Significance of the bright coloration of male fish. What determines the color of fish? Coloring of fish, its biological significance

The color of fish can be surprisingly diverse, but all possible shades of their color are due to the work of special cells called chromatophores. They are found in a specific layer of the fish's skin and contain several types of pigments. Chromatophores are divided into several types. Firstly, these are melanophores containing a black pigment called melanin. Further, etitrophores, containing red pigment, and xanthophores, in which it is yellow. The latter type is sometimes called lipophores because the carotenoids that make up the pigment in these cells are dissolved in lipids. Guanophores or iridocytes contain guanine, which gives the color of fish a silvery color and metallic luster. The pigments contained in chromatophores differ chemically in terms of stability, solubility in water, sensitivity to air, and some other features. The chromatophores themselves are also not the same in shape - they can be either stellate or rounded. Many colors in the coloration of fish are obtained by imposing some chromatophores on others, this possibility is provided by the occurrence of cells in the skin on different depth. For example, a green color is obtained when deep-lying guanophores are combined with xanthophores and erythrophores covering them. If you add melanophores, the body of the fish becomes blue.

Chromatophores do not have nerve endings, with the exception of melanophores. They are even involved in two systems at once, having both sympathetic and parasympathetic innervation. Other types of pigment cells are controlled humorally.

The color of fish is quite important for their life. Coloring functions are divided into patronizing and warning. The first option is designed to mask the body of the fish in the environment, so usually this coloration consists of soothing colors. Warning coloration, on the other hand, includes a large number of bright spots and contrasting colors. Its functions are different. In poisonous predators, which usually say with the brightness of their body: “Don’t come near me!”, It plays a deterrent role. Territorial fish guarding their home are brightly colored in order to warn the rival that the place is occupied and to attract the female. A kind of warning coloration is also the marriage attire of fish.

Depending on the habitat, the body color of the fish acquires characteristic features that make it possible to distinguish pelagic, bottom, thicket and schooling colors.

Thus, the color of fish depends on many factors, including habitat, lifestyle and nutrition, season, and even the mood of the fish.

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The coloration of fish, including the color pattern, is an important signal. The main function of color is to help members of the same species find and identify each other as potential sexual partners, rivals, or members of the same pack. Demonstration of a certain coloration may not go further than this.

Fish of certain species take on one color or another, demonstrating their readiness for spawning. The bright colors of the fins make a proper impression on potential sexual partners. Occasionally, a mature female will develop a brightly colored area on her belly, emphasizing its rounded shape and indicating that it is filled with caviar. Fish that have a specific bright spawning coloration may appear dull and inconspicuous when not spawning. A noticeable appearance makes the fish more vulnerable to predators, and predatory fish unmasks.

Spawning coloration may also serve as a stimulus for competition, for example in competition for a spawning partner or for spawning territory. The preservation of such coloration after the end of spawning would be completely meaningless, and perhaps even clearly unfavorable for schooling fish.

Some fish have an even more highly developed "language" of coloration, and they can use it, for example, to demonstrate their status in a group of fish of the same species: the brighter and more challenging the coloring and pattern, the higher the status. They may also use coloration to demonstrate threat (bright coloration) or submission (dim or less bright coloration), often accompanied by gestures, body language, and fish.

Some fish showing parental care for offspring have a special coloration when guarding young. This coloration of the watchman is used to warn uninvited guests or draw attention to yourself, distracting from the fry. Scientific experiments have shown that parents use certain types coloring to attract fry (to make it easier for them to find their parents). Even more remarkable is that some fish use body and fin movements and coloration to give various instructions to their fry, for example: "Swim here!", "Follow me" or "Hide at the bottom!"

It must be assumed that each species of fish has its own "language", corresponding to their special way of life. However, there is strong evidence that closely related fish species clearly understand each other's basic signals, although they most likely do not have the slightest idea what the representatives of another fish family are "talking" among themselves. By the way, the zooportal jokingly disassembled the fish by color:

The aquarist cannot "answer" the fish in their language, but in sioah he can recognize some of the signals given by the fish. This will allow predicting the actions of underwater inhabitants, for example, to notice the approaching spawning, or the growing conflict.

