The habitat of flatworms is brief. Type Flatworms

Rishta subcutaneous worm

There are worms living in human blood. These include schistosomes. Their main habitat is blood vessels. However, they are able to penetrate into various organs, causing symptoms of damage to the genitourinary system, liver, and kidneys.

Some helminth larvae may be in the blood. For example, in tapeworms this is how they spread throughout the organism of the intermediate host. With the blood flow, the larvae migrate to various organs, where they fix and form cysts containing the heads of adult worms. The latter, when they enter the digestive tract of the final host, attach to the intestinal wall, giving rise to a sexually mature individual.

Flatworms: general characteristics

The body of flatworms is capable of performing complex and varied movements.

All flatworms have common structural features:

• The outer cover is represented by the cuticle. In free-living individuals, it is covered with cilia, the surface of the body of the worms is usually smooth.
• Several layers of muscle fibers are located under the outer cover.
• There is no body cavity.
• The digestive system has only one opening - the mouth. The intestine ends blindly. Some worms have no digestive organs at all. So, tapeworms, which absorb nutrients throughout the body from the lumen of the host's intestine, do not need them.
• There is no circulatory system and no blood, as well as respiratory organs.
• The excretory system is represented by a network of tubes that permeate the entire body.
• The nervous system is primitive. There are several ganglia near the pharynx, from which nerve trunks connected by jumpers extend. The sense organs are formed only in free-living individuals and some worms at the larval stages of development.

The system that is really well developed is the reproductive system. Flat worms- hermaphrodites. Reproduction is possible with the participation of 2 individuals or by self-fertilization.

Suckers

The developmental cycle of trematodes is one of the most difficult. Miracidia emerge from eggs that enter the external environment. In water, the latter feel comfortable and exist for some time as free-living organisms. The next stage is the introduction of miracidia into the first intermediate host. The larva does this using a special cutting device on the head. The mollusk usually becomes the host.

Their life cycle can take place in several hosts and is accompanied by a regular alternation

Here miracidium turns into a sporocyst, which gives rise to the next stage of the development cycle - redia. Those, in turn, are the predecessors of cercariae, which leave the intermediate host and re-enter the aquatic environment. Further, the development cycle follows one of two options. Cercariae are transformed into cysts directly in the external environment (attached to algae) or in the body of a second intermediate host (mollusk, fish, amphibian).

These are the longest worms with a transparent shell.

Infection of the final host occurs when it eats infected organs of the intermediate. The developmental cycle ends with the attachment of the cyst head to the intestinal wall and the development of an adult worm. The latter can reach significant sizes (for example, a wide ribbon grows up to 10 m long).

Human for flukes is the final host, but for tapeworms it can be intermediate.

What symptoms occur when a person is infected with a helminth? The clinic of the disease is primarily due to which organ is affected. Sexually mature worms usually live in the intestines, therefore, in the general picture of the disease, symptoms characteristic of digestive disorders prevail: nausea, gas formation, stool disturbances, and abdominal pain.

Helminths secrete waste products, which, entering the bloodstream, cause poisoning and symptoms of intoxication (fever, fatigue, and others). In addition, they are perceived by the immune system as an allergen. Therefore, helminthiases are often accompanied by symptoms of an allergic reaction (skin rash, itching).

Structural features Bilaterally asymmetric - the only 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 dimensions 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 tape), excretory nervous and sexual.

The integument of the body and the muscular system The cells of the epithelium and muscles are separate formations. The musculocutaneous 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 dorsal-abdominal muscles. Movement is provided by muscle contraction (flukes and tapeworms) or by cilia of the integumentary epithelium and muscle contraction (ciliary worms).

Digestive system Has two sections - front (mouth, pharynx) and middle (bowel branches). The intestine is closed blindly, the posterior part of the intestine and the anus are absent. Undigested food debris is removed by mouth. In tapeworms, the digestive system is absent (represented by individual 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 is united into one or two common channels, ending with excretory pores.

Nervous system. Sense organs. Consists of the supraopharyngeal 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 flukes Hepatic flukes, usually 3 cm long and 1.3 cm wide. Hepatic flukes of the Opisthorchis order cause opisthorchiasis, symptoms early stage- enlarged liver, allergic reactions and gastrointestinal disorders; late stage symptoms - back pain, bilious colic, headaches and dizziness, insomnia. Treatment is carried out with anthelmintic, choleretic and enzyme preparations. High frequency electromagnetic radiation is also used.

