Well, let's continue to very briefly characterize the types of worms. So today roundworms .

I ask even very impressionable to stay on this page.

……………………. Type Roundworms

…………………. Class Nematodes (Actually roundworms)

…………………………………. More than 10 thousand species

Structure: double-symmetric, from a few micrometers to a few meters, the body is unsegmented with a dense cuticle. The body is filiform, round in cross sectionand.

Body cavity: first appears   primarybody cavity - pseudo-target  (does not have epithelial lining). Located between the skin and muscular bag and internal organs. In her  all fit internal organs, filled with liquidperforms supporting, transport and protective  functions.

Digestive system: front, middle and back gut ending anus. The anterior gut is differentiated: the mouth with cuticular lips, pharynx, esophagus. The middle and posterior intestine are not divided into sections.

Circulatory and respiratory systems  are missing.

Excretory system: 1-2 skin glands - modified protonephridia  - these are large cells from which two channels depart on the sides of the body, opening in frontbodies excretory at times.

Nervous system: ladder type . She is represented   head  nerve nodes (ganglia) pharyngeal nerve  ring and several nerve trunks  (most developed dorsal and ventral), connected by cross bars.

Sense organs: poorly developed and represented by organs touch and organs chemical  the senses. Sea forms have photosensitive receptors.

Reproductive system: most roundworms dioecious, sexual dimorphism is expressed (males are smaller than females). Gonads have the appearance of tubes . Males  reproductive system unpaired  (testicle, seed tube, ejaculating channel opening into the back intestine ). In females  reproductive system   steam room  (ovaries, oviducts, uterus and unpaired vagina).

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As we see   roundworms are not so far gone in their development from their flat counterparts. Circulatory and respiratory systems, they have not yet acquired

The nature of the roundworms rewarded, the appearance of their primary body cavity (pseudo-target) and the perfect digestive system.

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Type Ringed Worms

General characteristics of the type Ringed worms (kolchetsy)

General characteristics of the type

Ringed worms (kolchetsy) - a large type (about 9 thousand species) of the highest free-living marine, freshwater and soil animals that have more complex organization than flat and round worms. This primarily include to  marine polychaete worms, which are a nodal group in the evolution of higher invertebrates: mollusks and arthropods originated from their ancient ancestors.

The main progressive features of the structure of kolchets are the following:

1. The body consists of numerous (5-800) segments  (rings). Segmentation is expressed not only in the external, but also in the internal organization, in the frequency of many internal organs, which increases the survival of the animal with partial damage to the body.

2. Groups of similar in structure and function of segments of polychaete worms are combined into body parts  - head, trunk and anal lobes. The head section was formed by merging several front segments. In mallechnitis worms, body segmentation homogeneous.

3. Body cavity secondary,  or whole  lined by coelomic epithelium. In each segment, the whole is represented by two insulated bags filled with a coelomic fluid.

Figure 11.7.   Head end of nereida: I1-eyes; 2 - tentacles; 3 -antennae; four - parapodia with tufts of bristles.

4. The skin and muscular bag consists of a thin elastic cuticle  located under it single layer epithelium  and two muscular layers: external - ring,  and internal - highly developed longitudinal.

5. For the first time appeared specialized organs of the movement - parapodia - they are the lateral bilobate outgrowths of the body walls of the trunk segments, into which the whole enters. Both lobes (dorsal and ventral) carry more or fewer setae (Fig. 11.7). In small-chained worms, parapodia are absent; there are only bundles with few bristles.

6. In the digestive system, which has three sections, the anterior intestine is strongly differentiated into a number of organs (mouth, pharynx, esophagus, goiter, stomach).

7. First developed circulatory system closed loop  It consists of large longitudinal spinal  and abdominal vessels  connected in each segment annular vessels  (fig. 11.8). The movement of blood is carried out due to the pumping activity of the contractile parts of the spinal cord, less often the annular vessels. Plasma blood contains respiratory pigments, close to hemoglobin, thanks to which kolchetsy inhabited habitats with the most different oxygen content.

8. Respiratory Organs in Polychaete Worms -gills;  these are thin-walled leaf-shaped, pinnate or bushy external outgrowths of part of the dorsal lobes of parapodia, penetrated by blood vessels. Malachish worms breathe all over the body surface.

9. Discharge organs - arranged in pairs in each segment. metanefridia,  deducing end-products of vital activity from cavity fluid. The funnel of metanephria is in the coelom of one segment, and the short tubule extending from it opens to the outside in the next segment. (see fig. 11.8,6).

