And coral polyps belong to type of coelenterates. They are also called stinging– for stinging cells located in the tentacles and other parts of the body. Animals use stinging cells to catch, immobilize and kill victims; the burns of some are very painful for people, and several species of coelenterates are even capable of fishing for humans. The name coelenterates reflects the threefold structure of their body - they resemble an empty bag, inner part which is occupied by the digestive cavity. Most of these creatures live in the sea and only a few species have adapted to life in fresh water. There are no land coelenterates.

The digestive cavity of jellyfish and other coelenterates has a single opening - this is both the mouth and the outlet for undigested residues. It is usually surrounded by long and thin tentacles, the number of which can exceed a hundred. On the outside, their surface is strewn with stinging cells.
If we look at a jellyfish from below, we will see swaying tentacles, or oral lobes, that immobilize the prey and pull it towards the mouth.
Purple-striped jellyfish are quite difficult to spot in the murky sea waters where they drift like ghosts.

Most coelenterates have a soft, transparent, quivering body containing a large sac-like digestive cavity. The body of an animal is formed by two layers of cells and a jelly-like substance between them. Some species, such as corals, build strong cup-shaped protective shells around themselves. Jellyfish have a particularly thick layer of jelly-like substance.
BODY SHAPE. In the group of coelenterates there are two main life forms: jellyfish and polyp. Some coelenterates spend their entire lives in one form. For example, hydra and sea anemones always live in the form of polyps. But many coelenterates begin life as a polyp and then turn into jellyfish - or vice versa.

POLYP. A typical polyp has a soft, cylindrical shape. The elongated lower part of the body serves to attach the animal to stones, algae and other objects. At the top of the polyp there is a mouth surrounded by a ring of hunters stinging tentacles directed upward. Sea anemones and corals spend their entire lives in the form of polyps; they do not have the jellyfish stage.

JELLYFISH. The typical one resembles a polyp turned upside down. Her body looks like an umbrella or a bell, from behind the edge of which tentacles pointing downwards peek out. The mouth is located in the center on the underside of the body. Usually the jellyfish swims in the water column, and the polyp sits and slowly crawls at the bottom. Jellyfish spend all or most of their lives drifting in the oceans.

PALE OR BRIGHT. Some jellyfish, sea anemones and corals are pale or milky in color, especially in cold waters. At the same time, tropical species are often colored bright shades pink, red, yellow and orange color.
At low tide on exposed rocky seabed sea ​​anemones look like dull patches of jelly. But with the onset of tide, they spread their soft tentacles, similar to the corollas of flowers. For this they are called - “ sea ​​anemones" But of course sea anemones are animals. Like all coelenterates, sea anemones look harmless, but in fact they are merciless predators.

Coelenterates:
- about 10,000 species
- mostly marine inhabitants, there are a few freshwater species
- have a round body shape
- mouth surrounded by tentacles
- most are soft-bodied, but some (corals) form strong, hard protective shells or skeletons
- the stinging cells of some representatives contain poison dangerous to humans

The type is divided into three classes:
1. Hydroid
– about 3500 species
– marine and freshwater (hydra)
– in the life cycle the stages of polyp and jellyfish usually alternate; there are colonial forms.

2. Coral polyps (including sea anemones)
– about 6000 species
– only sea
– live only in the form of polyps

3. Scyphoid (jellyfish)

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

Report on coelenterates

The phylum Coelenterate organisms include multicellular animals with a two-layer body structure and radial symmetry. Due to the lack of real organs and tissues, they are considered quite primitive animals. All of them lead an aquatic lifestyle, most species live in oceans and seas, only a few of them live in fresh waters. Coelenterate animals have two life forms: jellyfish and polyp.

Polyps lead a sedentary or immobile lifestyle. They are fixed on the substrate. Their body has a cylindrical shape, the lower part expands to the shape of the sole. It is thanks to it that the polyps are held on the substrate. In the upper part of the body there 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 in the lower part. Along the edges of the dome there are numerous tentacles.

General characteristics of coelenterates

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

Between the layers of cells a layer of mesoglea, a non-cellular substance, has formed. It looks like a thin plate. But in jellyfish, the layer is much thicker and is made up of a gelatinous substance. A feature of coelenterates is the presence of stinging cells in the ectoderm.

