Mnemiopsis - the plague of the 21st century (9 photos). Life in the water column Ctenophore beroe in the Black Sea

Reading the invertebrate genome sea ​​creatures — ctenophores, Russian biologists and their foreign colleagues have questioned a number of provisions of the traditional theory of evolution.

They found that ctenophores are much older than sponges, which were considered the oldest inhabitants of the Earth. But most importantly, nervous system arose twice in the process of evolution. In ctenophores it is different than in all other animals, and works on the basis of different basic substances.

Russian and foreign scientists have created an international team to decipher the genome of ctenophores, invertebrate animals that live in the seas. The head of the laboratory of the Novosibirsk Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences became the head of one of the two groups Evgeniy Rogaev, the other is an American professor Leonid Moroz.

By teaming up, scientists obtained data that refuted the fundamental idea of ​​​​the evolution of living beings on Earth. The results of the study were published in the journal Nature.

Before the work of a team of biologists from Russia, the USA, Spain, Holland and England, not much was known about ctenophores. It is extremely difficult to study them, because it is worth extracting this mysterious creature from its usual environment, as its tissues dry out almost immediately, it is difficult to transport it to the laboratory.

Previously, ctenophores were classified as coelenterates, but they have long been identified as a separate type. They consist of a translucent jelly-like mass surrounded by epithelial layers. Their size, depending on the type, ranges from a few millimeters to one and a half meters. In total, more than 150 species of ctenophores are known. They got their name for a unique, very ancient type of movement - they move using ridges of cilia.

Ctenophores are predators, feeding on zooplankton, crustaceans, and sometimes fry. They started talking about them in Russia when, in the 80s of the last century, one of the species of ctenophores, Mnemiopsis, was accidentally introduced into the waters of the Black Sea. This almost led to disaster. The multiplied ctenophores ate zooplankton in such quantities that the fish had nothing to eat and their numbers sharply decreased. Commercial fishing is under threat. The problem was solved only after the people were resettled in the Black Sea natural enemies Mnemiopsis - predatory ctenophores of Beroe.

After analyzing the genome of the ctenophore Pleurobrachia bachei (sea gooseberry), scientists found that, most likely, ctenophores are the most ancient living creatures currently living on Earth.

They separated from other multicellular animals at a very early stage of evolution, about 600 million years ago. Before this, much more primitive sea sponges were considered the oldest. However, they do not have a nervous system, while ctenophores, which turned out to be older than them, do have one.

Ctenophores are predators, which means they need a nervous system. Without it, they would not be able to hunt: navigate in space and coordinate their movements. The brain of ctenophores is of the elementary type. What is most interesting is that this elementary brain is capable of regenerating when damaged in 3-4 days. And not just once, but many times. However, like other tissues of ctenophores, which quickly regenerate even with the most serious wounds.

Vladimir Alekseev, biologist, Ph.D. Sc., employee of the Institute of Cytology and Genetics SB RAS

The second conclusion that scientists made after studying the genome of ctenophores is that perhaps the nervous system arose not once, but twice in the process of evolution. Ctenophores acquired a nervous system independently of other animals.

The fact is that, as it turned out, it differs in the composition of neurotransmitters - chemical transmitters of the nerve signal at the synapses. Other animals “think” with the help of neurotransmitters such as serotonin, dopamine, norepinephrine, histamine, but ctenophores do not use them. There are no analogues to their nervous system on Earth; it is unique.

Everything from jellyfish to humans use the same substances to connect neurons, but ctenophores do not. In addition to the fact that they do not have neurons that secrete serotonin, they lack a number of receptor proteins typical of other animals, the so-called neurotransmitters, which are involved in the transmission of chemical signals between neurons. It is logical to assume that the ctenophores' nervous system and perhaps muscle specification evolved independently of other animals.

Evgeniy Rogaev, neurogeneticist, professor, head of the Center for Neurobiology and Brain Neurogenetics of the Institute of Cytology and Genetics SB RAS, head of laboratories at the Institute of General Genetics of the Russian Academy of Sciences and Medical school University of Massachusetts.

Until now, it was believed that in all representatives of the animal kingdom the nervous system developed along the same path: from the simplest nervous network to the human brain. Now this basic position will have to be reconsidered, as well as the classification of animals.

It turns out that from common ancestors The first to separate was the branch leading to ctenophores, then the branch of sponges, and only then the branch leading to coelenterates and bilaterally symmetrical animals, which include humans.

Some genes that the ctenophore has are unique; they are not found in other living creatures on Earth. In addition, surprising features of gene regulation were discovered in the sea gooseberry. It lacks microRNAs, small sequences of ribonucleic acid. All other animals have them, moreover, they play a very important role in the development and functioning of the body. However, the comb jelly somehow manages without them.

