Interesting facts about jellyfish. Jellyfish aurelia eared Yellow jellyfish

In the waters of the Black, Azov and Baltic seas there are many mysterious creatures, one of which is the aurelia jellyfish, nicknamed the long-eared one because of its four lobes located under a jelly-like dome and strikingly reminiscent of a hare's ears. It is not surprising that today this weightless marine inhabitant is of interest to many aquarists.

Jellyfish is an invertebrate animal

Lifestyle

Natural habitat of long-eared aurelias - coastal waters temperate and tropical zones. The most numerous colonies of jellyfish can be found in equatorial stripes close to the coast, where they often form dense clusters of quite a large extent.

Aurelias are characterized by a pelagic lifestyle. Speaking in simple language, they inhabit areas that are not in close proximity to the bottom. This marine inhabitant belongs to the eurybiont type of invertebrate animals, which means it can withstand significant temperature fluctuations environment and constant changes in the level of salt in the water, which explains its extremely wide distribution.

All scyphoid jellyfish, without exception, are poor swimmers. They only rise from the depths and sink again, freezing motionless for some time in the water column. After storms, the entire coastal zone is literally strewn with aurelias.

It is harmless to humans

Until recently, this type of jellyfish was considered harmless to humans. However, in the Gulf of Mexico, cases of people receiving severe burns from contact with long-eared aurelia have been recorded. In the Black Sea for a bathing person such the jellyfish does not pose a serious threat. Unless its stinging cells can provoke minor irritation, comparable to what remains after contact with nettles.

Morphological features

Externally, the long-eared aurelia resembles a transparent umbrella. The jellyfish does not have a hard skeleton. The body base, 98% liquid, is represented by a jelly-like dome covered with epidermal cells. The size of the sea dweller sometimes reaches 50 cm.

Along the edges of the body there is a huge number of thin tentacles hanging down, dotted with stinging cells - the main weapon of the jellyfish, with which it paralyzes small animals. The continuous contraction of the muscle fibers of the dome ensures its movement and creates a flow of water that directs plankton into the oral cavity.

There are several stages of jellyfish development

Along the edges of the umbrella there are complex sensory organs - rhopalia. With their help, the long-eared aurelia navigates in space and stays at a certain distance from the sea surface so that the raging waves do not damage its body.

In the central part of the lower side of the dome there is a mouth surrounded by two pairs of blades. Their size makes it easy to determine the sex of a jellyfish. The female has much larger blades - they contain chambers for the maturation of larvae. Through the mouth and pharynx, food enters the stomach, and then, due to the work of the flagellar epithelium, enters the radial canals. Undigested residues follow the same path in the opposite direction and are excreted.

Stages of development

The eared jellyfish is a dioecious coelenterate animal that gives birth only once in its entire life, after which it dies. An interesting fact is that Aurelias show a kind of care for their brood, which cannot be said about other representatives of scyphoid jellyfish. The life cycle of a marine animal consists of several stages:

A two-layer embryo developing in an egg.
Larva (planula).
Polyp.
Adult.

Adult – last stage

In a female suspended in the water, the oral lobes are lowered, so the eggs emerging from the mouth opening penetrate into special gutters, move along them and end up in pockets, where they are fertilized and further development. Gradually, the embryo becomes covered with cilia, which help it swim, and eventually transforms into a larva.

For some time it stays in the water column, and then sinks to the bottom and is fixed on it with the help of the front end. A mouth with tentacles emerges from the upper part of the body, and the larva turns into a polyp, visually resembling a hydra. At the next stage, its division occurs, which is provided by transverse constrictions that cut into the body. This is how young aurelia appear.

Breeding aurelia at home has its own nuances. Jellyfish require a special tank that provides a smooth circular flow, in which they will not be afraid of collisions with objects encountered on their way. This is extremely important point, since the delicate and soft body of the long-eared aurelia can easily be damaged even by a minor blow. Finally, you need to keep in mind that the aquarium must be spacious enough, otherwise the jellyfish will not be able to fully expand their body.

Jellyfish love algae

Jellyfish can be kept in conditions of minimal water filtration. To maintain its quality at the proper level, it is simply necessary to regularly change the contents of the aquarium. Jellyfish do not take root in water that contains a lot of organic matter and nitrogenous compounds. Aurelias do not like it when other stinging animals (for example, hydras) are introduced to them.

In terms of food, these creatures are completely unpretentious. Suitable for them:

phytoplankton;
seaweed;
finely chopped seafood.

