Are there jellyfish? What do jellyfish eat, what is their diet? Why are these animals dangerous? One species of jellyfish may be immortal

Greek heroes turned to stone under the gaze of the mythical witch Medusa Gorgon. Will the real and at the same time the world's largest jellyfish, the Arctic cyanide, make you freeze from shock? This floating nightmare has a 2m diameter bell and extends its tentacles up to 30m! Learn the truth about giant jellyfish, their size and lifestyle, and the chances of encountering them in the wild.

First place: Arctic cyanide - the longest animal on the planet

The owner of the longest body prefers the cold waters of the White, Kara and Barents Seas, although he often descends to the latitudes of Boston and northern Portugal. In 1870, residents of one of the villages on the shores of Massachusetts Bay went out to collect fish left on the sand after a storm, and found a gigantic jellyfish thrown out by the sea.

Animal measurements showed:

• 7.5 feet (2.3 m) - span of the bell;
• 120 feet (36.6 m) - the length of the tentacles;
• 121.4 feet (37 m) - full length from crown to tip of tentacles.

Even the blue whale falls short of the cyanide record of 3.5m!

What does a giant jellyfish look like and what does it eat?

The dome of cyanide, flickering with a greenish light, is painted burgundy closer to the edges and is divided into 16 lobes. Numerous tentacles of the animal stretch behind the dome in a sloppy pink train. Thanks to them, the jellyfish received a second name - hairy.

For a person, a meeting with an Arctic giant is fraught with painful burns. The National Geographic Society of the United States considers cyanide to be potentially deadly, although the case of death from its poison was recorded only once.

Runner-up: Nomura's bell, a yellow giant from the Yellow Sea

Kanihi Nomura, a zoologist and at the same time director of fisheries in the Japanese prefecture of Fukui, puzzled by the clogging of nets by jellyfish, found and described this species in 1921. The animal resembles a clump of tangled fibers from the central part of a pumpkin fruit, hanging from a two-meter bell. The second name of the giant is the lion's mane.

Nomura's tentacles are small, but the mass of one specimen reaches 200 kg. In 2009, a fishing boat capsized off the coast of Japan, the crew of which struggled with nomura that filled the net. The efforts of fishermen to throw the lion's mane out of the nets end sadly: numerous tentacles always find a small strip of open skin, even on a person dressed in a sea robe.

What burns the bell Nomura and his brothers

Jellyfish are slow and clumsy, it is difficult for them to keep the caught prey. So you have to act with a paralyzing poison, grow stinging cells with a coiled harpoon thread inside. When a crustacean or fish touches a tiny protrusion near such a cage, the thread instantly shoots, sticks in the side and injects poison.

Jellyfish toxins are little studied, but it has been established that one of their components is histamine, which is responsible for a sharp allergic reaction. Other substances in the composition of the poison affect the nervous system, paralyzing planktonic trifles and causing severe pain in marine mammals and humans.

Third place: chrysaora - a tender and burning beauty

Chrysaora chose the eastern and western shelves of the North American continent. Its dome reaches a meter in diameter, painted in sandy color with dark radial stripes. 24 thin stinging tentacles up to 5 m long hang from the edges of the dome. 4 more tentacles grow around the mouth, located on the underside of the dome, lush, like a feather boa. All together it resembles a ladies' hat with ribbons.

The second name of the underwater beauty is sea nettle. Like the plant of the same name, chrysaora burns sharply, painfully, but not for long. After an hour, the burning and itching stop, and the next day, redness also disappears.

How chrysaors migrate

There is an opinion that jellyfish only go with the flow. However, they easily move where they want, taking water under the dome and throwing it out with strong shocks. This mode of movement is called reactive.

Chrysaors make multi-day sea voyages in search of prey: crested jellyfish and plankton. Sometimes they gather in clusters of tens of thousands of individuals - zoologists call this phenomenon "swarm" or "bloom". Why the Chrysaors behave this way remains to be explored.

