Jellyfish (Polypomedusae) is a representative of marine fauna. The class of jellyfish, which includes freshwater hydras, consists of many sea inhabitants, some of them very large and conspicuous.

The jellyfish has a gelatinous and sometimes almost cartilaginous body in the shape of a rain or lady's umbrella with a stem extending downwards or a bell with a tongue hanging down.

In a jellyfish umbrella, you can distinguish a convex outer or upper side and a concave inner or lower side. From the center of the lower surface of the jellyfish's umbrella, either a very short or rather long stalk extends downwards, representing an oral tube; on the lower edge of this tube there are projections of various sizes located around the mouth opening, which are called oral lobes or oral tentacles.

The edge of the umbrella, equipped on its lower surface with a layer of muscles that serves to reduce the cavity of the bell and at the same time for the movement of the jellyfish, appears either dissected into separate blades, or has the form of a border running in the form of a ring perpendicular to the oral tube. Along the edge of the bell there are usually tentacles or lassoes, the number of which varies greatly; visual, auditory, and sometimes olfactory organs are also located right there.

The stomach of the jellyfish, communicating through the pharyngeal tube with the mouth, passes into a whole series of radiant canals or elongated pockets leading to the edge of the bell. Eggs and seminal cells develop in the stomach or on the walls of the canals extending from it.

The life cycle of a jellyfish includes the formation of a polyp, then a jellyfish, then a polyp again, and so on. As for the polyp, it differs from the jellyfish in the absence of a bell. Each polyp appears as a sac-like body, closed at one end; the closed lower end of such an individual is attached to some foreign object or to a polypnik, which sometimes floats freely or is attached to something.

The opposite end of the polyp is usually elongated in the form of a cone and in the center has an opening called the mouth, surrounded by tentacles. If we imagine that such a polyp, having separated from the object to which it was attached, will somewhat flatten in the dorso-ventral direction, then we will get a disk with tentacles along the edges and a mouth cone in the middle; from here it is not far to a real jellyfish: all that remains is for this disk to become convex and take the shape of a bell or an umbrella.

Thus, the oral canal of the polyp turns into the pharyngeal tube of the jellyfish, and the edge of its oral disc, bordered by tentacles, into the edge of the bell of the jellyfish with its tentacles.

As for the bag-shaped stomach of the polyp, it turns into the vascular system of a jellyfish in water in the following way: its close walls grow together along the periphery over some distance, resulting in radially located channels. However, polyps differ from jellyfish not only in their structure, but also in other features, the most important of which is their different participation in the reproduction process.

How does a jellyfish reproduce?

Jellyfish are organisms that develop reproductive products; polyps, which are one of the stages of development of jellyfish, the stage of the so-called nurse (since they give rise to the jellyfish themselves), reproduce asexually.

The polyps themselves develop from fertilized jellyfish eggs and are in turn produced asexually by jellyfish. There are, however, jellyfish from whose eggs only jellyfish develop; Polyps are also known that produce eggs and seed cells instead of jellyfish. Between these two extreme cases there are all sorts of transitions. With asexual reproduction, the vast majority of polyps form entire colonies, composed of individual individuals that remain connected to each other; the formation of such colonies is common for the order of hydroid polyps and hydroid jellyfish (Hydroidea). All of the main characteristics of hydroid polyps indicated are also characteristic of freshwater polyps, i.e. hydras.

The sexual generation of hydroid polyps are usually hydroid jellyfish, which are characterized by the presence of a membranous rim, the so-called sail, along the edge of the bell.

Hydroid jellyfish and polyps

Freshwater polyps are among the types of hydroid polyps that do not have alternation of generations, i.e., do not develop jellyfish. These same hydroid polyps include the so-called Sarsia, named after a Swedish naturalist; The reproduction of species of this genus is associated with alternation of generations.

The tubular sarsia itself (S. tubulosa) has the appearance of slender and weakly branched bushes, 10-15 mm high; Its polyps, club-shaped, are covered with 12-16 tentacles scattered without any order. She lives in the Baltic Sea and settles on the underwater parts of wooden buildings, on sea grass, red algae and similar objects.

The club-shaped polyps of Sarsia bud, after a number of changes occurring in them, jellyfish, which are the sexual generation; These jellyfish, reaching 6-8 mm in width, are bell-shaped, equipped with a long oral tube and four long tentacles located along the edge of the bell at an equal distance from one another; At the base of each tentacle a simple eye is placed.