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Thus, snail worms were recently discovered, whose ancestors lived on Earth over 500 million years ago; scientists also managed to catch a fish that was previously thought to have died out 70 million years ago.

This material is dedicated to the extraordinary, mysterious and yet unexplained phenomena ocean life. Learn to understand the complex and varied relationships between the inhabitants of the ocean, many of which have lived in its depths for millions of years.

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« What determines the color of fish?

Presentation "What determines the color of fish"

The inhabitants of the sea are among the most brightly colored creatures in the world. Such organisms, shimmering with all the colors of the rainbow, live in the sun-drenched waters of warm tropical seas.

Coloration of fish, its biological significance.

Coloration is of great biological importance for fish. There are protective and warning colors. The protective coloration is intended to camouflage the fish against the background of the environment. Warning, or sematic, coloration usually consists of conspicuous large, contrasting spots or bands that have clear boundaries. It is intended, for example, for poisonous and poisonous fish, to prevent a predator from attacking them and in this case is called a deterrent.

Identification coloration used to warn a rival in territorial fish, or to attract females to males by warning them that the males are ready to spawn. The last type of warning coloration is commonly referred to as the mating dress of fish. Often the identification coloration unmasks the fish. It is for this reason that in many fish guarding the territory or their offspring, the identification coloration in the form of a bright red spot is located on the belly, shown to the opponent if necessary, and does not interfere with the disguise of the fish when it is located belly to the bottom. There is also a pseudosematic coloration that mimics the warning coloration of another species. It is also called mimicry. It allows harmless fish species to avoid being attacked by predators who mistake them for dangerous view.

What determines the color of fish?

The color of fish can be surprisingly diverse, but all possible shades of their color are due to the work of special cells called chromatophores. They are found in a specific layer of the fish's skin and contain several types of pigments. Chromatophores are divided into several types.

First, these are melanophores containing a black pigment called melanin. Further, etitrophores, containing red pigment, and xanthophores, in which it is yellow. The latter type is sometimes called lipophores because the carotenoids that make up the pigment in these cells are dissolved in lipids. Guanophores or iridocytes contain guanine, which gives the color of fish a silvery color and metallic luster. The pigments contained in chromatophores differ chemically in terms of stability, solubility in water, sensitivity to air, and some other features. The chromatophores themselves are also not the same in shape - they can be either stellate or rounded. Many colors in the coloration of fish are obtained by superimposing one chromatophore on another, this possibility is provided by the occurrence of cells in the skin at different depths. For example, a green color is obtained when deep-lying guanophores are combined with xanthophores and erythrophores covering them. If you add melanophores, the body of the fish becomes blue.

Chromatophores do not have nerve endings, with the exception of melanophores. They are even involved in two systems at once, having both sympathetic and parasympathetic innervation. Other types of pigment cells are controlled humorally.

The color of fish is quite important for their life.. Coloring functions are divided into patronizing and warning. The first option is designed to mask the body of the fish in the environment, so usually this coloration consists of soothing colors. Warning coloring, on the contrary, includes a large number of bright spots and contrasting colors. Its functions are different. In poisonous predators, which usually say with the brightness of their body: “Don’t come near me!”, It plays a deterrent role. Territorial fish guarding their home are brightly colored to warn the rival that the place is occupied and to attract the female. A kind of warning coloration is also the marriage attire of fish.

Depending on the habitat, the body color of the fish acquires characteristic features that make it possible to distinguish pelagic, bottom, thicket and schooling colors.

Thus, the color of fish depends on many factors, including habitat, lifestyle and nutrition, season, and even the mood of the fish.

Identification coloration

In the life-infested waters around the coral reefs, each species of fish has its own identification paint, similar to the uniforms of football players of one team. This allows other fish and individuals of the same species to instantly recognize it.