Fourth place: purple striped jellyfish

This rare creature lives off the coast of California. The diameter of its bell reaches 70 cm, the length of thin marginal tentacles is 2 m. In its youth, the jellyfish is colorless, it is decorated with barely visible dark stripes and edging along the edge of the dome. With age, the stripes become bright brown, and the jellyfish itself acquires a rich blueberry color.

The stings inflicted by the purple striped jellyfish are not fatal, but unpleasant, like a lash. In 2012, 130 vacationers on a Monterey Bay beach were injured after encountering a large group of young, and therefore hard to see, animals in the water.

Why is the body of a jellyfish transparent?

The jellyfish does not have a single internal organ. Their flesh is two rows of cells, between them is laid a thick layer of gelatinous substance, which is 98% water. The jellyfish seems to be made of liquid glass.

Cells share all the work of the body. Some produce toxins, others digest prey, others are responsible for sensitivity. There are cells whose duties include the prompt restoration of parts of the body bitten off by turtles and other predators. But since there are only two layers of cells, the general outlines of objects can be seen through the jellyfish.

Fifth place: Black Sea cornerot

For the Mediterranean and Black Seas, this is the largest representative of jellyfish. The diameter of the bell reaches 60 cm, weight - 10 kg. Cornerot does not have long trapping tentacles characteristic of chrysaora or cyanide. There are small oral lobes resembling young roots of well-fed seedlings.

Cornerots are hardly noticeable, because on their transparent colorless body there is only one colored area - the purple edging of the dome. Bathers discover the jellyfish when they touch the floating jelly. For most people, this animal is safe, and only severe allergic people react to its soft touch with a scattering of urticaria.

Can a jellyfish feel

Sight, hearing, taste - this is not about jellyfish. The nervous system is too primitive. However, sailors have long noticed that before a storm, cornerots disappear, go away from the coast.

It turned out that along the edges of the dome, the animals carry tubes with lime crystals. In response to infrasounds that appear in the sea 10-15 hours before the storm, the crystals begin to move and touch microscopic sensitive tubercles.

This signal is received by nerve cells. Now the sailors are armed with the "jellyfish ear" device, which notifies in advance of the approach of bad weather.

The world's largest jellyfish cyanide and its smaller sisters are one of the most beautiful inhabitants of the ocean. Slowly and mysteriously they dance in the thickness of salty water for hundreds of millions of years. During this time, they acquired delicate colors, burning poisons and the finest hearing. But zoologists are sure that far from all the secrets of transparent beauties have been revealed.

The Black Sea jellyfish are the oldest jelly-like organisms without a skeleton or tissue base. They are found only in salt water of different saturation, they move chaotically, unconsciously. The existence of jellyfish cannot be attributed to any of the evolving categories. For 650 million years since their appearance, these transparent gelatinous animals have not changed one iota.

Anatomy

The body of a jellyfish is extremely primitive: of the internal organs, it has only a stomach, which is connected to the mouth opening. There is no hole for the withdrawal of waste products; the animal also pushes out all the waste food masses through the mouth. The stomach in most species of jellyfish serves to move in space. It works on the principle of a jet nozzle, contracting, pushing out the collected water and thereby creating thrust, due to which the movement occurs.

Varieties

In total, thousands of species of jellyfish live in the water bodies of the Earth, seas and oceans. Some live in colonies in the form of huge aggregations, slowly migrating with the current or under the influence of the wind. Others are, as a rule, rather large specimens, they live apart, hunt alone, but do not have housing. Jellyfish do not have a settled reflex, and they never linger in one place.

The stinging jellyfish of the Black Sea are not numerous, there are only three types of them: Cornerot, Aurelia and Mnemiopsis. These animals are well studied, but belong to the category of individuals that are under the constant supervision of scientists.

Population spread

The largest Black Sea jellyfish is the rhizostoma-cornerot (Rhizostoma Pulmo). The diameter of her round body can reach half a meter. Cornerot is a well-recognized animal, its difference from other species lies in the absence of tentacles. Instead, massive branches up to a meter long extend from the dome. Each has spongy thickenings.

