Jellyfish are animals that everyone associates with something shapeless and infinitely primitive, but their lifestyle and physiology are not as simple as it seems at first glance. The word "jellyfish" usually means animals from the Scyphoid class and representatives of the Trachilid order from the Hydroid class of the intestinal type. At the same time, in the scientific community, this word has a broader interpretation - zoologists use this term to designate any mobile forms of intestinal animals. Thus, jellyfish are closely related to mobile types of intestinal (siphonophores, sea boats) and sessile ones - corals, sea anemones, hydras. In total, there are over 200 species of jellyfish in the world.
Scyphoid jellyfish rhizostoma, or cornerot (Rhizostoma pulmo).
Because of their primitiveness, jellyfish are characterized by the uniformity of physiology and internal structure, but at the same time they are distinguished by an amazing variety of colors and appearance unexpected for such simple animals. One of the main hallmarks jellyfish is radial symmetry. This type of symmetry is characteristic of some marine animals, but in general it is not so common in the animal world. Due to radial symmetry, the number of paired organs in the body of jellyfish is always a multiple of 4.
The umbrella of this jellyfish is divided into blades, the number of which is always a multiple of 4.
Jellyfish are so primitive that there are no differentiated organs in their body, and the tissues of the body consist of only two layers: the outer (ectoderm) and the inner (endoderm), connected by a sticky substance - mesoglea. However, the cells of these layers are specialized to perform different functions. For example, ectoderm cells perform an integumentary function (skin analog), motor (muscle analog), here are special sensitive cells, which are the rudiments of the nervous system and special germ cells that form reproductive organs in adult jellyfish. But the cells of the endoderm are only engaged in the digestion of food, for this they secrete enzymes that digest the prey.
Due to the highly developed colorless mesoglea, the body of the flower cap jellyfish (Olindias formosa) looks almost transparent.
The body of jellyfish is shaped like an umbrella, disk or dome. The upper part of the body (it can be called external) is smooth and more or less convex, and the lower (it can be called internal) shape resembles a bag. The inner cavity of this sac is both an engine and a stomach. In the middle of the lower part of the dome, the jellyfish have a mouth. Its structure is very different from different types: in some jellyfish, the mouth has the shape of an elongated proboscis or tube, sometimes very long, in others, short and wide oral lobes are located on the sides of the mouth, in others, instead of lobes, there are short club-shaped oral tentacles.
This chic crown is formed by the mouth tentacles of the cotylorhiza tuberculata jellyfish.
Trapping tentacles are located along the edges of the umbrella, in some species they can be relatively short and dense, in others - thin, long, filiform. The number of tentacles can vary from four to several hundred.
The tentacles of the eared jellyfish (Aurelia aurita) are relatively short and very thin.
In some species of jellyfish, these tentacles are modified and turned into organs of balance. Such organs have the form of a tube-stalk, at the end of which there is a bag or vial with a calcareous stone - statolith. When the jellyfish changes direction, the statolith shifts and affects the sensitive hairs, from which the signal is transmitted to the nervous system. The nervous system of jellyfish is extremely primitive, these animals have neither a brain nor sensory organs, but there are groups of light-sensitive cells - eyes, so jellyfish distinguish between light and dark, but they, of course, cannot see objects.
And this jellyfish has thick and long trapping tentacles combined with long and fringed mouthparts.
However, there is one group of jellyfish that completely refutes the usual ideas about these animals - these are stauromedusas. The fact is that stauromedusas do not move at all - this is a rare example of sedentary animals. Sitting jellyfish are radically different in their structure from free-swimming species, at first glance the relationship between these groups of jellyfish seems incredible.
Sedentary jellyfish Cassiopeia (Cassiopea andromeda).
The body of stauromedusa resembles a bowl on a long leg. With this leg, the jellyfish is attached to the ground or algae. The mouth is located in the middle of the bowl, and the edges of the bowl are extended into eight so-called arms. At the end of each "arm" is a bunch of short tentacles, similar to a dandelion.
Sedentary alfalfa jellyfish (Lucernaria bathyphila).
Despite the fact that stauromedusas lead a sedentary lifestyle, if necessary, they can move around. To do this, the jellyfish bends its leg in such a way that its cup leans towards the ground, and then stands on its “hands”, as if performing a headstand, after which the leg comes off and moves a few centimeters, standing on the leg, the jellyfish straightens up. Such movements are carried out very slowly, during the day the jellyfish takes several steps.
