Jellyfish aurelia lifespan. Interesting facts about jellyfish

The sea jellyfish, which is called a wasp, belongs to the category of box jellyfish, a type of cnidarians. She is a representative of the exceptional animals of the marine world and is able to live only in the salt water of the seas and oceans.

Invisible danger

The sea wasp jellyfish is considered the most poisonous jellyfish in the world. The toxin that is released from its tentacles depresses nervous system, causes severe burns and unbearable pain. The result is a heart attack that can lead to cardiac arrest. Timely rendered health care in some cases it can save a person’s life. However, there are known cases of death within a very short period of time after an encounter with a poisonous monster. Even a dead sea wasp (photo below) is a source of increased danger. The poison-toxin disintegrates only a week after the death of the jellyfish, so it is strictly forbidden to touch it.

Unfortunately, jellyfish of this type are also found in beach resorts and diving areas. Another danger of encountering a sea wasp is that it is almost invisible. Therefore, precautions should not be neglected.

Habitat

There is a jellyfish in Pacific Ocean its Indo-western part and in South-East Asia. Most often, the sea wasp is found near the coast of northern Australia, where there are many corals and shallow sea depths. summer months from November to March. Jellyfish inhabit coastal zones at a respectful distance from the shores, but at strong excitement sea they can be washed ashore.

Appearance

The sea wasp is the largest representative of its class. The body of a jellyfish is a transparent dome consisting of 95% water. Its shape is similar to a rounded cube, hence the name box jellyfish. The size of the dome is 20-45 cm, in size it can be compared with a basketball ball. It has a pale blue color and is completely invisible in the water.

The animal has 24 eyes, which are located in three pairs in each corner of the dome. Two pairs of eyes serve to receive images, and one only reacts to light. Scientists cannot explain the presence of so many eyes in a jellyfish, because the information received from what it sees has nowhere to be transmitted; it does not have a brain.

In addition to the organs of vision, there are 60 tentacles - four bundles of 15 pieces each. The probes, 15 cm long and 5 mm thick, stretch up to three meters when hunting for prey. Each tentacle is covered with stinging cells containing deadly poison.

The sea wasp does not have a skeleton; it is replaced by two nervous systems, one of which receives and processes information received from the organs of vision, and the other controls the movement of muscles along the border of the dome, which function simultaneously and harmoniously.

Nutrition

Sea wasps feed in coastal waters small fish and various bottom organisms, but the most favorite delicacy is shrimp. When going out to fish, they extend their tentacles and freeze in place. The jellyfish encloses the stalked victim in probes, pierces the skin, injects poison, kills and swallows. In appearance, its bite resembles a wasp, only the venom is much more toxic, incomparable even to the venom of a snake.

Reproduction

The sea wasp gives birth only once in its entire life, and then dies. Box jellyfish live for about 7 months and continue to grow throughout this period.

Sea wasps reproduce offspring in the same way as other individuals belonging to this species. They reproduce in summer period, gathering in large flocks and swimming closer to the shores. During this period of time, Australia is trying to close all beaches.

The male ejects a dose of sperm into the water while near the swimming female. The latter swallows it, fertilization occurs. Larvae develop inside the female, which after some time are released into the water and settle on the surface of the seabed. They stick to stones, shells, and driftwood, forming polyps.

As a result of budding, small jellyfish grow from polyps, which break off and begin an independent life. They immediately navigate the sea and feed on plankton on their own.

What do Australians call a sea wasp?

Due to its transparency, this small sea animal is almost invisible in the water. It is an active predator and poses a great danger to animals and humans. This animal swims well and maneuvers well among algae and corals, moving at speeds of up to six meters per minute. During the day it is most often at the bottom, and with the onset of evening it floats to the upper layers of the water. The speed at which a jellyfish attacks its prey is very high.

