What is absent in intestinal animals. Type Intestinal, or Cnidaria

Coelenterates, like sponges, first appeared on earth more than 500 million years ago. They have multicellular organisms and a variety of forms. Coelenterates include sea anemones, jellyfish and corals.

general characteristics

The body of the coelenterates has the shape of a bag with a hole, which is surrounded by tentacles. They can be turned up like a polyp or down like a jellyfish. Coelenterates and sponges have a radially symmetrical body, that is, body parts are located around a central axis.

Nutrition

The internal cavity in the body of the coelenterates communicates with the surface through a single hole, which serves to eat and release undigested residues. Around the hole are tentacles that capture, paralyze and pull the prey inside.

Habitat

Coelenterates live in warm tropical seas; some of them lead a fixed way of life, others are free-floating. So, hydroids can be both motionless (polyps) and floating (jellyfish); the scyphoid class consists only of jellyfish, and the class of coral polyps includes only immobile forms - polyps living separately or in colonies. Coelenterates are multicellular organisms, characterized by a simple structure and radial symmetry. Such a structure is very convenient for animals that do not have the ability to move freely: both food and enemies can appear from anywhere, so it is important to be ready to attack or defend from any direction.

The body of all coelenterates consists of one internal cavity that communicates with the surface through a hole - the mouth, the walls of which perform respiratory functions, serve to eat and remove processed products.

The mouth is surrounded by tentacles with nettle, or stinging, cells. When a small animal touches one of them, a tubular fiber containing a poisonous liquid is thrown out. Hundreds of such threads dig into the victim, and the tentacles pull it, paralyzed, into the oral cavity. Thus, coelenterates are predators; their prey is small fish and crustaceans. Due to the specifics of the body structure, the coelenterates are well camouflaged at the bottom and become a sudden trap for their victims.

The type of structure of the intestinal cavity (there are two main types - polyps and jellyfish) during the development of the animal is able to change: the larva can be motionless, in the form of a polyp, and the adult can be mobile, like a jellyfish; and vice versa, the larva is mobile, and the adult animal is a stationary form of a polyp, like in corals.

The walls of the body of the intestinal cavity consist of two rows of cells: one is external, it is called the ectoderm, and the other internal is the endoderm. Between the two rows of cells is a jelly-like layer with plenty of water.

The ectoderm is made up of oblong muscle cells, and the endoderm is rounded. The shooting movement characteristic of jellyfish is provided by the activity of these two rows of cells, which stretch and contract. Such movements allow the jellyfish to move forward: compressions push water out from under the umbrella, and the jellyfish receives a jet propulsion, like a rocket.

The rest of the cells have been transformed into nerve cells and envelop the surface of the body in a mesh, endowing the jellyfish with sensory organs.

Coelenterates are divided into three large classes: hydroid, scyphoid and coral polyps.

There are 2700 species of hydroids; they are small, reproduce only by budding, and come in two forms, polyps and jellyfish. They live in isolation, like hydras, or in colonies, like hydrants.

The scyphoid class includes jellyfish of bright colors with large umbrellas; they only live in isolation. There are about 250 species of scyphoid: the largest representative of this class is the arctic cyanide, whose umbrella is more than 2 m in diameter.

Coral polyps are a class of intestinal cavities with the largest number of species - 6500 species. They are found only in the form of polyps, can be solitary, like anemones or sea anemones, but more often live in colonies, like corals and madrepores.

The most popular of the coral polyps - red coral - has been known in China and Japan since ancient times; in Europe, it began to be widely used for making jewelry even before our era. For the inhabitants of Tibet in the 13th century BC, red coral was a bargaining chip. In addition, as early as the end of the 19th century, various healing properties were attributed to corals: coral powder was considered a panacea for many diseases.

Kinds

The noble, or red, coral is found mainly in the Mediterranean Sea at a depth of 20 to 200 m in colonies 10-14 cm high. Other representatives of this species living in the Sea of ​​Japan reach 1 m in height and weigh about 40 kg.

For thousands of years, noble coral has been used to make small decorative items and ornaments. It is found even in burials of the 4th century BC.