This alfalfa shows off the muscular stalk that anchors it to the bottom.
The sizes of jellyfish range from 1 cm to 2 m in diameter, and the length of the tentacles can reach 35 m! The weight of such giants can reach up to a ton!
This is the largest jellyfish in the world - cyanide, or lion's mane(Cyanea capillata), it is her long tentacles that can reach 35 m in length!
Since the tissues of jellyfish are poorly differentiated, their cells do not have color. In most jellyfish, the body is transparent or with a pale milky, bluish, yellowish tint. This feature is reflected in the English name of jellyfish - "jelly fish". Indeed, devoid of a skeleton, soft, saturated with moisture (the water content in the body of jellyfish is 98%!), The pale body of jellyfish resembles jelly.
In water, their body retains elasticity due to saturation with moisture, but a jellyfish thrown onto land instantly falls and dries up; on land, jellyfish are not able to make even the slightest movement.
However, not all jellyfish are so nondescript. Among them there are really beautiful views, painted in bright colors - red, pink, purple, yellow. Only green jellyfish do not exist. In some species, the coloration has the appearance of a pattern in the form of small specks or stripes.
Amazing play of colors of scyphoid jellyfish.
But that's not all. Some types of jellyfish (pelagia nightlight, aequorea, ratkey and others) are able to glow in the dark. Interestingly, in deep-sea jellyfish, the emitted light is red, while those that swim close to the surface of the water are blue. This phenomenon is called bioluminescence and underlies the exciting natural phenomenon- night glow of the sea. The glow arises as a result of the decay of a special substance - luciferin, whose name is consonant with the name of the devil, obviously this phenomenon caused awe among the discoverers of bioluminescence. In fairness, it should be said that the glow of water is provided not only by jellyfish, but also by other marine organisms - small crustaceans (plankton), algae and even ... worms.
The deep-sea scyphoid atoll jellyfish (Atolla vanhoeffeni) is bright red in color and looks like an unearthly creature.
The range of jellyfish covers the entire World Ocean, they are found in all seas except inland ones. Jellyfish live only in salt water, occasionally they can be found in closed lagoons and brackish lakes of coral islands that once separated from the sea. The only one freshwater species- a tiny jellyfish kraspedakusta, which was discovered by accident in the pool ... of the London Botanical Society. Jellyfish got into the pool along with aquatic plants brought from the Amazon. Among the jellyfish you will not find pandemic species, that is, those that are found everywhere, usually each species of jellyfish occupies an area limited by any one sea, ocean or bay. Among jellyfish there are heat-loving and cold-water ones; species that prefer to stay near the surface and deep-sea. Deep-sea jellyfish almost never rise to the surface; they swim all their lives in the depths in pitch darkness. Those jellyfish that live near the surface of the sea make vertical migrations - during the day they plunge to great depths, and at night they rise to the surface. Such migrations are associated with the search for food. Also, jellyfish can migrate in a horizontal direction, although they are passive in nature, jellyfish are simply carried by the current over long distances. Jellyfish, being primitive animals, do not contact each other in any way, they can be classified as solitary animals. At the same time, in places rich in food, at the intersection of currents, jellyfish can form large clusters. Sometimes the number of jellyfish increases so much that they literally fill the water space.
Numerous jellyfish make vertical migration in the slightly saline Lake Medusa on about. Palau.
Jellyfish move rather slowly, largely using the auxiliary power of the currents. The movements are provided by thin muscle fibers in the umbrella: contracting, they seem to fold the dome of the jellyfish, while the water contained in the internal cavity (stomach) is pushed outward with force. Thus, a jet stream arises, which pushes the body of the jellyfish forward. Accordingly, jellyfish always move in the direction opposite to the mouth, but they can swim in different directions - horizontally, up and down (as if upside down). The direction of movement and their position in space are determined by the jellyfish with the help of balance organs. Interestingly, if the vials with statoliths are cut off from a jellyfish, its umbrella is less likely to contract. However, in the role of an invalid, a jellyfish is not destined to live long - these animals have excellent tissue regeneration. Due to the primitive structure, all cells in the body of jellyfish are interchangeable, so they quickly heal any wounds. Even if the jellyfish is cut into pieces or the “head” is separated from the lower body, it will restore the missing parts and form two new individuals! Characteristically, the recovery of the head end is faster than the end part. Even more surprising is that if such an operation is carried out on different stages development of a jellyfish, then each time individuals of the appropriate age will be formed - adults will form from an adult jellyfish, only larvae will form from the larval stage, which will continue their development as independent organisms. Thus, the tissues of one of the most primitive animals have the so-called cellular memory and "know" their age.