However, specialized stores always have ready-made food available, designed specifically for such aquarium inhabitants. As practice shows, the Aurelia eared jellyfish does well in captivity. Some aquarists not only successfully keep them, but also breed them, observing all stages of development.

In this video you will learn more about jellyfish:

Jellyfish are very common and the most amazing view living creatures inhabiting the seas and oceans. You can admire them endlessly. What types of jellyfish are there, where they live, what they look like, read in this article.

General information about jellyfish

They belong to the coelenterates and are part of their life cycle, which has two stages: asexual and sexual. Adult jellyfish are dioecious and reproduce sexually. The role of the male is to sweep reproductive products into the water, which can immediately enter the corresponding organs of the female or be fertilized directly in the water. It depends on the type of jellyfish. The emerging larvae are called planulae.

They have the ability to exhibit phototaxis, that is, they move towards a light source. Obviously, they need to stay in the water for some time, and not immediately fall to the bottom. The freely mobile life of planulas does not last long, about a week. After this, they begin to settle to the very bottom, where they attach to the substrate. Here they are transformed into a polyp or scyphistoma, the reproduction of which occurs by budding.

This is called asexual reproduction, which can continue indefinitely until conditions are favorable for the formation of jellyfish. Gradually, the body of the polyp acquires transverse constrictions, then the process of strobilation occurs and the formation of young disc jellyfish - ethers.

They are most of the plankton. Subsequently, they mature and become adult jellyfish. Thus, for asexual reproduction - budding, the water temperature may be low. But, having overcome a certain temperature barrier, dioecious jellyfish are formed.

Class of hydroid jellyfish

Coelenterates include solitary or colonial aquatic inhabitants. Almost all of them are predators. Their food is plankton, larvae and fry of fish. There are ten thousand species of coelenterate jellyfish. They are divided into classes: hydroid, scyphoid, and the first two classes are usually combined into a subspecies of jellyfish.

Hydroid coelenterate jellyfish are characteristic representatives of freshwater polyps. Their place habitual habitat are lakes, ponds and rivers. The body has a cylindrical shape and the sole is attached to the substrate. The opposite end is crowned with a mouth with tentacles located around it. Fertilization occurs inside the body. If a hydra is cut into many pieces or turned out the other way, it will continue to grow and live. The length of its green or brown body reaches one centimeter. Hydra does not live long, only one year.

They are free-swimming and have different sizes. The size of some species is only a few millimeters, while others are two to three meters. An example is cyanea. Its tentacles can stretch up to twenty meters in length. The polyp is poorly developed or completely absent. The intestinal cavity is divided into chambers by partitions.

Scyphoid jellyfish can live up to several months. About two hundred species live in temperate and tropical waters World ocean. There are jellyfish that people eat. These are cornerota and aurelia, they are salted. Many species of scyphoid jellyfish cause burns and reddening of the body if touched. For example, chirodrofus even causes fatal burns in humans.

Jellyfish Aurelia eared

There are different types jellyfish A photo of one of them is presented to your attention. This is a scyphoid eared one. Her breathing is carried out throughout her transparent and gelatinous body, in which there are twenty-four eyes. Sensitive bodies called rhopalia are located along the entire perimeter of the body. They perceive impulses from the environment. It could be the light.

The jellyfish eats food and removes its remains from the body through the mouth opening, around which four oral lobes are located. They contain a burning substance that serves as a defense for the jellyfish and helps it obtain food. Aurelia is not adapted to life on land, as it consists of water.

Medusa Cornerot

It is popularly called the "Umbrella". The habitat of the jellyfish is Black, Azov and Baltic Sea. Cornerot fascinates with its beauty. The body of the jellyfish is translucent with a blue or purple edging, reminiscent of a lampshade or umbrella. Its peculiarity is that most often it swims on its side and has no mouth. Instead, small diameter holes are scattered on the blades through which it feeds. Cornerot lives and reproduces in the water column on great depth. If you accidentally come into contact with a jellyfish, you can get burned.

Unusual habitat

Scientists from Israel have proven that freshwater jellyfish are found in lakes in the Golan Heights. The children saw them for the first time. Then individual specimens were placed in a bottle and given to Professor Gofen. He carefully studied them in the laboratory. It turned out that this was a local colony of one of the freshwater hydroid jellyfish, which were described in England back in 1880. Then these jellyfish were discovered in a pool of water tropical plants. According to the professor, the jellyfish's mouth is surrounded by numerous stinging cells, with which it catches planktonic organisms. These jellyfish are not dangerous to humans.

