What is the name of the method of movement of a jellyfish? Interesting facts about jellyfish. Biophysics: jet motion in living nature

The logic of nature is the most accessible and most useful logic for children.

Konstantin Dmitrievich Ushinsky(03.03.1823–03.01.1871) - Russian teacher, founder of scientific pedagogy in Russia.

BIOPHYSICS: JET MOTION IN LIVING NATURE

I invite readers of the green pages to look into the fascinating world of biophysics and get to know the main principles of jet propulsion in wildlife. Today on the program: jellyfish cornermouth- the largest jellyfish in the Black Sea, scallops, enterprising rocker dragonfly larva, amazing the squid with its unrivaled jet engine and wonderful illustrations performed by a Soviet biologist and animal artist Kondakov Nikolai Nikolaevich.

A number of animals move in nature using the principle of jet propulsion, for example, jellyfish, scallops, dragonfly larvae, squid, octopus, cuttlefish... Let's get to know some of them better ;-)

The jet method of movement of jellyfish

Jellyfish are one of the most ancient and numerous predators on our planet! The body of a jellyfish is 98% water and is largely composed of hydrated connective tissue - mesoglea functioning like a skeleton. The basis of mesoglea is the protein collagen. The gelatinous and transparent body of the jellyfish is shaped like a bell or an umbrella (a few millimeters in diameter up to 2.5 m). Most jellyfish move in a reactive way, pushing water out of the umbrella cavity.

Jellyfish Cornerata(Rhizostomae), order of coelenterate animals of the scyphoid class. Jellyfish ( up to 65 cm in diameter) lacking marginal tentacles. The edges of the mouth are elongated into oral lobes with numerous folds that grow together to form many secondary oral openings. Touching the mouth blades may cause painful burns caused by the action of stinging cells. About 80 species; They live mainly in tropical, less often in temperate seas. In Russia - 2 types: Rhizostoma pulmo common in the Black and Azov Seas, Rhopilema asamushi found in the Sea of Japan.

Jet escape of scallops

Shellfish scallops, usually lying calmly on the bottom, when their main enemy approaches them - a delightfully slow, but extremely insidious predator - starfish- they sharply squeeze the doors of their sink, forcefully pushing water out of it. Thus using jet propulsion principle, they emerge and, continuing to open and close the shell, can swim a considerable distance. If for some reason the scallop does not have time to escape with its jet flight, the starfish wraps its arms around it, opens the shell and eats it...

Scallop(Pecten), a genus of marine invertebrates of the class of bivalve mollusks (Bivalvia). The scallop shell is rounded with a straight hinge edge. Its surface is covered with radial ribs diverging from the top. The shell valves are closed by one strong muscle. Pecten maximus, Flexopecten glaber live in the Black Sea; in the Seas of Japan and Okhotsk – Mizuhopecten yessoensis ( up to 17 cm in diameter).

Rocker dragonfly larva jet pump

Temperament Rocker dragonfly larvae, or eshny(Aeshna sp.) is no less predatory than its winged relatives. She lives for two and sometimes four years in the underwater kingdom, crawling along the rocky bottom, tracking down small aquatic inhabitants, happily including fairly large-sized tadpoles and fry in her diet. In moments of danger, the larva of the rocker dragonfly takes off and swims forward with jerks, driven by the work of the remarkable jet pump. Taking water into the hindgut and then abruptly throwing it out, the larva jumps forward, driven by the recoil force. Thus using jet propulsion principle, the larva of the rocker dragonfly with confident jerks and jerks hides from the threat pursuing it.

Reactive impulses of the nervous “freeway” of squids

In all the above cases (principles of jet propulsion of jellyfish, scallops, rocker dragonfly larvae), shocks and jerks are separated from each other by significant periods of time, therefore high speed of movement is not achieved. To increase the speed of movement, in other words, number of reactive impulses per unit time, necessary increased nerve conduction which stimulate muscle contraction, servicing a living jet engine. Such large conductivity is possible with a large nerve diameter.

It is known that Squids have the largest nerve fibers in the animal world. On average, they reach a diameter of 1 mm - 50 times larger than that of most mammals - and they conduct excitation at a speed 25 m/s. And a three-meter squid dosidicus(it lives off the coast of Chile) the thickness of the nerves is fantastically large - 18 mm. Nerves are thick like ropes! Brain signals – the triggers of contractions – rush along the squid’s nervous “freeway” at the speed of a car – 90 km/h.

