is illuminated. After half an hour, most of the shoes are moved into fresh water, and this water with ciliates is transferred to a vessel with fish larvae. To feed many characins and a number of other fish, the larvae of which cannot stand the presence of bacteria, infusoria can withstand a day or two in clean water. During this time, the shoes eat all the bacteria and thus disinfect the water.

For a constant supply of ciliates to the aquarium with fish larvae, a jar of ciliates is placed above the aquarium and from it, through a hose with a clamp, water with ciliates drops into the aquarium with larvae. You can pour water with ciliates not with a hose, but with a moistened linen thread. Feeding by ciliates of the larvae of most fish is usually carried out only during the first two or three days with the gradual addition (on the second day) of larger food organisms.

There are many types of ciliates. Most of them live in water, mostly in stagnant water. The most common infusoria in fresh water is the slipper. She lives in a variety of water bodies.

The structure of the shoe ciliates is slightly different from the proteus amoeba and green euglena. For example, due to the presence of a shell, ciliates do not form pseudopods.

Infusoria slipper is larger than amoeba and euglena. The length of her body reaches 0.3 - 0.5 mm. If you look against the light into a glass vessel with water in which shoes are floating, then they can be seen with the naked eye in the form of tiny white spots. They move so fast that they can be difficult to see even with a microscope at low magnification. The shoes move so fast because their body is covered with a multitude of the thinnest protoplasmic formations - cilia. The cilia oscillate and scoop up the water like oars. With the help of cilia, the ciliates of the shoes located around the mouth are also fed, they move in one direction, urging food.

When studying the structure of the ciliates of the shoe, it is clear that its body is covered with the thinnest shell, so it has a more or less constant shape. Due to the presence of the shell of the ciliates, the shoe does not form pseudopods. The body of the shoe infusoria consists of protoplasm, in which there are two nuclei: large and small.

Like other invertebrate animals, the ciliate shoe has the ability to respond to external stimuli. If you place a shoe in a drop of water on a glass slide and shine it brightly on one side, you will notice that they will quickly gather on the illuminated part of the glass, while common amoebas gather on the darkened part of the glass. You can place two drops of water with shoes next to each other on a glass slide, and then use a glass rod to make a water bridge between the drops. If you add a crystal of salt to one of them, then the shoes will swim into the drop where there is no salt.

Infusoria slippers in water gather around food. The ciliate shoe feeds on microscopic organisms. The movement of the shoes is also affected by the temperature of the water. If you place them in a test tube with water, the temperature of which at one end is 30 - 35 °, and at the other - about 15 °, then the shoes will gather in the most favorable temperature zone for them - about 25 - 27 °.

Like amoeba and euglena, shoe ciliates breathe the entire surface of the body. In the body of the ciliates of the shoe there are two contractile vacuoles. Harmful substances formed in the protoplasm enter them through the tubules. These vacuoles either expand or contract. Contracting, they free the body of the ciliate shoe from excess water and harmful substances.

Reproduction of the infusoria of the shoe is carried out like an amoeba, that is, by cell division. Like amoeba, ciliates form cysts under adverse conditions.

Type Ciliates, or Ciliary, are the most complexly organized protozoa. On the surface of the body they have organelles of movement - cilia. There are two nuclei in the ciliate cell: a large nucleus is responsible for nutrition, respiration, movement, and metabolism; the small nucleus is involved in the sexual process.

Features of the structure and vital activity of ciliates are considered on the example of ciliates-shoes.

Habitat, structure and locomotion. In the same reservoirs where the amoeba proteus and green euglena live, the infusoria shoe is also found (Fig. 30). This unicellular animal, 0.5 mm long, has a spindle-shaped body, vaguely resembling a shoe. Ciliates-shoes are always in motion, swimming with a blunt end forward. The speed of movement of this animal reaches 2.5 mm per second.

Rice. 30. The structure of ciliates-shoes: 1 - cilia; 2 - contractile vacuole; 3 - cytoplasm; 4 - large core; 5 - small core; b - cell membrane; 7 - cell mouth; 8 - cell pharynx; 9 - digestive vacuole; 10 - powder

The organism of ciliates is more complicated than that of amoeba and euglena. The thin elastic shell that covers the outside of the ciliate maintains a constant shape of its body. This also contributes to the burial of the developed supporting fibrils, which are located in the layer of cytoplasm adjacent to the shell. About 15 thousand oscillating cilia are located on the surface of the body of the ciliate. At the base of each cilium lies a basal body. The movement of each eyelash consists of a sharp stroke in one direction and a slower, smoother return to its original position. The cilia vibrate about 30 times per second and, like oars, push the ciliate forward, while the wave-like movement of the cilia is coordinated. When the ciliate-shoe swims, it slowly rotates around the longitudinal axis of the body.

Under the elastic membrane, special formations are scattered all over the body - trichocysts (from the Greek trichos - “hair” and cystis - “bubble”). These are short "sticks" located in one layer perpendicular to the surface of the body. In case of danger, trichocysts are thrown out with force, turning into thin long elastic threads that hit a predator that attacks the shoe. In place of the used trichocysts, new ones arise over time.

Food. On the body of the ciliate there is a recess - a cellular mouth, which passes into the cellular pharynx. Around the mouth are thicker and longer cilia. They drive bacteria into the throat along with the flow of water - the main food of the shoe. At the bottom of the pharynx, food enters the digestive vacuole. Digestive vacuoles move in the body of the ciliates by the current of the cytoplasm. In the vacuole, food is digested, the digested products enter the cytoplasm and are used for life. The undigested residues remaining in the digestive vacuole are thrown out at the posterior end of the body through a special structure - powder.

