Message about coelenterates. General characteristics of coelenterates, lifestyle, structure, role in nature Interesting types of coelenterates

The only intestinal animals in their group have stinging capsules, thanks to which, if necessary, as a rule, during irritation, they throw the thread out of the body, it contains poison. He must paralyze any attacked animal, but this applies mainly to small individuals.

Coelenterates have tentacles that are considered important parts of their body. The tentacles serve as hands, with the help of which the animal grabs the prey and pushes it into its mouth, where the prey is partially digested, digested into small fragments, then the food passes to the ectothermal cells, which already absorb useful substances. Undigested particles are excreted again through the oral cavity.

The hollow threads of the coelenterates, with which animals defend themselves and neutralize other animals, look like tentacles. At their tips are stinging cells, outwardly they look like harpoons that dig into the body of the victim and release poison.

In some coelenterates, the venom of the stinging cells is able to act even on humans. It is believed that the poison of intestinal animals is not harmful to humans, but this is a big mistake. Some species of these animals cause serious burns in humans. There are cases when the nervous or respiratory system failed and people died a painful death.

In intestinal animals, there are two categories that lead a mobile lifestyle and not mobile. In general, people should avoid any encounters with these animals so as not to put their health at risk. For example, anemones are more like flowers, these animals have many tentacles that are looking for prey.

Wow! .. Here, yes! .. Be healthy! ..

Type Intestinal - these are multicellular individuals, inhabitants of water expanses, mainly seas. Some species have adapted to a sedentary lifestyle (attach to the bottom or substrate), while others actively move, covering long distances.

There are over 10,000 species of coelenterates. The variety of coelenterates is very large: there are small individuals up to a couple of millimeters, and huge representatives are jellyfish cyanoea, about two meters wide, and the tentacles reach 15 meters in length.

Why are intestinal animals given this name? Coelenterates have a two-layer body, so that a cavity is formed between the cells of the layers, which is equipped with one mouth opening. The cavity is called intestinal, and the name intestinal cavity was formed.

For coelenterates, radial symmetry is characteristic, if you draw a line from the lower edge to the upper, then the opposite parts of the body relative to the drawn axis will be identical. The wall of the polyp consists of three layers.

Epidermis

The first layer is the outer ball of epithelial cells (epidermis).

The ectoderm also includes:

• contractile cells(provide movement);
• stinging that perform a protective function. In the capsule of stinging cells there is a paralyzing poison; when danger approaches, poisonous substances enter a special channel, which is located in the stinging thread and goes to the body of the victim. After splashing out the poison, the cell dies, a new one begins to form from the intermediate cells;
• intermediate cells capable of constant division and transformation into specialized ones, this is how the regeneration of the body is carried out;
• sex cells- eggs and spermatozoa are formed in ectodermal tubercles.

Endoderm

The second layer is the inner (endodermis). The cell ball lines the intestinal cavity, consists of two types of cells:

• Digestive- have flagella and pseudopods, with the help of which they capture food particles and carry out intracellular digestion;
• glandular- secrete enzymes for the breakdown of food in the gastric cavity.

Mesoglea

Mesoglea, which is located between the layers and is a jelly-like mass, with collagen fibers, does not contain cells.

Coelenterates lack mesoderm - the middle germ layer.

Coelenterates

All representatives are deprived of specialized respiratory, circulatory, excretory organs. Nervous system coelenterates is represented by nerve cells that are connected to the nerve plexus. Jellyfish have nerve rings near the mouth and dome.

Digestion carried out in the intestinal cavity due to glandular cells, epithelial-muscular cells are responsible for intracellular digestion. Digested residues are excreted through the mouth opening (the digestive system is closed).

reproduction coelenterates goes by budding, this is an asexual mechanism, when the body is divided in longitudinal or transverse directions. During sexual division, sperm and eggs enter the external environment, where they merge. First, a zygote is formed, and then a larva emerges - a planula. After the transformation of the planula, either a polyp or a jellyfish can form from it.

