How Black Sea jellyfish reproduce. The whole truth about how jellyfish reproduce

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"

reads as the most dangerous poisonous animal in the world's oceans: scientists claim that its poison is quite 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 by 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. coelenterate cnidarian jellyfish reproduction

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, germ cells mature in the gonads;
• 2. After the eggs and sperm mature, they come out through the mouth and are fertilized, resulting in a jellyfish larva - 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 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 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.

The Scyphoid class includes jellyfish that inhabit the seas and oceans (they live only in salt water), which are able to move freely among the expanses of water (with the exception of the sessile jellyfish, which leads a sedentary lifestyle).

general characteristics

Scyphoid jellyfish live everywhere; they have adapted to life in cold and warm waters. There are about 200 species. They are transported over considerable distances with the current, but can also move independently. Thus, with the help of active contractions of the dome and the release of water from it, the jellyfish can develop greater speed. This method of movement was called reactive.

The jellyfish has the shape of an umbrella or a longitudinally elongated dome. There are quite large species. Some representatives of the scyphoid class reach 2 m in diameter (Cyanea arctica). Many tentacles extend from the edges of the bell, which can grow up to 15m in length. They contain stinging cells that contain toxic substances necessary for protection and hunting.

Structural features

In the middle of the inner concave part of the umbrella there is a mouth, the corners of which turn into oral lobes (necessary for capturing food). In rootostomes, they grow together and form a filtering apparatus for absorbing small plankton.

Scyphoids are endowed with a stomach with 4 pocket-like protrusions, and a system of radial tubules, through which nutrients from the intestinal cavity are distributed throughout the body. Undigested food particles are sent back to the stomach and eliminated through the mouth.

The body of jellyfish consists of two layers of epithelial cells: ectoderm and endoderm, between them is mesoglea - jelly-like tissue. It consists of 98% water, so jellyfish quickly die under the scorching sun. Jellyfish have enormous regenerative abilities; if you cut it into 2 parts, each will grow into a full-fledged individual.

Since scyphoid jellyfish have switched to an active way of life, their nervous system has become more developed. At the edges of the umbrella there are clusters of nerve cells; nearby there are also sensory organs that perceive light stimuli and help maintain balance.

Life cycle and reproduction

Scyphoids go through two phases in their life cycle: sexual (jellyfish) and asexual (polyp).

All representatives are dioecious organisms. The germ cells originate from the endoderm and mature in the pouches of the gastric cavity.

The gametes exit through the mouth and end up in the water. During the process of fusion of germ cells and further maturation, a jellyfish larva, a planula, emerges from the egg. It sinks to depth, attaches to the bottom and enters the asexual phase.

A single polyp (scyphostoma) leads a benthic life and begins to reproduce through lateral budding. After a certain time, the scyphistoma turns into a strobila, then the tentacles begin to shorten, and transverse constrictions form on the body. This is how a division called strobilation begins. Thus, the strobila gives life to young organisms - ethers. The ethers are then converted into adults.

Lifestyle

Scyphoid jellyfish do not live in schools and do not transmit signals to each other, even when at close range. Life expectancy is about 2-3 years, sometimes it happens that a jellyfish lives only a couple of months. They are also often eaten by fish and turtles.

All jellyfish are predatory animals. They consume plankton and small fish, which are immobilized by poisonous cells. Stinging cells release poison not only during hunting, but also to all organisms passing by. Therefore, jellyfish are dangerous for people in the water. If you accidentally catch the tentacles of a jellyfish, it will burn your skin with its poison.

The most common representatives of the class of scyphoid jellyfish are Aurelia, Cyanea, which inhabits the Arctic seas, and Cornerot, which is devoid of tentacles and lives in the waters of the Black Sea.

Meaning in nature and human life

Scyphoid jellyfish are part of the food chain of the world's oceans.

In Chinese and Japanese cuisine, dishes with rhopilema or aurelia are often found. Jellyfish meat is considered a delicacy.

Cornerot is the largest jellyfish in the Black Sea with a dome diameter of about 40 cm. Thus, it serves as a shelter for fish fry and protects them from predators and unfavorable environmental conditions. Sometimes, when the fry grow up, they begin to bite off small pieces of the jellyfish, or may eat it altogether.

Scyphoid jellyfish filter water, clearing it of contaminants.

