Aurelia jellyfish moves due to. Sea jellyfish

Jellyfish - very amazing creatures, causing an extraordinary attitude towards them. Jellyfish can be found in every sea, in every ocean, on the surface of the water or at a depth of many kilometers.

Jellyfish are the oldest animals on the planet, their history goes back at least 600 million years. In nature there is an incredible amount of diversity different types, but even now the emergence of new ones, previously unknown to scientists, is being recorded.

Jellyfish (Polypomedusae) are one of the phases life cycle cnidarians Medusozoa, which are usually divided into three types: hydroid, scyphoid and box jellyfish. Jellyfish reproduce sexually. There are males who produce sperm and females who produce eggs. As a result of their fusion, the so-called planula is formed - a jellyfish larva. The planula settles to the bottom, where over time it turns into a polyp (asexual generation of jellyfish). Having reached full maturity, the polyp begins to bud off a young generation of jellyfish, often completely different from the adults. In scyphoid jellyfish, the newly separated specimen is called ether. The body of jellyfish is a jelly-like dome, which, through contractions, allows them to move in the water column. Tentacles equipped with stinging cells (cnidocytes) with a burning poison are designed for hunting and capturing prey.

The term "jellyfish" was first used by Carl Linnaeus in 1752, as an allusion to the animal's resemblance to the head of the Gorgon Medusa. Becoming popular around 1796, the name began to be used to identify other medusoid species of animals, such as ctenophores.

A little interesting facts about jellyfish:

The world's largest jellyfish can reach up to 2.5 meters in diameter and have tentacles more than 40 meters long. Jellyfish are capable of reproducing both sexually and by budding and fission. Medusa " Australian wasp"is the most dangerous poisonous animal in the world's oceans. The venom of a sea wasp is enough to kill 60 people. Even after the death of a jellyfish, its tentacles can sting for more than two weeks. Jellyfish do not stop growing throughout their lives. Large concentrations of jellyfish are called “swarms” or “blooms.” Some species of jellyfish are eaten in East Asia, considered a “delicacy.” Jellyfish don't have a brain respiratory system, circulatory, nervous and excretory systems.
The rainy season significantly reduces the number of jellyfish living in salt water bodies. Some female jellyfish can produce up to 45,000 larvae (planulae) per day.

Pink jellyfish from the Scyphozoan family was discovered quite recently, a little over 10 years ago, in the waters of the Gulf of Mexico and the Caribbean. Some individuals of this species reach up to 70 cm in diameter. Pink jellyfish can cause serious and painful burns, especially if a swimmer inadvertently ends up among a large concentration of these creatures.

Antarctic Diplulmaris- one of the species of jellyfish of the Ulmaridae family. This jellyfish was recently discovered in Antarctica, in the waters of the continental shelf. The Antarctic Diplulmaris is only 4 cm in diameter.

Flower cap jellyfish(lat. Olindias Formosa) is one of the types of hydroid jellyfish from the order Limnomedusae. Basically, these cute creatures live off the southern coast of Japan. Feature- motionless hovering near the bottom in shallow water. The diameter of the “flower cap” usually does not exceed 7.5 cm. The tentacles of the jellyfish are located not only along the edge of the dome, but also over its entire surface, which is not at all typical for other species. A flower cap burn is not fatal, but is quite painful and can lead to severe allergic reactions.

Purple striped jellyfish(lat. Chrysaora Colorata) from the class Scyphozoa is found only near the coast of California. It's pretty large jellyfish reaches 70 cm in diameter, the length of the tentacles is about 5 meters. A characteristic feature is the striped pattern on the dome. In adults it has a bright purple color, in juveniles it is pink. Purple-striped jellyfish usually live alone or in small groups, unlike most other species of jellyfish, which often form huge colonies. The Chrysaora Colorata burn is quite painful, but not fatal to humans.

Giant Nomura jellyfish(Latin: Nemopilema nomurai) is a species of scyphoid jellyfish from the order Cornerotae. This species predominantly inhabits the East China and Yellow Seas. The size of individuals of this species is truly impressive! They can reach up to 2 meters in diameter and weigh about 200 kg. The name of the species was given in honor of Mr. Kan'ichi Nomura, general director fisheries in Fukui Prefecture. In early 1921, Mr. Nomura first collected and studied a previously unknown species of jellyfish. Currently, the number of Nomura jellyfish in the world is growing. Possible reasons population growth, scientists believe climate change, overexploitation water resources and environmental pollution. In 2009, a 10-ton fishing trawler capsized in Tokyo Bay with three crew members trying to remove nets overflowing with dozens of Nomura jellyfish.

Tiburonia granrojo- a little-studied species of jellyfish from the Ulmáridos family, discovered by MBARI (Monterey Bay Aquarium Research Institute) only in 2003. It lives at depths between 600 and 1500 meters in Hawaii, the Gulf of California and Japan. Thanks to its rich dark red color, this species of jellyfish has earned the nickname Big Red. The great red jellyfish is one of the largest species of jellyfish, its diameter ranges from 60 to 90 cm. Currently, only 23 individuals of this red giant have been found and studied.

Pacific sea nettle(lat. Chrysaora fuscescens) - has a bright characteristic golden-brown color, which is why it is often kept in captivity (aquariums and oceanariums). The name of the jellyfish genus Chrysaora goes back to Greek mythology. Chrysaor is the son of Poseidon and Medusa the Gorgon; his name translated means “he who has golden weapons.” IN wildlife Sea nettles are found in the Pacific Ocean from Canada to Mexico. The diameter of the jellyfish's dome can reach more than 1 meter, but more often no more than 50 cm, the length of the tentacles is 3-4 meters. The tentacles of the jellyfish are very thin, so the burn looks like a bright red welt, similar to a blow from a whip. Although victims experience severe pain and burning, going to a medical facility is usually not necessary. You can neutralize the effects of jellyfish toxins and relieve pain with vinegar or citric acid.