Adjacent to the order of hydroid polyps and hydroid jellyfish just described is the order of floating siphonophores, or tubular polyps (Siphonophora), free-floating colonies, some members of which are in the form of polyps, others in the form of jellyfish; in such colonies there are, in addition, feeding polyps armed with a long thread - a lasso, jellyfish-like individuals that produce egg cells and sperm, and, finally, some members of the colony turn into apparatus or bells that serve for the movement of the colony.

The flat siphonophores include the so-called swallowtail (Velella); this animal, swimming on the sea surface, has a disk-shaped body, pierced inside with air channels, with a crest standing vertically on its upper surface, which plays the role of a sail: on the lower side of the disk in the center there is one large feeding polyp, surrounded by many smaller ones; The tactile members of the colony are located along the edges of the disk.

The most famous species of this genus is the common sailfish (Velella spirans), which can often be found very far from the shores, from which it is driven by the wind; in this animal, at the base of small polyps, small jellyfish-like creatures bud, which already develop sexual products and thus serve for the reproduction of the sailfish.

Another form, Physalia, has most of its body in a huge air sac lying horizontally on the water surface; on the lower surface of the bladder there are large and small feeding polyps, armed with long lassoes; the palps are also located here.

The common bladderwort (Ph. caravella), with violet, white-speckled polyps and a purplish-red air sac, playing the same role as the swallowtail scallop, is distributed in the Mediterranean Sea and the Atlantic Ocean; the dimensions of this form reach 30 cm in length (not counting the lassoes, which can extend very significantly).

Classification

Akalephs

Representatives of the next order, Acalephae, differ from hydropolyps, hydromedusae and siphonophores, which are similar in structure to the polypoid and medusoid individuals of the entire colony, in the structure of both polyps and jellyfish: jellyfish of this order mostly reach quite significant sizes and have an umbrella, dissected at the edges into separate lobes.

As for polyps, their characteristic feature is the presence of four regularly located longitudinal swellings located on the inner wall of their gastric cavity; in the intervals between the indicated swellings there are 4 bags.

Reproduction of Akalephs

In some cases, the egg of a jellyfish develops directly into a jellyfish, but for the most part it turns into a small goblet-shaped polyp with tentacles around the oral disc; on such an embryo, sitting motionless on algae, etc., horizontal ring-shaped constrictions begin to appear, located one below the other; in this form, the entire embryo resembles a stack of plates; soon individual discs - future jellyfish - bud off one after another and, floating freely, turn into sexually mature forms.

The long-eared jellyfish Aurelia aurita, which is very common in the Baltic and generally in the European seas, belongs to the suborder of broad-tentacled acalefs (Semostomae), characterized by the presence of 4 long, boat-shaped simple tentacles located around a cruciform mouth; it is distinguished by a flat, like a watch glass, and sometimes hemispherical umbrella and narrow, lanceolate, strongly laminated at the edges, but not lobed tentacles.

This form, often found in huge masses, is well known to all explorers of our seas; The size of the eared jellyfish varies between 1 and 40 cm in diameter, but specimens measuring 5-10 cm are most often found.

Another well-known jellyfish from the Acalephids is the hairy jellyfish (Cyanea capillata), native to northern European seas. Like other species of this genus, the described jellyfish is distinguished by the edge of the bell, dissected into 8 main lobes, and the presence on its lower surface of many long tentacles - lassoes.

The described jellyfish appears in the fall, like the eared jellyfish, in masses; its main color is yellow-brown, sometimes reddish-yellow; in diameter reaches 30-60 cm, but there are specimens more than 1 m in diameter and with tentacles more than 2 m in length.

The northern hairy jellyfish (C. arctica) reaches even larger sizes, that is, over 2 m in diameter; the length of the tentacles of this species sometimes exceeds 4 m. This jellyfish is thus the largest of all jellyfish known to us.

Rootmouth jellyfish

As for the root-mouthed jellyfish (Rhizostomeae), they differ from the previous ones in the presence of 8 long, arranged in pairs, root-shaped mouth tentacles; In most cases, these tentacles grow together in pairs, and the mouth is completely closed and its role is played by many small sucking holes located along the tentacles.

Between the indicated stomata, these jellyfish often have more or less numerous oral palps, with button-shaped thickenings at the ends.