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

Absolutely all representatives of coelenterates are predators. Their nervous system diffuse type and responses acquired a reflex character. They breathe over the entire surface of their 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 the tentacles and 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 of poison in their body. When they are threatened, they throw it out and paralyze the enemy.
• Made from coelenterate corals Jewelry and get a special construction material. But when corals are fired, lime is obtained.
• Man, observing jellyfish and their movement, created jet engines.

We hope that the report on coelenterates helped you prepare for classes. You can leave your message about coelenterates using the comment form below.

These amazing coelenterates - jellyfish and corals, as well as worms

These amazing coelenterates - jellyfish and corals, as well as worms

The most numerous predators

Due to the predominance of jellyfish remains, the end of the Proterozoic is called the “age of jellyfish.” Then, about 700 million years ago, the first animals appeared in the sea. These were primitive invertebrate creatures, worms and jellyfish. Since then, jellyfish have been one of the most numerous predators on Earth. First, the jellyfish absorbs everything it finds in its immediate vicinity. Then he stops. It rises from the depths a meter or two and heads in the opposite direction. In front of her are crustaceans, rising up after her first passage.

Pretty simple creatures

Jellyfish are fairly simple creatures compared to humans. Their body lacks blood vessels, heart, lungs and most other organs. Jellyfish have a mouth, often located on a stalk and surrounded by tentacles. The mouth leads into a branched intestine. And most of the jellyfish’s body is an umbrella. Tentacles also often grow on its edges.

Gelatinous form of being

Thanks to its original jelly-like shape, the jellyfish has buoyancy potential. A particularly rigid body in the ocean is not necessary: ​​here in aquatic environment, there is nothing for marine life to run into.

Jellyfish can contract to release a jet of water and at the same time are not provided with muscles to return to their original position. For this reason, the bodies of some jellyfish are formed around a transparent disc. Its substance, although jelly-like, contains collagen threads that give the disc sufficient elasticity. Such a disk has shape memory.

Does a jellyfish eat crabs?

Jellyfish muscles

The umbrella of a jellyfish consists of a gelatinous elastic substance. It contains a lot of water, but also strong fibers made from special proteins. The upper and lower surfaces of the umbrella are covered with cells. They form the integument of the jellyfish - its “skin”. But they are different from our skin cells. Firstly, they are located in only one layer (we have several dozen layers of cells in the outer layer of skin). Secondly, they are all alive (on the surface of our skin dead cells). Third, the integumentary cells of jellyfish usually have muscular processes; That's why they are called dermal-muscular. These processes are especially well developed in cells on the lower surface of the umbrella. Muscle processes stretch along the edges of the umbrella and form the circular muscles of the jellyfish (some jellyfish also have radial muscles, located like spokes in an umbrella). When the circular muscles contract, the umbrella contracts and water is thrown out from under it.

Brain and nerves of a jellyfish

It is often believed that the nervous system of jellyfish is a simple nervous network of individual cells. But this is also wrong. Jellyfish have complex sensory organs (eyes and balance organs) and clusters of nerve cells - nerve ganglia. You could even say that they have a brain. Only it is not like the brain of most animals, which is located in the head. Jellyfish have no head, and their brain is a nerve ring with nerve ganglia on the edge of an umbrella. Nerve cell processes extend from this ring, giving commands to the muscles. Among the cells of the nerve ring there are amazing cells - pacemakers. An electrical signal (nerve impulse) appears in them at certain intervals without any external influence. Then this signal spreads around the ring, is transmitted to the muscles, and the jellyfish contracts the umbrella. If these cells are removed or destroyed, the umbrella will stop contracting. Humans have similar cells in their heart.

Jellyfish are constantly eating

While examining schools of herring spawning off the coast of British Columbia, biologists found that in one day, crystal jellyfish ate the entire herring brood. In addition, jellyfish harm fish by devouring their food. For a number of reasons, a huge number of jellyfish mnemopsis. Soon after, the herring catch fell from 600 to 200 tons per year.