Life cycle of coelenterates

Depending on the life cycle of the coelenterates, two groups are distinguished: asexual generation (polyps) and sexual generation (jellyfish).

polyps- These are single organisms or colonial ones, which unite from tens to thousands of individual individuals. Equipped with a mouth opening with tentacles, which passes into the gastric cavity. The lower part of the polyp is the sole with which it is attached to underwater objects or the bottom.

The internal cavity is divided by septa, the number of which corresponds to the number of tentacles. Cilia depart from the septa, which are in constant motion and provide a regular change of water inside the polyp.

The continuous movement of water provides increased pressure in the intestinal cavity, so the polyps straighten out and stay in this position for a long time. When he gets tired, he changes his position by bending over or moving a short distance.

The shape of the body is similar to a bell, the contractile cells of which ensure the active movement of individuals in the water. The mesoglea is 98% water, the rest is connective tissue. Jellyfish, due to their high water content, are easy to keep in the aquatic environment.

On the bottom of the bell is a mouth opening with mouth lobes. With the help of the mouth, food is captured, which enters the intestinal cavity. It consists of many tubules that have departed from the central cavity. In the mouth area there are stinging cells that serve to obtain food and protect against enemies.

Jellyfish have sensory organs, on the surface of the body there are eyes that perceive light rays. If the jellyfish is washed ashore, it will die due to the complete evaporation of water.

What stage of the life cycle of coelenterates promotes their settlement?

The dispersal of animals across the sea is at the larval and medusoid stages. During these periods of life, they are able to move or are carried by the current. A polyp, on the other hand, can only move a couple of meters over the entire period of existence, and most are completely motionless.

Types of coelenterates

The following types of coelenterates are distinguished: hydroid, scyphoid and coral polyps.

hydroid- have a relatively simple structure in comparison with other representatives of the type. They feed on plankton and small animals. In the spring-summer period, it reproduces asexually, buds develop on the body, which, when ripe, leave the mother. In autumn, sexual reproduction takes place, with the formation of an egg, which in the spring will give life to new organisms.

Scyphoid- a class of free-swimming jellyfish, the polyp stage is either absent or poorly developed. Reproduction is sexual, a scyphostomy is formed, from which jellyfish bud (the young form is ether).

coral- organisms with an internal keratinized skeleton. They lead a sedentary lifestyle, reproduce by budding, while not separated from the mother's body, or sexually.

Flatworms have a more complex structure and developed differentiation of tissues and organs. But representatives of the coelenterates have evolved significantly in comparison with the simplest organisms, which is manifested in the structure, way of life, procreation.

Compare the life features of coelenterates and protozoa using the table below.

The role of coelenterates in nature

Participate in the regulation of the number of small fish, crustaceans, as they are food for intestinal organisms.

They are an integral part of the marine biocenosis.

They form coral reefs - a mass accumulation of madreporous corals. They are located near the islands, gradually growing upwards, forming islands (atolls).

They serve as raw material for the extraction of lime.

Coelenterates can live in symbiosis with other animals. Anemones, which lead a sedentary lifestyle, often attach themselves to crayfish and thus move faster. Cohabitation is also beneficial for cancer, as anemone protects it from enemies.

The anemone's tentacles provide hiding places for small shrimp.

The value of intestinal organisms in human life

Widely used in the food industry (edible jellyfish - cornerot). The Japanese catch several thousand tons of Ropilem jellyfish every year, from which various dishes are prepared.

Jewelry is made from the skeleton of a red coral polyp.

Coral reef islands become an obstacle to transport ships.

A poison that is dangerous to human health, which is secreted by stinging cells of the coelenterates, causes severe burns, as well as respiratory failure and cardiac arrhythmia.

This species is nothing but invertebrate multicellular animals. They are divided into two types: ctenophores and cnidarians, as well as into two categories: mobile and motionless. Consider the most interesting facts about coelenterates.