Freshwater jellyfish

These coelenterate inhabitants inhabit the waters only of seas and oceans. But, there is one exception called the Amazon freshwater jellyfish. Its habitat is South America, namely the swimming pool large river on the mainland - the Amazon. Hence the name. Today, this species has spread everywhere, quite by accident, during the transportation of fish from the seas and oceans. The jellyfish is very small, reaching only two centimeters in diameter. Now it inhabits slow, calm and stagnant waters, dams, and canals. The food is zooplankton.

The largest jellyfish

Is it cyanea or lion's mane. There are different types of jellyfish in nature, but this one is special. After all, that’s what he described Conan Doyle in your story. This is a very large jellyfish, the umbrella of which reaches two meters in diameter, and the tentacles reach twenty. They look like a raspberry-red tangled ball.

In the central part the umbrella is yellowish, and its edges are dark red. The lower part of the dome is endowed with a mouth opening, around which there are sixteen large folded oral lobes. They hang down like curtains. Cyanea moves very slowly, mainly on the surface of the water. It is an active predator, feeding on planktonic organisms and small jellyfish. Habitat: cold waters. Occurs frequently, but is not dangerous. The resulting burns are not fatal, but can cause painful redness.

Jellyfish "Purple Sting"

This species is distributed in the World Ocean with warm and temperate waters: it is found in the Mediterranean and Atlantic Pacific Oceans. These types of jellyfish usually live far from the coast. But sometimes they can form schools in coastal waters, and can be found in large numbers on the beaches. Jellyfish are not only They are golden yellow or yellow-brown, depending on their habitat.

Jellyfish Compass

These types of jellyfish chose coastal waters as their place of residence. Mediterranean Sea and one of the oceans - the Atlantic. They live off the coast of Turkey and the United Kingdom. These are quite large jellyfish, their diameter reaches thirty centimeters. They have twenty-four tentacles, which are arranged in groups of three each. The body color is yellowish-white with a brown tint, and its shape resembles a saucer-bell, which has thirty-two lobes, which are colored brown at the edges.

The upper surface of the bell has sixteen brown V-shaped rays. The lower part of the bell is the location of the mouth opening, surrounded by four tentacles. These Their poison is potent and often leads to the formation of wounds that are very painful and take a long time to heal.

Among the most unusual animals on Earth, jellyfish are also among the oldest, with an evolutionary history dating back hundreds of millions of years. In this article, we reveal 10 basic facts about jellyfish, from how these invertebrates move through deep water to how they sting their prey.

1. Jellyfish are classified as cnidarians or cnidarians.

Named after the Greek word for "sea nettle," cnidarians are marine animals characterized by a jelly-like body structure, radial symmetry, and stinging "cnidocyte" cells on their tentacles that literally explode when capturing prey. There are about 10,000 species of cnidarians, about half of which belong to the class coral polyps, and the other half includes hydroids, scyphoids, and box jellyfish (the group of animals that most people call jellyfish).

Cnidarians are among the most ancient animals on earth; Their fossil roots go back almost 600 million years!

2. There are four main classes of jellyfish

Scyphoid and box jellyfish are two classes of cnidarians that include classical jellyfish; The main difference between the two is that box jellyfish are cube-shaped and bell-shaped, and are slightly faster than scyphoid jellyfish. There are also hydroids (most species of which do not go through the polyp stage) and staurozoa - a class of jellyfish that lead a sedentary lifestyle, attaching to a hard surface.

All four classes of jellyfish: scyphoid, box jellyfish, hydroid and staurozoa belong to the subphylum of cnidarians - medusozoa.

3. Jellyfish are some of the simplest animals in the world

What can you say about animals without central nervous, cardiovascular and respiratory systems? Compared to animals, jellyfish are extremely simple organisms, characterized mainly by wavy bells (which contain the stomach) and tentacles with many stinging cells. Their almost transparent bodies consist of only three layers of outer epidermis, middle mesoglea, and inner gastrodermis and water making up 95-98% of the total volume, compared to 60% in the average human.

4. Jellyfish are formed from polyps

Like many animals, life cycle Jellyfish breeding begins with eggs, which are fertilized by males. After this, things get a little more complicated: what emerges from the egg is a free-swimming planula (larva) that looks like a giant slipper ciliate. The planula then attaches itself to a solid surface (sea floor or rocks) and develops into a polyp resembling miniature corals or sea anemones. Finally, after several months or even years, the polyp detaches and develops into an ether, which grows into an adult jellyfish.

5. Some jellyfish have eyes

Cobojellyfish have a couple of dozen light-sensitive cells in the form of an eyespot, but unlike other marine jellyfish, some of their eyes have a cornea, lenses and retina. These compound eyes are arranged in pairs around the circumference of the bell (one pointing upward and the other downward, providing a 360-degree view).

