Adaptations of fish to the environment. The adaptability of fish to life in water in the external and internal structure, reproduction. How does a person use knowledge about the life of fish for their artificial breeding? List the adaptations of fish to the aquatic environment.
The most important property of all organisms on earth is their amazing ability to adapt to environmental conditions. Without it, they could not exist in constantly changing living conditions, the change of which is sometimes quite abrupt. Fishes are extremely interesting in this respect, because the adaptability to the environment of some species over an infinitely long period of time led to the appearance of the first terrestrial vertebrates. Many examples of their adaptability can be observed in the aquarium.
Many millions of years ago, in the Devonian seas of the Paleozoic era, there lived amazing, long extinct (with a few exceptions) lobe-finned fish (Crossopterygii), to which amphibians, reptiles, birds and mammals owe their origin. The swamps in which these fish lived began to gradually dry up. Therefore, over time, to the gill breathing they had until now, pulmonary breathing was also added. And the fish more and more adapted to breathing oxygen from the air. Quite often it happened that they were forced to crawl from dried-up reservoirs to places where there was still at least a little water left. As a result, over many millions of years, five-fingered limbs developed from their dense, fleshy fins.
In the end, some of them adapted to life on land, although they still did not go very far from the water in which their larvae developed. This is how the first ancient amphibians arose. Their origin from lobe-finned fishes is proved by the finds of fossil remains, which convincingly show the evolutionary path of fishes to terrestrial vertebrates and thus to humans.
This is the most convincing material evidence of the adaptability of organisms to changing environmental conditions, which can only be imagined. Of course, this transformation lasted for millions of years. In the aquarium, we can observe many other kinds of adaptability, less important than those just described, but faster and therefore more obvious.
Fish are quantitatively the richest class of vertebrates. To date, over 8,000 species of fish have been described, many of which are known in aquariums. In our reservoirs, in rivers, lakes, there are about sixty species of fish, for the most part economically valuable. About 300 species of freshwater fish live on the territory of Russia. Many of them are suitable for aquariums and can serve as its decoration either all their lives, or at least while the fish are young. With our ordinary fish, we can most easily observe how they adapt to environmental changes.
If we place a young carp about 10 cm long in a 50 x 40 cm aquarium and a carp of the same size in a second aquarium 100 x 60 cm in size, then after a few months we find that the carp contained in the larger aquarium has outgrown the other carp from the small aquarium. . Both received the same amount of the same food and, however, did not grow in the same way. In the future, both fish will stop growing altogether.
Why is this happening?
Reason - pronounced adaptability to external environmental conditions. Although in a smaller aquarium the appearance of the fish does not change, but its growth slows down significantly. The larger the aquarium that contains the fish, the larger it will become. Increased water pressure - either to a greater or lesser extent, mechanically, through hidden irritations of the senses - causes internal, physiological changes; they are expressed in a constant slowdown in growth, which finally stops altogether. Thus, in five aquariums of different sizes, we can have carps of the same age, but completely different in size.
If a fish, which has been kept in a small vessel for a long time and which therefore has become ill, is placed in a large pool or pond, then it will begin to catch up with what has been lost in its growth. If she does not catch up with everything, however, she can significantly increase in size and weight even in a short time.
Under the influence of different environmental conditions, fish can significantly change their appearance. So fishermen know that between fish of the same species, for example, between pikes or trout caught in rivers, dams and lakes, there is usually a large enough difference. The older the fish, the more striking these external morphological differences are usually, which are caused by prolonged exposure to different environments. The fast-flowing stream of water in a river bed, or the quiet depths of a lake and a dam, equally but differently affect the shape of the body, always adapted to the environment in which this fish lives.
But human intervention can change the appearance of a fish so much that an uninitiated person sometimes hardly thinks that it is a fish of the same species. Let's take, for example, the well-known veiltails. Skillful and patient Chinese, through a long and careful selection, brought out a completely different fish from a goldfish, which differed significantly from the original shape in the shape of the body and tail. The veiltail has a fairly long, often hanging, thin and split tail fin, similar to the most delicate veil. His body is rounded. Many types of veiltails have bulging and even turned up eyes. Some forms of veiltails have strange outgrowths on their heads in the form of small combs or caps. A very interesting phenomenon is the adaptive ability to change color. In the skin of fish, as in amphibians and reptiles, pigment cells, the so-called chromophores, contain countless pigment granules. Black-brown melanophores predominate in the skin of fish from chromo- tophores. Fish scales contain silver-colored guanine, which causes this very brilliance that gives the water world such a magical beauty. Due to compression and stretching of the chromophore, a change in color of the whole animal or any part of its body can occur. These changes occur involuntarily with various excitations (fright, fight, spawning) or as a result of adaptation to a given environment. In the latter case, the perception of the situation acts reflexively on the change in color. Anyone who had the opportunity to see flounders in a marine aquarium lying on the sand with the left or right side of their flat body could observe how this amazing fish quickly changes its color as soon as it gets on a new substrate. The fish constantly "strives" to merge with the environment so that neither its enemies nor its victims notice it. Fish can adapt to water with different amounts of oxygen, to different water temperatures and, finally, to a lack of water. Excellent examples of such adaptability exist not only in the slightly modified ancient forms that have survived, such as, for example, lungfish, but also in modern fish species.
First of all, about the adaptive ability of lungfish. 3 families of these fish live in the world, which resemble giant lung salamanders: in Africa, South America and Australia. They live in small rivers and swamps, which dry up during a drought, and at normal water levels are very silty and muddy. If there is little water and it contains a sufficiently large amount of oxygen, fish breathe normally, that is, with gills, only sometimes swallowing air, because in addition to the gills themselves, they also have special lung sacs. If the amount of oxygen in the water decreases or the water dries up, they breathe only with the help of lung sacs, crawl out of the swamp, burrow into the silt and fall into hibernation, which lasts until the first relatively large rains.
Some fish, like our brook trout, need a relatively large amount of oxygen to live. Therefore, they can only live in running water, the colder the water and the faster it flows, the better. But it has been experimentally established that forms that have been grown in an aquarium from an early age do not require running water; they should only have cooler or slightly ventilated water. They adapted to a less favorable environment due to the fact that the surface of their gills increased, which made it possible to receive more oxygen.
Aquarium lovers are well aware of labyrinth fish. They are called so because of the additional organ with which they can swallow oxygen from the air. This is the most important adaptation to life in puddles, rice fields and other places with bad, decaying water. In an aquarium with crystal clear water, these fish take in less air than in an aquarium with cloudy water.
Convincing evidence of how living organisms can adapt to the environment in which they live is the viviparous fish that are very often kept in aquariums. There are many types of them, small and medium in size, variegated and less colorful. All of them have a common feature - they give birth to relatively developed fry, which no longer have a yolk sac and soon after birth live independently and hunt for small prey.
Already the act of mating these fish differs significantly from spawning, because males fertilize mature eggs directly in the body of females. The latter, after a few weeks, throw out fry, which immediately swim away.
These fish live in Central and South America, often in shallow ponds and puddles, where after the end of the rains the water level drops and the water almost or completely dries up. Under such conditions, the laid eggs would die. Fish have already adapted to this so much that they can be thrown out of drying puddles with strong jumps. Jumping, in relation to the very size of their body, is greater than that of salmon. Thus, they jump until they fall into the nearest body of water. Here the fertilized female gives birth to fry. In this case, only that part of the offspring that was born in the most favorable and deep water bodies is preserved.
Stranger fish live in the mouths of the rivers of tropical Africa. Their adaptation has stepped so far forward that they not only crawl out of the water, but can also climb onto the roots of coastal trees. These are, for example, mudskippers from the goby family (Gobiidae). Their eyes, reminiscent of a frog's, but even more protruding, are located on the top of the head, which gives them the ability to navigate well on land, where they lie in wait for prey. In case of danger, these fish rush to the water, bending and stretching the body like caterpillars. Fish adapt to living conditions mainly by their individual body shape. This, on the one hand, is a protective device, on the other hand, due to the lifestyle of various fish species. So, for example, carp and crucian carp, feeding mainly on the bottom of motionless or inactive food, while not developing a high speed of movement, have a short and thick body. Fish that burrow into the ground have a long and narrow body, predatory fish have either a strongly laterally compressed body, like a perch, or a torpedo-shaped body, like a pike, pikeperch or trout. This body shape, which does not represent strong water resistance, allows the fish to instantly attack prey. The prevailing majority of fish has a streamlined body shape that cuts through the water well.
Some fish have adapted, thanks to their way of life, to very special conditions, so much so that they even bear little resemblance to fish at all. So, for example, seahorses have a tenacious tail instead of a caudal fin, with which they strengthen themselves on algae and corals. They move forward not in the usual way, but due to the wave-like movement of the dorsal fin. Seahorses are so similar to the environment that predators hardly notice them. They have an excellent camouflage coloration, green or brown, and most of the species have on their body long, billowing outgrowths, much like algae.
In tropical and subtropical seas, there are fish that, fleeing from their pursuers, jump out of the water and, thanks to their wide, membranous pectoral fins, glide many meters above the surface. These are the flying fish. To facilitate "flight" they have an unusually large air bubble in the body cavity, which reduces the relative weight of the fish.
Tiny archers from the rivers of southwest Asia and Australia are excellently adapted to hunting flies and other flying insects that sit on plants and various objects protruding from the water. The archer keeps near the surface of the water and, noticing the prey, splashes from the mouth with a thin water jet, knocking the insect to the surface of the water.
Some fish species from various systematically distant groups have developed over time the ability to spawn far from their habitat. These include, for example, salmon fish. Before the ice age, they inhabited the fresh waters of the northern seas basin - their original habitat. After the melting of the glaciers, modern salmon species also appeared. Some of them have adapted to life in the salt water of the sea. These fish, for example, the well-known common salmon, go to rivers to spawn in fresh water, from where they later return to the sea. Salmon were caught in the same rivers where they were first seen during migration. This is an interesting analogy with the spring and autumn migrations of birds, following very specific paths. Eel behaves even more interestingly. This slippery, snake-like fish breeds in the depths of the Atlantic Ocean, probably up to 6,000 meters deep. In this cold, deep-sea desert, which is only occasionally illuminated by phosphorescent organisms, tiny, transparent, leaf-shaped eel larvae hatch from countless eggs; for three years they live in the sea before they develop into true little eels. And after that, countless juvenile eels begin their journey into the fresh water of the river, where they live for an average of ten years. By this time, they grow up and accumulate fat reserves in order to again set off on a long journey into the depths of the Atlantic, from where they never return.
The eel is excellently adapted to life at the bottom of a reservoir. The structure of the body gives him a good opportunity to penetrate into the very thickness of the silt, and with a lack of food, crawl on dry land into a nearby reservoir. Another interesting change in its color and shape of the eyes when moving to sea water. Initially dark eels turn to a silvery sheen on the way, and their eyes enlarge significantly. Enlargement of the eyes is observed when approaching the mouths of rivers, where the water is more brackish. This phenomenon can be induced in an aquarium with adult eels by diluting a little salt in the water.