Thanks to squids, research into the vital functions of nerves advanced rapidly at the beginning of the 20th century. "And who knows, writes British naturalist Frank Lane, Maybe there are now people who owe it to the squid for the fact that their nervous system is in a normal state..."

The speed and maneuverability of the squid is also explained by its excellent hydrodynamic forms animal body, why squid and nicknamed “living torpedo”.

Squid(Teuthoidea), suborder of cephalopods of the order Decapods. The size is usually 0.25-0.5 m, but some species are largest invertebrate animals(squids of the genus Architeuthis reach 18 m, including the length of the tentacles).
The body of squids is elongated, pointed at the back, torpedo-shaped, which determines their high speed of movement as in water ( up to 70 km/h), and in the air (squids can jump out of the water to a height up to 7 m).

Squid Jet Engine

Jet propulsion, now used in torpedoes, aircraft, missiles and space shells, is also characteristic of cephalopods - octopuses, cuttlefish, squids. Of greatest interest to technicians and biophysicists is squid jet engine. Notice how simply, with what minimal use of material, nature solved this complex and still unsurpassed task;-)

In essence, the squid has two fundamentally different engines ( rice. 1a). When moving slowly, it uses a large diamond-shaped fin, which periodically bends in the form of a running wave along the body of the body. The squid uses a jet engine to launch itself quickly.. The basis of this engine is the mantle - muscle tissue. It surrounds the mollusk’s body on all sides, making up almost half the volume of its body, and forms a kind of reservoir - mantle cavity - the “combustion chamber” of a living rocket, into which water is periodically sucked in. The mantle cavity contains the gills and internal organs of the squid ( rice. 1b).

With a jet swimming method the animal sucks water through a wide open mantle gap into the mantle cavity from the boundary layer. The mantle gap is tightly “fastened” with special “cufflinks-buttons” after the “combustion chamber” of a living engine is filled with sea water. The mantle gap is located near the middle of the squid's body, where it is thickest. The force causing the movement of the animal is created by throwing a stream of water through a narrow funnel, which is located on the abdominal surface of the squid. This funnel, or siphon, is "nozzle" of a living jet engine.

The engine “nozzle” is equipped with a special valve and the muscles can turn it. By changing the angle of installation of the funnel-nozzle ( rice. 1c), the squid swims equally well, both forward and backward (if it swims backward, the funnel is extended along the body, and the valve is pressed against its wall and does not interfere with the water stream flowing from the mantle cavity; when the squid needs to move forward, the free end of the funnel elongates somewhat and bends in the vertical plane, its outlet collapses and the valve takes a curved position). Jet shocks and the absorption of water into the mantle cavity follow one after another with elusive speed, and the squid rushes like a rocket in the blue of the ocean.

Squid and its jet engine - Figure 1

1a) squid – a living torpedo; 1b) squid jet engine; 1c) the position of the nozzle and its valve when the squid moves back and forth.

The animal spends a fraction of a second taking water in and pushing it out. By sucking water into the mantle cavity in the aft part of the body during periods of slow movements due to inertia, the squid thereby carries out suction of the boundary layer, thus preventing the flow from stalling during an unsteady flow regime. By increasing the portions of ejected water and increasing the contraction of the mantle, the squid easily increases its speed of movement.

The squid jet engine is very economical, thanks to which he can reach speed 70 km/h; some researchers believe that even 150 km/h!

Engineers have already created engine similar to a squid jet engine: This water cannon, operating using a conventional gasoline or diesel engine. Why squid jet engine still attracts the attention of engineers and is the object of careful research by biophysicists? To work underwater, it is convenient to have a device that operates without access to atmospheric air. The creative search of engineers is aimed at creating a design hydrojet engine, similar air-jet…

Based on materials from wonderful books:
“Biophysics in physics lessons” Cecilia Bunimovna Katz,
And "Primates of the Sea" Igor Ivanovich Akimushkina

Kondakov Nikolay Nikolaevich (1908–1999) – Soviet biologist, animal artist, Candidate of Biological Sciences. His main contribution to biological science was his drawings of various representatives of the fauna. These illustrations were included in many publications, such as Great Soviet Encyclopedia, Red Book of the USSR, in animal atlases and teaching aids.

