The Scyphoid class includes jellyfish that inhabit the seas and oceans (they live only in salt water), which are able to move freely among the expanses of water (with the exception of the sessile jellyfish, which leads a sedentary lifestyle).
general characteristics
Scyphoid jellyfish They live everywhere, they have adapted to life in cold and warm waters. There are about 200 species. They are transported over considerable distances with the current, but can also move independently. Thus, with the help of active contractions of the dome and the release of water from it, the jellyfish can develop greater speed. This method of movement was called reactive.
The jellyfish has the shape of an umbrella or a longitudinally elongated dome. There are quite a few large species. Some representatives of the scyphoid class reach 2 m in diameter (Cyanea arctica). Many tentacles extend from the edges of the bell, which can grow up to 15m in length. They contain stinging cells that contain toxic substances necessary for protection and hunting.
Structural features
In the middle of the inner concave part of the umbrella there is a mouth, the corners of which turn into oral lobes (necessary for capturing food). In rootostomes, they grow together and form a filtering apparatus for absorbing small plankton.
Scyphoids are endowed with a stomach with 4 pocket-like protrusions, and a system of radial tubules, through which nutrients from the intestinal cavity are distributed throughout the body. Undigested food particles are sent back to the stomach and eliminated through the mouth.
The body of jellyfish consists of two layers of epithelial cells: ectoderm and endoderm, between them is mesoglea - jelly-like tissue. It consists of 98% water, so jellyfish quickly die under the scorching sun. Jellyfish have enormous regenerative abilities; if you cut it into 2 parts, each will grow into a full-fledged individual.
Since scyphoid jellyfish have switched to an active way of life, their nervous system has become more developed. There are clusters at the edges of the umbrella nerve cells, nearby there are also sensory organs that perceive light stimuli and help maintain balance.
Life cycle and reproduction
Scyphoids go through two phases in their life cycle: sexual (jellyfish) and asexual (polyp).
All representatives are dioecious organisms. The germ cells originate from the endoderm and mature in the pouches of the gastric cavity.
The gametes exit through the mouth and end up in the water. During the process of fusion of germ cells and further maturation, a jellyfish larva, a planula, emerges from the egg. It sinks to depth, attaches to the bottom and enters the asexual phase.
A single polyp (scyphostoma) leads a benthic life and begins to reproduce through lateral budding. After a certain time, the scyphistoma turns into a strobila, then the tentacles begin to shorten, and transverse constrictions form on the body. This is how a division called strobilation begins. Thus, the strobila gives life to young organisms - ethers. The ethers are then converted into adults.
Lifestyle
Scyphoid jellyfish do not live in schools and do not transmit signals to each other, even when at close range. Life expectancy is about 2-3 years, sometimes it happens that a jellyfish lives only a couple of months. They are also often eaten by fish and turtles.
All jellyfish are predatory animals. They consume plankton and small fish, which are immobilized by poisonous cells. Stinging cells release poison not only during hunting, but also to all organisms passing by. Therefore, jellyfish are dangerous for people in the water. If you accidentally catch the tentacles of a jellyfish, it will burn your skin with its poison.
The most common representatives of the class of scyphoid jellyfish are Aurelia, Cyanea, which inhabits the Arctic seas, and Cornerot, which is devoid of tentacles and lives in the waters of the Black Sea.
Meaning in nature and human life
Scyphoid jellyfish are part of the food chain of the world's oceans.
In Chinese and Japanese cuisine, dishes with rhopilema or aurelia are often found. Jellyfish meat is considered a delicacy.
Cornerot is the largest jellyfish in the Black Sea with a dome diameter of about 40 cm. Thus, it serves as a shelter for fish fry and protects them from predators and unfavorable environmental conditions. Sometimes, when the fry grow up, they begin to bite off small pieces of the jellyfish, or may eat it altogether.
Scyphoid jellyfish filter water, clearing it of contaminants.
For humans, the dangerous poison of jellyfish, which causes skin burns, sometimes provokes a painful shock and a person, being at depth, can no longer surface on his own. It is not safe to touch a jellyfish even when it is dead. When touched, an allergic reaction develops, disruption of the nervous and of cardio-vascular system, convulsive attacks occur.
Jellyfish are very amazing creatures that evoke an extraordinary attitude towards them. Jellyfish can be found in every sea, in every ocean, on the surface of the water or at a depth of many kilometers.