About jellyfish

Jellyfish, like sea feathers and pelaria, stand out with a bluish glow. This is because certain bacteria live in their body, thanks to which these coelenterates have bioluminescence.

An Australian scientist found that in the 44th year of the last century, approximately 100 thousand people died from the poison of the box jellyfish of the sea wasp in the Australian seas. She is the most dangerous and poisonous animal in the world.

Also in southern Australia, in Edikar, they discovered the oldest jellyfish prints in the world. It was possible to find out that they are about 600 million years old.

Many people wonder why jellyfish are transparent. Because their body is almost entirely water, only 2 percent is collagen.

The definition of "jellyfish" was given to a number of marine coelenterates by the famous scientist Linnaeus back in 1740.

The huge jellyfish cyanide capillata is the largest coelenterate. It lives in the Atlantic Ocean, in its northwestern part. Its diameter is almost 2.30 meters, and the tentacles are 36.5 meters.

About corals

The Great Barrier Reef is the largest in the world. It is located in Australia, Queensland. Its length is more than 2,000 kilometers, and its width reaches 72 km.

Those reefs that are formed by stony coral polyps are the most diverse. They can only be compared with tropical forests. In them you can find many species of fish, shellfish and other aquatic life.

There are such horn corals, or gorgonians. So, they are most popular because they contain a large amount of iodine. In ancient times, they were even used for medicinal purposes.

About the structure of the intestinal

Many of them have tentacles, and these are very important organs for them. Seeing their prey, they wrap their tentacles around it and push it into their mouths.

They also have hollow filaments, an equally important organ. These threads also resemble tentacles, only with their help the coelenterates protect themselves and neutralize the enemy.

The poison of stinging cells, which is released by the coelenterates, can be deadly to humans, although many consider it harmless. A burn is still half the trouble, the worst thing is that the nervous and respiratory systems can fail, which will lead to death.

Intestinal cavities (Coelenterata or Cnidaria) are distinguished into a separate type of animal, there are about 9000 species. They are characterized by radial symmetry: they have one main longitudinal axis, around which various organs are located in a radial order. In this they sharply differ from bilaterally symmetrical (or bilateral) animals, which have only one plane of symmetry, dividing the body into two mirror-like halves - right and left.

Leuckart was the first to separate the coelenterates from the echinoderms and designated by this name a group of radiant animals. In these animals, the intestine does not form an independent cavity, but corresponds to the common cavity in other animals. This cavity in them is both digestive, and circulatory, and respiratory.

The intestinal cavity is divided into three subdivisions:

• ctenophores, or ctenophore (Ctenophorae),
• stingers (Cnidaria)
• and sponges.

Ctenophores belong to pelogical animals, as they swim freely in the open sea. They are either in the form of transparent, like glass, ovals, cones, hemispheres, or in the form of ribbons, up to 1-1.5 meters long, and flat disks. Their mouth is always turned downwards and leads to a cavity that corresponds to the stomach, where digestion takes place. Under the skin there are channels that communicate with the upper part of the gastric cavity. Above the channels, on the surface of the body, there are solid longitudinal plates called ribs. On the ribs are rows of ciliated cilia that form swimming plates. The most important organs of ctenophores are the tentacles.

Sometimes very long and branched, they serve partly as grasping organs, and partly help animals in locomotion. Very interesting organs of ctenophores are prehensile cells. They look like small warts and are equipped with a spirally twisted thread. Spontaneously ejected or retracted, they serve to catch small organisms.