And the poison contained in the tentacles is so poisonous that when stung, any creature instantly dies. Moreover, it stings several times in a row, bringing the concentration of poison to a lethal level. Australian sea wasp - that’s what this jellyfish is called - it poses a danger to all living organisms, with the exception of the poison of these predators does not affect them, and turtles eat box jellyfish with appetite.

Consequences of an encounter with a sea wasp

Although box jellyfish are extremely dangerous to human life, they do not attack them themselves; on the contrary, they tend to swim to the side. It can sting a person purely by accident. Often the victims are scuba divers who are not protected by special suits.

When the skin comes into contact with the tentacle, terrible pain, severe redness and swelling appear. A person's heart most often stops and he drowns. Some managed to get ashore, but paralysis set in respiratory system, and the man died. After autopsies, it was discovered that the victims' respiratory organs were filled with mucus, while others died from cerebral hemorrhage. There were cases where a person did not die immediately, but no one remained alive.

Protecting the lives of vacationers

During the jellyfish migration season, net barriers are installed on beaches to prevent them from entering the swimming area. Despite this, small specimens penetrate through the mesh cells, so the beach administration warns vacationers about the danger and strictly prohibits them from entering the water.

This warning should not be ignored. After all, the fast-acting poison of the sea wasp leaves no hope of salvation. The only way to help is to administer an antidote - antitoxic serum and urgently hospitalize the victim. But this does not give any guarantee of saving life.

It is known that jellyfish appeared more than 600 million years ago, much earlier than dinosaurs, crocodiles and sharks.
Jellyfish and polyps are different stages of the life period of the same creature.
A sea wasp is a jellyfish that breathes through its entire dome and stings like a wasp.
The absence of a brain does not prevent them from perceiving nervous stimulation from the organs of touch and vision.
They have two nervous systems.

Jellyfish are able to move underwater by sucking in and expelling water by contracting their parasol muscles, but they mostly drift thanks to the current. Scientists believe that they belong to plankton.

Jellyfish are a class of multicellular invertebrates that hunt and kill their victims using tentacles.

These beautiful exotic creatures can only survive in salt water, therefore, their habitat is oceans, seas and in some cases cut off from " big water» lagoons of coral islands. Some of the species love cool water, others love warm water, and still others live only upper layers, and the fourth - only at the bottom.

It is interesting that the representatives of the animal world in question belong to the same group as... corals. Both of these classes of creatures belong to the coelenterates.

Jellyfish are loners. They do not transmit signals to their “relatives” in any way, even if they are swept into a large pile by the current.

They were named in the mid-18th century by Carl Linnaeus, who noticed their similarity to a head. famous character ancient Greek myths - Medusa the Gorgon.

This is an amazing animal 98% consists of water, therefore, its body is almost transparent, similar to a dome, umbrella or disk made of jelly. And the “dome” moves due to muscle contraction.

Tentacles

There are tentacles along the edges of the creature. They are very different different types: short and thick are possible, long and thin are possible; their number ranges from four to four hundred (the number of tentacles is always a multiple of four, because these animals have an inherent radial symmetry).

Tentacles are built from containing toxic substances stinging cells and are needed for movement, hunting and holding prey. Fun fact: even a dead jellyfish can bite for about two weeks. Certain types of jellyfish are extremely dangerous for humans. For example, an animal called the Sea Wasp can poison six dozen people in a couple of minutes.

From above the animal’s body is smooth and dome-shaped, and from below it looks like an empty bag. In the middle below is the mouth opening. It can also be different: in some individuals it looks like a pipe, in others it looks like a club, in others it is wide. Undigested food remains are also removed through the mouth.

Growth and development

Jellyfish increase in size throughout their lives, and their final size depends on the species. Yes - tiny, not longer than a pair millimeters, but there are giants larger than forty meters(this is the length of the tentacles). Cyanea is the largest representative and lives in the North Atlantic.

These inhabitants of the sea no brain and sense organs, but there are light-sensitive cells that help them distinguish between darkness and light (they do not see objects). Some specimens can glow in the dark. Animals living in the depths are usually red, and those living near the surface of the water are blue.