The visible part of the coral is the outer skeleton, very hard and fragile, formed by small polyps. They form branched colonies that resemble small trees, especially when they move their tentacles that look like corollas of flowers.

Hydra lives in fresh water. Because of its six thin tentacles, the length of which is six times the size of the hydra itself, it is very similar to algae. Looking at it, it is hard to imagine that this innocent animal was identified in Greek mythology with a monstrous snake with nine heads that grew again every time they were chopped off.

The structure of the jellyfish is interesting in that this animal is 95% composed of water, and organic matter is only 5% of the total mass. If a large jellyfish is thrown onto land, it will completely “melt”, and in a few hours there will be nothing left on the sand but a small wet spot.

Xenia is a very beautiful tree-like coral, sparkling with its feathered tentacles.

In the sea pen, unlike its coral relatives, the outer skeleton is soft and flexible, which makes it look like a graceful quill pen. It emits a bright blue-green color, which is why it received the Latin name pennatula phosphorea, which means “phosphorus” in Russian.

The verrucoso anemone is a medium-sized anemone (about 3 cm) with a characteristic knobby leg. In case of danger, she hides her tentacles in her mouth and becomes like a hard ball.

Gorgonaria unicella cavolinia is a very rare coral found in the Mediterranean Sea. He lives in large colonies, and his branched "crown" reaches 70 cm in length. Unfortunately, the beauty of this coral draws the attention of poachers to it.

In the Mediterranean Sea, you can find caryophylla clava - a madrepore living in isolation with a thin transparent body.

To type of coelenterates include lower multicellular organisms, the body of which consists of two layers of cells and has radial symmetry. Coelenterates are characterized by the presence of stinging cells.

Hydra

About 9,000 species are known. The most typical representative is the structure freshwater hydra.

In a freshwater hydra polyp, a body up to 1 cm long looks like a sac, the walls of which consist of two layers of cells: the outer ectoderm and internal - endoderm. Inside the body there is intestinal cavity. At one end of the body is mouth surrounded by tentacles. With them, the hydra captures food and directs it into the mouth.

The other end - sole- hydra is attached to underwater objects, leads a constantly motionless lifestyle. Sometimes it can move by bending the body in one direction or another and moving the sole to another object, to which it is attached. The bulk of the ectoderm is made up of skin-muscle cells, at the base of which there are contractile muscle fibers. When they contract, the body of the hydra shrinks into a lump, one-sided contraction leads to a bend in the body. At the base of the skin-muscle cells lie star-shaped nerve cells with long processes (a very primitive nervous system).

On the body of the hydra, especially on the tentacles, are located stinging cells having a capsule stinging thread. Protrudes from the stinging cell stinging hair, upon contact with which a stinging thread is pierced into the body of the prey, its poison kills the animal, which the hydra then swallows with its tentacles.

The main function of the endoderm is the digestion of food. Some of its cells secrete digestive juice, under the influence of which partial digestion of food occurs in the intestinal cavity. Undigested food remains are expelled through the mouth. Endodermal cells also perform an excretory function. Hydra breathes the entire surface.

Hydra is characterized by both asexual and sexual reproduction.

Asexual reproduction is called budding. It happens under favorable conditions. Protrusions form on the walls of the hydra's body - kidneys, at the ends of which tentacles appear, and between them - a horn. Small hydras separate and live on their own.

During sexual reproduction, tubercles are formed on the body of hydras, in which small mobile cells are formed in some individuals - spermatozoa, on others - large - eggs.

Ripe spermatozoa swim up to the hydra with the egg cell and penetrate inside - the nuclei of the germ cells merge. going on fertilization. The ovum turns into egg covered with a thick shell. The hydra dies, and the egg falls to the bottom of the reservoir and is stored there. In the spring, a small hydra develops from it.

The hydra has a highly developed ability to restore lost and damaged parts of the body - regeneration.

