Type Flatworms. Class Ciliary worms. Flatworms: structural features, types and general characteristics

§ 1 Habitats and external structure of Flatworms

Type Flatworms has about 15 thousand species of animals. Flatworms are found in all habitats: aquatic, soil, terrestrial-air and organismic. Their body sizes vary from half a millimeter to 15 meters. However, despite such a variety of species, all representatives of this type have a number of common features.

All representatives of Flatworms are multicellular animals and have bilateral body symmetry. Let's remember what symmetry is. Symmetry in biology is the regular arrangement of identical parts of the body relative to the center, which is called the axis of symmetry. Bilateral symmetry means that one side of the animal's body is a mirror image of the other side.

An important feature external structure representatives of this type of animal is also a flattened top and bottom body shape. Outside, the body of Flatworms is covered with only one layer of epithelium, under which there are 3 layers of muscles. The totality of the skin and muscles of the worms is commonly called the skin-muscular sac.

§ 2 Internal structure of Flatworms

Speaking about the internal structure of this type of animal, it must be remembered that the circulatory and respiratory system missing. They are characterized by aerobic or anaerobic respiration. Oxygen enters the body through the entire surface of the body.

The digestive system of Flatworms is represented by a mouth, pharynx and highly branched intestines. However, the posterior intestine and anus are absent, so undigested food remains are excreted through the mouth.

The work of the excretory system is aimed at removing excess water and some metabolic products from the body. In flatworms, it is represented by a whole network of branched tubules that are located along the entire body, uniting into 1 or 2 excretory canals, they open at the posterior end of the body.

A pair of supraesophageal ganglions and longitudinal nerve trunks, connected by strands, form the nervous system. Of the sense organs, Flatworms have light-sensitive eyes, special balance organs, and tactile cells.

Most species of Flatworms are hermaphrodites. Hermaphrodites are called animals, in the body of which there are simultaneously organs of both the male and female reproductive systems. Despite this, 2 individuals are involved in the process of fertilization.

§ 3 Systematics of Flatworms

Type Flatworms are divided into 3 main Classes, namely Class Ciliary Worms, Class Flukes and Class Tapeworms.

The class Ciliary worms includes about 3.5 thousand species of animals. Most Ciliary worms are free-living, ie. they live in any habitat, with the exception of the organism. Their skin is covered with cilia, which gave the name to this class. Due to muscle contraction, the cilia move, thereby moving the body in space. The most famous representatives of the Class Ciliary worms are: Dairy Planaria, Black Planaria and Many-eyed.

List of used literature:

1. Konstantinov V.M. Lesson planning for the textbook “Biology. Animals ”for grade 7, Konstantinov V.M., Babenko V.G., Kumchenko V.S. / Konstantinov V.M. - M.: Ventana-Graf, 2005. - 304 p.
2. World Encyclopedia: Biology / Ch. ed. M.V. Adamczyk: Ch. scientific Ed. V.V. Adamchik: Mn .: Modern writer, 2004. - 832 p.
3. Iontseva A.Yu. Biology in schemes and tables / A.Yu. Iontseva, A.V. Torgalov. - M.: Eksmo, 2014. - 352 p.
4. Sadovnichenko Yu.A. Biology / Yu.A. Sadovnichenko. – M.: Eksmo, 2013. – 512p.
5. Biology: a guide for applicants to universities: In 2 vols. V.1. - 2nd ed., Rev. and additional - M .: RIA "New Wave": Publisher Umerenkov, 2012. - 512p.

Used images:

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.

Patients who want to get rid of worms often ask for natural remedies with the least side effects. In such cases, I recommend this tool.

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.

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 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 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 the internal organs is 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. 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 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, due 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 blood 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, musculocutaneous sac, tegument, hypodermis, reduction, protonephridia (flame cells), orthogon, strobili, 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

flatworms

Free-living species we can meet in the seas, either fresh waters. In total, 5500 species of flatworms are known.

The phylum flatworms are usually represented by three classes:

• flukes,
• eyelash worms,
• Tape worms.

Body structure of flatworms

When looking at the body flatworm, you can determine its right and left sides, abdominal and dorsal, i.e. it is bilaterally symmetrical.

With the help of the abdominal part, the worm can move on a hard surface. Thanks to nerve cells and organs responsible for perception chemical substances, as well as the organs of vision located at the head end of the body, flatworms have the opportunity to better navigate in space.

The intestinal system of a flatworm is very simple, it consists of the anterior, caecum and middle intestine.