Cotylorhiza

An example of such a jellyfish is the Mediterranean cotylorhiza tuberculata; it is a generally yellowish jellyfish, 10-20 cm wide in diameter with long sucking tubes or with suckers on long legs; the edges of the disk of this jellyfish are mottled with white spots, the oral disk is fleshy red or yellowish-brown in color; milky-white tentacles, which, however, can sometimes be amber-yellow in color, brown, purple or violet blue, festoons surrounding the sucking holes - these are the features that describe the described jellyfish in more detail.

Disc jellyfish

Both mentioned groups of jellyfish, broad-tentacled and root-mouthed, constitute the suborder of disc-shaped jellyfish (Discomedusae), the characteristic features of which are: a flat, mostly disc-shaped bell or umbrella, usually with 8 marginal sense organs; the edge of the bell is cut into no less than 16 blades; the stomach is surrounded by 8, 16, 32, or even a large number of gastric sacs; On the lower wall of the stomach there are gonads, which are very clearly visible in our eared jellyfish and are popularly called eyes.

Cuboid jellyfish

The next group of cuboid jellyfish (Cubomedusae) is defined by the following characteristics: a tall, cubic umbrella, the edge of which, reminiscent of the swimming edge of hydroid jellyfish, is in the form of a horizontally tense membrane or hanging downwards; on this edge there are 4 sensitive flasks, with an eye and an organ of hearing on each.

A representative of this group can be the Mediterranean common box jellyfish (Charybdea marsupialis), which is 2-3 cm wide and 3-4 cm high; this species, as well as other species of the same genus, is interesting for its unusually highly differentiated eyes, the structure of which resembles the structure of the eyes of vertebrates.

Sea wasp jellyfish

The sea wasp jellyfish is the most poisonous jellyfish in the world; it lives off the coast of Thailand and Australia. Its body is glassy and cube-shaped, that is, this jellyfish belongs to the cuboid jellyfish. Its stinging cells leave fatal burns. As a result, death can occur within 3 minutes.

However, there are survivors - people with strong hearts. There is an antidote against sea wasp jellyfish burns, but you must have it with you, since the victim has no more than 3 minutes from the moment of the burn to save a life. Therefore, you should swim only in places specially fenced off from jellyfish; if you decide to swim in the open ocean, then have an antidote with you.

Goblet jellyfish

Finally, the last group of goblet jellyfish (Stauromedusae) is characterized by the presence at the top of the goblet-shaped umbrella of a stalk, with the help of which the jellyfish is attached to algae, etc.; The tentacles, collected mostly in bunches, sit along the edge of the bell of these jellyfish.

Lantern

The described suborder includes, among other things, the lanternfly (Lucernaria), which belongs mainly to the northern seas; this form can move from place to place with the help of its tentacles, which is also helped by the jellyfish leg, which has the ability to arbitrarily attach or separate from underwater objects.

In the northern European, as well as in the Black and Baltic seas, the largest (up to 7 cm) and long-known species of the described genus is found - the common lanternfly (L. quadricornis): this gray, green, brown-yellow or, finally, , the black-brown jellyfish willingly settles on red algae. It is also known on the shores of Greenland and found in America, off its northeastern shores.
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Jellyfish can rightfully be called one of the most mysterious inhabitants of the depths of the sea, causing interest and a certain fear. Who are they, where did they come from, what varieties are there in the world, what is their life cycle, are they as dangerous as popular rumor says - I want to know about all this for sure.

Jellyfish appeared more than 650 million years ago, making them one of the oldest organisms on Earth.

About 95% of the jellyfish's body is water, which is also their habitat. Most jellyfish live in salt water, although there are species that prefer fresh water. Jellyfish are the “sea jelly” phase of the life cycle of members of the genus Medusozoa, alternating with the stationary asexual phase of nonmotile polyps, from which they are formed by budding after maturation.

The name was introduced in the 18th century by Carl Linnaeus, who saw in these strange organisms a certain resemblance to the mythical Gorgon Medusa, due to the presence of tentacles that flutter like hair. With their help, the jellyfish catches small organisms that serve as food for it. The tentacles may look like long or short, pointed threads, but they are all equipped with stinging cells that stun prey and make hunting easier.

Life cycle of scyphoids: 1-11 - asexual generation (polyp); 11-14 - sexual generation (jellyfish).

Glowing jellyfish

Anyone who has seen how sea water glows on a dark night will hardly be able to forget this sight: myriads of lights illuminate the depths of the sea, shimmering like diamonds. The reason for this amazing phenomenon is the smallest planktonic organisms, including jellyfish. The phosphoric jellyfish is considered one of the most beautiful. It is not found very often, living in the benthic zone near the coasts of Japan, Brazil, and Argentina.