Polyps and jellyfish

Among representatives of the intestinal type living in the seas, there are sessile forms - polyps and free-floating jellyfish. Among polyps there are single and colonial forms. Solitary marine polyps include anemone. With the help of a muscular leg, she can slowly move along the bottom. One of the adaptations for movement over long distances in sea anemones is symbiosis- its cohabitation with a hermit crab: a hermit crab is less noticeable at the bottom if there is sea anemone on its shell, while sea anemone gets the opportunity to move long distances, which increases its ability to get food.

Colonial coral polyps can be varied in shape (spherical, tree-like), have an external or internal skeleton of lime or horn-like organic substances of various colors. They are used to make jewelry.

Colonial madreporous polyps form dense settlements in shallow water - coral reefs and coral islands - atolls, which are often a dangerous obstacle to navigation.

Jellyfish- floating predators. Prey is killed with poison stinging cells. Their translucent body has the shape of a bell or an umbrella with a diameter of 0.3 to 2 m. Their digestive cavity consists of central part and departing from it channels.

The nervous system has a more complex structure than that of the hydra. In addition to the general nerve cluster around umbrella, there is an accumulation of nerve cells that form together with processes nerve ring.

The jellyfish have photosensitive eyes and balance organs. Jellyfish move in a jet way by shortening the bell, pushing water out from under it.

Some jellyfish ( cornerot, cross) are harmful to humans. Others are of commercial importance, for example ropilema, which is eaten in China and Japan.

Coelenterates belong to the group of multicellular invertebrates, they are one of the most low-organized representatives of this type. The group was named after peculiarities coelenterates, as the presence of a cavity called gastric or intestinal.

Their body has two layers of cells, between which there is a non-cellular layer called mesoglea and having a very low level of cellular development, the layers surrounding the mesoglea are called endotherms and ectotherms. The device of the body of animals according to the principle of radial axial symmetry is another of the features of these invertebrates.

All representatives of this species are inhabitants of water bodies and, moreover, for a very small number of freshwater coelenterates, live in the waters of the seas and oceans.

Although the group belongs to the representatives of the simplest, coelenterates have many different types of appearance. This diversity is due to two reasons. The first one is characteristics of the coelenterates, as colonial animals. An individual taken separately for consideration has a very small size and therefore, speaking of coelenterates mean their colonies.

The appearance of the colonies is very diverse, some look like bushes or small trees. Others on the feathers of fabulous birds, others resemble a brush in appearance. Along with such plastic forms, colonies are built on a solid foundation of lime. interesting a feature of the coelenterates colony , is a fairly regular geometric shape.

Another reason that has a strong influence on the appearance of the representatives of the group is that each individual can be in the form of either a polyp or a medusa.

Representatives of the polyp-shaped group have a cylindrical body, at one end of the cylinder there is a mouth surrounded by tentacles. As a rule, according to such a characteristic as the shape of coelenterates, determines the way of life of animals. Most often, representatives of polyps lead a fixed or sedentary lifestyle, and it is from them that colonies consist.

coral polyps

Representatives of the jellyfish form, on the contrary, are constantly on the move, moving alone. The shape of the body resembles an umbrella, with tentacles on the edges. Below is the mouth of the animal.

The manifestation of such features of intestinal, as having two types of state − jellyfish and polypoid, the ability to create extensive colonies of complex shapes and the diverse coloration that representatives of this group have divide animals into many different forms, and this despite the fact that their general body structure has a common type and is very simple.

hydroid polyps

General information about the group

To date, scientists have discovered about 9000 species animals belonging to this group. The smallest representatives are no more than 1 mm in size, but there are also real giants among them, for example, the jellyfish (Cyanea arctica), whose body size can be up to 2 meters, and the tentacles extend up to 30 meters.

Of the representatives of true multicellular animals, group of coelenterates is one of the oldest. On the path of evolution, animals were able to settle and live in a variety of places, sometimes completely different, according to their living conditions. Such characteristic of coelenterates how exceptional adaptability allows them to feel great in the ocean at various depths and in its various places from South to North.