However, flatworms become the first owners of excretory organs, the function of which is to remove excess water, metabolic products, and also regulate osmotic pressure.

Flatworms are hermaphrodites. The reproductive system of flatworms is represented by the sex glands, ducts and yolks.

Class Ciliary worms

The most typical representative of this class is the predator dairy planaria, which is a free-living flatworm. The habitat of planaria is stagnant fresh water.

Planarians feed on insect larvae, snails, and small crustaceans. Planarians have a well-developed ability to regenerate.

Flukes class

A representative of this class of flatworms is a liver fluke, whose habitat is the ducts of the liver of cattle and humans.

The development cycle occurs with a change of host and alternation of generations.

Together with the feces, the mature egg enters the water, after a short development a larva appears, it penetrates into the body of the intermediate host (small pond snail), where it turns into a sporocyst, and then a redia.

Such a long period of development is evidence that the ancestors of flukes were free-living.

Tapeworms

The body of a tapeworm consists of a head, neck and segments, which are alternately interconnected.

A typical representative of the bull tapeworm, the ultimate owner of which is a man.

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The purpose of the lesson is to analyze the basic features of this type of animal and the first two of its three classes.

In the previous lesson, we analyzed the type of Ki-shech-but-lost-nye. They have ra-di-al-ny sim-met-ryu. And this year we are on-chi-on-it once-a-thief about two-sided-sim-metric animals.

Two-sided-sim-metric - a huge group, more than 99% of animals belong to them. Including these are flatworms, ringworms and roundworms, mollyus-ki, members-no-one-hundred-no-gie, choir-to-vye and many others. etc. Their body is characterized by two-sided symmetry and the presence of three cellular layers: ek-to-der-we, me-zo- der-we and en-to-der-we. Here, I remind you that the intestinal-but-on-lost cell-layers had only two. In most bilaterally symmetrical animals, one can distinguish between the anterior and posterior ends of the body, as well as the abdominal and spinal ny side of the body. Some-rye, one-on-one, again morning-chi-va-yut two-sided symmetry, as, for example, needle-skin.

The most ancient in terms of origin, with-mi-tiv-noy group-sing two-sided-symmetric-metric animals are considered flatworms. This type combines worm-like demons-of-the-night calls that do not have a body. Flatworms live in saline and fresh waters; some species have adapted to life in wet earthly places-to-obi-ta-ni-yah, many pa-ra-zi-ti-ru -yut on different groups of animals.

The body length of flatworms lies in the range from 0.5 mm to 20 m. The body consists of several cellular layers. The outer integumentary layer of free-but-living flatworms has cilia. Pa-ra-zi-ti-che-sky pre-hundred-vi-te-lei has no res-no-cheque.

Why do pre-hundred-vi-the-types, like right-vi-lo, have a flat body? The fact is that they have no special breathing system. In order for each cell to be able to receive sour and give off carbon-le-sour gas (i.e., for gas-to-ob-me-on) , it must-on-ra-la-gat-sya not far from the external environment. The body of large flatworms is usually flat, like boom-ma-ha.

Under the integumentary tissue, there are several layers of mu-sku-la-tu-ry. Mu-sku-la-tu-ra and the blood layer together form a skin-but-muscle-shoulder sac. Flatworms don’t have internal-ren-it in the lo-sti, the whole body is half-not-but cells-ka-mi. Or-ga-ny ob-one-not-us in the system-ste-we. In flatworms, you have a pi-sche-va-ri-tel-naya, you-de-li-tel-naya, nervous and in a lo-vaya si-ste-we or- g-nov.

The blood-ve-nos-naya si-ste-ma they don’t have, and the pi-ta-tel-nye things are dis-pro-country-ny-ut-sya right in the ki- shech-ni-ku (when he is). The gut blindly closes and communicates with the environment only through the mouth. Free-bod-but-living-woo-ing flatworms pi-ta-yut-sya pre-im-s-stvenno-but like predators. Pa-ra-zi-ti-che-pi-ta-yut-sya either with the help of the mouth, or vpi-you-vaya pi-ta-tel-studies through the entire top -ness of the body.

The nervous system is represented by the nerve-knots-la-mi, dis-lo-women-us-mi in the anterior part of the body, the brain-go- you-mi gang-gli-i-mi and from-go-da-schi-mi from them nerve-us-mi-stol-ba-mi, connect-nen-us-mi re-re-mych-ka- mi. In some free-bod-but-living-woo-shy flat worms, once you have pri-mi-tiv-nye organs of vision and or-ga-na equal -but-ve-siya.