Jellyfish escape

The well-studied Aglantha digitale jellyfish has two types of swimming - normal and “flight reaction”. When swimming slowly, the muscles of the umbrella contract weakly, and with each contraction the jellyfish moves one body length (about 1 cm). During the “flight reaction” (for example, if you pinch a jellyfish’s tentacle), the muscles contract strongly and frequently, and for each contraction of the umbrella, the jellyfish moves forward 4–5 body lengths, and can cover almost half a meter in a second. It turned out that the signal to the muscles is transmitted in both cases along the same large nerve processes (giant axons), but with at different speeds! The ability of the same axons to transmit signals at different speeds has not yet been discovered in any other animal.

There will be more sprat because of jellyfish

Scientists are beginning an experiment in the Caspian Sea to introduce the Beroe jellyfish, which feeds on the ctenophore Mnemiopsis. It was he who caused the catastrophic decline in the sprat population in the Caspian Sea. Mnemiopsis was brought with ballast water from the Sea of ​​Azov. Feeding on plankton, Mnepiopsis undermined the food supply for sprat over the course of two years. As a result, it became so scarce that catches of this type of fish decreased almost tenfold. For example, this year the quota for its catch will be only 23.9 thousand tons. Although ten years ago this figure was close to 225 thousand tons, and it was sprat processing that most fish factories in the Astrakhan region were focused on.

Reasons for the increase in the number of jellyfish

In overfishing of commercial fish species - the main destroyers of jellyfish. Among the main enemies of jellyfish are tuna, sea ​​turtles, ocean sunfish and some ocean birds. Salmon also does not disdain jellyfish.

Abundance of jellyfish

There are so many jellyfish in the Chesapeake Bay in Maryland that you can't even stand a chance near the shore. Without stepping on them. The feeling is not pleasant - as if you are walking through thickets of nettles. The cause is the stinging cells of jellyfish.

In 2002 In French Cote d'Azur big jellyfish pelagia violet-red color multiplied in such quantities. That it tore fishing nets with a total weight of over 2 thousand kg to shreds.

In Japan, jellyfish clogged the mouths of pipes for taking water into the cooling system nuclear power plant. Because of which her work was stopped.

Fleeing from enemies, the jellyfish throws away its tentacles

Jellyfish ColobonemaColobonema sericeum throws off tentacles, and she has 32 of them. This is probably why the jellyfish that are found near the coast. These deep-sea jellyfish, which are found at depths of 500-1500 m, rarely have a full set of tentacles. Colobonema in its entirety can be seen only on the surface of the ocean. This is a small jellyfish, its dome diameter is 5 cm. The same thing happens to a lizard when it is grabbed by the tail. When swimming, a jellyfish moves in a reactive manner - by pushing water out of any part of the body, as a result of which the animal moves forward in the opposite direction.

Arctic giant jellyfish Cyanea

The largest jellyfish in the world is considered to be the Arctic giant jellyfish (Cyanea), which lives in the Northwest Atlantic. One of these jellyfish, washed ashore in Massachusetts Bay, had a bell diameter of 2.28 m, and its tentacles extended 36.5 m. Each such jellyfish eats about 15 thousand fish during its life

The diameter of the cyanea jellyfish bell reaches two meters, and the length of the thread-like tentacles is 20-30 meters.

Extreme jellyfish
Lake Mogilnoye on Kildin Island near the Kola Bay is a completely unique Arctic body of water. It is located in close proximity to the sea, and sea water seeps into it. Sea and fresh water do not mix due to different densities. From the surface to a depth of 5-6 m there is a layer of fresh water in which freshwater forms of organisms live, for example Cladocera Daphnia and Chidorus. Below, up to 12 m, lies a layer sea ​​water, in which jellyfish, cod, and sea crustaceans live. Even deeper is a layer of water contaminated with hydrogen sulfide, in which there are no animals.

Australian sea wasp Chironex fleckeri

The most poisonous jellyfish in the world is the Australian sea wasp (Chironex fleckeri). After touching its tentacles, a person dies in 1-3 minutes if he does not arrive in time health care. The diameter of its dome is only 12 cm, but the tentacles are 7-8 m long. The venom of the sea wasp is similar in its effect to the venom of a cobra and paralyzes the heart muscle. On the coast of Queensland in Australia, more than 70 people have become victims of this jellyfish since 1880.