The diameter of the luminous jellyfish umbrella can reach 15 centimeters. Living in the dark depths, jellyfish are forced to adapt to conditions, provide themselves with food, so as not to disappear altogether as a species. An interesting fact is that the bodies of jellyfish do not have muscle fibers and cannot resist water flows.

Since the slow jellyfish, swimming at the will of the current, cannot keep up with mobile crustaceans, small fish or other planktonic inhabitants, they have to use a trick and force them to swim up to the predatory mouth opening. And the best bait in the darkness of the bottom space is light.

The body of a luminous jellyfish contains a pigment - luciferin, which is oxidized under the influence of a special enzyme - luciferase. The bright light attracts victims like moths to a candle flame.

Some species of luminous jellyfish, such as Rathkea, Equorea, Pelagia, live at the surface of the water, and, gathering in large quantities, they literally make the sea burn. The amazing ability to emit light has interested scientists. Phosphors have been successfully isolated from the genome of jellyfish and introduced into the genomes of other animals. The results turned out to be quite unusual: for example, mice whose genotype was changed in this way began to grow green hairs.

Poisonous jellyfish - Sea Wasp

Today, more than three thousand jellyfish are known, and many of them are far from harmless to humans. All types of jellyfish have stinging cells “charged” with poison. They help to paralyze the victim and deal with him without any problems. Without exaggeration, for divers, swimmers, and fishermen, a jellyfish called the Sea Wasp is represented. The main habitat of such jellyfish is warm tropical waters, there are especially many of them off the coast of Australia and Oceania.

Transparent bodies of pale blue color are invisible in the warm water of quiet sandy bays. The small size, namely, up to forty centimeters in diameter, also does not attract much attention. Meanwhile, the poison of one individual is enough to send about fifty people to heaven. Unlike their phosphorescent counterparts, sea wasps can change direction of movement, easily finding careless swimmers. The poison that enters the victim’s body causes paralysis of smooth muscles, including the respiratory tract. Being in shallow water, a person has a small chance of being saved, but even if medical assistance was provided in a timely manner and the person did not die from suffocation, deep ulcers form at the sites of the “bites”, causing severe pain and not healing for many days.

Dangerous little ones - Irukandji jellyfish

Tiny Irukandji jellyfish, described by Australian Jack Barnes in 1964, have a similar effect on the human body, with the only difference being that the degree of damage is not so deep. He, as a true scientist who stands up for science, experienced the effect of poison not only on himself, but also on his own son. Symptoms of poisoning - severe headache and muscle pain, cramps, nausea, drowsiness, loss of consciousness - are not fatal in themselves, but the main risk is a sharp increase in blood pressure in a person who has personally met Irukandji. If the victim has problems with the cardiovascular system, then the likelihood of death is quite high. The size of this baby is about 4 centimeters in diameter, but its thin spindle-shaped tentacles reach 30-35 centimeters in length.

Bright beauty - Physalia jellyfish

Another very dangerous inhabitant of tropical waters for humans is Physalia - the Sea Boat. Her umbrella is painted in bright colors: blue, violet, purple and floats on the surface of the water, so it is visible from afar. Entire colonies of attractive sea “flowers” ​​attract gullible tourists, beckoning them to pick them up as quickly as possible. This is where the main danger lurks: long, up to several meters, tentacles, equipped with a huge number of stinging cells, are hidden under the water. The poison acts very quickly, causing severe burns, paralysis and disruption of the cardiovascular, respiratory and central nervous systems. If the meeting took place at great depth or simply far from the shore, then its outcome could be the saddest.

Giant Jellyfish Nomura - Lion's Mane

The real giant is Nomura Bell, who is also called Lion's Mane for some resemblance to the king of beasts. The diameter of the dome can reach two meters, and the weight of such a “baby” reaches two hundred kilos. It lives in the Far East, in the coastal waters of Japan, off the coast of Korea and China.

A huge hairy ball, falling into fishing nets, damages them, causing damage to fishermen and striking them themselves when they try to free themselves. Even if their venom is not fatal to humans, meetings with the “Lion’s Mane” rarely take place in a friendly atmosphere.

