Why do jellyfish appear near the shore? Interesting facts about jellyfish. The most dangerous poisonous jellyfish

Scientists do not give a definite answer to the question of how long jellyfish live. Many agree that life cycle These animals are short-lived and the lifespan of most species ranges 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 inland), sometimes in closed lagoons or lakes with salt water on the 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.

We got ours modern name these creatures 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

One more interesting feature of these creatures is their ability to restore lost parts of the body - 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, it is possible both sexually (they are heterosexual) and vegetative propagation. 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 prominent representatives hydromedusa - 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. Like these ones Interesting Facts Scientists recently told the world about jellyfish.

Scyphojellyfish

Scyphoid jellyfish have a more complex structure compared to hydromedusae: they are larger than representatives of other species - the most big 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 ones 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.

One of the most striking specimens of this species, in addition to the Cyanea jellyfish, is also the Aurelia jellyfish (the most typical representative) and the Golden Jellyfish, an animal that can only be seen in 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 specimens 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 away to East Coast, in the evening - sails 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 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 most large jellyfish in her class - her 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. Eating Sea Wasps mostly shrimp and small fish, and they themselves are caught and eaten sea ​​turtles- the only animals on our planet that are insensitive to the poison of some of the most dangerous creatures on the ground.

Over the past few years, Tunisia has become extremely popular among Russian tourists. This is explained by the fact that holidays in Tunisia are quite inexpensive and can compete even with the resorts of Egypt and Turkey in terms of prices and variety of entertainment infrastructure. In addition, on the territory of this African country there are a great many natural, cultural and historical monuments.

Basically, the climate of Tunisia is mild, even in winter, so you can feel comfortable here at any time of the year. Holiday seasons in Tunisia are conventionally divided into two periods - summer and winter. In summer, when the air temperature is about 25-30ºС and the water temperature is 26-28ºС, travelers go to the coast. In winter, when the air warms up no more than 12ºС, and the water - no more than 15ºС, lovers of the famous thalassotherapy, spa treatments and Tunisian hammams come to the country.

If you still prefer to bask in the hot rays of the sun and swim in the warm sea, then before planning a trip to the resorts of Tunisia, you should pay attention to such an unpleasant fact as jellyfish season in Tunisia.

Features of the jellyfish season in Tunisia

As a rule, the largest concentration of jellyfish off the coast of beaches is observed around mid-August and lasts about a couple of weeks. However, the jellyfish season in Tunisia does not occur every year, and largely depends on weather conditions. The more the water near the shore warms up, the more likely it is that in the near future the entrance to the sea will become quite unpleasant for swimmers.

Some hotels in Tunisia that have their own beach often fence it with a special net that traps jellyfish and prevents them from ruining the holiday of swimmers.

Is the jellyfish season dangerous in Tunisia?

In general, jellyfish are not dangerous to human life, but their burns can cause some trouble for people with sensitive skin, as well as for those who are susceptible to various allergic reactions. Despite the fact that even representatives of local population However, when going to Tunisia during the jellyfish season, you should always have special medications for burns with you. It is not always possible to quickly find a pharmacy, even near the best beaches in Tunisia.
If you are unlucky enough to get stung by a jellyfish, never wash the affected skin with water or scratch it. It is best to wipe the area with vinegar, alcohol, or alcohol-containing medicinal products, and then apply a gel or ointment that relieves swelling and itching. If such remedies are not available, apply a tomato slice to the bite site. If an allergic reaction occurs (most often this happens in young children), you should immediately consult a doctor.
The jellyfish season in Tunisia is most dangerous in the areas of Hammamet, Monastir and Sousse - the highest concentration of jellyfish is observed here during this period. The following types of jellyfish are found off the coast of Tunisia: cotylorhiza, charibra, chryozora, pink anemone and black jellyfish. The last two species are the most poisonous, but also the least common. In general these sea ​​creatures can be found not only in August-September. Single specimens periodically appear off the coast, regardless of what sea in Tunisia is on this moment- cool or warm.

How to avoid meeting jellyfish in Tunisia?

When is the best time to go to Tunisia so as not to spoil your beach holiday?
The jellyfish season in Tunisia is a non-periodic phenomenon, but it is best to choose June, July and early August, then the second half of September and early October. If your trip is scheduled for the end of summer - beginning of autumn, be careful when swimming and exercise maximum caution so that you do not spend the remaining days before the end of your vacation on the shore, or, even worse, in a hotel room or local hospital.

Have a nice holiday in Tunisia!

I live in Crimea and have long observed that there are a lot of jellyfish when the sea warms up well - this is in the middle of August. During this period, the sea glow is still observed in the evening, i.e. glow of marine organisms occurs.

At the end of summer - August (second half and September). But the number of these same jellyfish is impossible to predict. It also depends on sea ​​currents and on water temperature. Therefore, if you are interested in looking at jellyfish, plan your vacation for this time of year.