One effective means of protection is women's tights, which were once used by lifeguards at a surfing competition in Queensland, Australia.

Giant jellyfish stygiomedusa gigantea

Jellyfish sting

Killer Jellyfish Carukia barnesi, which has a deadly sting, is actually tiny - the length of its dome is only 12 millimeters. However, it is this animal that is responsible for the occurrence of Irukandji syndrome, which killed two tourists in Australia in 2002. It all starts with a mosquito-like bite. For an hour, victims experience severe pain in the lower back, lumbago all over the body, cramps, nausea, vomiting, sweating and coughing profusely. The consequences are extremely serious: from paralysis to death, cerebral hemorrhage or cardiac arrest.

Jellyfish are bred in captivity

Australian scientists from the CRC Reef Research Center have for the first time managed to grow the jellyfish Carukia barnesi, which has a deadly sting, in captivity. The captured jellyfish has passed the planktonic stage and is now kept in an aquarium. Getting jellyfish to breed in captivity was the first step in developing an antivenom. In general, it will be necessary to study from 10 thousand to a million jellyfish.

Giant jellyfish of Japan Stomolophus nomurai

Since September, thousands of giant jellyfish measuring more than a meter and weighing about 100 kilograms have been observed off the coast of Echizen (Fukui Prefecture). They can reach a length of up to 5 meters, have poisonous tentacles, but are not fatal to humans. Their migration to the Sea of ​​Japan is associated with an increase in water temperature.

Fishermen complain that the jellyfish reduce their income by killing or stunning fish and shrimp caught in their nets.

The species, known as Stomolophus nomurai, was discovered in the East China Sea. The fact that representatives of this species have appeared from time to time in the Sea of ​​Japan between Japan and the Korean Peninsula since 1920 is associated with an increase in water temperatures, they say. Jellyfish, which can reach a length of up to 5 meters, have poisonous tentacles, but are not fatal to humans.

The most poisonous jellyfish can kill 12 people at once, they live in Australia

Jellyfish gene in potato gene

As a result of achievements genetic engineering It became possible to insert the gene... of a jellyfish into the genome of a potato plant! Thanks to this gene, the body of the jellyfish retains fresh water, and if there is a lack of water in the soil, potatoes with this gene will also retain water. In addition, thanks to this gene, the jellyfish glows. And this property is preserved in potatoes: when there is a lack of water, its leaves glow green in infrared rays.

Sea feathers Pennatularia

There are about 300 species of polyps called sea feathers (Pennatularia) in the world's oceans. Each polyp consists of many eight-tentacled individuals sitting on one common thick stem. Sea feathers live at depths from 1 to 6 thousand m. At greater depths, specimens up to 2.5 m long are found. Sea feathers are able to glow due to the special mucus that covers them on the outside. It has been noticed that the mucus does not lose its ability to glow even when dried.

Sea anemone Actiniaria

The distribution of sea anemones (Actiniaria), six-rayed corals, depends on the salinity of the sea water. For example, in the North Sea there are 15 species, in the Barents Sea - 10, in the White Sea - 5-6 species, in the Black Sea - 4 species, and in the Baltic and Seas of Azov there are none at all.

Sea anemone and clown fish

Hydra is a "stray stomach" equipped with tentacles

This is a real monster. Long tentacles armed with special stinging capsules. A mouth that stretches so that it can swallow prey much larger than the hydra itself. Hydra is insatiable. She eats constantly. Eats countless amounts of prey, the weight of which exceeds its own. Hydra is omnivorous. Both daphnia and cyclops and beef are suitable for her food. In the fight for food, the hydra is ruthless. If two hydras suddenly grab the same prey, then neither will yield.

Hydra never releases anything caught in its tentacles. The larger monster will begin to drag its competitor towards itself along with the victim. First, it will swallow the prey itself, and then the smaller hydra. Both the prey and the less fortunate second predator will fall into the super-capacious womb (it can stretch several times!). But the hydra is inedible! A little time will pass and the larger monster will simply spit out its smaller brother. Moreover, everything that the latter managed to eat himself will be completely taken away by the winner. The loser will see the light of God again, having been squeezed to the very last drop of anything edible. But very little time will pass and the pathetic lump of mucus will again spread its tentacles and again become a dangerous predator.