Hairy Cyanea - the largest jellyfish in the ocean

Cyanea is considered one of the largest jellyfish. Living in cold waters, it reaches its largest size. The most gigantic specimen was discovered and described by scientists at the end of the 19th century in North America: its dome was 230 centimeters in diameter, and the length of the tentacles turned out to be 36.5 meters. There are a lot of tentacles, they are collected in eight groups, each of which has from 60 to 150 pieces. It is characteristic that the dome of the jellyfish is divided into eight segments, representing a kind of octagonal star. Fortunately, they do not live in the Azov and Black Seas, so you don’t have to worry about them when going to the sea to relax.

Depending on the size, the color also changes: large specimens are bright purple or violet, smaller ones are orange, pink or beige. Cyaneas live in surface waters, rarely descending into the depths. The poison is not dangerous to humans, causing only an unpleasant burning sensation and blisters on the skin.

Using jellyfish in cooking

The number of jellyfish living in the seas and oceans of the globe is truly enormous, and not a single species is in danger of extinction. Their use is limited by their harvest, but people have long used the beneficial properties of jellyfish for medicinal purposes and enjoy their taste in cooking. In Japan, Korea, China, Indonesia, Malaysia and other countries, jellyfish have long been eaten, calling them “crystal meat”. Its benefits are due to the high content of protein, albumin, vitamins and amino acids, and microelements. And when properly prepared, it has a very refined taste.

Jellyfish “meat” is added to salads and desserts, sushi and rolls, soups and main courses. In a world where population growth is steadily threatening the onset of famine, especially in underdeveloped countries, protein from jellyfish can be a good help in solving this issue.

Jellyfish in medicine

The use of jellyfish for the manufacture of medicines is typical, to a greater extent, in those countries where their use as food has long ceased to be a subject of surprise. For the most part, these are countries located in the coastal areas, where jellyfish are directly harvested.

In medicine, preparations containing processed jellyfish bodies are used to treat infertility, obesity, baldness and gray hair. The poison extracted from stinging cells helps to cope with diseases of the ENT organs and normalize blood pressure.

Modern scientists are struggling to find a drug that can defeat cancerous tumors, not excluding the possibility that jellyfish will also help in this difficult fight.

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

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

The most numerous predators

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

Pretty simple creatures

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

Gelatinous form of being

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

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

Does a jellyfish eat crabs?

Jellyfish muscles

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

Brain and nerves of a jellyfish

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

Jellyfish are constantly eating

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

Jellyfish escape

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

There will be more sprat because of jellyfish

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

Reasons for the increase in the number of jellyfish

In overfishing of commercial fish species - the main destroyers of jellyfish. Jellyfish's main enemies include tuna, sea turtles, ocean sunfish and some ocean birds. Salmon also does not disdain jellyfish.

Abundance of jellyfish

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

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

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

Fleeing from enemies, the jellyfish throws away its tentacles

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

Arctic giant jellyfish Cyanea

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

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

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

Australian sea wasp Chironex fleckeri

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

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

Giant jellyfish stygiomedusa gigantea

Jellyfish sting

Killer Jellyfish Carukia barnesi, which has a deadly sting, is actually tiny - the length of its dome is only 12 millimeters. However, it is this animal that is responsible for the occurrence of Irukandji syndrome, which killed two tourists in Australia in 2002. It all starts with a mosquito-like bite. Within an hour, victims experience severe pain in the lower back, shooting 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 the jellyfish Carukia barnesi, which has a deadly sting, in captivity. The captured jellyfish has passed the planktonic stage and is now kept in an aquarium. Getting jellyfish to breed in captivity was the first step in developing an antivenom. In general, it will be necessary to study from 10 thousand to a million jellyfish.

Giant jellyfish of Japan Stomolophus nomurai

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

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

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

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

Jellyfish gene in potato gene

As a result of 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 if there is a lack of water in the soil, potatoes with this gene will also retain water. In addition, thanks to this gene, the jellyfish glows. And this property is preserved in potatoes: when there is a lack of water, its leaves glow green in infrared rays.

Sea feathers Pennatularia

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

Sea anemone Actiniaria

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

Sea anemone and clown fish

Hydra is a "stray stomach" equipped with tentacles

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

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

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

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

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

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

Hermaphrodites

Among those that are actually able to change sex at will are sea slugs, earthworms and the European giant garden worm.

Female worms simply inhale the small male

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

Boys eat girls

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

The worm's blood is red, but different

All mammals have red blood due to the hemoglobin contained in red blood cells. There are no red blood cells in the blood of invertebrate animals. However, their blood can still be red (for example, in an annelid, 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 chlorocruonine, which is similar to hemoglobin. This pigment is not enclosed in blood cells, but forms large molecules dissolved directly in the plasma.

