• Type of: Cnidaria (Coelenterata) Hatschek, 1888 = Coelenterates, Cnidaria
• Subtype: Anthozoa Ehrenberg, 1834 = Corals, coral polyps, non-producing jellyfish
• Class: Hexacorallia = Six-pointed corals
• Class: Octocorallia Haeckel, 1866 = Eight-pointed corals
• Subtype: Medusozoa = Medusoproducing
• Class: Cubozoa = Box jellyfish
• Class: Siphonophora = Siphonophores
• Class: Scyphozoa Götte, 1887 = Scyphozoa
• Class: Hydrozoa Owen, 1843 = Hydrozoa, hydroid (Hydra)

Type: Cnidaria (Coelenterata) Hatschek, 1888 = Coelenterates, cnidarians

The world of coelenterates are amazing living creatures with a complex body structure and well-controlled behavior. Although, a jellyfish, consisting of 98% of water, looks like one of the simplest forms of life, but in fact it is capable of exhibiting complex food, protective and many other reactions.

Coelenterates have organs of vision and balance, are able to respond to environmental factors such as light, heat, mechanical, chemical and other influences. At the same time, for example, in sea anemones, each part of the body is characterized by a reaction to a certain type of external influence. Through the mouth, she perceives chemical irritation, without feeling the mechanical effect, to which, however, the sole is sensitive. And the walls of the body and the tentacles of anemones respond to mechanical, chemical, and electrical influences. Thanks to a variety of devices and living "devices", these living beings are able to respond to these external signals with an adequate response and carry out purposeful movements. Let's look at some examples.

"Instrument" for predicting a storm

The jellyfish is known for its ability to sense the approach of a storm ahead of time using an infrasound pickup device. These acoustic impacts with a frequency of 8-13 hertz are created by the pre-storm wind when the water collapses on the crest of the wave. In humans, such infrasounds cause nervous tension. And to the body of a jellyfish, they signal about its approach already twenty hours before the start of the storm. Thanks not only to the so-called "infra-ear", but also to the signal recognition system, the jellyfish leaves the danger zone in time. Otherwise, her gelatinous body can be broken by storm waves on stones or thrown ashore.

The device of a living "device" of a jellyfish interested bionics. Her body, which looks like a bell, is provided with eyes, organs of balance, as well as auditory cones the size of a pinhead - the “ear” of a jellyfish. Its bell, like a mouthpiece, amplifies the infrasound that occurs before bad weather. Then it is transmitted to the auditory cones of the jellyfish, and she hears the echoes of the storm, located hundreds of kilometers away. On the principle of operation of such a magnificent device as the “infra-ear” of a jellyfish, bionics have created an automatic device - a predictor of storms. It allows you to avoid many of the terrible consequences of the storm, because. warns about it in 15 hours, and the traditional barometer - only two hours.

The biological clock"

The life activity of many living beings is cyclical and is triggered by certain key stimuli. One of the most important cycles is the alternation of day and night. Other cycles are associated with the change of seasons, high and low tides. Moreover, this is not only a direct reaction to changing external conditions. Such biological rhythms are carried out in artificial conditions due to the presence of internal “biological clocks” in living organisms. They involve the most complex multifunctional structures and mechanisms: systems for analyzing the situation in the external and internal environment of the body; mechanisms of inclusion of certain nervous and other components; regulators of periodically manifested behavioral acts and much more.

Scientists still do not know where such “clocks” are located, with what organs, elements of the cell and body they are connected, what is the nature of the processes occurring in them, what underlies their “course” - physical or chemical changes. And, despite the complexity of such systems, the "primitive" organism of the coelenterates has a very accurate biological "clock". So, anemone equina is able to determine the time of the onset of high tide and low tide with an accuracy of several minutes. Experiments in the aquarium made it possible to establish that the sea anemone blooms at high tide, opening its tentacles, and reduces them at low tide, not only in natural conditions. She retains this ability in a special aquarium. Such a rhythm in the artificial environment is very persistent and persists for several days after the start of the experiment.

Ability to carry out coordinated movements

Some representatives of the intestinal cavities are sedentary attached animals. Others can shape-shift and move around using coordination systems that allow targeted contraction and relaxation of specific muscle cells.