Exceptional survivability common hydra brilliantly demonstrated in the XYIII century. Swiss scientist Tremblay: using a pig's bristle, he turned the hybra inside out. She continued to live as if nothing had happened, only the ectoderm and endoderm began to perform each other’s functions.

Corals grow very quickly. So, one favia larva ( favia) in a year produces a colony with an area of ​​20 sq. mm and a height of 5 mm. There are corals that grow even faster. Thus, one of the ships that sank in the Persian Gulf was covered with a coral crust 60 cm thick within 20 m.

The biggest sponge, barrel-shaped Spheciospongia vesparium, reaches height 105 cm and 91 cm in diameter. These sponges live in the Caribbean Sea and off the coast of Florida, USA.

Excitation propagation speed in different parts of the nervous system of coelenterates it is 0.04-1.2 m per second.

Hermaphrodites

Among those who are truly able to change gender at their own discretion are sea slugs, earthworms and the European giant garden worm.

Female worms simply inhale the small male

The females of one species of worm simply inhale a small male, who settles in a nook in the reproductive tract, from where he fertilizes the eggs.

Boys eat girls

In marine oligochaete worms, the boys eat the girls. Males guard the fertilized eggs until they burst, and since the female is destined to die after mating anyway, the male, without hesitation, eats her for dinner. This kind of concern - offering herself as dinner - is due to the fact that the female may want to receive guarantees that her offspring will survive.

The worm's blood is red, but different

All mammals have red blood due to the hemoglobin contained in red blood cells. There are no red blood cells in the blood of invertebrate animals. However, their blood may still be red (for example, ringworm, peskozhila), only hemoglobin is not enclosed in blood cells, but forms large molecules dissolved directly in the plasma. This blood is called hemolymph.

Blood is green

Some polychaete annelids have green hemolymph due to the pigment chlorocruonine, which is similar to hemoglobin. This pigment is not enclosed in blood cells, but forms large molecules dissolved directly in the plasma.

Canned worms for moles

There is less food in winter than in summer, and in order not to starve, moles store “canned food” of worms for the winter: they bite off their heads and wall them up in the walls of their holes, sometimes hundreds of them at once. Without heads, worms cannot crawl far, but they do not die, and therefore do not deteriorate.

Earthworms from Europe pose a threat to North America

The US Midwest, where there were no earthworms of their own due to massive glaciation that ended 10 thousand years ago, is particularly at risk. In these parts European species worms appeared only in the last century. Some of them turned out to be involuntary migrants, arriving on ships moored at ports on the Great Lakes. Others were specially imported as bait for fishermen.

Earthworms do not so much enrich the soil with oxygen and nitrogen as they damage the thin layer of humus in which an interconnected community of insects and microorganisms lives. Worms process forest litter around the clock. They digest it so quickly that they endanger the existence of other organisms at the beginning of the food chain, which in turn harms the higher organisms for which they serve as food.

The presence of earthworms in the soil in national park Chippewa have led to declines in populations of native insect species, small insectivorous mammals species such as the mouse vole and shrew, ground-nesting bird species (such as the ovenbird), and ultimately a reduction in the area occupied by sugar maple, a native forest-forming species.

Earthworms love buckthorn and can't stand oak trees.

Earthworms love to live in the roots of buckthorn, enriching the soil with nitrogen compounds that this shrub needs for normal life. Such a symbiosis of two species causes damage to other elements of the ecosystem. On the other hand, earthworms do not like the foliage of oak trees, in the plantings of which their number is minimal.

Worms can live up to 500 years

By carefully changing some genes and stimulating the production of certain hormones, scientists managed to extend the life of a laboratory worm several times. By human standards, the experimental worm lived an active and healthy life 500 years. The researchers claim that they have changed one of the main life-supporting mechanisms of the worm's body - the insulin metabolic system. This system is characteristic of many species, including mammals.

