The characteristic appearance of which is given by a convex umbrella and massive oral lobes with numerous processes. Unlike other scyphoid jellyfish, Cornerot jellyfish lack the corolla of tentacleslocated along the edge of the umbrella. About 80 species are known. Some representatives (for example, Nemopilema nomurai) during outbreaks are capable of creating difficulties for fisheries.
| Cornerots | ||||||||||
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| Stomolophus meleagris |
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Rhizostomeae Cuvier, |
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Reproduction and life cycle
The usual life cycle of cornerots is metagenesis - the alternation of asexual generation (polyps) and sexual generation (jellyfish).
Cornerot polyps ( scyphistomas) have a goblet shape, small size and lead a bottom lifestyle. Their reproduction is carried out by lateral budding (in this case, other polyps are formed) or by strobilation, as a result of which planktonic stages are formed - ethers, which subsequently develop into jellyfish.
Jellyfish can reach much larger sizes (over 2 m in diameter) and most of the representatives live in the water column. As a result of external insemination, a planula larva is formed from the egg, which settles to the bottom and transforms into a scyphistoma.
Jellyfish
Structure
The primary mouth opening in the jellyfish of most cornerots is overgrown. Inside the umbrella there is a voluminous, septless stomach, at the bottom of which there are four gonads. A dense irregular network of thin gastrovascular channels extends from the stomach cavity, which penetrate the entire umbrella and enter the oral lobes. In forms lacking a primary mouth, the canals of the oral lobes break outward and form numerous secondary oral openings.
The oral lobes, which in many cornerots fuse into a single formation, have a characteristic process structure that gave the order its name. Their epidermis is rich in stinging cells, with which the cornerots immobilize the prey. Trapping tentacles, common for other jellyfish, are absent along the edge of the umbrella.
Lifestyle
Planktonic organisms act as the main source of food, which jellyfish catch from the jet stream that occurs when the umbrella contracts and swallow through the secondary oral openings on the oral lobes. There is evidence that Cornerots are capable of external digestion, due to which they are able to feed on larger organisms, such as fish.
Movement
Outwardly, the "hands" resemble the roots and stems of marine plants. Hence its so unusual name - cornerot. There are no tentacles at all. Cornerot jellyfish are excellent swimmers. Unlike their relatives, they can move in any direction.
Medusa Cornerot
Russian name cornerot- literal translation of the Latin name of the jellyfish Rhizostoma(from Greek. rhiza- root and stoma- mouth). This jellyfish is common in the Black and Azov Seas, and can even be found in desalinated Black Sea bays and estuaries. Outside of Russia, the Cornerot lives in the Mediterranean Sea and along the Atlantic coast of Europe from the Strait of Gibraltar to the Lofoten Islands off the northern coast of Norway.
Cornerots are very beautiful and perfectly swimming jellyfish. Their highly convex white umbrella with a slight yellowish or greenish tint looks great against the blue of sea water. And along the very edge of the umbrella, like a fine finish, there is a bright purple, blue or blue stripe (see textbook drawing, p. 110).
A feature of the cornerot jellyfish is the absence of tentacles along the edge of the umbrella. Catching prey is carried out exclusively by oral lobes.
The edges of the mouth of the cornerots are elongated into four lobes, which can be forked or even strongly branched. The skin folds of these numerous lobes grow together in many places and form peculiar tubes. As a result, the mouth opening turns out to be completely overgrown and surrounded by many processes hanging down and resembling the roots of a plant. Indeed, a real cornerot. The overgrowth of the mouth led to a change in the lifestyle of the jellyfish. For her, large food became inaccessible, and the jellyfish switched to feeding on plankton. Small organisms suspended in sea water easily pass through the pores in the oral lobes and then enter the pharynx and digestive cavity through special channels.
The diameter of the cornerot bell can reach 60 cm. The digestive cavity inside it is represented by 16 radial canals radiating from the stomach to the edges of the umbrella. Approximately in the middle of the length, all channels are interconnected by an annular channel. Thus, the entire digestive system is closed, there is a single opening - the mouth. Through this hole, undigested food residues are also removed.
A feature of the life cycle of the cornerot is the absence of a polyp stage. At least the polypoid stage of this species has not yet been described by scientists.
Some types of cornerots can have more than one and a half hundred "roots". Such, for example, are edible jellyfish living off the coast of Japan and China. ropilema with an umbrella diameter of up to 20 cm. Specially salted, these jellyfish are known in East Asia under the name "crystal meat". They are served as a condiment to other dishes.
Scyphoid jellyfish: Aurelia, Cyanea, Cornerot
Scyphoid - intestinal, specialized for a planktonic lifestyle. Most of the life cycle takes place in the form of swimming jellyfish, the polyp phase is short or absent.
