Water and soil habitat. Flatworm habitat Where do flatworms live?

a brief description of

Habitat and appearance	Size 10-15 mm, leaf-shaped, live in ponds and slow-flowing reservoirs
body cover and musculocutaneous sac	The body is covered with a single layer (ciliary) epithelium. The superficial muscle layer is annular, the inner one is longitudinal and diagonal. There are dorso-abdominal muscles
body cavity	The body cavity is absent. Inside is spongy tissue - parenchyma
Digestive system	Consists of the anterior (pharynx) and the middle, which has the appearance of highly branched trunks ending blindly
excretorysystem	Protonephridia
Nervous system	The brain ganglion and the nerve trunks coming from it
sense organs	Tactile cells. One or more pairs of eyes. Some species have balance organs
Respiratory system	No. Oxygen is supplied through the entire surface of the body
reproduction	Hermaphrodites. Fertilization is internal, but cross-fertilization - two individuals are needed

Typical representatives of ciliary worms are planaria(Fig. 1).

Rice. one.Morphology of flatworms on the example of dairy planaria. A - the appearance of the planaria; B, C - internal organs (diagrams); D - part of the transverse section through the body of the dairy planaria; D - terminal cell of the protonephridial excretory system: 1 - oral opening; 2 - throat; 3 - intestines; 4 - protonephridia; 5 - left lateral nerve trunk; 6 - head ganglion; 7 - peephole; 8 - ciliary epithelium; 9 - circular muscles; 10 - oblique muscles; 11 - longitudinal muscles; 12 - dorsoventral muscles; 13 - parenchyma cells; 14 - cells forming rhabdites; 15 - rabdits; 16 - unicellular gland; 17 - a bunch of cilia (flickering flame); 18 - cell nucleus

general characteristics

Appearance and covers . The body of ciliary worms is elongated, foliate. Sizes vary from a few millimeters to several centimeters. Body colorless or white color. Most often ciliary worms dyed in different colors pigment embedded in the skin.

body covered single layer ciliated epithelium. The covers have skin glands scattered throughout the body or collected in complexes. Of interest is the variety of skin glands - rhabdit cells, which contain light-refracting rods rabdites. They lie perpendicular to the surface of the body. When the animal is irritated, the rhabdites are thrown out and swell greatly. As a result, mucus is formed on the surface of the worm, possibly playing a protective role.

Skin-muscular sac . Under the epithelium is basement membrane, which serves to give the body a certain shape and to attach muscles. The combination of muscles and epithelium forms a single complex - skin-muscle sac. The muscular system is made up of several layers smooth muscle fibers. The most superficial circular muscles, somewhat deeper longitudinal and the deepest diagonal muscle fibers. In addition to the listed types of muscle fibers, ciliary worms are characterized by dorso-abdominal, or dorsoventral, muscles. These are bundles of fibers running from the dorsal side of the body to the ventral side.

The movement is carried out due to the beating of the cilia (in small forms) or the contraction of the skin-muscular sac (in large representatives).

clearly defined body cavity ciliary worms do not. All gaps between organs are filled parenchyma- loose connective tissue. The small spaces between the parenchyma cells are filled with an aqueous liquid, due to which the transfer of products from the intestine to the internal organs and the transfer of metabolic products to the excretory system can be carried out. In addition, the parenchyma can be considered as a supporting tissue.

Digestive system ciliary worms blindly closed. Mouth also serves for swallowing food, and for throwing out undigested food. The mouth is usually located on the ventral side of the body and leads to throat. In some large ciliary worms, such as freshwater planaria, the mouth opening opens into pharyngeal pocket, in which is muscular throat, able to stretch and protrude out through the mouth. midgut in small forms of ciliary worms is channels branching in all directions, and in large forms, the intestines are represented three branches: one front, going to the front end of the body, and two rear running along the sides to the posterior end of the body.