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.

Comparative table of differences between flatworms and intestinal animals
Characteristic	Type Intestinal	flatworms
Habitat	Water environment
Category	Multicellular
body structure type	Radial symmetry	Bilateral symmetry
Wall structure	two layers of cells	Three layers of cells
Organs and systems	The presence of only specialized cells: muscle, nerve, reproductive	Common to all representatives

Flatworms have a more complex structure and developed differentiation of tissues and organs. But representatives of the intestinal cavities 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.

Comparison of the vital activity of coelenterates and protozoa
Characteristic	Coelenterates	Protozoa
Category	Multicellular	Unicellular
Habitat	Water environment	soil, water
Movement	By contracting muscle cells	Due to flagella and contractile vacuoles
specialized cells	Present	Missing
Food	Heterotrophs
reproduction	Sexual and asexual
Breath	body surface

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).

Atolls - islands of coral reefs

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

Paradoxically, the most dangerous sea creatures for us turned out to be also the most delicate and fragile. Sea wasp, small chiropsalmus jellyfish ( Chiropsalmus quadrigatus), living off the coast of Southeast Asia, kills a person within a few seconds; to do this, she just needs to touch him with her tentacles. The sea wasp belongs to the type of animals called coelenterates, or cnidarians, - these are jellyfish, corals, hydroids, sea anemones and their relatives. All these animals are poisonous, although not all of them are dangerous to humans. Many coelenterates compete with flowers in beauty and grace - outwardly they are more like plants than animals.

Coelenterates are one of the most primitive types of living beings on Earth. In total there are about nine thousand species; most coelenterates live in the sea and only a few species live in fresh water. Among these latter is the hydra, a tiny polyp often shown to students as a typical coelenterate. Hydra is a creature of microscopic dimensions, and, nevertheless, it retains all the signs of the structure of the coelenterates. The hydra has a hollow sac-like body, the shell of which consists of two layers of cells - the outer layer and the inner, digestive one - separated by an elastic layer that allows the polyp to maintain its shape. Inside the shell is the digestive cavity. It communicates with the environment through a hole that serves both to draw food in and to throw out waste. This hole is surrounded by a fringe of thin tentacles armed with stinging cells.

Polyps come in a wide variety of sizes; the smallest of them are no more than a dot on this page, but there are also quite large ones. The polyps that build coral reefs and create entire islands in the ocean are just tiny hollow droplets of living protoplasm armed with microtentacles. Nevertheless, it was they who built the Great Barrier Reef in Australia - the largest solid formation on the planet. This reef covers an area of ​​more than 200 thousand square kilometers; tiny polyps built it for about a million years.

Coral reefs form more or less quickly only in clear water, because fine particles settling from muddy water retard the growth of polyps. The rate of their growth is also affected by the illumination of the water - that is why at a depth of more than 30 meters there are already much fewer corals, and beyond 60 meters they disappear completely.

Each coral polyp lives inside a tiny calcareous cup that it builds for itself by extracting the right chemicals from the sea water and making a calcareous secretion out of them. The lower part of the polyp's body is attached to the substrate, which serves as the foundation of its calyx. Most polyps are brightly colored, but since they usually spend all day inside their cups, the true beauty of coral reefs can only be appreciated at night, when the polyps emerge from the cups, coloring the reef in orange, green, brown tones. A coral becomes white only when all the polyps that make it up die.

Apparently, coral polyps build large reefs only if they are aided by mysterious micro-organisms called zooxanthellae; zooxanthellae have features of plants and animals at the same time. Inside each polyp, thousands of photosynthetic zooxanthellae live, helping the polyp process the carbon dioxide it emits.

Polyps also have another assistant in the construction of reefs - algae included in the genus Lithothamnium. These algae cover the coral buildings in large patches; they release lime, which is also used to build the reef. A growing reef is as if covered with living skin - polyps live only on its outer surface. And under this skin lies a conglomerate of dead polyps, shells and all kinds of waste and debris, from year to year settling on the seabed. All this building material is also held together due to the presence of a huge number of polychaete worms, which build tubular formations from sand cemented by their metabolic products.