The fact that when analyzing the genome of the ctenophore and the work of its genes, it was revealed that they do not contain microRNAs and genes for some enzymes involved in the formation of RNA, this is surprising. MicroRNAs play vital role in the functioning of the body of all previously studied animals, but not in ctenophores. In all likelihood, they use other types of RNA that perform similar functions.

Evgeniy Rogaev, neurogeneticist, professor, head of the Center for Neurobiology and Neurogenetics of the Brain at the Institute of Cytology and Genetics SB RAS, head of laboratories at the Institute of General Genetics of the Russian Academy of Sciences and the University of Massachusetts Medical School

The results of the study of the genome of the sea gooseberry will change not only the fundamental understanding of scientists about the evolution of life on Earth, they may also have practical applications.

Expert opinion
David Abramovich, physiologist, Ph.D.,

- Like most basic research, sequencing the ctenophore genome will have practical benefits. Perhaps it will lead to the creation of new drugs or the development of new treatments. The fact that they use different molecules and mechanisms to transmit signals than other living beings can help in the treatment of brain diseases.

If we can use neurotransmitters that ctenophores use instead of standard ones, this could be a breakthrough. After all, a neurotransmitter such as dopamine, which ensures the transmission of nerve signals in all living creatures except ctenophores, is associated with Alzheimer’s and Parkinson’s diseases. If he can find an alternative, it will change everything. In addition, it is extremely promising to use molecules that ensure the regeneration of the nervous system of sea gooseberries.

Guess the riddle. Swims underwater, not a fish, consists of a jelly-like mass, but not a jellyfish, the most ancient animals on earth, but not dinosaurs. Not a specialist in the field marine fauna Anapa is having a hard time solving this puzzle. The site "My" will help you understand the most mysterious issues of our land and will introduce all our readers to a unique species called ctenophores. The beach areas of the resort are home to two unique and opposite species of ctenophores, Mnemiopsis and Beroe. Today you will learn a lot of interesting things about these strange creatures Oh.

Appearance

Externally, ctenophores look like jellyfish; their body consists of a jelly-like substance, which contains more than 90% water. Previously, strange creatures were considered jellyfish, but then they were identified as separate species, and it turned out not in vain.
Ctenophores get their name from the presence of swimming combs consisting of tiny cilia. Mnemiopsis has noticeable wings, while Beroe looks more like a floating pocket with a large mouth.

All ctenophores have longitudinal lines where light is refracted, creating the feeling of a rainbow. If it were not for the cheerful light music, which the diver immediately notices, then no one would pay attention to the transparent ctenophore.
The sizes of ctenophores that can be observed in Anapa are 5 or 7 centimeters long.

Habits

Combworms carry both female and male sex glands, in other words, they can change sex over time, and even fertilize their own eggs. Active reproduction begins when the water temperature in the Black Sea rises. The diet of Anapa ctenophore species varies. Mnemiopsis is an avid lover of zooplankton; per day it eats more plankton than it weighs itself. Beroe prefers its brother and actively devours Mnemiopsis, swallowing it whole. We will talk about this feature below.

It should be noted that ctenophores are not indigenous to the Black Sea waters of Anapa. Mnemiopsis was the first to settle in our area. In the 80s of the twentieth century, this seemingly harmless creature, brought by ships from America, undermined the ecosystem of an entire region. The ctenophore, which loves to eat more than required and has no enemies, ate more than half of the plankton. The decline in plankton has led to a reduction in the population of commercial fish and other animals that feed on small larvae. For ten whole years, Mnemiopsis ruled the sea until people introduced it to their enemy - Beroe. This floating stomach loves its lunch distant relative, which it absorbs into itself and slowly digests.

The arrival of the Beroe ctenophores helped stop the reproduction of the voracious invertebrate. Thanks to the invasion of Mnemiopsis, restoration of the original volume of plankton that has always lived in the Black Sea will no longer be possible.

Scientists began to closely study ctenophores when footprints of ancient species were found in shale excavations. It turned out that ctenophores are one of the oldest creatures that live on our earth; they have been on the planet for more than 500 million years!

Serious studies of the jelly-like creatures began, and after deciphering the genome, it became clear that the nervous system of the ctenophore has evolved twice and has a completely different structure than all animals on Earth. Research on these inconspicuous invertebrates has shaken the whole idea of ​​the evolution of creatures. Studying new neurotransmitters used by ctenophores may help treat diseases caused by diseases of the nervous system.