How is the cornerot arranged?

The dome, or umbrella, of a milky-white jellyfish, rounded, spherical in shape, a purple fringed border runs along the edge. Hanging from under the dome are eight fleshy roots with soft growths that hide poisonous stinging threads. At someone else's touch, the jellyfish throws out stinging arrows and can deliver unpleasant sensations similar to a nettle burn. The poison is weak, its effect wears off after a few days.

Cornerot feeds on small fish, marine worms, and small crustaceans. It paralyzes its prey with poison and then eats it. This species of jellyfish is the largest population in the Black Sea. And although there is no benefit from these animals, it is the cornerot that has a unique ability, for which the Black Sea fishermen appreciate it. This jellyfish is a living barometer, it is sensitive to weather changes, on the eve of a storm it moves away from the coast and goes into the depths.

However, not all marine protozoa have these abilities. Other Black Sea jellyfish, Aurelia and Mnemiopsis, do not feel the approach of bad weather, remain on the surface and die by the thousands. These two species are less numerous, but their numbers are also significant. Habitat - mainly in shallow water, along the coast of Crimea, the area of ​​​​the city of Sudak, the village of Planerskoye and up to Kerch itself. Both species are able to move, but their migration is chaotic.

The Black Sea jellyfish have long been studied by scientists for movement. Over many years of observation, only one conclusion was made: there is no pattern in the movements of gelatinous creatures. They are completely left to the elements and resemble autumn leaves: where the wind blows, they float there. Scientists tried to draw a logical chain, linking the migration of jellyfish with the prevailing winds. However, the jellyfish of the Black Sea, even in this matter, did not live up to expectations, they simply never aspire anywhere. If there is no wind, they stand still, the wind blew - they stirred.

Aurelia

Another large jellyfish that lives in the Black Sea is Aurelia. The diameter of her umbrella, or dome, is about forty centimeters, the body is translucent, usually colorless, but sometimes acquires a pink, blue or purple hue. In the upper part of the dome, four circles are visible, arranged symmetrically. These are the sex glands. The poisonous jellyfish of the Black Sea are same-sex creatures, they fertilize themselves when the time comes for reproduction.

Aurelia, or Sherikh, as it is also called by fishermen who hunt in the Black Sea, feeds on small crustaceans, larvae, and diatoms. Having caught the prey, the jellyfish puts it to sleep with poison and, after the victim is immobilized, slowly eats it. Aurelia lives in the coastal strip, in shallow water, does not swim far into the sea and does not sink into the depths. This format of existence is explained by the fact that the jellyfish is afraid of the cold, its living space is limited to warm water.

However, this species is very tenacious. The jellyfish is thermophilic, but can withstand sub-zero temperatures without dying. Such abilities are observed in many invertebrates, some endure cooling in motion, others fall into anabiosis.

Mnemiopsis

A jellyfish of a relatively small size, up to ten centimeters, which lacks tentacles and stings. Differs in the ability of biological luminescence, that is, it glows in the dark. Having been born, Mnemiopsis develops rapidly, puberty of both males and females occurs no later than two weeks from the date of birth. The process of fertilization is not of a fundamental nature, the jellyfish is capable of self-reproduction. The embryo is formed within twenty hours.

Mnemiopsis feeds only on zooplankton, sometimes it eats caviar of small fish, sprat, tyulka, capelin. Medusa is distinguished by the absence of a satiety reflex, she always eats. In the case of complete filling of the gastric space, the excess is thrown out and the process continues. At the same time, with a complete lack of nutrition, a jellyfish can live from two to three weeks.

Mnemiopsis was brought to the Black Sea from the eastern coast of America at random, in the holds of ships plying along trade routes. Its appearance in the Black Sea caused significant damage to fisheries. Today, measures are being taken to reduce the population of this jellyfish.