The structure of the body of a polyp can serve as an example of the structure of all intestinal, including jellyfish - with the only difference being that the tentacles of the jellyfish hang from the lower edge of the gelatinous bell, which, in essence, is similar to the bag-shaped elongated body of the hydra. Coelenterates live both in colonies and as individuals. Some coelenterates are tubular, hydra-like polyps with one end open and the other attached to the substrate. Other intestinal cavities - such as jellyfish, for example - swim freely. Many coelenterates go through both of these stages in their development.

From the point of view of biology, coelenterates are primitive creatures; nevertheless they are first-class hunters. Their tentacles are armed with so-called nematocysts - stinging cells, which, upon receiving a signal, throw out tiny poisoned "harpoons". The nematocyst is an oval capsule with a lid. A coiled hollow thread is hidden under the lid, inside of which there is poison. A sensitive hair protrudes on the outer surface of the capsule - the so-called knidocil, which serves as a kind of fuse for this miniature harpoon gun. Having received a signal, the capsule drops the lid and literally turns inside out, firing a stinging thread. The signal that "ignites the fuse" is, apparently, some kind of chemical substance, and not a mechanical effect on the cnidocil. (In the course of laboratory experiments, it was possible to make the capsule "shoot" in response to a chemical signal. In addition, there is no doubt that clown fish and other fish living with coelenterates accidentally touch nematocysts, but the capsule does not react to this.) the end of the stinging thread penetrates the body of the intended victim, poison immediately pours out of the thread. The name "cnidarians", by the way, comes from the Greek word "knidos", that is, "thread". A colony of coelenterates can simultaneously throw out several thousand poisonous threads that paralyze the victim; most coelenterates are not able to pierce human skin with threads, but those few animals that can do this pose a serious, sometimes deadly danger.

There are approximately seventy types of coelenterates that are dangerous to humans. In appearance, their tentacles are gentle, like a thin cobweb, but this impression is deceptive: their touch burns like fire. The excruciating pain that follows such a touch is apparently due to the presence of a substance from the group of histamines that enters the human skin: it causes pain, leaving bright stripes on the skin. The impact of the most powerful poisons secreted by intestinal cavities leads to the most unpleasant phenomena - from headache and nausea to cessation of breathing and cardiac arrest.

Among the hydroids, that is, in the class of intestinal cavities to which the harmless hydra belongs, there are also several extremely poisonous species.

An example of hydroids are polyps living in luxurious, branched colonies; the appearance of these polyps is deceptive: they can be mistaken for plants. At great depths, there are colonies of tree-like hydroids; such colonies sometimes reach the height of human growth; but those colonies of hydroids, which, like a fringe, are overgrown with coastal stones and piles, sometimes do not exceed a few centimeters in length. This fringe is painted in bright, eye-pleasing tones - crimson, pink, red. Of the two thousand seven hundred species of hydroids, most are quite harmless, but a few are capable of causing very unpleasant sensations. Hydroid Pennaria tiarella, for example, it stings like nettles, leaving a mark that does not go away for several days. This hydroid is found off the coast of California; scuba divers often see how its branches sway in the jets of underwater currents, like a fern in the wind. Of all the hydroids, this is perhaps the most poisonous.

Much more dangerous are the poisons of the notorious "burning corals", which in fact do not belong to corals at all, but are relatives of hydroids. They are colonies of polyps that look like huge, branched calcareous trees. The most dangerous of these polyps is hydrocoral M. illepora alcicornis, which is distinguished by such subtle beauty that many, at the sight of it, cannot resist the temptation and break off a piece as a keepsake. This should not be done - not only because we spoil the beauty of the underwater reef, but also because the "burning coral" burns like white-hot iron.

I heard a story about a man who fell victim to millepora and perhaps deserved punishment from the "burning corals". This story was told to me by one of my friends, an experienced scuba diver who was accompanying a group of tourists on an underwater tour of a delightful reef off the northeast coast of Puerto Rico. Before starting the dive, the group leader warned tourists that in order to preserve the underwater wealth of the area, local authorities forbade breaking off coral branches. However, one of the tourists apparently decided that getting a souvenir was more important than keeping a branch in the underwater forest. He spent only a few minutes in the water and soon returned to the tourist boat on which his wife was sunbathing. Quickly climbing on deck, he surreptitiously took out a piece of millepora from the swimming trunks and showed it to his wife. In less than five minutes, he began to roll on the deck, holding his lower abdomen and howling, as if he had been burned alive. The illegally obtained souvenir turned out to be a piece of "burning coral".