Where and when to see in Anapa

In Anapa, you can observe the life of ancient creatures during the summer holidays. There are more than enough ctenophores on sandy and pebble beaches. In order to get a good look at the underwater flights of sea rainbows, stock up on a snorkel and mask in advance. Unique invertebrates live at depths of one meter; you don’t need the skills of a professional diver.

Ctenophores are not jellyfish, don't even have them family ties, although it’s impossible to call them anything else. Externally, Mnemiopsis are light, transparent, with blade-like skirts and paddle plates. They do not have a brain, heart, or skeleton, but they do have a nervous system, an organ of balance, and the ability to luminesce.

According to the latest data from scientists, the ctenophore is one of the first living creatures on planet Earth. Previously it was believed that this title belongs to sea sponges - much more primitive creatures.

The Black Sea and the reservoirs of Ukraine are being colonized by new organisms that are not typical for our latitudes, which are destroying the traditional fauna of our waters. According to the Chairman of the Association of Fishermen of Ukraine Alexander Chistyakov, not so long ago Black Sea coast Predatory Pacific rapana appeared, which destroy native mussels and oysters.
Also, Mnemiopsis has penetrated into the Black Sea, which has won the lion's share of the food supply of planktivorous fish and destroys their eggs and larvae. The most affected party in this environmental disaster was the anchovy - one of the main commercial fish of the Black Sea - its numbers have sharply decreased. “Aliens” enter our seas with ballast water and on the bottoms of dry cargo ships from other seas and oceans of the world. A warm in winter the sea promotes their reproduction.
The same problem exists in the Dnieper-Bug estuary. It has been captured by jellyfish, Chinese shaggy crabs and even piranhas. The estuary has always been considered a fishing Mecca in the lower reaches of the Dnieper in the Kherson region. It is rich in bream, roach, pike perch, pike and giant carp. More than a dozen fishing cooperatives are engaged in fishing there. However, since the end of last year, it has become physically impossible to fish there - the nets are filled not with crucian carp and roach, but with jellyfish. In the spring they will destroy the larvae of valuable commercial fish species - bream, carp, ram, because for these fish the estuary is a common natural spawning ground.
“Environmentalists have long been sounding the alarm about aliens. It’s good that the heat-loving herbivorous subspecies of piranha Paku will disappear with the onset of cold weather. But species that adapt well to our conditions are increasingly entering our water bodies and are beginning to displace our native fish species. Last year, the arrival of a Chinese shaggy-armed crab in the Dnieper-Bug estuary, which first took root in the Black Sea and has now settled in the estuary, almost became a disaster,” says Chistyakov.
And the Ukrainian golden crucian carp was replaced in the Red Book of Ukraine by an alien with Far East – goldfish. Also a serious threat to our fish is the sunfish from North America, which has already settled in almost all reservoirs.

Mnemiopsis - a terrible threat to the Caspian Sea

Scientifically, this is called “biological invasion.” Plants or animals invade a foreign environment and begin to settle in there, thousands of kilometers from their homeland. In a new place they acclimatize and displace the “indigenous inhabitants”.
The problem of alien species has reached planetary proportions. “As an unwelcome by-product of globalization, alien species have detrimental impacts on ecosystems, human lives and economies around the world,” the message reads. Secretary General UN.
Mnemiopsis leidyi (lat.) - a comb jelly that lives in sea ​​water in warm regions and resembles a jellyfish. Externally, Mnemiopsis are light, transparent, with blade-like skirts and paddle plates. They do not have a brain, heart, or skeleton, but they do have a nervous system, an organ of balance, and the ability to luminesce. Mnemiopsis is a predator that feeds on zooplankton, eggs, and larvae of fish and mollusks. Shimmers in the light bright colors, at night gives the sea waves a yellowish luminescent glow. According to the latest data from scientists, the ctenophore may be one of the oldest living creatures on planet Earth.

Mnemiopsis leidyi is native to the Atlantic Ocean surrounding Florida, where it lived until recently. However, in our age of developed communications, the moment has come when Mnemiopsis moved to conquer other water territories.
In 1987, Mnemiopsis entered the waters of the Black Sea with the ballast waters of ships. In 2006, Mnemiopsis leidyi was first noticed in the North and Baltic Seas.
Mnemiopsis has many of the characteristics of an ideal invader. It is both a self-fertilizing hermaphrodite; it is an omnivore - consuming a wide range of food; it survives in a wide range of conditions environment with varying salinity from 3.4 to 75 ppm and temperatures from 1.3 ° C to 32 ° C; at optimal temperature(above 20° C) it develops very quickly, reaching its sexual maturity in 12 days; it also responds to increased concentration nutrients rapid growth and reproduction.
Moreover, there is a high resistance and low sensitivity of Mnemiopsis to various pollutants. This invader was even found in the waters of ports, in places where ships were moored, where water environment was contaminated with gasoline and oil. Ctenophore individuals different ages and sizes felt great in a mixture of water and petroleum products.