Development cycle Life Cycles 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 dormant stage - adolescaria. In the species of the genera Opisthorchis and Clonorchis, freshwater fish is the second intermediate host, and infection of the final host occurs when raw fish with invasive stages are consumed. 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.

Bovine tapeworm (tapeworm) Affects cattle and humans, causing teniarinhoses. Bovine tapeworm infection is especially common in equatorial Africa, Latin America, in the Philippines and in some parts of Eastern Europe... An adult bovine tapeworm consists of more than 1000 segments and reaches 4-40 meters in length. The laying of the genital apparatus begins from about the 200th segment. The length of mature proglottids is mm, the width is 5-7 mm. The scolex (head section) is equipped with 4 suction cups without hooks (therefore unarmed). The life span of a bovine tapeworm in the human intestine, if no deworming measures are taken, is years. For a year, tapeworm produces ~ 600 million eggs, in a lifetime ~ 11 billion.

Development cycle Segments containing eggs are released from the human intestine (the main host). Together with the grass, they enter the cow's stomach (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 phynose meat, the head of the tapeworm attaches to the intestinal wall and begins to produce segments.

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

Digestive system Formed by the anterior, middle and hind gut. The anterior gut is differentiated into sections: the mouth with cuticular lips, the pharynx and the esophagus. The middle and hind gut are not divided into sections. The digestive tract ends with the anus.

Excretory system Presented by 1-2 cutaneous glands (modified protonephridia). These are large cells, from which two channels extend on the sides of the cell. At the posterior end of the body, the channels end blindly, and in the front they open into the external environment by the excretory pore.

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

Human Ascaris Ascaris are large round worms, their length can reach 40 centimeters. The organs of the gastrointestinal tract are most often affected, causing ascariasis. The preferred habitat for adults is the small intestine. Roundworm bisexual worms. Ascaris females can produce more than 200 thousand eggs per day. Fertilized eggs from the human intestine enter the soil. Larvae develop in them. Infection occurs when drinking water from open reservoirs, eating poorly washed vegetables, fruits, which have eggs with larvae. In the human body, the larva migrates: once it enters the intestine, it bores its walls and enters the bloodstream.

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

Body integument and muscular system The body wall is formed by the skin-muscular sac, consisting of a single-layer epithelium covered with a thin cuticle, two layers of smooth muscles (external annular and internal longitudinal) and a single-layer epithelium of the secondary body cavity. With the contraction of the annular 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 (it has epithelial vyzylka). In most, the body cavity is divided by transverse septa corresponding to the 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.

Digestive system Consists of three sections: anterior (mouth, muscular pharynx, esophagus, goiter), middle (tubular stomach, middle intestine) and posterior (hind intestine, anus). The glands of the esophagus and midgut secrete enzymes to digest food. Absorption takes place in the midgut.

Circulatory system 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 one, along the abdominal end from front to back. The movement of blood is carried out due to the rhythmic contractions of the walls of the dorsal vessel and the annular vessels ("heart") in the pharynx. Many have red blood.

Excretory system Metanephidial type. Metanephridia look like tubes with funnels, two in each segment. The funnel, surrounded by cilia, and the convoluted tubules are in one segment, and the short tubule opening outward with an opening - excretory pore - is in the adjacent segment.

Nervous system. Sense organs. It is represented by the supraopharyngeal and subopharyngeal nerve nodes (ganglia), which are connected to the periopharyngeal nerve ring and the abdominal nerve chain, consisting of paired nerve nodes in each segment, connected by longitudinal and transverse nerve trunks. Polychaetae 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. The sex glands only develop 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.

Let's start the description with a little grimace worms... What can you 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 bilayers has led to significantly more perfect forms organisms with a three-layer body structure. And here nature had to tinker for a long time, creating not one, but whole.

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

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

……………… Type Flatworms (three-layer)

…………………………………. K l ... but. from. from. s

__________________________________________________________________________________

.. Ciliated worms ……………………… .. Flukes ……………………… .. Tapeworms

___________________________________________________________________________________

White planaria…. Liver fluke …… …………… Bovine tapeworm __________________________________________________________________________________

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

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

……..
Structure: bilaterally symmetric ... For the first time in embryos, the third germ layer – mesodermfrom which parenchymal cells and the muscular system develop. Body flattened.

………..
Body integuments and muscular system: musculocutaneous sac - from unilamellar epithelium (can be with cilia) and three layers smooth muscles (annular, longitudinal and oblique).