Akimushkin Igor Ivanovich (01.05.1929–01.01.1993) – Soviet biologist, writer and popularizer of biology, author of popular science books about animal life. Laureate of the All-Union Society "Knowledge" award. Member of the USSR Writers' Union. The most famous publication of Igor Akimushkin is a six-volume book "Animal world".

The materials in this article will be useful to apply not only in physics lessons And biology, but also in extracurricular activities.
Biophysical material is extremely beneficial for mobilizing the attention of students, for turning abstract formulations into something concrete and close, affecting not only the intellectual, but also the emotional sphere.

Literature:
§ Katz Ts.B. Biophysics in physics lessons

§ § Akimushkin I.I. Primates of the sea
Moscow: Mysl Publishing House, 1974
§ Tarasov L.V. Physics in nature
Moscow: Prosveshchenie Publishing House, 1988

Jellyfish swim easily by contracting their bell. Each contraction releases water from under the bell, causing the jellyfish's body to move in the opposite direction. It turns out to be a kind of jet engine; the jellyfish floats forward with powerful thrusts.

V. G. Bogorov. Life of the sea. M., Ed. "Young Guard", 1954.

More precisely a barometer

When the wind blows strongly over the sea, it tears off not only spray and foam from the crests, but also... infrasounds. They quickly run in all directions and warn all the inhabitants of the sea who hear them about the approaching storm. And the jellyfish hears it: sound infrawaves with a frequency of 8 - 13 hertz hit tiny pebbles that float in the “ear” of the jellyfish - a tiny ball on a thin stalk. The pebbles rub against the nerve receptors in the walls of the “ball”, and the jellyfish hears

the menacing roar of an approaching storm. A “jellyfish ear” device has already been designed - its similarity with the original is not only in the name: it quite accurately imitates the infrasound-sensitive organ of a jellyfish. The device works with great accuracy: it warns about the approach of a storm 15 hours in advance.

I. Akimushkin. Where? And How? M., "Thought", 1965.

Who is the enemy, who is the friend

The largest known jellyfish, Cyanea. can reach 4 m in diameter and have tentacles up to 30 m long. This orange-blue monster is one of the largest invertebrate animals, posing a real danger to swimmers in the North Atlantic Ocean.

The young of many fish find protection from enemies in the tentacles of this giant jellyfish. The jellyfish does not touch it, but kills those predators who, in the excitement of chasing the fry, swim too close to the jellyfish’s tentacles.

K. Willie. Biology. M., Ed. "World", 1964.

Sea lanterns

Among the coelenterates, compared to other types of multicellular organisms, the percentage of luminous species is highest. Jellyfish equiorea (5-10 cm in diameter) is sometimes so abundant in the harbors of the Pacific coast of the United States that its light makes the waves seem to be on fire at night, and fireballs stick to the blades of the oars. This jellyfish is also found off the Atlantic coast of the United States, where it is joined by another luminous jellyfish, the cyanea. The most famous is the glow of the yellow-orange pelagic jellyfish, which is found in the open sea near the surface of tropical and moderately cold waters in all oceans and in the Mediterranean Sea. The outer surface of her umbrella and tentacles glow. Glow occurs only with external irritations; such an irritant could simply be a splash of water. A light touch to the jellyfish causes a glow in this place, which spreads further as irritation intensifies. Flashes of glow in this jellyfish last for several minutes. The luminous Charybdea jellyfish, with its tall, cuboid-shaped umbrella, is widespread in warm coastal waters.

N. I. Tarasov. Living light of the sea. M., 1956.

Commonwealth in the struggle and betrayal of it when dividing the spoils

The development of sessile jellyfish haliclistus occurs in a very unique way. The larvae formed from eggs crawl for 2 - 4 days, after which they become motionless and settle in groups of up to 20 pieces. At the same time, they are able to paralyze relatively large animals, using all their stinging capsules. One of the larvae, which captures most of the prey, grows quickly, the rest are doomed to starvation, from which they die. The growing larva gives rise to offspring; Before it transforms into an adult haliclistus, new larvae grow on its body in the form of buds, completely similar to the larvae originating from the eggs, and which begin the same life cycle.

