Killed worms: general type characteristic. Ring Worms (characteristics and structure)

For the type of ring worms include primary animals, the most highly organized from all worms. The type includes, according to various sources, 10-18 thousand species and is divided into three classes: multi-minded (the most numerous, more than 10 thousand species), non-timing and leeches. These worms live in reservoirs, not excluding the oceanic bottom and ice water of the Atlantic, and in the soil. The exceptions are several types of leeches that have adapted to ground accommodation in wet forests of tropics. Well, the most famous and familiar in our latitudes by unauthorized worms are the rain, named so for the custom of friendly, dozens, crawl out of the soil during the rain to enhance with oxygen. In addition, their presence is given to small buccorki-strip, especially well-visible in spring, - young worms explode soil, passing by her oxygen. We will talk about rainwrites further in more detail, and now we will consider important aromorphoses and the features of the structure of ringed worms.

Aromorphosis of ringed worms

1. Whole - secondary body cavity, that is, a closed, liquid-filled space separating the intestines from the walls of the body. It is important to emphasize that, unlike the primary cavity of round worms, the whole ringed has an epithelial shell, a liner. Multi-and-timing worms have a completely large volume. In the filling fluid, the cells participating in excretory, gas exchange and other processes are freely floating.

2. Closed circulatory system - Her emergence is directly related to the advent of the organizer. As the larvae develops the worm, the secondary cavity displaces the primary, the remains of which are converted into blood vessels.

3. Metamerism - Segmentation, duplication of internal organs, thanks to which loss of body parts for a worm is not critical. Each ring has its own sex glands, excretory organs, nervous nodes, etc.

4. Parapody - contributing to movement grows on the sides of the body in multi-art.

The structure of the ringed worms

1. Body sizes from a quarter millimeter to three and even more than a meter.

2. In cross section, the body is close to a circle or oval. Three departments are distinguished: head (head blade), torso and anal blade. Ring worms grow by forming new segments in the anal blade area.

2. The body is segmented by halves to many homogeneous rings (segments). It is important that the whole also has partitions, in accordance with the outer division. Upper layer skin-muscular bag - Cuticula, the next - one-layer epithelium. Muscles of two types, outside ring, are deeply lying on.

3. On the head, in addition to the mouth of the opening, there may be eyes, the touch bodies (a variety of mustache, peppers, etc.).

4. From the cuticle grow scheduleswhich can be very much over the entire length of the body.

System organs

1. Digestive system Not closed, it divides on three departments presented by the front, medium (here the nutrients are absorbed) and the rear integral. Some kinds of worms have acquired salivary glands.

2. Ring worms are heartless creatures, in their closed blood system There are only different types of vessels by which blood moves. Interestingly, the red color of the blood is not required - it all depends on pigments.

3. Breath It can be carried out in two ways - or the surface of the body (like non-timing worms and leeches), or by means of primitive gills, which are on Parapodiye's growing (in multi-pectic worms).

4. Nervous system It begins in the head of the worm, where two nerve ganglium, the durable and sodylum, connected by heavy, are formed by a blocking nervous ring. From Ganglia under the throat, it turns out and stretches along the body of a pair of nervous trunk with ganglions connected by jumpers in each segment. This is the so-called abdominal nervous chain.

5. Sense organs Pretty well developed in active worms: tactile cells, eyes (there are not all kinds), chemoreceptors, an equilibrium organ.

6. Selective system presented in all rings in pairs metanephridiev: Located in whole tubes that open on the surface of the body.

Origin of ring worms

1. The ancestors of ringed worms were free-lived flat worms. How can I prove it? The larvae of multi-minded worms have a great similarity with the planearies. What is it expressed? Throchofora, Larvae Multi-Point, has cilia, eyes, metanephrides in the form of tubes with star cells and a "flickering flame" formed by the bio of the cilia. In addition, the nervous system of Trophorm is very similar to the nervous system of the planarium.

2. Unauthorized occurred from the ancient multi-minded as a result of simplified in their structure caused by life in the thickness of the soil.