Main Feature nervous system ciliary worms compared to coelenterates is concentration of nerve elements at the anterior end of the body with the formation of a double node - the brain ganglion, which becomes the coordinating center of the whole body. depart from the ganglion longitudinal nerve trunks connected by transverse ring jumpers.

sense organs ciliary worms are relatively well developed. organ of touch whole skin serves. In some species, the function of touch is performed by small paired tentacles at the anterior end of the body. Sense organs of balance represented by closed sacs - statocysts, with hearing stones inside. organs of vision are almost always available. The eye may be one pair or more.

excretory system first appears as separate system. It is represented two or multiple channels, each of which one end opens outwards, a the other is strongly branched, forming a network of channels of various diameters. The thinnest tubules or capillaries at their ends are closed by special cells - stellate(see fig. 1, D). From these cells in the lumen of the tubules depart bunches of cilia. Thanks to them permanent job there is no stagnation of fluid in the body of the worm, it enters the tubules and is subsequently brought out. The excretory system in the form of branched canals, closed at the ends by stellate cells, is called protonephridia.

reproductive system quite varied in structure. It can be noted that in comparison with coelenterates in ciliary worms special excretory ducts appear for

expelling germ cells. Eyelash worms hermaphrodites. Fertilization - internal.

Reproduction. In most cases in a sexual way. For most worms direct development, but some marine species development occurs with metamorphosis. However, some ciliary worms can reproduce and asexually through transverse fission. At the same time, in each half of the body, regeneration missing organs.

Number of species: about 25 thousand.

Habitat: They live everywhere in humid environments, including the tissues and organs of other animals.

Structure: Flatworms are the first multicellular animals that evolved bilateral symmetry, three-layer, real organs and tissues.

Bilateral(bilateral) symmetry - this means that an imaginary axis of symmetry can be drawn through the animal's body, while the right side of the body will be a mirror image of the left.

During embryonic development, three-layer animals are laid three layers of cells: outer - ectoderm, average - mesoderm, internal - endoderm. Certain organs and tissues develop from each layer:

from the ectoderm, the skin (epithelium) and the nervous system are formed;

from the mesoderm - muscle and connective tissues, reproductive, excretory systems;

from the endoderm - the digestive system.

In flatworms, the body is flattened in the dorsal-abdominal direction, there is no body cavity, the space between internal organs filled with mesoderm cells (parenchyma).

Digestive system includes the mouth, pharynx and blindly closed intestine. The absorption of food and the excretion of undigested residues occurs through the mouth. Tapeworms have no digestive system at all. nutrients they absorb the entire surface of the body, being in the intestines of the host.

excretory organs - protonephridia. They consist of thin branching tubules, at one end of which are fiery (flickering) cells star-shaped, immersed in the parenchyma. A bundle of cilia (flickering flame) departs inside these cells, the movement of which resembles the flickering of a flame (hence the name of the cells). Flame cells capture liquid decay products from the parenchyma, and cilia drive them into the tubule. The tubules open on the surface of the body with an excretory pore through which decay products are removed from the body.

Nervous system ladder type ( orthogon). It is formed by a large head paired ganglion (ganglion) and six nerve trunks extending from it: two on the ventral side, two on the dorsal and two on the sides. Nerve trunks are interconnected by jumpers. From the ganglion and trunks, nerves depart to the organs and skin.

Reproduction and development:

Flatworms are hermaphrodites. Sex cells mature in the sex glands (gonads). Hermaphrodite has both male glands - testes, and female - ovaries. Fertilization is internal, usually cross, i.e. worms exchange seminal fluid.

CLASS CILIATION WORMS

Dairy planaria, a small aquatic animal, the adult has a length of ~25 mm and a width of ~6 mm, the body is flat, milky white. At the front end of the body are two eyes that distinguish light from darkness, as well as a pair of tentacles (chemical sense organs) necessary for finding food. Planarians move, on the one hand, thanks to the work of the cilia covering their skin, on the other hand, due to the contraction of the muscles of the skin-muscular sac. The space between the muscles and internal organs is filled with parenchyma, in which intermediate cells responsible for regeneration and asexual reproduction.