Why do the eyes of eels enlarge when traveling to the ocean? This device makes it possible to catch every, even the smallest ray or reflection of light in the dark depths of the ocean.
Some fish are found in waters poor in plankton (crustaceans moving in the water column, such as daphnia, larvae of some mosquitoes, etc.), or where there are few small living organisms at the bottom. In this case, the fish adapt to feeding on insects falling to the surface of the water, most often flies. Small, about a cm long, Anableps tetrophthalmus from South America has adapted to catching flies from the surface of the water. In order to be able to move freely right at the very surface of the water, she has a straight back, strongly elongated with one fin, like a pike, very shifted back, and her eye is divided into two almost independent parts, upper and lower. The lower part is an ordinary fish eye, and the fish looks underwater with it. The upper part protrudes quite significantly forward and rises above the very surface of the water. Here, with its help, the fish, examining the surface of the water, detects fallen insects. Only some examples from the inexhaustible variety of species of adaptation of fish to the environment in which they live are given. Just like these inhabitants of the water kingdom, other living organisms are able to adapt to varying degrees in order to survive in the interspecific struggle on our planet.
T]ol of the physical properties of water in the life of fish is enormous. From the width of the water: to a large extent, the conditions of movement, the fish in. water. The optical properties of water and the content of suspended particles in it affect both the hunting conditions of fish orienting themselves with the help of their organs of vision, and the conditions for their protection from enemies.Water temperature largely determines the intensity of the metabolic process in fish. Temperature changes in many; cases, they are a natural irritant that determines the beginning of spawning, migration, etc. Other physical and chemical properties of water, such as salinity, saturation; oxygen, viscosity, are also of great importance.
DENSITY, VISCOSITY, PRESSURE AND MOTION OF WATER.
FISH MOVEMENT METHODS
Fish live in an environment much denser and more viscous than air; this is associated with a number of features in their structure, functions of their organs and behavior.
Fish are adapted to move in both stagnant and flowing water. The movements of water, both translational and oscillatory, play a very significant role in the life of fish. Fish are adapted to move in the water in different ways and at different speeds. This is connected with the shape of the body, the structure of the fins, and some other features in the structure of fish.
According to the shape of the body, fish can be divided into several types (Fig. 2):. ¦
- Torpedo-shaped - the best swimmers, inhabitants of the water column. This group includes mackerel, mullet, herring shark, salmon, etc.
- Arrow-shaped and yy - close to the previous one, but the body is more elongated and unpaired fins are pushed back. Good swimmers, inhabitants of the water column - garfish, itsuka.
- Flattened from the side - this type varies the most. It is usually subdivided into: a) bream-like, b) moon-fish type and c) flounder type. According to the habitat conditions, the fish "belonging to this type are also very diverse - from the inhabitants of the water column (moon-fish) to the bottom (bream) or bottom (flounder). :
- ; L e i t about vidi y y - body. , strongly elongated and flattened fc sides. Bad swimmers oar king - kegalecus. Trachy-pterus and others. . . , ' (
- Spherical and - the body is almost spherical, the caudal fin is usually poorly developed - boxfish, some lumpfish, etc.,
^i^shchrg^shgaa^rshgtgos^sloping motion is provided
9
Rice. 2. Different types of fish body shape:
/ - swept (garfish); 2 - torpedo-shaped (mackerel); 3 - laterally flattened, bream-like (common bream); 4 - type of fish-moon (moon-fish);
5 - type of flounder (river flounder); 6 - serpentine (eel); 7 - ribbon-like (herring king); 8 - spherical (body) 9 - flat (slope)
- Flat - the body is flattened dorsoventrally various rays, monkfish.
Shi
"shish
q (H I
IVDI
SHCHSHCH
:5
Rice. 3. Ways of movement: at the top - eel; below - cod. You can see how the wave goes through the body of the fish (from Gray, 1933)
Atnia calva L. Flounders swim, making oscillatory movements simultaneously with both dorsal and anal fins. In the skate, swimming is provided by oscillatory movements of greatly enlarged pectoral fins (Fig. 4).
Rice. 4. Movement of fish with fins: anal (electric eel) or pectoral (ray) (from Norman, 195 8)
The caudal fin mainly paralyzes the inhibitory movement of the end of the body and weakens the reverse currents. According to the nature of the action, the tails of fish are usually divided into: 1) isobathic, where the upper and lower lobes are equal in size; a similar type of tail is found in mackerel, tuna and many others; 2) e and ibatic, in which the upper lobe is better developed than the lower one; this tail facilitates upward movement; this kind of tail is characteristic of sharks and sturgeons; 3) hypobatic, when the lower lobe of the tail is more developed than the upper lobe and promotes downward movement; a hypobatic tail is found in flying fish, bream, and some others (Fig. 5).
Rice. 5. Different types of tails in fish (from left to right): epibatic, isobatic, hypobatic
The main function of the depth rudders in fish is performed by the thoracic, as well as the abdominal dyats. With the help of them, partly the rotation of the fish in a horizontal plane is also carried out. The role of unpaired fins (dorsal and anal), if they do not carry out the function of translational movement, is reduced to facilitating the turns of the fish up and down and only partly to the role of stabilizer keels (Vasnetsov, 1941).
The ability to bend the body more or less is naturally related to. its structure. Fish with a large number of vertebrae can bend the body more than fish with a small number of vertebrae. The number of vertebrae in fish ranges from 16 in the moon fish to 400 in the belt fish. Also, fish with small scales can bend their body to a greater extent than large-scaled ones.
To overcome the resistance of water, it is extremely important to minimize the friction of the body on the water. This is achieved by smoothing the surface as much as possible and lubricating it with appropriate friction reducing agents. In all fish, as a rule, the skin has a large number of goblet glands, which secrete mucus that lubricates the surface of the body. The best swimmer among fish has a torpedo-shaped body.
The speed of movement of fish is also associated with the biological state of the fish, in particular, the maturity of the gonads. They also depend on the temperature of the water. Finally, the speed of movement of the fish may vary depending on whether the fish is moving in a flock or alone. Some sharks, swordfish,
tuna. Blue shark - Carcharinus gtaucus L. - moves at a speed of about 10 m / s, tuna - Thunnus tynnus L. - at a speed of 20 m / s, salmon - Salmo salar L. - 5 m / s. The absolute speed of a fish depends on its size.’ Therefore, to compare the speed of movement of fish of different sizes, the speed coefficient is usually used, which is a quotient of the division of the absolute speed of movement
fish at the square root of its length
Very fast moving fish (sharks, tuna) have a speed factor of about 70. Fast moving fish (salmon,
Rice. 6. Scheme of the movement of flying fish during takeoff. Side and top view (from Shuleikin, 1953),
mackerel) have a coefficient of 30-60; moderately fast (herring, cod, mullet) - from 20 to 30; slow (for example, bream) - QX 10 to 20; slow. ) - less than 5.
/ Good swimmers in flowing water are somewhat different in / shape / of the body from good swimmers in still water, in particular / in the cervix, the caudal peduncle is usually / much higher, and "shorter than in the second. As an example, you can compare the shape of the caudal peduncle of a trout, adapted to live in water with a fast current, and mackerel - an inhabitant of slowly moving and stagnant sea waters.
Swimming fast., overcoming rapids and rifts, the fish get tired. They cannot swim for a long time without rest. With a lot of tension in the blood, lactic acid accumulates in the blood, which then disappears during rest. Sometimes fish, for example, when passing through fish passages, become so tired that, having passed through them, they even die (Biask, 1958; etc.). In connection with. Therefore, when designing fish passages, it is necessary to provide appropriate places for fish to rest in them.
Among the fish there are representatives who have adapted to a kind of flight through the air. This is the best
the property is developed in flying fish - Exocoetidae; actually, this is not a real flight, but a soaring like a glider. In these fish, the pectoral fins are extremely strongly developed and perform the same function as the wings of an airplane or glider (Fig. 6). The main engine that gives the initial speed during flight is the tail and, first of all, its lower blade. Having jumped out to the surface of the water, the flying fish glides over the water surface for some time, leaving behind ring waves diverging to the sides. At a time when the body of a flying fish is in the air, and only its tail remains in the water, it still continues to increase its speed, the increase of which stops only after the complete separation of the fish's body from the surface of the water. A flying fish can stay in the air for about 10 seconds and at the same time fly a distance of more than 100 miles.
Flying fish have developed flight as a protective device that allows the fish to elude predators chasing it - tuna, coryphen, swordfish, etc. Among the characin fish there are representatives (genera Gasteropelecus, Carnegiella, Thoracocharax) that have adapted to active flapping flight (Fig. 7). These are small fish up to 9-10 cm long, inhabiting the fresh waters of South America. They can jump out of the water and fly with the help of a wave of elongated pectoral fins up to 3-5 m. Although flying charadinids have smaller pectoral fins than flying fish of the Exocoetidae family, the pectoral muscles that drive the pectoral fins are much more developed. These muscles in characin fish, adapted to flapping flight, are attached to very strongly developed bones of the shoulder girdle, which form some kind of thoracic keel of birds. The weight of the muscles of the pectoral fins in flying characinids reaches up to 25% of the body weight, while in non-flying representatives of the closely related genus Tetragonopterus it is only: 0.7%,
The density and viscosity of water, as is known, depends primarily on the content of salts and temperature in water. With an increase in the amount of salts dissolved in water, its density increases. On the contrary, with an increase in temperature (above + 4 ° C), the density and viscosity decrease, and the viscosity is much stronger than the density.
Living matter is usually heavier than water. Its specific gravity is 1.02-1.06. According to A.P. Andriyashev (1944), the proportion of fish of different species varies from 1.01 to 1.09 for the fish of the Black Sea. Consequently, fish, in order to stay in the water column, “must have some special adaptations, which, as we will see below, can be quite diverse.
The main organ by which fish can regulate
to control its specific gravity, and, consequently, its confinement to certain layers of water, is the swim bladder. Only a few fish that live in the water column do not have a swim bladder. Sharks and some mackerels do not have a swim bladder. These fish regulate their position in a particular layer of water only with the help of the movement of their fins.
Rice. 7. Haracin fish Gasteropelecus adapted to flapping flight:
1 - general view; 2 - diagram of the structure of the shoulder girdle And the location of the fin:
a - cleithrum; b -, hupercoracoideum; c - hypocoracoibeum; d - pte * rhygiophora; d - rays of the fin (from Sterba, 1959 and Grasse, 1958)
In fish with a swim bladder, such as, for example, horse mackerel - Trachurus, wrasses - Crenilabrus and Ctenolabrus, southern haddock - Odontogadus merlangus euxinus (Nordm.), etc., the specific gravity is somewhat less than in fish without a swim bladder , namely; 1.012-1.021. In fish without a swim bladder [sea ruff - Scorpaena porcus L., stargazer - Uranoscopus scaber L., gobies - Neogobius melanostomus (Pall.) and N. "fluviatilis (Pall.), etc.] the specific gravity ranges from 1, 06 to 1.09.