The coloring of the dogfish becomes brighter when it seeks to attract a female.

Dogfish - deadly dangerous predator

Dog fish belongs to the order of pufferfish or pufferfish, and there are more than ninety species of them. It differs from other fish in its unique ability to inflate when frightened, swallowing a large volume of water or air. At the same time, she pricks with spikes, spewing out a nerve poison called tetrodotoxin, which is 1200 times more effective. potassium cyanide

The dog-fish, due to the special structure of the teeth, was called the pufferfish. Puffer teeth are very strong, fused together, and look like four plates. With their help, she splits the shells of mollusks and crab shells, getting food. A rare case is known when live fish, not wanting to be eaten, bit off the cook's finger. Some species of fish are also able to bite, but the main danger is its meat. In Japan, this exotic fish is called fugu, skillfully cooked, it is at the top of the list of local delicacies. The price for one serving of such a dish reaches $ 750. When an amateur chef takes over its preparation, the tasting ends lethal outcome, because in the skin and in internal organs This fish contains the strongest poison. First, the tip of the tongue goes numb, then the limbs, followed by convulsions and instant death. When gutting the fish, the dog emits a fetid, eerie odor.

The coloring of the Moorish idol fish is most striking when it hunts its prey.

The main body color is white. The edge of the upper jaw is black. The lower jaw is almost completely black. In the upper part of the muzzle there is a bright orange spot with a black border. There is a wide black stripe between the first dorsal fin and the ventral fin. Two thin, curved bluish stripes run from the first black stripe, from the beginning of the pelvic fins to the front. dorsal fin, and from the abdominal cavity to the base of the dorsal fin. The third, less noticeable, bluish stripe is located from the eyes towards the back. The second, gradually expanding, wide black stripe is located from the dorsal rays in the direction of the ventral ones. Behind the second wide black stripe is a thin vertical white line. A bright yellow-orange spot with a thin white border extends from the tail to the middle of the body, where it gradually merges with the main white color. The caudal fin is black with white trim.

Day and night coloring

At night, the fusilier fish sleeps on seabed, taking on a dark coloration that matches the color sea ​​depths and bottom. Waking up, it brightens and becomes completely light as it approaches the surface. By changing color, it becomes less noticeable.

awake fish

Waking up fish

sleeping fish

Warning coloration

Seeing from afar brightly colored harlequin toothfish”, other fish immediately understand that this hunting area is already occupied.

Warning coloration

The bright coloring warns the predator: beware, this creature tastes bad or is poisonous! Pointy-nosed puffer fish extremely poisonous, and other fish do not touch it. In Japan, this fish is considered edible, but when cutting it, an experienced connoisseur must be present to remove the poison and make the meat harmless. And yet this fish, called fugu and considered a delicacy, claims the lives of many people every year. So, in 1963, viper fish were poisoned by meat and 82 people died.

The puffer fish is not at all scary in appearance: it is only the size of a palm, swims with its tail forward, very slowly. Instead of scales - thin elastic skin, capable of inflating in case of danger to a size three times larger than the original - a kind of goggle-eyed, outwardly harmless ball.

However, her liver, skin, intestines, caviar, milk, and even her eyes contain tetrodoxin, a strong nerve poison, 1 mg of which is a lethal dose for humans. There is no effective antidote for it yet, although the poison itself, in microscopic doses, is used to prevent age-related diseases, as well as to treat diseases. prostate.

Multicolor Mystery

Most starfish move very slowly and live on clean bottoms, not hiding from enemies. Faded, muted tones would help them to become invisible, and it is very strange that the stars have such a bright color.

Depending on the habitat, the body color of the fish acquires characteristic features that make it possible to distinguish pelagic, bottom, thicket and schooling coloration.

Pelagic fish

The term "pelagic fish" comes from the place in which they live. This area is the area of ​​the sea or ocean, which does not border the bottom surface. Pelageal - what is it? From the Greek "pelagial" is interpreted as "open sea", which serves as a habitat for nekton, plankton and pleuston. Conventionally, the pelagic zone is divided into several layers: epipelagic - located at a depth of up to 200 meters; mesopelagial - at a depth of up to 1000 meters; bathypelagial - up to 4000 meters; over 4000 meters - abyspelagial.