Scyphoid jellyfish have the same body plan as hydroid jellyfish. Unlike hydroid jellyfish, scyphoid jellyfish have: 1) larger sizes, 2) a highly developed mesoglea, 3) a more developed nervous system with eight isolated ganglia, 4) endodermal gonads, 5) a stomach divided into chambers. The mode of locomotion is "reactive", but since scyphoids do not have a "sail", locomotion is achieved by shortening the walls of the umbrella. Along the edge of the umbrella are complex sense organs - ropalia. Each ropalia contains an "olfactory fossa", an organ of balance and stimulation of the movement of the umbrella - statocysts, a light-sensitive eye. Scyphoid jellyfish are predators, but deep-sea species feed on dead organisms.
rice. 1.
1 - adult, 2 - egg,
3 - planula, 4 - scyphistoma,
5 - strobila, 6 - ether.
Aurelia (Aurelia aurita)(Fig. 1) - one of the most common jellyfish. Small tentacles are located along the edge of the umbrella. On the concave side in the center of the umbrella on a short stalk is a mouth. The edges of the mouth are elongated into four oral lobes. Stinging cells are located on the tentacles and oral lobes. The stomach has four pockets in which there are gastric filaments that increase the digestive surface. Eight non-branching and eight branching radial canals depart from the pockets. The radial channels flow into the annular channel. Through non-branching channels, food moves from the stomach to the annular channel, through branching ones - in the opposite direction. Along the edge of the umbrella are eight ganglia (clusters of nerve cells), above them - eight ropalia. Ropalia is a shortened tentacle, inside of which there is one statocyst, and on the sides there are two eyes. Olfactory pits are located on adjacent shortened tentacles. The eyes are photosensitive.
rice. 2. cyanea
(Cyanea arctica)
Jellyfish are dioecious animals. Gonads are formed in the endoderm of the pockets of the stomach, have a horseshoe shape. Mature sex cells are excreted through the mouth of the jellyfish. Fertilization is external. The eggs develop in the folds of the oral lobes. A planula larva develops inside the egg. The planula leaves the mother's body. After swimming for some time, the planula sinks to the bottom and turns into a single polyp - scyphist. The scyphistoma reproduces by budding, similar to that of the hydra. After some time, the scyphistoma transforms into a strobilus, while the tentacles of the scyphistoma shorten, and transverse constrictions appear on the body. The process of transverse fission is called strobilation. By strobilation, young jellyfish - ethers - are separated from the strobila. Esters gradually turn into adult jellyfish.
rice. 3. Cornerot
(Rhizostoma pulmo)
Inhabits the Arctic seas. It is the largest jellyfish: the diameter of the umbrella can reach 2 m, the length of the tentacles is 30 m (Fig. 2). Cyanea is brightly colored, the poison of stinging capsules is dangerous for humans.
It does not have tentacles along the edges of the umbrella. The oral lobes bifurcate, their lateral sides form numerous folds that grow together. The ends of the oral lobes end in eight root-like outgrowths, from which the jellyfish takes its name (Fig. 3). The mouth of adult Cornerots is overgrown, food enters through numerous small openings in the folds of the oral lobes. It feeds on small planktonic organisms. Found in the Black Sea.
Ropilema edible (Rhopilema esculenta) along with aurelia is eaten in China and Japan. Ropilema resembles the Black Sea cornerot, differs from it in the yellowish or reddish color of the oral lobes and the presence of a large number of finger-like outgrowths. The mesoglea of the umbrella is used for food.
Cornerot jellyfish (Rhizostoma pulmo) is the largest jellyfish in the Black and Mediterranean Seas. Medusa belongs to the order Cornerota (lat. Rhizostomeae) and can reach 50-60 cm in diameter and weigh 10 kg.
This pelagic species is widely distributed in the Atlantic Ocean, the eastern Mediterranean (especially along the Adriatic coast) and the Black Sea.
A convex umbrella and massive oral lobes with numerous processes give the jellyfish a characteristic appearance. Poisonous stinging cells are located on lacy lobes. The poison of Rhizostoma pulmo does not pose a serious danger to humans. Only in sensitive people, upon contact with the oral lobes, a strong irritation similar to a nettle burn may occur, which disappears within a short time. This is probably why the jellyfish is also called sea nettle, zhigalka, zhguchka.
The usual life cycle of cornerots is metagenesis - the alternation of asexual generation (polyps) and sexual generation (jellyfish).
Cornerot polyps (scyphistomas) are goblet-shaped, small in size and lead a bottom lifestyle. Their reproduction is carried out by lateral budding (in this case, other polyps are formed) or by strobilation, as a result of which planktonic stages are formed - ethers, which subsequently develop into jellyfish.