The eyes are used to search for prey and protect themselves from predators, but their main function is the correct orientation of jellyfish in the water column.

6. Jellyfish have a unique way of delivering venom.

As a rule, they release their venom during a bite, but not jellyfish (and other coelenterates), which in the process of evolution have developed specialized organs called nematocysts. When the jellyfish's tentacles are stimulated, enormous internal pressure is created in the stinging cells (about 2,000 pounds per square inch) and they literally explode, piercing the skin of the unfortunate victim to deliver thousands of tiny doses of venom. The nematocysts are so powerful that they can be activated even when the jellyfish is washed ashore or dies.

7. The sea wasp is the most dangerous jellyfish

Most people are afraid poisonous spiders and rattlesnakes, but the most dangerous animal on the planet for humans may be a species of jellyfish - the sea wasp ( Chironex fleckeri). With a bell the size of a basketball and tentacles up to 3 meters long, the sea wasp prowls the waters off Australia and South-East Asia, and at least 60 people lost their lives because of it in the last century.

Slight touch of tentacles sea wasp causes excruciating pain, and closer contact with these jellyfish can kill an adult in a couple of minutes.

8. The movement of jellyfish resembles the operation of a jet engine

Jellyfish are equipped with hydrostatic skeletons, invented by evolution hundreds of millions of years ago. Essentially, the jellyfish's bell is a fluid-filled cavity surrounded by circular muscles that spray water in the opposite direction of the movement.

The hydrostatic skeleton is also found in starfish, worms and other invertebrates. Jellyfish can move along with ocean currents, thereby saving themselves from unnecessary effort.

9. One type of jellyfish may be immortal

Like most invertebrate animals, jellyfish have a short lifespan: some small species live only hours, while the largest species, such as the lion's mane jellyfish, can live for several years. Controversially, some scientists claim that jellyfish species Turritopsis dornii immortal: adults are able to return to the polyp stage (see point 4), and thus an endless life cycle is theoretically possible.

Unfortunately, this behavior has only been observed in laboratory conditions, and Turritopsis dornii can easily die in many other ways (such as becoming dinner for predators or being washed up on a beach).

10. A group of jellyfish is called a “swarm”

Remember the scene from the cartoon Finding Nemo, where Marlon and Dory have to navigate their way through a huge cluster of jellyfish? Scientifically, a group of jellyfish consisting of hundreds or even thousands of individual individuals is called a "swarm". Marine biologists have noticed that large concentrations of jellyfish are being observed more and more often, and can serve as an indicator of sea pollution or global warming. Swarms of jellyfish usually form in warm water jellyfish are able to thrive in anoxic marine conditions that are unsuitable for other invertebrates of their size.

Jellyfish aurelia is a common jellyfish that everyone who has been to the sea has seen. Aurelia jellyfish or eared jellyfish live in the Black, Baltic, Barents, Japanese, Bering and White seas. In addition, aurelia is found in tropical seas and Arctic zones.

These jellyfish swim poorly; they can only rise from the depths and sink, hovering motionless while contracting their umbrellas. After a storm, these jellyfish are found in huge numbers on the shore.

The umbrella of Aurelia has a flat shape and is 40 centimeters in diameter. The umbrella is completely transparent because it is formed from a non-cellular substance, which is almost 98% water. In this regard, the weight of a jellyfish is close to the weight of water, which makes the swimming process easier. Small but very mobile tentacles run along the edge of the umbrella. Located on the tentacles big number stinging cells.

In the middle of the bell there is a quadrangular mouth, 4 scalloped oral lobes hang from it, which also actively move. Jellyfish use stinging cells to kill prey. Jellyfish mainly feed on small crustaceans. The oral lobes contract and pull prey towards the mouth.

Aurelias are dioecious jellyfish.

Reproduction of aurelia

Aurelias are dioecious creatures. The body of males contains milky-white testes, clearly visible and shaped like half rings. Females have purple and red ovaries, which are visible through the bell. The gender of a jellyfish can be easily determined by the color of these glands.

Reproduction in Aurelia jellyfish occurs only once, after which they die. These jellyfish, unlike most of their relatives, take care of their offspring. When a jellyfish hangs in the water, its mouth lobes are lowered down, so the eggs that come out of the mouth opening fall into the gutters, move along them and penetrate into the pockets, where they are fertilized and develop. After fertilization, the egg begins to divide, first in two, then each half divides in two again, and so on. Thus, a multicellular single-layer ball is obtained. A certain number of cells are immersed inside, just like a rubber ball is squashed, this is how a two-layer embryo is obtained.