Internal structure

The internal structure of animals is very simple. They consist of two layers:

The outer ectoderm, which acts as a kind of skin and muscle, contains the rudiments of nerves and germ cells.
Internal endoderm, which only digests food.

Jellyfish have an amazing ability to regenerate: even if you cut an animal into halves, two similar individuals will grow from them.

Classification

Hydroids or Hydrozoa(organisms that live only in waters that constantly contain absorbed oxygen). Relatively small (1 to 3 cm), transparent animals; four tentacles, a long mouth resembling a tube. The most famous creature of this class is Turritopsis nutricula. This the only thing known to science biologically immortal being. Having aged, it sits on the seabed and transforms into a polyp, from which new individuals then grow. Another very dangerous animal called the Cross belongs to this class. It is tiny (the largest individuals reach about 4 cm), but if it bites a person, the victim will have serious and very long-term health problems.

Box jellyfish (Cubozoa). This class is so named because their umbrella is not oval, but cubic. They differ from other representatives by their developed nervous system. They can swim at speeds of up to six meters per minute and adjust direction with ease. However, they are also the most dangerous for people: some individuals can even kill a careless swimmer. The most poisonous representative of cnidarians on the planet, the Sea Wasp, is a representative of this class.

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

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

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

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

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

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

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

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

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

How does a jellyfish reproduce?

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

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

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

Hydroid jellyfish and polyps

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

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

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

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

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

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

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

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

Classification

Akalephs

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

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

Reproduction of Akalephs

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

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

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

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

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

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

Rootmouth jellyfish

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

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

Cotylorhiza

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

Disc jellyfish

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

Cuboid jellyfish

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

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

Sea wasp jellyfish

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

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

Goblet jellyfish

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

Lantern

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

In the northern European, as well as in the Black and Baltic seas, the largest (up to 7 cm) is found and a long time ago known species of the described genus is the common lanternfly (L. quadri-cornis): this gray, green, brown-yellow or, finally, black-brown jellyfish willingly settles on red algae. It is also known on the shores of Greenland and found in America, off its northeastern shores.
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Jellyfish aurelia is a species sea creatures, which is very interesting and mysterious. Therefore, they are often kept in aquariums. This article contains information about who the aurelia jellyfish is: description, features of the content, reproduction of this species.

general description

In aurelia, the umbrella is flat and can reach 40 cm in diameter. Since it is based on a non-cellular substance (consists of 98% water), it is completely transparent. This quality also means that the weight of these animals is close to the weight of water, which makes swimming much easier.

It should be noted that the aurelia jellyfish has a very interesting structure. So, along the edge of her umbrella there are tentacles - small, but mobile. They are packed very tightly huge number stinging cells.

This jellyfish has a quadrangular mouth with 4 movable blades at the edges. Their contraction (they are covered) also makes it possible to pull the prey to the mouth and securely capture it.

The issues of keeping jellyfish are somewhat specific. Initially, it's about aquariums. For jellyfish, special containers are needed to ensure a smooth circular flow. This allows animals to move calmly without fear of any collisions. This is important because the aurelia, or eared jellyfish, has a very delicate and soft body that is easily damaged.

It is necessary to ensure the correct flow speed, which should allow animals to “soar” without problems in the water column. Only in this case there should be no danger of harm to their bodies.

The specificity also lies in the fact that for jellyfish in aquariums the use of aeration is absolutely excluded. This is explained by the fact that air bubbles can end up under the dome of the animal, get stuck there and then pierce it, which is very dangerous and can lead to the death of the jellyfish.

They don’t need any special lighting; basically, simple lighting is enough.

Also note that there is no need to filter the water. As a rule, it is enough just to regularly change the water so that its quality always remains at the proper level. If there is no desire to constantly update the water, you can also install a life support system. It is important to take proper care to protect the animals. Because they can be pulled into intake devices.

