Flatworms name meaning and habitat. Flatworms: structural features, types and general characteristics Flatworm habitat

Integuments of the body Outside, the body is covered with a single-layer epithelium. In ciliary worms, or turbellaria, the epithelium consists of cells that carry cilia. Flukes, monogeneans, cestodes, and tapeworms lack ciliated epithelium for most of their lives (although ciliated cells may occur in larval forms); their covers are represented by the so-called tegument, in a number of groups bearing microvilli or chitinous hooks. Tegumented flatworms belong to the Neodermata group. Flatworms can regenerate 6/7 of their body.

Musculature Under the epithelium there is a muscular sac, consisting of several layers of muscle cells that are not differentiated into individual muscles (a certain differentiation is observed only in the region of the pharynx and genital organs). The cells of the outer muscle layer are oriented across, the inner - along the anterior-posterior axis of the body. The outer layer is called the layer of circular muscles, and the inner layer is called the layer of longitudinal muscles.

Nervous system and sensory organs The nervous system is represented by nerve nodes located in the anterior part of the body of the worm, cerebral ganglia and nerve columns extending from them, connected by jumpers. The sense organs, as a rule, are represented by separate skin cilia - processes of sensitive nerve cells. Some free-living representatives of the type, in the process of adapting to living conditions, acquired light-sensitive pigmented eyes - primitive organs of vision and organs of balance.

Structure The body is bilaterally symmetrical, with clearly defined head and tail ends, somewhat flattened in the dorsoventral direction, in large representatives it is strongly flattened. The body cavity is not developed (with the exception of some phases of the life cycle of tapeworms and flukes). The exchange of gases is carried out through the entire surface of the body; respiratory organs and blood vessels are absent.

Questions: How many flatworms live in Russia? What are the body coverings of flatworms? What kind of muscles? What are the sense organs? Briefly describe the structure of the body. How do flat people eat? How do they breathe? How do they reproduce?

Interesting Facts 1. By digestion flatworms able to "learn". A group of scientists have made an unusual discovery regarding the abilities of flatworms. It turns out that if planar worms are first taught to go through the maze, then grind them into a puree and let other worms eat it, then such worms will be able to go through this maze the first time.

Interesting facts 2. Different-sex species of worms - schistosomes are inseparable throughout life. The female lives in the pocket of the male all her life.

Interesting facts 3. Almost all types of flatworms can turn inside out. 4. And here are some more interesting facts about flatworms. For example, flatworms are truly almost immortal. If you cut off a very small piece from the worm, approximately 1/100 of the whole worm, it is still able to recover to the whole organism.

Interesting facts 5. On the skin of some planarians living in fresh water, scientists found nettle cells, which are very similar to stinging cells found in coelenterates. It turns out that these cells really previously belonged to coelenterates, which subsequently ate ciliary worms. Stinging cells are not digested by worms. They get into their skin and serve to carry protective function and attacks.

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Worms are a fairly common species on earth. Roundworms differ from flatworms both in appearance and in the construction of internal vital systems. However, there are not only differences between these species. Worms of these classes do not have a circulatory and excretory system in the traditional sense, but their life cycle is the same. Adults become dangerous.

The differences between roundworms and flatworms are not significant, but the harm to human health is significant.

General information on the comparison of flatworms and roundworms

Flat individuals have a flattened body (often ribbon-like). They also differ in the presence of 3 muscle layers:

  • annular;
  • diagonal;
  • longitudinal.

roundworms

  • A cylindrical thin body, consisting of the so-called outer cuticle, under which there is an epithelial layer and muscles running along.
  • Fluid fills the body (hydroskeleton).
  • The structure of the digestive system is simple. This is a tube with mouth and excretory openings. It is conditionally divided into 3 parts - front, middle and back.
  • The nervous system is represented by the pharyngeal ganglion (a kind of brain). The nerve trunks branch off from the ganglion. Roundworms have a sense of touch and taste.

The main differences between roundworms within a species are their habitat. It should be noted that, unlike flat ones, round ones are bisexual. Males and females are usually distinguishable. This type has more than 15 thousand species living almost everywhere. Some can be seen under a microscope, but there are, in comparison, giants.

flatworms

  • ciliary;
  • tape;
  • flukes.

The structure of flatworms is somewhat different from roundworms. Namely:

Flat representatives, with rare exceptions, are same-sex. Their breeding system is quite complex. In addition to the present symbiosis of male and female genital organs, this includes additional appendages and formations that fully ensure the process of fertilization and development of the embryo, by providing it with all the necessary substances.