Planarians are carnivores that feed on small animals. The mouth is located on the ventral side, closer to the middle of the body, from it comes a muscular pharynx, from which three branches of a closed intestine depart. Having captured the victim, the planaria sucks out its contents with its throat. Digestion occurs in the intestine under the action of enzymes (intestinal), intestinal cells are able to capture and digest pieces of food (intracellular digestion). Undigested food remains are removed through the mouth.

Reproduction and development. Ciliary - hermaphrodites. Cross fertilization. Fertilized eggs fall into a cocoon, which the worm lays on underwater objects. The development is direct.

CLASS FLUES

4 - sporocyst; 5 - redia; 6 - cercariae; 7 - adolescarium.

CLASS TAPE WORMS

Bull tapeworm- a tapeworm, reaches a length of 4 to 12 meters. The body includes a head with suckers, a neck and a strobile - a tape of segments. The youngest segments are at the neck, the oldest are sacs filled with eggs, located at the posterior end, where they come off one by one.

Reproduction and development. Bull tapeworm is a hermaphrodite: in each of its segments there is one ovary and many testes. Both cross-fertilization and self-fertilization are observed. The posterior segments, filled with mature eggs, open and, with feces, are brought out. Cattle (intermediate host) can swallow eggs along with grass, in the stomach microscopic larvae with six hooks come out of the eggs, which enter the bloodstream through the intestinal wall and spread throughout the body of the animal and enter the muscles. Here the six-hooked larva grows and turns into Finn- a vial, inside of which there is a tapeworm head with a neck. A person can become infected with fincas by eating undercooked or undercooked meat from an infected animal. In the human stomach, a head emerges from the finca, which is attached to the intestinal wall. New segments bud from the neck - the worm grows. Bull tapeworm emits toxic substances that cause intestinal disorders and anemia in humans.

Development pork tapeworm has a similar character, its intermediate owner, in addition to a pig and a wild boar, can also be a person, then Finns develop in its muscles. Development wide ribbon is accompanied by a change of two intermediate hosts: the first is a crustacean (cyclops), the second is a fish that has eaten a crustacean. The definitive host may be a human or a predator that has eaten the infected fish.

New concepts and terms: mesoderm, skin-muscular sac, tegument, hypodermis, reduction, protonephridia (flame cells), orthogon, strobilus, ganglion, gonads, hermaphrodite, direct and indirect development, definitive and intermediate host, miracidium, cercaria, finna, segment, armed and unarmed tapeworm.

Questions for reinforcement.

1. Who is called the intermediate host? final?

6. Why is it dangerous to drink raw water, swim in ponds near livestock grazing? Why is it important to wash your hands with soap after interacting with animals?

7. For which worms is oxygen harmful?

8. What aromorphoses led to the appearance of the type Flatworms?

Lectures on zoology

Type Roundworms

Answer plan:

General characteristics of roundworms

The structure of the body of Ascaris human

Reproduction and development of Ascaris human

Classification of roundworms, variety of species

The value of roundworms in nature and human life

Structural features Bilaterally symmetrical - a single cavity of symmetry divides the body into left and right halves. Development occurs from three germ layers: ectoderm, endoderm and mesoderm. The third germ layer appears for the first time in the course of evolution and gives rise to the development of parenchymal cells that fill the gaps between the organs and the muscular system. Left half Right half

Structural features Body sizes from 2-3 mm to 20 m. The body is elongated and flattened in the dorsal-abdominal direction; has a ribbon-like or leaf-like shape. The presence of developed organ systems is characteristic: muscular, digestive (absent in ribbon), excretory nervous and sexual.