Portuguese man of war(lat. Physalia physalis) is a bright and very toxic representative of colonial hydroids from the order of siphonophores. Most often found in tropical and subtropical regions of the Pacific and Indian Oceans and in the North Atlantic Ocean. IN lately There has been a significant increase in the number of this species. Since 1989, physalia has appeared in the Mediterranean Sea, for the first time off the coast of Africa, then Corsica, and in 2010 it was discovered off the coast of Malta. In the period 2009-2010, cases of physalia appearing off the coasts of Ireland and Florida were recorded. Entire flotillas of Portuguese man-of-war can now be found off the coast of Guyana, Colombia, Jamaica, Venezuela, Australia and New Zealand. In fact, the Portuguese man-of-war is not a single jellyfish, since it is a whole colony of polypoid and medusoid individuals united under one “roof”. The tentacles of this unusual organism, when extended, can reach up to 50 meters in length. A Man of Portugal burn is comparable in toxicity to a poisonous snake bite. For burns, it is necessary to treat the affected area with 3-5% vinegar in order to prevent the release of poison from the stinging cells remaining in the wound. Only in rare cases do physalia burns lead to death. The Man of Portugal is especially dangerous for children, the elderly and allergy sufferers. Be extremely careful with this type of jellyfish.

Cephea cephea or the so-called "soft" jellyfish is widespread throughout the Indo-Pacific region, including the Red Sea. This large jellyfish can reach up to 50 cm in diameter.

Aurelia eared(lat. Aurelia aurita) is a scyphoid jellyfish from the order of discomedusae. Widely distributed in the coastal waters of tropical and temperate zones. In particular, the Mediterranean and Black Seas. The diameter of the aurelia dome can reach up to 40 cm. The color is pinkish-violet, the body is almost transparent. Until recently, this type of jellyfish was not considered dangerous to humans. However, there have been several recent cases of severe burns in the Gulf of Mexico. It is believed that in the waters of the Black Sea, aurelia does not pose a serious danger to humans.

Australian jellyfish or sea wasp (lat. Chironex fleckeri) from the class of box jellyfish - the most dangerous deadly animal in the world's oceans. The main habitats are the coasts of northern Australia and Indonesia. The sea wasp is one of the largest species of box jellyfish; the diameter of its dome can reach up to 20-30 cm. Its pale blue color and almost complete transparency make it especially dangerous for swimmers, since it is not easy to notice in the water. The tentacles of a jellyfish are densely covered with stinging cells containing extremely strong poison. Burns caused by box jellyfish cause severe excruciating pain and in some cases can lead to rapid death. The venom of the sea wasp simultaneously affects the heart, nervous system and skin. At the same time, the neurotoxic venom of a jellyfish acts much faster than the venom of any snake or spider. Cases have been recorded where death occurred within 4 minutes of contact. First aid for a sea wasp burn consists of immediately treating the affected area with vinegar, removing the tentacles that have stuck to the skin (remove only with protected hands or tweezers!) and immediately contacting a medical facility, as the administration of an antitoxic serum may be required. The Australian jellyfish is the most dangerous jellyfish in the world!

Ctenophores(Latin Ctenophora) are jellyfish-like organisms that live in sea waters almost all over the world. Distinctive feature of all ctenophores - a kind of “combs”, groups of fins-cilia, used by this species for swimming. The sizes of Ctenophora range from a few millimeters to 1.5 meters. Among ctenophores, there are many deep-sea species capable of bioluminescence.

Aequorea Victoria or "crystal" jellyfish - a bioluminescent jellyfish from the order of hydromedusae. Widely distributed along the North American western Pacific coast, from the Bering Sea to Southern California.

Australian spotted jellyfish(lat. Phyllorhiza punctata) belongs to the family of pelagic jellyfish. Its main habitat is south basin Pacific Ocean. The usual size of the dome of the spotted Australian jellyfish is up to 40 cm, but in the waters of the Persian and Mexican Gulfs it reaches 70 cm. The Australian jellyfish is not dangerous to humans. However, to neutralize the poison, it is worth resorting to a proven method - treating the skin with acetic or citric acid in order to prevent possible allergic reactions. Recently recorded mass reproduction Australian jellyfish, which can pose a serious threat to populations commercial fish. Feeding on eggs and fry, they pass up to 15,000 liters of water per day through their tentacles and swallow huge amounts of plankton and other marine life.

Mediterranean jellyfish Cassiopeia can reach up to 30 cm in diameter. Spends most of its time in shallow water, basking in the sun's rays.

Hairy cyanea or Lion's mane jellyfish (lat. Cyanea capillata, Cyanea arctica) is a large jellyfish from the order of disc jellyfish. The species is distributed in all northern seas of the Pacific and Atlantic oceans, living near the coast in the surface layers of water. The bell of the Arctic cyanea (a subspecies of the hairy cyanea) can reach up to 2 meters in diameter, and the length of the tentacles is up to 33 meters. Lion's mane is generally considered a moderately stinging jellyfish. The burns it inflicts are quite painful, and the toxins contained in the poison can cause a severe allergic reaction. However, the poison of this jellyfish is not fatal to humans.

