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).
These tentacles consist of string cells that contain poison and are therefore directly intended for hunting. It is interesting that even after death, jellyfish are able to sting for another fortnight. Some species can be deadly even to humans. For example, the animal known as " Sea Wasp"is considered the most dangerous poisonous animal in the world's oceans: scientists claim that its poison is quite enough to poison sixty people in a few minutes.
The outer part of the body is smooth and convex, while the lower part resembles a bag. In the center of the lower part there is a mouth: in some jellyfish it looks like a tube, in others it is short and wide, in others it resembles short clubs. This hole also serves to remove food debris.
These animals grow throughout their lives, and their size largely depends on the species: among them there are very small ones, no more than a few millimeters, and there are also huge ones, the body size of which exceeds two meters, and together with the tentacles - all thirty ( for example, the largest jellyfish in the world's oceans, Cyanea, which lives in the North-West Atlantic, has a body size of more than 2 m, and with tentacles - almost forty).
Despite the fact that these marine animals lack brains and sensory organs, they have light-sensitive cells that act as eyes, thanks to which these organisms are able to distinguish darkness from light (they, however, are not able to see objects). Interestingly, some specimens glow in the dark, 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.
Methods of transportation
Since all representatives of this class (even the largest individuals, whose weight exceeds several centners) are almost unable to resist sea currents, scientists consider jellyfish as representatives of plankton.
Most species water flows still do not give in completely and, although slowly, they move, using the current and thin muscle fibers their body: contracting, they fold the body of the jellyfish like an umbrella - and the water that is in the lower part of the animal is sharply pushed out.
As a result, a strong jet is formed, pushing the animal forward. Therefore these sea creatures always move in the direction opposite to the mouth. They are helped to determine where exactly they need to move by the balance organs located on the tentacles.
Regeneration
One more interesting feature of these creatures is their ability to restore lost parts of the body - absolutely all the cells of these animals are interchangeable: even if this animal is divided into parts, it will restore them, forming two new individuals! If you do this with an adult jellyfish, an adult copy will appear; from a jellyfish larva, a larva will appear.
Reproduction
Looking at these amazing translucent creatures, many ask themselves the question of how jellyfish reproduce. Reproduction of jellyfish is an interesting and unusual process.
Answering the question of how jellyfish reproduce, it is worth noting that in this case, 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, fish caviar. 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 prominent representatives hydromedusa - jellyfish Turritopsis nutricula: the only creature discovered by people about which scientists have declared that it is immortal.
Having reached maturity, it sinks to the bottom of the sea, transforming into a polyp, on which new formations are formed, from which new jellyfish subsequently arise.
This process is repeated more than once, which means that it is constantly reborn, and can die only if it is eaten by some predator. These are the interesting facts about jellyfish that scientists recently told the world.
Scyphojellyfish
Scyphoid jellyfish have a more complex structure compared to hydromedusae: they are larger than representatives of other species - the largest jellyfish in the world, the Cyanea jellyfish, belongs precisely to this class. 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 amount 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 allergic reaction or even painful shock. Having seen this animal, it is advisable not to take risks and, when swimming past, not to touch it.
Some of the most striking specimens of this species, in addition to the Cyanea jellyfish, are also the Aurelia jellyfish (the most typical representative) and the Golden jellyfish - an animal that can only be seen on the archipelago Rocky Islands 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 underground tunnels and filled with slightly salted water. Representatives of this species also differ from marine specimens in that they completely lack pigment spots, have no stinging tentacles, and no tentacles that surround the mouth.
Although the golden jellyfish is a scyphojellyfish, over many years it has turned into a completely different species that does not pose a danger to humans, since it has significantly lost its stinging ability. An interesting fact is that the Golden Jellyfish began to grow 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 just this species, lives near the Australian coast and is called the Box Jellyfish or Sea Wasp: its poison can kill a person in just a few minutes. This wasp is almost transparent, of a pale blue hue, which is why it is difficult to notice on the water, which means it is easier to stumble upon it.