However, many people may decide that the price of immortality is too high. Worms that lived for 500 years had their reproductive systems removed.

The team of scientists from the USA and Portugal that conducted this experiment set a kind of record. They managed to help a living creature live the longest possible life. No one before them could achieve such a lifespan.

Males for asexual worms

The male gender is important even for inconspicuous people nematodes - Caenorhabditis elegans, soil worms that can reproduce asexually. Its dimensions are very modest (length less than the thickness of a human hair). The worms grow very quickly, turning from embryo to adult in four days. They also have another interesting property: almost 99.9% of the population are hermaphrodites - females with two X chromosomes, capable of producing sperm and self-fertilization. Indeed, in most cases it is more profitable for a species to self-fertilize rather than mate with males - sexual fertilization is costly in terms of time and energy. However, 0.1% of the population are males with one X chromosome. The presence of men is necessary for the survival of the species.

When living conditions deteriorate, males make a key genetic contribution to the survival of the species. The X chromosome coming from them determines the possibility of survival of the species. It turned out that, faced with starvation, about half of the hermaphrodite larvae conceived sexually turned into males, losing one of the X chromosomes. This turned the larvae into males who look different, live longer, and can pass on their genes through sperm. Worms conceived by self-fertilization did not have this ability. This means that sexually conceived worms can adapt better to a changing environment than hermaphrodites. In addition, an increase in the number of males reduces the number of offspring - which is effective when there is a lack of food. In addition, males live longer and survive better in difficult conditions - they can travel longer in search of food.

Best time for worms

Earthworms belong to the class Oligochaetes Annelida. Best time days to search for earthworms - the night when they crawl out of their holes. We must try so that the light of the lantern does not suddenly blind the animals, since in this case they will immediately hide in their holes. Mating earthworms lie side by side with their head ends in different directions, connected at the girdle region (an extension near the anterior edge).

16 tons of soil

Earthworms, living on half a hectare of garden, pass through their bodies about 16 tons of soil per year.

Worms are garbage eaters

It is known that in a day a worm processes as much organic matter into vermicompost as it weighs. Earthworms can be used to dispose of garbage. It can cleanse the soil of harmful elements, as it is capable of accumulating certain metals, including zinc, which is most toxic to microbes living in fallen leaves and pine needles. Namely, they make the soil suitable for all other organisms and plants. Worms stimulate their activity, help them breathe, absorbing the poisons that humans inject into the earth.

In Russia, there are three successful breeds of worms - “Vladimir”, “Petersburg” and “Bryansk” hybrids. They are extremely voracious - the “Petersburger” happily eats even urban sewage sludge if diluted with manure. According to researchers, worms can turn up to half of the food they eat into humus. The soil passed through their intestines contains almost no helminths and pathogenic microorganisms. But worms will not be able to clean city soil from arsenic compounds and heavy metals; they only assimilate zinc and cadmium well.

Worms on a hook feel no pain

At the usual earthworm The nervous system is very simple. A worm can be cut in half and it can continue to exist peacefully. When a worm is placed on a hook, it reflexively curls up, but it does not feel pain. He may be experiencing something, but this does not interfere with his existence.

Record for carrying heavy loads

A caterpillar can lift a load approximately 25 times heavier than its own weight, an ant 100 times, a leech 1500 times.

Four-toed worm

The reptile, which is called the "tatzelwurm" (four-toed worm) is a famous representative of the alpine reptiles. This animal, called "stollenwurm" (underground worm), was even listed in the "New Handbook for Lovers of Nature and Hunting", published in Bavaria in 1836. This book contains a funny drawing of a cave worm - a cigar-shaped creature covered with scales with a menacing toothy mouth and underdeveloped, stump-shaped paws. However, no one has yet managed to find and examine the remains or shell of this animal, which could be considered the largest European lizard.

According to the testimony of 60 eyewitnesses, the length of the animal’s body was approximately 60-90 centimeters, it had an elongated shape, and its back part sharply tapered towards the end. The animal's back had a brownish tint, and its belly was beige. It had a thick short tail, no neck, and two huge spherical eyes sparkled on its flattened head. His legs were so thin and short that some even tried to claim that he had no hind limbs at all. Some claimed that it was covered with scales, but this fact was not always confirmed. In any case, everyone was unanimous in the opinion that the beast hissed like a snake.