It is interesting to note the relationship between the specific gravity of fish and its mobility. Of the fish that do not have a swim bladder, more mobile fish, such as, for example, sultanka - Mullus barbatus (L.) - (average 1.061), and the largest - bottom, burrowing, such as stargazer, have a smaller specific gravity which averages 1.085. A similar pattern is observed in fish with a swim bladder. Naturally, the proportion of fish depends not only on the presence or absence of a swim bladder, but also on the fat content of the fish, the development of bone formations (presence of a shell) IT. d.
The proportion of fish changes as it grows, as well as during the year due to changes in its fatness and fat content. So, in the Pacific herring - Clupea harengus pallasi Val. - specific gravity varies from 1.045 in November to 1.053 in February (Tester, 1940).
In most of the more ancient groups of fish (among the bony ones, in almost all herring and cyprinids, as well as lungfish, multifins, bone and cartilaginous ganoids), the swim bladder is connected to the intestines using a special duct - ductus pneumaticus. In the rest of the fish - perch-like, cod-like and other * bony ones, in the adult state, the connection of the swim bladder with the intestines is not preserved.
In some herrings and anchovies, for example, oceanic herring - Clupea harengus L., sprat - Sprattus sprattus (L.), anchovies - Engraulis encrasicholus (L.), the swim bladder has two holes. In addition to the ductus pneumaticus, there is also an external opening in the back of the bladder, which opens directly behind the anal (Svetovidov, 1950). This hole allows the fish to quickly dive or rise from the depth to the surface in a short time to remove excess gas from the swim bladder. At the same time, in a fish sinking to a depth, excess gas appears in the bubble under the influence of water pressure on its body that increases as the fish sinks. In the case of rising with a sharp decrease in external pressure, the gas in the bubble tends to occupy the largest possible volume, and in connection with this, the fish is often also forced to remove it.
A flock of herring floating to the surface can often be detected by numerous air bubbles rising from the depths. In the Adriatic Sea off the coast of Albania (Gulf of Vlora, etc.), when catching sardines in the light, Albanian fishermen accurately predict the imminent appearance of this fish from the depths by the appearance of gas bubbles released by it. The fishermen say so: “Foam has appeared, and now the sardine will appear” (message by G. D. Polyakov).
The filling of the swim bladder with gas occurs in open-bladder fish and, apparently, in most fish with a closed bladder, not immediately after leaving the egg. While the hatched free embryos go through the resting stage, hanging from the stems of plants or lying on the bottom, they do not have gas in the swim bladder. The swim bladder is filled by swallowing gas from outside. In many fish, the duct connecting the intestines to the bladder is absent in the adult state, but their larvae have it, and it is through it that their swim bladder is filled with gas. This observation is confirmed by the following experiment. Larvae were hatched from the eggs of perch fish in such a vessel, the surface of the water in which was separated from the bottom by a thin mesh impervious to larvae. Under natural conditions, the filling of the bladder with gas occurs in perch fish on the second or third day after hatching. In the experimental vessel, the fish were kept up to five to eight days of age, after which the barrier separating them from the surface of the water was removed. However, by this time the connection between the swim bladder and the intestines had been interrupted, and the bladder remained unfilled with gas. Thus, the initial filling of the swim bladder with gas in both open bladder and most fish with a closed swim bladder occurs in the same way.
In pike perch, gas in the swim bladder appears when the fish reaches about 7.5 mm in length. If by this time the swim bladder remains not filled with gas, then the larvae with an already closed bladder, even having the opportunity to swallow gas bubbles, overflow their intestines, but the gas no longer enters the bladder and exits through their anus (Kryzhanovsky, Disler and Smirnova, 1953).
From the vascular system (for unknown reasons) no gas can be released into the swim bladder until at least some gas enters it from outside.
Further regulation of the amount and composition of gas in the swim bladder in different fish is carried out in various ways. In fish that have a connection between the swim bladder and the intestine, the flow and release of gas from the swim bladder occurs to a large extent through the ductus pneumaticus. In fish with a closed swim bladder, after the initial filling with gas from the outside, further changes in the amount and composition of the gas occur through its release and absorption by the blood. Such fish have on the inner wall of the bladder. red body - extremely densely permeated with blood capillaries formation. So, in two red bodies located in the swim bladder of an eel, there are 88,000 venous and 116,000 arterial capillaries with a total length of 352 and 464 m. 3 At the same time, the volume of all capillaries in the red bodies of an eel is only 64 mm3, i.e. e. no more than a drop of medium size. The red body varies in different fish from a small spot to a powerful gas-secreting gland, consisting of a cylindrical glandular epithelium. Sometimes the red body is also found in fish with ductus pneumaticus, but in such cases it is usually less developed than in fish with a closed bladder.
According to the composition of the gas in the swim bladder, both different types of fish and different individuals of the same species differ. So, tench usually contains about 8% oxygen, perch - 19-25%, pike * - about 19%, roach - 5-6%. Since mainly oxygen and carbon dioxide can penetrate from the circulatory system into the swim bladder, it is these gases that usually predominate in the filled bladder; nitrogen is a very small percentage. On the contrary, when gas is removed from the swim bladder through the circulatory system, the percentage of nitrogen in the bladder increases dramatically. As a rule, marine fish have more oxygen in their swim bladder than freshwater fish. Apparently, this is mainly due to the predominance of forms with a closed swim bladder among marine fish. The oxygen content in the swim bladder is especially high in secondarily deep-sea fish.
І
The gas pressure in the swim bladder in fish is usually transmitted in one way or another to the auditory labyrinth (Fig. 8).
Rice. 8. Scheme of the connection of the swim bladder with the organ of hearing in fish (from Kyle and Ehrenbaum, 1926; Wunder, 1936 and Svetovidova, 1937):
1 - oceanic herring Clupea harengus L. (herring-like); 2 carp Cyprinus carpio L. (cyprinids); 3*- in Physiculus japonicus Hilgu (cod-like)
So, in herring, cod and some other fish, the anterior part of the swim bladder has paired outgrowths that reach the openings of the auditory capsules covered with a membrane (in cod), or even enter inside them (in herring). In cyprinids, the transfer of pressure from the swim bladder to the labyrinth is carried out using the so-called Weberian apparatus - a series of bones connecting the swim bladder with the labyrinth.
The swim bladder serves not only to change the specific gravity of the fish, but it also plays the role of an organ that determines the magnitude of the external pressure. In some fish, for example,
in most loaches - Cobitidae, leading a bottom lifestyle, the swim bladder is greatly reduced, and its function as an organ that perceives pressure changes is the main one. Fish can perceive even slight changes in pressure; their behavior changes when atmospheric pressure changes, for example, before a thunderstorm. In Japan, some fish are specially kept for this purpose in aquariums, and the change in their behavior is used to judge the upcoming change in the weather.
With the exception of some herrings, rögt;s, which have a swim bladder, cannot quickly move from the surface layers to the depths and back. In this regard, in most species that make rapid vertical movements (tuna, mackerel, sharks), the swim bladder is either completely absent or reduced, and retention in the water column is carried out due to muscular movements.
The swim bladder is also reduced in many bottom fish, for example, in many gobies - Gobiidae, blennies - Blenniidae, loaches - Cobitidae and some others. The reduction of the bladder in bottom fish is naturally associated with the need to provide a greater proportion of the body. In some closely related fish species, the swim bladder is often developed to varying degrees. For example, among gobies, some leading a pelagic lifestyle (Aphya), it is present; in others, such as Gobius niger Nordm., it is retained only in pelagic larvae; in gobies, whose larvae also lead a benthic lifestyle, such as Neogobius melanostomus (Pall.), the swim bladder is reduced and in larvae and adults.
In deep-sea fish, in connection with life at great depths, the swim bladder often loses contact with the intestines, since at enormous pressures the gas would be squeezed out of the bladder. This is true even of those groups, for example, Opistoproctus and Argentina of the herring order, in which, species living near the surface, have ductus pneumaticus. In other deep-sea fishes, the swim bladder may be reduced altogether, as, for example, in some Stomiatoidei.
Adaptation to life at great depths causes other very serious changes in fish that are not directly caused by water pressure. These unique adaptations are associated with the lack of natural light at depths (see p. 48), nutritional habits (see p. 279), reproduction (see p. 103), etc.
By their origin, deep-sea fish are heterogeneous; they come from different orders, often widely separated from each other. At the same time, the time of transition to deep-
. Rice. 9. Deep Sea Fish:
1 - Cryptopsarus couesii (Q111.); (foot-finned); 2-Nemichthys avocetta Jord et Gilb (acne-prone); .3 - Ckauliodus sloani Bloch et Schn, (herring-like): 4 - Jpnops murrayi Gunth. (glowing anchovies); 5 - Gasrostomus batrdl Gill Reder. (eels); 6 -x4rgyropelecus ol/ersil (Cuv.) (luminous anchovies); 7 - Pseudoliparis amblystomopsis Andr. (perciformes); 8 - Caelorhynchus carminatus (Good) (long-tailed); 9 - Ceratoscopelus maderensis (Lowe) (glowing anchovies)
the aquatic way of life in different groups of these species is very different. We can divide all deep-sea fishes into two groups: into ancient or truly deep-sea fishes and into secondary deep-sea fishes. The first group includes species belonging to such families, and sometimes suborders and orders, all of whose representatives have adapted to living in the depths. The adaptations to the deep-sea way of life in these "fishes are very significant. Due to the fact that the living conditions in the water column at depths are almost the same throughout the world's oceans, fish belonging to the group of ancient deep-sea fish are often very widespread. (Andriyashev, 1953) This group includes anglers - Ceratioidei, luminous anchovies - Scopeliformes, largemouths - Saccopharyngiformes, etc. (Fig. 9).
The second group - secondary deep-sea fishes, includes forms whose deep-water nature is historically later. Usually, the families to which the species of this group belong include mainly fish. distributed within the continental step or in the pelagial. Adaptations to life at depths in secondary deep-sea fishes are less specific than in representatives of the first group, and the area of distribution is much narrower; none of them are widely distributed worldwide. Secondary deep-sea fishes usually belong to historically younger groups, mainly perch-like ones - Perciferous. We find deep-sea representatives in the families Cottidae, Liparidae, Zoarcidae, Blenniidae and others.
If in adult fish the decrease in specific gravity is ensured mainly by the swim bladder, then in fish eggs and larvae this is achieved in other ways (Fig. 10). In pelagic, i.e., eggs developing in the water column in a floating state, a decrease in specific gravity is achieved due to one or more fat drops (many flounders), or due to watering the yolk sac (red mullet - Mullus), or by filling a large round yolk - perivitelline cavity [grass carp - Ctenopharyngodon idella (Val.)], or swelling of the shell [eight minnow - Goblobotia pappenheimi (Kroy.)].