All ctenophores are hermaphrodites. The main distinguishing features of the stinger are the stinging vesicles of the nematocyst. The bubbles contain a long thread and a poisonous liquid. Chasers are divided into two classes - polypo-jellyfish (Polypo-medysae) and coral polyps (Anthozoa). The most beautiful representative of the siphonophore order is undoubtedly Physalia (Physalia). The body of the physalia consists of a large bladder, which sometimes reaches the size of a child's head, and a swimming column. Physalia is considered the most dangerous of the siphonophores. In his stories, Meyen described how, in one round-the-world voyage, a sailor, fascinated by the amazing beauty of the physalia, rushed into the water to get it. As soon as he touched the physalia, it twisted its threads around his shoulder, and instantly he felt a terrible pain. The comrades who came to the rescue with difficulty pulled him aboard; after this he developed a violent fever, and for a long time his life was in danger. The Pelagic physalia (Physalia pelagica) lives in the Mediterranean Sea, but the main area of ​​the physalia is the warm seas, where they reach amazing beauty. Hydromedusae, or hydras, are called polyps of a relatively simple structure, which almost always form colonies. The walls of the body consist of two layers - outer (ectoderm) and inner (endoderma), separated by a third layer. The outer layer contains stinging cells. Around the mouth opening is a corolla of tentacles. Hydroids usually reproduce asexually.

In the same way, a generation of jellyfish with sexual reproduction is formed. The larva, which developed from a fertilized egg of a jellyfish, after some time of free swimming, attaches itself to an underwater object and begins to reproduce asexually, forming a colony.

Hydrojellyfish are real marine animals, but there are also freshwater forms among them. Much more often in fresh stagnant waters there are hydras (Hydra), 1-8 mm long. The green hydra (Hidra viridis) and the gray or common hydra (H. vulgaris) live in our waters. Akalefs or jellyfish are otherwise called umbrella jellyfish, since the shape of the body of these jellyfish resembles an umbrella.

The body of jellyfish is always transparent and very tender, gelatinous. Dimensions can reach up to 18 cm in diameter.

With the help of contractions of their umbrella, jellyfish swim quite quickly. Jellyfish usually stay on the surface, although a case is described when the Challenger deep-sea expedition caught a specimen of an amazing periphilia from a depth of 2000 meters. In the European seas, jellyfish are very plentiful. Almost all jellyfish are very beautiful, especially if they are observed in freedom. The development of jellyfish in most cases occurs with alternation of generations. Coral polyps, which include the noble coral, in most cases, the animals are very small. Working imperceptibly at the bottom of the oceans for a number of geological epochs, these animals have built entire islands, countless reefs and shoals, laid the foundation even for some continents.

Almost 200 years have passed until people became convinced of the similarity of these small mysterious animals with larger sea anemones or anemones, whose belonging to the animal kingdom was well known even to Aristotle. According to Ovid's Metamorphoses, the Romans and Greeks believed that corals represent flowers that petrify as soon as they are taken out of the water. In connection with this, there is probably a myth about the Gorgon Medusa, at the sight of which everyone turned to stone and which was killed by Perseus.

In the skeleton of the polyp, metabolism and growth occurs, due to the continuous deposition of new layers. The death of the coral skeleton occurs from below, so that the coral grows upward and rests on the already dead part. Reproduction of polyps occurs both sexually and asexually, through budding. There is hardly any other class of animals in which the change in form would reach such a degree. The history of the development of the sponge has been studied in some detail. A larva develops from an egg. During free swimming in water, the larva undergoes significant changes. The posterior cells, after growth and intensive reproduction, overgrow the anterior ciliated half. In the end, it turns into a flat circle in the form of a lid on a cup. After some time, this circle is drawn inward and a two-layer gastula sac is formed. Later, the shape of the larva changes into a cylindrical one. Probably the most beautiful and interesting in structure can be considered six-beam, or glass sponges. The skeleton of these sponges, after removing the inner pulp, becomes transparent. The basic form of such a vitreous skeleton is always the same and represents the connection of the three axes of the cube, intersecting each other at right angles. The size of glass sponges is varied: from a few millimeters to half a meter in diameter. Reproduction occurs both sexually and asexually.