In the Black Sea, Mnemiopsis had no natural predators and began to multiply rapidly, devouring plankton, eggs and fish fry. IN favorable conditions The comb jelly can eat ten times its own weight per day. Depending on the amount of food, it can double in size per day and lay 8 thousand eggs per day. By 1989, the amount of food for fish had decreased by 30 times compared to the period 1978-1988.
Gradually increasing, the total biomass of the ctenophore population in the Black Sea reached about 1 billion tons in 1989, and its density in the southwestern part of the Black Sea was 4000-5000 grams per cubic meter of water. There was a time when this species accounted for 90% of the mass of all living organisms in the Black Sea.
The transparency of the water sharply decreased, since the destroyed zooplankton no longer ate small algae, in addition, this ctenophore secretes a colossal amount of mucus during its life. The Black Sea became like a muddy ctenophore soup. The number of fish that feed on plankton has fallen tenfold: anchovy, mackerel and sprat. Fishing losses amounted to several hundred million dollars. The Black Sea dolphins also found themselves on a starvation diet.
As already indicated, the reason for the massive development of these “invaders” was the lack of predators capable of controlling their numbers: no one ate Mnemiopsis. Ctenophores are considered to be “dead ends” of food chains: low content nutrients makes it unattractive for effective nutrition.
It would seem that the Black Sea is facing complete biological collapse. But in 1997 - 1999. A new ctenophore, Beroe ovata, is invading the Black Sea. Unlike Mnemiopsis, Beroe cannot digest zooplankton, eggs, jellyfish and fish fry and feeds exclusively on... the Mnemiopsis ctenophore! Beroe is not embarrassed by large prey specimens. It has no tentacles, but almost its entire body is one continuous throat. Beroe either pulls the mnemiopsis into itself gradually, or swallows it immediately through a wide open mouth, while the entire body of the predator swells. After 3-5 hours, the beroe digests the victim and can immediately swallow the next one. In the light, beroe has a yellowish-pink color, in the dark it becomes milky white.

The introduction and reproduction of Beroe led to a sharp decrease in the biomass of Mnemiopsis and, as a consequence, to an increase in zooplankton and fish larvae, and later in the fish stocks of the Black Sea.
In 1999, Mnemiopsis leidyi made its way into the Caspian Sea. The alarm about the sharp decline in the population of first sprat and then sturgeon was sounded in all Caspian states.
According to scientists, Mnemiopsis was most likely introduced through the Volga-Don Canal, through the ballast waters of ships or on uncleaned bottoms. During Soviet times, all transit ships were subjected to strict sanitary inspections in Astrakhan. With the decline in general control standards, the barriers to “illegal” entry into foreign waters by an uninvited alien have been essentially eliminated.
The first information about the appearance of Mnemiopsis leidyi in the Turkmen waters of the Caspian Sea was obtained by chance in the second half of September 1999, during the collection of material on the biology and ecology of Karabogazgol. From the oral report of the fishermen, the appearance of “jellyfish” in the Caspian Sea, in the bay area, which they had never seen here before, was noted.

During 1999-2000, a widespread distribution of Mnemiopsis began to be noted in the waters of the Middle and Southern Caspian Sea. Having found here suitable environmental and feeding conditions, the ctenophore not only colonized almost the entire water area of ​​the Caspian Sea, creating a powerful population with high numbers, but also began to influence the entire ecosystem of the sea. During the period of expeditionary work in the Caspian Sea in October 2000, a wide distribution of Mnemiopsis and its highest abundance along the western coast of the Caspian Sea were noted. The trawl and cone net for catching sprat caught ctenophores of different ages and sizes, but the fish required for analysis were practically not caught at these stations.
In February 2003, in the southern part of the Caspian Sea, the concentration of Mnemiopsis reached up to 320 specimens per cubic meter of water. In three years, its population grew so much that on moonlit nights the sea became phosphorescent.
It is with the vital activity of the ctenophore that scientists associate the mass death of the Caspian sprat in the summer of 2001. According to specialists from the Dagestan branch of the Caspian Research Institute of Fisheries, about 200 thousand tons of sprat died then, which was a fifth of its total in the Caspian basin. According to other sources, not 40%, but almost all sprat (at least 80% of the population) died in the Caspian Sea. The cause of the mass death of sprat was not disease, but real hunger.