According to the book: A. E. Brem. Animal life, vol. I. M., Uchpedgiz, 1948.

What gender is she?

The compass jellyfish is one of the few hermaphroditic jellyfish. In youth, for the most part, it possesses only male gonads; later, both eggs and livestock are formed in it, and, finally, in old animals exclusively eggs are formed. The eggs develop in the mother's body and are separated from her in the form of larvae covered with cilia.

According to the book: A. E. Brem. Animal life, vol. I, M., Uchpedgiz, 1948.

They eat fish, but there is no mouth

Cornerome jellyfish are deprived of a real mouth opening - instead there is a series of strongly folded depressions, like funnels, at the bottom of which there are tiny pores, leading through a series of tubules into the general gastrovascular cavity. The edges of the funnels are capable of stretching greatly and capturing fairly large prey, even fish. The prey is digested in these external funnels, and only dissolved food products enter the gastrovascular cavity.

S. A. Zernov. General hydrobiology. M., Ed. USSR Academy of Sciences, 1949

Jellyfish have muscles. True, they are very different from human muscles. How are they structured and how does a jellyfish use them for movement?

Jellyfish are fairly simple creatures compared to humans. Their body lacks blood vessels, heart, lungs and most other organs. Jellyfish have a mouth, often located on a stalk and surrounded by tentacles (visible below in the picture). The mouth leads into a branched intestine. And most of the jellyfish’s body is an umbrella. Tentacles also often grow on its edges.

The umbrella may shrink. When the jellyfish contracts the umbrella, water is released from under it. A recoil occurs, pushing the jellyfish in the opposite direction. Often such movement is called reactive (although this is not entirely accurate, but the principle of movement is similar).

The umbrella of a jellyfish consists of a gelatinous elastic substance. It contains a lot of water, but also strong fibers made from special proteins. The upper and lower surfaces of the umbrella are covered with cells. They form the integument of the jellyfish - its “skin”. But they are different from our skin cells. Firstly, they are located in only one layer (we have several dozen layers of cells in the outer layer of skin). Secondly, they are all alive (we have dead cells on the surface of our skin). Third, the integumentary cells of jellyfish usually have muscular processes; That's why they are called dermal-muscular. These processes are especially well developed in cells on the lower surface of the umbrella. Muscle processes stretch along the edges of the umbrella and form the circular muscles of the jellyfish (some jellyfish also have radial muscles, located like spokes in an umbrella). When the circular muscles contract, the umbrella contracts and water is thrown out from under it.

It is often written that jellyfish do not have real muscles. But it turned out that this was not the case. In many jellyfish, under the layer of skin-muscle cells on the lower side of the umbrella, there is a second layer - real muscle cells (see figure).

Arrangement of muscles in the umbrella of some hydroid jellyfish. Skin-muscle cells with smooth muscle fibers are shown in green, striated muscle cells are shown in red.

Humans have two main types of muscles - smooth and striated. Smooth muscles consist of ordinary cells with a single nucleus. They ensure contraction of the walls of the intestines and stomach, bladder, blood vessels and other organs. Striated (skeletal) muscles in humans consist of huge multinucleated cells. They are responsible for the movement of our arms and legs (as well as our tongue and vocal cords when we speak). Striated muscles have a characteristic striation and contract faster than smooth muscles. It turned out that in most jellyfish, movement is also ensured by striated muscles. Only their cells are small and mononuclear.

In humans, striated muscles are attached to the bones of the skeleton and transmit forces to them during contraction. And in jellyfish, the muscles are attached to the gelatinous substance of the umbrella. If a person bends his arm, then when the biceps relaxes, it extends due to the action of gravity or due to the contraction of another muscle - the extensor. Jellyfish do not have “umbrella extensor muscles.” After the muscles relax, the umbrella returns to its original position due to its elasticity.