Integuments of the body and the muscular system The cells of the epithelium and muscles are separate formations. The skin-muscle sac consists of a single-layer epithelium (in aquatic forms, the epithelium has cilia) and three layers of smooth muscles: annular, longitudinal, and oblique). Some representatives also have dorso-abdominal muscles. Movement is provided by muscle contraction (flukes and tapeworms) or by cilia of the integumentary epithelium and muscle contraction (ciliary worms).

The digestive system has two sections - anterior (mouth, pharynx) and middle (intestinal branches). The intestine is closed blindly, the posterior intestine and anus are absent. Undigested food remains are removed through the mouth. Tapeworms have no digestive system (represented by separate digestive cells).

Excretory system Formed by a system of tubules, one end of which begins in the parenchyma with a stellate cell with a bundle of cilia, and the other flows into the excretory duct. The duct unites into one or two common channels, ending in excretory pores.

Nervous system. Sense organs. It consists of supraglottic ganglions (ganglia) and longitudinal nerve trunks that run along the body and are connected by transverse nerve bridges. Sense organs - touch and chemical sense. Free-living people have organs of touch and balance.

Hepatic fluke Hepatic flukes, usually up to 3 cm long, 1.3 cm wide. Hepatic flukes of the order Opisthorchis cause opisthorchiasis, early symptoms - liver enlargement, allergic reactions and gastrointestinal disturbances; late stage symptoms - pain radiating to the back, biliary colic, headaches and dizziness, insomnia. Treatment is with anthelmintic, choleretic and enzyme preparations. High frequency electromagnetic radiation is also used.

Development cycle The life cycles of different genera are different. In species of the genus Fasciola, development occurs with one intermediate host (freshwater snail), and infection of the final host occurs when swallowed with water or eaten with coastal plants of the resting stage - adolescaria. In species of the genera Opisthorchis and Clonorchis, the second intermediate host is freshwater fish, and infection of the final host occurs by eating raw fish with invasive stages. In species of the genus Dicrocoelium, terrestrial lung snails and ants serve as intermediate hosts, and infection of the final host (usually a herbivore) occurs when an infected ant is eaten with grass.

Bull tapeworm (tapeworm) It affects cattle and humans, causing teniarinhoz. Infection with bovine tapeworm is especially common in equatorial Africa, Latin America, in the Philippines and parts of Eastern Europe. An adult bull tapeworm consists of more than 1000 segments and reaches 4-40 meters in length. The laying of the reproductive apparatus begins at about the 200th segment. Length of mature proglottids mm, width 5-7 mm. The scolex (head section) is equipped with 4 suckers without hooks (therefore unarmed). The life span of bovine tapeworm in the human intestine, if no deworming measures are taken, is years. A tapeworm produces ~ 600 million eggs per year, ~ 11 billion in a lifetime.

Development cycle Segments containing eggs are excreted from the human intestine (the main host). Together with the grass, they enter the stomach of the cow (intermediate host). Six hooked larvae emerge from the eggs, which penetrate into the blood vessels of the intestine and then into the muscles. In the muscles, the larva turns into Finns (a vial with a tapeworm head inside). When a person eats poorly processed finny meat, the tapeworm head attaches to the intestinal wall and begins to produce segments.

Structural features Bilaterally symmetrical. Sizes from a few micrometers (soil) to several meters (sperm whale nematode). They have a non-segmented body with a dense cuticle. The ciliary cover is partially or completely reduced. Body filiform, fusiform, non-segmented, round in cross section.

The digestive system is formed by the anterior, middle and hindgut. The foregut is differentiated into sections: mouth with cuticular lips, pharynx and esophagus. The middle and hindgut are not divided into sections. The digestive tract ends at the anus.

The excretory system is represented by 1-2 skin glands (modified protonephridia). These are large cells, from which two channels depart on the sides of the cell. At the posterior end of the body, the channels end blindly, and in front they open into the external environment with an excretory pore.