Canned worms for moles

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

Earthworms from Europe pose a threat to North America

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

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

The presence of earthworms in the soil in Chippewa National Park has led to declines in populations of native insect species, small insectivorous mammals such as the mouse vole and shrew, ground-nesting bird species (such as the ovenbird), and ultimately a decline in areas occupied by sugar maple, a local forest-forming species.

Earthworms love buckthorn and can't stand oak trees.

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

Worms can live up to 500 years

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

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

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

Males for asexual worms

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

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

Best time for worms

Earthworms belong to the class Oligochaetes Annelida. 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 at the girdle region (an extension near the anterior edge).

16 tons of soil

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

Worms are garbage eaters

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

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

Worms on a hook feel no pain

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

Record for carrying heavy loads

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

Four-toed worm

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

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

One of the most ancient living organisms found on our planet are jellyfish. They are present in almost any large body of salt water, so they can be found in almost all seas and oceans. What are the jellyfish of the Black Sea?

What are jellyfish?

As scientists say, jellyfish have existed on the planet for a very long time. They appeared before man arose. And during all this time their way of life has not changed. Even the appearance remained the same. Interestingly, the body of jellyfish consists almost entirely of water. To be more precise, 98% is water. Due to their appearance, some call them “water umbrellas,” while others consider them “floating bells.”

Due to their shape, these marine inhabitants can move very quickly in the water. Their muscles, which are hydrated connective tissue, begin to contract, facilitating movement. There are several thousand different types of jellyfish in the world. As for the Black Sea, there are only three species of such marine inhabitants. And every vacationer on the Black Sea coast immediately has a question: how dangerous are they, do they pose a threat, if not to a person’s life, then to his health?

Jellyfish of the Black Sea: what is their danger to humans?

Any diver should take into account that in the Black Sea there are several inhabitants that are undesirable to meet:

- jellyfish.

Although they do not pose a mortal danger, you should still beware of them. Why is a jellyfish dangerous, and what kind of troubles can you expect from it?

If we take into account all three species of jellyfish that live here, their main weapon is their stinging cells. They contain a special toxin. When it gets on human skin, it can cause a burn, somewhat comparable to nettle. So, after meeting a jellyfish, although you won’t end up in a hospital bed, you will still have unpleasant memories. Parents especially need to monitor their children. After all, jellyfish are often washed ashore by waves. And children have more sensitive skin than adults.

Types of jellyfish of the Black Sea

You need to know that the largest number of jellyfish on the Black Sea coast occurs in the second half of summer. There are three varieties of them here, and each type has its own distinctive characteristics. The description should start with the jellyfish, which is most often found here.

1. Cornerot, which is called the Blue Jellyfish (Rhizostoma pulmo) for its appearance. It is believed that this is the most popular inhabitant of this sea. This is a marine predator that feeds not only on worms, but also on small fish. First, he paralyzes them with his poison, and then calmly eats them. The jellyfish consists of an upper cap, reaching up to half a meter in size, as well as lower fleshy outgrowths. They act as the oral cavity. This is the most poisonous type of jellyfish that lives in the Black Sea. They can sting so much that a swelling appears on the skin, as if from a thermal burn.

Cornermouth jellyfish
Photo: https://destepti.ro

2. Aurelia aurita, which poses virtually no danger. Unless you try what this jellyfish tastes like. The skin will not feel contact with it, but a slight burning sensation and redness will appear on the mucous membrane. Most of these jellyfish appear just at the height of the swimming season. The diameter of their dome can reach up to 40 cm.

Medusa-Aurelia. Photo: http://fr.academic.ru

3. Mnemiopsis (Mnemiopsis leidyi) has absolutely no stingers or even tentacles. In fact, this jellyfish appeared here from afar - from the shores of America. But it took root here and is now considered a semi-indigenous inhabitant of the Black Sea. This jellyfish is completely harmless to humans. Today, everything is being done to reduce its population.

Scientists do not give a definite answer to the question of how long jellyfish live. Many agree that the life cycle of these animals is short and the life expectancy of most species is from two to six months.

Recently, zoologists discovered that among representatives of this species there are specimens that never die and are always reborn. That is why the Turitopsis Nutricula jellyfish is considered to be the only immortal creature on the planet.