10. Nervous system ganglion type.  It consists of paired epiglottic  and subpharyngeal ganglia,  connected nerve trunks  into the pharyngeal nerve ring, and many pairs of ganglia abdominal nervous chain,  one pair in each segment (Fig. 11.8, a). The sense organs are diverse: of sight (in polychaete worms), touch, chemical sense, balance.

11. The vast most  kolchetsov- dioecious animals,  less often hermaphrodite.  The gonads develop either under the coelomic epithelium in all body segments (in polychaete worms), or only in some (in miniataline worms). In polychaete worms, the germ cells through the ruptures of the coelomic epithelium enter the coelom fluid, from which they are introduced into the water by special sex funnels or metanephridia. In most aquatic armor fertilization is external, in soil forms it is internal. Development with metamorphosis (for polychaete worms) or direct (for miniataline worms, leeches). Some types of kolchets, except for sexual, multiply and asexually (fragmentation of the body, followed by regeneration of the missing parts). Type Ringed worms are divided into three classes - Polychaeta, Mala chetiz and Leeches.

Type Ringed Worms. general characteristics

The main characteristic signs of annelids are:

-secondary,or coelomic, cavitybodies;

Appearance circulatoryand respiratory systems;

Excretory system in the form of metanephridia.

a brief description of

Low-class nephritis

Class Malachishwormsunites 4-5 thousand species. The length of their body ranges from 0.5 mm to 3 m.

Audiofragment "Class Malshchetinkovye worms"(00:54)

The internal structure of the earthworm

The integuments of the body and muscles.  The skin of the worm consists of a single layer of integumentary cells. Among them are cells that produce mucus. Under the skin are the annular and longitudinal muscles. When the annular muscles contract, the body of the earthworm lengthens, thinns, and moves forward. With the contraction of the longitudinal muscles, the back part pulls up to the front. Movement occurs in waves.

Virtual Lab

Body cavity As we already know, the earthworm belongs to three-layer animals. His body consists essentially of two tubes nested inside one another. The outer tube is the wall of the body, and the inner is the wall digestive tract. Body cavity lined on the inside with a layer of cells is located between them. In the cavity fluid (it gives the body elasticity) are internal organs.

Digestive system.  The digestive tract begins with the mouth, followed by the pharynx, esophagus, goiter, stomach, intestines and anus.

Circulatory system.  The circulatory system is designed to move oxygen, carbon dioxide, nutrients and other substances inside the body. In an earthworm, blood does not pour freely into the body cavity, but moves only inside the vessels. This circulatory system is called closed . The circulatory system consists of two main vessels : spinal and ventral. In the spinal blood flows forward, in the abdominal - back. In the esophagus, these vessels are connected by annular vessels, called "hearts". They have muscular walls, with the help of which they inject blood   in the abdominal vessel. To all organs and to the walls of the body, small blood vessels flow away.

Respiratory system.

Respiratory system.  The respiratory organs of the earthworm are absent. Breathing is carried out through moist skin penetrated by blood vessels.

Excretory system.  The excretory system is represented by paired organs (excretory tubes) located in each segment of the body. With the help of the excretory system, the body removes excess water and other substances.

Nervous system.  The nervous system consists of the pharyngeal nerve ring and the ventral nerve chain with swelling in each segment from which the nerves depart. Peripharyal pharyngeal ring consists of epipharyngeal and subpharyngeal ganglia connected by an annular bridge. There are no special sensory organs, but the sensory cells in the skin allow the earthworm to sense touch and distinguish light from darkness. The excitation that occurs in these cells is transmitted along the nerve fibers to the nearest nerve node, and from there along the other nerve fibers to the muscles, which causes their contraction. Thus, the nervous system responds to irritation (reflex).

2. Reproduction and development

The earthworm is able to reproduce both asexually and sexually. With asexual reproduction, the body of the earthworm breaks down into two parts, and then, by regeneration, each of them “completes” the missing parts of the body.

3. The value of earthworms

Ringed worms serve as important links in the food chains of natural biogeocenoses. Earthworms, for example, feed on moles, hedgehogs, frogs, toads, and birds. Other worms (e.g. pipe builder) - fish (carp, crucian carp).

Earthworms bring great benefits to humans by loosening the soil. They make it more porous, more accessible to the penetration of air and water, which facilitates plant growth and increases crop yield. Rummaging in the ground, the worms swallow pieces of soil, chop them up and throw them away with organic matter.

Charles Darwin became interested in earthworms as a young man. In 1837, he made a report on the formation of the soil layer in the London Geological Society, in which he stated the theory that soil particles are constantly carried away by earthworms from the depths to the surface, due to which objects lying on the ground turn out to be few years have passed at a depth of 6–10 cm under turf. Thus, the entire soil layer is passed through the stomach of earthworms.