Jellyfish are the oldest animals on the planet, their history goes back at least 600 million years. There is an incredible number of different species in nature, but even now the emergence of new ones, previously unknown to scientists, is being recorded.
Jellyfish (Polypomedusae) are one of the phases of the life cycle of cnidarians Medusozoa, which are usually divided into three types: hydroid, scyphoid and box jellyfish. Jellyfish reproduce sexually. There are males who produce sperm and females who produce eggs. As a result of their fusion, the so-called planula is formed - a jellyfish larva. The planula settles to the bottom, where over time it turns into a polyp (asexual generation of jellyfish). Having reached full maturity, the polyp begins to bud off a young generation of jellyfish, often completely different from the adults. In scyphoid jellyfish, the newly separated specimen is called ether. The body of jellyfish is a jelly-like dome, which, through contractions, allows them to move in the water column. Tentacles equipped with stinging cells (cnidocytes) with a burning poison are designed for hunting and capturing prey.
The term "jellyfish" was first used by Carl Linnaeus in 1752, as an allusion to the animal's resemblance to the head of the Gorgon Medusa. Becoming popular around 1796, the name began to be used to identify other medusoid species of animals, such as ctenophores.
Some interesting facts about jellyfish:
The world's largest jellyfish can reach up to 2.5 meters in diameter and have tentacles more than 40 meters long. Jellyfish are capable of reproducing both sexually and by budding and fission. The Australian wasp jellyfish is the most dangerous poisonous animal in the world's oceans. The venom of a sea wasp is enough to kill 60 people. Even after the death of a jellyfish, its tentacles can sting for more than two weeks. Jellyfish do not stop growing throughout their lives. Large concentrations of jellyfish are called “swarms” or “blooms.” Some species of jellyfish are eaten in East Asia, considered a “delicacy.” Jellyfish don't have a brain respiratory systems s, circulatory, nervous and excretory systems.
The rainy season significantly reduces the number of jellyfish living in salt water bodies. Some female jellyfish can produce up to 45,000 larvae (planulae) per day.
Pink jellyfish from the Scyphozoan family was discovered quite recently, a little over 10 years ago, in the waters of the Gulf of Mexico and the Caribbean. Some individuals of this species reach up to 70 cm in diameter. Pink jellyfish can cause serious and painful burns, especially if a swimmer inadvertently ends up among a large concentration of these creatures.
Antarctic Diplulmaris- one of the species of jellyfish of the Ulmaridae family. This jellyfish was recently discovered in Antarctica, in the waters of the continental shelf. The Antarctic Diplulmaris is only 4 cm in diameter.
Flower cap jellyfish(lat. Olindias Formosa) is one of the types of hydroid jellyfish from the order Limnomedusae. Basically, these cute creatures live off the southern coast of Japan. Feature- motionless hovering near the bottom in shallow water. The diameter of the “flower cap” usually does not exceed 7.5 cm. The tentacles of the jellyfish are located not only along the edge of the dome, but also over its entire surface, which is not at all typical for other species. A flower cap burn is not fatal, but is quite painful and can lead to severe allergic reactions.
Purple striped jellyfish(lat. Chrysaora Colorata) from the class Scyphozoa is found only near the coast of California. This rather large jellyfish reaches 70 cm in diameter, the length of the tentacles is about 5 meters. A characteristic feature is the striped pattern on the dome. In adults it has a bright purple color, in juveniles it is pink. Purple-striped jellyfish usually live alone or in small groups, unlike most other species of jellyfish, which often form huge colonies. The Chrysaora Colorata burn is quite painful, but not fatal to humans.
Giant Nomura jellyfish(Latin: Nemopilema nomurai) is a species of scyphoid jellyfish from the order Cornerotae. This species predominantly inhabits the East China and Yellow Seas. The size of individuals of this species is truly impressive! They can reach up to 2 meters in diameter and weigh about 200 kg. The name of the species was given in honor of Mr. Kan'ichi Nomura, director general of fisheries in Fukui Prefecture. In early 1921, Mr. Nomura first collected and studied a previously unknown species of jellyfish. Currently, the number of Nomura jellyfish in the world is growing. Possible reasons population growth, scientists believe climate change, overexploitation water resources and pollution environment. In 2009, a 10-ton fishing trawler capsized in Tokyo Bay with three crew members trying to remove nets overflowing with dozens of Nomura jellyfish.