Medusa swimming upside down.
All jellyfish are predators because they feed exclusively on animal food. However, the prey of most jellyfish are tiny organisms - small crustaceans, fish fry, free-floating fish eggs and just small edible pieces of someone else's prey. The largest species of jellyfish can prey on small fish and ... smaller jellyfish. However, jellyfish hunting looks peculiar. Since jellyfish are practically blind and have no other senses, they are unable to detect and pursue prey. They find their food in a passive way, they simply catch with their tentacles the edible trifle that the current brings. Jellyfish catch the touch with the help of trapping tentacles and kill the victim with them. How do primitive helpless "jelly" do this? Jellyfish have powerful weapons - stinging or nettle cells in tentacles. These cells can be of different types: penetrants - the cells look like pointed threads that dig into the body of the victim and inject a paralyzing substance into it; glutinants - threads with a sticky secret that "glue" the victim to the tentacles; Volvents are long sticky threads in which the victim simply gets entangled. The tentacles push the paralyzed victim to the mouth, undigested food residues are also excreted through the mouth. The poisonous secret of jellyfish is so powerful that it affects not only small prey, but also animals much larger than the jellyfish themselves. Deep-sea jellyfish lure prey with a bright glow.
The victim can not get out of this tangle of mouth and trapping tentacles of a jellyfish.
The reproduction of jellyfish is no less interesting than other life processes. In jellyfish, sexual and asexual (vegetative) reproduction is possible. Sexual reproduction includes several stages. Sex cells mature in the gonads of jellyfish, regardless of the season, but in species from temperate waters, reproduction is still confined to the warm period of the year. Jellyfish are separate sexes, males and females outwardly do not differ from each other. The eggs and sperm are released into the water… through the mouth, during external environment fertilization occurs, after which the larva begins to develop. Such a larva is called planula, it is not able to feed and reproduce. A short time planula floats in the water, and then settles to the bottom and attaches to the substrate. At the bottom of the planula, a polyp is formed that can reproduce asexually - by budding. It is characteristic that daughter organisms form in the upper part of the polyp, as if layering on top of each other. AT eventually such a polyp resembles a stack of plates stacked on top of each other, the uppermost individuals gradually separate from the polyp and swim away. Free-swimming individuals of hydroid jellyfish are actually young jellyfish that gradually grow and mature; in scyphoid jellyfish, such an individual is called an ether, since it differs sharply from an adult jellyfish. After some time, the ether turns into an adult. But in the jellyfish pelagia and several species of trachilids, the polyp stage is completely absent; in them, mobile individuals are formed directly from the planula. Bougainvillea and Campanularia jellyfish have gone even further, in which polyps are formed directly in the sex glands of adults, it turns out that the jellyfish gives rise to tiny jellyfish without any intermediate stages. Thus, in the life of jellyfish, there is a complex alternation of generations and methods of reproduction, and several individuals are formed from each egg at once. The reproduction rate of jellyfish is very high and they quickly restore their numbers even after natural disasters. The life expectancy of jellyfish is short - most species live for several months, the largest species of jellyfish can live 2-3 years.
The dome of this jellyfish is decorated with stripes.
A tiny fish hides under the dome of a jellyfish.
The green turtle eats the jellyfish.
Jellyfish have been known to people since ancient times, however, due to their negligible economic value, they for a long time did not attract attention. The word medusa itself comes from the name of the ancient Greek goddess Gorgon Medusa, whose hair, according to legend, was a bunch of snakes. Apparently, the moving tentacles of jellyfish and their poisonousness reminded the Greeks of this evil goddess. However, little attention was paid to jellyfish. The exceptions were countries Far East whose inhabitants loved exotic food. For example, the Chinese eat eared jellyfish and edible ropil. One side the nutritional value jellyfish is negligible, since their body mainly consists of water, on the other hand, the abundance and availability of jellyfish suggested that at least some benefit could be derived from them. To do this, the Chinese first cut out poisonous tentacles from jellyfish, and then salt them with alum and dry them. Dried jellyfish resemble strong jelly in consistency, they are cut into strips and used in salads, as well as boiled, fried with the addition of pepper, cinnamon and nutmeg. Despite such tricks, jellyfish are practically tasteless, so their use in cooking is limited to the national cuisines of China and Japan.