But in order to swim, it is not enough to have muscles. We also need nerve cells that give the muscles the order to contract. It is often believed that the nervous system of jellyfish is a simple nervous network of individual cells. But this is also wrong. Jellyfish have complex sensory organs (eyes and balance organs) and clusters of nerve cells - nerve ganglia. You could even say that they have a brain. Only it is not like the brain of most animals, which is located in the head. Jellyfish have no head, and their brain is a nerve ring with nerve ganglia on the edge of an umbrella. Nerve cell processes extend from this ring, giving commands to the muscles. Among the cells of the nerve ring there are amazing cells - pacemakers. An electrical signal (nerve impulse) appears in them at certain intervals without any external influence. Then this signal spreads around the ring, is transmitted to the muscles, and the jellyfish contracts the umbrella. If these cells are removed or destroyed, the umbrella will stop contracting. Humans have similar cells in their heart.

In some respects, the nervous system of jellyfish is unique. The well-studied jellyfish has aglanta ( Aglantha digitale) there are two types of swimming - normal and “flight reaction”. When swimming slowly, the muscles of the umbrella contract weakly, and with each contraction the jellyfish moves one body length (about 1 cm). During the “flight reaction” (for example, if you pinch a jellyfish’s tentacle), the muscles contract strongly and frequently, and for each contraction of the umbrella, the jellyfish moves forward 4–5 body lengths, and can cover almost half a meter in a second. It turned out that the signal to the muscles is transmitted in both cases along the same large nerve processes (giant axons), but at different speeds! The ability of the same axons to transmit signals at different speeds has not yet been discovered in any other animal.

What is the name of the method of movement of a jellyfish? Class Scyphoid. Reactive impulses of the nervous “freeway” of squids

Among aquatic invertebrate animals - inhabitants of the seas, a group of organisms called scyphoids stands out. They have two biological forms - polypoid and medusoid, differing in their anatomy and way of life. This article will study the structure of the jellyfish, and also discuss the features of its life activity.

General characteristics of the scyphoid class

These organisms belong to the type of coelenterates and are exclusively marine inhabitants. Scyphoid jellyfish, photos of which are presented below, have a bell-shaped or umbrella-shaped body, and the body itself is transparent and gelatinous, consisting of mesoglea. All animals of this class are second-order consumers and feed on zooplankton.

Organisms are characterized by a radial body: anatomically identical parts, as well as tissues and organs, are located radially from the median longitudinal axis. It is characteristic of animals that passively swim in the water column, as well as those species that lead a sedentary lifestyle (anemones) or slowly crawl along the substrate (urchins).

External building. Habitat

Since representatives of scyphoids have two life forms - jellyfish and polyps, let us consider their anatomy, which has some differences. First, let's study the external structure of a jellyfish. Turning the animal over with the base of the bell down, we find a mouth bordered with tentacles. It performs dual functions: it absorbs parts of food and removes its undigested remains outside. Such organisms are called protostomes. The body of the animal is two-layered, consisting of ectoderm and endoderm. The latter forms the intestinal (gastric) cavity. Hence the name:

The gap between the layers of the body is filled with a transparent jelly-like mass - mesoglea. Ectodermal cells perform supporting, motor and protective functions. The animal has a skin-muscular sac that allows it to move in water. The anatomical structure of the jellyfish is quite complex, since the ecto- and endoderm are differentiated into various In addition to the integumentary and muscular, the outer layer also contains intermediate cells that perform a regenerative function (from which damaged parts of the animal’s body can be restored).

The structure of neurocytes in scyphoids is interesting. They have a star-shaped shape and with their processes intertwine the ectoderm and endoderm, forming clusters - nodes. A nervous system of this type is called diffuse.

Endoderm and its functions

The inner layer of scyphoids forms a gastrovascular system: digestive canals, lined with glandular (secreting digestive juice) and phagocytic cells, extend from the intestinal cavity in rays. These structures are the main cells that break down food particles. The structures of the skin-muscle sac are also involved in digestion. Their membranes form pseudopodia, capturing and drawing in organic particles. Phagocytic cells and pseudopodia carry out two types of digestion: intracellular (as in protists) and cavity, inherent in highly organized multicellular animals.

Stinging cells

Let's continue to study the structure of the scyphoid jellyfish and consider the mechanism by which animals defend themselves and also attack potential prey. Scyphoids also have another systematic name: the class Cnidarians. It turns out that in the ectodermal layer they have special cells - nettle, or stinging cells, also called cnidocytes. They are found around the mouth and on the tentacles of the animal. When exposed to mechanical stimuli, the thread located in the nettle cell capsule is rapidly thrown out and pierces the body of the victim. Scyphoid toxins that penetrate the cnidocoel are lethal to planktonic invertebrates and fish larvae. In humans, they cause symptoms of urticaria and skin hyperthermia.