Who are jellyfish

When zoologists talk about jellyfish, they usually mean all mobile forms of coelenterate cnidarians (a group of multicellular invertebrate representatives of the animal world) that catch and kill their victims with the help of tentacles.

These amazing animals live only in salt water, and therefore they can be found in all oceans and seas of our planet (except internal ones), sometimes in closed lagoons or lakes with salt water on coral islands. Among the representatives of this class there are both heat-loving animals and those that prefer cold waters, species that live only near the surface of the water, and those that live only on the bottom of the ocean.

Jellyfish are solitary animals, since they do not communicate with each other in any way, even if currents bring them together, thus forming a colony.

These creatures received their modern name in the middle of the 18th century thanks to Karl Lineus, who hinted at the mythical head of the Gorgon Medusa, the resemblance to which he noticed in these representatives of the animal world. This name is not without reason, since these animals are similar to it.

This amazing animal consists of 98% water, and therefore has a transparent body with a slight tint, which in appearance resembles a jelly-like bell, umbrella or disk that moves by contracting the muscles of the bell wall.

Along the edges of the body there are tentacles, the appearance of which directly depends on what species it belongs to: in some they are short and thick, in others they are long and thin. Their number can vary from four to several hundred (but always a multiple of four, since representatives of this class of animals are characterized by radial symmetry).

These tentacles consist of string cells that contain poison and are therefore directly intended for hunting. It is interesting that even after death, jellyfish are able to sting for another fortnight. Some species can be deadly even to humans. For example, the animal known as the “Sea Wasp” is considered the most dangerous poisonous animal in the world’s oceans: scientists claim that its poison is enough to poison sixty people in a few minutes.

The outer part of the body is smooth and convex, while the lower part resembles a bag. In the center of the lower part there is a mouth: in some jellyfish it looks like a tube, in others it is short and wide, in others it resembles short clubs. This hole also serves to remove food debris.

These animals grow throughout their lives, and their size largely depends on the species: among them there are very small ones, no more than a few millimeters, and there are also huge ones, the body size of which exceeds two meters, and together with the tentacles - all thirty ( for example, the largest jellyfish in the world's oceans, Cyanea, which lives in the North-West Atlantic, has a body size of more than 2 m, and with tentacles - almost forty).

Despite the fact that these marine animals lack brains and sensory organs, they have light-sensitive cells that act as eyes, thanks to which these organisms are able to distinguish darkness from light (they, however, are not able to see objects). Interestingly, some specimens glow in the dark, with species living at great depths having a red light, and those living closer to the surface having a blue light.

Since these animals are primitive organisms, they consist of only two layers, connected thanks to a special adhesive substance - mesoglia:

• external (ectoderm) - a kind of analogue of skin and muscles. The rudiments of the nervous system and germ cells are also located here;
• internal (endoderm) - performs only one function: digests food.

Methods of transportation

Since all representatives of this class (even the largest individuals, whose weight exceeds several centners) are almost unable to resist sea currents, scientists consider jellyfish as representatives of plankton.

Most species still do not completely succumb to water flows and, although slowly, move, using the current and the thin muscle fibers of their body: contracting, they fold the body of the jellyfish like an umbrella - and the water that is in the lower part of the animal is sharply pushed out.

As a result, a strong jet is formed, pushing the animal forward. Therefore, these sea creatures always move in the direction opposite to the mouth. They are helped to determine where exactly they need to move by the balance organs located on the tentacles.

Regeneration

Another interesting feature of these creatures is their ability to restore lost body parts - absolutely all the cells of these animals are interchangeable: even if this animal is divided into parts, it will restore them, forming two new individuals! If you do this with an adult jellyfish, an adult copy will appear; from a jellyfish larva, a larva will appear.

Reproduction

Looking at these amazing translucent creatures, many ask themselves the question of how jellyfish reproduce. Reproduction of jellyfish is an interesting and unusual process.

Answering the question of how jellyfish reproduce, it is worth noting that in this case, both sexual (they are heterosexual) and vegetative reproduction are possible. The first involves several stages:

1. In these animals, the sex cells mature in the gonads;
2. After the eggs and sperm mature, they come out through the mouth and are fertilized, resulting in the appearance of a jellyfish larva - a planula;
3. After some time, the planula settles to the bottom and attaches itself to something, after which a polyp appears on the basis of the planula, which reproduces by budding: on it, layering on top of each other, daughter organisms are formed;
4. After some time, they peel off and float away, revealing themselves as a newly born jellyfish.
   The reproduction of some species differs somewhat from this pattern. For example, the pelagic jellyfish does not have a polyp stage at all - the cubs appear directly from the larva. But bougainvillea jellyfish can be said to be born, since polyps are formed directly in the gonads, without separating from the adults, without any intermediate stages.