The percentage of water contained in pelagic eggs is much higher than that of bottom eggs. So, in the pelagic Mullus caviar, water makes up 94.7% of the live weight, while in the bottom eggs of the smelt lt; - Athedna hepsetus ¦ L. - water contains 72.7%, and in the goby - Neogobius melanostomus (Pall.) - only 62 ,5%.
Pelagic fish larvae also develop peculiar adaptations.
As you know, the larger the area of a body in relation to its volume and weight, the greater the resistance it exerts when immersed and, accordingly, the easier it is for it to stay in a particular layer of water. Devices of this kind in the form of various spines and outgrowths, which increase the surface of the body and help to keep it in the water column, are broken in many pelagic animals, including
Rice. 10. Pelagic fish eggs (not to scale):
1 - anchovy Engraulus encrasichlus L.; 2 - Black Sea herring Caspialosa kessleri pontica (Eich); 3 - skygazer Erythroculter erythrop "erus (Bas.) (cyprinids); 4 - red mullet Mullus barbatus ponticus Essipov (perciformes); 5 - Chinese perch Siniperca chuatsi Bas. (perciformes); 6 - flounder Bothus (Rhombus) maeoticus (Pall.) 7 snakehead Ophicephalus argus warpachowskii Berg (snakeheads) (according to Kryzhanovsky, Smirnov and Soin, 1951 and Smirnov, 1953) *
in fish larvae (Fig. 11). So, for example, the pelagic larva of the bottom monkfish - Lophius piscatorius L. - has long outgrowths of the dorsal and ventral fins, which help it soar in the water column; similar changes in the fins are also observed in the larva of Trachypterus. Larvae of the moon-fish -. Mota mola L. - have huge spines on their body and somewhat resemble an enlarged planktonic alga Ceratium.
In some pelagic fish larvae, the increase in their surface occurs through a strong flattening of the body, as, for example, in the larvae of the river eel, the body of which is much higher and flatter than in adults.
In the larvae of some fish, such as the red mullet, even after the embryo emerges from the shell, a powerfully developed fat drop retains the role of a hydrostatic organ for a long time.
In other pelagic larvae, the role of the hydrostatic organ is performed by the dorsal fin fold, which expands into a huge swollen cavity filled with liquid. This is observed, for example, in the larvae of the sea crucian - Diplodus (Sargus) annularis L.
Life in flowing water in fish is associated with the development of a number of special adaptations. We observe a particularly fast flow in rivers, where sometimes the speed of water movement reaches the speed of a falling body. In rivers originating from mountains, the speed of water movement is the main factor determining the distribution of animals, including fish, along the course of the stream.
Adaptation to life in the river on the course of various representatives of the ichthyofauna goes in different ways. According to the nature of the habitat in a fast stream and the adaptation associated with this, the Hindu researcher Hora (1930) divides all fish inhabiting fast streams into four groups:
^1. Small species that live in stagnant places: in barrels, under waterfalls, in backwaters, etc. These fish are, in their structure, the least adapted to life in a fast stream. Representatives of this group are the Bystrianka - Alburnoides bipunctatus (Bloch.), Lady's stocking - Danio rerio (Ham.), etc.
2. Good swimmers with a strong rolled body, easily overcoming fast currents. This includes many river species: salmon - Salmo salar L., marinka - Schizothorax,
Rice. Fig. 12. Suckers for attachment to the bottom of river fish: catfish - Glyptothorax (left) and Garra from cyprinids (right) (from Nog, 1933 and Annandab, 1919)
^ some Asian (Barbus brachycephalus Kpssl., Barbus "tor, Ham.) and African (Barbus radcliffi Blgr.) species of barbel and many others.
^.3. Small bottom fish, usually living between the stones of the bottom of the stream and swimming from stone to stone. These fish, as a rule, have a spindle-shaped, slightly elongated shape.
These include - many loaches - Nemachil "us, gudgeon" - Gobio, etc.
4. Forms with special attachment organs (suckers; spikes), with the help of which they are attached to bottom objects (Fig. 12). Usually, fish belonging to this group have a flattened dorsoventrally body shape. The sucker is formed either on the lip (Garra and others) or between
Rice. 13. Cross section of various fishes of fast-flowing waters (top row) and slow-flowing or stagnant waters (bottom row). Left nappavo vveokhu - y-.o-
pectoral fins (Glyptothorax), or by fusion of the pelvic fins. This group includes Discognathichthys, many species of the family Sisoridae, and a peculiar tropical family Homalopteridae, etc.
As the current slows down when moving from the upper to the lower reaches of the river, fish begin to appear in the channel, unadapted to overcome high current speeds, reel, minnow, char, sculpin; down In fish living in the waters
zu - bream, crucian carp, carp, roach, red - with Slow current, body
butperka. Fish taken of the same height are more flattened, AND THEY usually
' not so good SWIMMERS,
as inhabitants of fast rivers (Fig. 13). The gradual change in the shape of the body of the fish from the upper to the lower reaches of the river, associated with a gradual change in the speed of the current, is natural. In those places of the river where the current slows down, fish are kept that are not adapted to life in a fast stream, while in places with an extremely fast movement of water, only forms adapted to overcome the current are preserved; typical inhabitants of a fast stream are rheophiles, Van dem Borne, using the distribution of fish along the stream, divides the rivers of Western Europe into separate sections;
- the area of the trout-mountain part of the stream with a fast current and rocky bottom is characterized by fish with a rolled body (trout, char, minnow, sculpin);
- barbel section - flat current, where the flow velocity is still significant; there are already fish with a higher body, such as barbel, dace, etc.;?,
- the section of the bream-flow is slow, the ground is partly silt, partly sand, underwater vegetation appears in the channel, fish with a body flattened from the sides, such as bream, roach, rudd, etc.
usually occurs very gradually, but in general, the areas outlined by Born stand out in most mountain-fed rivers quite clearly, and the patterns he established for the rivers of Europe are preserved both in the rivers of America and Asia and Africa.
(^(^4gt; forms of the same species living in flowing and stagnant water differ in their adaptability to the flow. For example, the grayling - Thymallus arcticus (Pall.) - from Baikal has a higher body and a longer tail stem, while representatives of the same species from the Angara are shorter in body and short-tailed, which is characteristic of good swimmers.Weaker young specimens of river fish (barbels, chars), as a rule, have a lower terete body and a shortened tail compared to adults. In addition, usually in mountain rivers, adults, larger and stronger individuals, stay upstream than juveniles.If you move upstream of the river, then the average size of individuals of the same species, for example, crest-tailed and Tibetan charrs, all increase, and the largest individuals are observed near the upper limit of the distribution of the species (Turdakov, 1939).
UB River currents affect the fish organism not only mechanically, but also indirectly, through other factors. As a rule, fast-flowing water bodies are characterized by * supersaturation with oxygen. Therefore, rheophilic fish are at the same time oxyphilic, i.e., oxygen-loving; and, conversely, fish inhabiting slowly flowing or stagnant waters are usually adapted to different oxygen regimes and tolerate oxygen deficiency better. . -
The current, influencing the nature of the bottom of the stream, and thus the nature of bottom life, naturally affects the feeding of fish. So, in the upper reaches of the rivers, where the soil forms immovable blocks. usually a rich periphyton* can develop, which is the main food for many fish in this section of the river. Because of this, the fish of the upper reaches are characterized, as a rule, by a very long intestinal tract/adapted for the digestion of plant foods, as well as by the development of a horn cover on the lower lip. As you move down the river, the soils become shallower and, under the influence of the current, acquire mobility. Naturally, rich benthic fauna cannot develop on moving soils, and fish pass to feeding on fish or food falling from land. As the current slows down, siltation of the soil gradually begins, the development of benthic fauna, and herbivorous fish species with a long intestinal tract again appear in the channel.
33
The flow in the rivers affects not only the structure of the body of the fish. First of all, the nature of reproduction of river fish changes. Many inhabitants of fast-flowing rivers
3 G. V. Nikolsky
have sticky caviar. Some species lay their eggs by burying them in the sand. American catfish from the genus Plecostomus lay eggs in special caves, other genera (see reproduction) hatch eggs on their ventral side. The structure of the external genital organs also changes. In some species, a shorter sperm motility develops, etc.
Thus, we see that the forms of adaptation of fish to the flow in rivers are very diverse. In some cases, unexpected movements of large masses of water, for example, silt or silt breaks in the dams of mountain lakes, can lead to mass death of the ichthyofauna, as, for example, took place in Chitral (India) in 1929. The speed of the current sometimes serves as an isolating factor, "leading to the separation of the fauna of individual reservoirs and contributing to its isolation. For example, rapids and waterfalls between the large lakes of East Africa are not an obstacle for strong large fish, but are impassable for small ones and lead to the isolation of fauna thus separated sections of water bodies.
"Naturally, the most complex and peculiar adaptations" to life in a fast current are developed in fish that live in mountain rivers, where the speed of movement of water reaches its greatest value.
According to modern views, the fauna of mountain rivers of temperate low latitudes of the northern hemisphere are relics of the ice age. (By the term "relic", we mean those animals and plants whose area of distribution is separated in time or space from the main area of \u200b\u200bdistribution of this faunistic or floristic complex.) "The fauna of mountain streams of tropical and, partially / temperate latitudes of non-glacial origin, but developed as a result of the gradual migration of “organisms into high-altitude reservoirs from the plains. - ¦¦ : \
: For a number of groups, the ways of adaptation: to: life. in mountain streams can be traced quite clearly and can be restored (Fig. 14). --.that;
Both in rivers and in stagnant water bodies, currents have a very strong influence on fish. But while in rivers the main adaptations are developed to the direct mechanical action of moving molasses, the influence of currents in the seas and lakes affects more indirectly - through changes caused by the current - in the distribution of other environmental factors (temperature, salinity, etc.). It is natural, of course, that adaptations to the direct mechanical action of water movement are also developed in fish in stagnant water bodies. The mechanical influence of currents is primarily expressed in the transfer of fish, their larvae and eggs, sometimes over great distances. So, for example, the larvae of
di - Clupea harengus L., hatched off the coast of northern Norway, are carried by the current far to the northeast. The distance from Lofoten - the spawning grounds of herring and to the Kola meridian is covered by herring fry in about three months. The pelagic eggs of many fish also
Єіurtetrnim, five cores.) /
/n-Vi-
/ SshshShyim 9ІURT0TI0YAYAL (РЯУІйІ DDR)
will show
Єіurtotyanim
(meatgg?ggt;im)
are sometimes carried by currents for very considerable distances. So, for example, flounder eggs laid off the coast of France belong to the coast of Denmark, where the release of "" juveniles occurs. The advancement of eel larvae from spawning grounds to European mouths and rivers is largely
noah its part timed |
GlWOStlPHUH-
(sTouczm etc.)
way^-
1І1IM from South to North. leinya catfish of the "YyShІЇ" family pV
Minimum speeds in relation to two main factors
some of the readings are over the mountain streams.; In the diagram, it can be seen
values to which the species has become less rheophilic
fish, apparently, of the order 2- (dz Noga, G930).