Charles Darwin was struck by the following observations: the worms were pulling leaves into the hole, grabbing them by the top (not by the petiole), so the leaf had the least resistance when pulling into the hole (because the top of the leaf was already its base). But pine needles worms always pull over the scape, that is, the common ground for twin needles. And in this case, the object has the least resistance. Darwin, in his experiments, laid triangles cut out of paper into worms, and they pulled them in the most expedient way: at one of the sharp corners. Further studies have shown that reflexes play a leading role in this process.

Earthworms are capable of learning. They were placed in a T-shaped labyrinth: in the longest corridor that forms the base of the letter T. When the worms crawled to its end, they were given the choice to turn right or left. On the right, they were waited by blackout and food, on the left - by a weak discharge of electric current. After a series of such “lessons”, the worms produced a reflex to unmistakably go in the right direction, to food.

Type Ringed Worms. Class Malashchetinkovye

GENERAL CHARACTERISTICS

Structure and integuments . The body of the small-necked worms (oligochat) strongly extended, cylindrical, consists of lying one after another rings, or segments. All segments have a similar structure, i.e. for the organization of oligochaetes (and all ringed worms) is characteristic structure repeatability, or metamerism. Each segment, except the very first, is supplied small bristles, usually arranged in four bunches - a pair of side and a pair of abdominal. Anterior segment is head lobe - simple, devoid of eyes and antennas. He carries mouth opening. The last segment is anal lobe, or pygidiumbears powder powder.

Veil oligochaeta presented epitheliumforming a thin surface elastic cuticle (Fig. 1). Epithelium is rich glandular cells.

Skin Muscular Bag . Under the epithelium are well developed. muscle layers. Outer layerpresented circular muscle fibers. By reducing this layer, the worm's body becomes thinner and stretched. Inner layer, more powerful, presented longitudinal muscle fibers, by reducing which the worm's body thickens and shortens.

Fig. one.A cross-section of the middle part of the earthworm's body: 1 - cuticle; 2 - epidermis; 3 - a layer of ring muscles; 4 - a layer of longitudinal muscles; 5 - coelomic epithelium; 6 - metanephridium; 7 - seta; 8 - mesentery; 9 - abdominal vessel; 10 - subneural vessel; 11 - abdominal nerve chain; 12 - chloroogenic cells; 13 - intestinal cavity; 14 - vascular plexus; 15 - Tiflozol; 16 - Tiflozol vessel; 17 - spinal vessel

Between the intestine and the skin-muscle bag is secondary body cavity , or whole -space bounded by its own epithelial walls of mesodermal origin and containing coelomic fluid (Fig. 2). By structure, the whole is different from the primary body cavity by the presence coelomic lining - own wall. The pavement is formed two sheets. One is adjacent to the wall of the body, the other - to the walls of the intestine. Above the intestine and below it, both leaves grow together, forming mesentery(mesentery) which divides the whole on the left and right side. In addition, there are transverse partitionsthat divide the body cavity by cameras, matching boundaries of rings. The whole is filled with fluid in which phagocytes, eggs, and sperm cells float. Coelomic fluid, washing the internal organs, supplies them with oxygen and nutrients, and also contributes to the removal of metabolic products and the movement of phagocytes. As well as the fluid that fills the primary body cavity in roundworms, the coelomic fluid can play a role hydroskeleton.

Digestive system oligochaeta well differentiated (Fig. 3). She starts mouth opening. The intestine consists from three departments - front, average and rear. The most differentiated anterior section of the intestine, consisting of the pharynx, esophagus and muscular stomach. Sometimes there is a goiter in front of the stomach. In the midgut to increase the absorption surface formed vagirovany inside the intestinal lumen - tiflozol.

Fig. 2Development of coelom in annelids. А-В - transverse sections of three successive stages of the segment development: 1 - intestine; 2 - the primary body cavity; 3 - whole; 4 - outer wall of the coelomic bag; 5 - spinal mesentery; 6 - the inner wall of the coelomic bag; 7 - abdominal mesentery; 8 - abdominal nerve trunks

Circulatory system closed and consists of two main longitudinal vessels - spinal and abdominal. The dorsal vessel passes along the whole body above the intestine, the ventral one below it. The cavity of the blood vessels is a remnant of the primary body cavity. Both vessels are communicated by annular vessels located metamerically. The movement of blood through the vessels is ensured by the pulsation of the dorsal vessel and certain annular vessels of the anterior part of the body, which are therefore called lateral, or annular, hearts. In the spinal vessel, blood flows forward, in the abdominal - back. The blood moves through the annular vessels from the dorsal vessel to the ventral one in the anterior part of the body and in the opposite direction in the posterior segments. The blood may have a red color from iron containing vertebrate close to hemoglobin dissolved in blood fluid.