Is it necessary to be afraid of gelatinous organisms?

How dangerous jellyfish are in the Black Sea or there is no reason for concern - this issue has been worked out for a long time. There is still no single answer. There is certainly poison in the stinging tentacles of the Black Sea jellyfish, but it is weak, it can provoke a burn like a nettle, but no more. However, there were cases when people who suffered from contact with a jellyfish near the coast of Crimea lost consciousness from severe toxic poisoning. In such a situation, the answer to the question of whether jellyfish are dangerous in the Black Sea should be in the affirmative. Therefore, the conclusions of toxicologists are still vague, research continues.

So, the question is "Jellyfish in the Black Sea are dangerous or not?" while it remains open. In places of their accumulation, it is recommended to be careful and touch their umbrellas less, and especially the tentacles. In addition, every bather must know which jellyfish in the Black Sea sting and which are absolutely harmless. This information will help you avoid being bitten by a harmless animal if not provoked.

When do jellyfish appear in the Black Sea?

Invertebrates, especially marine ones, have their own “holiday season”, when they are most comfortable in their native element, warm and have plenty of food. For the Black Sea jellyfish, this is three months a year: July, August and September. At this time, they actively breed, swim to the best of their ability, and a person should not disturb harmless creatures during this period, it is better to let them live their lives. The time when jellyfish appear in the Black Sea is not precisely defined, every year the time is different, but approximately it is the end of June - the beginning of July.

Jellyfish lack a brain or even a simple rudimentary nervous system, but they seem to show some signs of higher nervous activity.

New discoveries by biologists show that jellyfish from time to time are in the sleep phase. If the scientific research, published in the journal Current Biology, is confirmed by future research, then jellyfish will become the first invertebrates in the world that lack a higher nervous organization, but are able to sleep. This discovery could support the theory that sleep is an inherent property of neurons. To be more precise, sleep may be the ability that nerve cells provide even without the presence of complex organization.

“The novelty of the discovery lies in the fact that this invertebrate animal, which appeared on our planet a very long time ago, differs from humans and higher animals in the mechanism of sleep,” says study co-author Claire Bedbrook.

The origins of sleep

Sleep plays a huge role in the process of survival, but no one can say with certainty for what reasons it developed in nature. A 1995 study found that after completely depriving rats of a night's rest, the rodents died within the next three weeks. It has also been found that protozoan arthropods, such as the worm Caenorhabditis elegans, which has 302 neurons and an underdeveloped nervous system, exhibit phases of wakefulness and rest similar to sleep.

Ravi Nath, a graduate student at Caltech, and his lab assistant, Paul Sternberg, wondered if evidence could be found for sleep in simpler animals.

As it turned out, in parallel with this, another graduate student at the institute, Michael Abrams, raised jellyfish in the laboratory of biologist Leah Goentoro for a completely different scientific research. He noticed that the Cassiopeia jellyfish, or upside down jellyfish, becomes less active at night. In the wild, the invertebrate spends most of its time with its tentacles up on the ocean floor.

“Her body pulses about once a second,” Abrams told Live Science. “This position makes the jellyfish a very easy object for scientific observation.”

Jellyfish behavior

Abrams, Nat and Bedbrook formed a single team of scientists. The purpose of their study was to study the behavior of jellyfish. To prove that jellyfish sleep, biologists had to argue that the animal's behavioral model met the generally accepted criteria for sleep.

The main indicators should include:

• reduced physical activity, which differs from that observed in a comatose or unconscious state;
• a decrease in the level of sensitivity to stimuli compared to the state of wakefulness;
• regulation at the level of homeostasis, which suggests the existence of some kind of innate mechanism that provides sleep and the animal's need for rest.

Conducted experiments

Medusa Cassiopeia, known in biology due to its special body position as a shifting jellyfish, according to scientists, sleeps at night. To measure the activity of the animal, the researchers recorded the rate of pulsation of the bell of 23 jellyfish for a week. It was found that the intensity decreased by 32% at night and amounted to approximately 1155 impulses for 20 minutes per day and 781 impulses for 20 minutes per night.