The Sea Wasp is the largest jellyfish in its class - its body is the size of a basketball. When a sea wasp simply swims, its tentacles are reduced to 15 cm in length and are almost invisible. But when the animal hunts, they stretch out to three meters. Sea Wasps feed mainly on shrimp and small fish, and they themselves are caught and eaten sea turtles- the only animals on our planet that are insensitive to the poison of some of the most dangerous creatures on the ground.
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 sedentary lifestyle life, attaching to a solid 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 house the stomach) and tentacles containing 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, the life cycle of jellyfish 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.
A slight touch of the tentacles of a 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 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 most large species, for example, jellyfish lion's mane 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 clusters jellyfish are being observed more frequently and may serve as an indicator of sea pollution or global warming. Swarms of jellyfish usually form in warm water, and jellyfish are able to thrive in oxygen-free conditions sea conditions, which are not suitable for life for other invertebrates of this size.
Among all the creatures on the planet, jellyfish are one of the most ancient. Scientists claim that they lived in water spaces hundreds of millions of years ago. These creatures are found both in the seas and oceans. Are different appearance, because some are attractive, while others, to put it mildly, are repulsive. Some of them are harmless, but some carry hidden threat so we collected everything interesting facts about jellyfish and combined them into one list.
1. The most huge jellyfish It is called the Arctic giant and its size is truly impressive. It was possible to find an individual whose dome diameter is almost 2.5 meters, and the length of the entire body, including tentacles, is over 35 meters.
2. It has long been believed that fish are soothing, so people often buy aquariums for themselves at home and admire the inhabitants of the seas, feeding them. In Japan, jellyfish are bred for the same purpose, because researchers in this country have found that their monotonous, smooth movements completely help strengthen the nervous system.
3. Interesting fact about jellyfish for children. Their largest concentration is in the lake of the same name on the Rocky Archipelago. According to preliminary estimates, there are more than two million individuals there, and this despite the fact that the lake itself is 450 meters long and only 170 wide.
4. The creature does not have lungs; it captures oxygen mixed with water with its entire body. At the same time, the jellyfish also does not have a brain, but has two nervous systems and two dozen eyes.
5. Among the most interesting facts about jellyfish is the box jellyfish and its capabilities. The creature can reach speeds of up to two meters per second and at the same time has a deadly powerful poison. Even the slightest touch to her is fatal, and the total amount of poison in her body is enough to send at least fifty people to the next world.
6. Despite the simplicity of their body structure, jellyfish are capable of movement. They swallow some of the water into themselves and then push it back out. But this happens extremely rarely; most often they prefer to follow the flow, completely inactive.
7. Jellyfish are regularly used in medicine. Back in the Middle Ages, it was discovered that a separate part of their body, called the cornet, has a laxative property. Nowadays, the poison of these creatures is actively used, because it makes more effective medicines, which helps normalize blood pressure.
8. Life cycle jellyfish is unique. It begins with eggs, from which planulae are born; they resemble a ciliate shoe enlarged thousands of times, which drifts in the water surface until it encounters something solid on its way, be it a reef, a rock, or maybe the bottom. Having attached to it, it forms a polyp, which gradually grows and forms into something more reminiscent of a jelly-like creature. Sometimes after a month, and sometimes after a year, the changed polyp detaches and the jellyfish appears before the world.
9. Any animal known to possess poison, as a rule, infects its victim through a bite. But jellyfish are a clear exception, because for this they have special organs called nematocysts. Feeling threatened, they stimulate them with such force that they literally explode, striking the enemy's body with hundreds of drops of deadly poison.
10. There is an assumption that one of the types of these creatures is immortal. Scientists have been able to establish that Turritopsis dornii, already fully grown, can return to the polyp state and, in theory, can do this indefinitely. However, this was only verified in the laboratory, because in reality real life they are either eaten or sooner or later washed up on the shore.