What is the difference?

What common?

Any worms that have entered the human body are dangerous for him, especially if they are not noticed in time and adequate treatment is not applied. Helminths can cause many diseases, including: ulcers, colitis, intestinal obstruction, cysts, lesions of the central nervous system, meningitis. Among the most dangerous species are flukes, paragonims and schistosomes, echinococci, roundworms, hookworms, trichinella.

The causative agent of opisthorchiasis: what it looks like, structure, habitat

The first case of the appearance of opisthorchis was recorded in 1884, when a helminth, previously unknown to science, was found in a cat in the northern part of Italy. S. Rivolta called the helminth a cat fluke.

7 years after the first case, the cat fluke was already found in the human body in Russian Siberia. In 1891, professor-pathologist K. N. Vinogradov conducted research on the liver and found a leaf-shaped worm in it, which he gave the name of the Siberian fluke. Further studies have shown that the Siberian fluke is nothing more than a previously caught cat fluke. Subsequently, the helminth was given the name opisthorchis, and the disease began to be referred to as opisthorchiasis.

The structure and appearance of the helminth

Unlike other representatives of its class, opisthorchis is much smaller. This is what a helminth looks like: the body of a feline fluke is shaped like an oblong flat leaf or lancet, its length rarely exceeds 18 millimeters, and its width varies from 1.5 to 2 millimeters.

There are two suckers on the body of the helminth, one is the abdominal sucker, and the other is the oral sucker, with the help of which the opisthorchis is attached to the mucous membranes of the damaging organs and sucks nutrients. The oral sucker of the helminth serves as the beginning of its digestive tract. At the rear end of the body there is a special channel through which the excretion of processed waste products of the worm is carried out.

The reproductive system of the causative agent of opisthorchiasis is based on the hermaphroditic principle. The helminth has two pairs of genital organs. Reproduction of opisthorchis occurs by the release of eggs. One individual of the worm in the body of its final host is capable of producing 900-1000 eggs daily.

The eggs of opisthorchis are pale yellow in color, have a delicate double-circuit shell, there is a special cap on one pole of the eggs, and the other pole is slightly thickened. The size of helminth eggs varies from 0.011 to 0.019 in width and from 0.023 to 0.034 in length.

Habitat and endemic foci

The habitat of opisthorchis eggs is freshwater reservoirs, in such conditions they are able to maintain their vital activity for one year. It should be noted that opisthorchis develop with the participation of three carriers - one final host and two intermediate ones.

Considering that the helminth develops in freshwater reservoirs, special endemic foci are distinguished, where the probability of infection with opisthorchiasis is high. These endemic foci include:

  1. Yamalo-Nenets Aut. district, Khanty-Mansiysk Aut. district, regions of Siberia, Altai Republic. Endemic foci in Russia are also confined to the basins of the Irtysh, Ob, Volga, Northern Dvina, Kama, Don, Dnieper, Biryusa.
  2. Ukraine and Kazakhstan.
  3. Italy, France, Holland.
  4. India, Thailand, other countries of Southeast Asia where fishing prevails.
  5. Canada and Northern regions of the USA.

The development of the causative agent of opisthorchiasis

The causative agent of opisthorchiasis belongs to biohelminths, which means that a change of owners is necessary for its successful life. In this case, as mentioned above, the trematode has one final and two intermediate hosts; in their organisms, it goes through a complete life cycle.

The cycle of opisthorchis begins in the body of the final host, which is a person, as well as some mammals (cats, dogs, pigs, foxes, and others). Sexually mature individuals lay eggs, together with the feces of the host, they pass into environment, in the presence of favorable conditions, they continue their development.

Once in water bodies, opisthorchis eggs settle to the bottom, where they are eaten by freshwater mollusks. In their organisms, the larvae of opisthorchis, miracidia, emerge from the eggs. Miracidia have special cilia, penetrating into the intestinal wall of the mollusk, they lose them and turn into the maternal sporocyst. The sporocyst gives rise to rediae, which in turn develop into cercariae. Tailed cercariae exit the body of mollusks through the cover or mouth opening and begin hunting for the second intermediate host.