The first vitreous sponges were discovered at the end of the 18th century. In the East, these sponges were even traded, as they were valued for their elegance and beauty. Intestinal cavities (Coelenterata or Cnidaria) are distinguished into a separate type of animal, including about 9000 species. They are characterized by radial symmetry: they have one main longitudinal axis, around which various organs are located in a radial order. In this they sharply differ from bilaterally symmetrical (or bilateral) animals, which have only one plane of symmetry, dividing the body into two mirror-like halves - right and left. All radially symmetrical animals lead a sedentary lifestyle or did so in the past, i.e. come from attached organisms. One of the poles of the body serves to attach the animal to the substrate, at the other end there is a mouth opening.

Intestinal - bilayer animals, in ontogenesis they form only two germ layers - ectoderm and endoderm.

Between the outer and inner layers is a non-cellular substance, sometimes it forms a thin layer (hydra), sometimes a thick gelatinous layer (jellyfish). The body of the coelenterates has the form of a bag open at one end. Digestion takes place in the cavity of the bag, and the hole serves as a mouth, through which undigested food residues are removed. However, this is a generalized scheme of the structure of the coelenterates, which, depending on the lifestyle of specific representatives, may change. Sedentary forms of coelenterates - polyps - most correspond to this description. Freely moving jellyfish are characterized by flattening of the body along the longitudinal axis. The division into jellyfish and polyps is not systematic, but purely morphological; sometimes the same type of coelenterates at different stages of the life cycle may look like either a polyp or a jellyfish. Another characteristic feature of the coelenterates is the presence of stinging cells in them.

The type is divided into three classes: hydrozoa (Hydrozoa, about 3000 species), scyphoid jellyfish (Scyphozoa, 200 species) and coral polyps (Anthozoa, 6000 species). In each of the classes there are well-known representatives. Among the hydrozoa, this is a small (up to 1 cm) hydra polyp found in our fresh water bodies. It leads a sedentary lifestyle, attaching to the substrate with its base, or sole. At the free end of the body there is a mouth opening surrounded by a corolla of 6-12 tentacles, on which the bulk of the stinging cells are located. Hydra feeds mainly on small crustaceans - daphnia and cyclops. Reproduction occurs both sexually and asexually. In the first case, a new hydra develops from a fertilized egg after a certain dormant period (winter). It should be noted that most hydroid polyps lead, unlike hydra, not a solitary, but a colonial way of life. At the same time, special mobile individuals arise and bud in such colonies - the same jellyfish that<отвечают>for the dispersal of polyps.

Jellyfish actively move and release mature germ cells into the environment. The larva that has developed from a fertilized egg also moves for some time in the water column, and then sinks to the bottom and forms a new colony. As a separate subclass in the class of hydroids, the siphonophore (Siphonophora) is distinguished, which include very interesting colonial animals from the genus Physalia (Physalia). These are marine organisms that live mainly in the southern seas. Although outwardly the physalia looks like a solitary animal, in fact, each of its<особь>It's just a colony of organisms. In it, individual individuals are attached to a single trunk, in which a common gastric cavity is formed, which communicates with the gastric cavity of each of the individuals. The upper end of the trunk is swollen, this swelling is called an air bladder or sail, and is one highly modified medusoid individual.

Along the edges of the opening leading to the cavity of the bladder, a closing muscle is formed:<надувая>bubble or releasing gas from it (it is secreted by the glandular cells of the bladder, in composition it is close to air), physalia are able to float to the surface or sink into depth.

Below the bubble are other members of the colony that specialize in feeding or reproduction, as well as stinging polyps. In physalia, there are two main types of arrangement of the mass of tentacles of the colony under the bubble: shifted to the left or shifted to the right. This allows the colonies moving on the surface of the water under the action of the wind to move in two different directions and to some extent protects them from the fact that, under some unfavorable wind direction, they will all be thrown at once onto the coastal shallows. In one of the most common physalia of the Pacific Ocean (Physalia utriculus), one of the tentacles, the so-called noose, is longer than all the others, and can reach 13 meters or more in length.