The biology report on jellyfish can be supplemented with interesting facts about jellyfish. Messages about jellyfish contain a lot of educational information.
Report on the topic “Jellyfish”
Jellyfish is an invertebrate marine animal with a transparent gelatinous body, along the edges, equipped with tentacles. She is a lower multicellular creature, belongs to the type coelenterates. Among them there are free-swimming (jellyfish), sessile (polyps), and attached forms (hydra).
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 coral islands. Some of the species love cool water, others - warm, others live only in the upper layers, and others - only at the bottom.
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 resemblance to the character ancient greek myths- Gorgon Medusa.
Jellyfish 98% consist of water, therefore, his body is almost transparent, like a dome. And they move due to muscle contraction. On the lower concave side of jellyfish there is an oral stalk. The mouth leads into the pharynx, which opens into the stomach. Radial canals diverge from the stomach to the ends of the body, forming the gastric system. Undigested food remains are also removed through the mouth.
There are tentacles along the edges of the jellyfish. They are very different: some are short and thick, and some are long and thin. Their number ranges from four to four hundred (the number of tentacles is always a multiple of four, because these animals are characterized radial symmetry).
Tentacles are built from containing toxic substances stinging cells and are needed for movement, hunting and holding prey.
Interesting fact about jellyfish: even dead jellyfish can bite for about two weeks. Selected species Jellyfish are extremely dangerous for humans. For example, an animal called the Sea Wasp can poison six dozen people in a couple of minutes.
Jellyfish increase in size throughout their lives, and their final size depends on the species. There are tiny ones, no more than a couple of millimeters, but there are giants over 40 m(along with tentacles). Cyanea - largest representative, lives in the North Atlantic.
At the jellyfish no brain and sense organs, but there are light-sensitive cells that help them distinguish between darkness and light. 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.
Jellyfish 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.
The message about jellyfish can be used by 7th grade students.
Goals:
Expand and deepen children's understanding of jellyfish.
Show children natural connections in nature.
Dictionary: scuba.
Develop the fine muscles of children's hands.
Cultivate an interest in nature, a desire to learn something new about it.
Equipment:
Photos of jellyfish, picture with underwater seascape, paper, scissors, glue, brushes, napkins.
Aurelia jellyfish
Cornermouth jellyfish
Progress of the lesson:
Today we will take a trip to the underwater sea kingdom.
But can a person stay under water for a long time? Why? (Children's answers). Of course, we all need air to breathe. Do you know what device a French explorer came up with in order to stay under water for a long time? (Children's answers). This device is called scuba gear. We have come across words starting with “aqua” more than once. Remember them. (Children's answers). Aquarium, water park, watercolor. The meaning of these words is somehow connected with water. “Aqua” is water, only in a different language, in Latin.
Put on your scuba gear and let's dive into our sea. What is it called? (Children's answers). (Imitation of putting on scuba gear and diving).
Who can we meet in the waters of our Black Sea? (Children's answers). There are dolphins, mussels, rapana, katran, and anchovy.
And here is the mysterious jellyfish. Take a look at the picture.
In summer and autumn there are many jellyfish off the coast of Crimea. They clog fishing nets, disturb those swimming in the sea, and sometimes waves wash them ashore. They were called differently: sea lard, sea moon, sea heart. Why do you think? (Children's answers).
Many different small jellyfish live in our sea, and there are also large ones. They are armed. They have stinging cells under their umbrella. Take a look at the photo. Here they are, looking like tentacles. If an enemy approaches the jellyfish, it can burn him with its stinging cells. This burn resembles a nettle burn. Hence the names of jellyfish such as stinging nettle and sea nettle. For jellyfish enemies this burn is dangerous, but for humans it is not so dangerous, but painful. So when you meet a large jellyfish, look at it, admire it, but do not approach or touch it.