The second intermediate host of the pathogen of opisthorchiasis is a fish of the carp family. The fish swallows them through the mouth opening, and cercariae can also enter its body through the lateral lines and integument. In the organisms of cyprinids, cercariae are localized in the muscles and subcutaneous tissue, turning into metacercariae. Metacercaria larvae are slightly oval in shape, measuring 0.34 mm long and 0.24 mm wide. Metacercariae develop in the body of fish for a month and a half, during which time they become invasive to humans.

How does the infection of the final host occur? The causative agent of opisthorchiasis enters the human (animal) body when eating raw or insufficiently thermally processed fish. In the human body, metacercariae reach their sexual maturity as early as 10-14 days. The main centers of impact are the liver, its ducts, gallbladder and pancreas. Characteristic symptoms appear two to three weeks after the onset of the invasion.

Opisthorchiasis proceeds in two stages, this is due to the peculiarities of the life cycle of the helminth. This implies the difference in the clinical picture for the period of invasion and the later period. Entering the human body in the stage of metacercaria, the helminth develops to the stage of puberty, and then during for long years lives in its usual places of localization.

In the early stages, the causative agent of opisthorchiasis provokes the development of an allergic reaction, which is very pronounced. A similar reaction of the human body is due to the fact that the helminth secretes enzymes and metabolic products that have a toxic effect.

  • In the lymphatic system, inflammatory processes occur, the same phenomena are observed in the spleen.
  • Purulent-inflammatory reactions can be found in the mucous membranes of the gastrointestinal tract, respiratory system.
  • There is a violation of blood microcirculation in the internal organs, first of all, the part of the circulatory system located in the liver suffers.
  • Hypoxic signs develop, gas exchange is disturbed.
  • Dystrophic changes are observed in the liver, heart and other organs.

The rate of development of pathological changes in the human body directly depends on the degree of intensity of invasion.

The chronic stage of opisthorchiasis is characterized by mechanical, allergic and neuro-reflex harmful effects of the helminth. There is a secondary influence of the microbial flora, as well as the influence of the decay products of their own cells and tissues, most of all the cells of the gallbladder. Without timely diagnosis and treatment, the development of chronic cholangitis, pericholangitis, hepatitis, cirrhosis of the liver is likely.

Neuro-reflex exposure is fraught with violations of the tone of the gallbladder and biliary tract, secretory dysfunction, impaired motor function of the stomach and intestines.

Symptoms of opisthorchiasis, as a rule, include the clinical picture of a disease such as chronic gastroduodenitis. The peculiarity is associated with a pathological change in the functions of the pancreas and adrenal glands, as well as with the development of inflammatory processes in the mucous membranes of organs. The causative agent of opisthorchiasis also provokes hormonal instability.

Treatment of opisthorchiasis should be immediate and mandatory, neglected cases of the disease lead to the development of liver cancer. Prevention of opisthorchiasis consists in the correct and sufficient processing of freshwater fish before eating it.

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Tapeworms (cestodes)

The oldest traces of cestodes are found in the remains of sharks living 270 million years ago.

Human infection

People can become infected with several types of tapeworms in different ways. When eating undercooked meat: pork (pork tapeworm), beef (bovine tapeworm) and fish (wide tapeworm). Or when living and eating in conditions of poor hygiene - pygmy and rat tapeworms, echinococcus.

Treatment

Now for the treatment of tapeworms, the main drugs are Praziquantel and Albendazole. Praziquantel is an effective agent that is more preferable than the obsolete Niclosamide. Cestodosis can also be treated with certain types of antibiotics. Doctors after a course of drugs can give enemas to patients to completely remove the worms from the intestines.

Structure

The main common elements of the cestode body. Others may differ (the presence of a rim with hooks, suction cup types may be slit-like, etc.)

Larvae, in contrast, show a wide range of habitat preferences and can be found in almost any organ of both vertebrate and invertebrate hosts. Although most larval species have a preference for a particular organ.

The absence of a gastrointestinal tract markedly separates cestodes from nematodes and trematodes. The outer tegument (special epithelium) of the body serves not only as a protective covering, but also as a metabolically active layer through which nutrients are absorbed, along with secretions and waste products transported out of the body. To facilitate this process, the entire surface of the body is covered with microscopic wrinkles or protrusions, which greatly increase the surface area available for absorption of nutrients.

Worms do not need to move inside the host body, so they do not have any organs of the musculoskeletal system and external bristles.

They also lack circulatory and respiratory systems.

The excretory and nervous systems of cestodes are similar to those of other representatives of flatworms.

