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It would seem that the answer to this question is obvious: to swim, or rather, to stay at the required depth. The fish bubble is like a natural hydrostatic sensor.

Down or up

When the fish goes deep, the water pressure on its body immediately increases, the swim bladder begins to contract and pushes air out of itself. This happens "automatically", that is, the fish do not control the process on their own. The amount of air inside the body decreases and the fish almost does not have to make any efforts to dive to depth.

When the fish goes up, everything happens exactly the opposite. The pressure of water on the body decreases and the bubble gradually fills with gas, if the fish stops, the bubble will be able to hold it at the desired depth without effort.

The nerve endings that penetrate the swimming organ transmit impulses to the central nervous system, and the fish feels: at what depth it is and what pressure it is experiencing, in connection with which it can adjust its movement.

Where does the gas come from and what kind?

Depending on the type of swim bladder, adult fish are divided into two groups: closed-vesicular and open-vesicular. In the first, the bubble is filled with gases from the blood and gives them also to the vessels, through a special network of capillaries on a thin wall. In open-bubble fish, the bladder is a separate organ and fills after the fish swallows atmospheric air.

As for the gas that fills the bubble, it is mainly oxygen, hydrocarbon and some nitrogen.

Another bubble function

Many ichthyologists will disagree with the statement that fish are "models" of silence, because they can and give special signals to their own kind, converting sound waves from water vibrations, and they do this with the help of a swim bladder.

Which fish don't have a bubble?

Not all fish have acquired this useful organ, sailfish, many deep-sea and bottom fish do not have a bubble, and why do they need it if they never try to float to the surface.

The swimbladder can perform hydrostatic, respiratory and sound-forming functions. It is absent in fishes leading a bottom lifestyle and in deep-sea fishes. In the latter, buoyancy is provided mainly due to fat due to its incompressibility or due to the lower density of the fish body, such as in ancistrus, golomyanka and drop fish. In the course of evolution, the swim bladder was transformed into the lungs of terrestrial vertebrates.

Description

During the embryonic development of fish, the swim bladder appears as a dorsal outgrowth of the intestinal tube and is located under the spine. In the process of further development, the canal connecting the swim bladder with the esophagus may disappear. Depending on the presence or absence of such a channel, fish are divided into open and closed bubbles. In open-bubble fish ( physostomy) the swim bladder is connected to the intestines throughout life by an air duct through which gases enter and are removed. Such fish can swallow air and thus control the volume of the swim bladder. Carp, herring, sturgeon and others belong to the open-bubble. In adult closed-bubbly fish ( physicalists) the air duct is overgrown, and gases are released and absorbed through the red body - a dense plexus of blood capillaries on the inner wall of the swim bladder.

Hydrostatic function

The main function of the swim bladder in fish is hydrostatic. It helps the fish stay at a certain depth, where the weight of the water displaced by the fish is equal to the weight of the fish itself. When the fish actively sinks below this level, its body, experiencing greater external pressure from the water side, contracts, squeezing the swim bladder. In this case, the weight of the displaced volume of water decreases and becomes less than the weight of the fish and the fish falls down. The lower it falls, the stronger the water pressure becomes, the more the fish's body is compressed and the more rapidly its fall continues. On the contrary, when surfacing closer to the surface, the gas in the swim bladder expands and reduces the specific gravity of the fish, which pushes the fish even more towards the surface.

Thus, the main purpose of the swim bladder is to provide zero buoyancy in the normal habitat of fish, where it does not need to spend energy to maintain the body at this depth. For example, sharks that do not have a swim bladder are forced to maintain their depth of submersion with constant active movement.

Links

• Swim bladder- article from the Great Soviet Encyclopedia
• - Useful information about the swim bladder.