Jellyfish Chrysaora Achlyos- one of the largest species of scyphoid jellyfish. The bell size is approximately 1 m in diameter, the tentacles can reach up to 6 m in length. It has the ability of a chameleon - changing color from bright red to black.

A new species of transparent jellyfish discovered in Antarctica. Its diameter is about 2.5 cm

Jellyfish aurelia is a common jellyfish that everyone who has been to the sea has seen. Aurelia jellyfish or eared jellyfish live in the Black, Baltic, Barents, Japanese, Bering and White seas. In addition, aurelia is found in tropical seas and Arctic zones.

These jellyfish swim poorly; they can only rise from the depths and sink, hovering motionless while contracting their umbrellas. After a storm, these jellyfish are found in huge numbers on the shore.

The umbrella of Aurelia has a flat shape and is 40 centimeters in diameter. The umbrella is completely transparent because it is formed from a non-cellular substance, which is almost 98% water. In this regard, the weight of the jellyfish is close to the weight of water, which makes the swimming process easier. Small but very mobile tentacles run along the edge of the umbrella. Located on the tentacles large number stinging cells.

In the middle of the bell there is a quadrangular mouth, 4 scalloped oral lobes hang from it, which also actively move. Jellyfish use stinging cells to kill prey. Jellyfish mainly feed on small crustaceans. The oral lobes contract and pull prey toward the mouth.

Aurelias are dioecious jellyfish.

Reproduction of aurelia

Aurelias are dioecious creatures. The body of males contains milky-white testes, clearly visible and shaped like half rings. Females have purple and red ovaries, which are visible through the bell. The gender of a jellyfish can be easily determined by the color of these glands.

Reproduction in Aurelia jellyfish occurs only once, after which they die. These jellyfish, unlike most of their relatives, take care of their offspring. When a jellyfish hangs in the water, its mouth lobes are lowered down, so the eggs that come out of the mouth opening fall into the gutters, move along them and penetrate into the pockets, where they are fertilized and develop. After fertilization, the egg begins to divide, first in two, then each half divides in two again, and so on. Thus, a multicellular single-layer ball is obtained. A certain number of cells are immersed inside, just like a rubber ball is squashed, this is how a two-layer embryo is obtained.

The cells of the embryo are covered on top with a large number of cilia, with the help of which the embryo swims. From this time on, the embryo transforms into a larva called a planula. The larva swims in the water for some time, and then sinks to the bottom and attaches itself to it using its anterior end. Then a mouth with a crown of tentacles breaks out on the back, upper part of the body. Thus, the planula is transformed into a polyp, which is similar in appearance to hydra.

After some time, the polyp divides using transverse constrictions. The constrictions cut into the body of the polyp, and it takes on a resemblance to a stack of plates. These discs are young jellyfish that are beginning an independent life. That is, in this way, asexual reproduction of polyps occurs; they cannot reproduce sexually. Only jellyfish can reproduce in this way.

Jellyfish food

In Japan and China, Aurelia jellyfish are used as food; in these countries, fishing for these creatures is organized. Large aurelias are used for pickling. The mouth blades of the caught jellyfish are separated, and the umbrella is thoroughly washed until the digestive canals are cleaned. Only the non-cellular substance of the umbrella can be processed. The Chinese call jellyfish meat “crystal”. Jellyfish are eaten boiled and fried with a variety of seasonings, and salted jellyfish are used in solariums.

For humans, the stinging cells of aurelia jellyfish are safe, unlike the corner jellyfish that live in Cherny and Seas of Azov. Cornerotes do not have tentacles; they grab prey with their branched mouth cavities, the edges of which are similar to root outgrowths. These outgrowths are strewn with stinging cells that contain the toxic substance rhizostomin. This substance causes severe burns to humans. Cornerots are different from eared jellyfish the presence of a border along the edge of the umbrella of bright purple or blue color. Large specimens of cornetroots reach a diameter of 50 centimeters.

Cyanea

The Barents and White Seas are home to a cold-water giant, the cyanea; the umbrella of this huge jellyfish can reach 2 meters in diameter. The central part of the umbrella is yellowish and the edges are dark red. These jellyfish shimmer with a faint greenish color. The mouth opening is surrounded by sixteen wide oral lobes, crimson-red in color. Cyaneas have long tentacles up to 20-40 meters, light pink in color. When the cyanea spreads its tentacles, the trapping network of them covers 150 square meters.

Under the bell of these jellyfishes, haddocks, cod fry and other fish calmly swim, which under this dome find shelter and food - a variety of microorganisms living on the body of the jellyfish.

If a person touches the tentacles of cyanea, he will experience pain that goes away only after 40 minutes, in addition, quite serious lesions can occur on the skin.

Equorea jellyfish

Among the jellyfish there are also luminous representatives. If a large number of jellyfish accumulate in the water, at night it seems that green or blue balls light up from time to time.

On the Pacific coast of Russia, as well as on Atlantic coast Aequorean jellyfish live in the USA. The glow of these jellyfish makes the waves seem to be on fire. And in tropical and moderately cold waters, luminous pelagia of the nightglow live.

Under the “dome” of a jellyfish, fry of various fish can live.

There is an interesting relationship between jellyfish and small fish. When immersed in water, you can see small horse mackerel swimming next to the cornet jellyfish. When divers approach the fish, they instantly hide under the dome of the jellyfish, through which their bodies can be distinguished. The fry do not touch the stinging cells located on the tentacles of jellyfish, so jellyfish for them are a reliable shelter from numerous predators. But some careless fry nevertheless become victims of stinging cells, in which case the jellyfish calmly digests them.