10 cm/sec. Hamsa - - Engraulis "¦¦ ¦
encrasichalus L. - starts re- 1
react to the current at a speed of 5 cm/sec, but for many species these threshold reactions have not been established. -
The organ that perceives the movement of water is the cells of the lateral line. In its simplest form, this is in sharks. a number of sensory cells located in the epidermis. In the process of evolution (for example, in a chimera), these cells sink into a canal, which gradually (in bony fish) closes and is connected to the environment only by means of tubules that pierce the scales and form a lateral line, which is far from being developed in different fish in the same way. The lateral line organs are innervated by the nervus facialis and n. vagus. In herring, the lateral line canals have only the head; in some other fish, the lateral line is incomplete (for example, in the apex and some minnows). With the help of the lateral line organs, the fish perceives movement and fluctuations of water. Moreover, in many marine fish, the lateral line serves mainly to sense the oscillatory movements of water, while in river fish it also allows one to orient oneself to the current (Disler, 1955, 1960).
Significantly more than the direct effect, the indirect effect of currents on fish, mainly through changes in the water regime. Cold currents running from north to south allow arctic forms to penetrate far into the temperate region. Thus, for example, the cold Labrador current pushes far to the south the spread of a number of warm-water forms, which move far to the north along the coast of Europe, where the warm current of the Gulf Stream strongly affects. In the Barents Sea, the distribution of individual highly arctic species of the Zoarciaae family is confined to cold water areas located between warm current jets. In the branches of this current, warmer-water fish, such as, for example, mackerel and others, keep.
GTsdens can radically change the chemical regime of a reservoir and, in particular, affect its salinity, introducing more salty or fresh water. Thus, the Gulf Stream brings more saline water into the Barents Sea, and more saline organisms are confined to its jets. formed by fresh waters carried out by Siberian rivers, whitefish and Siberian sturgeon are largely confined in their distribution. the production of organic matter, which allows a few eurythermal forms to develop in mass quantities.Examples of this kind of junction of cold and warm waters are quite common, for example, near the western coast of South America near Chile, on the Newfoundland banks, etc.
A significant role in the life of fish is played by vertical and calic currents of water. The direct mechanical effect of this factor can rarely be observed. Usually, the influence of vertical circulation causes mixing of the lower and upper layers of water, and thereby the alignment of the distribution of temperature, salinity, and other factors, which, in turn, creates favorable conditions for vertical migrations of fish. So, for example, in the Aral Sea, vobla far from the coast in spring and autumn rises at night for poverty in the surface layers, descends into the bottom layers during the day. In the summer, when a pronounced stratification is established, the roach stays all the time in the bottom layers, -
An important role in the life of fish is also played by the oscillatory movements of water. The main form of oscillatory movements of water, which is of the greatest importance in the life of fish, is unrest. Disturbances have various effects on fish, both direct, mechanical, and indirect, and are associated with the development of various adaptations. During strong waves in the sea, pelagic fish usually sink into deeper layers of water, where they do not feel the excitement. The waves in coastal areas have a particularly strong effect on the fish, where the force of the wave reaches up to one and a half tons.
living in the coastal zone, are characterized by special devices that protect themselves, as well as their caviar, from the influence of the surf. Most coastal fish are capable*
per 1 m2. For fish / live /
stay in place in
surf time In against- Fig- 15- Changed into a sucker belly. . l l "fins of marine fish:
HOME case THEY would be on the left - the goby Neogobius; on the right - prickly broken O stones. So, lumpfish Eumicrotremus (from Berg, 1949 and, for example, typical obi-Perm "nova, 1936)
coastal water thieves - various Gobiidae gobies, have ventral fins modified into a sucker, with the help of which the fish are held on stones; a slightly different type of suckers are found in lumpfish - Cyclopteridae (Fig. 15).
In waves, they not only directly mechanically affect the fish, but also have a great indirect effect on them, contributing to the mixing of water and immersion to the depth of the temperature jump layer. So, for example, in the last pre-war years, due to the lowering of the level of the Caspian Sea, as a result of an increase in the mixing zone, the upper boundary of the bottom layer, where biogenic substances accumulate, also decreased. Thus, part of the nutrients entered the cycle of organic matter in the reservoir, causing an increase in the amount of plankton, and thereby, the food supply for the Caspian plankton-eating fish. Another type of oscillatory movements of sea waters, which is of great importance in the life of fish, is tidal Thus, off the coast of North America and in the northern part of the Sea of Okhotsk, the difference between the levels of high and low tide reaches more than 15 m. times, a day, huge masses of water rush through, have special adaptations for life in small puddles ice remaining after low tide. All inhabitants of the intertidal zone (littoral) have a dorsoventrally flattened, serpentine or valky body shape. High-bodied fish, except for flounders lying on their sides, are not found in the littoral. So, in Murman, eelpouts - Zoarces viuiparus L. and butterfish - Pholis gunnelus L. - species with an elongated body shape, as well as large-headed sculpins, mainly Myoxocephalus scorpius L., usually remain in the littoral.
Peculiar changes occur in the fish of the intertidal zone in the biology of reproduction. Many of the fish in particular; sculpins, for the time of spawning, depart from the littoral zone. Some species acquire the ability to give birth, such as the eelpout, whose eggs go through an incubation period in the mother's body. The lumpfish usually lays its eggs below the level of low tide, and in those cases when its caviar dries out, it pours water from its mouth and splashes its tail on it. The most curious adaptation to breeding in the intertidal zone is observed in American fish? ki Leuresthes tenuis (Ayres), which spawns during spring tides in that part of the intertidal zone that is not covered by quadrature tides, so that the eggs develop out of the water in a humid atmosphere. The incubation period lasts until the next syzygy, when the juveniles leave the eggs and go into the water. Similar adaptations for reproduction in the littoral are also observed in some Galaxiiformes. Tidal currents, as well as vertical circulation, also have indirect effects on fish, mixing bottom sediments and thus causing a better assimilation of their organic matter, and thereby increasing the productivity of the reservoir.
Somewhat apart is the influence of such a form of water movement as tornadoes. Capturing huge masses of water from the sea or inland water bodies, tornadoes carry it along with all animals, including fish, over considerable distances. In India, during the monsoons, fish rains often occur, when live fish usually fall to the ground along with the downpour. Sometimes these rains capture quite large areas. Similar fish showers occur in various parts of the world; they are described for Norway, Spain, India and a number of other places. The biological significance of fish rains is undoubtedly primarily expressed in promoting the resettlement of fish, and with the help of fish rains, obstacles can be overcome under normal conditions. fish are irresistible.
Thus / as can be seen from the foregoing, the forms of influence on the “fish of movement! Water are extremely diverse and leave an indelible imprint on the body of the fish in the form of specific adaptations that ensure the existence of the fish in various conditions.
Fish, less than any other group of vertebrates, are associated with a solid substrate as a support. Many species of fish never touch the bottom in their entire lives, but a significant, perhaps most, part of the fish is in close or other connection with the soil of the reservoir. Most often, the relationship between soil and fish is not direct, but is carried out through food objects attached to a particular type of substrate. For example, the confinement of bream in the Aral Sea, at certain times of the year, to gray silty soils is entirely due to the high biomass of the benthos of this soil (benthos serves as food for wood). But in a number of cases there is a connection between the fish and the nature of the soil, caused by the adaptation of the fish to a particular type of substrate. So, for example, burrowing fish are always confined in their distribution to soft soils; fish confined in their distribution to stony bottoms often have a sucker for attachment to bottom objects, etc. Many fish have developed a number of rather complex adaptations for crawling on the bottom. Some fish, sometimes forced to move on land, also have a number of features in the structure of their limbs and tail, adapted to movement on a solid substrate. Finally, the coloration of fish is largely determined by the color and pattern of the ground on which the fish is located. Not only adult fish, but bottom - demersal caviar (see below) and larvae are also in a very close relationship with the soil of the reservoir, on which eggs are deposited or in which larvae are kept.
There are relatively few fish that spend a significant part of their lives buried in the ground. Among cyclostomes, a significant part of the time is spent in the ground, for example, lamprey larvae - sandworms, which may not rise to its surface for several days. The Central European spikelet - Cobitis taenia L. spends considerable time in the ground. Just like the sandworm, it can even feed by digging into the ground. But most species of fish dig into the ground only in times of danger or during the drying up of the reservoir.
Almost all of these fish have a “serpentine-like elongated body and a number of other adaptations!” associated with burrowing. Thus, in the Indian fish Phisoodonbphis boro Ham., which burrows in liquid silt, the nostrils look like tubes and are located on the ventral side of the head (Noga, 1934). This device allows the fish to successfully make its moves with a pointed head, and its nostrils are not clogged with silt.
bodies similar to those movements that a fish makes when swimming. Standing at an angle to the surface of the ground, head down, the fish, as it were, screwed into it.
Another group of burrowing fish has a flat body, such as flounders and rays. These fish usually don't burrow so deep. Their burrowing process takes place in a slightly different way: the fish, as it were, throw soil over themselves and usually do not burrow completely, exposing their head and part of the body.
Fish burrowing into the ground are inhabitants of mainly shallow inland water bodies or coastal areas of the seas. We do not observe this adaptation in fish from the deep parts of the sea and inland waters. Of the freshwater fish that have adapted to digging into the ground, one can point out the African representative of the lungfish - Protopterus, burrowing into the ground of a reservoir and falling into a kind of summer hibernation during a drought. Of the freshwater fish of temperate latitudes, one can name the loach - Misgurnus fossilis L., which usually burrows during the drying of water bodies, the spiny -: Cobitis taenia (L.), for which burying in the ground serves mainly as a means of protection.
Examples of burrowing marine fish include the gerbil, Ammodytes, which also burrows into the sand, mainly to escape pursuit. Some gobies - Gobiidae - hide from danger in shallow burrows dug by them. Flatfish and stingrays are also buried mainly to be less visible.
Some fish, buried in the ground, can exist for quite a long time in wet silt. In addition to the lungfish noted above, often in the silt of dried-up lakes for a very long time (up to a year or more), ordinary crucians can live. This is noted for Western Siberia, Northern Kazakhstan, and the south of the European part of the USSR. There are cases when crucian carp were dug out from the bottom of dried-up lakes with a shovel (Rybkin, 1 * 958; Shn "itnikov, 1961; Goryunova, 1962).
Many fish, although they do not burrow themselves, can penetrate relatively deep into the ground in search of food. Almost all benthivorous fish dig up the soil to a greater or lesser extent. Digging up the soil is usually done by a jet of water released from the mouth opening and carrying small silt particles to the side. Directly swarming movements in benthivorous fish are observed less frequently.