Nutrition

These amazing animals are the most numerous predators on our planet. They feed mainly on plankton: fry, small crustaceans, and fish eggs. Larger specimens often catch small fish and smaller relatives.

Thus, jellyfish see almost nothing and do not have any sense organs; they hunt with the help of scratching tentacles, which, having sensed the touch of edible food on them, instantly inject poison into it, which paralyzes the victim, after which the jellyfish eats it. There are two more options for catching food (much depends on the type of jellyfish): the first is that the prey sticks to the tentacles, the second is that it gets entangled in them.

Classification

There are the following types of jellyfish, differing from each other in structure.

Hydromedusa

Hydroid jellyfish are transparent, small in size (from 1 mm to 3 cm), four tentacles and a long tube-shaped mouth are attached to the body. Among the prominent representatives of hydromedusas is the jellyfish Turritopsis nutricula: the only creature discovered by people about which scientists have declared that it is immortal.

Having reached maturity, it sinks to the bottom of the sea, transforming into a polyp, on which new formations are formed, from which new jellyfish subsequently arise.

This process is repeated more than once, which means that it is constantly reborn, and can die only if it is eaten by some predator. These are the interesting facts about jellyfish that scientists recently told the world.

Scyphojellyfish

Scyphoid jellyfish have a more complex structure compared to hydromedusae: they are larger than representatives of other species - the largest jellyfish in the world, the Cyanea jellyfish, belongs precisely to this class. At approximately 37 meters long, this giant jellyfish is one of the longest animals on Earth. Therefore, she eats a lot: during her life, the largest jellyfish eats about 15 thousand fish.

Scyphojellyfish have a more developed nervous and muscular system, a mouth surrounded by a huge number of stinging and tactile cells, and a stomach divided into chambers.

Like all jellyfish, these animals are predators, but deep-sea animals also feed on dead organisms. The touch of a scyphoid jellyfish to a person is quite painful (the feeling as if bitten by a wasp), and a mark resembling a burn often remains at the point of contact. Its bite can also cause an allergic reaction or even painful shock. Having seen this animal, it is advisable not to take risks and, when swimming past, not to touch it.

Some of the most striking specimens of this species, in addition to the Cyanea jellyfish, are also the Aurelia jellyfish (the most typical representative) and the Golden jellyfish - an animal that can only be seen on the Rocky Islands archipelago in Palau.

The golden jellyfish is notable for the fact that, unlike its relatives, who live only in the seas, it lives in Jellyfish Lake, which is connected to the ocean by underground tunnels and is filled with slightly salted water. Representatives of this species also differ from marine species in that they completely lack pigment spots, have no stinging tentacles, and no tentacles that surround the mouth.

Although the golden jellyfish is a scyphojellyfish, over many years it has turned into a completely different species that does not pose a danger to humans, since it has significantly lost its stinging ability. An interesting fact is that the Golden Jellyfish began to grow green algae on its body, from which it receives part of its nutrition. The Golden Jellyfish, like its marine relatives, feeds on plankton and has not lost the ability to migrate - in the morning it swims to the east coast, in the evening it swims to the west.

Box jellyfish

Box jellyfish have a more advanced nervous system compared to other representatives of the cnidarian class. They are the fastest of all jellyfish (able to reach speeds of up to 6 m/min) and can easily change the direction of their movement. They are also the most dangerous representatives of jellyfish for humans: the bites of some representatives of box jellyfish can be fatal.

The most poisonous jellyfish in the world belongs to this species, lives near the Australian coast and is called the Box Jellyfish or Sea Wasp: its poison can kill a person in just a few minutes. This wasp is almost transparent, of a pale blue hue, which is why it is difficult to notice on the water, which means it is easier to stumble upon it.

The Sea Wasp is the largest jellyfish in its class - its body is the size of a basketball. When a sea wasp simply swims, its tentacles are reduced to 15 cm in length and are almost invisible. But when the animal hunts, they stretch up to three meters. Sea Wasps feed mainly on shrimp and small fish, and they themselves are caught and eaten by sea turtles - the only animals on our planet that are insensitive to the poison of some of the most dangerous creatures on Earth.