Jellyfish are animals that everyone associates with something formless and infinitely primitive, but their lifestyle and physiology are not as simple as it seems at first glance. The word “jellyfish” usually means animals from the Scyphoid class and representatives of the Trachylid order from the Hydroid class of the Coelenterate type. At the same time, in the scientific community this word has a broader interpretation - zoologists use this term to designate any mobile forms of coelenterates. Thus, jellyfish are closely related to mobile species of coelenterates (siphonophores, sea ships) and sessile species - corals, sea anemones, hydras. In total, there are over 200 species of jellyfish in the world.

Scyphoid jellyfish rhizostoma, or cornerot (Rhizostoma pulmo).

Because of their primitiveness, jellyfish are characterized by uniform physiology and internal structure, but at the same time they are distinguished by an amazing variety of colors and appearance, unexpected for such simple animals. One of the main distinguishing features of jellyfish is radial symmetry. This type of symmetry is characteristic of some marine animals, but in general it is not very common in the animal world. Due to radial symmetry, the number of paired organs in the body of jellyfish is always a multiple of 4.

The umbrella of this jellyfish is divided into blades, the number of which is always a multiple of 4.

Jellyfish are so primitive that their body does not have any differentiated organs, and the tissues of the body consist of only two layers: the outer (ectoderm) and the inner (endoderm), connected by an adhesive substance - mesoglea. However, the cells of these layers specialize in performing different functions. For example, ectoderm cells perform an integumentary function (analogous to skin), motor (analogous to muscles), special sensitive cells are also located here, which are the rudiments of the nervous system and special germ cells that form the reproductive organs in adult jellyfish. But endoderm cells are only involved in digesting food; for this they secrete enzymes that digest prey.

Due to the highly developed colorless mesoglea, the body of the flower cap jellyfish (Olindias formosa) looks almost transparent.

The body of jellyfish is shaped like an umbrella, disk or dome. Upper part The body (it can be called the outer) is smooth and more or less convex, and the lower (it can be called the inner) shape resembles a bag. The internal cavity of this sac is both the engine and the stomach. In the middle of the lower part of the dome, jellyfish have a mouth. Its structure is very different in different species: in some jellyfish the mouth has the shape of an elongated proboscis or tube, sometimes very long, in others there are short and wide oral lobes on the sides of the mouth, in others, instead of lobes there are short club-shaped oral tentacles.

This gorgeous crown is formed by the mouth tentacles of the cotylorhiza tuberculata jellyfish.

Along the edges of the umbrella there are hunting tentacles; in some species they can be relatively short and thick, in others they can be thin, long, and thread-like. The number of tentacles can vary from four to several hundred.

The hunting tentacles of the eared jellyfish (Aurelia aurita) are relatively short and very thin.

In some species of jellyfish, these tentacles are modified and turned into balance organs. Such organs look like a tube-stalk, at the end of which there is a bag or vesicle with a calcareous stone - a statolith. When the jellyfish changes direction of movement, the statolite moves and touches the sensitive hairs, from which the signal is transmitted to the nervous system. The nervous system of jellyfish is extremely primitive, these animals have neither a brain nor sensory organs, but there are groups of light-sensitive cells - eyes, so jellyfish distinguish between light and darkness, but, of course, they cannot see objects.

And this jellyfish has thick and long hunting tentacles combined with long and fringed mouthparts.

However, there is one group of jellyfish that completely refutes the usual ideas about these animals - these are staurojellyfish. The fact is that staurojellyfish do not move at all - they are a rare example of sessile animals. Sessile jellyfish are radically different in structure from free-swimming species; at first glance, the relationship between these groups of jellyfish seems incredible.

Benthic sessile jellyfish Cassiopea andromeda.

The body of stavromedusas resembles a bowl on a long stem. With this leg, the jellyfish attaches itself to the ground or algae. There is a mouth in the middle of the bowl, and the edges of the bowl are extended into eight so-called arms. At the end of each “arm” there is a bunch of short tentacles, similar to a dandelion.

Sedentary lucernaria jellyfish (Lucernaria bathyphila).

Despite the fact that stavromedusas lead a sedentary lifestyle, if necessary, they can move. To do this, the jellyfish bends its leg in such a way that its cup leans towards the ground, and then stands on its “hands”, as if performing a headstand, after which the leg comes off and moves a few centimeters, standing on the leg the jellyfish straightens. Such movements are carried out very slowly; the jellyfish takes several steps per day.

This alfalfa shows off the muscular stalk that attaches it to the bottom.

The sizes of jellyfish range from 1 cm to 2 m in diameter, and the length of the tentacles can reach 35 m! The weight of such giants can reach up to a ton!

This is the largest jellyfish in the world - cyanea, or lion's mane(Cyanea capillata), its long tentacles can reach 35 m in length!

Since the tissues of jellyfish are poorly differentiated, their cells are not colored. Most jellyfish have a transparent body or a pale milky, bluish, yellowish tint. This feature is reflected in English name jellyfish - “jelly fish”. Indeed, devoid of a skeleton, soft, saturated with moisture (the water content in the body of jellyfish is 98%!), the pale body of jellyfish resembles jelly.

In water, their body retains elasticity due to saturation with moisture, but a jellyfish thrown onto land instantly falls off and dries up; on land, jellyfish are not able to make even the slightest movement.

However, not all jellyfish are so inconspicuous. Among them there are truly beautiful views, painted in bright colors - red, pink, purple, yellow. Only there are no green jellyfish. In some species, the coloration has the appearance of a pattern in the form of small speckles or stripes.

Stunning play of colors of scyphoid jellyfish.