3. The leeches occurred from the ancient unauthorized worms.

Ring Worms are the most highly organized type of worms. Includes from 12 thousand (according to old sources) to 18 thousand (on new) species. According to the traditional classification, ringed worms include three classes: multi-art worms, unauthorized worms, leeches. However, according to another classification of multi-minded, considered in the rank of class, and unobtinka and leeches are included in the rank of subclasses to the class of the rigging; In addition to these groups, other classes and subclasses are also distinguished.

The length of the body of ringed worms, depending on the species varies from several millimeters to more than 5-6 meters.

In the process of embryonic development, Etoderma, Mesoderma and Entoderma are laid. Therefore, they are believed to three-layer animals.

In the ringed worms in the process of evolution, a secondary cavity of the body appeared, i.e. they are secondary-fibrous. The secondary cavity is called whole. It is formed inside the primary cavity, which remains in the form of cleavers of blood vessels.

Overall develops from mesoderm. Unlike the primary cavity, the secondary cavity is lined with its own epithelium. In the ring worms, the whole is filled with a liquid, which among others performs the function of the hydraulic oil (support for the shape and support when moving). Also, the numerical fluid carries nutrients, exchange and sex cells are displayed through it.

The body of ringed worms consists of their duplicate segments (rings, segments). In other words, their body is segmented. Segments can be a few or hundreds. The body cavity is not one, but is divided into segments by transverse partitions (septs) of the epithelial liner of the agencies. In addition, each ring forms two nominal bags (right and left). Their walls come into contact over and under the intestine and maintain the intestines. Between the walls also underlie the blood vessels and the nervous chain. In each segment there are nodes of the nervous system (on the paired abdominal nervous trunk), the selection organs, sex glands, outdoor grows.

The head blade is called a surgery. The rear of the body is an anal blade, or pygidy. Segmented body is called torso.

The segmented body allows the ring worms to grow easily at the expense of the formation of new rings (this is from behind before the anal blade).

The appearance of a segmented body is evolutionary progress. However, for ringed worms, a chomonal segmentation is characteristic when all segments are about the same. In more highly organized animals, segmentation is heteromon, when segments and their functions are different. At the same time, the collected worms are observed the formation of the head unit of the body by fusion of the front segments with a simultaneous increase in brain ganglium. This is called cephalization.

The walls of the body, as well as the lower worms, forms a skin-muscular bag. It includes a skin epithelium, a cooler layer and a layer of longitudinal muscles. Muscles achieve more powerful development.

There were paired movement organs - parapody. They are only in multi-minded ringed worms. They are growing a leather-muscular bag with bristle bundles. A more evolutionary advanced group of unauthorized parapody disappear, only bristles remain from them.

The digestive system consists of anterior, middle and rectory. The intestinal walls are formed by several layers of cells, they have muscular cells, thanks to which food moves. The front intestine is usually divided into a sip, esophagus, goiter and muscular stomach. Roth is on the abdominal side of the first segment of the body. Anal hole is located on the tail blade. The process of suction of nutrients into blood takes place in the middle intestine having a fold to increase the suction surface.

Characterized by a closed circulatory system. In the previous types of worms (flat, round) circulatory systems at all. As already mentioned, the clearance of blood vessels is the former primary body cavity, whose strip fluid began to perform blood functions. The circular black circular system consists of a spinal vessel (in which the blood moves from the tail blade to the head), from the abdominal vessel (blood moves from the head blade to the tail), a semi-colt, connecting the dorsal and abdominal vessel, small vessels that depart to various organs and tissues . In each segment there are two semiring (left and right). The closure of the circulatory system means that blood flows only by vessels.

Blood moves due to the pulsation of the walls of the spine vessel. Some non-timing worms, in addition to the dorsal, some ring vessels are reduced.

Blood tolerates the nutrients of their intestines and oxygen, which entered through the covers of the body. The respiratory pigment, reversible binding oxygen, is in the blood plasma, and is not contained in special cells, such as the vertebrate pigment hemoglobin is in red blood cells. Pigments in ringed worms can be different (hemoglobin, chlorocruarine, etc.), so blood color is not always red.

There are representatives of ringed worms that do not have a circulatory system (leech), but they have been reduced, and a breathing pigment is present in the tissue fluid.