Scyphomedusa

settle down coelenterates animals on a wide variety of soil types are unpretentious in terms of the level of salt in the water, as already mentioned. some feel comfortable in fresh water. They are a very important part of the formation of marine biocenoses and the maintenance of life of various species of marine animals and plants.

More about these multicellular invertebrates, this video will tell:

In this article, we have covered the main characteristics coelenterates. This group of ancient animals is very interesting and diverse. with many representatives coelenterates, you can get acquainted in my new articles.

General characteristics of the type Intestinal.

Coelenterates - two-layer animals with radial symmetry.

Symmetry. In the body of the coelenterates there is a main axis, at one end of which there is a mouth opening. Several axes of symmetry pass through the main axis, along which the appendages and internal organs of the animal are located. This type of symmetry is called radial .

life forms. The main life forms of coelenterates are the polyp and the jellyfish.

Body polyp generally cylindrical, at one end there is a mouth opening surrounded by a different number of tentacles, and at the other - a sole. Polyps are usually sedentary or inactive. Polyps mostly form colonies.

Body jellyfish has the form of a regular umbrella or bell, on the lower, concave side of which there is a mouth opening. There are tentacles or lobes along the edge of the umbrella and sometimes around the mouth. Jellyfish lead, as a rule, a mobile lifestyle and do not form colonies.

Different types of coelenterates either exist in the form of only one of these life forms (jellyfish or polyp), or go through both stages throughout their life cycle.

Systematics. In the type of coelenterates, three classes are distinguished:

hydroid (hydra, obeli, polypodium, siphonophores);

Scyphoid (Aurelia jellyfish, cornerots, cyanides, sea wasps);

coral (black and red corals, acropores, fungi, sea anemones, alcyoniums).

In total, there are 9000 modern types of coelenterates.

Body dimensions coelenterates vary widely. Some types of polyps in adulthood do not exceed a few millimeters, while some sea anemones can reach 1 meter in diameter. In jellyfish, the diameter of the umbrella can be from 2 mm to 2 meters. In addition, the tentacles of some jellyfish can stretch up to 30 m.

Motion. polyps sedentary. They can bend the body, contract, move their tentacles. Hydras can "walk" like ground surveyor caterpillars (larvae of moths). Anemones can crawl slowly on their soles.

Jellyfish actively move by contracting the umbrella. An important role is also played by sea currents that carry jellyfish over long distances.

Body structure. As already mentioned, coelenterates are two-layer animals. Their body wall consists of two cell layers - ectoderm (outdoor) and endoderm (internal). Between them is mesoglea - a layer of structureless gelatinous substance. the only cavity in the body of the coelenterates - intestinal, or gastral .

ectoderm represented by a single-layer flat, cubic or cylindrical epithelium . In addition to ordinary epithelial cells, the ectoderm includes epithelial-muscular cells whose base is elongated longitudinal direction contractile (muscle) fiber. In some corals, muscle fibers separate from the epithelium and lie under it or sink into the mesoglea layer, forming an independent muscular system. Between the epithelial cells are interstitial cells that give rise to various cellular elements of the ectoderm. A characteristic feature of the coelenterates is the presence in the ectoderm of the so-called tentacles. stinging cells . Each such cell contains a capsule into which a spirally folded long hollow process is inserted - a stinging thread. Outside the cell there is a sensitive hair, upon irritation of which the stinging thread sharply turns out, straightens and pierces the body of the prey or the enemy. At the same time, a poisonous secret is poured out of the capsule, causing paralysis of small animals, as well as a burning sensation in large ones.

Endoderm. The epithelium lining the gastric cavity consists of flagellated cells. Some of these cells are epithelial-muscular , however, the muscular processes are located in the transverse direction, forming together, layers of annular fibers. The cells of the ectodermal epithelium are able to form pseudopodia, with the help of which they capture food particles. There are also glandular cells.

Mesoglea. In polyps, the mesoglea is poorly developed (with the exception of corals), while in jellyfish this layer reaches a considerable thickness. The mesoglea contains a number of ectodermal cells that take part in the formation of the skeleton.