Jellyfish move by contracting their umbrellas. Connect the fingertips of both hands and round your palms so that you get a hemisphere - that’s the jellyfish umbrella. Now try to show how it contracts. Here the jellyfish swims slowly, but here it swims faster. (Performed finger gymnastics). And now the jellyfish is swimming fast. There will be a storm at sea soon. How many of you know what a sea storm is called? (Children's answers). Shortly before a storm, jellyfish swim away from the shore. Scientists have noticed this and use it to warn of an impending storm.
Previously, it was believed that a jellyfish had no eyes and therefore could not see anything. But one Russian scientist carefully observed jellyfish and noticed that they were moving out of the darkness towards the light. So, jellyfish see the light! But no one believed this scientist. But he didn’t give up and found jellyfish eyes on their tentacles. It’s not for nothing that they say: “patience and work will grind everything down.”
And now the game. Stand in a circle and take the ball. You already know a lot about nature. For example, that everything in nature is interconnected, someone takes care of someone, someone eats someone. The person to whom I throw the ball must continue my sentence.
1. The hare is food for... (wolf, fox).
2. Honey – favorite treat... (bear).
3. They eat insects - ... (birds).
4. The cormorant sea raven eats - ... (fish).
5. Deer eat - ... (grass).
6. Plankton is food -... (whales).
7. They feast on fish - ... (sharks, seagulls, etc.)
Imagine that no one eats jellyfish. These are these amazing creatures that no one will encroach on them. Except for the person. In China and Japan they eat jellyfish. And the jellyfish themselves eat plankton. But young mackerel fish are hiding under the umbrellas of jellyfish. Until they grew up and gained strength. Would you like predatory fish feast on the babies, but they are afraid of jellyfish stinging cells. When horse mackerels grow up, they leave their shelter under the umbrella of the jellyfish and pay her with black ingratitude: they bite off the edges of the umbrella. That's how good is paid for with evil.
Paper construction “Medusa”
Now I want to invite you to make a jellyfish out of paper. Using scissors, glue and, of course, your skillful hands, we will make a jellyfish like this. (Paper construction. Examination of crafts.)
Questions:
1. How does a jellyfish protect itself from enemies?
2. What does a jellyfish eat?
3. Who eats the jellyfish itself?
4. What is the name of the device for a person’s long stay under water?
5. Who takes refuge under the jellyfish's umbrella?
6. How does a jellyfish move?
7. What do you know about the eyes of a jellyfish?
8. When do jellyfish swim away from the shore?
9. What names were given to the jellyfish?
You can invite children to write stories about the adventures of a jellyfish, draw illustrations, and put them in a book.
The Legend of the Jellyfish: "Heart of the Sea"
One day two brothers were swimming in the sea. So the eldest, when he took a swim, quietly swam to the shore, and the younger one swam further and further from the shore. And fell in love sea wave brave brother: she took him, hugged him tightly and pulled him to the bottom, in underwater kingdom sea
The boy resists, screams, calls his brother for help. And the eldest is afraid to swim. He thinks: “It’s deep there, I’ll drown with him!”
- Oh, my dear brother! Oh, beloved brother, save me! – last time The boy emerged, shedding tears.
“Let God save you,” the elder said cowardly, but he himself did not dare to look at how his brother was drowning, and quickly rowed to the shore and climbed onto a stone.
The wave got angry and chased the coward, caught up, carried him into the sea and drowned him.
The sea queen sheltered her younger brother at the bottom. And she turned his tears into sparkling pearls, and his curls into corals. And the older brother of the fish and crayfish was stolen to the ground. Only no one wanted to touch the heart: this cowardly heart was so vile.
Since then, that heart has appeared in the sea. It swims timidly, furtively, slippery, cold, stinging, like nettles, it moves sluggishly, trembles, there is not even a shadow from it - transparent. But the sea disdains the heart: it throws it onto the shore, and there it dies without a trace.
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