Although the ringed worms do not have a respiratory system and usually breathe with the entire surface of the body, the transport of gases is carried out by a circulatory system, and not by diffusion through the tissue fluid. For some marine species on parapody, primitive gills are formed, in which there are many small blood vessels located close to the surface.

Allocation bodies are represented by metanephridia. These are tubes having a funnel with cilia at the end, located inside the body (in total). On the other hand, the tube opens out through the body surface. In each segment of the ring worm are two metanephridium (right and left).

The nervous system is more developed in comparison with round worms. In the head blade, a couple of spilled knots (ganglia) forms the semblance of a brain. Ganglia is located on the opening ring, from which the pair abdominal chain goes. It contains paired nerve nodes in each body segment.

The organs of the senses of ringed worms: tactile cells or structures, a number of species have eyes, chemical feelings (olfactory pits), there is an equilibrium organ.

Most of the collide worms separators, however, there is a hermaphrodite. The development is straightforward (small worm comes out of the egg) or with metamorphosis (the floating larva of the Throhofora comes out; characteristic of multi-singing).

It is believed that the ringed worms occurred from worms with an undusted body, similar to ciliated worms (type of flat worms). That is, in the process of evolution, two other worms groups occurred from the flat - round and ringed.

Killed worms are known from the Middle Cambrian period. It is believed that they originated from the lower flat worms, since certain features of their structure indicate the similarity of these groups of animals. Multi-point worms are isolated as the main class of the ringed type. From them later during the evolution in connection with the transition to the ground and freshwater lifestyle, there were unavoyallic, which gave rise to leeches.

All ringed worms have a characteristic structure. Basic characteristic: Their two-way-symmetric body can be divided into a head blade, segmented torso and rear (anal) blade. The number of body segments can reach from tens to several hundred. The dimensions vary from 0.25 mm to 5 m. Feeling organs are placed at the head end of the rings: eyes, olfactory cells and fishing pits, which respond to various chemical stimuli and perceive smells, as well as hearing organs that have a structure like locators. Feeling authorities can be located on tentacles. The body of ringed worms is divided into segments in the form of rings. Each segment in a certain sense is an independent part of the whole organism, since both (secondary body cavity) is divided by partitions into segments in accordance with the outer rings. Therefore, this type is assigned to this name - "Ring Worms". The value of such division of the body is huge. When damaged, the worm loses the contents of several segments, the remaining remains preserved, and the animal quickly regenerates. Metamer (segmentation) of internal organs, and, accordingly, system of ringed worms are due to segmentation of their bodies. The internal medium of the organism of the rings is a nuclear fluid that fills over in the skin-muscular bag, consisting of cuticle, skin epithelium and two muscle groups - ring and longitudinal. In the body cavity, the biochemical constancy of the internal environment is maintained, and transport, sexual, excretory, musculoskeletal function of the body can be realized. In more ancient multi-minded worms at each segment of the body there are parapody (paired primitive limbs with bristles). Some types of worms are moving due to muscle contraction, while others using parapody.

The river hole is on the abdominal side of the first segment. Digestive Ring Worms System Through. The intestine is divided into the front, middle and rear. The circular cruise cruise system is closed, consists of two main vessels - spinal and abdominal, which are interconnected by ring vessels like arteries and veins. Blood worms of this type can be of different colors from various types: red, green or transparent. It depends on the chemical structure of the respiratory pigment in the blood. The process of respiration is carried out by the entire surface of the body of the worm, but some kinds of worms have already gills. The excretory system is represented by pair protonphritis, metanephridia or mixonfritis (kidney samples) available in each segment. The nervous system of ring worms includes a large nervous ganglion (prototype of the brain) and the abdominal nerve chain of smaller ganglia in each segment. Most of the collected worms of dioceptions, but some recently developed hermaphroditism (like a rainwater worm and leech). Fertilization is carried out inside the body or in the external environment.

The value of the ringed worms is very large. It should be noted their important role in the food chains in the natural habitat. In the farm, people began to use sea types of rings as a feed base for growing valuable fishing fish species, for example sturgeon. The rainwill has long been used as a cavalry in fishing, like bird feed. The benefits of rain worms are enormous, as they are aimed and break the soil, which increases the crops of agricultural plants. In medicine, leeches in hypertension are widely used, increased blood clotting, as they highlight a special substance (giraudine), which has a property to reduce blood clotting and expand blood vessels.