Popular types

The main commercial catch of fish is pelagic. It accounts for 65-75% of the total catch. Due to the large natural supply and availability, pelagic fish are the most inexpensive type of seafood. However, this has no effect on palatability and utility. The leading position of the commercial catch is occupied by pelagic fish of the Black Sea, the North Sea, the Sea of ​​Marmara, the Baltic Sea, as well as the seas of the North Atlantic and the Pacific basin. These include smelt (capelin), anchovy, herring, herring, horse mackerel, cod (blue whiting), mackerel.

bottom fish- most life cycle carried out at the bottom or in close proximity to the bottom. They are found both in coastal regions of the continental shelf and in the open ocean along the continental slope.

Bottom fish can be divided into two main types: purely bottom and benthopelagic, which rise above the bottom and swim in the water column. In addition to the flattened shape of the body, an adaptive feature of the structure of many bottom-dwelling fish is the lower mouth, which allows them to feed from the ground. Sand sucked in with food is usually ejected through gill slits.

overgrown coloring

Overgrown painting- brownish, greenish or yellowish back and usually transverse stripes or stains on the sides. This coloration is characteristic of fish in thickets or coral reefs. Sometimes these fish, especially in tropical zone, can be colored very brightly.

Examples of fish with overgrown coloration are: common perch and pike - from freshwater forms; sea ​​scorpion ruff, many wrasses and coral fish- from the sea.

Vegetation, as an element of the landscape, is also important for adult fish. Many fish are specially adapted to life in thickets. They have the appropriate patronizing coloration. or a special form of the body, reminiscent of ts zardeli, among which the fish lives. So, the long outgrowths of the fins of seahorse- rag-picker, - in combination with the appropriate color, they make it completely invisible among the underwater thickets.

flock coloring

A number of features in the structure are also associated with a schooling lifestyle, in particular the color of fish. Schooling coloration helps fish to orient themselves to each other. In those fish in which a schooling lifestyle is characteristic only of juveniles, accordingly, schooling coloration can also appear.

A moving flock is different in shape from a stationary one, which is associated with the provision of favorable hydrodynamic conditions for movement and orientation. The shape of a moving and stationary school differs in different species of fish, and np may be different in the same species. A moving fish forms a certain force field around its body. Therefore, when moving in a flock, fish adjust to each other in a certain way. Flocks are grouped from fish usually of close sizes and a similar biological state. Fish in a flock, unlike many mammals and birds, apparently do not have a permanent leader, and they alternately focus either on one or the other of their member, or, more often, on several fish at once. Fish navigate in a flock with the help, first of all, of the organs of vision and the lateral line.

Mimicry

One of the adaptations is color change. Flat fish are masters of this miracle: they can change color and its pattern in accordance with the pattern and color of the seabed.