Fig. 3The structure of the earthworm (opened worm): 1 - throat; 2 - esophagus; 3 - calcareous glands; 4 - goiter; 5 - the stomach; 6 - midgut; 7 - the dorsal fold of the intestine (in section); 8 - epipharyngeal ganglion; 9 - node of the abdominal nervous chain; 10 - spinal blood vessel; 11 - circular vessels covering the pharynx; 12 - abdominal nerve chain; 13 - metanefridia; 14 - testes; 15 - seed tube; 16 - seed bags; 17 - ovaries; 18 - oviducts; 19 - seminal receptacles; 20 - partitions of the body cavity

Excretory system is presented metanefridia. Metanephridium begins in the body cavity funnel - nephrostomy. From the funnel there is a duct that passes through the partition, enters the adjacent segment and opens to the outside. excretory at times in the side wall of the body. In each segment there is a pair of metanephridia - right and left. The funnel and duct are provided with cilia, causing movement of the excreted fluid.

Nervous system. central part the nervous system consists of paired cerebral ganglia — suprapharyngeal and subpharyngeal, united by two semi-pharyngeal connections (nerve trunks connecting opposite ganglia). Thus formed pharyngeal ring. In the central part of the nervous system enters and paired abdominal nerve trunk. In each segment trunks have a thickening - ganglia,which are interconnected by jumpers - commissures (transverse nerve trunks connecting the ganglia of one segment). Formed abdominal nerve cord, like a ladder. Each ganglion innervates all organs of the segment in which it is located.

Sense organs u oligochat very poorly developed due to the burrowing lifestyle. Eyes almost always are missing. However, there are photosensitive cells, in large numbers scattered in the skin, allowing oligochaetes to be sensitive to light.

The reproductive system. Oligochaeta - hermaphrodites but fertilization have them - cross internal. The genital gonads are localized in the genital segments. Male gonads - testes - lie in the seed capsules, which are in the seed bags. Female reproductive system is presented a pair of ovaries, a pair of oviducts and egg bags.

Reproduction and development. Direct development without the larva stage. Eggs develop inside the egg cocoon, which forms in the belt zone.

In addition to sexual reproduction in oligochaetes observed asexual reproduction similar to asexual reproduction of ciliary worms. The body of the worm is divided into two halves: the back of the body at the front regenerates, the back of the body - the head part.

Helminthology and nematodology are the sciences that study worms and the processes of their vital activity: from laying eggs and the emergence of larvae to the formation of adult individuals. The digestive system of nematodes is complex and diverse. And today we will dwell on this question: is there a body cavity in roundworms, and what?

Types of worms and the structure of their body cavity

Studying the worms, you need to pay attention to other types, so it was with what to compare the class round and know at least approximately their structure. In the process of clarifying the question of whether there is a body cavity in roundworms, consider briefly the family of crawlers:

1. Flatworms have three cellular layers: external (ectoderm), internal (endoderm) and middle (mesoderm). They generally do not have a body cavity as such, but are filled with a parenchyma, due to which food is supplied, digested and exited. The digestive system is absent, or it is complex without the intestine.
2. Ringed worms have a whole (secondary body cavity), in the epithelial layer of which there are partitions separating the segments. These walls divide the cavity and protect the body from external factors. Digestive system end-to-end with the initial, intermediate and anal intestine.
3. Roundworms have schizocel (primary body cavity). The digestive system is pass-through, without partitions, with intestines and anal exit. Most of the worms reproduce by an internal algorithm, and individuals are fertilized in parthenogenesis in an independent way.

All inhabitants have one common accessory - the skin-muscular bag, which brings them together and belongs to the same genus. Determining whether there is a body cavity in roundworms, the types and structure of its structure, we turn to a detailed study of the considered individuals and their digestive scheme.

Description of the body cavity of roundworms

Acquainted with the flat, ring and oval members of the animal world, find out more thoroughly about the insides of the last representatives. Primary body cavity roundworm  also called a pseudo-target. It does not have its own epithelial layer, and it looks like a through hole between the muscle mass and the common intestine. In this space are all the major organs and systems. Here the center of the vital activity of the organism and the whole existence of the nematode. The body cavity of the roundworm performs such necessary functions as:

• support and direction of the form;
• formation of muscular system;
• the development of a hard layer - cuticle;
• transfer of fluid under pressure;
• food accompaniment;
• development of metabolic processes.