Sense organs

Along the edges of the bell of the jellyfish, the photo of which is presented below, you can see shortened tentacles called marginal bodies - rhopalia. They contain two sense organs: vision (eyes that react to light) and balance (statocysts that look like calcareous pebbles). With their help, scyphoids learn about an approaching storm: sound waves in the range from 8 to 13 Hz irritate the statocysts, and the animal hastily moves deeper into the sea.

and reproduction

Continuing to study the structure of a jellyfish (the figure is presented below), we will focus on the reproductive system of scyphoids. It is represented by gonads formed from the pouches of the gastric cavity, which are of ectodermal origin. Since these animals are dioecious, eggs and sperm are released through the mouth and fertilization occurs in water. The zygote begins to fragment and a single-layer embryo is formed - the blastula, and from it - a larva called the planula.

It floats freely, then attaches to the substrate and turns into a polyp (scyphistoma). It can bud and is also capable of strobilation. A stack of young jellyfish called ethers forms. They are attached to the central trunk. The structure of a jellyfish detached from the strobile is as follows: it has a system of radial canals, a mouth, tentacles, rhopalia and the rudiments of the gonads.

Thus, the structure of the jellyfish differs from the asexual scyphistoma, which has a cone-shaped shape 1-3 mm in size and is attached to the surface with a stalk. The mouth is surrounded by a corolla of tentacles, and the gastric cavity is divided into 4 pouches.

How do scyphoids move?

Jellyfish is capable of She sharply pushes out a portion of water and moves forward. The animal's umbrella contracts up to 100-140 times per minute. While studying the structure of a scyphoid jellyfish, for example, a cornerot or aurelia, we noted such an anatomical formation as a skin-muscular sac. It is located in the ectoderm; efferent fibers of the marginal nerve ring and ganglia approach its cells. The excitation is transmitted to the skin-muscular structures, as a result of which the umbrella contracts, then, expanding, pushes the animal forward.

Features of the ecology of scyphoids

These representatives of the coelenterate class are common both in warm seas and in cold Arctic waters. Aurelia is a scyphoid jellyfish, the body structure of which we studied, lives in the Black and Azov Seas. Another representative of this class, Cornerot (rhizostoma), is also widespread there. It has a milky white umbrella with purple or blue edges, and mouth lobes that resemble roots. Tourists vacationing in Crimea know this species well and try to stay away from its representatives while swimming, since the animal’s stinging cells can cause serious “burns” on the body. Ropilema, like Aurelia, lives in the Sea of Japan. The color of its rhopalia is pink or yellow, and they themselves have numerous finger-like outgrowths. The umbrella mesoglea of both species is used in Chinese and Japanese cuisine under the name "crystal meat".

Cyanea is an inhabitant of cold Arctic waters. The length of its tentacles reaches 30-35 m, and the diameter of the umbrella is 2-3.5 m. Lion's mane or hairy cyanea has two subspecies: Japanese and blue. The poison of the stinging cells located along the edges of the umbrella and on the tentacles is very dangerous for humans.

We studied the structure of scyphoid jellyfish, and also became familiar with the features of their life activity.

In the section on the question How does a jellyfish move? given by the author Dazed The best answer is: Jellyfish move slowly. scyphoid jellyfish move according to a reactive principle, pushing out water by contracting the dome

Answer from Alice frame[newbie]
ahahaha it floats in my opinion that’s logical :)

Answer from glacial period[guru]
With the help of fur pillows ;-))

Answer from Petitioner[guru]
Jet propulsion. Octopuses are also faster.

Answer from Flush[guru]
moving beautifully...

Answer from Veta[guru]
The most progressive method of movement of aquatic invertebrates is hydrojet. It is believed that the simplest jet engine is possessed by single-celled animals - gregarines. They slowly glide through the water without visible movements. For a long time we wondered how they moved. It turned out that, releasing droplets of a gelatinous substance from the smallest holes on the body, they repel the water and thus move forward.
Jellyfish use a jet mode of movement. Hydroid jellyfish have a muscular membrane attached to the lower edge of the umbrella. By alternately expanding and contracting, the jellyfish draws water under the dome and then pushes it out. When water is pushed out, it receives a push and moves with its convex side forward. The shocks follow one after another every 5-6 seconds, and therefore the jellyfish swims slowly. Scallop mollusks have a similarity to hydrojet engines; they swim, or rather, jump in the water, slamming the shell flaps and spraying water from under them.