Presentation Hosting

The morphological side of the coloration of fish has been described earlier. Here we will analyze environmental significance coloring in general and its adaptive value.
Few animals, not excluding insects and birds, can compete with fish in the brightness and variability of their coloration, which disappears for them for the most part with death and after being placed in a preservative liquid. Only bony fishes (Teleostei) are so diversely colored, which have all the methods of color formation in various combinations. Stripes, spots, ribbons are combined on the main background, sometimes in a very complex pattern.
In the coloration of fish, as well as other animals, many see in all cases an adaptive phenomenon, which is the result of selection and gives the animal the opportunity to become invisible, hide from the enemy, and lie in wait for prey. In many cases this is certainly true, but not always. Recently, there are more and more objections to such a one-sided interpretation of the color of fish. A number of facts speak for the fact that coloration is a physiological result, on the one hand, of metabolism, on the other, of the action of light rays. Coloration arises from this interaction and may have no protective value at all. But in those cases where coloration can be ecologically important, when coloration is supplemented by the corresponding habits of fish, when it has enemies from which it is necessary to hide (and this is not always the case in those animals that we consider to be protectively colored), then coloration becomes a tool in the struggle for existence, is subject to selection and becomes an adaptive phenomenon. Coloring can be useful or harmful not in itself, but being correlated with some other useful or harmful feature.
AT tropical waters and metabolism and light are more intense. And the coloring of animals is brighter here. In the colder and less brightly illuminated waters of the north, and even more so in caves or underwater depths, the color is much less bright, sometimes even scooping.
The need for light in the production of pigment in the skin of fish is supported by experiments with flounders kept in aquariums in which the underside of the flounder was exposed to light. On the latter, a pigment gradually developed, but usually the underside of the body of the flounder is white. Experiments were made with young flounders. Pigmentation developed the same as on the upper side; if the flounders were kept in this way for a long time (1-3 years), then the underside became exactly the same pigmented as the top. This experiment, however, does not contradict the role of selection in the development of protective coloration - it only shows the material from which, due to selection, the flounder has developed the ability to respond to the action of light by forming a pigment. Since this ability could be expressed to the same extent in different individuals, selection could act here. As a result, in flounders (Pleuronoctidae) we see a pronounced changeable protective coloration. In many flounders upper surface the body is painted in various shades of brown with black and light spots and is in harmony with the prevailing tone of the sandbars on which they usually feed. Once on the ground of a different color, they immediately change their color to the color corresponding to the color of the bottom. Experiments with the transfer of flounders to soils painted like a chessboard with squares of various sizes gave a striking picture of the animal acquiring the same pattern. It is very important that some fish that change in different times habitat, adapt in their color to new conditions. For example, Pleuronectes platessa in the summer months rests on clean light sand and is light in color. In the spring, after spawning, R. platessa, having changed color, is looking for silty soil. The same choice of habitat corresponding to coloration, more precisely, the appearance of a different coloration in connection with a new habitat, is also observed in other fish.
Fish living in transparent rivers and lakes, as well as fish in the surface layers of the sea, have common type coloration: the back, they are colored dark, mostly blue, and the ventral side is silvery. It is generally accepted that the dark blue color of the spoke makes the fish invisible to aerial enemies; the lower one - silvery - against predators, who usually stay at a greater depth and can notice the fish from below. Some believe that the silvery-shiny coloration of the belly of fish from below is invisible. According to one opinion, rays reaching the surface of the water from below at an angle of 48° (in salt water 45°) are entirely reflected from the dog. The position of the eyes on the fish's head is such that they can see the surface of the water at a maximum angle of 45°. Thus, only reflected rays enter the eyes of the fish, and the surface of the water appears to the fish as silver-shiny, like the bottom and sides their prey, which for this reason becomes invisible. According to another opinion, the mirror surface of the water reflects the bluish, greenish and brown tops of the entire reservoir, the silvery belly of the fish does the same. The result is the same as in the first case.
However, other researchers believe that the above interpretation of the white or silver color of the belly is incorrect; that its useful value for fish is not proved by anything; that the fish is not attacked from below and that it must appear dark and conspicuous from below. The white color of the ventral side, in this opinion, is a simple consequence of the absence of its illumination. However specific feature a trait can become only if it is directly or indirectly useful biologically. Therefore, simplified physical explanations are hardly justified.
In fish living at the bottom of the reservoir, the upper surface of the body is dark, often decorated with sinuous stripes, larger or smaller spots. The ventral side is gray or whitish. Such bottom fish include palima (Lota lota), minnow (Gobio fluviatilis), goby (Cottus gobio), catfish (Siluris glanis), loach (Misgurnus fossilis) - from freshwater, sturgeon (Acipenseridae), and from purely marine - marine devil (Lophius piscatorius), stingrays (Batoidei) and many others, especially flounders (Pleuronectidae). In the latter, we see a sharply pronounced changeable protective coloration, which was mentioned above.
We see another type of color variability when fish of the same species become darker in deep water with a muddy or peaty bottom (lake) and lighter in shallow and clear water. An example is the trout (Salmo trutta morpha fario). Trout from gravel or sandy bottom streams are lighter in color than those from muddy streams. Vision is necessary for this color change. We are convinced of this by experiments with transection of the optic nerves.
A striking example of protective coloration is australian view seahorse - Phyllopteryx eques, in which the skin forms numerous, long, flat, branched threads, colored with brown and orange stripes, like algae, among which the fish lives. Many fish living among the coral reefs of the Indian and Pacific Oceans, especially fish belonging to the Ohaсtodontidae and Pomacentridae families, have in the highest degree brilliant and lively coloration, often decorated with stripes of various colors. In both named families, the same color pattern developed independently. Even the reef-visiting flounders, which are usually dull in color, have the upper surface adorned with lively tops and striking patterning.
Coloring can be not only protective, but also help the predator to be invisible to its prey. Such, for example, is the striped coloration of our perch and pike, and perhaps zander; dark vertical stripes on the body of these fish make them invisible among plants, where they wait for prey. In connection with this coloration, many predators develop special processes on the body that serve to lure prey. Such, for example, is the sea devil (Lophius piscatorius), painted patronizingly and having the anterior ray of the dorsal fin changed into a antennae, mobile thanks to special muscles. The movement of this antenna deceives the small fishes, mistaking it for a worm and approaching to disappear into the mouth of Lophius.
It is quite possible that some cases of bright coloration serve as warning coloration in fish. Such, probably, is the brilliant coloration of many symtognathic (Plectognathi). It is associated with the presence of prickly spines that can bulge, and can serve as an indication of the danger of attacking such fish. The meaning of warning coloration, perhaps, has a bright color sea ​​dragon(Trachinus draco), armed with poisonous spikes on the gill cover and a large spine on the back. Perhaps, some cases should be attributed to the phenomena of an adaptive nature. complete disappearance coloration in fish. Many pelagic larvae of Teleostei lack chromatophores and are colorless. Their body is transparent, and therefore hardly noticeable, just as glass lowered into the water is hardly noticed. Transparency increases due to the absence of hemoglobin in the blood, as, for example, in Leptocephali - eel larvae. Larvae of Onos (family Gadidae) during the pelagic period of their life have a silver color due to the presence of iridocytes in the skin. Ho, passing with age to life under stones, they lose their silver luster and acquire a dark color.