More farmers of ancient Egypt saw in the rainwoods of the key to future yields. Aristotle called their intestines to land. And this is true: flowing through your intestine the land and plant residues, worms enrich the soil. In the 50s of our century, the question of the breeding of worms was arose specifically, as producers of very valuable, environmentally friendly fertilizer. The concept of "vermicultura" appeared - the culture of breeding worms. A red California worm was bred, which is used to create vermicultures. Biohumus can be breed both on an industrial scale and in the apartment, on the balcony and in the country area. "California" is a wonderful "pet." It can be lined up at home in a box made of wood or plywood, even in a cardboard, but from the inside of polyethylene, in a glass old aquarium, in a plastic box.

Now the topic of ringed worms is of particular interest, thanks to the latest studies of scientists who reveal all the new amazing abilities of these animals. For example, quite recently it became known that ringed worms are capable of distinguishing sharp corners. Another stunning ability is that most worms use their "photon installations" in order to disorient opponents. Cerves in the food pyramid of the ocean occupy one of the lower steps, serving for a wide variety of organisms - cephalters, crabs, crabs, fish, and even aggressive philicheets.

Ring worm. Photo: Chanabun R, Sutcharit C, Tongkerd P, Panha S

When a predator attacks the polyhetete and begins to break and torment her body, the cauldrop of the worm flashes brightly, attracting the attention of the "aggressor". The luminous part of the body is enough, and the second (head) is hidden in the dark. Subsequently, the tail from the worm reveals again. It turns out that the ringed worms long before the lizards were inventors of a dexterous trick with a tail discarded.

The object of study of this course work is the type of ring worms. A brief description of this type of worms features the organization of ringed worms. In the practical part of the work, such classes of this type were considered as a class of leeches, a multi-art class, a class of malletinkic, the class of Echihurides. Systems of these worms and their features are described.

The first part of the work is given general information about the type of ring worms. In the practical part of the work, information on some clays of this type of worms.

Overall characteristics of the type of ringed worms

Ring Worms are an extensive group of animals, which includes about 12 thousand species that live mainly in the seas, as well as in fresh waters and on land. This is a group of purelless invertebrates, which for this reason are of particular importance in the nutrition of other animals, as they are absorbed without a residue. At the same time, they all actively participate in the destruction of organic matter in biocenoses, promoting a biogenic cycle. Especially diverse marine forms that are found at different depths up to the limit (up to 10 - 11 kilometers) and in all latitudes of the oceans. They play a significant role in marine biocenoses and have a high density of settlements: up to 100 thousand copies by 1 meter square bottom surface. Sea rings are a favorite food of fish and occupy an important position in the trophic chains of marine ecosystems.

In the soil, earthworms are most numerous, or, as we call them, rain. Their density in forest and meadow soils can reach 600 copies per 1 meter square. Rainy worms are involved in the process of soil formation and contribute to the increase in the yield of crops and the productivity of natural biocenoses. Blood citations - leeches live mostly in fresh waters, and in tropical areas are found in the soil and on trees. They are used in medicine for the treatment of hypertension.

Consider the main features of the organization of the type of ringed worms as the first nominal animals.

1. Metalog of external and internal structure. Metamery is a repetition of the same parts or rings along the main axis of the body (from the Latin words META - repetition, MERA - part). The body is worm-shaped, divided into segments, or segments. In each segment, many system systems are repeated. The body of ringed worms consists of a head blade, segmented torso and anal blade.

2. There is a skin-muscular bag consisting of leather epithelium, ring and longitudinal muscles, which from the inside are fastened by a niculic epithelium.

3. The secondary cavity of the body (whole) is filled with a nominal fluid, which performs the role of the inner environment of the body. In general, relatively constant biochemical regime is maintained and many of the functions of the body are carried out (transport, separation, sexual, musculoskeletal).

4. The intestine consists of three functionally different departments: anterior, middle and realer. Some species have salivary glands. The front and rear departments are ectodermal, and the middle department of the digestive system - entodermal origin.