When the scientists put some food into the jellyfish container, the invertebrates changed their location, and their body pulsation reached daily levels. The scientific study indicates that this rest period was easily reversible.

But are jellyfish becoming less active than usual? To find out, the biologists placed the animals in small containers made of PVC pipes with a mesh bottom. They carefully placed the jellyfish on the bottom of the tank, then quickly shook the container, causing it to float. Jellyfish prefer to sit so as to be able to emerge. But they did it much faster during the day, starting to pulsate 2 seconds after they moved from the depth to the surface of the water. It took them about 6 seconds to start pulsing and moving after waking up from sleep.

Does homeostasis underlie jellyfish sleep?

The researchers then tested whether the jellyfish's sleeping behavior was controlled through homeostasis. Simply put, the question was, would invertebrates be active the next day if their sleep was disturbed during the night?

To learn about this, the researchers artificially created small waves in the container for 10 seconds every 20 minutes. They found that when they prevented the jellyfish from resting, during the last 6 hours of the night, the animal had a decrease in pulsations, and for four hours the next day - by 12%. The impaired response looked as if the animals were having trouble waking up. When the researchers interrupted the jellyfish's sleep throughout the night, the activity of the animals the next day was reduced by 17%. Interestingly, after a full night of rest without any disturbance, the next day the jellyfish returned to its normal level of activity.

The evolution of sleep

The main question is whether the cycle of sleep and wakefulness in jellyfish is stable. Scientists have long established that the same genes and molecules are responsible for controlling sleep in worms, flies, zebrafish and humans. But they were not found in jellyfish.

In one interesting experiment, biologists diluted a container of water containing invertebrates with two substances that affect the inhibition of nerve cells in humans. These were melatonin and antihistaminepyrilamine. When these substances were added, jellyfish also showed less activity. Thus, it is assumed that the mechanism of sleep in the oldest invertebrates on earth and humans may have the same biological roots.

Search for new research approaches

“What is the general principle responsible for this state of sleep that all living beings have?” asks the biologist Bedbrook.

The next step in the scientific study, Nutt says, could be to use electrodes to track the activity level of the jellyfish's neurons while they sleep.

“It remains to be seen whether there are other species of jellyfish that also rest,” adds biologist Bedbrook. "Our research team would also like to understand if sponges, which are living beings of a lower level than jellyfish, sleep." Sponges do not have a nervous system at all, although they do have some rudimentary genes and proteins that have been found in the nervous systems of other animals.

Question: I wonder if there are species of jellyfish that can live in a freshwater aquarium? Jellyfish are really cool, but I only have a freshwater aquarium.

Answer: Yes, there are jellyfish living in fresh water. For example, Craspedacusta sowerbyi. These are freshwater jellyfish that live on almost all continents, but are very rare in Africa. Even before 1908 there was no mention of these animals. Freshwater jellyfish inhabit lakes, reservoirs, and sometimes artificial reservoirs, such as water-filled quarries or mines. Although these jellyfish are different, nevertheless, they all prefer the stagnant water of a lake or reservoir rather than the turbulent turbulent flow of the river.

Unfortunately, I do not know a single person who would keep such jellyfish in a home aquarium. And I don't know of any pet store that sells them. Since these aquatic creatures require special conditions, it is difficult for me to recommend specific aquarium accessories. As far as I know, these jellyfish most often prefer to be located at the bottom of the reservoir, thus conserving energy for capturing prey and reproduction.

Freshwater jellyfish usually feed on zooplankton. With the help of nematocytes (stinging cells), they sting and paralyze prey, which gives them the opportunity to master it. These jellyfish are also good at adapting to cold water. In the cold season, they curl up and practically hibernate until the water temperature starts to rise again.