But that's not all. Some types of jellyfish (Pelagia nocturnal, Equorea, Rathkea and others) are capable of glowing in the dark. Interestingly, deep-sea jellyfish emit red light, while those that swim close to the surface of the water emit blue. This phenomenon is called bioluminescence and underlies the exciting natural phenomenon- night glow of the sea. The glow arises as a result of the breakdown of a special substance - luciferin, the name of which is similar to the name of the devil; apparently, this phenomenon caused sacred awe among the discoverers of bioluminescence. To be fair, it should be said that the glow of water is provided not only by jellyfish, but also by other marine organisms- small crustaceans (plankton), algae and even... worms.

The deep-sea atoll scyphoid jellyfish (Atolla vanhoeffeni) is bright red and looks like an unearthly creature.

The range of jellyfish covers the entire World Ocean; they are found in all seas except inland ones. Jellyfish live only in salt water; occasionally they can be found in closed lagoons and brackish lakes of coral islands, which were once separated from the sea. The only one freshwater species- a tiny jellyfish Craspedacusta, which was discovered by chance in the pool ... of the London Botanical Society. The jellyfish got into the pool along with aquatic plants brought from the Amazon. Among jellyfish you will not find pandemic species, that is, those that are found everywhere; usually each type of jellyfish occupies an area limited to one sea, ocean or bay. Among the jellyfish there are heat-loving and cold-water ones; species that prefer to stay near the surface and are deep-sea. Deep-sea jellyfish almost never rise to the surface; they spend their entire lives swimming in the depths in pitch darkness. Those jellyfish that live near the surface of the sea make vertical migrations - during the day they dive to great depths, and at night they rise to the surface. Such migrations are associated with the search for food. Jellyfish can also migrate in a horizontal direction, although they are passive in nature; jellyfish are simply transported by currents over long distances. Jellyfish, being primitive animals, do not contact each other in any way; they can be classified as solitary animals. At the same time, in places rich in food, at the intersection of currents, jellyfish can form large clusters. Sometimes the number of jellyfish increases so much that they literally fill the water space.

Numerous jellyfish make vertical migration in the slightly salty Lake Medusa on the island. Palau.

Jellyfish move rather slowly, largely using the auxiliary force of currents. The movements are ensured by thin muscle fibers in the umbrella: contracting, they seem to fold the dome of a jellyfish, while the water contained in the internal cavity (stomach) is forcefully pushed out. This creates a jet stream that pushes the jellyfish’s body forward. Accordingly, jellyfish always move in the direction opposite to the mouth, but they can swim in different directions- horizontally, up and down (as if upside down). The direction of movement and its position in space are determined by jellyfish with the help of balance organs. Interestingly, if the jellyfish's vesicles with statoliths are cut off, its umbrella contracts less often. However, the jellyfish is not destined to live long as a disabled person - these animals have excellent tissue regeneration. Due to the primitiveness of their structure, all cells in the body of jellyfish are interchangeable, so they quickly heal any wounds. Even if a jellyfish is cut into pieces or the “head” is separated from the lower body, it will restore the missing parts and form two new individuals! It is characteristic that the restoration of the head end occurs faster than the end part. What is even more surprising is that if such an operation is carried out at different stages of jellyfish development, then each time individuals of the appropriate age will be formed - from an adult jellyfish adults will be formed, from the larval stage only larvae will be formed, which will continue their development as independent organisms. Thus, the tissues of one of the most primitive animals have so-called cellular memory and “know” their age.

Jellyfish swimming upside down.

All jellyfish are predators because they feed exclusively on animal food. However, the prey of most jellyfish are tiny organisms - small crustaceans, fish fry, free-swimming fish eggs and simply small edible pieces of someone else's prey. The largest species of jellyfish can prey on small fish and... smaller jellyfish. However, the hunting of jellyfish looks peculiar. Since jellyfish are practically blind and have no other senses, they are unable to detect and pursue prey. They find their food in a passive way; they simply catch with their tentacles the edible little things that the current brings. Jellyfish catch the touch with the help of hunting tentacles and use them to kill the victim. How do primitive helpless “jelly” manage to do this? Jellyfish have powerful weapons - stinging or nettle cells in their tentacles. These cells may be different types: penetrants - cells look like pointed threads that dig into the victim’s body and inject a paralyzing substance into it; glutinants - threads with a sticky secretion that “glue” the victim to the tentacles; volvents are long sticky threads in which the victim simply becomes entangled. The paralyzed victim is pushed towards the mouth by the tentacles, and undigested food remains are also removed through the mouth. The poisonous secretion of jellyfish is so powerful that it affects not only small prey, but also animals much larger than the jellyfish themselves. Deep-sea jellyfish lure prey with a bright glow.

The victim cannot get out of this tangle of mouth and hunting tentacles of the jellyfish.