5. Most rings have a closed circulatory system. This means that blood flows only by vessels and has a network of capillaries between the arteries and veins.

6. The main allocation bodies are metanephrides of ectodermal origin. Each pair of metanephridium begins in one segment of funnels, open as a whole, from which excretory channels continue in the next segment and open there with paired holes. Methanefridia is not only the absorption organs, but also the regulation of the water balance in the body. In the channels of metanephridy, there is a thickening of the products of the selection (ammonia turns into urinary acid), and the water is absorbed back into the nominal fluid. Thereby saves moisture in the body and a certain water-salt regime is maintained in net. Moisture savings are particularly necessary for terrestrial and soil rings.

7. The nervous system consists of paired spinal cerebral ganglia and the abdominal nervous chain with meta and repetitive pair ganglines in each segment. The emergence of a brain, located at the hard side, is significantly distinguished by the collected worms from the flat. Paired spinal stakes of the brain of rings are divided into front, medium and rear ganglia. This feature of the brain structure distinguishes the rings from round worms.

8. Killed worms usually separately, but often there is simultaneous development of male and female sex glands (hermaphroditism).

9. Development often flows with metamorphosis. Typical larva at sea rings - threehood.

Thus, in the organization of ringed worms, progressive features of the organization of nominal animals are traced: the presence of an aims, the metaalog of the structure, the appearance of a circulatory system, an excretory system of type metanephridium, a higher-organized nervous system and sense organs. These rings differ from the lower worms of flat and round.

However, a number of devils in the organization of rings testifies to their relationship with lower worms. So, in the larvae of rings - three phophors there are primary body cavity, protonphridei, orthogonal nervous system and in the early stages - a blind intestine. These features are sometimes found in adult rings from primitive groups.

The type of ring worms is divided into classes:

Primary Ring Class (Archiannelida),

Multi-stage class (Polychaeta),

Unionthinkic class (OligoChaeta),

Leech class (Hirudinea),

Echiurida class (Echiurida),

Sipunculida class.

Signs and variety of rings

About 200 years ago, the great French naturalist J. Kuvier, working on the creation of the animal world system, allocated six types of animals, including the type of segic, in which he combined all creatures, the body of which is divided into segments: insects, crayfish, spiders, wets, Rain worms and leeches. Modern science has about leeches and rainworms with more extensive information, and therefore these worms are highlighted in a special type - rings.

For ringed worms, the appearance of the following features of the organization is characteristic: the presence of a secondary body or kheloma, a circulatory system, the presence of metamery - body segmentation

In addition to these features that play an important role in the evolution of animals, for the ringed worms, it is also characterized by the presence of special motion authorities - parapody, a significant development of the central nervous system consisting of a dump assembly and the abdominal nerve chain with nerve nodes; The presence of a closed circulating system, metanephridial structure of the excretory system.

1 Primary Ringlets

2 Multi-singing

3 Unobtinkovye

5 Echihurides

6 Sipunkulda

External structure of ringed worms

Ring Worms are the most highly organized representatives of the group of worms. The dimensions of the rings fluctuate from the fraction of a millimeter to two and a half meters. Mostly it is free-lived forms. The body of the rings is divided into three parts: a head, a torso, consisting of a rings, and anal blade. There are no such clear division of the body to departments that are below for their organization of animals.

The head of the rings is equipped with various senses. Many rings have a well developed eye. Some species have particularly acute vision, and their lens is capable of accommodation. True, the eyes can be arranged not only on the head, but also on the tentacles, on the body and on the tail. Ringers are developed and taste. In the head and tentacles, many of them have special olfactory cells and wilderness fosses that perceive various odors and actions of many chemical stimuli. Well developed in the rings of hearing organs arranged by type of locators. Recently, naval rings Ehirui has an hearing organs, very similar to the lateral line organs from fish. With the help of these organs, the animal subtly distinguishes the slightest rustles and sounds that are heard much better than in the air.

The inner structure of Kolchozov

Digestive system It consists of three departments: front, middle and rear. The front intestine is highly differentiated by a number of organs: mouth, throat, esophagus, goiter, stomach.