Further up the food chain there was a mass death of the Caspian seal. In this case, first of all, the population lost all the expected offspring (animals that did not gain fat either did not reproduce or gave birth to weakened young, which soon died).
IN given time the sprat population decreased by an order of magnitude, and then there was a decrease in the number sturgeon fish. In addition, Mnemiopsis devours their eggs, preventing them from reproducing. It is predicted that the sturgeon catch will soon be in the hundreds.
Scientists from the Caspian states have been looking for ways to combat mnemiopsis for several years now. A number of experiments with the propagation of Beroe were carried out in laboratories in Russia and Iran. It was found that with increasing water temperature, the feeding intensity of Beroe increases sharply. Beroe still needs to adapt to the Caspian water, since the Caspian water has a different ionic composition and salinity than the Azov-Black Sea water.

Research has shown that beroe can live and grow intensively in the south of the Caspian Sea, with a salinity of 12-13 ppm. The Beroe feeding rate was quite high (100 or more percent of own weight body per day) at 21-26 degrees Celsius. Daily diet and the growth rate at 12.8 ppm was close to the values ​​characteristic of the Black Sea (where salinity reaches 18 ppm). Based on physiological data, confidence was expressed that Beroe can, just like in the Black Sea, intensively feed on Mnemiopsis and sharply reduce its numbers in the Caspian Sea.
For the first time in the world, Russian scientists have successfully adapted Beroe. The adaptation period takes 6-7 days. Beroe otava is caught in the Black Sea and delivered to the Caspian coast by road or air. During the adaptation period, individuals are brought to a sexually mature state and produce offspring. The resulting offspring live practically in Caspian water. The adaptation method is patented.
However, scientists disagree about the possibility of using beroe in the Caspian Sea. Some consider it an urgent issue to expand the range of release of adapted individuals of Beroe ovata into the waters of the Caspian Sea and the need for all Caspian states to join this fight. Others consider such activities futile. We can only hope that due to the differences natural conditions in the Caspian Sea, the harmful invader will not be able to enslave it completely and lead to a total catastrophe.

Representatives of the Ctenophore type have much in common with the others. But at the same time they have unique features, allowing them to be distinguished into a separate type (the rest of the coelenterates are combined into the type Cnidarians).

Ctenophores live in the seas. More than 100 of their species have been described, that is, they are not numerous animals in terms of the number of species. However, they are widespread in the seas, numerous in number of individuals, and quickly restore their numbers. So they cannot be called rare.

Ctenophores have one life form (neither a polyp nor a jellyfish). They are capable of active movement (in this respect they are closer to jellyfish). Most species swim in the water column, some lead a benthic (swim or crawl near the bottom) lifestyle.

Many people have bodies appearance looks like a slightly elongated and flattened translucent ball with two tentacles. However, there are ctenophores without tentacles. The body is soft (gelatinous), since ctenophores do not have a mineralized skeleton. Along the body, from the mouth opening to the point opposite it, there are eight rows of rowing plates, thanks to which the animal swims. Plastics consist of fused cilia of surface cells. Eyelashes reflect light, which is why they appear to glow.

Body size ranges from a few millimeters to 2 meters.

Ctenophores have radial symmetry, characteristic of all coelenterates. However, this symmetry is not complete, but two-ray. This means that only two planes can be drawn through the body of the ctenophore, dividing it into equal halves, and not many planes. The body is flattened, but the ventral and dorsal sides cannot be distinguished (they do not differ from each other). Therefore, one pair of symmetrical halves is conditionally left and right, the second pair is conditionally front and back.

Ctenophores swim mouth first. They are predators and feed on small crustaceans, fish and other coelenterates. They do not have stinging cells, but they do have cells that provide adhesion to the prey. There are species of ctenophores that assimilate (integrate into their body) the stinging cells of the jellyfish they eat.

The mouth opening opens into the pharynx. Next comes the flattened intestinal cavity, from which branching canals extend. In turn, closed processes extend from the canals; one goes up, the other goes down. Each pair of processes of one channel passes under the rowing plates.

WITH opposite side From the mouth there is an organ of balance that controls movement.

Ctenophores have a highly developed mesoglea, lying between the ectoderm and endoderm. Unlike other coelenterates, it contains quite a lot of cells. Therefore, the mesoglea of ​​ctenophores is sometimes already considered as mesoderm (third layer of cells).

Eat muscle cells. The nervous network has clusters of nerve cells under the cristal plates and the organ of balance.

Most are hermaphrodites. In some species, the production of eggs and sperm alternates over time. In others, individuals produce them simultaneously. After fertilization, a larva develops, most often leading a planktonic lifestyle. She gradually turns into an adult.

Jellyfish

Ctenophores are living rainbows