Skeletal formations. Only polyps have a skeleton. In hydroid polyps, the body is covered with a thin chitinous theca - a dense shell that performs a protective function. Most coral species have a calcareous skeleton, sometimes horny. The development of the skeleton can vary from individual spicules scattered in the mesoglea to powerful stone-like formations of various sizes and shapes (in madrepore corals). These skeletons are derived from the ectoderm.

The formation of the skeleton in corals is largely due to the presence of polyps in the body. symbiotic algae . Consider the chemical reactions that take place during the formation of a calcareous skeleton. The initial substances - calcium ions and carbon dioxide - are contained in sea water in sufficient quantities.

Carbon dioxide, when dissolved in water, forms a very unstable carbonic acid:

H 2 O + CO 2 ↔ H 2 CO 3, which immediately dissociates into ions:

H 2 CO 3 ↔ H + + HCO 3 -.

When Ca and HCO 3 ions interact, calcium bicarbonate is formed:

Ca ++ + 2 HCO 3 - ↔ Ca (HCO 3) 2. This substance is soluble in water, but it is also not stable and easily turns into insoluble calcium carbonate:

Ca (HCO 3) 2 ↔ Ca CO 3 ↓ + H 2 O + CO 2.

With an excess of CO 2, this reaction shifts to the left and a soluble bicarbonate is formed. With a decrease in the concentration of CO 2, the reaction shifts to the right and lime precipitates.

Algae living in the body of polyps constantly remove carbon dioxide from the tissues of the intestinal cavities for the process of photosynthesis, constantly creating a reduced concentration of CO 2. Such conditions favor the formation of insoluble calcium carbonate and the construction of a powerful skeleton by polyps.

Digestive system and nutrition. The digestive system is represented by the gastric cavity. Most coelenterates are predators. Prey, killed or stunned by stinging cells, they bring with tentacles to the mouth opening and swallow.

In hydroid polyps, the gastric cavity looks like a simple bag, which communicates with the environment through the oral opening. Various small animals that enter the gastric cavity are most often absorbed by endoderm cells ( intracellular digestion). Larger prey can be digested by enzymes secreted by glandular cells. Undigested residues are ejected through the mouth opening.

In coral polyps, the gastric cavity is divided longitudinally by septa, which increases the area of ​​the endoderm. In addition, the ectodermal pharynx protrudes into the digestive cavity of corals.

As already mentioned, reef-building corals enter into a symbiotic relationship with a certain type of unicellular algae that settle in the endodermal layer. These plants, receiving carbon dioxide and metabolic products from the polyp, supply it with oxygen and a number of organic substances. Algae themselves are not digested by polyps. Under normal conditions, such a symbiosis makes it possible for polyps to do without the intake of organic substances from the environment for a long time.

At jellyfish the gastric cavity is generally formed by the stomach located in the central part of the umbrella, radial canals extending from the stomach and an annular canal running along the edge of the umbrella. Hydromedusas often have 4 radial canals, while scyphomedusas have 16 radial canals. The entire complex of canals forms the so-called gastrovascular system .

Nervous system. At polyps nervous system diffuse type . Separate nerve cells located at the base of the epithelium of the ectoderm and endoderm are connected by their processes into a nervous network. The mouth opening and the sole of the polyps are surrounded by a denser nervous network.

At jellyfish the nervous system is more concentrated than in polyps, which is associated with a mobile lifestyle.

At hydroid jellyfish accumulation of nerve cells is located on the edge of the umbrella. The cells themselves and their processes form a double nerve ring. The outer ring performs sensory functions, while the inner ring performs motor functions.

At scyphoid jellyfish the nerve ring is less pronounced, but at the base of the ropalia (marginal sensory bodies) there are clusters of nerve cells that can be called ganglia.

sense organs. Due to a sedentary lifestyle, polyps special no sense organs . There are only a few sensitive (tactile) cells, which are located mostly near the mouth opening.

At jellyfish there are also sensitive cells, but there are also special sense organs - vision, balance and smell.