Very often, digging the soil in fish is associated with the construction of a nest. So, for example, nests in the form of a hole where eggs are laid are built by some representatives of the Cichlidae family, in particular, Geophagus brasiliense (Quoy a. Gaimard). To protect themselves from enemies, many fish bury their eggs in the ground, where they
is undergoing development. Caviar developing in the ground has a number of specific adaptations and develops worse outside the ground (see below, p. 168). As an example of marine fish that bury eggs, one can point to atherina - Leuresthes tenuis (Ayres.), and from freshwater - most salmon, in which both eggs and free embryos develop in the early stages, being buried in pebbles, thus protected from numerous enemies. In fish that bury their eggs in the ground, the incubation period is usually very long (from 10 to 100 or more days).
In many fish, the egg shell becomes sticky when it enters the water, due to which the egg is attached to the substrate.
Fish that live on solid ground, especially in the coastal zone or in fast currents, very often have various organs of attachment to the substrate (see p. 32); or - in the form of a sucker formed by modifying the lower lip, pectoral or ventral fins, or in the form of spines and hooks, usually developing on the ossifications of the shoulder and abdominal girdle and fins, as well as the gill cover.
As we have already indicated above, the distribution of many fishes is confined to certain soils, and often close species of the same genus are found on different soils. So, for example, a goby - Icelus spatula Gilb. et Burke - is confined in its distribution to stony-pebble soils, and a closely related species is Icelus spiniger Gilb. - to sandy and silty-sandy. The reasons for the confinement of fish to a certain type of soil, as mentioned above, can be very diverse. This is either a direct adaptation to a given type of soil (soft - for burrowing forms, hard - for attached ones, etc.), or, since a certain nature of the soil is associated with a certain regime of a reservoir, in many cases there is a connection in the distribution of fish with soil through the hydrological regime. And, finally, the third form of connection between the distribution of fish and the ground is the connection through the distribution of food objects.
Many fish that have adapted to crawling on the ground have undergone very significant changes in the structure of the limbs. The pectoral fin serves to support the ground, for example, in the larvae of the polypterus Polypterus (Fig. 18, 3), some labyrinths, such as the Anabas crawler, Trigla, the Periophftialmidae, and many Lophiiformes, for example , monkfish - Lophius piscatorius L. and starfish - Halientea. In connection with the adaptation to movement on the ground, the forelimbs of fish undergo rather strong changes (Fig. 16). The most significant changes occurred in foot-finned Lophiiformes, in their forelimbs a number of features are observed, similar to similar formations in tetrapods. In most fish, the skin skeleton is highly developed, and the primary skeleton is greatly reduced, while in tetrapods, the opposite picture is observed. Lophius occupies an intermediate position in the structure of the limbs; both the primary and skin skeletons are equally developed in it. The two radialia of Lophius bear a resemblance to the tetrapod zeugopodium. The muscles of the limbs of tetrapods are divided into proximal and distal, which are located in two groups.
Rice. 16. Pectoral fins resting on the ground of fish:
I - multifeather (Polypteri); 2 - gurnard (trigles) (Perclformes); 3- Ogcocephaliis (Lophiiformes)
pami, and not a solid mass, thereby allowing pronation and supination. The same is observed in Lophius. However, the musculature of Lophius is homologous to the musculature of other bony fish, and all changes towards the limbs of tetrapods are the result of adaptation to a similar function. Using its limbs as legs, Lophius moves very well along the bottom. Many common features in the structure of the pectoral fins are found in Lophius and polypterus - Polypterus, but in the latter there is a shift of muscles from the surface of the fin to the edges to an even lesser extent than in Lophius. We observe the same or similar direction of changes and the transformation of the forelimb from the organ of swimming into the organ of support in the jumper - Periophthalmus. The jumper lives in mangroves and spends much of its time on land. On the shore, he chases the terrestrial insects that he feeds on. This fish moves on land with jumps that it makes with the help of its tail and pectoral fins.
The trigla has a peculiar device for crawling on the ground. The first three rays of her pectoral fin are isolated and have acquired mobility. With the help of these beams, the trigla crawls along the ground. They also serve the fish as an organ of touch. In connection with the special function of the first three rays, some anatomical changes also occur; in particular, the muscles that set the free rays in motion are much more developed than all the others (Fig. 17).
Rice. 17. Musculature of the rays of the pectoral fin of the gurnard (trigles). Enlarged free ray muscles are visible (from Belling, 1912).
The representative of the labyrinths - the crawler - Anabas, moving but on dry land, uses the pectoral fins for movement, and sometimes also the gill covers.
In the life of fish, oh! "- a significant role is played not only by the soil, but also by solid particles suspended in the water.
Very important in the life of fish is the transparency of water (see p. 45). In small inland water bodies and coastal areas of the seas, water transparency is largely determined by the admixture of suspended mineral particles.
Particles suspended in water affect fish in a variety of ways. The most severe effect on fish is suspended matter in flowing water, where the solids content often reaches up to 4% by volume. Here, first of all, the direct mechanical influence of mineral particles of various sizes borne in water, from several microns to 2-3 cm in diameter, affects. In this regard, the fish of muddy rivers develop a number of adaptations, such as a sharp decrease in the size of the eyes. Short-eyedness is characteristic of shovelnose living in muddy waters, loaches - Nemachilus and various catfish. The reduction in the size of the eyes is explained by the need to reduce the unprotected surface, which can be damaged by the suspension carried by the flow. The small-eyedness of charrs is also connected with the fact that these and bottom fishes are guided by food mainly with the help of the organs of touch. In the process of individual development, their eyes relatively decrease as the fish grows and develops antennae and the transition to bottom feeding associated with this (Lange, 1950).
The presence of a large amount of suspension in the water, of course, should also make it difficult for the fish to breathe. Apparently, in connection with this, in fish living in turbid waters, the mucus secreted by the skin has the ability to precipitate particles suspended in water very quickly. This phenomenon has been studied in most detail for the American flake - Lepidosiren, the coagulating properties of the mucus of which help it live in the thin silt of the Chaco reservoirs. For Phisoodonophis boro Ham. it has also been found that its mucus has a strong ability to precipitate a suspension. Adding one or two drops of mucus secreted by the skin of a fish to 500 cc. cm of turbid water causes sedimentation of suspension in 20-30 sec. Such rapid sedimentation leads to the fact that even in very turbid water, the fish lives, as it were, surrounded by a case of clear water. The chemical reaction of the mucus itself, secreted by the skin, changes when it comes into contact with muddy water. So, it was found that the pH of the mucus in contact with water decreases sharply, falling from 7.5 to 5.0. Naturally, the coagulating property of the mucus is important as a way to protect the gills from clogging with suspended particles. But despite the fact that fish living in turbid waters have a number of adaptations to protect themselves from the effects of suspended particles, nevertheless, if the amount of turbidity exceeds a certain value, the death of fish may occur. In this case, death, apparently, occurs from suffocation as a result of clogging of the gills with sediment. Thus, there are cases when during heavy rains - forces, with an increase in the turbidity of the streams by dozens of times, there was a mass death of fish. A similar phenomenon has been recorded in the mountainous regions of Afghanistan and India. At the same time, even fish so adapted to life in troubled waters as the Turkestan catfish Glyptosternum reticulatum Me Clel perished. - and some others.
LIGHT, SOUND, OTHER VIBRATIONAL MOVEMENTS AND FORMS OF RADIANT ENERGY
Light and, to a lesser extent, other forms of radiant energy play a very important role in the life of fish. Of great importance in the life of fish are other oscillatory movements with a lower frequency of oscillations, such as, for example, sounds, infra-, and apparently, ultrasounds. Electric currents, both natural and radiated by fish, are also of known importance for fish. With its sense organs, the fish is adapted to perceive all these influences.
j Light /
Lighting is very important, both direct and indirect, in the life of fish. In most fish, the organ of vision plays a significant role in orienting during movement to prey, a predator, other individuals of the same species in a flock, to stationary objects, etc.
Only a few fish have adapted to live in complete darkness in caves and in artesian waters, or in very weak artificial light produced by animals at great depths. "
The structure of the fish - its organ of vision, the presence or absence of luminous organs, the development of other sensory organs, color, etc. is associated with the characteristics of lighting. Fish behavior is also largely related to illumination, in particular, the daily rhythm of its activity and many other aspects of life. Light has a certain effect on the course of fish metabolism, on the maturation of reproductive products. Thus, for most fish, light is a necessary element of their environment.
The conditions of illumination in water can be very different and depend, in addition to the strength of illumination, on the reflection, absorption and scattering of light, and many other factors. An essential factor determining the illumination of water is its transparency. The transparency of water in various reservoirs is extremely diverse, ranging from the muddy, coffee-colored rivers of India, China and Central Asia, where an object immersed in water becomes invisible as soon as it is covered with water, and ending with the transparent waters of the Sargasso Sea (transparency 66.5 m), the central part of the Pacific Ocean (59 m) and a number of other places where the white circle - the so-called Secchi disk, becomes invisible to the eye only after diving to a depth of more than 50 m. the same depth are very different, not to mention different depths, because, as you know, with depth, the degree of illumination rapidly decreases. So, in the sea off the coast of England, 90% of the light is absorbed already at a depth of 8-9 M.
Fish perceive light with the help of the eye and light-sensitive kidneys. The specifics of lighting in water determines the specifics of the structure and function of the fish's eye. Beebe's experiments (Beebe, 1936) showed that the human eye can still distinguish traces of light under water at a depth of about 500 m. even after a 2-hour exposure does not show any changes. Thus, animals living from a depth of about 1,500 m to the maximum depths of the world's oceans over 10,000 m are completely unaffected by daylight and live in complete darkness, disturbed only by light emanating from the luminous organs of various deep-sea animals.
-Compared to Man and other terrestrial vertebrates, fish are more myopic; her eye has a much shorter focal length. Most fish clearly distinguish objects within about one meter, and the maximum range of vision of fish, apparently, does not exceed fifteen meters. Morphologically, this is determined by the presence in fish of a more convex lens compared to terrestrial vertebrates. In bony fish: accommodation of vision is achieved using the so-called sickle-shaped process, and in sharks, the ciliated body. "
The horizontal field of view of each eye in an adult fish reaches 160-170 ° (data for trout), i.e., more than in humans (154 °), and the vertical field of view in fish is 150 ° (in humans - 134 °). However, this vision is monocular. The binocular field of view in a trout is only 20-30°, while in humans it is 120° (Baburina, 1955). The maximum visual acuity in fish (minnow) is achieved at 35 lux (in humans - at 300 lux), which is associated with the adaptation of the fish to less, compared to air, illumination in water. The quality of a fish's vision is related to the size of its eye.
Fish whose eyes are adapted to see in the air have a flatter lens. In the American four-eyed fish1 - Anableps tetraphthalmus (L.), the upper part of the eye (lens, iris, cornea) is separated from the lower by a horizontal septum. In this case, the upper part of the lens has a flatter shape than the lower part, adapted for vision in water. This fish, swimming near the surface, can simultaneously observe what is happening both in the air and in the water.