Closer to the onset of autumn, jellyfish in the Black Sea become noticeably more numerous. In addition, they can appear in July; we went on vacation once, and the sea was swarming with them when the water was warm and sticky. So it’s better to rest at the beginning of summer if you don’t like them.

Jellyfish appear in the Black Sea in August and September. The water is very warm at this time, especially off the coast.

I literally saw an invasion of jellyfish in the second half of August on Central Beach in Sochi. At first we didn’t even understand what was happening to the water - it turned silver in the sun and was somehow unusual. And when we got closer, we saw that there were jellyfish, apparently and invisible! They were the most different sizes- from very tiny to quite large. They penetrated the water column.

The waves washed them ashore, the children collected them and sent them back to the sea. Moreover, there were vacationers who were not embarrassed by the full sea of ​​jellyfish, and they swam! No one complained of a burn or bite. The jellyfish were good). But we didn’t dare to swim that day. The next day they almost completely disappeared, the sea near the shore cleared, and only single jellyfish were found.

I visited the Black Sea for the first time at the end of July, in the port city of Tuapse. And there were jellyfish, at first there were not many of them, occasionally they were washed ashore by a wave. Mostly small.

And then a couple of days later there was a storm and the next morning there were a lot of them in the sea, from large to small. I didn’t dare to swim anymore. Jellyfish are nasty, and some sting.

There are usually a lot of jellyfish near the shore after a storm. And in front of him they try to swim away.

Jellyfish love warm water, so they are most abundant in the Black Sea towards the end of summer - August, September. Although many indigenous people note their presence in large quantities and in early June, near the shores of some beaches.

When there are a lot of jellyfish, many residents of the Black Sea try not to visit the beach and wait for the jellyfish to swim away. After all, sometimes you come across individuals that sting painfully. It is unpleasant. Moreover, if you have been bitten painfully by a jellyfish at least once, then from that moment you begin to fear them.

There are many small jellyfish in the Black Sea, but most often they live in the water column. Previously, mussels were caught in the Black Sea and biological additives were made from them for animals, but unfortunately, production is now closed. After all, from 5 kg you get 100-200 grams useful product, the rest is all water.



Usually in the second half of August the jellyfish season begins on the Black Sea. Sometimes there are simply unimaginably many of them, and sometimes they hardly bother you. Why does this depend? Yes, it depends on many factors: on how warm the sea is, on how strong the current is in a particular place.

However, the presence of jellyfish is definitely not a reason to refuse a vacation at this time. Moreover, the end of August - beginning of September is an amazing, cool time for relaxation - the water has warmed up, there are fewer vacationers, and you can’t get enough of local fruits and vegetables. In addition, jellyfish in the Black Sea are quite harmless. If one of them does bite, just lubricate the affected area with vinegar and it will quickly go away (I was taught this little trick in Bulgaria).

Many of those who vacationed at sea encountered jellyfish. This helped to realize the fact that they cannot be called ordinary and harmless creatures. Let's look at some interesting facts about jellyfish.

What does science know about jellyfish?

Researchers believe that jellyfish have been around for about 650 million years. They are found in all layers of each ocean. Various live in both salty and fresh water. Their primitive nervous system, which is located on the epidermis, allows you to perceive only smells and light. The nerve networks of jellyfish help them detect another organism through touch. These "animal plants" essentially do not have a brain or sensory organs. They do not have a developed respiratory system, and breathe through thin skin, which absorbs oxygen directly from the water.

While exploring interesting facts about jellyfish, scientists noticed that these creatures are able to positively influence people experiencing stress. For example, in Japan they breed jellyfish in special aquariums. Their smooth and measured movements act as a sedative. Although such pleasure is expensive and causes additional troubles, in general it is justified.

Jellyfish are more than 90 percent water. The venom of their tentacles is used as a raw material for drugs that regulate blood pressure, and for the treatment of respiratory diseases.

It was called the “Portuguese man-of-war” by some 18th-century sailors who liked to tell others about the jellyfish floating like a Portuguese warship of the Middle Ages. In fact, her body is very similar to this vessel.

Her official name- physalia, but this is not one organism. We are talking about a colony of jellyfish and polyps in different modifications, which interact very closely and therefore look like one creature. The poison of some types of physalia is deadly to humans. Most often, the habitats of the Portuguese man-of-war are limited to the subtropical parts of the Indian and Pacific Oceans, as well as the northern bays Atlantic Ocean. In more rare cases, they are carried away by currents into the waters of the Caribbean and Mediterranean seas, to the shores of France and Great Britain, to the Hawaiian Islands and the Japanese archipelago.

These jellyfish often swim in huge groups of several thousand individuals in warm waters. The transparent and shiny jellyfish body rises above the water by about 15 centimeters and moves along a chaotic trajectory regardless of the wind. Those individuals that swim near the shore are often thrown out powerful winds to land. In the warm season, physalia swims away from the shore, it moves with the current towards one of the earth's poles.

