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 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 of 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 3m long, the sea wasp prowls the waters off Australia and Southeast Asia and has killed at least 60 people 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? Scientifically, 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.
Jellyfish are amazing and very extraordinary creatures. Read and watch
Jellyfish are amazing and very extraordinary creatures, evoking a whole range of emotions from delight and admiration to disgust and fear. 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 650 million years. There is an incredible number of different species in nature, but even now the emergence of new ones, previously unknown to mankind, is being recorded.
Jellyfish washed up on the sand of Belmedie beach, Scotland
In fact, jellyfish or the medusoid generation are one of the phases of the life cycle of the cnidarians Medusozoa, which are usually divided into three species: 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.
Jellyfish at Shark Bay Manaday Reef Aquarium in Las Vegas, Nevada
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.
Jellyfish on display in Long Beach, California
Did you know? 10 interesting facts about jellyfish:
The world's largest jellyfish can reach 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 do not have a brain, respiratory system, circulatory, nervous or 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.
The most incredible and bizarre shapes
Aequorea Victoria or crystal jellyfish
Lilac sting
Elegant dance of jellyfish
Aurelia - “butterflies”
Medusa - crown
Eared aurelia (lat. Aurelia aurita) is a species of scyphoid from the order of disc jellyfish (Semaeostomeae)
glowing ctenophore
Pink jellyfish
The pink jellyfish from the Scyphozoan family was discovered quite recently, just over 10 years ago, in the waters of the Gulf of Mexico and the Caribbean. Some individuals of this species reach 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
Antarctic Diplulmaris is one of the species of jellyfish of the family Ulmaridae. This jellyfish was recently discovered in Antarctica, in the waters of the continental shelf. The Antarctic Diplulmaris is only 4 cm in diameter.
Colony of jellyfish
Aurelia aurita or moon jellyfish
Pacific sea nettle (Chrysaora fuscescens)
Flower cap jellyfish (Olindias formosa)
Flower cap jellyfish (lat. Olindias Formosa) is one of the species of hydroid jellyfish from the order Limnomedusae. Basically, these cute creatures live off the southern coast of Japan. A characteristic feature is 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.
Scyphoid jellyfish rhizostoma (Rhizostoma pulmo) or cornet
Incredible bioluminescent jellyfish
Jellyfish - an inhabitant of the coast of the Federated States of Micronesia
Purple-banded jellyfish (Chrysaora colorata)
The 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.
Pelagia Noctiluca, known in Europe as "lilac sting"
Giant Nomura jellyfish (Nemopilema nomurai)
Giant Nomura jellyfish (lat. 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 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. Scientists believe climate change, overexploitation of water resources and environmental pollution are possible reasons for the population increase.
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.
Great red jellyfish (Tiburonia granrojo)
Medusa cannonball
The cannonball jellyfish lives along the east coast of the United States to Brazil. It got its name because of its unusual shape, perfectly smooth and round, like a cannonball. In Asian countries, these jellyfish are widely used in folk medicine. It is believed that they can cure lung disease, arthritis, and lower blood pressure.
Olindias formosa
This rare species of jellyfish is found off the coast of Brazil, Argentina, and Japan. Characteristic of these jellyfish is hovering at shallow depths. When the jellyfish is in this state, its tentacles are concentrated under the cap. Due to its small numbers, this species does not pose a danger to people, but we should not forget that they can leave very severe burns.
Portuguese man of war
This amazing creature differs from all jellyfish in that it consists of many jellyfish individuals. It has a gas bubble that floats on the surface of the water, allowing it to absorb air. The tentacles of the Portuguese man-of-war can reach 50 meters when extended.
Purple striped jellyfish
This type of jellyfish can be found in Monterrey Bay. They are not yet well studied. This jellyfish is quite large and can cause serious burns to humans. Stripes and rich colors appear in jellyfish as they age. Along with warm currents, the jellyfish can also migrate to the shores of Southern California. This was especially noticeable in 2012, when 130 people received burns from jellyfish (black sea nettle and purple striped one).
Mediterranean or jellyfish fried egg
This amazing creature really resembles a fried egg, or poached egg. Jellyfish live in the Mediterranean, Adriatic and Aegean Seas. Its important feature is that it can move independently without relying on waves.
Darth Vader or Narcomedusa
This type of jellyfish was discovered in the Arctic. This happened quite recently. In addition to such an interesting and at the same time terrifying appearance, the jellyfish has 4 tentacles and 12 stomach pouches. While swimming, the tentacles are pulled forward to better reach their prey.
Blue jellyfish
The blue jellyfish has very stinging tentacles. It has been discovered off the coast of Scotland, in the North Sea and in the Irish Sea. The average transverse diameter of this jellyfish is 15 centimeters. Color varies from dark blue to bright blue.
Porpit porpit
It's not really a jellyfish. This creature is more commonly known as the blue button. The porpet lives on the surface of the ocean and consists of two parts: a hard golden-brown float and hydroid colonies, which in appearance are very similar to the tentacles of a jellyfish. Porpita can easily be confused with a jellyfish.
Diplulmaris Antarctica
This magnificent creature lives in the deep waters of Antarctica and has four bright orange tentacles as well as white tentacles. The small white dots on the jellyfish are side-spreads. They live inside the jellyfish and sometimes even feed on it.
Black sea nettle
The black sea nettle is a giant bell-shaped jellyfish with a diameter of 3 feet. An adult can reach 5 meters and have 24 tentacles. This type of jellyfish was discovered in the waters of the Pacific Ocean. they are carnivores. They prefer larvae, plankton, and other jellyfish as food.