Proglottid

The body of helminths of this class consists of a chain of segments (proglottids), which can be immature or mature, the last of which are at the end of the body and contain a fully formed uterus filled with eggs.

The totality of all proglottids (from two to several thousand) is called a strobila. It is thin and resembles a strip of tape. This is where the common name “tape” comes from.

New segments grow from the neck, containing an independent digestive and reproductive system. By the time the segment reaches the end of the worm's tail, only the reproductive organs remain. In fact, such segments are already just egg bags. The segment then separates from the body, carrying the tapeworm eggs out of the definitive host along with the feces.

Thus, each cestode consists of a series of segments that have a complete set of reproductive organs in a progressive degree of sexual maturity, which bud from the body from the side of the tail.

scolex

Life cycle

The life cycle of cestodes includes an intermediate and definitive host (with the exception of the pygmy tapeworm, which can develop in the same organism). It consists of several stages.

At the first stage, sexually mature individuals of tapeworms are in the body of the final host (vertebrates and humans), multiply and produce eggs, which are subsequently excreted into the environment along with feces.

At the second stage (depending on the type of cestodes), a larva (embryo) is formed in the eggs on land or in water.

At the third stage, the larvae enter the organism of the intermediate host (vertebrates and invertebrates), where Finns are formed from them. Finna is a spherical bubble (less often worm-shaped), filled with liquid, inside of which there is one or more heads. Depending on the number of heads, as well as on the presence of child bubbles inside, there are 5 forms of Finns:

  • cysticercus;
  • cysticercoid;
  • tsenur;
  • echinococcus;
  • plerocercoid.

At the fourth stage, the Finns enter the body of the final host, their shell disappears, and segments begin to grow from the heads attached to the walls of the intestine. Thus, at this stage, the growth and development of adults occurs.

The most common representatives

Pork and bovine tapeworm (tapeworms)

Infections caused by ingestion of larvae of representatives of the genus Tepni, in humans or animals, are called teniidoses. The presence of an adult worm in the body (taeniasis and teniarhynchosis) rarely causes symptoms other than minor intestinal disorders (diarrhea, constipation or indigestion).

Bovine tapeworm does not cause human cysticercosis.

dwarf tapeworm

The pygmy tapeworm (Hymenolepis nana) is the smallest member of the tapeworm genus that infects humans. This cestode belongs to big family known as Hymenolepis. Diagnostic features of this family: scolex contains 24-30 hooks; the adult has one to three large testes and a sac-like uterus.

The dwarf tapeworm is cosmopolitan, i.e. widely distributed throughout the world. Infection is more common in children, although adults can also be infected (developing hymenolepiasis). The disease may not cause any symptoms even with significant infection. However, some cases of anxiety, irritability, anorexia, abdominal pain, and diarrhea have been reported in hymenolepiasis.

The life cycle of Hymenolepis nana does not necessarily require an intermediate host, full development occurs within the gut of a single host (the "direct" life cycle). It may also use insects as an intermediate host.

wide ribbon

As a rule, they have a scolex, which is characterized by two shallow elongated bothria (slits), located one dorsally (on the back) and the other ventrally (on the ventral side). The proglottids are flattened dorsoventrally, i.e. from dorsal to ventral.

With a little frown, let's start the description worms. What to do if there are such trump cards in the thick "deck" of the natural diversity of life forms.

I write "trump cards" not only because " worms". The evolution of multicellularity from two-layer has led to much more perfect forms of organisms with a three-layer body structure. And then nature had to tinker for a long time, creating not one, but whole.

Somehow it even becomes a shame for all mammals, which represent only a separate class of organisms in the type of chordates. And here, "some kind of worms" - and whole three types: flatworms, roundworms and annelids.

Well, let's start everything in order, so:

……………… Type Flatworms (three layers)

…………………………………. K l . A. With. With. s

__________________________________________________________________________________

.. Ciliary worms……………………….. Flukes……………………….. Tapeworms

___________________________________________________________________________________

White planaria…. Liver fluke …… …………… Bull tapeworm ________________________________________________________________________________________________

……………………………………………….. More than 15 thousand species

Habitat : marine and fresh water bodies, moist soil, human and animal organisms.

……..
Structure: bilaterally symmetrical . For the first time in embryos, a third germ layermesodermfrom which parenchymal cells and the muscular system develop. Body flattened.