The logic of nature is the most accessible and most useful logic for children.

Konstantin Dmitrievich Ushinsky(03.03.1823–03.01.1871) - Russian teacher, founder of scientific pedagogy in Russia.

BIOPHYSICS: JET MOTION IN LIVING NATURE

A number of animals move in nature using the principle of jet propulsion, for example, jellyfish, scallops, dragonfly larvae, squid, octopus, cuttlefish... Let's get to know some of them better ;-)

The jet method of movement of jellyfish

Jet escape of scallops

Rocker dragonfly larva jet pump

Reactive impulses of the nervous “freeway” of squids

The speed and maneuverability of the squid is also explained by its excellent hydrodynamic forms animal body, why squid and nicknamed “living torpedo”.

Squid Jet Engine

Squid and its jet engine - Figure 1

1a) squid – a living torpedo; 1b) squid jet engine; 1c) the position of the nozzle and its valve when the squid moves back and forth.

The squid jet engine is very economical, thanks to which he can reach speed 70 km/h; some researchers believe that even 150 km/h!

Based on materials from wonderful books:
“Biophysics in physics lessons” Cecilia Bunimovna Katz,
And "Primates of the Sea" Igor Ivanovich Akimushkina

Literature:
§ Katz Ts.B. Biophysics in physics lessons

§ § Akimushkin I.I. Primates of the sea
Moscow: Mysl Publishing House, 1974
§ Tarasov L.V. Physics in nature
Moscow: Prosveshchenie Publishing House, 1988

Cornermouth jellyfish(Latin name Rhizostoma pulmo) is a group of variegated jellyfish that lives mainly in warm seas. This group includes many large jellyfish that inhabit the shores of the Atlantic Ocean, the North, Mediterranean, Black and Baltic seas.

Cornerot jellyfish are distinguished by the fact that they do not have a single central “mouth”. Its role is played by 8 long root-like “arms”, which are interconnected by numerous holes in a canal system. Externally, the “hands” resemble the roots and stems of sea plants. Hence its unusual name - cornerot. There are no tentacles at all. Cornerota jellyfish are excellent swimmers. Unlike their relatives, they can move in any direction.

Among the jellyfish of the cornerota group, the most famous are the following: rhizostoma Aldrovandi, Cassiopeia, rhizostoma Tsiviri. Rhizostoma Aldrovandi is found in the Mediterranean Sea and is a “bell” up to 80 centimeters wide.

Cassiopeia inhabits the coast of Florida and the Red Sea. Her way Its movement is very curious: it does not swim freely like other jellyfish, but lies on the bottom, on coral sand, with its lower side turned up and making weak movements with the edges of the bell.

Common jellyfish found in the waters of the Black Sea are represented by the species Rhizostoma pulmo. They have a milky or darkish white, less often bluish or violet-colored “body”, with dark blue umbrella edges and reddish, yellowish or violet “arms”. The diameter of the umbrella of the Rhizostoma pulmo jellyfish varies from 20 to 80 centimeters, and the height can reach 30 centimeters. Some jellyfish can hardly fit in a bucket.

Jellyfish eat microscopic plankton and fish fry. The latter are attacked by jellyfish with poisonous stinging cells located along the edges of the oral cavities. When meeting a person, a jellyfish can use stinging cells to defend itself.

It cannot kill a person with them, but it can inflict a painful burn. The diameter of the burn is sometimes 25-50 centimeters. Such a burn may take several years to disappear from the skin. Often, the affected person later develops a persistent allergy to seafood.

Some types of cornet jellyfish are eaten. Among them, a special place is occupied by edible rospilema (Latin name Rhopilema esculenta), which is part of the national dishes of Japan and China. The “meat” of jellyfish in these countries is called “crystal”. “Crystal meat” is not consumed in its pure form, but is usually added to various salads and generously flavored with pepper, cinnamon and nutmeg.