Along it are thousands of stinging batteries, each consisting of hundreds of microscopic capsules (individual cells) called nematocysts. These spherical cells contain a tightly coiled, hollow, drill-like thread that conducts the venom. When the fish stumbles upon the tentacle, the threads pierce the tissues of the victim, and the poison from the capsules is pumped through these channels. Thus, the lasso captures and paralyzes the prey, and then pulls it to the mouth. If a physalia stings a person who accidentally touches it, the consequences can be very serious. Physal burns are very painful, blisters appear on the victim's skin, lymph glands enlarge, sweating increases, and nausea appears.

Sometimes it becomes difficult for victims to breathe. A close relative of physalia has long been known - the Portuguese warship (Physalia physalis). Its approximately 35 cm long crested float is very colorful - the membrane is colored iridescent blue, turning into mauve and further, at the top of the crest, into pink. Boat colonies look like extraordinarily elegant balls, often intact<флотилиями>drifting on the surface of the ocean. From time to time, the boat dips the float into the water so that the membrane does not dry out. Deadly poisonous tentacles stretch down from the float for 10-15 m, capable of paralyzing large fish and pulling it up to the digestive organs. Although Physalia are inhabitants of the open ocean, many of them, under appropriate currents and weather conditions, are carried to the shores of Northwestern Europe. Even washed ashore, they retain the ability to sting anyone who touches them. The best way to interact with physalia for a person in the sea is to try to get away or swim away from them, remembering that the most dangerous tentacles more than 10 m long are attached to a small air bubble below. Despite the toxicity of physalia, some sea turtles eat them in huge quantities. People, of course, do not eat physalia, but they also find use for them. Farmers in Guadeloupe (Caribbean) and Colombia use dried tentacles of physalis as poison for rats. In scyphoid jellyfish, the body looks like a rounded umbrella with long tentacles suspended from below.

In all species, a gastrovascular system of varying complexity is formed, radial canals running from the stomach to the edges of the body. A number of tentacles in jellyfish are modified, turning into the so-called marginal bodies. Each of these bodies carries one statocyst (a formation involved in maintaining balance) and several eyes, including a very complex structure. The body of most jellyfish is transparent, which is due to the high (often up to 97.5%) water content in the tissues. Some species of scyphoid, such as, for example, the eared jellyfish known to everyone who has been to the Black Sea, or Aurelia (Aurelia aurita), are very widespread - in almost all seas. Coral polyps generally resemble hydroid coelenterates, but their structure is much more complex. They have a differentiation of muscle tissue, many have skeletal formations. Madrepore, or reef-building corals (from the group of six-ray corals, Hexacorallia) * have branches that sometimes reach 4 m in length. It is them<останки>and form coral reefs. Red noble coral of the Mediterranean Sea (Corallium rubrum) belongs to the eight-pointed corals (Octocorallia) and is not able to form reefs. Its colonies grow on the coastal slopes of the Mediterranean Sea at a depth of more than 20 m (usually from 50 to 150 m). Interesting history of the name<коралл>. It comes from the Greek word for a hook used by divers to extract coral from great depths. Approximately the same noble red coral, which has long been used to make jewelry, is mined today. With all the diversity of corals, the polyps that actually make up the colonies are arranged more or less the same way.

A single polyp placed in a calcareous cell is a tiny living lump of protoplasm with a complex internal structure. The mouth of the polyp is surrounded by one or more corollas of tentacles. The mouth passes into the pharynx, and she - into the intestinal cavity. One of the edges of the mouth and pharynx is covered with large cilia that drive water into the polyp. The internal cavity is divided by incomplete partitions (septa) into chambers. The number of partitions is equal to the number of tentacles. There are also cilia on the septa, which drive water in the opposite direction - out of the cavity. The skeleton of stony corals is quite complex. It is built by the cells of the outer layer (ectoderm) of the polyp. At first, the skeleton looks like a small cup in which the polyp itself sits. Then, as the radial partitions grow and form, the living organism turns out to be, as it were, impaled on its skeleton. Coral colonies form as a result of<не доведенного до конца>budding.