In one of the tropical species of blennies, Dialotnus fuscus Clark, the eye is divided across by a vertical septum, and the fish can see with the front of the eye outside the water, and with the back - in the water. Living in the depressions of the dry zone, it often sits with the front of its head out of the water (Fig. 18). However, fish can also see out of the water, which do not expose their eyes to the air.
While under water, the fish can see only those objects that are at an angle of not more than 48.8° to the vertical of the eye. As can be seen from the above diagram (Fig. 19), the fish sees air objects as if through a round window. This window expands when it sinks and narrows when it rises to the surface, but the fish always sees at the same angle of 97.6° (Baburina, 1955).
Fish have special adaptations for seeing in different light conditions. The rods of the retina are adapted to
Rice. 18. Fish, whose eyes are adapted to see both in water * And in the air. Above - four-eyed fish Anableps tetraphthalmus L.;
on the right is a section of her eye. '
Below, the four-eyed blenny Dialommus fuscus Clark; "
a - axis of air vision; b - dark partition; c - axis of underwater vision;
g - lens (according to Schultz, 1948), ?
To receive weaker light, and in daylight, they sink deeper between the pigment cells of the retina, "which close them from light rays. Cones, adapted to perceive brighter light, approach the surface in strong light.
Since the upper and lower parts of the eye are illuminated differently in fish, the upper part of the eye perceives more rarefied light than the lower part. In this regard, the lower part of the retina of the eye of most fish contains more cones and fewer rods per unit area. -
Significant changes occur in the structures of the organ of vision in the process of ontogenesis.
In juvenile fish that consume food from the upper layers of water, an area of increased sensitivity to light is formed in the lower part of the eye, but when they switch to feeding on benthos, sensitivity increases in the upper part of the eye, which perceives objects located below.
The intensity of light perceived by the fish's organ of vision does not seem to be the same in different species. American
Horizon \ Stones of Cerek \ to
* Window Y
.Shoreline/ "M
Rice. 19. The visual field of a fish looking up through the calm surface of the water. Above - the surface of the water and the airspace seen from below. Below is the same diagram from the side. Rays falling from above on the surface of the water are refracted inside the "window" and enter the eye of the fish. Inside the angle of 97.6°, the fish sees the surface space; outside this angle, it sees the image of objects at the bottom reflected from the surface of the water (from Baburina, 1955)
fish Lepomis from the family, Centrarchidae eye still picks up light with an intensity of 10~5 lux. A similar strength of illumination is observed in the most transparent water of the Sargasso Sea at a depth of 430 m from the surface. Lepomis is a freshwater fish that lives in relatively shallow waters. Therefore, it is very likely that deep-sea fish, especially those with telescopic visual organs of vision, are able to respond to much weaker lighting (Fig. 20).
In deep-sea fish, a number of adaptations are developed in connection with poor illumination at depths. In many deep-sea fishes, the eyes reach enormous sizes. For example, in Bathymacrops macrolepis Gelchrist from the Microstomidae family, the eye diameter is about 40% of the head length. In Polyipnus from the Sternoptychidae family, the eye diameter is 25–32% of the head length, while in Myctophium rissoi (Cosso) from the family
Rice. 20. Organs of vision of some deep-sea fishes, Left - Argyropelecus affinis Garm.; right - Myctophium rissoi (Cosso) (from Fowler, 1936)
of the Myctophidae family - even up to 50%. Very often, in deep-sea fish, the shape of the pupil also changes - it becomes oblong, and its ends go beyond the lens, due to which, just as by a general increase in the size of the eye, its light-absorbing ability increases. Argyropelecus from the Sternoptychidae family has a special light in the eye.
Rice. 21. Larva of deep-sea fish I diacanthus (ref. Stomiatoidei) (from Fowler, 1936)
a stretching organ that maintains the retina in a state of constant irritation and thereby increases its sensitivity to light rays entering from outside. In many deep-sea fishes, the eyes become telescopic, which increases their sensitivity and expands the field of view. The most curious changes in the organ of vision take place in the larvae of the deep-sea fish Idiacanthus (Fig. 21). Her eyes are located on long stalks, which greatly increases the field of view. In adult fish, the stalked eyes are lost.
Along with the strong development of the organ of vision in some deep-sea fishes, in others, as already noted, the organ of vision either significantly decreases (Benthosaurus and others) or disappears completely (Ipnops). Along with the reduction of the organ of vision, these fish usually develop various outgrowths on the body: the rays of paired and unpaired fins or antennae are greatly elongated. All these outgrowths serve as organs of touch and, to a certain extent, compensate for the reduction of the organs of vision.
The development of the organs of vision in deep-sea fish living at depths where daylight does not penetrate is due to the fact that many animals of the depths have the ability to glow.
49
Glow in animals, inhabitants of the deep sea, is a very common phenomenon. About 45% of fish inhabiting depths over 300 m possess luminous organs. In the simplest form, the organs of luminescence are present in deep-sea fish from the Macruridae family. Their skin mucous glands contain a phosphorescent substance that emits a faint light, creating
4 G. V. Nikolsky
giving the impression that the whole fish is glowing. Most other deep-sea fishes have special luminous organs, sometimes quite complex. The most complex luminous organ of fish consists of an underlying layer of pigment, followed by a reflector, above which are luminous cells, covered with a lens on top (Fig. 22). The location of the light
5
Rice. 22. The luminous organ of Argyropelecus.
¦ a - reflector; b - luminous cells; c - lens; d - underlying layer (from Brier, 1906-1908)
The number of organs in different fish species is very different, so that in many cases it can serve as a systematic feature (Fig. 23).
Lighting usually occurs as a result of contact
Rice. 23. Scheme of arrangement of luminous organs in the schooling deep-sea fish Lampanyctes (from Andriyashev, 1939)
the secret of luminous cells with water, but in the fish of Asgoroth. japonicum Giinth. reduction is caused by microorganisms located in the gland. "The intensity of the glow depends on a number of factors and varies even in the same fish. Many fish glow especially intensely during the breeding season.
What is the biological significance of the glow of deep-sea fish,
It has not yet been fully elucidated, but, undoubtedly, the role of the luminous organs is different for different fish: In Ceratiidae, the luminous organ, located at the end of the first ray of the dorsal fin, apparently serves to lure prey. Perhaps the luminous organ at the end of Saccopharynx's tail performs the same function. The luminous organs of Argyropelecus, Lampanyctes, Myctophium, Vinciguerria and many other fish located on the sides of the body allow them to find individuals of the same species in the dark at great depths. Apparently, this is of particular importance for fish that keep in schools.
In complete darkness, not disturbed even by luminous organisms, cave fish live. According to how closely animals are associated with life in caves, they are usually divided into the following groups: 1) troglobionts - permanent inhabitants of caves; 2) troglophiles - the predominant inhabitants of caves, but also found in other places,
- trogloxens are widespread forms that also enter caves.
As compensation for the organ of vision degenerating in cave fish, they usually have very strongly developed lateral line organs, especially on the head, and tactile organs, such as the long whiskers of Brazilian cave catfish from the Pimelodidae family.
The fish that inhabit the caves are very diverse. At present, representatives of a number of groups of cyprinids are known in the caves - Cypriniformes (Aulopyge, Paraphoxinus, Chondrostoma, American catfish, etc.), Cyprinodontiformes (Chologaster, Troglichthys, Amblyopsis), a number of species of gobies, etc.
Illumination conditions in water differ from those in air not only in intensity, but also in the degree of penetration into the depth of water of individual rays of the spectrum. As is known, the coefficient of absorption by water of rays with different wavelengths is far from the same. Red rays are most strongly absorbed by water. When passing a layer of water of 1 m, 25% of red is absorbed *
rays and only 3% violet. However, even violet rays at a depth of more than 100 m become almost indistinguishable. Consequently, at the depths of the fish poorly distinguish colors.
The visible spectrum perceived by fish is somewhat different from the spectrum perceived by terrestrial vertebrates. Different fish have differences associated with the nature of their habitat. Fish species living in the coastal zone and in
Rice. 24. Cave fish (from top to bottom) - Chologaster, Typhlichthys: Amblyopsis (Cvprinodontiformes) (from Jordan, 1925)
surface layers of water, have a wider visible spectrum than fish living at great depths. The sculpin - Myoxocephalus scorpius (L.) - is an inhabitant of shallow depths, perceives colors with a wavelength from 485 to 720 mkm, and the stellate stingray that keeps at great depths - Raja radiata Donov. - from 460 to 620 mmk, haddock Melanogrammus aeglefinus L. - from 480 to 620 mmk (Protasov and Golubtsov, 1960). At the same time, it should be noted that the reduction in visibility occurs, first of all, due to the long-wavelength part of the spectrum (Protasov, 1961).
The fact that most species of fish distinguish colors is proved by a number of observations. Apparently, only some cartilaginous fishes (Chondrichthyes) and cartilaginous ganoids (Chondrostei) do not distinguish colors. The rest of the fish distinguish colors well, which has been proved, in particular, by many experiments using the conditioned reflex technique. For example, the minnow - Gobio gobio (L.) - could be taught to take food from a cup of a certain color.
It is known that fish can change the color and pattern of the skin depending on the color of the ground on which they are located. At the same time, if the fish, accustomed to black soil and having changed color accordingly, were given a choice of soils of different colors, then the fish usually chose the soil to which it was accustomed and the color of which corresponds to the color of its skin.
Particularly sharp changes in body color on various soils are observed in flounders.
At the same time, not only the tone changes, but also the pattern, depending on the nature of the soil on which the fish is located. What is the mechanism of this phenomenon is not yet clear. It is only known that a change in color occurs as a result of a corresponding irritation of the eye. Semner (Sumner, 1933), putting transparent colored caps on the eyes of the fish, caused it to change color to match the color of the caps. The flounder, whose body is on the ground of one color, and the head is on the ground of another color, changes the color of the body according to the background on which the head is located (Fig. 25). "
Naturally, the color of the body of a fish is closely related to the conditions of illumination.
It is usually customary to distinguish the following main types of fish coloration, which are an adaptation to certain habitat conditions.
Pelagic coloration - bluish or greenish back and silvery sides and abdomen. This type of coloration is characteristic of fish living in the water column (herring, anchovies, bleak, etc.). The bluish back makes the fish hardly noticeable from above, and the silvery sides and belly are poorly visible from below against the background of a mirror surface.
Overgrown coloration - 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 the tropical zone, can be very brightly colored.
Examples of fish with overgrown coloration are: common perch and pike - from freshwater forms; sea scorpion ruff, many wrasses and coral fish are from sea.
Bottom coloration - dark back and sides, sometimes with darker stains and a light belly (in flounders, the side facing the ground is light). Bottom fish living above the pebbly soil of rivers with clear water usually have black spots on the sides of the body, sometimes slightly elongated in the dorsal direction, sometimes located in the form of a longitudinal strip (the so-called channel coloration). Such coloration is characteristic, for example, of salmon fry in the river period of life, grayling fry, common minnow and other fish. This coloration makes the fish hardly noticeable against the background of pebbly soil in clear flowing water. Bottom fish in stagnant waters usually do not have bright dark spots on the sides of the body, or they have blurred outlines.