The reproduction of jellyfish is no less interesting than other life processes. In jellyfish, sexual and asexual (vegetative) reproduction is possible. Sexual reproduction includes several stages. Sex cells mature in the gonads of jellyfish regardless of the season, but in species from temperate waters, reproduction is still confined to the warm period of the year. Jellyfish are dioecious; males and females do not differ from each other in appearance. Eggs and sperm are released into the water... through the mouth, in external environment fertilization occurs, after which the larva begins to develop. Such a larva is called a planula; it is not able to feed and reproduce. Short time The planula floats in water and then settles to the bottom and attaches to the substrate. At the bottom, a polyp is formed from the planula, capable of reproducing asexually - by budding. It is characteristic that daughter organisms are formed in the upper part of the polyp, as if layering on top of each other. Ultimately, such a polyp resembles a stack of plates stacked on top of each other; the uppermost individuals gradually separate from the polyp and swim away. Free-swimming individuals of hydroid jellyfish are actually young jellyfish that gradually grow and mature; in scyphoid jellyfish, such an individual is called an ether, since it differs sharply from an adult jellyfish. After some time, the ether turns into an adult. But in the pelagic jellyfish and several species of trachylids there is no polyp stage at all; in them, mobile individuals are formed directly from the planula. Bougainvillea and Campanularia jellyfish have gone even further, in which polyps are formed directly in the gonads of adult individuals; it turns out that the jellyfish gives birth to tiny jellyfish without any intermediate stages. Thus, in the life of jellyfish, a complex alternation of generations and methods of reproduction occurs, and from each egg several individuals are formed at once. The reproduction rate of jellyfish is very high and they quickly restore their numbers even after natural disasters. The lifespan of jellyfish is short - most species live for several months, the largest species of jellyfish can live 2-3 years.

The dome of this jellyfish is decorated with stripes.

A tiny fish hides under the dome of a jellyfish.

A green turtle eats a jellyfish.

Jellyfish have been known to people since ancient times, but due to their insignificant economic value, they did not attract attention for a long time. The word medusa itself comes from the name of the ancient Greek goddess Medusa, the Gorgon, whose hair, according to legend, was a tuft of snakes. Apparently the moving tentacles of jellyfish and their poisonousness reminded the Greeks of this evil goddess. However, almost no attention was paid to jellyfish. The exceptions were countries Far East, whose inhabitants loved exotic food. For example, the Chinese eat eared jellyfish and edible rhopil. On the one hand, the nutritional value of jellyfish is negligible, since their body mainly consists of water, on the other hand, the abundance and availability of jellyfish suggested the idea of ​​deriving at least some benefit from them. To do this, the Chinese first cut out the poisonous tentacles from jellyfish, and then salt them with alum and dry them. Dried jellyfish resemble the consistency of strong jelly; they are cut into strips and used in salads, as well as boiled and fried with the addition of pepper, cinnamon and nutmeg. Despite such tricks, jellyfish are practically tasteless, so their use in cooking is limited to the national cuisines of China and Japan.

The eared jellyfish is one of the edible species.

In nature, jellyfish provide some benefit by cleaning sea waters from small organic debris. Sometimes jellyfish multiply so much that their mass clogs water settling tanks in desalination plants and pollutes beaches. However, jellyfish should not be blamed for this pestilence, since people themselves are the culprits of such outbreaks. The point is that emissions organic matter and biological debris that fills the oceans are food for jellyfish and provoke their reproduction. This process is also facilitated by a shortage of fresh water, since with an increase in the salinity of the sea, jellyfish reproduce better. Since jellyfish reproduce well, there are no endangered species among them.

Seasonal invasion of jellyfish in the Black Sea is a common occurrence.

Under natural conditions, jellyfish pose no particular benefit or harm to humans. However, the venom of some species can be dangerous. Poisonous jellyfish can be divided conditionally into two groups: in some species the poison is irritating and can cause allergies, in others the poison acts on the nervous system and can lead to serious disruption of the heart, muscles and even death. For example, the sea wasp jellyfish that lives in Australian waters has caused the death of several dozen people. Touching this jellyfish causes a severe burn; after a few minutes, convulsions begin and many people die before they can swim to the shore. However, the sea wasp has an even more terrible competitor - the Irukandji jellyfish, which lives in the Pacific Ocean. The danger of this jellyfish is that it is very small (12 cm in diameter) and stings almost painlessly, so swimmers often ignore its bite. At the same time, the poison of this baby acts very quickly. Despite this, the danger of jellyfish in general is greatly exaggerated. In order to protect yourself from unpleasant consequences, it is enough to know a few rules:

• do not touch unknown species of jellyfish - this applies not only to living jellyfish swimming in the sea, but also to dead ones washed ashore, because the stinging cells can continue to act for some time after the death of the jellyfish;
• in case of a burn, get out of the water immediately;
• rinse the bite site with plenty of water until the burning stops;
• in case discomfort did not pass, wash the bite site with a vinegar solution and call immediately ambulance(usually in such cases adrenaline injections are given).

Burns on a swimmer's arm left by a jellyfish.

Typically, a victim of a jellyfish burn recovers in 4-5 days, but one thing should be taken into account: jellyfish venom can act as an allergen, so if you encounter the same type of jellyfish again, the second burn will be much more dangerous than the first. In this case, the body’s reaction to the poison develops faster and more powerfully, and the threat to life increases many times over. Nevertheless, the mortality rate from encounters with jellyfish is insignificant and is inferior to accidents with other species of animals.

Jellyfish at the Monterey Public Aquarium.

Despite some unfriendliness of jellyfish towards humans, it has recently become fashionable to keep them in an aquarium. The smooth, continuous movements of these fantastic creatures bring peace and calm the nerves. However, keeping jellyfish in an aquarium poses some difficulties: jellyfish are very sensitive to water pollution, do not tolerate desalination, and require a less pronounced water flow. They are most often kept in large public aquariums, where it is relatively easy to keep the water clean and create a current. However, you can also keep jellyfish at home. For home keeping, the moon jellyfish and cassiopeia jellyfish are used, which reach 20 and 30 cm in diameter, respectively. Only a special one is suitable for keeping both species. marine aquarium, always with a powerful water purification system, including mechanical filtration. You need to create a current in the aquarium, but at the same time make sure that the jellyfish is not sucked into the filter by the current. Jellyfish require special lighting, so metal-halogen lamps will have to be installed in the aquarium. Please note that the water temperature for a moon jellyfish should not exceed 12-18 C°; Cassiopeia can easily live at room temperature. You need to feed jellyfish with live food - artemia, which can be easily purchased in specialized stores and from amateur aquarists. Both species are not dangerous, but can still cause painful burns, so be careful when caring for jellyfish. Do not forget that jellyfish will not tolerate proximity to fish; only motionless animals or benthic organisms can be placed in their aquarium.

