The importance of protozoa for human health. Practical meaning of protozoa
Protozoa are a source of food for other animals. In the seas and in fresh waters protozoa, primarily ciliates and flagellates, serve as food for small multicellular animals. Worms, mollusks, small crustaceans, as well as the fry of many fish feed primarily on single-celled organisms; Without protozoa, their existence would be impossible. These multicellular animals, in turn, feed on larger animals, and primarily on growing fish fry. It's clear what great value have the simplest in the life of nature and in national economy.
The largest animal that has ever lived on Earth, the blue whale, feeds on very small crustaceans that inhabit the oceans. Other toothless whales also feed on them. And these crustaceans, in turn, feed on single-celled animals. So it turns out that, ultimately, the existence of whales depends on single-celled animals and plants.
Protozoa are participants in the formation of rocks. Examining a crushed piece of ordinary writing chalk under a microscope, you can see that it consists mainly of small shells of some animals. Many calcareous rocks of the Volga region, the Urals, Crimea, and the Caucasus consist of the same microscopic shells. Each such shell once contained the body of a simple animal - a foraminifera, which lived in ancient times on the bottom of seas and oceans.
And even now, a significant part of the ocean floor is covered with silt consisting of foraminifera shells. Many limestones consist almost entirely of such shells. Limestones have long been of great practical importance as construction material. For example, gigantic ancient structures - the Egyptian pyramids - were built from them.
2. Signs of animal organisms. Characteristics of the kingdom Animals (Zoa). Organization of animals of the type Cnidaria. Peculiarities of biology of representatives of the classes Hydrozoa, Scyphozoa and Coral polyps(Anthozoa). Biological and practical significance of coelenterates.
3. Type Flatworms(Plathelminthes). Dismemberment of the body. Structure of organ systems. Representatives of the classes Ciliated (Turbellaria), Flukes (Trematoda), Tapeworms(Cestoda). Features of life activity and development in connection with lifestyle. Development cycles of species using the example of planaria, liver fluke, and bovine tapeworm.
body leaf-shaped or ribbon-shaped, flattened in the dorsoventral direction;
Skin-muscular the sac consists of skin epithelium
Leah, who lost cellular structure(tegument), under co‑
which contains three layers smooth muscles(circular, longitudinal and diagonal);
absence of body cavity. The space between the internal
These organs are filled with parenchyma cells, which perform supporting, excretory and storage functions.
bilateral symmetry;
three-layer, those. development of organ systems from ectoderm, endoderm and mesoderm;
Digestive system represented by the foregut of ectodermal origin (mouth, pharynx, esophagus) and the midgut of endodermal origin
niya, closed blindly. The hindgut and anus are absent. Digestion and absorption of food occurs in the intestines nutrients. Undigested residues
food ki are expelled through the mouth. ^ In tapeworms digestive system absent. They feed on the entire surface of the body with the help of microtrichia;
Excretory system protonephridial type. It is represented by stellate-shaped terminal cells and branching tubules extending from them. Channel‑
cells start from terminal cells; they contain bundles of oscillating cilia (ciliary flame). Terminal cells have slit-like openings through which dis- products enter the lumen from the parenchyma.
simulation. Flickering flame provides advancement
fluid in the tubules. The tubules merge with each other, forming two lateral canals that open outwards with excretory pores. Protonephridia remove pro-
dissimilation products and regulate osmotic pressure;
Nervous system scalene-nodal type (orthogon). Represented by a peripharyngeal nerve ring connecting the suprapharyngeal and subpharyngeal ganglion
glia, and the longitudinal nerve trunks extending from it
lami, of which the lateral ones are the most developed. Nervous
They are connected by commissures. Of the sense organs, the or-
the senses of touch and chemical sense;
Reproductive system well developed. The vast majority of flatworms are hermaphrodite
You. Cross fertilization.
Lack of circulatory system
The phylum Flatworms include three classes: Eyelash worms (Turbellaria), Flukes ( Trematoda) and Tapeworms ( Cestoda). Representatives of the classes Flukes and Tapeworms are of medical importance.
^ 110. Class Flukes. Class characteristics. Representatives of medical significance. Prevalence in the Republic of Belarus.