Many of those who vacationed at sea encountered jellyfish. This helped to realize the fact that they cannot be called ordinary and harmless creatures. Let's look at some interesting facts about jellyfish.
What does science know about jellyfish?
Researchers believe that jellyfish have been around for about 650 million years. They are found in all layers of each ocean. Various live in both salt and fresh water. Their primitive nervous system, which is located on the epidermis, allows them to perceive only smells and light. The nerve networks of jellyfish help them detect another organism through touch. These "animal plants" essentially do not have a brain or sensory organs. They do not have a developed respiratory system, but breathe through thin skin, which absorbs oxygen directly from the water.
While exploring interesting facts about jellyfish, scientists noticed that these creatures are able to positively influence people experiencing stress. For example, in Japan they breed jellyfish in special aquariums. Their smooth and measured movements act as a sedative. Although such pleasure is expensive and causes additional troubles, in general it is justified.
Jellyfish are more than 90 percent water. The venom from their tentacles is used as a raw material for drugs that regulate blood pressure and to treat respiratory diseases.
It was called the “Portuguese man-of-war” by some 18th-century sailors who liked to tell others about the jellyfish floating like a Portuguese warship of the Middle Ages. In fact, her body is very similar to this vessel.
Its official name is physalia, but it is not one organism. We are talking about a colony of jellyfish and polyps in different modifications, which interact very closely and therefore look like one creature. The poison of some types of physalia is deadly to humans. Most often, the habitats of the Portuguese man-of-war are limited to the subtropical parts of the Indian and Pacific Oceans, as well as the northern bays of the Atlantic Ocean. In more rare cases, they are carried by currents into the waters of the Caribbean and Mediterranean seas, to the shores of France and Great Britain, to the Hawaiian Islands and the Japanese archipelago.
These jellyfish often swim in huge groups of several thousand individuals in warm waters. The transparent and shiny jellyfish body rises above the water by about 15 centimeters and moves along a chaotic trajectory regardless of the wind. Those individuals that swim near the shore are often thrown onto land by powerful winds. In the warm season, physalia swims away from the shore, it moves with the current towards one of the earth's poles.
Distinctive features of physalia
Other interesting facts about this type of jellyfish concern their unique features. Physalia is one of two species that can glow red. The Portuguese warship also uses its air bag filled with nitrogen, carbon dioxide and oxygen as a sail. If a storm approaches, the jellyfish releases its bubble and goes under water. Small perches like to swim near its tentacles; they do not sense a toxic environment and have serious protection from enemies, as well as food particles. Perches attract other fish with their appearance, which become food for these invertebrates. This is such a symbiosis.
There are a considerable number of species known today as physalia. In the Mediterranean Sea alone, researchers have discovered about 20 species of Portuguese man-of-war.
Physalia jellyfish, interesting facts about reproduction
It is not known exactly how this jellyfish reproduces. However, scientific research has shown that they reproduce asexually, and in each colony there are polyps that are responsible for reproduction. In fact, they are the ones who create new colonies. Portuguese man-of-war are distinguished by the fact that they can reproduce continuously, which is why the number of nascent jellyfish in the waters of the oceans and seas is growing.
Another common version of the reproduction of physalia indicates that, when dying, the jellyfish leaves behind some organisms that exhibit sexual characteristics, after which new individuals are formed. This theory has not yet been proven.
About the tentacles of the Portuguese man-of-war
Regarding the jellyfish tentacles, the interesting facts are that their structure is unique. The “limbs” of jellyfish are equipped with a large number of capsules containing poison, the composition of which is similar to the poisonous substance of a cobra. Each of these small capsules is a hollow, twisted tube with fine hairs. If contact occurs between the tentacles and the fish, the fish will die due to the stinging mechanism. When a person receives a burn from this jellyfish, he experiences sharp pain, develops a feverish state, and has difficulty breathing.
The interesting facts about jellyfish don’t end there. The tentacles of these invertebrates can reach 30 meters in length. In addition, a person who is engaged in swimming, enjoying the process itself, will not always be able to see a bright blue-red bubble on the water and realize the danger that threatens him.
Irukandji jellyfish: interesting facts about the danger posed by it
This small jellyfish, which lives off the coast of Australia, produces toxic substances that are stronger than cobra venom. There are 10 types of Irukandji, 3 of which are deadly. The bite is almost imperceptible, but its consequences are a powerful heart attack, which in some cases can result in painful death. And all this can happen in just 20 minutes. Because these invertebrates are so small and virtually invisible, they can easily penetrate any barrier net that is designed for large creatures that pose a danger to swimmers and vacationers.
There are some other interesting facts about this species of jellyfish. Since fishermen often fell ill with a strange disease after each trip to the sea, they realized that the reason for this was contact with some kind of sea creature. The jellyfish was named after the Irukandji tribe. Over time, thanks to Dr. Barnes, it was finally possible to establish that the cause of the disease was contact with jellyfish. Although its size is quite small, its tentacles reach a length of 1 meter. The pain from the bite is so severe that it forces you to double over, is accompanied by severe sweating and vomiting, and your legs tremble violently.
conclusions
Although these invertebrate organisms are difficult to see in the water, regardless of their size, you still shouldn’t be careless and inattentive while swimming in the sea or walking along the shore - for the sake of your health. Many types for human health and life.
However, they also perform useful functions in their habitats and are used in medicine as raw materials for drugs. And who knows, maybe humanity will be able to get even more benefits from jellyfish.
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 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 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. At the edges of the umbrella there are clusters of 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 cardiovascular systems, and convulsive attacks occur.