Circulatory system closed. It consists of large longitudinal vessels - spinal and abdominal connected in each of the segments of ring vessels. The blood movement is carried out due to the chipping activity of the reduced areas of the dorsal, less often ring vessels. The blood plasma contains respiratory pigments close to hemoglobin, thanks to which the rings settled habitat with the most different oxygen content. Many colley worms have red blood like a person. It is so painted, naturally, due to the presence of iron. But at the same time, iron is part of a completely different pigment, which is not similar to hemoglobin, is hemaryrin. It is capable of seizing oxygen 5 times more than hemoglobin. The choice of pigment is due to the characteristics of the lifestyle of such worms. These are bottom creatures, most of the time conductive in the thickness of the soil, where they are experiencing acute oxygen deficiency.

Respiratory system Multi-point worms - gills are thin-walled leafoids, filament or bushy, outdoor grows of pieces of spinal parapody blades penetrated by blood vessels. Unavythinkic worms breathe with the entire body surface.

Options - Parly located in each segment of metanefridium, withdrawing ultimate vital products from a strip liquid. The Methanefridium Funnel is in a number of one segment, and the short channel coming from it opens out in the subsequent segment.

Nervous system Ganglionary type. It consists of paired durable and satellite ganglia, connected by nervous trunks in the octopic nervous ring, and many of the abdominal nervous chain ganglia couples, one pair in each segment.

Sense organs. A number of rings are well developed organs of feelings, first of all eyes. Unlike the man and other warm-blooded animals, the worms have a rapid number of eyes that can be on the head, at the rear end of the body, on the sides (including on each segment) and even on the tail. Marine polychas not only react to light, but also able to emit it.

Women's livestock products. Photo: Chanabun R, Sutcharit C, Tongkerd P, Panha S

The reproduction of Kolchovetsov. The overwhelming majority of rings are separate animals, less often hermaphrodites. Sex glands are developing either under a kinded epithelium in all the torso segments (in multi-pectic worms), or only in some (at unabroad worms). Multi-singing worms of sex cells through the tears of the nuclear epithelium are entered into the fluid of the organizer, from where with special sexual funnels or metanephridia. In most water rings, fertilization external, in soil forms - internal. Development with metamorphosis (in multi-art worms) or a straightforward (at unabroad worms, leeches). Some types of rings, in addition to sex, are multiplied with an affordable method (fragmentation of the body with subsequent regeneration of missing parts). The type of ringed worms is divided into three classes - multi-styled, unauthorized and leeches.

Features of reproduction of ringed worms

Killed worms can be multiplied with both sexual and in a forceful way. The first most typical for water species, especially some marine polychites. Miscellaneous reproduction comes down either to body division into parts or to kill. When dividing the body of the worm disintegrates on halves, each of which subsequently restores the missing end.

It is curious that the tail end after the branch is an independent being and is able to repel the new head. Sometimes this head will grow long before the worm was divided in half. In the middle of the body of such a ring, who is preparing to extend the genus is the second head. After some time, two-headed creation breaks down to give life to two new worms.

Cocoon medical leech is easily feeding its many young, until they have heads.

Fertilization of sea worms that breed sexually exterior. Females and males throw out sex cells into the water, where the fusion of spermatozoa with eggs occurs. In the future, larvae are hatched from eggs - Trophorms, not similar to adult individuals. Ground and freshwater rings, including leeches, are direct development when young individuals are almost accurately copied by adults. Young leeches develop from cocoons where eggs are contained.

An important role in the reproduction of ringed worms plays glow. Glow of worms is ensured by the presence of a special substance in the body that received the name of luciferine. Under the action of a special luciferase enzyme luciferine is oxidized with oxygen to form carbon dioxide. In this case, the released chemical energy goes to the separation of light particles with excited atoms - photons. Luciferin is contained at worms in granules, which are floating in a liquid cell substance, where they are oxidized. Therefore, the impression is as if Polyhete Lights Body Fabric.

The worms are endowed with a relatively efficient oxidation mechanism, the return of which ranges from 10 to 20 percent and maybe even more. This means that over 10 percent of the chemical energy of Luciferin, marine polychas learned to be transferred to the light, and the rest is useless losses. In comparison with the incandescent lamps, the polychaete is extremely economical and compact biological devices. Thus, for every 3 molecules of luciferin, 3 oxygen molecules occur, and as a result of the reaction, 3 carbon dioxide molecules and 2 photons are released.