Pisces are extremely various colors with a very strange design. A special variety of colors is observed in tropical fish and warm waters. It is known that fish of the same species in different bodies of water have different colors, although they mostly retain the pattern characteristic of this species. Take at least a pike: its color changes from dark green to bright yellow. The perch usually has bright red fins, a greenish color from the sides and a dark back, but there are whitish perches (in rivers) and, conversely, dark ones (in ilmens). All such observations suggest that the color of fish depends on their systematic position from the habitat, environmental factors, nutritional conditions.

The coloration of fish is due to special cells found in skin-containing pigment grains. Such cells are called chromatophores.

Distinguish: melanophores (contain black pigment grains), erythrophores (red), xanthophores (yellow) and guanophores, iridocytes (silver color).

Although the latter are considered chromatophores and do not have pigment grains, they contain a crystalline substance - guanine, due to which the fish acquires a metallic sheen and silvery color. Of the chromatophores, only melanophores have nerve endings. The shape of the chromatophores is very diverse, however, the most common are stellate and discoid.

In terms of chemical resistance, the black pigment (melanin) is the most resistant. It is not soluble in acids, alkalis, and does not change as a result of changes in the physiological state of the fish (starvation, nutrition). Red and yellow pigments are associated with fats, so the cells containing them are called lipophores. The pigments of erythrophores and xanthophores are very unstable, dissolve in alcohols and depend on the quality of nutrition.

Chemically, pigments are complex substances belonging to different classes:

1) carotenoids (red, yellow, orange)

2) melanins - indoles (black, brown, gray)

3) flavins and purine groups.