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See what "Swim bladder" is in other dictionaries:

SWIMMING BUBBLE, an air-filled bag that keeps bony fish afloat. It is located under the intestines. Due to the presence of a channel connecting the bladder with the intestines, it can deflate and inflate, filling ... Scientific and technical encyclopedic dictionary

An unpaired or paired fish organ that performs hydrostatic, respiratory and sound-forming functions ... Big Encyclopedic Dictionary

- (vesica pаtatoria), hot or paired organ of fish; develops as an outgrowth of the anterior part of the intestine. Performs hydrostatic, some fish breathe. and sound-producing functions, as well as the role of a resonator and a transducer of sound waves. In some fish P. p. ... ... Biological encyclopedic dictionary

An unpaired or paired fish organ that performs hydrostatic, respiratory and sound-forming functions. * * * SWIMMING BUBBLE SWIMMING BUBBLE, unpaired or paired fish organ performing hydrostatic, respiratory and ... ... encyclopedic Dictionary

An unpaired or paired fish organ that develops as an outgrowth of the anterior part of the intestine; can perform hydrostatic, respiratory and sound-forming functions, as well as the role of a resonator and transducer of sound waves. In lungs, ... ... Great Soviet Encyclopedia

An unpaired or paired organ of fish that performs hydrostatic respiration. and sound generating. functions ... Natural science. encyclopedic Dictionary

BUBBLE, bubble, husband. 1. A transparent, hollow and filled with air (or some kind of gas) ball that appears in some liquid mass or is formed from it and is separated due to the pressure of the air stream. Blow bubbles. Bubbles in ... ... Explanatory dictionary Ushakova

The appendage of the intestinal canal of fish, quite often from it, is completely disconnected and filled with gases. Usually the P. bubble is placed on the dorsal side of the animal and plays an important role in swimming, confining it to a certain depth (see ... ... Encyclopedic Dictionary of F.A. Brockhaus and I.A. Efron

Noun., M., Uptr. cf. often Morphology: (no) who? bubble to whom? bubble, (see) whom? bubble by whom? bubble, about whom? about the bubble; pl. who? bubbles, (no) who? bubbles to whom? bubbles, (see) whom? bubbles by whom? bubbles, about whom? about bubbles 1. Bubble ... ... Dmitriev's Explanatory Dictionary

Books

• Amazing fish. Audio encyclopedia (CDmp3), Kachur Elena. You will get acquainted with the amazing inhabitants of our planet - fish. The guys will learn what the lateral line and the swim bladder are. They will understand how fish breathe, how they hear and how ...

The buoyancy of fish (the ratio of the density of the fish's body to the density of the water) can be neutral (0), positive or negative. In most species, buoyancy ranges from +0.03 to –0.03. With positive buoyancy, fish float, with neutral buoyancy, they hover in the water column, with negative buoyancy, they submerge.

Rice. 10. Swimming bladder of carp.

Neutral buoyancy (or hydrostatic balance) in fish is achieved:

1) with the help of a swim bladder;

2) watering the muscles and lightening the skeleton (in deep-sea fish)

3) the accumulation of fat (sharks, tuna, mackerel, flounder, gobies, loaches, etc.).

Most fish have a swim bladder. Its occurrence is associated with the appearance of a bone skeleton, which increases the proportion of bony fish. In cartilaginous fishes, the swim bladder is absent, from bony fishes it is absent in benthic (gobies, flounder, pinagor), deep-sea and some fast-swimming species (tuna, bonito, mackerel). An additional hydrostatic adaptation in these fish is the lifting force, which is formed due to muscular efforts.

The swim bladder is formed as a result of protrusion of the dorsal wall of the esophagus, its main function is hydrostatic. The swimbladder also perceives pressure changes, is directly related to the organ of hearing, being a resonator and reflector of sound vibrations. In loaches, the swim bladder is covered with a bone capsule, has lost its hydrostatic function, and acquired the ability to perceive changes in atmospheric pressure. In lungs and bony ganoids, the swim bladder performs the function of respiration. Some fish are capable of making sounds with the help of their swim bladder (cod, hake).