We gave a superficial characteristic and confirmed the answer to whether there is a body cavity in roundworms. Yes, there is a primary lithophysis, and let's talk more about this further.

About roundworms in general

Nemathelmints, or nematodes - this is the name of roundworms. Their body is oblong and corpulent, thin and sharp at the ends. Among them stand out:

• gastrointestinal;
• rovers;
• hairworms;
• scrapers;
• nematodes.

• human ascaris;
• trichinella;
• whipworm;
• children's pinworm;
• hookworm.

Going deep into the study, we ask the sources: is there a body cavity in roundworms? Yes, the primary body cavity - we already understand that so. But what is its role not only in the development of a boneless creature, but also in getting this pest into the human body?

Gastrotrichs

Now we know where roundworms have a primary inner stronghold. The cavity of the roundworms of gastrotrichs is slightly expressed, and half of its area is occupied by the cells of the parenchyma. The gut of the digestive tract passes through three levels:

• front - massive sip;
• middle - ferrous;
• back - anal passage.

Turbellarians (protonephridia and areas of the ciliary epithelium, hermaphroditism and parenchymal areas in the body cavity), as well as features present in nemathelmints (three intestinal nodes and the primary body cavity) are characteristic of the structure of the gastrointestinal worms. The allocation system consists of two protonphridia. Fertilized internally gastrotricha. Separate individuals breed in the form of parthenogenesis.

Rotifers (Rotatoria)

The body cavity in roundworms is highly structured. In the digestive system of this species are present:

• mouth and throat;
• mastaks - stomach chewing design;
• medium intestine;
• rear short intestine;
• anal pass.

The stomach contains the cuticular anvil - the jaw with two hammers. In the midgut are two glands for digestion. In the allocation system, there are two protonephridia, whose channels are connected with bladder  and an anal orifice. Rotifers lay their seeds through the oviduct, tied to the caudal intestine, called the cloaca. For the full development of life the main types of rotatoria necessarily mixing parthenogenetic and sexual generations. Rotifers have great vitality, are able to form cysts to wait out adverse conditions and resettlement.

Volosatiki (Nematomorpha)

If you ask yourself if there is a body cavity in roundworms of hair makers, you can say with certainty: yes. Although she is a little different and her colleagues. In general structure, they are similar in the hypodermis and smooth muscles. But here the intestine is almost or completely reformed. Adult nematomorpha worms practically do not feed. Excretory system is also not. Only the nervous system contains the pharyngeal ring and the nerve-abdominal trunk that joined it. But females of this species breed very intensively, laying more than a million eggs into the water through the back gut.

Scrubs (Acanthocephala)

The digestive system is not. The pair of protonephridia also belongs to the organs of excretion. The nervous system has two trunks from the sides and ganglion of the head. The genital sphere consists of two oviducts and the uterus, vagina and ducts. Giant scratches macrocanthorhynchus hirudinaceus grow preferably in the intestines of piglets, where they get along with the soil and where they reach their maturity. Some individuals are drawn in length by 25 centimeters.

Nematodes (Nematoda)

Getting acquainted with the most extensive class - nematodes, we have almost come to the knowledge of whether there is a body cavity in roundworms? Yes of course. And nematoda is no exception to the rule. They have a pronounced internal system in which there is no mesodermal lining, and it is filled with fluid. It also develops a digestive branch:

• oral cavity and pharynx;
• esophagus;
• middle gut;
• back gut;
• anal pass.

In the excretory secretion is the hypodermis, consisting of one or two cells, also called neck glands. In the anterior part of the body pass the excretory channels and four phagocytic cells. The organs of touch (papillae) and chemical perception (amphidae) are poorly developed. In the female genital pattern there are two oviducts, the same number of ovaries and one pair of queens.

In conclusion about roundworms and not only

1. Flukes - Fasciola hepatic (Fasciola hepatica), (Opisthorchis felineus), lanceolate flukes (Dicrocoelium lanceatum).
2. Tapeworms - chains (Cyclophyllidea), pseudophyllidea (Pseudophyllidea).

And there is no difference, there is a body cavity or not in predators, you need to take all measures to combat them and strictly follow the instructions so as not to get infected with the larvae. Their entry into the human body occurs through water and raw or poorly processed meat of livestock. And if the bad has already happened, then you should not hesitate: it is important to undergo a course of intensive therapy against the invader. Today, this is done by specialized methods quickly and painlessly.