Class Flukes (Trematoda). Trematodes (or flukes) - helminths small size(from 2 to 80 mm) with a flat leaf-shaped body, devoid of articulation. The sexually mature stage of flukes is called Marita. Marita has two suckers, one of which surrounds the oral opening, and the second, abdominal, serves as an attachment organ.
^ Covers of the body. The body wall is made up of a skin-muscular sac, consisting of a tegument (outer covering) fused with the underlying muscles. The tegument is formed from a layer of cells that have merged with each other, so that a total weight protoplasm (syncytium). External part tegument consists of anucleate cytoplasm containing big number mitochondria; deep inner part The tegument contains nuclei. Under the tegument there is a basement membrane, behind which there are smooth muscles, consisting of circular, diagonal and longitudinal muscle fibers.
^ Reproductive system. Most flukes are hermaphrodites. Blood flukes are dioecious.
Male reproductive system consists of a pair of branching or compact testes, two vas deferens, merging into the ejaculatory canal, which
lies on the surface of the copulatory organ (cirrus).
^ Female reproductive system is arranged in a complex manner. The ovary (unpaired), vitelline, spermatheca open into the ootype, where fertilization and the final formation of fertilized eggs take place. Nutrient material for eggs comes from the vitellaria. This also includes the secretions of special glands - Melisa corpuscles. From the ootype, eggs move to the uterus, where
promotes their maturation and is expelled through the genital opening. The egg has characteristic features: its shape is oval, at one pole there is a cap through which the larva emerges.
In some flukes, fertilization occurs in the spermatic receptacle. Insemination is usually cross-breeding. Self-insemination is less common. Flukes are very prolific. Within a week, one individual produces about 1 million eggs.
Life cycle complex, with a change of hosts and several generations of larval stages. All species of this class are biohelminths. The final host is vertebrates and humans, the intermediate, obligatory host is mollusks. Some trematodes, in addition, have a second intermediate host, which can be lower vertebrates and representatives various groups invertebrates. Characteristic feature The life cycle is the reproduction of larval stages through parthenogenesis.
The sexually mature form, marita, lays eggs that are carried outside. For further development the egg should fall into the water. The first larva emerges from the egg - miracidium(It has oval shape, ciliated cover, 2 pigment eyes at the anterior end of the body and protonephridia, in the posterior part of the body of the miracidium there are germ cells that give rise to the next generation of larval forms). Miracidium floats in the water and actively penetrates the body of the mollusk. In the liver the mollusk
as the miracidium turns into a sac-like sporocyst, within which germ cells are preserved. Then, from the germ cell of the sporocyst, the next stage of larvae develops parthenogenetically - redia(has an elongated body, pharynx, intestinal rudiments, nervous and excretory systems and also contains germ cells). In the body of the redia, the next generation of larvae is parthenogenetically formed from the germ cells - cercariae(have a body with a tail appendage, 2 suckers, an intestine, an excretory system, and the rudiment of the reproductive system). At the anterior end of the body, some forms have a sharp stylet or a bunch of spines that perform a perforating function, and a group of penetration glands. Cercariae have developed all organ systems with the exception of the reproductive system.
filamentous, formed by the host organism. In those trematodes that have one intermediate host ( liver fluke, fasciolopsis), the cercaria encysts in the external environment and is called adolescaria.
Metacercaria and adolescaria are invasive stages for the final host, in whose body they turn into marita.
The invasive stage of blood flukes for the definitive host is the cercariae, which actively invades the host’s body through the skin.
A group of diseases caused by trematodes is called trematodes. Complex environmental conditions on the territory of the Republic of Bashkortostan are favorable for the entire development cycle of liver, feline and lanceolate flukes. They are unfavorable for the development of pulmonary and blood flukes, but increased migration of the population not only within Russia, but from countries far and near abroad, endemic for paragonimiasis and schistosomiasis, contributes to the importation of these trematodes into the territory of the republic.
The following representatives of trematodes are of medical importance: liver fluke (Fasciola hepatica), cat fluke (Opisthorchis felineus), pulmonary fluke (Paragonimus westermani), blood flukes (Schistosoma haematobium, Schistosoma mansoni, Schistosoma japonicum).