Eared jellyfish is one of the edible species.
In nature, jellyfish provide some benefit by cleansing sea waters from small organic debris. Sometimes jellyfish breed so strongly that they clog water sumps in desalination plants with their mass, pollute the beaches. However, jellyfish should not be blamed for this sabotage, since the culprits of such outbreaks are the people themselves. The point is that emissions organic matter and the biological debris that fills the oceans is food for jellyfish and provokes their reproduction. This process is also facilitated by the lack of fresh water, since with an increase in the salinity of the sea, jellyfish multiply better. Since jellyfish breed well, there are no endangered species among them.
Seasonal invasion of jellyfish in the Black Sea is a common occurrence.
Under natural conditions, jellyfish do not pose any particular benefit or harm to humans. However, the venom of some species can be dangerous. Poisonous jellyfish can be conditionally divided into two groups: in some species, the poison has an irritating effect and can cause allergies, in others, the poison acts on nervous system and can lead to serious disruption of the heart, muscles, and even death. For example, the "sea wasp" jellyfish that lives in the waters of Australia has caused the death of several dozen people. Touching this jellyfish causes a severe burn, after a few minutes convulsions begin and many people die before they can swim to the shore. However, sea wasp there is an even more terrible competitor - the Irukandji jellyfish, which lives in pacific ocean. The danger of this jellyfish is that it is very small (12 cm in diameter) and stings almost painlessly, so swimmers often ignore its bite. At the same time, the poison of this crumb acts very quickly. Despite this, the danger of jellyfish in general is greatly exaggerated. In order to protect yourself from unpleasant consequences, it is enough to know a few rules:
Burns on a swimmer's hand left by a jellyfish.
Usually, a jellyfish sting victim recovers in 4-5 days, but one thing should be taken into account: jellyfish venom can act as an allergen, so if you meet the same type of jellyfish again, the second burn will be much more dangerous than the first. In this case, the reaction of the body to the poison develops faster and more powerfully, and the threat to life increases many times over. Nevertheless, the mortality from encounters with jellyfish is negligible and inferior to accidents with other animal species.
Jellyfish at the Monterey Public Aquarium.
Despite some hostility of jellyfish to humans, it has recently become fashionable to keep them in an aquarium. The smooth continuous movements of these fantastic creatures bring peace and soothe the nerves. However, the maintenance of jellyfish in an aquarium is associated with some difficulties: jellyfish are very sensitive to water pollution, do not tolerate desalination, and require a more or less pronounced flow of water. Most often they are kept in large public aquariums, where it is relatively easy to ensure the purity of the water and create a current. However, at home, jellyfish can also be kept. For home keeping, the moon jellyfish and the cassiopeia jellyfish are used, which will reach 20 and 30 cm in diameter, respectively. Only a special marine aquarium is suitable for keeping both species, always with a powerful water purification system, including mechanical filtration. In the aquarium, you need to create a current, but at the same time, make sure that the jellyfish is not sucked into the filter by the current. Jellyfish require special lighting, so metal halide lamps will have to be installed in the aquarium. Please note that the water temperature for the moon jellyfish should not exceed 12-18 ° C, Cassiopeia may well live at room temperature. You need to feed jellyfish with live food - brine shrimp, it is easy to purchase in specialized stores, from amateur aquarists. Both species are not dangerous, but can still cause painful burns, so be careful when caring for jellyfish. Do not forget that jellyfish will not tolerate proximity to fish; only immobile animals or bottom organisms can be settled in their aquarium.
Jellyfish (Polypomedusae) is a representative of the marine fauna. The class of jellyfish, which include and freshwater hydras, consists of many inhabitants of the sea, some of which are very large and conspicuous.
Medusa has a gelatinous, and sometimes almost cartilaginous body in the form of a rain or lady's umbrella with a stalk extending downwards or a bell with a tongue hanging down.