Tiburonia granrojo- a little-studied species of jellyfish from the Ulmáridos family, discovered by MBARI (Monterey Bay Aquarium Research Institute) only in 2003. It lives at depths between 600 and 1500 meters in Hawaii, the Gulf of California and Japan. Thanks to its rich dark red color, this species of jellyfish has earned the nickname Big Red. The great red jellyfish is one of the largest species of jellyfish, its diameter ranges from 60 to 90 cm. Currently, only 23 individuals of this red giant have been found and studied.
Pacific sea nettle(lat. Chrysaora fuscescens) - has a bright characteristic golden-brown color, due to which it is often kept in captivity (aquariums and oceanariums). The name of the jellyfish genus Chrysaora goes back to Greek mythology. Chrysaor is the son of Poseidon and Medusa the Gorgon, his name translated means “he who has golden weapons.” IN wildlife Sea nettles are found in the Pacific Ocean from Canada to Mexico. The diameter of the jellyfish's dome can reach more than 1 meter, but more often no more than 50 cm, the length of the tentacles is 3-4 meters. The tentacles of the jellyfish are very thin, so the burn looks like a bright red welt, similar to a blow from a whip. Although victims experience severe pain and burning, going to a medical facility is usually not necessary. You can neutralize the effects of jellyfish toxins and relieve pain with vinegar or citric acid.
Portuguese man of war(lat. Physalia physalis) is a bright and very toxic representative of colonial hydroids from the order of siphonophores. It is most common in tropical and subtropical regions of the Pacific and Indian Oceans and the North Atlantic Ocean. Recently, there has been a significant increase in the number of this species. Since 1989, physalia has appeared in the Mediterranean Sea, for the first time off the coast of Africa, then Corsica, and in 2010 it was discovered off the coast of Malta. In the period 2009-2010, cases of physalia appearing off the coasts of Ireland and Florida were recorded. Entire flotillas of Portuguese man-of-war can now be found off the coast of Guyana, Colombia, Jamaica, Venezuela, Australia and New Zealand. In fact, the Portuguese man-of-war is not a single jellyfish, since it is a whole colony of polypoid and medusoid individuals united under one “roof”. The tentacles of this unusual organism, when extended, can reach up to 50 meters in length. A Man of Portugal burn is comparable in toxicity to a poisonous snake bite. For burns, it is necessary to treat the affected area with 3-5% vinegar in order to prevent the release of poison from the stinging cells remaining in the wound. Only in rare cases do physalia burns lead to death. The Man of Portugal is especially dangerous for children, the elderly and allergy sufferers. Be extremely careful with this type of jellyfish.
Cephea cephea or the so-called "soft" jellyfish is widespread throughout the Indo-Pacific region, including the Red Sea. This large jellyfish can reach up to 50 cm in diameter.
Aurelia eared(lat. Aurelia aurita) is a scyphoid jellyfish from the order of discomedusae. Widely distributed in the coastal waters of tropical and temperate seas. In particular, the Mediterranean and Black Seas. The diameter of the aurelia dome can reach up to 40 cm. The color is pinkish-violet, the body is almost transparent. Until recently, this type of jellyfish was not considered dangerous to humans. However, there have been several recent cases of severe burns in the Gulf of Mexico. It is believed that in the waters of the Black Sea, aurelia does not pose a serious danger to humans.
Australian jellyfish or sea wasp (lat. Chironex fleckeri) from the class of box jellyfish - the most dangerous deadly animal in the world's oceans. The main habitats are the coasts of northern Australia and Indonesia. The sea wasp is one of the largest species of box jellyfish; the diameter of its dome can reach up to 20-30 cm. Its pale blue color and almost complete transparency make it especially dangerous for swimmers, since it is not easy to notice in the water. The tentacles of a jellyfish are densely covered with stinging cells containing extremely strong poison. Burns caused by box jellyfish cause severe excruciating pain and in some cases can lead to rapid death. The venom of the sea wasp simultaneously affects the heart, nervous system and skin. Moreover, the neurotoxic venom of a jellyfish acts much faster than the venom of any snake or spider. Cases have been recorded where death occurred within 4 minutes of contact. First aid for a sea wasp burn consists of immediately treating the affected area with vinegar, removing tentacles stuck to the skin (remove only with protected hands or tweezers!) and immediate treatment medical institution, as administration of antitoxic serum may be required. The Australian jellyfish is the most dangerous jellyfish in the world!