Some corals have not one, but two or three polyps in each cell. In this case, the cell is stretched, it becomes like a boat, and the mouths are arranged in one row, surrounded by a common rim of tentacles. In other species, dozens of polyps already sit in the lime house. Finally, in meander corals, all polyps merge to form a single organism. The colony takes the form of a hemisphere, covered with numerous winding grooves. Such corals are called brain corals, the furrows on them are merged mouth slits, seated with rows of tentacles. Colonies of coral polyps grow quite quickly - branched forms, under favorable conditions, grow up to 20-30 cm per year. Having reached the level of low tide, the tops of coral reefs stop growing and die, and the entire colony continues to grow from the sides.

From broken off<живых>branches can grow new colonies. Corals also have sexual reproduction, these organisms have separate sexes. From the fertilized egg, a free-swimming larva is formed, which, after a few days, settles to the bottom and gives rise to a new colony. In order for coral polyps to be able to safely grow and build reefs, they need certain conditions. In shallow, well-heated lagoons, they withstand water heating up to 35 ° C and a certain increase in salinity. However, water cooling below 20.5 °C and even short-term desalination have a detrimental effect on them. Therefore, in cold and temperate waters, as well as where large rivers flow into the sea, coral reefs do not develop.

In scyphoid jellyfish the body looks like a rounded umbrella with long tentacles suspended from below. In all species, a gastrovascular system of varying complexity is formed, radial canals running from the stomach to the edges of the body. A number of tentacles in jellyfish are modified, turning into the so-called marginal bodies. Each of these bodies carries one statocyst (a formation involved in maintaining balance) and several eyes, including a very complex structure. The body of most jellyfish is transparent, which is due to the high (often up to 97.5%) water content in the tissues. Some species of scyphoid, such as, for example, the eared jellyfish, or Aurelia (Aurelia aurita), known to everyone who has been to the Black Sea, are very widespread - in almost all seas.

Coelenterates, or radial animals - a group of multicellular invertebrates.
Coelenterates are the only animals in their group that have stinging capsules, thanks to which they can, if necessary, usually during irritation, throw out a thread that contains poison from the body. The poison should paralyze any attacked animal, but usually only small individuals.

Interesting facts about coelenterates

- coelenterates have tentacles, which are important parts of their body. With the help of tentacles, the animal grabs its prey and pushes it into its mouth, where partial digestion takes place, the prey is digested into small fragments, then they pass to the ectodermal cells, they already absorb useful substances. If some particles are not digested, then they go back through the oral cavity;

- hollow threads with which intestinal animals defend themselves and neutralize other animals look like tentacles. Stinging cells are located at the tips of the tentacles, in appearance they are similar to harpoons that dig into the body of the victim and inject poison;

- the poison of stinging cells of some intestinal animals even affects people. It is believed that the poison from various intestinal cavities is not harmful to humans, but in fact this is an erroneous opinion. Some of the animal species can cause severe burns in humans, and there have been cases when the respiratory and nervous systems failed, which led to painful death;

- intestinal animals are divided into two categories, one of them leads a mobile lifestyle, and the other is motionless. In general, people should be wary of all varieties of these animals so as not to put their health at risk. For example, sea anemones are more like flowers, in fact, they are animals with many tentacles that are only looking for prey;

- jet engines were created by observing jellyfish that move like them.

- most representatives reproduce sexually and have planktonic or crawling larvae. The life cycle of a significant part of cnidarians is metagenesis: a regular alternation of sexual and asexual reproduction.

- A person uses some coelenterates. Building material is extracted from the dead calcareous parts of corals, lime is obtained during firing. Black and red corals are used to make jewelry.

With stinging cells, some coelenterates can cause burns to divers, swimmers and fishermen. In some places, coral reefs prevent the passage of ships, while serving as a refuge and food for fish.

- Since they are intestinal predators, they affect marine animal communities, eat plankton, and large sea anemones and jellyfish also eat small fish. In turn, sea turtles and some fish feed on jellyfish. Some types of jellyfish are edible ( Rhopilema esculenta, Rhopilema verrucosa)