Distinctive features of physalia

Other interesting facts about this type of jellyfish concern their unique features. Physalia is one of two biological species, capable of glowing red. Another Portuguese warship uses its air bag filled with nitrogen as a sail, carbon dioxide and oxygen. If a storm approaches, the jellyfish releases its bubble and goes under water. Small perches like to swim near its tentacles; they do not sense a toxic environment and have serious protection from enemies, as well as food particles. Perches attract other fish with their appearance, which become food for these invertebrates. This is such a symbiosis.

There are a considerable number of species known today as physalia. In the Mediterranean Sea alone, researchers have discovered about 20 species of Portuguese man-of-war.

Physalia jellyfish, interesting facts about reproduction

It is not known exactly how this jellyfish reproduces. However Scientific research showed that they reproduce asexually, and in each colony there are polyps that are responsible for reproduction. In fact, they are the ones who create new colonies. Portuguese man-of-war They differ in that they can reproduce continuously, which is why the number of nascent jellyfish in the waters of the oceans and seas is growing.

Another common version of the reproduction of physalia indicates that, when dying, the jellyfish leaves behind some organisms that exhibit sexual characteristics, after which new individuals are formed. This theory has not yet been proven.

About the tentacles of the Portuguese man-of-war

Regarding the jellyfish tentacles, the interesting facts are that their structure is unique. The “limbs” of jellyfish are equipped big amount capsules containing poison, the composition of which is similar to the poisonous substance of a cobra. Each of these small capsules is a hollow, twisted tube with fine hairs. If contact occurs between the tentacles and the fish, the fish will die due to the stinging mechanism. When a person receives a burn from this jellyfish, he experiences sharp pain, develops a feverish state, and has difficulty breathing.

The interesting facts about jellyfish don’t end there. The tentacles of these invertebrates can reach 30 meters in length. In addition, a person who is engaged in swimming, enjoying the process itself, will not always be able to see a bright blue-red bubble on the water and realize the danger that threatens him.

Irukandji jellyfish: interesting facts about the danger posed by it

This small jellyfish, which lives off the coast of Australia, produces toxic substances that act stronger than poison cobras There are 10 types of Irukandji, 3 of which are deadly. The bite is almost imperceptible, but its consequences are a powerful heart attack, which in some cases can result painful death. And all this can happen in just 20 minutes. Because these invertebrates are so small and practically invisible, they can easily penetrate any barrier network that is designed to big creatures posing a danger to swimmers and vacationers.

There are some other interesting facts about this species of jellyfish. Since fishermen often fell ill with a strange disease after each trip to the sea, they realized that the reason for this was contact with some kind of sea creature. The jellyfish was named after the Irukandji tribe. Over time, thanks to Dr. Barnes, it was finally possible to establish that the cause of the disease was contact with jellyfish. Although its size is quite small, its tentacles reach a length of 1 meter. The pain from the bite is so severe that it forces you to double over, is accompanied by severe sweating and vomiting, and your legs tremble violently.

conclusions

Although these invertebrate organisms are difficult to see in the water, regardless of their size, you still shouldn’t be careless and inattentive while swimming in the sea or walking along the shore - for the sake of your health. Many types for human health and life.

However, they also do useful features in their habitats, they are used in medicine as raw materials for drugs. And who knows, maybe humanity will be able to get even more benefits from jellyfish.

Why jellyfish swim to the seashore, you will learn from this article.

Why do jellyfish swim to the shore?

Jellyfish swim to the shore to leave their offspring. Their total invasion in shallow water, closer to the shore, is just a temporary phenomenon. Having taken care of their future, they swim back into the depths of the sea.

Why are there so many jellyfish in the sea?

There are not always many jellyfish in the sea, but often the coast is crowded with such inhabitants. This means that jellyfish are in mating season.

Jellyfish are among the most ancient inhabitants of our planet. They appeared more than 650 million years ago. And in the process of evolution they have changed little. These animals are 95% water, and 5% muscle fibers in their body make jellyfish a full-fledged organism.

In the sea you can find three types of jellyfish:

• Aurelia

It is also called the “eared jellyfish”. And all because there are transparent white tentacles along the entire circumference of the aurelia. This is the most small view jellyfish A peculiarity of the animal is the presence of stinging cells in the body, which can damage the edges of the lips and the mucous membrane of the eyes.

• Cornerot

By appearance it resembles a fleshy bell or dome with a heavy beard of mouth cavities. The lace lobes are equipped with poisonous stinging cells. It is better to swim around such jellyfish.

• Mnemiopsis

This type of jellyfish does not have stings or tentacles. In the Black Sea it is the smallest. Its peculiarity is the ability to glow. Therefore, another name for Mnemiopsis is nightlight.