For humans, the dangerous poison of jellyfish, which causes skin burns, sometimes provokes a painful shock and a person, being at depth, can no longer surface on his own. It is not safe to touch a jellyfish even when it is dead. When touched, an allergic reaction develops, disruption of the nervous and cardiovascular systems, and convulsive attacks occur.

Jellyfish is an invertebrate marine animal with a transparent gelatinous body, along the edges, equipped with tentacles. She is a lower multicellular creature, belongs to the type of coelenterates. Among them there are free-swimming (jellyfish), sessile (polyps), and attached forms (hydra).

The body of coelenterates is formed by two layers of cells - ectoderm and endoderm, between them there is mesoglea (non-cellular layer), and the body also has radial symmetry. Animals of this type have the appearance of an open sac at one end. The hole serves as a mouth, which is surrounded by a corolla of tentacles. The mouth leads into the blindly closed digestive cavity (gastric cavity). Digestion of food occurs both inside this cavity and by individual cells of the endoderm - intracellularly. Undigested food remains are excreted through the mouth.

Jellyfish belong to the scyphoid class. The class of scyphoid jellyfish is found in all seas. There are species of jellyfish that have adapted to live in large rivers flowing into the sea. The body of scyphojellyfish has the shape of a rounded umbrella or bell, on the lower concave side of which an oral stalk is placed. The mouth leads into the pharynx, which opens into the stomach. Radial canals diverge from the stomach to the ends of the body, forming the gastric system.

Due to the free lifestyle of jellyfish, the structure of their nervous system and sensory organs becomes more complex: clusters of nerve cells appear in the form of nodules - ganglia, balance organs - statocysts, and light-sensitive eyes. Scyphojellyfish have stinging cells located on the tentacles around the mouth. Their burns are very sensitive even for humans.

Reproduction of jellyfish

Jellyfish are dioecious; male and female reproductive cells are formed in the endoderm. The fusion of germ cells in some forms occurs in the stomach, in others in water. Jellyfish combine their own and hydroid characteristics in their developmental features.

Among the jellyfish there are giants - Physaria or Portuguese man-of-war (from three or more meters in diameter, tentacles up to 30 m), such creatures can even eat a person. Recently, they have been spotted near the Sea of ​​Japan, and the Japanese and Chinese, who are trying to cook even from them, have added them to various salads, thereby poisoning quite a few people.

The jellyfish looks flabby, but it feels dense to the touch. Although it has neither an internal nor an external skeleton, it retains a certain shape. This is ensured in part by the fact that the gelatinous mass is permeated with strong connective tissue fibers. In addition, the jellyfish pumps water into itself - in the same way, an inflatable raft acquires rigidity when it is inflated with air. This method of maintaining body shape, called a hydrostatic skeleton, is also characteristic of sea anemones and worms.

Jellyfish feeding

A predatory jellyfish captures food with its tentacles and digests it in the body cavity with the help of enzymes in the digestive cells.

Movement of jellyfish:

The movement of jellyfish is carried out by “stepping” and “tumbling”.

Irritability

Irritability is produced by nerve cells scattered throughout the body.

Meaning: Eaten

Some jellyfish are deadly and poisonous to humans. For example, when bitten by a cornet, significant burns can occur. When bitten by a cross, the activity of all systems of the human body is disrupted. The first encounter with a cross is not dangerous, the second is fraught with consequences due to the development of anophiloxia. The bite of a tropical jellyfish is fatal, but the bite of an ordinary jellyfish goes away in 3 days and does not have any consequences.

Interesting facts about jellyfish

Jellyfish help fight stress! In Japan, jellyfish are bred in aquariums. The smooth, leisurely movements of jellyfish calm people, although keeping jellyfish is very troublesome and expensive.

The first robotic jellyfish appeared in Japan. Unlike real jellyfish, they not only swim smoothly and beautifully, but if the owner wishes, they can “dance” to music.

A certain type of jellyfish is caught off the coast of China and eaten! Their tentacles are removed, and the “carcasses” are kept in a special marinade, which turns the jellyfish into a translucent cake of delicate thin cartilage. In the form of such cakes, jellyfish are brought to Japan, where they are carefully selected for size, color and quality. For one of the salads, the jellyfish cake is cut into thin strips about 3-4 mm wide, mixed with stewed vegetables and herbs and poured with sauce.