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

Body cavity: absent , internal organs are located inparenchyma.

Digestive system:has two sections - anterior (mouth, pharynx) and middle (branches intestines). The gut is closed no anus and food debris is removed through the mouth... The tapedigestive system worms 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 begins in the parenchyma star cage with a bundle of cilia, and the other flows into excretory duct. Ducts are combined into one or two common channels ending in excretory pores. Elementary unit of the system areprotonephridia.

Nervous system:of supraopharyngeal ganglia(ganglia) and longitudinal nerve trunks, related cross bridges(ladder type).

Senses: touch and chemosensitive cells... Free living have organsvision and balance.…………..

Reproductive system: to As a rule, hermaphrodites.Mensreproductive system: testes, vas deferens, ejaculatory duct and copulatory organ... Womensreproductive system: ovary, oviduct, uterus, vitelline.

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

***************************************

Who has questions about the article to biology tutor via Skype, comments, suggestions - please in the comments .

Number of species: about 25 thousand.

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

Structure: Flatworms are the first multicellular animals in which, in the course of evolution, bilateral symmetry, three-layer structure, real organs and tissues appeared.

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 mirror-like to the left.

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

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

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

from the endoderm - the digestive system.

In flatworms, the body is flattened in the dorsal-abdominal direction, the body cavity is absent, the space between the internal organs is filled with mesoderm cells (parenchyma).

Digestive system includes the mouth, pharynx and cecum. Food absorption and undigested residues are excreted through the mouth. In tapeworms, the digestive system is completely absent, they absorb nutrients from 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 there are fiery (ciliated) cells stellate, immersed in the parenchyma. A bundle of cilia (flickering flame) leaves inside these cells, the movement of which resembles a flickering flame (hence the name of the cells). Flame cells capture liquid decay products from the parenchyma, and the cilia drive them into the tubule. The tubules open on the surface of the body by an excretory pore through which waste products are removed from the body.

Nervous system ladder type ( orthogon)... It is formed by a large head paired nerve node (ganglion) and six nerve trunks extending from it: two on the ventral side, two on the dorsal and two on the sides. The nerve trunks are interconnected by jumpers. Nerves extend from the ganglion and trunks to 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-fertilization, i.e. worms exchange seminal fluid.

CLASS CILIA WORM

Milk planaria, a small aquatic animal, an adult is ~ 25 mm long and ~ 6 mm wide, 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) needed to search for food. Planarians move, on the one hand, thanks to the work of the cilia covering their skin, on the other hand, thanks 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 they meet intermediate cells responsible for regeneration and asexual reproduction.

Planarians are predators that feed on small animals. The mouth is on the ventral side, closer to the middle of the body, from it there is a muscular pharynx, from which three branches of a closed intestine depart. Capturing the victim, the planaria sucks out its contents by throat. In the intestine, digestion occurs under the action of enzymes (intestinal), intestinal cells are able to capture and digest pieces of food (intracellular digestion). Undigested food debris is removed by mouth.

Reproduction and development... Ciliates are hermaphrodites. Fertilization is cross. Fertilized eggs fall into a cocoon, which the worm lays on underwater objects. Direct development.

PUCKER CLASS

4 - sporocyst; 5 - redia; 6 - cercarium; 7 - adolescarian.

TAPE CLASS

Bovine tapeworm- tapeworm, reaches a length of 4 to 12 meters. The body includes a head with suction cups, a neck and a strobila - 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... The bovine tapeworm is 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 removed. Cattle (an intermediate host) can swallow eggs along with grass; in the stomach, microscopic larvae with six hooks emerge from the eggs, which enter the bloodstream through the intestinal wall and are carried throughout the animal's body and are carried into the muscles. Here the six-hooked larva grows and turns into finnu- a bubble, inside which there is a chain head with a neck. A person can become infected with Finns by eating insufficiently cooked or cooked meat from an infected animal. In the human stomach, a head comes out of the fin, which is attached to the intestinal wall. New segments bud off from the neck - the worm grows. Bovine tapeworm releases 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 his muscles. Development wide tape accompanied by a change of two intermediate hosts: the first is a crustacean (cyclops), the second is a fish that ate the crustacean. The final host can be a human or a predator who ate the infected fish.

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

Questions for consolidation.