Ctenophores(Latin Ctenophora) are jellyfish-like organisms that live in sea waters almost all over the world. Distinctive feature of all ctenophores - a kind of “combs”, groups of fins-cilia, used by this species for swimming. The sizes of Ctenophora range from a few millimeters to 1.5 meters. Among ctenophores, there are many deep-sea species capable of bioluminescence.
Aequorea Victoria or "crystal" jellyfish - a bioluminescent jellyfish from the order of hydromedusae. Widely distributed along the North American west coast Pacific Ocean, from the Bering Sea to Southern California.
Australian spotted jellyfish(lat. Phyllorhiza punctata) belongs to the family of pelagic jellyfish. Its main habitat is the southern Pacific Ocean. The usual size of the dome of the spotted Australian jellyfish is up to 40 cm, but in the waters of the Persian and Mexican Gulfs it reaches 70 cm. The Australian jellyfish is not dangerous to humans. However, to neutralize the poison, you should resort to a proven method - treat the skin with vinegar or citric acid in order to prevent possible allergic reactions. Recently, a massive proliferation of Australian jellyfish has been recorded, which can pose a serious threat to commercial fish populations. Feeding on eggs and fry, they pass up to 15,000 liters of water per day through their tentacles and swallow huge amounts of plankton and other marine life.
Mediterranean jellyfish Cassiopeia can reach up to 30 cm in diameter. Spends most of its time in shallow water, basking in the sun's rays.
Hairy cyanea or Lion's mane jellyfish (lat. Cyanea capillata, Cyanea arctica) is a large jellyfish from the order of disc jellyfish. The species is distributed in all northern seas of the Pacific and Atlantic oceans, living near the coast in surface layers of water. The bell of the Arctic cyanea (a subspecies of the hairy cyanea) can reach up to 2 meters in diameter, and the length of the tentacles is up to 33 meters. Lion's mane is generally considered a moderately stinging jellyfish. The burns it inflicts are quite painful, and the toxins contained in the poison can cause a severe allergic reaction. However, the poison of this jellyfish is not fatal to humans.
Jellyfish Chrysaora Achlyos- one of the largest species of scyphoid jellyfish. The bell size is approximately 1 m in diameter, the tentacles can reach up to 6 m in length. It has the ability of a chameleon - changing color from bright red to black.
A new species of transparent jellyfish discovered in Antarctica. Its diameter is about 2.5 cm
Jellyfish
Jellyfish are mysterious and incredibly beautiful inhabitants of the seas and oceans of our planet. Meeting them can be fatal for a person, however, people always strive to explore them and observe their lives. They are one of the most ancient inhabitants of the Earth, which have not yet been fully studied, in particular due to the fact that some jellyfish live at depths of up to 10 thousand meters. In some countries, particularly Japan and China, jellyfish are eaten by first marinating the body of the jellyfish without tentacles.
In most cases, jellyfish swim freely in the water column, but some hydroid polyps have sessile medusoid individuals that do not separate from the colony (in the extreme case, like in the freshwater polyp Hydra, the medusoid generation is completely lost and gametes develop directly on the polyp). It is also believed that medusoid individuals are constantly present in the colony of some siphonophores.
Jellyfish can live at a depth of about 10,000 m. These are one of the most ancient inhabitants of our planet. Scientists still know very little about jellyfish, in particular how a creature without a brain, but with eyes, can navigate in pitch darkness and actively hunt.
The poison contained in the stinging cells of a number of jellyfish is dangerous to humans. The most famous in this regard are the sea wasp box jellyfish (Chironex fleckeri Southcott, 1956), which lives near the northern coast of Australia and in the waters of Southeast Asia, and the cross hydrojellyfish (Gonionemus vertens Agassiz, 1862), which lives in the northern part of the Pacific Ocean. The sea wasp's venom is deadly. The famous "Man of Portugal", also known for the potency of its venom, is not a jellyfish, but a siphonophore.
Jellyfish bodies
Jellyfish are perhaps the most fascinating creatures in the world's oceans.
There are usually four to eight mouth lobes that protrude from the edges of the jellyfish's bell. The main purpose of these oral lobes is to help transport food to the jellyfish's mouth. Many varieties of jellyfish also have groups of tentacles emerging from the edges of the bell. These tentacles have thousands of venom cells that fill the nematocysts and are mainly used to sting and paralyze prey. These tentacles are also useful for stinging potential predators and protecting themselves. The jellyfish is not capable of any horizontal movement. It completely depends on the flow of water and winds on the surface of the water. However, the jellyfish's bell allows it to control its vertical movements.