Class Flukes. Lanciform fluke. Systematic position, morphophysiological characteristics, life cycle, invasive stage, route of invasion, invasion factors, localization, pathogenic effect. Laboratory diagnostics and measures for public and personal prevention of dicroceliosis. Prevalence in the Republic of Belarus.
^ Lanceolate fluke - Dicrocelium lanceatum- causative agent of dicroceliosis (biohelminthiasis)
Geographical distribution - ubiquitous.
Development cycle. Biohelminth. The main host is herbivorous mammals. The first intermediate host is terrestrial mollusks of the genera Zebrina, Helicela etc. The second one is the ants . Formica. Sporocysts of the first and second order develop in the body of the mollusk; there is no redia stage. The cercariae stick together, form collective cysts, and are released onto the plants. Metacercariae develop in the body of ants.
When the air temperature drops, infested ants move to the tops of plants and fall into a kind of torpor. Infection of humans and animals occurs when ants are accidentally ingested with grass.
Localization. In the liver of large and small cattle and some other animals; very rare in humans.
Pathogenic effect similar to other liver flukes.
Laboratory diagnostics. Microscopy of feces and duodenal contents. Eggs are found. The eggs have an elongated oval shape and are always asymmetrical. The shell is thick, smooth, with a wide, slightly flattened cap at the narrowed pole of the egg. A mature egg is dark brown, an unripe egg is light yellow. Dimensions 38 - 45 ´ 25 - 30 microns.
It is necessary to remember about the possibility of transit eggs getting into gastrointestinal tract humans along with the eaten liver of domestic animals suffering from dicroceliosis.
Prevention. Measures to prevent dicroceliosis have not been sufficiently developed. Sometimes ants are controlled in grazing areas. However, such measures can lead to other undesirable consequences, since ants are important soil formers and human assistants in the fight against insect pests. The destruction of shellfish and deworming of livestock are also important.
^ 116. Class Tapeworms. Class characteristics. Representatives of medical significance. Prevalence in the Republic of Belarus.
Morphology. Cestodes have a flat, ribbon-like body. Body length and number of segments different types vary greatly (from 1 mm to 10 - 18 m). At the front end there is a head - scolex, Further neck and then strobila, consisting of segments - proglottid. Scolex equipped with devices for attachment to the intestinal walls - suckers, and in some species, hooks (order of tapeworms) or suction slits - bothria (order of tapeworms). The cervix is
is a growth zone. New proglottids bud from the neck, causing the previously formed ones to move back.
^ Nervous and excretory systems have the same structure as those of trematodes. The nervous system and sensory organs are poorly developed. The excretory system is represented by protonephridia. Unlike trematodes, cestodes in excretory system two excretory ducts that run along the sides of the body and open outward into the excretory pore. Blood and respiratory systems No.
^ Reproductive system in the proglottids closest to the neck, it is still absent, but as the segments grow, it begins to develop. First, male and then female organs appear. Hermaphroditic proglottids in the middle part of the strobila reach sexual maturity.
^ Male reproductive system:a large number of vesicular testes, the ducts of which merge into a common ejaculatory canal ending in the cirrus.
^ Female reproductive system. In the ootype, the vagina, ovarian ducts, vitelline ducts, and Melis corpuscles open. Fertilized eggs enter the uterus. The uterus may have different shape: sometimes a tube folded into loops ending in an outlet (wide tape) through which the eggs exit into the external environment, sometimes it is a tube ending blindly; some have a sac-shaped uterus. Young proglottids do not have a reproductive system. In the hermaphroditic segments, the formation of reproductive products, fertilization and the formation of eggs occur, which move to the uterus, where their maturation begins. As eggs arrive, the uterus increases in size (with the exception of forms that have an outlet in the uterus) and gradually fills the entire segment, displacing the remaining organs of the reproductive system. Such a segment is called “mature”. As the worm grows, the rear, mature segments gradually tear off, and new, young segments are formed from the neck.
^ Life cycles cestodes are quite complex; they necessarily have two larval stages - oncosphere and finna.
Oncosphere develops in the egg while it is still in the uterus. This is a six-hooked, spherical embryo. Outside, the oncosphere is covered with a thick shell with radial striations. In the intestine of the intermediate host, the oncosphere emerges from the membranes and, with the help of hooks, penetrates into blood vessels and is carried by the blood into various tissues and organs, where it turns into the next larval stage - Finn:
Cysticercus- Finn in the form of a bladder filled with liquid, into which one scolex (bovine and pork tapeworm) is inserted.