In addition, it must be taken into account that the aurelia jellyfish must live in a fairly spacious aquarium, since it needs the ability to freely extend its tentacles to their full length.

Feeding

How are jellyfish fed? They are perfectly suited for a mixture that consists of brine shrimp, phytoplankton, highly crushed crustaceans and seafood. Although there are currently various ready-made foods on sale that Aurelia (eared jellyfish) can also eat. But there is one peculiarity. If the animals don’t like the food at all, they can start eating the rest of the jellyfish.

Reproduction

Jellyfish aurelia is dioecious. Thus, the testes of males have a milky white color, they are clearly visible: they are small half rings in the body of the animal. Females have violet or red ovaries, which are also visible in the light. Therefore, by the color you can understand what gender the jellyfish is. Aurelians reproduce only once during their life, and then die. Their main distinguishing feature is considered to be the manifestation of care for their own offspring (which is not characteristic of other species).

It is worth noting that fertilization of eggs, as well as their further development occurs in special pockets. Eggs enter them through gutters from the mouth. After fertilization, the egg divides into 2 parts, each of which is subsequently also divided in half, and so on. Due to this, a single-layer multicellular ball is formed.

Some of the cells of this ball get inside, which can be compared to pressing a rubber ball. Because of this, a two-layer embryo appears.

He can swim thanks to a large number cilia, which are located on its outer part. The embryo then becomes a larva, which is called a planula. She just floats for a while and then falls to the bottom. It is attached at the front end to the bottom. Quite quickly, the rear end of the planula is transformed: a mouth appears in this place, and tentacles are also formed. And it becomes a polyp, from which small jellyfish are subsequently formed.

Jellyfish aurelia is often used in medicine. Laxatives and diuretics were produced from it in the Middle Ages. And today, from the poison contained in the tentacles of animals, drugs are produced to regulate blood pressure and treat various pulmonary diseases.

Farmers in the Caribbean use physalia poison as a poison for rodents.

Jellyfish allow you to effectively cope with stress. They are bred in special aquariums in Japan. The leisurely, smooth movements of animals calm people, but keeping them is very expensive and troublesome.

Luminophores isolated from jellyfish are used for biochemical analysis. Their genes were transplanted into various animals, for example, rodents, due to which biologists were able to see with their own eyes previously inaccessible processes. Because of this action, the rodents began to grow green hair.

Some jellyfish are caught off the coast of China, where their tentacles are removed, and the carcasses are kept in a marinade, due to which the animal turns into a cake of thin, delicate, translucent cartilage. In the form of such cakes, animals are taken to Japan, where they are carefully selected for quality, color and size and used in cooking. So, for one salad, the jellyfish is cut into small strips 3 mm wide, they are mixed with herbs, stewed vegetables, and then poured over with sauce.

Robot jellyfish also appeared there. They, unlike real animals, not only swim beautifully and slowly, but can also “dance” to music if the owner wishes.

Conclusion

Despite the fact that the aurelia jellyfish is very common, it cannot be called completely ordinary. In principle, these are very curious creatures, therefore, observing them and keeping them will be very exciting.

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

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

Who are jellyfish

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

These amazing animals live only in salt water, and therefore they can be found in all oceans and seas of our planet (except internal ones), sometimes in closed lagoons or lakes with salt water on coral islands.

Among the representatives of this class there are both heat-loving animals and those that prefer cold waters, species that live only near the surface of the water, and those that live only on the bottom of the ocean.

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

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, while in species living on great depth, the light is red, and for those that live closer to the surface it is 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 skin and muscles. The rudiments of the nervous system and germ cells are also located here;
internal (endoderm) - performs only one function: digests food.

Travel methods

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

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

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

Regeneration

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

Reproduction

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

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

In these animals, the sex cells mature in the gonads;
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;
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;
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

Exist the following types 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 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. This giant jellyfish At about 37 meters long, it 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 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 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 individuals in that they completely lack dark spots, there are no stinging tentacles, as well as 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 on its body green algae, 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 mainly 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 Earth.