Along the edge of the umbrella are located organs of vision - eyes , different in structure. In hydroid jellyfish, the eyes lie singly, while in scyphoid jellyfish, the eyes are on ropalia - sensitive marginal bodies. Moreover, one ropaliy can carry several eyes of varying degrees of complexity at once.

In connection with a mobile lifestyle, jellyfish have appeared organs of balance - statocysts. They are a bubble lined from the inside with sensitive cells. Inside the bubble is a calcareous body - statolith. Depending on the position of the jellyfish in space, the statolith irritates a certain section of the bubble wall. There are other types of structure of statocysts. In addition, statocysts are able to capture the vibrations of water, so they can also be called organs of hearing. In hydroid jellyfish, the balance organs are located along the edge of the umbrella in the amount of 4-80 in different species.

Scyphoid jellyfish also have olfactory pits - organs of chemical sense.

In scyphoids, all the senses are located on 8 ropalia - modified tentacles.

Breath. Gas exchange in coelenterates occurs by diffusion of oxygen and carbon dioxide. Large species (corals) have siphonoglyphs lined with ciliated epithelium on the pharynx. Cells equipped with cilia constantly carry out the flow of fresh water into the intestinal cavity of the animal. Many polyps, as already mentioned, have switched to symbiosis with algae, supplying the coelenterates with oxygen and releasing carbon dioxide.

Sex organs. At polyps there are no special sex organs. Sex cells are laid either in the ectoderm or in the endoderm. In the first case, the gametes exit through the rupture of the ectoderm, in the second, they first enter the gastric cavity, and then out through the mouth. Among the polyps there are hermaphrodites (hydras) and dioecious (corals).

At jellyfish , which are almost always separate sexes, there are sex glands.

At hydromedus they form in the ectoderm of the lower side of the umbrella under the radial canals, less often on the oral proboscis. The number of gonads corresponds to the number of radial canals. Gametes exit through ruptured glands.

At scyphoid jellyfish gonads of endodermal origin. They form in the pockets of the stomach. Gametes first enter the gastric cavity, and then into the environment.

Reproduction. Coelenterates reproduce both asexually and sexually.

asexual reproduction most often proceeds through budding . This path is characteristic of polyps, and is rare in jellyfish. In single polyps, a kidney appears on the body, which gradually forms tentacles and a mouth opening and then breaks away from the mother's body. In colonial hydroids and corals, the daughter individual does not separate from the mother, which leads to the formation of colonies.

Colonial hydroid polyps they are not capable of sexual reproduction, so they bud off and sexual individuals - jellyfish. Jellyfish are formed either on the axis of the colony, or on special outgrowths - blastostyles.

Another method of asexual reproduction is strobilation when the polyp at a certain stage begins to lace up in the transverse direction several times and a small jellyfish is formed from each part. Almost the entire body of the polyp is spent on the formation of jellyfish. This method is typical for scyphoid jellyfish.

Thus, there is a change of polypoid asexual and medusoid sexual generations. At the same time, the polypoid generation predominates in hydroids, and the medusoid generation in scyphoids. Corals do not have a medusoid generation.

In a number of hydroids, jellyfish do not break away from the colony, and in some, the jellyfish is reduced to the state of a "genital sac" - a sporosarca.

Very interesting siphonophores , which are a huge colony consisting of organisms of various structures. Each colony has a pneumatophore, an air bladder that supports the siphonophore on the surface of the water.

sexual reproduction characteristic of all jellyfish, all corals and some hydroid polyps. The sexual process involves haploid cells - gametes that copulate either in the environment or in the body of the intestinal cavity. The egg undergoes complete uniform crushing. Gastrulation of the blastula most often occurs by immigration, less often by invagination. In the future, a two-layer larva is formed - a planula, covered with cilia and leading a mobile lifestyle. For such sedentary animals as corals (which do not have a medusoid generation), the planula is the only settling stage. A polyp is always formed from the planula, later budding from itself either only polyps (corals), or polyps and jellyfish (hydroid), or only jellyfish (scyphoid). Thus, the development of the vast majority of coelenterates goes with metamorphosis. Sometimes a polyp is immediately formed from an egg (for example, in hydra).