Pumping or pushing water out from under you. The size of a jellyfish's bell varies depending on the species. It can range from a few centimeters to several feet in diameter. The largest known jellyfish had a bell that was 7 feet in diameter. The color and shape of a jellyfish's bell also differs between species, and can cover a very wide range in shades and shapes.
Structural features of jellyfish Jellyfish, if you ignore some deviations in the organization digestive system
, have the same structure as polyps, except that they are strongly flattened in a plane that is perpendicular to the main axis of the body.
The outer convex side of the bell or umbrella of a jellyfish is called exumbrella, and the inner concave side is called subumbrella. In the middle of the subumbrella there is a longer oral stalk with a mouth at the free end. The mouth is the gateway to the digestive cavity, which consists of a central stomach and radial canals diverging to the edges of the umbrella, their number is equal to or a multiple of four. In the thickness of the mesoglea they are connected by a continuous endodermal plate. A ring channel runs along the edge of the umbrella, through which all radial channels communicate with each other. The stomach and canals are the gastrovascular (i.e., intestinal-vascular) system.
A thin ring-shaped muscular membrane is attached to the free edge of the umbrella, which narrows the entrance to the bell cavity. It is called a sail, it is a characteristic difference between hydroid jellyfish and scyphoid jellyfish. The sail also helps with the movement of jellyfish. Along the edge of the umbrella there are tentacles, which, like radial channels, are most often multiples Four. Correct location
Scientists do not give a definite answer to the question of how long jellyfish live. Many agree that life cycle These animals are short-lived and the lifespan of most species ranges 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.
These tentacles consist of string cells that contain poison and are therefore directly intended for hunting. It is interesting that even after death, jellyfish are able to sting for another fortnight. Some species can be deadly even to humans. For example, the animal known as the “Sea Wasp” is considered the most dangerous poisonous animal in the world’s oceans: scientists claim that its poison is enough to poison sixty people in a few minutes.
The outer part of the body is smooth and convex, while the lower part resembles a bag. In the center of the lower part there is a mouth: in some jellyfish it looks like a tube, in others it is short and wide, in others it resembles short clubs. This hole also serves to remove food debris.
These animals grow throughout their lives, and their size largely depends on the species: among them there are very small ones, no more than a few millimeters, and there are also huge ones, the body size of which exceeds two meters, and together with the tentacles - all thirty ( for example, the largest jellyfish in the world's oceans, Cyanea, which lives in the North-West Atlantic, has a body size of more than 2 m, and with tentacles - almost forty).
Despite the fact that these marine animals lack brains and sensory organs, they have light-sensitive cells that act as eyes, thanks to which these organisms are able to distinguish darkness from light (they, however, are not able to see objects). Interestingly, some specimens glow in the dark, with species living at great depths having a red light, and those living closer to the surface having a blue light.
Since these animals are primitive organisms, they consist of only two layers, connected 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 still do not completely succumb to water flows and, although slowly, move, using the current and the thin muscle fibers of their body: contracting, they fold the body of the jellyfish like an umbrella - and the water that is in the lower part of the animal is sharply pushed out.
As a result, a strong jet is formed, pushing the animal forward. Therefore these sea creatures always move in the direction opposite to the mouth. They are helped to determine where exactly they need to move by the balance organs located on the tentacles.
Regeneration
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, it is possible both sexually (they are heterosexual) and vegetative propagation. The first involves several stages:
- In these animals, the sex cells mature in the gonads;
- After the eggs and sperm mature, they come out through the mouth and are fertilized, resulting in the appearance of a jellyfish larva - a planula;
- After some time, the planula settles to the bottom and attaches itself to something, after which a polyp appears on the basis of the planula, which reproduces by budding: on it, layering on top of each other, daughter organisms are formed;
- After some time, they peel off and float away, revealing themselves as a newly born jellyfish.
The reproduction of some species differs somewhat from this pattern. For example, the pelagic jellyfish does not have a polyp stage at all - the cubs appear directly from the larva. But bougainvillea jellyfish can be said to be born, since polyps are formed directly in the gonads, without separating from the adults, without any intermediate stages.
Nutrition
These amazing animals are the most numerous predators on our planet. They feed mainly on plankton: fry, small crustaceans, and fish eggs. Larger specimens often catch small fish and smaller relatives.