In the umbrella of a jellyfish, one can distinguish between a convex outer or upper side and a concave inner or lower side. From the center bottom surface the umbrella of the jellyfish goes down either a very short, or a rather long stalk, which is a mouth tube; on the lower edge of this tube, protrusions of various sizes are located around the oral 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 nooses, the number of which is very different, visual, auditory, and sometimes olfactory organs are immediately placed.
The stomach of the jellyfish, which communicates with the mouth by means of a pharyngeal tube, passes into a whole series of radiant canals or elongated pockets heading towards the edge of the bell. Eggs and seed cells develop in the stomach or on the walls of the channels extending from it.
The life cycle of a jellyfish includes the formation of a polyp, then a jellyfish, then another polyp, and so on. As for the polyp, it differs from the medusa in the absence of a bell. Each polyp is represented as a saccular, closed at one end of the body; the closed lower end of such an individual is attached to some foreign object or to a polyp, which sometimes swims freely or is attached to something.
The opposite end of the polyp is usually elongated in the form of a cone and has an opening in the center, called the mouth, surrounded by tentacles. If we imagine that such a polyp, having separated from the object to which it was attached, is somewhat flattened in the dorso-abdominal 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: it remains only for this disk to become convex and get 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 disk, 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 in vascular system jellyfish as follows: its adjacent walls grow together along the periphery for some length with each other, as a result of which radially located channels are obtained. 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.
Jellyfish are organisms that develop sexual products; polyps, which are one of the stages in the 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 in turn produce jellyfish asexually. There are, however, jellyfish whose eggs only develop into jellyfish; polyps are also known, giving eggs and seed cells instead of jellyfish. There are various transitions between these two extreme cases. During 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 usually for the detachment hydroid polyps and hydroid jellyfish (Hydroidea). All these main features of hydroid polyps are also characteristic of freshwater polyps, that is, hydras.
The sexual generation of hydroid polyps are usually hydroid jellyfish, which are characterized by the presence of a membranous rim along the edge of the bell, the so-called sail.
Among the types of hydroid polyps that do not have alternation of generations, i.e., do not develop jellyfish, are freshwater polyps. The so-called sarsia (Sarsia), named after a Swedish naturalist, belongs to the same hydroid polyps; reproduction of species of this genus is associated with alternation of generations.
The tubular sarsia itself (S. tubulosa) has the appearance of slender and slightly branched bushes, 10-15 mm high; its polypiks, 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 the like.
The club-shaped polyps of Sarsia bud off, 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; a simple eye is placed at the base of each tentacle.
The detachment of hydroid polyps and hydroid jellyfish that has just been described is adjoined by the detachment 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 noose, jellyfish-like individuals that produce egg cells and spermatozoa in themselves, and, finally, some members of the colony turn into apparatuses or into bells that serve to move the colony.
Among the flat siphonophores is the so-called sailboat (Velella); this animal floating 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 underside of the disk in the center is one large feeding polyp, surrounded by many smaller ones; along the edges of the disc are the tactile members of the colony.
The most famous species of this genus is the common sailboat (Velella spirans), which can often be found very far from the coast, from which it is driven away by the wind; in this animal, at the base of small polypiks, small jellyfish-like creatures bud, which already develop reproductive products and thus serve to reproduce the sailboat.
Another form, the bladder (Physalia), most of the body of which falls on a huge air sac lying horizontally on the water surface; large and small feeding polyps, armed with long lassoes, are placed on the lower surface of the bladder; there are also palps.
Common vesicle (Ph. caravella), with purple, white-speckled polyps and a purple-red air sac, which plays the same role as the scallop of the sailfish, is common in the Mediterranean Sea and Atlantic Ocean; the dimensions of this form reach 30 cm in length (not counting the lasso, which can be very significantly lengthened).
Representatives of the next order, Acalephae, differ from hydropolyps, hydromedusae and siphonophores, approaching them in the structure of polypoid and medusoid individuals of the entire colony, in the structure of both polyps and jellyfish: jellyfish of this order reach for the most part quite significant sizes and have an umbrella, dissected along the edges into separate lobes.
As for polyps, their characteristic feature is the presence of four correctly located longitudinal swellings that fit on the inner wall of their gastric cavity; 4 bags lie between the indicated swellings.