Tsenur - bubble with several screwed-in heads.
Cysticercoid in front has a
the widest part with an inverted scolex, and at the back - the tail
tomato appendage (dwarf tapeworm).
Echinococcus - Finn in the form of a large maternal bladder with daughter and grandchild bladders, inside of which a large number of scolex develop.
Plerocercoid- worm-like larva, at the anterior end of which there are two suction grooves (bothria).
Procercoid- wide tape
Larvocyst alveococcus - multi-chambered bladder
Finns develop into adults in the intestines of definitive hosts, which are infected by eating the meat of intermediate hosts. Under the influence of digestive juices, the scolex turns outward from the bladder, attaches to the intestinal wall, and proglottids begin to bud from the neck.
IN larval stage Echinococcus parasites in the human body ( Echinococcus granulosis) and alveococcus ( Alveococcus multilacularis)(liver, lungs, brain, rarely – spleen, kidneys, bones, muscles). Methods for specific and additional diagnostics of alveococcosis and echinococcosis: latex agglutination reaction (RAL) with echinococcal antigen, indirect hemoagglutination reaction (IRHA) with erythrocyte diagnosticum, flocculation reaction with bentonin (RFB); allergy test; X-ray method, ultrasound, tomography, radioisotope scanning.
For dwarf tapeworm ( Hymenolepis nana) humans are both the definitive and intermediate hosts. Laboratory diagnosis of hymenolipedosis is based on the detection of eggs in feces.
Diseases caused by cestodes are called cestodes.
^ Pathogenic effect of cestodes - toxic-allergic and mechanical (violation of the integrity of the intestinal wall by suction cups, hooks, pinching of the wide tapeworm by bothria, pressure on the organs and tissues of the larvocysts of echinococcus and alveococcus) and absorption of the host’s digested food and vitamins (wide tapeworm).
Protozoa are a source of food for other animals. In the seas and fresh waters, protozoa, primarily ciliates and flagellates, serve as food for small multicellular animals. Worms, mollusks, small crustaceans, as well as the fry of many fish feed primarily on single-celled organisms. These small multicellular organisms, in turn, feed on other, more large organisms. The largest animal that has ever lived on Earth, the blue whale, like all other baleen whales, feeds on very small crustaceans that inhabit the oceans. And these crustaceans eat single-celled organisms. Ultimately, whales depend on single-celled animals and plants for their existence.
Protozoa are participants in the formation of rocks. Examining a crushed piece of ordinary writing chalk under a microscope, you can see that it consists mainly of the smallest shells of some animals. Marine protozoa (rhizopods and radiolarians) play very important role in the formation of marine sedimentary rocks. Over many tens of millions of years, their microscopically small mineral skeletons settled to the bottom and formed thick deposits. IN ancient geological epochs during the mountain-building process sea bottom became dry land. Limestones, chalk and some other rocks largely consist of the remains of the skeletons of marine protozoa. Limestone has long been of great practical importance as a building material.
The study of fossil remains of protozoa plays big role in determining age different layers earth's crust and finding oil-bearing layers.
The fight against water pollution is the most important state task. Protozoa are an indicator of the degree of pollution of fresh water bodies. Each type of protozoan animal requires certain conditions to exist. Some protozoa live only in clean water containing a lot of dissolved air and not polluted by waste from factories and factories; others are adapted to life in water bodies of moderate pollution. Finally, there are protozoa that can live in very polluted, wastewater. Thus, the presence of a certain species of protozoa in a reservoir makes it possible to judge the degree of its pollution.
So, protozoa are of great importance in nature and in human life. Some of them are not only useful, but also necessary; others, on the contrary, are dangerous.
Protozoa are a source of food for other animals. In the seas and fresh waters, protozoa, primarily ciliates and flagellates, serve as food for small multicellular animals. Worms, mollusks, small crustaceans, as well as the fry of many fish feed primarily on single-celled organisms. These small multicellular organisms, in turn, feed on other, larger organisms.
The largest animal that has ever lived on Earth, the blue whale, like all other baleen whales, feeds on very small crustaceans that inhabit the oceans. And these crustaceans feed on single-celled organisms. Ultimately, whales depend on single-celled animals and plants for their existence.