Jellyfish go through quite a long development path. Fertilized eggs develop into larvae that float freely in the water. These larvae then attach to the seabed and grow into polyps. As a result of division, small jellyfish can bud from the polyp. They grow to adult size and reproduce. This process is called "alternation of generations." Almost all jellyfish live in seawater. However, there are also several freshwater species. In Europe, this is a freshwater jellyfish Craspedacusta with a diameter of only 2 cm, living in ponds and shallow lakes. Now it has become a rarity.

Jellyfish can be round like a ball, flat like a plate, elongated like a transparent airship, very small, like a sea wasp, and huge, like the giant of the Arctic waters, the fiery red lion's mane, whose domed body grows up to two and a half meters in height. diameter, and bundles of wriggling thread-like tentacles, reaching 30 m in length, can cover a five-story building.

Much more modest in size, the pelagia jellyfish, or nocturnal jellyfish, amazes experienced sailors with its bright light in the middle of the night in the waters of the Mediterranean Sea.

Not everyone knows that the beauty of most types of jellyfish can be very deceptive. After all, to a greater or lesser extent, all jellyfish are poisonous. The only difference is that some species are practically not dangerous to humans, others sting like nettles, and a painful burning sensation can be felt for several days, and others cause paralysis that can lead to death.

There are also jellyfish that are completely harmless to humans. This is the well-known glassy-white “eared” jellyfish - Aurelia. It lives in all tropical and moderately warm seas, including here in the Black Sea. These are summer animals. Autumn storms bring death to them, so they have adapted, so to speak, to “put off” their offspring for the winter. On the eve of cold weather, small, slightly more than a centimeter, lumps of living tissue, carriers of the Aurelia genetic code, settle to the bottom of the sea. They are not afraid of storms or cold snaps, and with the arrival of spring, tiny discs separate from them, which grow into adults in one summer.

By the way, if you rub the body of Aurelia into human skin, it becomes immune to “stinging” jellyfish, such as, for example, the same Black Sea rosistoma, otherwise known as corneros.

The most dangerous of all existing jellyfish are sea wasps. They are found in the warm waters of the Indian and Pacific oceans. It's hard to believe that this little blob of living mucus is actually a real killer. And meeting him is almost more dangerous than meeting a shark. The venom of the sea wasp is so strong that if it enters the bloodstream, it can stop a person’s heart in a few minutes. In search of food, such as bottom-dwelling shrimp, these deadly creatures sometimes come very close to the shore. As a result, more than fifty people have died in recent years in the coastal waters of Australia from the poison of these little killers.

The largest existing jellyfish is the giant arctic jellyfish, whose umbrella reaches 2.2 m in diameter; its tentacles are 35 m long. As we see, jellyfish can be gigantic! This giantess, as well as many other jellyfish, paralyze their prey with stinging cells. This poison can be very painful and even dangerous for humans. So some caution will not hurt if you come across a jellyfish with long threads in the sea. On the other hand, you don’t need to think that touching every jellyfish can cause a burn.

Speaking about jellyfish, one cannot help but recall their closest relatives - siphonophores, or, as they are also called, Portuguese man-of-war. The elongated bodies of these animals, similar to air bubbles, sway above the water and in appearance really resemble caravels under sail. Thanks to the obliquely placed comb on its float, the siphonophore goes “in full sail”, always remaining at an acute angle to the wind. And behind it, like a trail, stretch very long (up to 15 meters) and very poisonous tentacles.

The main difference between the Portuguese man-of-war and a jellyfish is that it is not one creature, but a whole community of completely different individuals, each of which has its own task - some control movement, others catch prey, others paralyze it, and others digest and share nutrients with all members of the colony.

During the voyage, the Portuguese warship is accompanied by its own “retinue”. These are small nomei fish that hide from predators under the reliable protection of long tentacles. The poison of the stinging cells of the boats does not affect the nimble escorts.

Jellyfish can be dangerous not only for people, but also for ships. Ship engines are cooled by sea water, which enters through a special hole in the bottom. And if jellyfish get into this hole, they tightly shut off the water supply. The engine overheats and fails until divers clear the live plug.