In some cases, a medusa immediately develops from a medusa egg, but for the most part it turns into a small goblet polyp with tentacles around the oral disc; on such an embryo, sitting motionless on algae, etc., horizontal, one below the other, annular constrictions begin to appear; in this form, the whole embryo is like a stack of plates; soon individual disks - future jellyfish - bud off one after another and, floating freely, turn into sexually mature forms.
The suborder of broad-tentacled akalefs (Semostomae), characterized by the presence of 4 long, boat-shaped simple tentacles located around the cruciform mouth, belongs to the very common in the Baltic and in general in European seas, eared jellyfish Aurelia aurita (Aurelia aurita); it is distinguished by a flat, like a watch glass, and sometimes a hemispherical umbrella and narrow, lanceolate, strongly layered 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 ranges between 1 and 40 cm in diameter, but specimens of 5-10 cm are most often found.
Another well-known jellyfish from the Akalefs is the hairy jellyfish (Cyanea capillata), characteristic of the 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 - nooses.
The described jellyfish appears in autumn, like an 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 long.
Even larger, i.e., over 2 m in diameter, reaches the northern hairy jellyfish (C. arctica), the length of the tentacles of this species sometimes exceeds 4 m. This jellyfish is thus the largest of all jellyfish known to us.
As for the root-mouthed jellyfish (Rhizostomeae), they differ from the previous ones in the presence of 8 long root-shaped mouth tentacles arranged in pairs; these tentacles in most cases 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 these stomata, these jellyfish often have more or less numerous mouth palps, with button-like thickenings at the ends.
An example of such a jellyfish is the Mediterranean cotylorhiza (Cotylorhiza tuberculata), it is a yellowish jellyfish in general, 10-20 cm wide in diameter with long sucking tubes or suckers on long legs; the edges of the disk of this jellyfish are spotted with white spots, the oral disk is meaty red or yellowish-brown; milky-white tentacles, which, however, can sometimes be amber-yellow, brown, purple or blue, like violet, scallops surrounding the sucking holes - these are the features that describe the described jellyfish in more detail.
Both of the mentioned groups of jellyfish, broad-tentacled and corner-mouthed, constitute a suborder of disc-shaped jellyfish (Discomedusae), the characteristic features of which are: a flat, mostly disc-shaped bell or umbrella, usually with 8 marginal sensory organs; the edge of the bell is cut into at least 16 blades; the stomach is surrounded by 8, 16, 32, or even a large number of gastric sacs; on the lower wall of the stomach are the sex glands, very clearly visible in our eared jellyfish and called eyes in the common people.
The next group of cuboid jellyfish (Cubomedusae) is defined by the following features: a tall, cubic umbrella, the edge of which, resembling the swimming rim of hydroid jellyfish, is in the form of a horizontally tense or hanging down membrane; on this edge there are 4 sensitive flasks, with an eye and an organ of hearing on each.
A representative of this group is the Mediterranean common cube-shaped 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 that of the eyes of vertebrates.
The sea wasp jellyfish is the most poisonous jellyfish in the world, it lives off the coast of Thailand and Australia. Its body is vitreous - cube-shaped, that is, this jellyfish belongs to cuboid jellyfish. Its stinging cells leave deadly burns. As a result of which death can occur within 3 minutes.
However, there are survivors - these are people with a strong heart. There is an antidote against the burns of the 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 the open ocean, then have an antidote with you.
Finally, the last group of goblet jellyfish (Stauromedusae) is characterized by the presence of a leg at the top of the goblet umbrella, with the help of which the jellyfish is attached to algae, etc .; tentacles, mostly in bundles, sit on these jellyfish along the edge of the bell.
The described suborder includes, among other things, the lantern (Lucernaria), belonging 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 leg of the jellyfish, 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 genus described is the common lantern (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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Aurelia jellyfish is a species of marine life that 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.
In Aurelia, the umbrella is flat and can reach 40 cm in diameter. Since it is based on a non-cellular substance (it consists of 98% water), it is completely transparent. This quality also determines that the weight of these animals is close to the weight of water, which greatly facilitates swimming.
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 very densely seated with a huge number of stinging cells.