The biological value of the glow may be different. There are cases when invertebrates apply their illumination in order to communicate with relatives, primarily with representatives of the opposite sex. Once a year, many tropical worms leave bottom asylums and float to the surface of the ocean to swallow. Here females meet with males.

Polycetes of the Bermuda Triangle Just during the Rate apply lanterns. The females attract males intense glow, causing those on the dance, during which cavallers should encourage their ladies to the emission of sex products. If the female does not shine, then she has already performed its "dance of love." It is not interested in males. Probably, "moving candles", which observed in the waters of the Caribbean X. Columbus, were such fierce worms.

The type of ringed worms has about 9 thousand species. The organization of animals included in this type is significantly higher than that of flat and round worms. The time of the occurrence of ringed worms is unknown. Their ancestors were perhaps primitive flat worms.

Basic signs such as ring worms:

• in the external structure, the head blade with the senses, segmented torso and the rear blade, is distinguished;
• the skin-muscular bag is well developed;
• overall, or secondary body cavity; The digestive system, as a rule, consists of the oral cavity, pharynx, middle intestine and rear and ends with anal hole;
• most species have a closed-type circulatory system;
• the nervous system consists of a paired brain, a pair of occasional nerve trunks, an abdominal nervous chain. Most representatives of the type in each segment are paired nervous ganglia. Sensivities are represented by eyes, felt pits, tentacious appendages, equilibrium authorities - stamotous;
• primitive forms of separation, many have a hermaphroditism.

Type is divided into two subtypes: rigging and worm. In the subtype of the piyasy sole class are multi-minded rings (polychateches), in which two subclass are isolated - stray and seats. The bottom-up subtype includes the class of unauthorized (oligochetus) and the leech class.

Multi-singing - Mostly sea ringed worms, leading bottom lifestyle (Nareis, Aphrodite, Peskadodil). They have well developed organs of feelings in the form of papies, eyes. At each segment of animals there are primitive legs - parapody that serve to move. Their body is covered with a single-layer epithelium separating a thin cuticle. Worms separatogs, have indirect development. The larva is called throhforuShe has cilia for movement.

Unobtinka - Inhabitants of soil and reservoirs. Their parapody is reduced, and the senses are poorly developed. There is no eye in animals, so the light is perceived by photosensitive cells. They breathe the surface of the body.

Rain Worms - Hermaphrodites. The development of the worm passes without a larval stage.

Features of the structure of the rings.

Skin-muscular bag It consists of outer ring and internal longitudinal muscles, which provides a variety of worm movements. Overall - the secondary body cavity formed inside the mesoderm is divided into areas whose number corresponds to the number of body segments. It performs reference, distribution, excretory and sexual function. The reference function is explained by the incompressibility of the delicate fluid. When cutting muscles, the body becomes elastic. In general, nutrients come from the intestines, then they are distributed in the body. In general, the genital products ripen. The digestive system consists of ordinary sections for ringwaves. At the unabroad, the middle intestine forms a fold. Some of the predatory species of multi-art chutin teeth are formed in the throat.

Respiratory system - Zhabra, separate parapody sites, the entire body surface.

Circulatory system Closed. It consists of abdominal and spine longitudinal vessels communicating with ring vessels that perform the role of the heart. Reducing the spine and front annular vessels provide blood flow through the body of the worm. On the spinal vessel, the blood flows forward, and on the abdominal - back.

Selective system Formed by metanephridia - excretory channels, each of which passes through two segments of the body and comes out. The end of the channel, which opens in general, is surrounded by cilia.

Nervous system knot, ganglion type.

In the process of evolution from the collide worms, arthropods arose.

The value of ringed worms.

Multi-piece serves food fish, crab and other animals.

Rain worms have a positive effect on the soil fertility, breaking it. This facilitates the penetration into the soil of water and air. Cherves are mixed and fertilized with vegetable residues, contributing to the formation of humus. They are also included in the diet of fish and other inhabitants of freshwater reservoirs.

The leeches are used in medicine for the treatment of diseases such as vessel thrombosis, hypertension, etc.