Freshwater jellyfish are quite difficult to keep in a home aquarium. You must make sure that the filtration system does not draw the jellyfish into the filter. In this case, it is better to use a sponge filter. Also make sure that the movement of water in the aquarium is minimal. Most importantly, remember that jellyfish need a constant source of food, shrimp and daphnia are the best.

Otherwise, there is very little information on how to keep freshwater jellyfish. Perhaps this is due to the fact that few people keep jellyfish, and even if they do, it is more likely that they are marine rather than freshwater. Interestingly, the stinging cells of freshwater jellyfish are not strong enough to sting a person. In this regard, they are safer than their marine counterparts. We will be glad if someone shares their experience in keeping freshwater jellyfish at home or in the laboratory.

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

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

Who are jellyfish

Zoologists, speaking of jellyfish, usually mean all mobile forms of intestinal 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 inland), 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 who prefer cold waters, species that live only near the surface of the water, and those that live only at the bottom of the ocean.

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

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

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

Along the edges of the body 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 are composed of string cells that contain poison and are therefore directly intended for hunting. Interestingly, even after death, jellyfish are able to sting for another half a month. Some species can be deadly even to humans. For example, an animal known as the "Sea Wasp" is considered the most dangerous poisonous animal in the world's oceans: scientists say 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 underside 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 maces. 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 whose body size exceeds two meters, and together with tentacles - all thirty (for example, the largest jellyfish in the world's oceans, Cyanea, which lives in the Northwest Atlantic, the body size is 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 are, however, not able to see objects). Interestingly, some specimens glow in the dark, while in species living at great depths, the light is red, and those that live closer to the surface are blue.

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

Ways 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, they move using the current and thin muscle fibers of their body: contracting, they fold the body of a 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. Where exactly they need to move, they are helped to determine the organs of balance 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, thus forming two new individuals! If this is done with an adult jellyfish, an adult copy will appear, from a jellyfish larva - a larva.

reproduction

Looking at these amazing translucent creatures, many people 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, it is possible both sexual (they are of different sexes) and vegetative reproduction. The first involves several stages:

1. In these animals, the germ cells mature in the gonads;
2. After the eggs and spermatozoa mature, they come out through the mouth opening and are fertilized, resulting in the appearance of a jellyfish larva - planula;
3. After some time, the planula settles to the bottom and is fixed on something, after which a polyp appears on the basis of the planula, which reproduces by budding: on it, layering on each other, daughter organisms form;
4. After some time, they peel off and swim away, representing a born jellyfish.
   Reproduction of some species is somewhat different from this scheme. For example, the pelagic jellyfish does not have a polyp stage at all - the cubs appear directly from the larva. But bougainvillea jellyfish, one might say, are born, since polyps are formed directly in the gonads, without separating from adults, without any intermediate stages.

Nutrition

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

So, jellyfish see almost nothing and do not have any sense organs, they hunt with the help of stringing tentacles, which, having caught 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 - prey sticks to the tentacles, the second - gets entangled in them.

Classification

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

hydrojellyfish

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 hydrojellyfish 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 some predator eats it. Here are some interesting facts about jellyfish that scientists recently told the world.

Scyphomedusa

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

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

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

One of the brightest specimens of this species, in addition to the Cyanei jellyfish, is 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, living only in the seas, it lives in the Jellyfish Lake, which is connected to the ocean by underground tunnels and is filled with lightly salted water. Representatives of this species differ from marine individuals also in that they completely lack age spots, there are no stinging tentacles, as well as tentacles that surround the mouth.

The golden jellyfish, although it belongs to the scyphomedusa, over the years 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 members of the cnidarine class. They are the fastest of all jellyfish (capable of speeds up to 6 m/min.) and can easily change their direction of movement. They are also the most dangerous representatives of jellyfish for humans: the bites of some representatives of box jellyfish are fatal.

The most poisonous jellyfish in the world belongs to just 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 hard to see 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 the sea wasp is just swimming, 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 one of the most dangerous creatures on Earth.