The hairy cyanea jellyfish, caught in the northwestern part of the Atlantic in 1865, is listed in the Guinness Book of Records. Its cap was 2.28 meters in diameter, and its tentacles extended 36.5 meters. That is, if you stretch the tentacles in different directions, the length of such a jellyfish will be 75 meters. This is the longest animal on Earth!

Many people know that the World Ocean has not revealed even half of its secrets to man. Will we ever be able to know for sure what the depths conceal?

However, people know quite a bit about the inhabitants of the oceans and seas. Our article will tell you about amazing creatures - jellyfish. They are distributed almost throughout the planet; some of them amaze with their beauty, while others seem completely inconspicuous against their background. However, there is one moment in the life of these animals that will clearly interest every lover of wildlife. We are talking about how jellyfish reproduce. If you don't know the answer to this question, our article will probably interest and surprise you.

Invasion of Japan

For the first time, Japanese scientists from the University of Hiroshima began to study this issue seriously. It was noticed that the waters of the Pacific coast of the Land of the Rising Sun are simply teeming with nomura jellyfish (Nemopilema nomurai). Experts became interested in this increase in population and decided to find out its reason.

During the research, they were faced with the need to thoroughly study the question of how jellyfish reproduce.

It was found that the cycle is quite complex. And after birth, giant jellyfish babies, like snowflakes, behave just as aggressively and have the same gluttony as adults.

Discoveries of scientists

Researchers have found that the population explosion was triggered by global warming, due to which conditions for the reproduction of jellyfish have improved. Not only have they increased their populations hundreds of times, but they have also become a serious threat to many ecosystems.

Other genera and species of jellyfish are also considered studied today. It has been established that reproduction can occur in one of two scenarios. Let's consider both methods of jellyfish reproduction in detail.

School lessons

Many people remember from school lessons that jellyfish belong to the type Coelenterates. In many educational institutions, they study the reproduction and development of obelia jellyfish, since this species is very common, is not at all dangerous to humans, and all the signs of the type are clearly expressed. The following illustration shows the obelia jellyfish.

The first thing that may surprise you is the unusual way in which the biomaterials needed for the process are released. Male jellyfish release sperm from their mouths.

In the water column, male cells meet female cells, and fertilization occurs. As a result, larvae - planulae - are formed.

It would seem that there is nothing unusual. But this is just the beginning, the most interesting things are yet to come!

Incredible sequel

The planula sinks to the bottom and attaches itself to it, beginning to form into a polyp. The polyp grows, gradually learning to capture prey passing by.

And here, for everyone who decides to find out how jellyfish reproduce, the most interesting thing begins - the polyp stage ends with typical budding.

The final stage of jellyfish reproduction

Simply put, pieces of matter begin to detach from the polyp, which form into small jellyfish.

Scientists call this method of reproduction incredible, because it combines two main types: sexual and vegetative. It turns out that jellyfish reproduce by alternating these types.

By studying the details of how jellyfish reproduce, scientists have found that the vast majority of species follow this path. However, he is not the only one.

As you know, jellyfish have been roaming the seas for at least 600 thousand years. During this time they learned to survive. Reproduction variability may be one of the mechanisms of species conservation.

Exceptions to the rules

Scientists know of only a few species of jellyfish that lack the polyp stage. The planula develops into a juvenile. Some jellyfish grow polyps inside the gonads in order to produce mature offspring ready for life in the ocean over time.

Vegetative propagation

Let's look at how jellyfish of the Hydrozoa class live and reproduce. Representatives of hydroids reproduce asexually. These are small animals, the size of which does not exceed three centimeters. Hydroid jellyfish consist of a bell-shaped dome, tentacles and oral proboscis.

Reproduction occurs vegetatively. The parent individual is simply divided in half starting from the center of the dome.

It is known that if, as a result of injury, a piece of tissue comes off from a jellyfish, it can take shape and develop into an independent individual. The damaged area quickly regenerates.

Phenomenal survivability

When answering the question of how long jellyfish live, scientists cite relatively small numbers. The average life expectancy is one to three years.

However, these creatures have phenomenal vitality and the highest reproduction rate. Numerous experiments have provided incredible data on the regenerative potential of jellyfish: if an individual is divided in two, both halves will quickly recover, survive, retain hunting skills and the ability to reproduce.

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.

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.