Nervous system. Sense organs Ladder-type nervous system. It is represented by the head nerve nodes (ganglia), the peripharyngeal nerve ring and several nerve trunks (dorsal and abdominal), median transverse bridges. The sense organs are represented by the organs of touch and chemical sense. Marine forms have light-sensitive receptors. Scheme of the roundworm nervous system: 1 - oral papillae with tactile endings and the nerves innervating them, 2 - peripharyngeal nerve ring, 3 - lateral head ganglia, 4 - abdominal nerve trunk, 5 - lateral nerve trunks, 6 - ring nerves, 7 - posterior ganglion , 8 - sensitive papillae with corresponding nerves, 9 - anus, 10 - dorsal nerve trunk

Ascaris human Ascarids are large roundworms, their length can reach 40 centimeters. Most often affect the organs of the gastrointestinal tract, causing ascariasis. The favorite habitat of adults is the small intestine. Roundworms are bisexual worms. Ascaris females can produce more than 200 thousand eggs per day. Fertilized eggs from the human intestine enter the soil. They develop larvae. Infection occurs when drinking water from open reservoirs, eating poorly washed vegetables, fruits that have eggs with larvae. In the human body, the larva migrates: once in the intestine, it perforates its walls and enters the blood stream.

Structural features Bilateral symmetry of the body. Sizes from 0.5 mm to 3 m. The body is divided into the head lobe, trunk and anus. The polychaetes have a separate head with eyes, tentacles and antennae. The body is segmented (external and internal segmentation). The trunk contains from 5 to 800 identical ring-shaped segments. The segments have the same external and internal structure(metamerism) and perform similar functions. The metameric structure determines a high degree regeneration.

Integuments of the body and muscular system The body wall is formed by a skin-muscular sac, consisting of a single-layer epithelium covered with a thin cuticle, two layers of smooth muscles (outer annular and inner longitudinal) and a single-layer epithelium of the secondary body cavity. With the contraction of the circular muscles, the body of the worm becomes long and thin, with the contraction of the longitudinal muscles, it shortens and thickens.

Body cavity Secondary - whole (has an epithelial vystilka). In most, the body cavity is divided by transverse partitions corresponding to body segments. The cavity fluid is a hydroskeleton and an internal environment; it is involved in the transport of metabolic products, nutrients and reproductive products.

The digestive system consists of three sections: anterior (mouth, muscular pharynx, esophagus, goiter), middle (tubular stomach, midgut) and posterior (hindgut, anus). The glands of the esophagus and midgut secrete enzymes to digest food. Absorption occurs in the midgut.

The circulatory system is closed. There are two vessels: dorsal and abdominal, connected in each segment by annular vessels. Through the dorsal vessel, blood moves from the posterior end of the body to the anterior, along the abdominal vessel from front to back. The movement of blood is carried out due to the rhythmic contractions of the walls of the spinal vessel and the annular vessels ("heart") in the pharynx. Many people have red blood.

The excretory system is of the Metanephidial type. Metanephridia look like tubes with funnels, two in each segment. The funnel, surrounded by cilia, and convoluted tubules are in one segment, and a short tubule that opens outwards with an opening - an excretory pore - is in the next segment.

Nervous system. Sense organs. It is represented by supraesophageal and subpharyngeal nerve nodes (ganglia), which are connected to the peripharyngeal nerve ring and the abdominal nerve chain, consisting of paired nerve nodes in each segment, connected by longitudinal and transverse nerve trunks. Polychaetes have organs of balance and vision (2-4 eyes). Most have only olfactory, tactile, and light-sensitive cells.

Reproduction and development Soil and freshwater forms are mainly hermaphodites. Sex glands develop only in certain segments. Insemination is internal. The type of development is direct. Asexual reproduction is carried out by budding and fragmentation (due to regeneration). Marine representatives are dioecious. Development with metamorphosis, trochophore larva.

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:

Flukes.
Tape.
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:

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. flatworms, possessing a tegument, 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 digesting, flatworms are 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 belonged to coelenterates, which subsequently ate the 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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