Protozoa are participants in the formation of rocks. Examining a crushed piece of ordinary writing chalk under a microscope, you can see that it consists mainly of the smallest shells of some animals. Marine protozoa (rhizopods and radiolarians) play a very important role in the formation of marine sedimentary rocks.
Over many tens of millions of years, their microscopically small mineral skeletons settled to the bottom and formed thick deposits. In ancient geological epochs, during the mountain-building process, the seabed became dry land. Limestones, chalk and some other rocks largely consist of the remains of the skeletons of marine protozoa. Limestone has long been of great practical importance as a building material.
Protozoa, living in the oceans, fresh waters, soil and higher organisms, occupy an important place in the cycle of substances in the biosphere. In the aquatic environment, protozoa are the basis of plankton, used as food by other larger animals. Thick layers of sedimentary rocks are formed from the skeletons of protozoa: foraminifera, radiolarians and armored flagellates - coccolithophores.
Many aquatic protozoa - sedimentators that feed on suspended organic particles and bacteria - play a significant role in the biological purification of water. Soil amoebas, ciliates and flagellates are an important part of the soil fauna: they take part in soil formation. A number of species of protozoa constitute a useful group of symbionts of higher animals that improve digestion and metabolic processes in the body.
More than 200 species of flagellates live in the stomachs of termites, converting fiber into sugar.
Collared flagellates - possible ancestors multicellular animals.
Slipper ciliates serve as food for the inhabitants of reservoirs.
In the seas and oceans, many shell rhizomes die every hour. Falling to the bottom, they form limestone deposits. The chalk used to write on a blackboard, whiten the walls and ceilings of buildings, and the limestone used to build houses consist mainly of the shells of marine protozoa. Using the remains of accumulations of shells of extinct marine unicellular animals, geologists find places of deposits of oil and other minerals.
Food chains in aquatic ecosystems begin with microscopic algae. The second link in them is usually planktonic protozoa - the first consumers of green products. Then they become the basis of nutrition for the animal-eating inhabitants of aquatic ecosystems: crustaceans, fish fry and all subsequent consumers. When the remains of dead plants and animals sink to the bottom, they are picked up by bottom-dwelling protozoa.
Many protozoa inhabit every millimeter of soil saturated with ground moisture. Together with other inhabitants, they maintain soil fertility.
The irony of fate: herbivorous animals themselves are not able to digest cellulose (fiber - note! Protozoa do this for them, populating their food tract from the first days of life. The intestine of a termite, the cecum of a hare and the stomach of a cow are equipped with special warehouses to accommodate these cohabitants. The owner It assimilates only the result of their digestion, and at the same time the protozoa themselves.
- Determine from Figure 36 what is the importance of the simplest animals in the life of animals - inhabitants of water bodies?
- What diseases caused by single-celled animals do you know?
The meaning of free-living protozoa. Many protozoa, especially ciliates that feed on bacteria and rotting organic debris, are involved in cleaning water bodies from pollution. At favorable conditions life they multiply quickly. Their a myriad of serves as food for fish larvae and fry, various small crustaceans, aquatic insects and their larvae, which, in turn, are eaten by grown fish fry and larger aquatic animals (Fig. 36). Rice. 36. Nutritional value the simplest species in the life of freshwater organisms, euglenas are of great importance in the purification of water bodies and in the nutrition of many small freshwater animals. In addition, by creating organic substances from inorganic ones in the light, they, like plants, reduce the content of water in water. carbon dioxide and increase the amount of oxygen.
Many of the protozoa serve as indicators of water purity. Thus, a high number of euglena and ciliates of some species indicates water pollution organic substances. Trumpeters, spirostomums, and slipper ciliates live in cleaner water, and in water with a low content of organic and big amount minerals The common amoeba usually lives.
The sporozoan phylum also includes coccidia. They settle in the cells of the intestinal or stomach walls of rabbits, chickens and other animals. Sick animals refuse food and soon die. Infection occurs through food contaminated with the feces of sick animals. There are known cases of coccidiosis in humans.