Hello my dear friends! In order to maintain our erudition at the proper level and not let us relax over the summer, I propose a topic from the field of knowledge. The material will later be useful to our children in lessons about the world around them.

And today we will talk about sea jellyfish. Do you agree? Moreover, those who still have a trip to the sea ahead may be interested in combining theory with practice by getting acquainted with these amazing inhabitants water element closer.

Lesson plan:

Who is she, this unknown little animal?

Marine animals with streamlined shapes, similar in appearance to an umbrella, with many tentacles, have been living among us for a long time. The name of these sea miracles was given in the 18th century by Carl Linnaeus, who was well familiar with the Homeric legends about the mythical Gorgon Medusa.

He noticed some resemblance to the head of this evil ancient Greek maiden, whose hair was composed of many moving snakes. It is because of this similarity between the tentacles and her head that the animal received its name.

And today, those who have visited the sea more than once have probably encountered them while swimming, trying to swim around this living creature. And all because jellyfish have special stinging cells with which they “bite” painfully, mercilessly burning us, as well as their prey and the predators attacking them.

Do you know what?! Medusa with unusual name Turitopsis Nutricula is considered the only immortal creature of its kind on our planet. On average, almost all jellyfish live no longer than six months; long-livers live up to three years. Only a few species do not die, but are reborn into a new living organism.

Speaking in the language of zoologists, these marine inhabitants are none other than coelenterates, members of the group of multicellular invertebrates. That’s why they spread so shapelessly, like jelly, when they fall on a hard surface or into our hands - there’s nothing for the fabrics to hold on to!

What, what, what are our jellyfish made of?

What does a skeletonless jellyfish consist of? Yes from the water! And by 98 percent! Therefore, if you put it to bask in the sun, then almost all of it will melt and dry out. And its muscles help it move in the water.

There are tentacles at the edges of the jellyfish's body. They can be long and thin, while some have short, thick “legs”. Based on these very tentacles, zoologists divide them into species. But no matter how many “legs” this invertebrate has - four or one hundred and four - their number is always a multiple of four. Why? This is how nature arranged it - this feature in such animal representatives is called radial symmetry.

It is on these very tentacles that those unfortunate stinging cells containing burning poison are located.

Do you know what?! The jellyfish called Sea Wasp is considered the most poisonous in the world among its relatives. This invertebrate “biter” the size of a basketball has such strength that it can kill 60 people at once in a couple of minutes!

The jellyfish breathes underwater with its entire body, and looks at those around it with 24 eyes, which are light-sensitive cells. True, scientists say that these invertebrates cannot distinguish objects, but they can distinguish light from darkness.

But thanks to these special cells, many specimens glow beautifully in the dark. Those that live higher to the surface of the water can wink in red, and those that prefer to hide in the depths often warn of their presence with blue light.

Jellyfish also have a mouth. It is located in the lower part and may look like a tube for some, like a club for others, and for others it can simply be a wide hole. By the way, because the jellyfish eats, it also throws the remaining food into the water.

A jellyfish has a lot of things, but it doesn’t have a brain! Nature did not reward the primitive creature it created with the ability to think, reflect, dream, and it did not provide sense organs.

How does a jellyfish live?

Jellyfish can live exclusively in salty sea water, so you will never see them in fresh rivers and lakes. But the oceans and seas, and not necessarily warm ones, there are those that like colder water - this is theirs favorite place residence.

This creature grows throughout its unconscious life and, depending on the species, can be small, just a few millimeters, or huge, as much as two meters. Some individual specimens can weigh several centners! Such a straight Bolskhansky floating jellied meat!

Do you know what?! If we measure the size of a resident of the North-West Atlantic called Cynea (in English Cynea) along with its tentacles, we get a figure of almost 40! meters.

This creature without brains and skeleton is a real predator! The largest ones catch small fish and even eat their own relatives. Smaller specimens are content with crustaceans, fish fry and caviar. “How does a jellyfish, which cannot distinguish any outlines, look for food?” - you ask. With the help of those very terrible and dangerous stinging cells on the tentacles, which catch touches and without thinking, since they have nothing to think about, they instantly inject poison into the victim. The jellyfish thereby paralyzes the prey, and then begins to feed.

Now you understand that when you touch the body of a jellyfish while swimming, in the first seconds it sees you as another lunch or dinner, burning you with poison! Some use the tentacles as a net to catch, entangling prey in them.

Scientists have noticed that jellyfish are solitary by nature. Of course, who would be friends with such gorgons! If you see colonies of clustered umbrella caps, then they have gathered together not at all because they want to “drink tea and talk.” They were simply overwhelmed by the flow of water. So they prefer to keep their distance from each other.

What types of jellyfish are there?

As we already mentioned, they are divided into types based on their tentacles. So, these are the families they have.

In total, in the nature of the world's oceans there are more than two hundred varieties of jellyfish of all shapes and colors. There are completely transparent ones, and red ones, and purple ones, and even speckled and striped ones, but there are no green ones! Why is unclear...