1. Who is called the intermediate host? Final?

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

7. For which worms is oxygen harmful?

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

Zoology lectures

Type Roundworms

Response plan:

· general characteristics Round worms

The structure of the body of Ascaris human

Reproduction and development of Ascaris human

Roundworm classification, variety of species

The importance of roundworms in nature and human life

a brief description of

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

Fig. one.The morphology of flatworms on the example of milk planaria. A - the appearance of the planaria; B, C - internal organs (diagrams); G - part of the cross section through the body of the milk planaria; D - terminal cell of the protonephridial excretory system: 1 - oral opening; 2 - pharynx; 3 - intestines; 4 - protonephridia; 5 - left lateral nerve trunk; 6 - head nerve node; 7 - peephole; 8 - ciliary epithelium; 9 - circular muscles; 10 - oblique muscles; 11 - longitudinal muscles; 12 - dorsoventral muscles; 13 - cells of the parenchyma; 14 - cells that form rhabdites; 15 - rhabdits; 16 - unicellular gland; 17 - a bundle of cilia (flickering flame); 18 - cell nucleus

general characteristics

Appearance and integuments . The body of ciliary worms is elongated in length, leaf-shaped... Sizes range from a few millimeters to several centimeters. The body is colorless or white... Most often, ciliary worms are colored in different colors by grains pigment lying in the skin.

Body covered monolayer ciliated epithelium... The covers have skin glands scattered throughout the body or collected in complexes. Of interest are a variety of skin glands - rhabdite cells containing light-refracting sticks rhabdites... 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 forms on the surface of the worm, possibly playing a protective role.

Musculocutaneous sac . Under the epithelium is basement membrane, which serves to give the body a certain shape and for the attachment of muscles. The set of muscles and epithelium forms a single complex - musculocutaneous sac... The muscular system is composed of several layers smooth muscle fibers... Most superficially located annular muscles, a little deeper - longitudinal and the deepest - diagonal muscle fibers... In addition to the listed types of muscle fibers, ciliary worms are characterized by dorsal-abdominal, or dorsoventral, muscle... 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 contraction of the skin-muscle sac (in large representatives).

Clearly expressed body cavity ciliary worms do not. All gaps between organs are filled parenchyma- loose connective tissue. Small spaces between the cells of the parenchyma are filled with an aqueous humor, so that the transfer of products from the intestine to internal organs and the transfer of metabolic products to the excretory system. In addition, the parenchyma can be considered as a supporting tissue.

Digestive system ciliary worms blind-closed. Mouth serves also for swallowing food, and for throwing away undigested food debris... The mouth is usually located on the abdominal side of the body and leads to throat... In some large ciliary worms, for example, in freshwater planaria, the mouth opens into pharyngeal pocket in which there is muscular pharynx capable of stretching and protruding through the mouth outward. Middle intestine in small forms of ciliary worms is canals branching in all directions, and in large forms the intestine is presented three branches: one front going to the front end of the body, and two back running laterally to the posterior end of the body.

Main feature nervous system ciliary worms in comparison with coelenterates is concentration of nerve elements at the anterior end of the body with the formation of a double node - the cerebral ganglion which becomes the coordinating center of the whole body... From the ganglion depart longitudinal nerve trunks connected by transverse ring bridges.

Sense organs in ciliary worms they are relatively well developed. Organ of touch all skin serves. In some species, the function of touch is performed by small paired tentacles of the anterior end of the body. Balance sense organs represented by closed sacs - statocysts, with auditory stones inside. Organs of vision are almost always available. The eye can be one pair or more.

Excretory system for the first time appears as separate system ... She is presented two or multiple channels, each of which one end opens outward, but the other branches heavily forming a network of channels of various diameters. The thinnest tubules or capillaries at their ends are closed with special cells - star-shaped(see fig. 1, D). From these cells into the lumen of the tubules depart cilia bundles... Due to their constant work, there is no stagnation of fluid in the body of the worm, it enters the tubules and is subsequently removed to the outside. The excretory system in the form of branched canals closed at the ends by stellate cells is called protonephridia.

Reproductive system the structure is quite diverse. It can be noted that in comparison with coelenterates in ciliary worms special excretory ducts appear for

removing germ cells to the outside. Ciliary worms hermaphrodites. Fertilization - internal.

Reproduction. In most cases sexually. Most worms direct development, but some marine species development occurs with metamorphosis. However, some ciliary worms can multiply and asexual way through transverse division. Moreover, in each half of the body there is regeneration missing organs.