The only coelenterate animals in their group have stinging capsules, thanks to which they, if necessary, usually during irritation, throw the thread out of the body; it contains poison. It should paralyze any attacking animal, but this applies mainly to small individuals.

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

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

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

In coelenterate animals, there are two categories: those that lead an active lifestyle and those that are immobile. In general, people should avoid any encounters with these animals so as not to put their health at risk. For example, sea anemones are more like flowers; these animals have many tentacles that search for prey.

Wow!.. That's it!.. Be healthy!..

Coelenterates, like sponges, first appeared on earth more than 500 million years ago. They have multicellular organisms and the most in different forms. Coelenterates include sea anemones, jellyfish and corals.

general characteristics

The body of coelenterates has the shape of a sac with a hole, which is surrounded by tentacles. They can face up like polyps or down like 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 coelenterates communicates with the surface through a single opening, which serves for the intake of food and the release of undigested residues. Around the hole there are tentacles that capture, paralyze and pull prey inside.

Habitat

Coelenterates live in warm tropical seas; Some of them lead a sedentary lifestyle, others are free-swimming. Thus, hydroids can be both stationary (polyps) and floating (jellyfish); the scyphoid class consists only of jellyfish, and the class coral polyps These include only immobile forms - polyps living separately or in colonies. Coelenterates are multicellular organisms characterized by a simple structure and radial symmetry. This structure is very convenient for animals that are not able to move freely: both food and enemies can appear from anywhere, so it is important to be prepared for attack or defense from any side.

The body of all coelenterates consists of one internal cavity, communicating with the surface through an opening - the mouth, the walls of which perform respiratory functions, serve for eating and removing processed products.

The mouth is surrounded by tentacles containing 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; becomes their prey small fish and crustaceans. Due to the specificity of their body structure, coelenterates are well camouflaged at the bottom and become a sudden trap for their victims.

The type of structure of coelenterates (there are two main types - polyps and jellyfish) can change during the development of the animal: 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 polyp, like corals.

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

The ectoderm consists of elongated muscle cells, and the endoderm is round. The shooting motion characteristic of jellyfish is achieved by the activity of these two rows of cells, which stretch and contract. Such movements allow the jellyfish to move forward: compression pushes the water out from under the umbrella, and the jellyfish receives a jet push, like a rocket.

The remaining cells have transformed into nerve cells and envelop the surface of the body with a mesh, giving the jellyfish sensory organs.

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

There are 2,700 hydroid species; They are small in size, reproduce only by budding and come in two forms - polyps and jellyfish. They live isolated, like hydras, or in colonies, like hydrants.

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

Coral polyps are the class of coelenterates with the largest number of species - 6500 species. They are found only in the form of polyps, can be solitary, like sea 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 since ancient times in China and Japan; 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, at the end of the 19th century, corals were attributed to various healing properties: Coral powder was considered a panacea for many diseases.

Kinds

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 jewelry. It is even found in burials of the 4th century BC.

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

Hydra lives in fresh water. Due to its six thin tentacles, which are six times longer than the size of the hydra itself, it closely resembles algae. Looking at her, it is difficult to imagine that this innocent animal was identified in Greek mythology with a monstrous snake with nine heads that grew back every time they were cut off.

The structure of the jellyfish is interesting because this animal is 95% composed of water, and organic matter makes up only 5% total mass. If big jellyfish throw it onto land, it will completely “melt”, and after a few hours there will be nothing left on the sand except a small wet spot.

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

The sea pen, unlike its coral relatives, has a soft and flexible external skeleton, which makes it look like an elegant goose feather. It emits a bright blue-green color, which is why it received the Latin name pennatula phosphorea, translated into Russian as “phosphorous”.

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 cavolinii is a very rare coral found in the Mediterranean Sea. It lives in large colonies, and its branched “crown” reaches 70 cm in length. Unfortunately, the beauty of this coral attracts the attention of poachers.

In the Mediterranean Sea you can find Caryophylla clava, an isolated madrepora with a thin transparent body.