The swimbladder is a relatively large elastic sac that sits under the kidneys. It happens:

1) unpaired (most fish);

2) paired (lung-breathing and mnogoper).

In many fish, the swim bladder is single-chambered (salmonids), in some species it is two-chambered (cyprinids) or three-chambered (error), the chambers communicate with each other. In a number of fish, the bladder has blind processes connecting it to the inner ear (herring, cod, etc.).

The swim bladder is filled with a mixture of oxygen, nitrogen, and carbon dioxide. The ratio of gases in the swim bladder in fish differs and depends on the type of fish, the depth of habitation, physiological state, etc. Deep-sea fish contain much more oxygen in the swim bladder than in species living closer to the surface. Fish with a swim bladder are divided into open-vesicular and closed-vesicular fish. In open-bladder fish, the swim bladder is connected to the esophagus by means of an air duct. These include - lungs, mnogoper, cartilaginous and bony ganoids, from bony - herring, carp, pike. In Atlantic herring, sprat and anchovy, in addition to the usual air duct, there is a second duct behind the anus, which connects back part swim bladder with the external environment. Closed-bubbly fish have no air duct (perch-like, cod-like, mullet-like, etc.). The initial filling of the swim bladder with gases in fish occurs when the larva swallows atmospheric air. Thus, in carp larvae, this takes place 1–1.5 days after hatching. If this does not happen, the development of the larva is disrupted and it dies. In closed-bubbly fish, the swim bladder eventually loses its connection with the external environment; in open-bubbly fish, the air duct remains throughout life. The regulation of the volume of gases in the swim bladder in closed vesicular fish occurs using two systems:

1) gaseous iron (fills the bladder with gases from the blood);

2) oval (absorbs gases from the bladder into the blood).

The gaseous gland is a system of arterial and venous vessels located in front of the swim bladder. An oval area in the inner lining of the swim bladder with thin walls, surrounded by a muscular sphincter, is located at the back of the bladder. When the sphincter relaxes, gases from the swim bladder flow to the middle layer of its wall, where there are venous capillaries and their diffusion into the blood occurs. The amount of absorbed gases is regulated by changing the size of the oval opening.

When closed-bubble fishes submerge, the volume of gases in their swim bladder decreases, and the fish acquire negative buoyancy, but upon reaching a certain depth, they adapt to it by releasing gases into the swim bladder through the gas gland. When the fish rises, when the pressure decreases, the volume of gases in the swim bladder increases, their excess is absorbed through the oval into the blood, and then through the gills is removed into the water. In open-bubble fish, there is no oval; excess gases are removed to the outside through the air duct. Most open-bubble fish do not have a gas gland (herring, salmon). The secretion of gases from the blood into the bladder is poorly developed and is carried out with the help of the epithelium located on the inner layer of the bladder. Many open-bubble fish trap air before diving to ensure neutral buoyancy at depth. However, during strong dives, it is not enough, and the filling of the swim bladder occurs with gases coming from the blood.

The fish organism is quite complex and multifunctional. The ability to stay underwater with swimming manipulations and maintaining a stable position is due to the special structure of the body. In addition to the organs familiar even for humans, the bodies of many underwater inhabitants are provided with critical parts that allow them to provide buoyancy and stabilization. The swim bladder, which is an extension of the intestine, is essential in this context. According to many scientists, this organ can be considered as the predecessor of the human lungs. But in fish, it performs its primary tasks, which are not limited only to the function of a kind of balancer.

Swim bladder formation

The development of the bladder begins in the larva, from the anterior gut. Most freshwater fish retain this organ throughout their lives. At the time of release from the larva, there is still no gaseous composition in the bubbles of the fry. To fill it with air, the fish have to rise to the surface and independently capture the necessary mixture. During embryonic development, the swim bladder forms as a dorsal outgrowth and sits under the spine. Subsequently, the canal that connects this part with the esophagus disappears. But this does not happen in all individuals. On the basis of the presence and absence of this channel, fish are divided into closed- and open-bubble. In the first case, overgrowth of the air duct occurs, and gases are removed through the blood capillaries on the inner walls of the bladder. In open-bladded fish, this organ is connected to the intestine through the air duct, through which gases are excreted.