You-de-le-nie implement-la-et-xia with the help of special channels, as well as through the surface of the body. In the or-ha-bottom-me of the flatworm, they have both male (se-men-no-ki) and female (egg-no-ki) or-ga-ny times -many. Such animals are na-zy-va-yut-xia ger-ma-fro-di-ta-mi. In-te-res-naya feature of the most-shin-stva of flatworms - is it so-called-zy-va-e-my-th-complex-th egg. It consists of a fertilized egg-cell and several bilious cells. All these cells together are covered by a single protective shield speed.

For pa-ra-zi-ti-che-sky flatworms, ha-rak-te-ren is a complex life cycle. Or-ga-nism, in some-rum time-vi-va-yut-sya and on-ho-dyat-sya for some time, li-chin-ki, na-zy-va-et-sya pro-me-zhu-precise ho-zya-i-nom. Or-ga-nism, in some-rum lives and multiplies an adult worm, na-zy-va-et-sya-windows nom.

At the present time, there are about 25 thousand species to the type of flatworms. You-de-la-ut up to 9 classes, out of some 6 representations-le-us-key-chi-tel-but pa-ra-zi-ti-che-ski-mi-vi -yes. We consider only three classes of flatworms.

Class Res-nich-nye worms

This class counts over 3500 species, predominantly free-but-living-woo. Sizes of pre-hundred-vi-te-lei - from micro-ro-co-pi-che to 30-40 cm. Most of the species are found in the seas and press -ny waters, a few - in wet places on the top of the land or in the soil.

The pre-hundreds of this class have eyelashes on the top of the body. Res-nich-ki-m-ga-yut float or re-re-move along the bottom. Large worms re-re-move-ga-yut-sya mainly due to waves-but-different movements of the body.

In the layers of ciliary worms, there are a lot of one-but-clear glands. Some-rye-le-zy you-ra-ba-you-va-yut special-ci-al-gra-nu-ly, some-rye when you break -whether-va-yut-sya on-ru-zhu and when co-cos-but-ve-nii with water form protective mucus. Thanks to this, the ciliary worms practically don’t eat other animals.

Pi-sche-va-ri-tel-naya si-ste-ma to-free-but once-but-about-time-on in pre-de-lah class-sa. The pain-shin-stvo of the pre-hundred-vi-te-lei of the class is a predator-ni-ki. Ob-on-ru-alive the victim, the worm on-roof-va-et with his body, after which you-va-et. At the same time, there are species, pi-ta-yu-schi-e-sya in-do-ros-la-mi or leading a pa-ra-zi-ti-che-sky way of life.

Or-ga-ny senses in ciliary worms, once you are significantly better than in other classes. Some species have an equal organ. The most important role is played by the organs of obscenity, since with the help of the sense of smell, almost all of them hunt. Almost all ciliated worms have eyes.

Res-nich-nye worms - ger-ma-fro-di-you. Most of the pro-is-ho-dit has a re-re-cross-blank-to-your-re-nie. The development is direct, that is, from the egg you-go-dit or-ga-nism, similar to an adult animal. Ciliary worms can also multiply in a demonic way. At the same time, on the body, it appears-yav-la-et-sya in-pe-river-naya pe-re-heavy-ka, in a degree-pen-but once-de-la-yu-shaya belly-here-noe on two parts. Brightly you-ra-same-on the ability to re-ge-not-ra-tion.

The most-bo-lea-of-the-west-na-mi are-la-yut-xia before-a-hundred-vi-te-whether from-a-row-yes plan-on-riy. These are small flatworms, some of which are in a hundred-yan-but meet in fresh-water-water-to-e-max, where they are half-for- yut among water races. In the north and middle in the lo-se of Russia, very often you meet a mo-loch-no-white plan-na-riya, the largest among others (up to 3 cm long). Through it, so-ver-shen-but white in-cro-you clearly see-sve-chi-va-et-dark-y-y-y-y-ki-shech-nick. On the head, you can see a pair of eyes.

Plan-on-rii re-re-dvi-ga-ut-sya through-you-tea-but smoothly and equally-but-by-measure-but due to res-no-check. Pi-ta-yut-sya in the basis of new chalk-ki-mi waters-us-mi live-here-us-mi. Ki-shech-nick has a through-you-tea-but branched-line form, something especially ben-but ho-ro-sho can be observed at milk-no- white plan-on-rii, if you look at it through a magnifying glass.

Once-a-many-m-yut-sya plan-on-rii eggs-tsa-mi, someone-rye-key-che-us in a cocoon. Behind the shield with the means of the plan-on-rii, their mucus is, for some reason, abundantly, but covers the body. These worms have through-you-tea-but raz-vi-tuyu re-ge-not-ra-tion.