Slipper ciliates locate their prey by sensing the presence of chemicals that are released by clusters of bacteria.

Selection. In the body of ciliates-shoes there are two contractile vacuoles, which are located at the anterior and posterior ends of the body. Each vacuole consists of a central reservoir and 5-7 channels directed to these reservoirs. First, the channels are filled with liquid, then it enters the central reservoir, and then the liquid is expelled out. The entire contraction cycle of these vacuoles takes place once in 10-20 seconds. Contractile vacuoles bring out harmful substances that are formed in the body, and excess water.

Breath. Like other free-living unicellular animals, ciliates breathe through the integument of the body.

Reproduction. Sexual process. Ciliates-shoes usually reproduce asexually - by dividing in two (Fig. 31, A). However, unlike flagellates, ciliates divide across the body. The nuclei are divided into two parts, and each new ciliate contains one large and one small nucleus. Each of the two daughter ciliates receives part of the organelles (for example, contractile vacuoles), while the others are formed anew. Infusoria-shoes are divided once or twice a day.

Rice. 31. Asexual reproduction (A) and sexual process (B) in ciliates-shoes

During the sexual process, an increase in the number of individuals does not occur. Two ciliates are temporarily connected to each other (Fig. 31, B). At the point of contact, the membrane dissolves, and a connecting bridge from the cytoplasm is formed between the animals. The large nucleus of each ciliate disappears. The small nucleus divides twice, and four daughter nuclei are formed in each ciliate. Three of them are destroyed, and the fourth is divided again. As a result, two nuclei remain in each ciliate. One of these nuclei of each of the two individuals passes through the cytoplasmic bridge into another ciliate (that is, an exchange of nuclei occurs) and merges with the remaining nucleus there. Then, in each ciliate, large and small nuclei are formed from this newly formed nucleus, and the ciliates diverge. This sexual process is called conjugation. It lasts about 12 hours.

The sexual process leads to renewal, exchange between individuals and redistribution of hereditary (genetic) material, which increases the viability of organisms.

Rice. 32. Variety of ciliates: 1 - bursaria; 2 - stentor; 3 - stilonychia; 4 - suvoyka

The bursaria has one large and long sausage-shaped core, about 30 small cores. Most ciliates actively swim, but some of them, such as stylonichia, move along the bottom of the reservoir, along aquatic plants, as if walking on special elongated cilia located on the ventral side of the body . Other ciliates, such as suvoys, are attached to the bottom or to plants with long stems, which can contract due to special contractile fibers. Many suvoyki form colonies. These ciliates feed mainly on bacteria. Sucking ciliates also lead a sedentary, motionless lifestyle. They don't have eyelashes. They are equipped with sucking tentacles in the form of thin contractile tubes that serve to catch prey (mainly other protozoa) and suck out the contents from it. Protozoa that touch the tentacles, such as flagellates, instantly stick to them. And then the contents of the victim are sucked in, as if pumped along the tentacle into the sucking infusoria.

Rice. 33. Protozoa from the stomach of ungulates

Some ciliates live in the intestines of large herbivorous ungulates (Fig. 33). In cows, sheep, goats, antelopes, and deer, ciliates inhabit the anterior sections of the stomach in large numbers. These ciliates feed on bacteria, starch grains, fungi, particles of plant tissues. Larger ciliates devour smaller ones. In other parts of the stomach of herbivores, ciliates are digested. Thus, these ciliates benefit those animals in whose stomachs they live. Infusoria infection occurs at the time of group feeding or watering.

Lab #1

1. Topic. The structure and movement of ciliates-shoes. Target. To study the features of the structure and movement of ciliates-shoes.
2. Equipment: microscope, tripod magnifier, glass slide and coverslip, pipette, cotton wool, culture of infusoria-shoes in a test tube.

Progress

1. Establish whether ciliates-shoes are visible to the naked eye in a test tube.
2. Place a drop of water with infusoria-shoes from a test tube on a glass slide. Consider with a magnifying glass the shape of the body, the external structure, the difference between the front of the body and the back, the way of movement. Count the number of ciliates in a drop of water.
3. Place two drops of water with ciliates on a glass slide, connect them with a water "bridge". Put a crystal of salt on the edge of one drop. Explain what is happening.
4. In a drop of water with ciliates, put two or three cotton fibers (to slow down the movement of ciliates). Cover carefully with a cover slip.
5. Place the slide under the microscope. Consider first at low and then at high magnification of the microscope what is happening inside the body of the ciliate.
6. Sketch the external and internal structure of the ciliates-shoes, using the high magnification of the microscope. Make the necessary notation.
7. Based on observations, list the signs characteristic of ciliates as representatives of protozoa.

Ciliates are complexly organized protozoa. They have two nuclei in the cell: a large and a small one. They reproduce asexually and sexually. Sexual reproduction promotes renewal, exchange between individuals and redistribution of hereditary (genetic) material, which increases the vitality of ciliates.

Lesson learned exercises

1. Why is the ciliate shoe so named?
2. What signs prove more complex organization ciliates-shoes compared with amoeba proteus and euglena green?
3. How does the structure of the ciliates-shoes, which is more complex than that of other protozoa, manifest itself in the processes of nutrition and excretion?
4. What are the features of the reproduction process of ciliates-shoes?
5. Why is the sexual process important biologically in the life of ciliates-shoes?