In general these natural creatures amazingly beautiful, especially when you watch them from the side, slowly floating through the water. Do you have any doubts? Hurry up, go to the aquarium and admire this beauty. No nearby? Then the Internet will always help you touch the beauty from thousands of kilometers away!

That's probably enough erudition for today?! It's time to relax, because it's still summer!

Although a video about jellyfish probably wouldn’t hurt)

Have a great August!

Since ancient times, people have known strange shapeless sea animals, to which they gave the name “jellyfish” by analogy with the mythological ancient Greek goddess Medusa the Gorgon. The hair of this goddess was a moving tuft of snakes. The ancient Greeks found similarities between the evil goddess and sea jellyfish with poisonous tentacles.

The habitat of jellyfish is all the salty seas of the World Ocean. There is only one known freshwater species of these sea ​​creatures. Each species occupies a habitat limited to one body of water and will never be found in another sea or ocean. Jellyfish are either cold-water or heat-loving; deep-sea and those that stay near the surface.

However, such species swim near the surface only at night, and during the day they dive into the depths in search of food. The horizontal movement of jellyfish is passive in nature - they are simply carried by the current, sometimes over long distances. Due to their primitiveness, jellyfish do not contact each other in any way; they are solitary animals. Large concentrations of jellyfish are explained by the fact that the current brings them to places rich in food.

Due to the highly developed colorless mesoglea, the body of the “flower cap” jellyfish (Olindias formosa) looks almost transparent

Types of jellyfish

More than 200 species of jellyfish are known in nature. Despite the primitiveness of the structure, they are very diverse. Their sizes range from 1 to 200 cm in diameter. The largest jellyfish is the lion's mane (cyanea). Some of its specimens can weigh up to 1 ton and have tentacles up to 35 m long.

Jellyfish are shaped like a disk, an umbrella, or a dome. Most jellyfish have a transparent body, sometimes with bluish, milky, or yellowish tints. But not all species are so inconspicuous; among them there are truly beautiful, bright colors: red, pink, yellow, purple, speckled and striped. There are no green jellyfish in nature.

Species such as Equorea, Pelagia nocturna, and Rathkea can glow in the dark, causing a phenomenon called bioluminescence. Deep-sea jellyfish emit red light, while those floating near the surface emit blue light. There is a special type of jellyfish (staurojellyfish) that hardly move. They are attached to the ground with a long leg.

The structure of jellyfish

The internal structure and physiology of jellyfish are uniform and primitive. They have one main hallmark– radial symmetry of organs, the number of which is always a multiple of 4. For example, a jellyfish umbrella can have 8 blades. The body of a jellyfish does not have a skeleton; it consists of 98% water. When thrown ashore, the jellyfish is unable to move and dries up instantly. Its consistency is similar to jelly, which is why the British called it “jelly fish.”

Body tissues have only two layers, which are connected to each other by an adhesive substance and perform different functions. The cells of the outer layer (ectoderm) are “responsible” for movement, reproduction, and are analogues of skin and nerve endings. The cells of the inner layer (endoderm) only digest food.

The outer part of the body of jellyfish is smooth, mostly convex, the inner (lower) shape resembles a bag. The mouth is located at the bottom of the dome. It is located in the middle and is very different in structure among different types of jellyfish. The umbrella is surrounded by hunting tentacles, which, depending on the species, can be either thick and short or thin, thread-like, and long.

What do jellyfish eat?

Jellyfish are predators; they consume only animal food (crustaceans, fry, small fish, caviar). They are blind and have no senses. Jellyfish hunt passively, catching with their tentacles the edibles that the current brings. The hunting tentacles kill the prey. This is done in different ways.

This is the largest jellyfish in the world - the cyanea, or lion's mane (Cyanea capillata), its long tentacles can reach 35 m in length!

Some types of jellyfish inject poison into the prey, others glue the prey to the tentacles, and others have sticky threads in which it becomes entangled. The tentacles push the paralyzed victim towards the mouth, through which undigested remains are then expelled. Interestingly, jellyfish living in the depths attract prey with their bright glow.

How do jellyfish reproduce?

Jellyfish have vegetative (asexual) and sexual reproduction. Externally, males are no different from females. Sperm and eggs are released through the mouth into the water, where fertilization occurs. After this, the larva (planula) develops. The larvae are not able to feed, they settle to the bottom and a polyp is formed from them. This polyp can reproduce by budding. Gradually, the upper parts of the polyp separate and float away; these are actually young jellyfish that will grow and develop.

Some species of jellyfish do not have a polyp stage. Young individuals are immediately formed from the planula. There are also species in which polyps are formed in the gonads, from which small jellyfish are born. Each egg cell in jellyfish produces several individuals.

Vitality of jellyfish

Although jellyfish do not live long - from several months to 2-3 years, their numbers are restored very quickly even after various disasters. Their reproduction rate is very high. Jellyfish quickly restore lost body parts. Even if they are cut in half, two new individuals are formed from the halves.

It is interesting that if such an operation is carried out at different ages of the jellyfish, then an individual of the corresponding developmental stage grows from the tissues. If you divide the larva, then two larvae will grow, and from the adult parts - jellyfish of the appropriate age.

Jellyfish swimming upside down

Jellyfish and people

Some types of jellyfish pose a danger to humans. They can be roughly divided into two groups. Some cause allergies, while the venom of others affects the nervous system and can cause serious problems in the functioning of the muscles and heart, and in some cases, death.

To avoid putting yourself in danger, you should avoid touching jellyfish, both living and dead. In case of a burn, you should wash the injured area with water, or better yet, a vinegar solution. If the pain does not subside and there are complications, you should immediately call a doctor.