So-sal-shchi-ki class

Worms of this class lead a pa-ra-zi-ti-che-sky way of life. Like many other couples, they have a complex life cycle. It includes, as a rule, at least three co-le-tions and pro-te-ka-et in several ho-zya-e-wahs. Usually, one of the hosts is a bru-ho-no-gy mole-lusk, and the other is like a nocturnal one. So-sal-shchi-ki pro-from-the-dyat a large number of eggs.

Window-cha-tel-ny ho-zya-in - in the sound of the night. In the or-ga-niz-me ho-zya-and-on adult worms can-go-die-sya in the ki-shech-ni-ke, pe-che-ne, gall bladder-zy-re , or-ga-nah you-de-li-tel-noy si-ste-we and in many other places. Their sizes are from ten microns to several san-ti-meters. The body is leaf-shaped, flattened. As a rule, they have two attachments - ro-to-vai and abdominal. At the bottom of the ro-to-howl of the pri-suc-ki races-on-lo-the-same-but ro-to-th-hole. Ki-shech-nick for-mknu-ty.

In-cro-you co-sal-shchi-kov do not have res-no-check. Nervous si-ste-ma - ha-rak-ter-naya for the type. You-de-le-nie - through the cross-you of the body and you-de-li-tel-nye ka-na-ly.

The pain-shin-stvo of so-sal-schi-kov is ger-ma-fro-di-you, but there are also di-del-but-po-lye. Ob-ra-zu-yu-shchi-e-sya after the worm-wei-scraping of the eggs, you-into the external environment with the feces or urine of the host.

From the egg you-go-dit li-chin-ka, able to swim with the help of b-e-niya res-no-check. For further development, it must-on-ra-zit bru-ho-no-ho-go-mol-lus-ka. Inside it, there is a li-chin-ka pre-ter-pe-va-et me-ta-mor-fo-zy and times-many-m-e-xia. Then from the body of the pro-me-zhu-exact-no-ho-zya-and-on you-ho-dyat races-se-li-tel-li-chin-ki, some-rye for-ra- zha-yut windows-cha-tel-nyh ho-zya-ev.

In total, opi-sa-but about 7200 species of sal-shchi-kov. Some species - pa-ra-zi-you che-lo-ve-ka, you-zy-va-yu-schy dangerous for-bo-le-va-nia.

Ras-look-rim as an example of a pe-che-night-twist, someone-para-ra-zi-ti-ru-et in pe-che- nor the bile ducts warm-blooded. She-za-va-et for-bo-le-va-nie fas-tsio-lez with pe-che-night-us-mi-li-ka-mi and ho-le-qi-sti-tom. Ras-pro-country-not-on among the sheep. An adult is ger-ma-fro-dit, usually up to 3 cm in length. nym ho-zya-i-nom - fresh water snail. For-ra-the-windows-cha-tel-no-go-ho-zya-and-on pro-is-ho-dit when pro-gla-you-va-nii with water or food in-ko-i- the current stage of pa-ra-zi-ta.

abstract source - http://interneturok.ru/ru/school/biology/7-klass/zhivotnye-ploskie-chervi/ploskie-chervi?seconds=0&chapter_id=79

video source - http://www.youtube.com/watch?v=vGLlqFriMns

video source - http://www.youtube.com/watch?v=ZqtXc9ZRtvo

video source - http://www.youtube.com/watch?v=6xy5QEwPwLw

video source - http://www.youtube.com/watch?v=lUq4T2IWBgU

video source - http://www.youtube.com/watch?v=z20mVcfg8_0

video source - http://www.youtube.com/watch?v=d_wz-R-5KUY

video source - http://www.youtube.com/watch?v=DGMS94Abgz4

video source - http://www.youtube.com/watch?v=TIz4ynRB1gE

video source - http://www.youtube.com/watch?v=IEDzPe6AoQ0

presentation source - http://ppt4web.ru/biologija/ploskie-chervi3.html

http://nsportal.ru/shkola/biologiya/library/2013/01/17/tip-ploskie-chervi

http://www.animals-wild.ru/bespozvonochnye-zhivotnye/972-ploskie-chervi.html

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 are painted in various colors with grains. 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. Muscular system consists 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, which allows the transfer of products from the intestine to the 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 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 for the first time 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. Due to their constant work, there is no stagnation of fluid in the body of the worm, it enters the tubules and is subsequently excreted. 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 in 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.