This jellyfish has a quadrangular mouth, has 4 movable blades along the edges. Their contraction (they are covered also makes it possible to pull the prey to the mouth and securely capture it.
Issues of keeping jellyfish differ in some specifics. Initially, it was in aquariums. For jellyfish, special containers are needed that provide a circular smooth flow. This allows the animals to move freely without fear of any collision. 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 rate, which should allow the 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 the use of aeration is absolutely excluded for jellyfish in aquariums. This is due to the fact that air bubbles can be 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 do not need special lighting either, mostly simple lighting is enough.
Also note that there is no need for water filtration. As a rule, only regular water changes are sufficient to ensure that its quality always remains at the proper level. If there is no desire to constantly update the water, you can also start installing a life support system. At the same time, it is important to take proper care of the protection of animals. Because they can be pulled into the intake devices.
In addition, it must be borne in mind 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.
How are jellyfish fed? They are great with a mixture that consists of brine shrimp, phytoplankton, heavily crushed crustaceans and seafood. Although at the moment there are various ready-made foods on sale that Aurelia (eared jellyfish) can also eat. But there is one feature. If the animals do not like the food at all, they can start eating the rest of the jellyfish.
Aurelia jellyfish is dioecious. So, the testes in males are milky white, they are perfectly visible: these are small half-rings in the body of the animal. Females have purple or red ovaries, which are also visible in the light. Therefore, by coloring, you can understand what gender the jellyfish is. Aurelias breed only once in their life, and then die. Their main distinguishing feature is the manifestation of concern for their own offspring (which is not typical of other species).
It is worth noting that the fertilization of eggs, as well as their further development, takes place in special pockets. Eggs enter them through the gutters from the mouth opening. After fertilization, the egg divides into 2 parts, each of which is further divided in half, and so on. Due to this, a single-layer multicellular ball is formed.
Some of the cells of this ball gets inside, which can be compared with pressing a rubber ball. Because of this, a two-layer embryo appears.
He can swim, thanks to the large number of cilia that are located on his outer part. The embryo then becomes a larva, which is called a planula. For some time it just floats, and then falls to the bottom. It is attached with its front end to the bottom. Quite quickly, the back 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.
Aurelia jellyfish is often used in medicine. Laxatives and diuretics were produced from it in the Middle Ages. And today, from the poison that is contained in the tentacles of animals, they develop means to regulate pressure and treat various pulmonary diseases.
Farmers in the Caribbean use physalium poison as a poison for rodents.
Jellyfish allow you to effectively deal with stress. They are bred in Japan in special aquariums. Slow, smooth movements of animals calm people down, while keeping them is very expensive and troublesome.
Phosphors 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 processes that were previously inaccessible. Because of this action, the rodents began to grow green hair.
Some of the jellyfish are caught off the coast of China, where their tentacles are removed, while 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, poached vegetables, and then poured with sauce.
Robot jellyfish also appeared there. They, unlike real animals, not only swim beautifully and slowly, but can also “dance” if the owner wishes to the music.
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.
Basic data:
DIMENSIONS
Diameter: jellyfish - up to 40 cm, ether - about 0.5 cm.
Color: pinkish or slightly purple, four horseshoe-shaped purple genitals showing through.
BREEDING
Fertilization: external.
Number of eggs: many thousands.
LIFESTYLE
Habits: the polyp is attached to a rock or algae; adult jellyfish swim in groups in coastal waters.
Food: mostly plankton.
RELATED SPECIES
Aurelia is one of the 200 species of jellyfish. The scyphoid class is divided into five rows. Seven species of jellyfish are found off the coast of the Baltic and North Seas. Its close relative is the edible ropilema.
Aurelia lives in almost all temperate and tropical seas of both hemispheres. There is a lot of it in the Baltic and North Seas. The genitals of Aurelia resemble horseshoes in their shape. Aurelia can be pinkish or slightly purple in color with dark semicircles in the middle of the umbrella.
Young Aurelia actively hunts even when it is still a small jellyfish with a diameter of about two centimeters. An adult Aurelia does not have to actively hunt to find food. 
At first glance, Aurelia seems to be a completely harmless creature, but a hunting jellyfish can paralyze its prey with the poison of stinging cells. Adult Aurelia has several types of gonial cells. The largest of them protrude above the surface of the body. In case of irritation, the cage opens, and the harpoon digs into the body of the victim, injecting poison that paralyzes the prey. The fibers of smaller sting cells wrap around the prey and hinder movement. The fibers of the smallest cells turn into sticky secretions, which gives the polyps the opportunity to attach themselves to the rock.