Not always touching this type of polyp causes severe pain. Dr. Martin Stempien of the Osborne Laboratories, while inspecting a reef in the Virgin Islands, unexpectedly stumbled upon a colony of "scorching corals". He felt the crevice and suddenly felt a burning sensation, as if he had scalded the skin between his fingers. However, the pain, according to Dr. Stempien, was not very strong.

The graceful tree structures of hydrocorals are home to billions of polyps that live in tiny pores that dot the coral's branches. Each colony has two types of polyps - large, large-mouthed polyps that extract food particles from the water for the entire colony, and small polyps that lack a mouth opening, but burn anyone who touches them.

The most famous of the hydroids - the widespread Portuguese boat, or physalia, - does not look like hydrocorals or other hydroids. Many consider it a jellyfish, but in fact it is a huge floating colony of polyps. It is made up of many different types of polyps, each type performing a specific function for the common good. Some polyps form a bright blue float, or pneumatophore, crowned with a pink crest. It is the pneumatophore that is the most noticeable part of the physalia, which floats at the behest of the wind on the surface of the sea. Below it hang "upside down" groups of other polyps, followed by a long - sometimes up to 30 meters - tail of tentacles. These tentacles, armed with whole batteries of nematocysts, blend in color with the ocean water and are often almost invisible. As soon as the tentacles touch a nearby fish, millions of capsules shoot their tiny poisonous "harpoons" at it, paralyzing the victim.

The fate of the fish that fell into the "paws" of the physalia is unenviable. The tentacles contract slowly, dragging the stunned but still alive prey towards the colony, where the gaping mouths of feeding gastrozoan polyps await. Their mouth openings are surrounded by a sticky ring and a battery of nematocysts. As soon as such polyps touch the fish, their mouth openings immediately stick to it. The tentacles contract, acquiring a blue color, and pull the fish close to the gastrozoids, after which the ill-fated fish disappears from sight; polyps-gastrozoids cover the entire surface of her body; the digestive cavities of the polyps turn outward and begin to digest the prey, providing nutrients to the entire colony. Once digestion is complete, the polyps regurgitate the remains of their prey; usually these are a few small pieces that settle to the bottom of the sea, joining the "rain" of organic matter, which constantly falls on the silt, enriching it.

Oddly enough, there is a fish that loves to hide among the tentacles of the physalia. This is a shepherd fish, or nomei ( Nomeus gronovii); how she escapes death remains a mystery to us. Either she knows how not to touch the nematocysts, which is unlikely, or she is simply immune to their poison. Perhaps some features of the nomei prevent the attack of the nematocysts; however, from time to time this fish, for some reason, becomes the prey of the physalia that sheltered it.

When bathing, people often come across a Portuguese boat, and it burns many; but only a few cases are known when this colony of polyps became the culprit of human death. Nevertheless, it should be remembered that the Portuguese boat is dangerous - even when it lies on the shore, thrown by the surf. Touching it causes almost instantaneous sharp pain, which is said to be similar to that of an electric shock. The skin at the point of contact swells, sometimes the victim begins to feel feverish and nauseous, and in some cases paralysis may even occur.

Suffered from a collision with a Portuguese boat and Nixon Griffis, scuba diving off the coast of the Florida Keys. Rising to the surface, Griffis saw several floating colonies right above his head. He kept a close eye on the nearest of them, but accidentally touched the tentacles of another colony, and they stuck to his hand. Griffis managed to get out of the water, but his arm hurt badly for another five hours.

My friend Carol Sanders told me about her unpleasant encounter with physalia. “It was in 1957,” she said, “on a beach in Miami Beach. About twenty meters from the shore, I noticed an object that looked like a beautiful bathing cap. It floated on the surface, and I swam to it, but when there was nothing left between us about two meters, I suddenly felt a sharp, unbearable pain in my arms and legs. It was like a burn and an electric shock at the same time. I was horrified to see that bright purple tentacles were wrapped around me. I swam with all my might back to the shore and tried to throw tentacles, moving my arms and legs along the sandy bottom. My strange movements and cries attracted the attention of the curious, but there was no sense from them. my friend, who was also on the beach, did not lose his presence of mind and, wrapping his hand in a towel, tore off my physalia.