Bubble gas filling

Gas glands stabilize the pressure of the bladder. In particular, they contribute to its increase, and if it is necessary to lower it, the red body, formed by a dense capillary network, is involved. Since the equalization of pressure in open-bubble fish occurs more slowly than in closed-bubble species, they can quickly rise from the water depths. When catching individuals of the second type, fishermen sometimes observe how the swim bladder protrudes from the mouth. This is due to the fact that the container swells in conditions of rapid ascent to the surface from depth. These fish, in particular, include pike perch, perch and stickleback. Some predators that live at the very bottom have a highly reduced bladder.

Hydrostatic function

The fish bladder is a multifunctional organ, but its main task is to stabilize the position in different conditions under the water. This is a function of a hydrostatic nature, which, by the way, can be replaced by other parts of the body, which is confirmed by examples of fish that do not have such a bubble. One way or another, the main function is to help the fish stay at certain depths, where the weight of the water displaced by the body corresponds to the weight of the individual itself. In practice, the hydrostatic function can manifest itself as follows: at the moment of active immersion, the body compresses together with the bubble, and on the ascent, on the contrary, straightens out. In the process of immersion, the mass of the displaced volume decreases and becomes less than the weight of the fish. Therefore, the fish can go down without much difficulty. The lower the immersion, the higher the pressure force becomes and the more the body is compressed. The reverse processes occur at the moments of ascent - the gas expands, as a result of which the mass is lightened and the fish easily rises up.

Function of the sense organs

Along with the hydrostatic function, this organ also acts as a kind of hearing aid. With its help, fish can perceive noise and vibration waves. But not all species have such an ability - carp and catfish are included in the category with this ability. But sound perception is not provided by the swim bladder itself, but by the whole group of organs into which it enters. Special muscles, for example, can cause the walls of the bladder to vibrate, which causes the sensation of vibrations. It is noteworthy that in some species that have such a bubble, hydrostatics are completely absent, but the ability to perceive sounds is preserved. This applies mainly to those who spend most of their lives at the same level under water.

Protective functions

At moments of danger, minnows, for example, can release gas from the bubble and produce specific sounds that are distinguishable by their relatives. At the same time, one should not think that sound production is of a primitive nature and cannot be perceived by other inhabitants of the underwater world. Humpbacks are well known to fishermen for their rumbling and grunting sounds. Moreover, the swim bladder, which fish has a trigger, literally terrified the crews of American submarines during the war - the sounds were so expressive. Usually, such manifestations take place at moments of nervous overstrain of fish. If, in the case of the hydrostatic function, the work of the bubble occurs under the influence of external pressure, then sound formation arises as a special protective signal generated exclusively by the fish.

What fish don't have a swim bladder?

Sailfish are deprived of this organ, as well as species that lead a benthic life. Almost all deep-sea individuals also do without a swim bladder. This is exactly the case when buoyancy can be provided in alternative ways - in particular, thanks to the accumulation of fat and their ability not to shrink. Low body density in some fish also contributes to maintaining stability. But there is also another principle of maintaining the hydrostatic function. For example, a shark does not have a swim bladder, so it is forced to maintain a sufficient diving depth through active manipulation of the body and fins.

Conclusion

It is not for nothing that many scientists draw parallels between and the fish bubble. These parts of the body are united by an evolutionary relationship, in the context of which it is worth considering the modern structure of fish. The fact that not all fish species have a swim bladder makes it inconsistent. This does not mean at all that this organ is unnecessary, but the processes of its atrophy and reduction indicate the possibility of doing without this part. In some cases, fish use the internal fat and density of the lower body for the same hydrostatic function, while in others they use their fins.