Melanophores and lipophores are located in different layers of the skin on the outer and inner sides of the boundary layer (cutis). Guanophores (or leukophores, or iridocytes) differ from chromatophores in that they do not have pigment. Their color is due to the crystal structure of guanine, a protein derivative. Guanophores are located under the chorium. It is very important that guanine is located in the plasma of the cell, like pigment grains, and its concentration can change due to intracellular plasma currents (thickening, thinning). Guanine crystals are hexagonal in shape and, depending on their location in the cell, the color changes from silvery-whitish to bluish-violet.

Guanophores in many cases are found together with melanophores and erythrophores. They play very big biological role in the life of fish, because located on the abdominal surface and on the sides, they make the fish less noticeable from below and from the sides; the protective role of coloring is especially pronounced here.

The function of pigment staves is mainly to expand, i.e. occupying more space (expansion) and reducing i.e. occupying the smallest space (contract). When the plasma contracts, decreasing in volume, the pigment grains in the plasma are concentrated. Thanks to this most of the surface of the cell is released from this pigment and as a result, the brightness of the color decreases. During expansion, the cell plasma spreads over a larger surface, and pigment grains are distributed along with it. Due to this, a large surface of the body of the fish is covered with this pigment, giving the fish a color characteristic of the pigment.

The reason for the expansion of the concentration of pigment cells can be both internal factors (the physiological state of the cell, organism), and some factors. external environment(temperature, content of oxygen and carbon dioxide inlet). Melanophores have innervation. Canthophores and erythrophores lack innervation: Therefore, the nervous system can only have a direct effect on melanophores.

It has been established that the pigment cells of bony fish retain a constant shape. Koltsov believes that the plasma of a pigment cell has two layers: ectoplasm (surface layer) and kinoplasm (inner layer) containing pigment grains. The ectoplasm is fixed by radial fibrils, while the kinoplasm is highly mobile. Ectoplasm determines the external form of the chromatophore (the form of ordered movement), regulates metabolism, and changes its function under the influence of the nervous system. Ectoplasm and kinoplasm, having different physical and chemical properties, mutual wettability when their properties change under the influence of the external environment. During expansion (expansion), the kinoplasm wets the ectoplasm well and, due to this, spreads through the cracks covered with ectoplasm. The pigment grains are located in the kinoplasm, are well moistened with it, and follow the flow of the kinoplasm. At concentration, the reverse picture is observed. There is a separation of two colloidal layers of protoplasm. The kinoplasm does not wet the ectoplasm and due to this the kinoplasm
occupies the smallest volume. This process is based on a change in surface tension at the boundary of two layers of protoplasm. Ectoplasm by its nature is a protein solution, and kinoplasm is a lecithin-type lipoid. Kinoplasm is emulsified (very finely divided) in ectoplasm.

In addition to nervous regulation, chromatophores also have hormonal regulation. It must be assumed that under different conditions one or another regulation is carried out. A striking adaptation of body color to the color of the environment is observed in sea ​​needles, gobies, flounders. Flounders, for example, can copy the pattern of the ground and even a chessboard with great accuracy. This phenomenon is explained by the fact that the nervous system plays a leading role in this adaptation. The fish perceives color through the organ of vision and then, by transforming this perception, the nervous system controls the function of the pigment cells.

In other cases, hormonal regulation clearly appears (coloration during the breeding season). In the blood of fish there are hormones of the adrenal gland adrenaline and the posterior pituitary gland - pituitrin. Adrenaline causes concentration, pituitrin is an antagonist of adrenaline and causes expansion (diffusion).

Thus, the function of pigment cells is under the control of the nervous system and hormonal factors, i.e. internal factors. But besides them, environmental factors (temperature, carbon dioxide, oxygen, etc.) matter. The time required to change the color of the fish is different and ranges from a few seconds to several days. As a rule, young fish change their color faster than adults.