As a result of external insemination, a planula larva is formed from the egg, which settles to the bottom and transforms into a scyphistoma.
The jellyfish's umbrella is constantly shrinking, and the animal actively moves, taking any position, but most often it swims on its side. When the cornerot wants to leave the surface, it does not stop moving, as other jellyfish do, in order to calmly drown, but turns its dome down and, continuing to contract rhythmically, confidently goes to the depths.
Cornerot is sensitive to changing weather conditions. For example, before a storm, jellyfish move away from the coast and sink to the bottom.
Cornerot helps fish fry survive in the sea, which hide under its umbrella from predators. Cornerot itself feeds exclusively on plankton, but no one eats cornerot in the sea. Scientists classify jellyfish as a food dead end, although jellyfish have been cooked in Japan, Korea, and China for over 1,700 years. They are recommended for high blood pressure and other diseases; they are a dietary product.
Even in the Middle Ages, diuretics and laxatives were made from cornerot. Jellyfish venom is now used to make medicines to treat lung diseases and regulate blood pressure.
Jellyfish are present in Japanese sushi recipes. In Thailand they make noodles. In China, they have been salted or dried for more than 1,000 years (resulting in something like dried mushrooms or thin brown pancakes). In 2006, during the mass reproduction of large jellyfish off the coast of Japan, these jelly-like creatures even went to the filling for pies, soups were cooked from them.
The mesoglea of the Cornerot umbrella contains 98.25% moisture and 1.75% dry matter, which includes 72.59% mineral and 27.41% organic matter, including 15.80% protein and 1.03% fat . Jellyfish protein is complete and contains 17 amino acids, including a complete set of essential ones.
Scientific classification:
Kingdom: Animals
Type: Cnidaria - Cnidaria (Hatschek, 1888)
Class: Scyphozoa - Scyphozoa (Gotte, 1887)
Detachment: Cornerotes - Rhizostomeae (Cuvier, 1799)
Suborder: Daktyliophorae
Family: Rhizostomatidae (Cuvier, 1799)
Genus: Rhizostoma (Cuvier, 1800)
View: Cornerot - Rhizostoma pulmo (Macri, 1778)
Water Over millions of years, these creatures have changed little. The most famous and dangerous is the Cornerot jellyfish, which can be found in the waters of the Black Sea. Thousands of tourists every year get burned when they meet these "cute" creatures.
Medusa Cornerot causes trouble to anyone who dares to touch her. This is one of the most dangerous representatives of its kind. It can be easily distinguished from relatives by a large spherical "cap", which reaches 150 cm in diameter, and a large outgrowth - the so-called tail. The Cornerot jellyfish, the photo of which you see in the article, feeds on plankton through the secondary mouth openings.
But there is evidence that the jellyfish can also absorb small fish, crustaceans, worms and other defenseless inhabitants of the ocean. This happens when the sea beauty manages to capture prey with root-like processes. Stinging threads hit the victim, immobilize it, and then with a stream of water it goes into the mouth. The poison, located in the root-like outgrowth, strikes the victim, paralyzing it.
Over millions of years, some species of fish have developed an instinct that allows them to swim in close proximity to a huge jellyfish, protecting themselves from marine predators in such a neighborhood. But the main task is to survive and not get caught in the tail of your "patron".
The name "cornerot" is quite justified. The fact is that this jellyfish does not have tentacles. Its mouth opening forms dense folds that stretch down and resemble a tail. In fact, these are mouth openings in the form of tubes, and a real mouth overgrows over time. The outer mouth openings resemble the thick roots of a plant, hence the eloquent name.
Cornerot is very common in this jellyfish can be found both at depth and near the coast. Due to the proximity to beaches and vacationers, unsuspecting children and adults become victims of burns.
Medusa Cornerot looks very exotic in the water. She moves slowly, does not hide at all and does not try to slip away. In this regard, many have a desire to catch or touch it. leads to quite tangible consequences - skin burns.
Not fatal to the human body, but causes a severe allergic reaction. At the same time, pain is aggravated in salt water. The pain is about the same as with a nettle burn.
During a storm, all jellyfish from the shore are carried to the bottom. Bathing after it will save you from meeting with these marine inhabitants, however, not for long. An interesting fact was noticed by scientists, as well as ordinary fishermen: the Cornerot jellyfish disappears from view a few hours before the start of the storm. Feeling the vibrations of the ocean, jellyfish fold their umbrellas and go to the bottom. Along with them, small fish and shrimp, which swim under their dome, disappear. Science still does not know how these creatures anticipate the storm. But their disappearance is a sure sign that bad weather is approaching. And vice versa, in calm, serene weather, the population of "burning" beauties in coastal waters is steadily growing. You can avoid trouble from meeting them if you bathe with caution.