➊ What is the importance of protozoa in the life of other animals - inhabitants of water bodies? ➋ What protozoa and how do they participate in the purification of water bodies? ➌ The presence of which protozoa in water is an indicator of its contamination with organic substances? ➍ What protozoa and how did they form the strata of chalk and limestone on Earth? ➎ What simple organisms are causative agents of human and animal diseases?
The discovery of A. Leeuwenhoek generated significant interest in the study of microscopic creatures among scientists in all countries of the world. At the end of the seventeenth century. A large number of works devoted to their description appeared. Leeuwenhoek was the founder of the science of microbiology.
Protozoa are a source of food for other animals. In the seas and fresh waters, protozoa, primarily ciliates and flagellates, serve as food for small multicellular animals. Worms, mollusks, small crustaceans, as well as the fry of many fish feed primarily on single-celled organisms; Without protozoa, their existence would be impossible. These multicellular animals, in turn, feed on larger animals, and primarily on growing fish fry. It is clear how important protozoa are in the life of nature and in the national economy.
The largest animal that has ever lived on Earth, the blue whale, feeds on very small crustaceans that inhabit the oceans. Other toothless whales also feed on them. And these crustaceans, in turn, feed on single-celled animals. So it turns out that, ultimately, the existence of whales depends on single-celled animals and plants.
Protozoa are participants in the formation of rocks. Examining a crushed piece of ordinary writing chalk under a microscope, you can see that it consists mainly of small shells of some animals. Many calcareous rocks of the Volga region, the Urals, Crimea, and the Caucasus consist of the same microscopic shells. Each such shell once contained the body of a simple animal - a foraminifera, which lived in ancient times on the bottom of seas and oceans.
And even now, a significant part of the ocean floor is covered with silt consisting of foraminifera shells. Many limestones consist almost entirely of such shells. Limestone has long been of great practical importance as a building material. For example, gigantic ancient structures - the Egyptian pyramids - were built from them.
Foraminifera are the simplest animals; they are closest to amoebas. Their different types differ in the structure of the calcareous shell, inside which protoplasm with nuclei is placed. Often the shell is spiral and multi-chambered inside. In the partitions between the chambers there are openings through which the protoplasm located in adjacent chambers communicates. The Latin word foramen means hole, hence the name foraminifera (hole-bearing).
Foraminiferal remains in rocks given great importance in geological exploration: discovery in limestone certain types foraminifera indicates the proximity of oil-bearing layers.
It must be borne in mind, however, that not all limestones consist of protozoan shells. A considerable amount of limestone is formed by the remains of coral skeletons, mollusk shells, etc.
Protozoa are an indicator of the degree of pollution of fresh water bodies. The fight against water pollution is the most important state task. Each type of protozoan animal requires certain conditions to exist. Some protozoa live only in clean water, containing a lot of dissolved air and not polluted by waste from factories and factories; others are adapted to life in water bodies of moderate pollution. Finally, there are protozoa that can live in very polluted wastewater. Thus, the presence of a certain species of protozoa in a reservoir makes it possible to judge the degree of its pollution.
Malaria is a terrible scourge of people, especially in tropical and subtropical countries. And in temperate latitudes it is quite widespread. Severe malaria is caused by special protozoa - malarial plasmodia (see article “Animals - keepers and carriers of diseases”).
Close to Leishmania large group parasitic protozoa - trypanosomes. Various types of trypanosomes cause serious illnesses humans and animals. These diseases are common in the tropics. In the temperate zone, people do not suffer from such diseases. Of the animal diseases caused by trypanosomes, the most dangerous disease in the USSR is suauru disease, which kills camels and horses in the Lower Volga region and Central Asia.
So, protozoa are of great importance in nature, in human life and in the national economy. Some of them are not only useful, but also necessary; others, on the contrary, are dangerous.
Wonders of nature
The skeletons of marine protozoa foraminifera and especially radiolarians are striking in their amazing beauty and diversity. Snowflakes, which so surprise us on a frosty winter day, can give us some idea of the diversity of their forms.
It is interesting to note that the beauty and variety of forms of marine protozoa inspired the artist who designed the scenery for the stage “Chernomor’s Garden” during the first production of M. I. Glinka’s opera “Ruslan and Lyudmila” (in 1842).
The artist used a colorful atlas of protozoa, published in Germany in the 30s of the last century.