Regeneration. Coelenterates have a high ability to regenerate. Experiments on the study of this phenomenon in hydra were staged as early as 1740 by Tremblay. It turned out that the animal can regenerate from 1/200 of a part.

Origin. Most likely, the ancestors of the coelenterates were free-floating organisms of the type parenchymella , which was described by I.I. Mechnikov. These hypothetical organisms were devoid of a skeleton and therefore could not be preserved as a fossil.

The oldest finds of coelenterates - coral skeletons - date back to the Cambrian period (about 600 million years ago). At the same time, not only individual prints were preserved, but also entire petrified reefs. A few imprints of jellyfish and hydroids are also known. In total, more than 20,000 species of fossil coelenterates are known.

Meaning. In nature, coelenterates, being predators and at the same time food for other animals, participate in complex food chains of marine biocenoses. Corals are of great geochemical importance, forming thick layers of calcareous rocks. Throughout their existence, corals have been involved in the formation of islands. Reefs are unique biocenoses, where a huge number of animal species live.

Practical significance modern coelenterates is small.

Corals (especially red and black) are used as decorations. They are mined in large quantities, mainly by artisanal methods. Coral collection is prohibited on large reefs.

Some jellyfish pose a serious danger to humans. In our seas, these include a small Far Eastern cross jellyfish that lives in thickets of marine plants and a large Black Sea cornerot, often found off the coast. The poison of the cross is sometimes fatal. The most dangerous jellyfish - the sea wasp - lives off the coast of Australia. Touching this animal causes severe pain and shock. Many people died when they met her.

In China and some other countries, specially prepared ropil jellyfish are eaten. There is a special trade there.

The report on coelenterates presented in this article will help you prepare for your biology class and learn a lot of useful information about them.

Message about coelenterates

The type of intestinal cavities includes multicellular animals with a two-layer body structure and radial symmetry. Due to the lack of real organs and tissues, they are considered rather primitive animals. All of them lead an aquatic way of life, most of the species live in the oceans and seas, only some of them live in fresh waters. Intestinal animals have 2 life forms: jellyfish and polyp.

Polyps lead a sedentary or motionless lifestyle. They are anchored to the substrate. Their body has a cylindrical shape, the lower part expands to the shape of the sole. It is thanks to her that the polyps are held on the substrate. In the upper part of the body is a mouth opening surrounded by tentacles.

Jellyfish are free-swimming organisms that move quite actively in the water. Their body is dome-shaped. The mouth is surrounded by oral lobes and is located at the bottom. Numerous tentacles are located along the edges of the dome.

General characteristics of intestinal

The body of the coelenterates has a wall, which consists of two layers of cells - ectoderm (performs motor and protective functions), endoderm (performs a digestive function).

A layer of mesogley, a non-cellular substance, formed between the layers of cells. It looks like a thin plate. But here in jellyfish, the layer is much thicker and is made up of a gelatinous substance. A feature of intestinal animals is the presence of stinging cells in the ectoderm.

All individuals have a gastric digestive cavity: in polyps it is saccular, and in jellyfish in the form of a system of canals. All undigested food remains are removed through the mouth. They have intracellular digestion.

Absolutely all representatives of intestinal cavities are predators. Their nervous system of a diffuse type and responses acquired a reflex character. They breathe with the entire surface of the body. They are also characterized by regeneration, which is associated with the division of intermediate cells.

The process of reproduction is carried out asexually and sexually. There are hermaphrodites.

Interesting facts about coelenterates

• In China and Japan, jellyfish are eaten. They eat only umbrellas, removing tentacles and the oral cavity. They are fried, boiled and called "crystal meat".
• They have organs of balance and vision.
• These are the only animals in their group that have a thread with poison in their body. When they are in danger, they throw it out and paralyze the enemy.
• From the intestinal corals make jewelry and extract a special building material. But when corals are burned, lime is obtained.
• Man, observing the jellyfish and their movement, created jet engines.

We hope that the report on coelenterates helped you to prepare for the classes. And you can leave your message about intestinal animals through the comment form below.