The pain tormented me for several hours, and the white stripes, similar to scars left by a whip, lasted for several days. The hotel roommates, who had been in no hurry to help me when they crowded around me on the beach, now generously advised me, urging me to sue the hotel administration for not following the order of the city authorities and not hanging a poster on the beach with depiction of a Portuguese boat. When I returned to New York, I regretted not following their advice, because five days after the collision with the ship, I developed such a severe allergy that I was taken away in an ambulance.

Real jellyfish, which are classified as scyphoid ( Scyphozoa), are not colonies of polyps, like physalia, but single, independent animals. The bell or umbrella that makes up the body of the jellyfish is surrounded by a fringe of tentacles; the bell, rhythmically contracting and blooming, serves as the mover of the jellyfish, and its tentacles catch the fish swimming by. The victim receives a dose of paralyzing poison, is pulled up to the mouth opening leading to the stomach, located in the cavity of the bell, and is digested there. Jellyfish catch and eat quite large prey for their size. The largest of the jellyfish is the polar jellyfish cyanide ( Cyanea arctica), whose bell reaches 2.5 meters in diameter, and the tentacles are 60 meters long. No case has yet been recorded of a polar jellyfish burning a person with its tentacles, but given their length and the relative size of the fish that jellyfish eat, it can be assumed that this monster is able to catch a person and stick it in its stomach.

Smaller species of cyanide are found off the east and west coasts of the United States, as well as in other areas of the oceans. Many of them burn the skin quite badly; the poison of one species - the so-called pink jellyfish ( Suanea capillata) - causes loss of consciousness and, judging by some reports, even death. Some scientists classify the pink jellyfish and the giant polar jellyfish as the same species. Off the coast of America, there is also an eared jellyfish, or Aurelia ( Aurelia aurita), the bell of which reaches a diameter of 15 centimeters; the touch of an eared jellyfish is also very painful.

The most venomous of the jellyfish, and probably the deadliest of all known sea dwellers, is the sea wasp, the terror of Australian beaches. It is the size of a small balloon. The sea wasp kills within seconds. In 1966, the venom of this jellyfish was isolated in the laboratories of the University of Queensland. Having penetrated into the blood of a person, it reaches the heart muscle, and if the dose of poison was large enough, paralysis of the heart occurs within thirty seconds after being touched by a jellyfish.

One of the victims died even less than thirty seconds after being stung by a sea wasp. Another managed to run ashore screaming and died only an hour later. Probably, the pain caused by a burn of this kind surpasses all other pain sensations that only fall to the lot of a person. In Australia, dozens of people have been affected by the venom of the sea wasp; many of them have died. An 11-year-old girl, wandering on the water 10 meters from the shore, was stung in the leg and died a minute later. A few years ago, on a beach near Cairns, in Queensland, a man was teaching his young son to swim and didn't notice when the boy was touched by a sea wasp. The boy screamed in pain and was immediately taken to the hospital. But less than half an hour later, he died, despite all the attempts of doctors to support his cardiac activity.

The day this boy died was calm and cloudy. In such weather, the tide often carries sea wasps into shallow water; experienced people do not bathe these days.

The largest number of species belongs to the third class of coelenterates - to coral polyps Anthozoa. Animals belonging to this class are less poisonous than representatives of the first two classes. Coral polyps include gorgonians, sea feathers, sea anemones - where they "grow", the underwater world resembles fairy gardens - and many types of corals. Only sea anemones and several types of corals can cause trouble to a person.

Anemones and corals are closely related. Anemones, whose sizes range from a few millimeters to 15 centimeters, are also called sea anemones - after the name of small forest flowers; these polyps can indeed be considered the flowers of the underwater kingdom: they sway on long, thickened stems, which are crowned with tentacles resembling thin flower petals; however, the sea anemone also has a mouth that looks like a narrow gap. The "petals" of anemones are painted in bright colors - pink, red, white, purple, yellow, brown. Attached to the bottom or to stones and shells lying on the bottom, sea anemones gracefully sway their "petals" like flowers in the wind.

Fish and other small marine animals that inadvertently approach these "flowers" are met with tentacles dotted with nematocysts. Like other coelenterates, sea anemones paralyze the victim and then pull it to the mouth. In several species of anemones, the poison is so strong that it can hurt a person. This is, for example, pink anemone ( Sagartia elegans), living in European waters, and common sea anemone ( Actinia equina), which is found in the eastern regions of the Atlantic Ocean.

Corals build their huge reefs only in those areas where the temperature is never below 21° Celsius; they are very delicate polyps living in tiny calcareous calyxes. I think anyone who has been scuba diving in tropical waters knows how painful cuts are from accidentally or carelessly touching coral. If these cuts are started, they begin to suppurate, and then their treatment is delayed for several months. And some types of corals sting painfully. The most common of these is the acropora coral, which is sometimes called "deer antlers" ( Acropora palmata); The branches of this coral can be seen at a depth of 1.5 to 10 meters.

The polyps that build coral reefs hide in their cups during the day, but at night they stick out and color the reefs with yellow, green and red patterns.

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

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

The most numerous predators

According 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. They were primitive invertebrates, worms and jellyfish. Since then, the jellyfish has been one of the most numerous predators on Earth. First, the jellyfish absorbs everything that it finds on its way in close proximity. Then he makes a stop. It rises from the depth to a meter or two and keeps the reverse course. 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, hearts, lungs, and most other organs. Jellyfish have a mouth, often located on a stalk and surrounded by tentacles. The mouth leads to a branched intestine. And most of the body of a jellyfish is an umbrella. Tentacles also often grow on its edges.

Gelatin form of being

Thanks to the original jelly-like form, the buoyancy potential is used in the jellyfish. A particularly rigid body in the ocean is not necessary: ​​here in the aquatic environment, marine life has nothing to bump into.

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

Jellyfish eat crabs?

Medusa muscles

The umbrella of a jellyfish consists of a gelatinous elastic substance. It contains a lot of water, but there are also strong fibers made from special proteins. The upper and lower surfaces of the umbrella are covered with cells. They form the covers 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 the skin). Secondly, they are all alive (we have dead cells on the surface of the skin). Thirdly, the integumentary cells of jellyfish usually have muscular processes; therefore they are called skin-muscular. These processes are especially well developed in cells on the lower surface of the umbrella. The muscular processes stretch along the edges of the umbrella and form the annular muscles of the jellyfish (some jellyfish also have radial muscles located like spokes in an umbrella). When the ring muscles contract, the umbrella contracts, and water is ejected 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 false. Jellyfish have complex sensory organs (eyes and balance organs) and clusters of nerve cells - nerve nodes. You could even say that they have a brain. Only it is not like the brain of most animals, which is in the head. Jellyfish don't have a head and their brain is a ring of nerves with ganglions on the edge of the umbrella. Outgrowths of nerve cells extend from this ring, giving commands to the muscles. Among the cells of the nerve ring there are amazing cells - pacemakers. In them, at certain intervals, an electrical signal (nerve impulse) occurs without any external influence. Then this signal spreads along 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. A person has similar cells in the heart.

Jellyfish are constantly eating

Examining schools of herring spawning off the coast of British Columbia, biologists found that in one day the crystal jellyfish ate the entire herring offspring. In addition, jellyfish harm fish and those that devour their food. For a number of reasons, a huge number of jellyfish mnemopsis. Shortly thereafter, the herring catch dropped from 600 to 200 tons per year.

jellyfish flight

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

Because of the jellyfish, there will be more sprats

Scientists are starting an experiment in the Caspian Sea to introduce the Beroe jellyfish, which feeds on the comb jelly Mnemiopsis. It was he who caused the catastrophic reduction in the sprat population in the Caspian. Mnemiopsis was introduced with ballast water from the Sea of ​​Azov. Feeding on plankton, mnepiopsis undermined the food base for sprats for two years. As a result, it has become so scarce that the catches of this species of fish have decreased by almost ten times. 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, most of the fish factories of the Astrakhan region were focused on the processing of sprat.

Reasons for the growth in the number of jellyfish

In overfishing of commercial fish species - the main fighters of jellyfish. Among the main enemies of jellyfish are tuna, sea turtles, ocean moon fish and some ocean birds. Salmon does not disdain jellyfish either.

Abundance of jellyfish

In Chesapeake Bay, Maryland, there are so many jellyfish that you can’t do a single step near the shore. without stepping on them. The feeling is not pleasant - as if you are walking through thickets of nettles. The reason is the stinging cells of jellyfish.

In 2002, on the French Cote d'Azur, a large jellyfish pelagia purple-red color has bred in such numbers. That tore to shreds fishing nets with a total weight of over 2 thousand kg.

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

Fleeing from enemies, the jellyfish discards tentacles

Medusa colobonemaColobonema sericeum she discards 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. Kolobonema in its entirety can only be seen on the surface of the ocean. This is a small jellyfish, its dome diameter is 5 cm. The same thing happens with a lizard when it is grabbed by the tail. When swimming, the jellyfish moves in a jet way - 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 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 cyanide jellyfish bell reaches two meters, and the length of the filamentous tentacles is 20-30 meters.

Extreme jellyfish
Lake Mogilnoye on the island of Kildin near the Kola Bay is a completely unique Arctic reservoir. It is located in close proximity to the sea, and sea water seeps into it. Sea and fresh water do not mix due to their 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, such as cladocerans daphnia and chidorus. Below, up to 12 m, lies a layer of sea water in which jellyfish, cod, and 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 her tentacles, a person dies in 1-3 minutes if medical assistance does not arrive in time. 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 action to that of the 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 form of protection is women's tights, which were once used by lifeguards at a surf 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 blamed for the Irukandji syndrome, which killed two tourists in Australia in 2002. It all starts with a bite, like a mosquito. Within an hour, the victims experience severe pain in the lower back, shootings all over the body, convulsions, nausea, vomiting, sweating profusely and coughing. 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 in captivity the jellyfish Carukia barnesi, which has a deadly sting. The captured jellyfish has passed the planktonic stage and is now kept in the aquarium. Getting the jellyfish to breed in captivity was the first stage in the development of the antidote. 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 over a meter in size and weighing about 100 kilograms have been observed off the coast of the city 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 jellyfish reduce their income because they kill or stun fish and shrimp caught in the net.

The species known as Stomolophus nomurai was discovered in the East China Sea. The fact that this species has occasionally appeared in the Sea of ​​Japan between Japan and the Korean Peninsula since 1920 is due to rising water temperatures, they argue. 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

The jellyfish gene in the potato gene

As a result of the achievements of 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 with 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: with a lack of water, its leaves glow green in infrared rays.

Sea feathers Pennatularia

About 300 species of polyps live in the oceans, which are called sea feathers (Pennatularia). Each polyp is a set of eight-tentacled individuals sitting on one common thick stem. Sea feathers live at a depth of 1 to 6 thousand m. At great depths, specimens up to 2.5 m long are found. Sea feathers are able to glow due to the special mucus that covers them from the outside. It has been observed that the mucus does not lose its ability to glow even when dried.

Anemone Actiniaria

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

Sea anemones and clown fish

Hydra is a "vagrant stomach" equipped with tentacles

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

The Hydra never releases what has fallen into its tentacles. A larger monster will begin to drag a competitor along with the victim. First, it will swallow the prey itself, and then the smaller hydra. Both the victim 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 back its smaller counterpart. Moreover, everything that this last one managed to eat himself will be completely taken away by the winner. The loser will again see the light of God, being squeezed to the very last drop of something edible. But very little time will pass and the pitiful lump of mucus will again straighten its tentacles and again become a dangerous predator.

Exceptional survivability common hydra brilliantly demonstrated in the 18th century. Swiss scientist Tremblay: with the help of a pig bristle, he turned the gibra inside out. She continued to live as if nothing had happened, only the ectoderm and endoderm began to perform the functions of each other.

corals grow very fast. So, one favia larva ( favia) per year gives a colony with an area of ​​20 sq. mm and a height of 5 mm. There are corals that grow even faster. So, one of the ships that sank in the Persian Gulf, for 20 m, was overgrown with a crust of corals 60 cm thick.

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

Speed ​​of propagation of excitation in different parts of the nervous system of the coelenterates is 0.04-1.2 m per second.

Hermaphrodites

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

Female worms simply inhale the small male

Females of one type of worm simply inhale the small male, which takes up residence in a nook in the reproductive tract, from where it fertilizes the eggs.

Boys eat girls

In marine oligochaete worms, the boys eat the girls. The 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 supper—is due to the fact that the female may want assurance 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 erythrocytes in the blood of invertebrates. However, their blood can still be red (for example, in an annelids, sandworm), 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 chlorocruonin, which is similar to hemoglobin. This pigment is not enclosed in blood cells, but forms large molecules dissolved directly in the plasma.

Worms in canned mole

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

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 the forest floor around the clock. They digest it so quickly that they threaten the existence of other organisms at the beginning of the food chain, which, in turn, damages the more highly organized creatures for which they serve as food.

The presence of earthworms in the soil in Chippewa National Park has led to a decline in the populations of native insect species, small insectivorous mammals such as field mice and shrews, ground-nesting bird species (such as the stovepiper), and eventually to a reduction in areas occupied by sugar maple, a local forest-forming species.

Earthworms love buckthorn and hate oaks

Earthworms love to live in the roots of buckthorn, enriching the soil with nitrogenous compounds that this shrub needs for normal life. Such a symbiosis of two species damages other elements of the ecosystem. On the other hand, earthworms do not like oak leaves, 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 the laboratory worm several times over. By human standards, the experimental worm lived an active and healthy life for 500 years. The researchers claim that they have changed one of the main life-supporting mechanisms of the worm's body - the insulin metabolism 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 500 years had their reproductive system removed.

The team of scientists from the USA and Portugal, which conducted this experiment, set a kind of record. They managed to help a living being live the longest possible life. Before them, no one could achieve such a life.

Males for asexual worms

Male sex is important even for inconspicuous nematode - Caenorhabditis elegans, soil worms that can reproduce asexually. Its dimensions are very modest (the length is less than the thickness of a human hair). Worms grow very quickly, turning from an embryo into an 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-fertilizing. Indeed, in most cases, it is more profitable for a species to self-fertilize, and not to 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 males is necessary for the survival of the species.

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

The best time for worms

Earthworms belong to the oligochaete class Annelida. The best time of day to look for earthworms is at night when they emerge from their burrows. 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 in the region of the girdle (expansion near the front edge).

16 tons of soil

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

Worms are garbage eaters

It is known that a worm per day processes as much organic matter into biohumus as it weighs itself. Earthworms can be used to dispose of garbage. It can cleanse the soil of harmful elements, as it is able to accumulate some metals, including zinc, which is most toxic to microbes living in fallen leaves and needles. Namely, they make the soil suitable for all other organisms and plants. Worms stimulate their activity, help to breathe, absorbing the poisons that people stuff the earth with.

In Russia, there are three successful breeds of worms - "Vladimir", "Petersburg" and "Bryansk" hybrids. They are extremely voracious - the "Petersburger" is happy to eat even the sediments of city sewers, if they are diluted with manure. According to researchers, worms can turn up to half of the food they eat into humus. The earth passed through their intestines contains almost no helminths and pathogenic microorganisms. But the worms will not be able to clean the urban soil from arsenic and heavy metal compounds, they only absorb zinc and cadmium well.

Worms on a hook don't feel pain

In an ordinary earthworm, the nervous system is very simple. A worm can be cut in half and it can continue to exist in peace. When the worm is put on a hook, it reflexively curls up, but it does not feel pain. Perhaps he is experiencing something, but this does not interfere with his existence.

Weight carrying record

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

four-toed worm

The reptile, which is called "tatzelwurm" (four-toed worm), is a well-known representative of alpine reptiles. This beast, called "stollenwurm" (underground worm), was even listed in the New Handbook for Nature and Hunting Lovers, published in Bavaria in 1836. In this book there is a funny drawing of a cave worm - a cigar-shaped creature covered with scales with a formidable toothy mouth and underdeveloped, in the form of stumps, paws. However, no one has yet been able 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 narrowed towards the end. The back of the beast had a brownish tint, and the 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 he was covered with scales, but this fact was not always confirmed. In any case, everyone was unanimous in their opinion that the beast hissed like a snake.