Aurelia lives in the seas of the whole world, she keeps to the coast. Adult individuals are united in large groups. Aurelia is a bad swimmer. Thanks to the contractions of the umbrella, it can only slowly rise to the surface, and, having become motionless, sink to the depths. The edge of the umbrella has 8 ropals, on which there are eyes and statocysts. Thanks to these sense organs, the jellyfish keeps at a certain distance from the surface.
- Range of eared jellyfish Aurelia eared (lat. Aurelia aurita) is a scyphoid jellyfish of the family Ulmaridae from the order Discomedusa (lat. Semaestomae).
This is the most big jellyfish found in the waters of the Black and mediterranean seas. Her transparent umbrella reaches a diameter of 40 cm. When meeting with her, it is recommended to be very careful, since even a light touch of her tentacles can cause severe burns.
Aurelia eared lives in tropical and temperate waters of the seas and oceans of the planet, with the exception of the polar regions. The largest colonies of jellyfish are located in equatorial regions close to the coast.
Eared aurelias easily tolerate the pollution of their habitat and quickly adapt to environmental conditions, so they often settle in port waters or near power plant collectors that discharge warm water.
The body of Aurelia eared is 98% water. Along the edge of the umbrella are receptor cells that perform the functions of balance organs and light-sensitive eyes. With their help, the jellyfish can determine prey and navigate in space.
Tentacles growing along the edge of the umbrella are designed to grab and move the victim to the oral cavities. An important role in the circulatory system of the jellyfish is played by water, which constantly circulates in the intestinal cavity. Aurelia eared absorbs oxygen dissolved in water, carrying out gas exchange processes with its entire body.
Aurelia poison is not dangerous for all creatures. For example, pilot fish fry very often hide between its tentacles. They are not afraid of poisonous stinging glands. Very often they can eat plenty of the remnants of their owner's food.
In the course of their development, scyphoid jellyfish undergo alternation of generations. Polyps reproduce by budding, while jellyfish reproduce sexually.
Adult males release sex products into the water.
Then they penetrate into the brood chambers of females, where they subsequently fertilize and develop. After the end of this process, the eggs are in the oral cavities of the females until they turn into larvae. Then the larvae (planula) break away from the mother's body and sink to the bottom. There they turn into a single polyp called scyphilistoma.
The polyp leads a sedentary lifestyle. With the help of tentacles, he hunts for plankton. In winter, all adult jellyfish die, only polyps remain. With the advent of spring, it begins to bud and produces up to 30 young jellyfish. This process is called strobilization. One polyp gives life to both male and female individuals.
The larvae of tiny jellyfish go free swimming. Outwardly, they are very similar to adults, but only very small. The diameter of their umbrellas reaches 2 mm.
After a month, they increase to 1 cm and acquire a well-formed umbrella, from which tentacles begin to grow. After 3 months, they have sex glands, and they become ready for reproduction.
Jellyfish drift in large colonies in coastal waters. They move in a reactive way. Having drawn water into the umbrella, and then, having contracted, they push it out.
At night, Aurelia eared descends to a depth of 10 meters, and during the day it rises closer to the surface. The main food consists of small fish, planktonic organisms and small jellyfish of other species.
Aurelia's weapons are stinging cells, which can infect the victim with poison. The mouth lobes pick up the immobilized prey and place it in the mouth opening, from where the food enters the intestinal cavity. The oral lobes of Aurelia are outgrowths from the mouth opening. Their inner surfaces are littered with stinging glands with deadly poison.
The intestine begins to secrete digestive enzymes and then proceeds to absorb the digested food. Undigested food remains through the mouth opening are brought to the surface.
The diameter of Aurelia eared can reach 40 cm, and weight up to 10 kg. The body of a jellyfish looks like an umbrella with 8 cutouts along the edge. The flat umbrella is filled with a thick layer of gelatinous substance. A lot of tentacles grow along its edge.
The oral cavity is surrounded by 4 wide oral lobes. The receptor cells located along the edges serve as sensory organs.
The life expectancy of Aurelia eared is about one year.