………..
Integuments of the body and muscular system: skin-muscular sac - from a single-layer epithelium (may be with eyelashes) and three layers smooth muscles (circular, longitudinal and oblique).

Movement: muscle contraction (flukes, tapeworms) or movement of cilia andmuscles (ciliary worms).

body cavity: absent , internal organs located inparenchyma.

Digestive system:has two sections - anterior (mouth, pharynx) and middle (branches intestines). The bowel is closed anal opening is missing and leftover food is removed. through the mouth. At the tapeworms digestive system absent- absorption of food by all cells of the body. As you remember, this is one of the forms of biological progress -.

excretory system: appears for the first time formed by a system of tubules. one end starts in the parenchyma stellate cell with a bunch of cilia, and the other flows into excretory duct. ducts combined into one or two common channels ending excretory pores. Elementary unit of the system areprotonephridia.

Nervous system:from supraesophageal ganglions(ganglia) and longitudinal nerves trunks, related cross jumpers(ladder type).

Sense organs: touch And chemosensitive cells. Free-living people have organsvision And balance.…………..

reproductive system: To usually hermaphrodites.Men'sreproductive system: testes, vas deferens, ejaculatory duct and copulatory organ. Women'sreproductive system: ovary, oviduct, uterus, yolk glands.

1. The appearance of the third germ layer -mesoderm.
2. The appearance of the excretory system - protonephridia.
3. Emergence of the nervous system ladder type.

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All worms can be divided into three types (flat, ringed, round), each of which has its own characteristic features. This type refers to invertebrates lacking a body cavity and possessing bilateral symmetry.

The main signs of the type of flatworms

  • digestive;
  • nervous;
  • sexual;
  • excretory.

This type has the presence of several systems and even the rudiments of organs

Circulatory system

Not available, but the function of the blood is performed by the parenchyma, consisting of connective cells. It is she who transports nutrients in the body.

Digestive system

Rather simplified, it consists of a pharynx and intestines.

The pharynx is powerful, can:

  • suck;
  • twist and wrap around your prey.

The intestine consists of two sections - anterior and middle, most often branched. It has a closed structure, so that all undigested waste exits through the mouth. The mouth opening is located closer to the middle of the body of the worm.

Free worms are mostly predators and they even have a kind of adaptation for capturing prey. This system is not observed in all classes; more primitive worms do not have it. For example, tapeworms feed on the entire surface.

excretory system

The excretory system is quite large and consists of many tubules that combine and lead to the excretory pores.

The parenchyma contains special cells that drive harmful substances into the tubules. For humans, these excretory products are very dangerous and toxic along with poison.

Muscular system

Presented, which form muscle fibers covered with epithelium. By contracting these fibers, the worms can move about.

Nervous system

In the upper part of the worm there are two head nodes, two nerve trunks descend from them. Longitudinal nerve trunks penetrate the body of the worm completely and are interconnected by transverse nerves, similar to a short flight of stairs.

With the help of dermal cilia, some worms can:

  • feel the temperature
  • other external stimuli.

And among free worms there are representatives who have developed organs of vision (pigments that react to light) and balance.

species diversity

There are three classes of this type:

  1. Flukes.
  2. Tape.
  3. Eyelash worms.

Flukes: class representatives and characteristics

Class members:

General characteristics of the class flukes:

Tapeworms: representatives of the class and characteristics


General characteristics of the tapeworm class:

Class members:

  • is in stagnant water - ponds, ditches, very active. Covered with cilia, uses them to move on the water surface and attach to the bottom. The length is about 35 cm. The digestive system is developed, it feeds mainly on crustaceans and small invertebrates. Reproduction is sexual and asexual (divided in half, and then each half is completed). Wide range of habitat, found almost everywhere.
  • Ehrenberg mesostoma- a flat leaf-shaped body, slightly convex, transparent and colorless, in old worms it is brown. Unlike planarians, the intestines are straight, not branched. They live attached to aquatic plants. The mesostoma is predatory, preying on crustaceans, worms, insects and even freshwater hydras. It is able to tolerate the drying up of reservoirs, live in flooded meadows, puddles, and after their drying out, the eggs of the mesostom remain capable of development.
  • Ground worm rhynchodemus- soil worm, lives in damp places, most often under stones. Habitat Europe and North America. It can reach 12 mm, the color is brown with red longitudinal spots. Cilia are preserved on the ventral side of the body, moves by muscle contraction. Predator that eats insects.


General characteristics of ciliary worms: