Interesting facts about coelenterates. The world of coelenterates. The worm's blood is red, but different

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• Type: Cnidaria (Coelenterata) Hatschek, 1888 = Coelenterates, cnidarians
• Subphylum: Anthozoa Ehrenberg, 1834 = Corals, coral polyps, non-jellyfish
• Class: Hexacorallia = Six-rayed corals
• Class: Octocorallia Haeckel, 1866 = Eight-rayed corals
• Subphylum: Medusozoa = Jellyfish-producing
• Class: Cubozoa = Box jellyfish
• Class: Siphonophora = Siphonophora
• Class: Scyphozoa Götte, 1887 = Scyphozoa
• Class: Hydrozoa Owen, 1843 = Hydrozoa, hydroids (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, the jellyfish, consisting of 98% water and in appearance, is one of the simplest life forms, but in fact it is capable of exhibiting complex nutritional, protective and many other reactions.

Coelenterates have organs of vision and balance, and are able to respond to environmental factors such as light, heat, mechanical, chemical and other influences. In this case, for example, in sea anemones, each part of the body has a characteristic reaction to certain type external influence. With her mouth she perceives chemical irritation without feeling mechanical impact, to which, however, the sole is sensitive. And the body walls and tentacles of the sea anemone respond to mechanical, chemical, and electrical influences. Thanks to a variety of devices and living “instruments”, 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.

"Device" for predicting storms

The jellyfish is known for its ability to sense the approach of a storm in advance using a device to detect infrasounds. These acoustic shocks with a frequency of 8-13 hertz are created by the pre-storm wind when the water slams on the crest of a wave. In humans, such infrasounds cause nervous tension. And they signal to the jellyfish’s body twenty hours before the storm begins that it is approaching. Thanks not only to the so-called “infraear”, but also to the signal recognition system, the jellyfish leaves the danger zone in time. Otherwise, its gelatinous body may be broken by storm waves on rocks or washed ashore.

The structure of the living “device” of the jellyfish interested bionics. Its bell-shaped body is equipped with eyes, balance organs, as well as auditory cones the size of a pinhead - the “ear” of the jellyfish. Its bell, like a megaphone, 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 a storm located hundreds of kilometers away. Based on the principle of operation of such a magnificent device as the “infraear” of a jellyfish, bionics have created an automatic device - a storm predictor. It allows you to avoid many of the terrible consequences of a storm, because... warns about it 15 hours in advance, and a traditional barometer only two hours in advance.

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 changing seasons, ebbs and flows. Moreover, this is not only a direct reaction to change external conditions. Such biological rhythms also occur 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 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 which organs, elements of the cell and organism 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”. Thus, sea anemone equina is able to determine the time of high and low tide with an accuracy of several minutes. Experiments in the aquarium made it possible to establish that the sea anemone blooms during high tide, opening its tentacles, and contracts them at low tide not only natural conditions. She retains this ability in a special aquarium. This rhythm in an artificial environment is very stable and persists for several days after the start of the experiment.

Ability to carry out coordinated movements

Some representatives of the coelenterates are sedentary attached animals. Others can change body shape and move thanks to coordination systems that allow targeted contractions and relaxations of specific muscle cells.

Type Coelenterates are multicellular individuals, inhabitants of water spaces, mainly seas. Some species have adapted to a sedentary lifestyle (attached to the bottom or substrate), others actively move, covering long distances.

There are more than 10,000 species of coelenterates. The diversity of coelenterates is very great: there are small individuals up to a couple of millimeters, and huge representatives are cyanea jellyfish, about two meters wide, and the tentacles reach 15 meters in length.

Why did coelenterates get 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 this is how the name coelenterates was formed.

Coelenterates are characterized by radial symmetry; 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 polyp wall 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 which perform a protective function. The capsule of the stinging cells contains a paralyzing poison; when danger approaches, toxic substances enter a special channel, which is located in the stinging thread and is directed to the victim’s body. After the poison spills out, the cell dies, a new one from intermediate cells begins to form;
• intermediate cells capable of constant division and transformation into specialized ones, this is how the body regenerates;
• germ cells– eggs and sperm are formed in ectodermal tubercles.

Endoderm

The second layer is the inner layer (endoderm). The ball of cells lines the intestinal cavity and 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 to break down 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.

Organs of coelenterates

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

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

Reproduction coelenterates go by budding; this is an asexual mechanism when the body is divided in the longitudinal or transverse directions. During sexual division, sperm and eggs enter the external environment where their merger occurs. First, the zygote is formed, and then the larva, the planula, emerges. 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 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 extend from the septa, which are in constant motion and ensure a regular change of water inside the polyp.

Continuous movement of water ensures high blood pressure in the intestinal cavity, so the polyps straighten and for a long time are in this position. When he gets tired, he changes his position by bending over or moving a short distance.

The body shape is similar to a bell, the contractile cells of which ensure the active movement of individuals in the water. Mesoglea is 98% water, the rest is connective tissue. Due to their high water content, jellyfish can easily stay in the aquatic environment.

At the bottom of the bell there is a mouth opening with oral lobes. With the help of the mouth, food is captured, which enters the intestinal cavity. It consists of many tubules that extend 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; there are eyes on the surface of the body that perceive light rays. If a jellyfish washes ashore, it will die due to complete evaporation of the water.

What stage of the life cycle of coelenterates contributes to their dispersal?

The dispersal of animals across the sea occurs at the larval and medusoid stages. During these periods of life, they are able to move or are carried away by the current. During the entire period of its existence, a polyp can only move a couple of meters, 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 spring-summer period reproduces asexually, buds develop on the body, which, when mature, leave the mother. Autumn is coming sexual reproduction, with the formation of an egg, which in the spring will give birth to new organisms.

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

Coral– organisms with an internal keratinized skeleton. Lead sedentary image life, reproduce by budding, without being separated from the mother’s body, or by sexual intercourse.

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

Compare the vital functions of coelenterates and protozoa using the table provided.

The role of coelenterates in nature

Participate in population regulation small fish, crustaceans, as they are food for coelenterates.

They are an integral part of the marine biocenosis.

Form Coral reefs– massive accumulation of madrepore corals. They are located near islands, gradually growing upward, forming islands (atolls).

Serve as raw material for lime extraction.

Coelenterate organisms can live in symbiosis with other animals. Sea anemones, which lead a sedentary lifestyle, often attach to crayfish and thus move faster. Cohabitation is also beneficial for cancer, since the sea anemone protects it from enemies.

The sea anemone's tentacles serve as a hiding place for small shrimp.

The importance of coelenterate organisms in human life

Widely used in Food Industry(edible jellyfish - cornerota). Every year the Japanese catch several thousand tons of Ropilem jellyfish, from which they prepare various dishes.

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

Coral reef islands become an obstacle to transport ships.

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

Among marine inhabitants, jellyfish are one of the most mysterious creatures. Meeting them can pose a mortal danger to humans, but even this does not stop researchers from trying to observe the life of these creatures and learn about how they live, reproduce, and feed. We offer a selection interesting information, which is known to the science of jellyfish.

One of the oldest and simplest organisms

Jellyfish are among the oldest organisms, with a history of existence of about 650 million years. They received their name in the 18th century. thanks to Carl Linnaeus, who saw their resemblance to the mythical Medusa Gorgon with snake-hair moving on her head. In American public aquariums, the term “jellyfish” is often used to refer to these creatures, although these creatures have nothing to do with fish.

These simple organisms lack cardiovascular, respiratory and central nervous systems. The functions of the latter are performed by nerve networks located in the epidermis, which make it possible to detect the touch of another or an organism. Respiratory functions are performed thin skin, which absorbs oxygen over the entire surface directly from the water.

Since they are primitive creatures, they do not communicate with each other in any way, even when sea currents knock them into large groups. Such clusters are called a swarm.

Body structure

Their body is 95-98% water, so existence outside aquatic environment impossible. It can be dome-shaped, umbrella-shaped, or disc-shaped and consists of a jelly-like substance called mesoglea. In the center of the lower part is the mouth, which is used both to absorb food and to remove its remains from the body. There are tentacles along its edges. Their type and quantity varies depending on the species: they can be thick and short or thin and long.

Interesting! The number of tentacles ranges from 4 to several hundred, but their number is always a multiple of 4, since these creatures are characterized by radial symmetry.

The tentacles are equipped with stinging cells containing poison. They make hunting easier and also perform a protective function, thanks to which these protozoa do not have many natural enemies.

Relationship with corals

No matter how surprising it may sound, but jelly-like Marine life and corals are close relatives. Both species belong to the marine animals of the coelenterate class. Even more interesting fact is that corals and jellyfish have a common parent - polyps. For coelenterate animals, two forms of existence are possible:

• polypoid - inherent in polyps and corals;
• medusoid - inherent in jellyfish, which are organisms derived from polyps.

On the left is Physalia (Physalia aretusa) - a colony of polyps, on the right is a jellyfish

The life cycle of medusoids begins with planulae - eggs fertilized by males. They drift freely in the water until they catch on a solid object: a reef, bottom, rock. Having attached itself to it, the planula forms a polyp. After several months or even years, the future body of the jellyfish is separated from it by the method of budding of ether, which will eventually turn into an adult organism.

Animals with "light"

These sea creatures do not have a central nervous system and sensory organs, but thanks to photosensitive cells they are able to distinguish light from darkness and navigate through the water column. Some of them have an interesting ability to glow in the dark, which allows them to lure prey in dark sea ​​depths. The body of luminous varieties contains a substance called luciferin, which is oxidized by luciferase and emits bright light. The color of the glow can be yellow, green, blue or cyan.

Unusual poison delivery system

Most venomous animals release their venom when they bite their prey. But this does not apply at all to jellyfish and other coelenterate organisms. Over millions of years of evolution, nature has awarded them with special organs - nematocysts - capsules with a poisonous liquid. The contact of the tentacles with the intended prey activates the nematocysts, and they release thousands of microdoses of poison into the victim’s body. This process lasts about 3 milliseconds and is considered one of the fastest actions among living organisms.

The effect of the poison kills small animals, and can have a paralyzing effect on large ones, which allows them to escape in case of danger. Some representatives of the species are “armed” with the strongest poisons, which, in terms of the degree of danger to humans, are among the most toxic natural substances.

An interesting fact is that the tentacles of poisonous individuals pose a danger not only during the life of jellyfish, but also for a long time after their death.

Way to travel

Despite the simplicity of their body structure, jellyfish are able to move in water on their own, although they do so very slowly. Muscle fibers are used for these purposes. Working like a pump, they draw water into their dome and then contract and throw it out. As a result, a powerful recoil is formed, pushing the animal in the direction opposite to the release of water. In this case, jelly-like bodies can move up, down or diagonally, but are not able to move in the horizontal plane. They use their ability quite rarely and prefer to remain idle most of the time, drifting along with the ocean current.

Benefit for humanity

In the selection of the most interesting facts about jellyfish, it is worth mentioning their use for the benefit of people. Back in the Middle Ages, some varieties were used to make laxatives and diuretics. Today, the venom from the tentacles is used as a raw material in drugs to regulate blood pressure and treat lung diseases. Farmers who farm on Caribbean Islands, use physalia poison as a poison for rodents.

The Japanese are confident that these simple sea creatures can help in the fight against stress. They are bred in special aquariums, which is quite a troublesome and expensive task. But in Japan they consider this to be completely justified, since the smooth and measured movements of jellyfish domes have a calming effect on people.

In Japan, as well as China, Korea and Indonesia, they are called “crystal meat” and eaten. Only the “umbrellas” themselves are considered edible, while the tentacles are usually thrown away.

Unique representatives

Currently, science knows about 3,000 species of these simple creatures. Not all of them belong to well-studied organisms, since many live at depths of up to 10,000 km. Among this diversity, the most interesting individuals deserve special attention, facts about which force us to take a fresh look at jellyfish.

The biggest

The hairy cyanea is the most gigantic creature, perhaps not only among jellyfish, but among all creatures. In 1865, an individual with a dome of about 2.28 m and a tentacle length of 36.5 m was discovered on the shores of Massachusetts Bay, while until that time the main record holder among animals was considered blue whale with a body length of up to 34 m. Cyaneas live in cold waters. Like many of their relatives, they are poisonous, but do not represent mortal danger for a person. The poison only causes a painful burning sensation and blisters on the skin.

The smallest

Irukandji are miniature creatures with a 12-20 mm dome and long transparent tentacles up to 1 m long. Despite their mini size, they are deadly to humans. Their venom is 10 times more toxic to the body compared to cobra venom. However, it has a delayed effect, so doctors often fail to connect its effect with an irukandji bite. The list of symptoms includes excruciating pain in the back and joints, profuse sweating, nausea and vomiting, and tachycardia.

The most dangerous

The sea wasp is one of the most dangerous organisms for humans living on our planet. Even light touch sea ​​wasp tentacles are fraught fatal, and in total the poison in her body is enough to kill at least 50 people. Interesting fact: the size of the wasp's tentacles is 10-20 cm in length and 5 mm in thickness, but during an attack they can stretch up to 3 m, turning into thin needles. Dangerous jellyfish live in warm waters Australia and Oceania. Main danger for swimmers and divers is that the sea wasp is almost transparent, so it is difficult to notice in the water column.

The only freshwater

Kraspedakusta is a river inhabitant whose homeland is the river. Amazon. With the help of trading ships transporting exotic plants from South America, she successfully “reached” European waters.

Scientists were able to discover an interesting fact about kraspedakust, which expresses the dependence of numbers on average temperature in summer. In years with the hottest summer season, jellyfish appear in many freshwater bodies of Europe as far as the Urals. In case of cool weather, they can rarely be seen even in the reservoirs of Southern Europe.

Immortal

Turritopsis nutricula are unique creatures in which the aging process as such is absent. If the life cycle of their relatives ends after reproduction, then the nutricular cells then experience cell degeneration and re-transformation into a polyp - the initial stage of the life cycle. Supposedly, this cycle can repeat itself forever, which is why scientists consider Turritopsis nutricula to be an immortal jellyfish and possibly the only creature on Earth with such an ability.

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 see in cloudy 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 hunting 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)
- V life cycle usually the polyp and jellyfish stages 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)