It is known that fish change body color according to the color of the environment. Such copying is carried out only if the fish can see the color and pattern of the ground. This is evidenced by the following example. If the flounder lies on a black board, but does not see it, then it does not have the color of a black board, but of the white soil visible to it. On the contrary, if the flounder lies on the ground white color, but sees a black board, then her body takes on the color of a black board. These experiments convincingly show that fish easily adapt, changing their color to unusual ground for them.

Lighting affects the color of the fish. "Like in dark places where there is low light, the fish lose their color. bright fish that have lived for some time in the dark, become pale in color. Blinded fish acquire dark color. On dark, the fish becomes dark in color, on light light. Frisch managed to establish that the darkening and lightening of the body of the fish depends not only on the illumination of the ground, but also on the angle of view from which the fish can see the ground. So, if the eyes of a trout are tied or removed, then the fish becomes black. If you cover only the lower half of the eye, the fish acquires a dark color, and if you glue only the upper half of the eye, then the fish retains its color.

Light has the strongest and most varied influence on the color of fish. Light
affects melanophores both through the eyes and nervous system, as well as directly. So Frisch, illuminating certain areas of the skin of the fish, received a local change in color: a darkening of the illuminated area (expansion of melanophores) was observed, which disappeared 1-2 minutes after the light was turned off. In connection with prolonged illumination in fish, the color of the back and abdomen changes. Usually the back of fish living on not great depths and in clear waters has a dark tone, and the abdomen is light. In fish living at great depths and muddy waters no such color difference is observed. It is believed that the difference in the coloration of the back and abdomen has an adaptive value: the dark back of the fish is less visible from above against a dark background, and the light abdomen from below. In this case, the different coloration of the abdomen and back is due to the uneven arrangement of pigments. There are melanophores on the back and sides, and on the sides there are only iridocytes (tuanophores), which give the abdomen a metallic sheen.

With local heating of the skin, the expansion of melanophores occurs, leading to darkening, while cooling - to lightening. A decrease in the concentration of oxygen and an increase in the concentration of carbonic acid also change the color of the fish. You probably observed that in fish after death, the part of the body that was in the water has a lighter color (melanophore concentration), and the part that protrudes from the water and comes into contact with the air is dark (melanophore expansion). The fish are in a normal state, usually the color is bright, multi-colored. With a sharp decrease in oxygen or in a state of suffocation, it becomes paler, dark tones almost completely disappear. The fading of the color of the integument of the fish network is the result of the concentration of chromatophores and , primarily melanophores. As a result of a lack of oxygen, the surface of the skin of the fish is not supplied with oxygen as a result of circulatory arrest or a poor supply of oxygen to the body (the beginning of suffocation), it always acquires pale tones. An increase in carbon dioxide in the water affects the color of fish in the same way as a lack of oxygen. Consequently, these factors (carbon dioxide and oxygen) act directly on the chromatophores, therefore, the center of irritation is located in the cell itself - in the plasma.

The action of hormones on the color of fish is revealed, first of all, during mating season(breeding period). Especially interesting coloring skin and fins observed in males. The function of chromatophores is under the control of hormonal agents and the feather system. Example with fighting fish. In this case, mature males, under the influence of hormones, acquire the corresponding coloration, the brightness and brilliance of which is enhanced by the sight of a female. The eyes of the male see the female, this perception is transmitted through the nervous system to the chromatophores and causes them to expand. The male skin chromatophores function in this case under the control of hormones and the nervous system.

Experimental work on the minnow showed that the injection of adrenaline causes a lightening of the integument of the fish (melanophore contraction). A microscopic examination of the skin of an adrenalized minnow showed that melanophores are in a state of contraction, and lipophores are in expansion.

Questions for self-examination:

1. The structure and functional significance of fish skin.

2. The mechanism of mucus formation, its composition and significance.

3. Structure and functions of scales.

4. Physiological role of skin and scale regeneration.

5. The role of pigmentation and coloration in the life of fish.

Section 2: Materials of laboratory works.