The cells of the embryo are covered on top with a large number of cilia, with the help of which the embryo swims. From this time on, the embryo transforms into a larva called a planula. The larva swims in the water for some time, and then sinks to the bottom and attaches itself to it with the help of its anterior end. Then a mouth with a crown of tentacles breaks out on the back, upper part of the body. Thus, the planula is transformed into a polyp, which is similar in appearance to hydra.

After some time, the polyp divides using transverse constrictions. The constrictions cut into the body of the polyp, and it takes on a resemblance to a stack of plates. These discs are young jellyfish that are beginning an independent life. That is, in this way, asexual reproduction of polyps occurs; they cannot reproduce sexually. Only jellyfish can reproduce in this way.

Jellyfish food

In Japan and China, Aurelia jellyfish are used as food; in these countries, fishing for these creatures is organized. Large aurelias are used for pickling. The mouth blades of the caught jellyfish are separated, and the umbrella is thoroughly washed until the digestive canals are cleaned. Only the non-cellular substance of the umbrella can be processed. The Chinese call jellyfish meat “crystal”. Jellyfish are eaten boiled and fried with a variety of seasonings, and salted jellyfish are used in solariums.

For humans, the stinging cells of aurelia jellyfish are safe, unlike the corner jellyfish that live in Cherny and Seas of Azov. Cornerotes do not have tentacles; they grab prey with their branched mouth cavities, the edges of which are similar to root outgrowths. These outgrowths are strewn with stinging cells that contain the toxic substance rhizostomin. This substance causes severe burns to humans. Cornerotes differ from eared jellyfish by the presence of a border along the edge of the umbrella that is bright purple or blue color. Large specimens of cornetroots reach a diameter of 50 centimeters.

Cyanea

The Barents and White Seas are home to a cold-water giant, the cyanea; the umbrella of this huge jellyfish can reach a diameter of 2 meters. The central part of the umbrella is yellowish and the edges are dark red. These jellyfish shimmer with a faint greenish color. The mouth opening is surrounded by sixteen wide oral lobes, crimson-red in color. Cyaneas have long tentacles up to 20-40 meters, light pink in color. When the cyanea spreads its tentacles, the trapping network of them covers 150 square meters.

Under the bell of these jellyfishes, haddocks, cod fry and other fish calmly swim, which under this dome find shelter and food - a variety of microorganisms living on the body of the jellyfish.

If a person touches the tentacles of cyanea, he will experience pain that goes away only after 40 minutes, in addition, quite serious lesions can occur on the skin.

Equorea jellyfish

Among the jellyfish there are also luminous representatives. If it accumulates in the water a large number of jellyfish, in the dark, green or blue balls seem to light up from time to time.

On the Pacific coast of Russia, as well as on Atlantic coast Equorean jellyfish live in the USA. The glow of these jellyfish makes the waves seem to be on fire. And in tropical and moderately cold waters, luminous pelagia of the nightglow live.

Under the “dome” of a jellyfish, fry of various fish can live.

Between jellyfish and small fish there is an interesting relationship. When immersed in water, you can see small horse mackerel swimming next to the cornet jellyfish. When divers approach the fish, they instantly hide under the dome of the jellyfish, through which their bodies can be distinguished. The fry do not touch the stinging cells located on the tentacles of jellyfish, so jellyfish for them are a reliable shelter from numerous predators. But some careless fry nevertheless become victims of stinging cells, in which case the jellyfish calmly digests them.

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

This form, often found in huge masses, is well known to all explorers of our seas; magnitude eared jellyfish varies between 1 and 40 cm in diameter, but specimens of 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 by the following characteristics: a tall, cubic umbrella, the edge of which, reminiscent of the swimming edge of hydroid jellyfish, is in the form of a horizontally tense membrane or hanging downwards; on this edge there are 4 sensitive flasks, with an eye and an organ of hearing on each.

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

Sea wasp jellyfish

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

However, there are survivors - people with strong hearts. There is an antidote against 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 northern seas; this form can move from place to place with the help of its tentacles, which is also helped by the jellyfish leg, which has the ability to arbitrarily attach or separate from underwater objects.

In the northern European, as well as in the Black and Baltic seas, the largest (up to 7 cm) and long-known species of the described genus is found - the common lanternfly (L. quadri-cornis): this gray, green, brown-yellow or, finally, , the black-brown jellyfish willingly settles on red algae. It is also known on the shores of Greenland and found in America, off its northeastern shores.
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