Thus, jellyfish see almost nothing and do not have any sense organs; they hunt with the help of scratching tentacles, which, having sensed the touch of edible food on them, instantly inject poison into it, which paralyzes the victim, after which the jellyfish eats it. There are two more options for catching food (much depends on the type of jellyfish): the first is that the prey sticks to the tentacles, the second is that it gets entangled in them.
Classification
There are the following types of jellyfish, differing from each other in structure.
Hydromedusa
Hydroid jellyfish are transparent, small in size (from 1 mm to 3 cm), four tentacles and a long tube-shaped mouth are attached to the body. Among the prominent representatives of hydromedusas is the jellyfish Turritopsis nutricula: the only creature discovered by people about which scientists have declared that it is immortal.
Having reached maturity, it sinks to the bottom of the sea, transforming into a polyp, on which new formations are formed, from which new jellyfish subsequently arise.
This process is repeated more than once, which means that it is constantly reborn, and can die only if it is eaten by some predator. Like these ones Interesting Facts Scientists recently told the world about jellyfish.
Scyphojellyfish
Scyphoid jellyfish have a more complex structure compared to hydromedusae: they are larger than representatives of other species - the largest jellyfish in the world, the Cyanea jellyfish, belongs precisely to this class. At approximately 37 meters long, this giant jellyfish is one of the longest animals on Earth. Therefore, she eats a lot: during her life, the largest jellyfish eats about 15 thousand fish.
Scyphojellyfish have a more developed nervous and muscular system, a mouth surrounded by a huge number of stinging and tactile cells, and a stomach divided into chambers.
Like all jellyfish, these animals are predators, but deep-sea animals also feed on dead organisms. The touch of a scyphoid jellyfish to a person is quite painful (the feeling as if bitten by a wasp), and a mark resembling a burn often remains at the point of contact. Its bite can also cause an allergic reaction or even painful shock. Having seen this animal, it is advisable not to take risks and, when swimming past, not to touch it.
Some of the most striking specimens of this species, in addition to the Cyanea jellyfish, are also the Aurelia jellyfish (the most typical representative) and the Golden jellyfish - an animal that can only be seen on the Rocky Islands archipelago in Palau.
The golden jellyfish is notable for the fact that, unlike its relatives, who live only in the seas, it lives in Jellyfish Lake, which is connected to the ocean by underground tunnels and is filled with slightly salted water. Representatives of this species also differ from marine specimens in that they completely lack pigment spots, have no stinging tentacles, and no tentacles that surround the mouth.
Although the golden jellyfish is a scyphojellyfish, over many years it has turned into a completely different species that does not pose a danger to humans, since it has significantly lost its stinging ability. An interesting fact is that the Golden Jellyfish began to grow green algae on its body, from which it receives part of its nutrition. The Golden Jellyfish, like its marine relatives, feeds on plankton and has not lost the ability to migrate - in the morning it swims to the east coast, in the evening it swims to the west.
Box jellyfish
Box jellyfish have a more advanced nervous system compared to other representatives of the cnidarian class. They are the fastest of all jellyfish (able to reach speeds of up to 6 m/min) and can easily change the direction of their movement. They are also the most dangerous representatives of jellyfish for humans: the bites of some representatives of box jellyfish can be fatal.
The most poisonous jellyfish in the world belongs to this species, lives near the Australian coast and is called the Box Jellyfish or Sea Wasp: its poison can kill a person in just a few minutes. This wasp is almost transparent, of a pale blue hue, which is why it is difficult to notice on the water, which means it is easier to stumble upon it.
The Sea Wasp is the largest jellyfish in its class - its body is the size of a basketball. When a sea wasp simply swims, its tentacles are reduced to 15 cm in length and are almost invisible. But when the animal hunts, they stretch up to three meters. Sea Wasps feed mainly on shrimp and small fish, and they themselves are caught and eaten sea turtles- the only animals on our planet that are insensitive to the poison of some of the most dangerous creatures on Earth.
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 are classified as coral polyps, and the other half include hydroids, scyphoids, and box jellyfish (the group of animals 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, 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. Then, the planula attaches to a solid surface ( sea bottom 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 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? WITH scientific point In visual terms, a group of jellyfish consisting of hundreds or even thousands of individual individuals is called a “swarm”. Marine biologists have noticed that large aggregations of jellyfish are being observed more and more often, and may serve as an indicator of sea pollution or global warming. Jellyfish swarms tend to form in warm water, and jellyfish are able to thrive in anoxic marine conditions that are unsuitable for other invertebrates of their size.