The schooling coloration of fish is especially prominent. This coloration facilitates the orientation of individuals in a flock towards each other (see p. 98 below). It appears as either one or more spots on the sides of the body or on the dorsal fin, or as a dark stripe along the body. An example is the coloration of the Amur minnow - Phoxinus lagovskii Dyb., juveniles of the prickly bitterling - Acanthorhodeus asmussi Dyb., some herring, haddock, etc. (Fig. 26).
The coloration of deep-sea fishes is very specific. Usually these fish are colored either dark, sometimes almost black or red. This is explained by the fact that even at relatively shallow depths, the red color under water seems black and is poorly visible to predators.
A slightly different color pattern is observed in deep-sea fish, which have organs of luminescence on their bodies. These fish have a lot of guanine in their skin, which gives the body a silvery sheen (Argyropelecus, etc.).
As is well known, the coloration of fish does not remain unchanged during individual development. It changes during the transition of fish, in the process of development, from one habitat to another. Thus, for example, the coloration of juvenile salmon in a river has the character of a channel type, when it descends into the sea, it is replaced by a pelagic one, and when the fish return back to the river for breeding, it again acquires a channel character. Coloring can change during the day; Thus, in some representatives of Characinoidei, (Nannostomus), the coloration is flocking during the day - a black stripe along the body, and at night transverse striping appears, i.e., the color becomes overgrown.
Rice. 26, Types of schooling coloration in fish (from top to bottom): Amur minnow - Phoxinus lagowsku Dyb.; prickly bitterling (juvenile) - Acanthorhodeus asmussi Dyb.; haddock - Melanogrammus aeglefinus (L.) /
The so-called mating coloration in fish is often
protective device. Mating coloration is absent in fish spawning at depths and is usually poorly expressed in fish spawning at night.
Different types of fish react differently to light. Some are attracted by light: sprat Clupeonella delicatula (Norm.), saury Cololabis saifa (Brev.), etc. Some fish, such as carp, avoid light. The light is usually attracted by fish that feed by orienting themselves with the help of the organ of vision / mainly the so-called "visual planktophages". The reaction to light also changes in fish that are in different biological states. Thus, females of anchovy kilka with flowing eggs are not attracted to light, but those that have spawned or are in a pre-spawning state go to light (Shubnikov, 1959). In many fish, the nature of the reaction to light also changes in the process of individual development. Juveniles of salmon, minnow and some other fish hide under stones from the light, which ensures their safety from enemies. In sandworms - lamprey larvae (cyclostomes), in which the tail carries light-sensitive cells - this feature is associated with life in the ground. Sandworms respond to illumination of the tail area by swimming movements, burrowing deeper into the ground.
. What are the reasons for the reaction of fish to light? There are several hypotheses on this issue (see Protasov, 1961 for a review). J. Loeb (1910) considers the attraction of fish to light as a forced, non-adaptive movement - as a phototaxis. Most researchers consider the reaction of fish to light as an adaptation. Franz (cited by Protasov) believes that light has a signal value, in many cases serving as a signal of danger. S. G. Zusser (1953) considers that the reaction of fish to light is a food reflex.
Undoubtedly, in all cases, the fish reacts to light adaptively. In some cases, this may be a defensive reaction when the fish avoids the light, in other cases, the approach to the light is associated with the extraction of food. At present, a positive or negative reaction of fish to light is used in fishing (Borisov, 1955). The fish, attracted by the light to form clusters around the light source, are then caught either with net tools or pumped onto the deck by a pump. Fish that react negatively to light, such as carp, with the help of light are expelled from places that are inconvenient for fishing, for example, from burrowed sections of the pond.
The importance of light in the life of fish is not limited to its connection with vision. Illumination is of great importance for the development of fish. In many species, the normal course of metabolism is disturbed if they are forced to develop in light conditions that are not characteristic of them (those adapted to development in the light are marked in the dark, and vice versa). This is clearly shown by N. N. Disler (1953) using the example of chum salmon development in the light (see below, p. 193).
Light also has an effect on the course of maturation of the reproductive products of fish. Experiments on the American char, S*alvelinus foritinalis (Mitchill), have shown that in experimental fish exposed to enhanced light, maturation occurs earlier than in controls exposed to normal light. However, in fish under high mountain conditions, apparently, just as in some mammals under conditions of artificial illumination, light, after stimulating the increased development of the gonads, can cause a sharp drop in their activity. In this regard, the ancient alpine forms developed an intense coloration of the peritoneum, which protects the gonads from excessive exposure to light.
The dynamics of illumination intensity during the year largely determines the course of the sexual cycle in fish. The fact that in tropical fish reproduction occurs throughout the year, and in fish of temperate latitudes only at certain times, is largely due to the intensity of insolation.
A peculiar protective adaptation from light is observed in the larvae of many pelagic fish. Thus, in the larvae of the herring genera Sprattus and Sardina, a black pigment develops above the neural tube, which protects the nervous system and underlying organs from excessive exposure to light. With resorption of the yolk sac, the pigment above the neural tube in fry disappears. Interestingly, closely related species that have bottom eggs and larvae that stay in the bottom layers do not have such a pigment.
The sun's rays have a very significant effect on the course of metabolism in fish. Experiments carried out on gambusia (Gambusia affitiis Baird, et Gir.),. have shown that in mosquito fish deprived of light, vitamin deficiency develops rather quickly, causing, first of all, the loss of the ability to reproduce.
Sound and other vibrations
As you know, the speed of sound propagation in water is greater than in air. Otherwise, sound absorption in water also occurs.
Fish perceive both mechanical and infrasonic, sound and, apparently, ultrasonic vibrations. Water currents, mechanical and infrasonic vibrations with a frequency of 5 to 25 hertz [I] are perceived by the lateral line organs of fish, and vibrations from 16 to 13,000 hertz are perceived by auditory labyrinth, more precisely, its lower part - Sacculus and Lagena (the upper part serves as an organ of balance).In some species of fish, oscillations with a wavelength of 18 to 30 hertz, i.e., located on the border of infrasonic and sound waves, are perceived as lateral line organs, Differences in the nature of the perception of vibrations in different fish species are shown in Table 1.
In the perception of sound, the swim bladder also plays an important role, apparently acting as a resonator. Since sounds travel faster and farther in water, their perception in water is easier. Sounds do not penetrate well from air into water. From water to air - several1
Table 1
The nature of sound vibrations perceived by different fish
| | Frequency in hertz |
|
| fish species | | |
| | from | BEFORE |
| Phoxinus phoxinus (L.) | 16 | 7000 |
| Leuciscus idus (L.) at. ¦ | 25 | 5524 |
| Carassius auratus (L.). | 25 | 3480 |
| Nemachilus barbatulus (L.) | 25 | 3480 |
| Amiurus nebulosus Le Sueur | 25 | 1300 |
| Anguilla anguilla (L.) | 36 | 650 . |
| Lebistes reticulatus Peters | 44 | 2068 |
| Corvina nigra C.V | 36 | 1024 |
| Diplodus annularis (L.) | 36 | 1250 |
| ¦Gobius niger L. | 44 | 800 |
| Periophthalmus koelreiteri (Pallas) | 44 | 651 |
better, since the pressure of sound in water is much stronger than in air.
Fish can not only hear, many species of fish can make sounds themselves. The organs by which fish make sounds are different. In many fish, such an organ is the swim bladder, which is sometimes equipped with special muscles. With the help of the swim bladder, sounds are made by slabs (Sciaenidae), wrasses (Labridae), etc. In catfish (Siluroidei), the organs that make sound are the rays of the pectoral fins in combination with the bones of the shoulder girdle. In some fish, sounds are made with the help of pharyngeal and jaw teeth (Tetrodontidae).
The nature of the sounds made by fish is very different: they resemble drum beats, croaking, grunting, whistling, grumbling. The sounds made by fish are usually divided into “biological”, i.e., specially made by fish and having an adaptive value, and “mechanical”, made by fish when moving, feeding, digging the soil, etc. The latter usually do not have an adaptive value and , on the contrary, they often unmask oyba (Malyukina and Protasov, 1960).
Among tropical fish, there are more species that make "biological" sounds than among fish inhabiting reservoirs of high latitudes. The adaptive meaning of the sounds made by fish is different. Often sounds are made by fish especially
intensively during reproduction and serve, apparently, to attract one sex to the other. This was noted in croakers, catfish and a number of other fish. These sounds can be so strong that they can be used by fishermen to find concentrations of spawning fish. Sometimes you don't even need to submerge your head in water to detect these sounds.
For some croakers, the sound is also important when fish come into contact in a feeding flock. Thus, in the area of Beaufort (Atlantic coast of the USA), the most intense sounding of gorbyls falls on the dark time of the day from 21:00 to 02:00 and falls on the period of the most intensive feeding (Fish, 1954).
In some cases, the sound is intimidating. Nesting killer whales (Bagridae) seem to scare off enemies with the creaking sounds they make with their fins. Opsanus tau, (L.) from the Batrachoididae family also makes special sounds when it guards its eggs.
The same type of fish can make different sounds, differing not only in strength, but also in frequency. So, Caranx crysos (Mitchrll) makes two types of sounds - croaking and rattling. These sounds differ in wavelength. Different in strength and frequency are the sounds made by males and females. This is noted, for example, for sea bass - Morone saxatilis Walb. from Serranidae, in which males produce stronger sounds, and with a greater amplitude of frequencies (Fish, 1954). Differ in the nature of the sounds made and young fish from old ones. The difference in the nature of the sounds made by males and females of the same species is often associated with corresponding differences in the structure of the sound-producing apparatus. So, in male haddock - Melanogrammus aeglefinus (L.) - the "drum muscles" of the swim bladder are much more developed than in females. Particularly significant development of this muscle is achieved during spawning (Tempelman a. Hoder, 1958).
Some fish are very sensitive to sounds. At the same time, some sounds of fish scare away, while others attract. On the sound of the motor or the impact of the oar on the side of the boat, salmon often jumps out of the water, standing on pits in the rivers in the pre-spawning time. The noise causes the Amur silver carp Hypophthalmichthys molitrix (Val.) to jump out of the water. On the reaction of fish to Sound, the use of sound when catching fish is based. So, when catching mullets with “bast mats”, frightened by the sound, the fish jumps out. water and falls on special mats laid out on the surface, usually in the form of a semicircle, with raised edges. When fishing for pelagic fish with a purse seine, sometimes a special bell is lowered into the seine gate, including
and turning it off, which scares the fish away from the gate of the seine during pursing (Tarasov, 1956).
Sounds are also used to attract fish to the place of fishing. From the dean's yaor.iaveeten fishing for catfish "on a shred". Catfish are attracted to the place of fishing by peculiar gurgling sounds.
Powerful ultrasonic vibrations can kill fish (Elpiver, 1956).
By the sounds made by the fish, it is possible to detect their clusters. Thus, Chinese fishermen detect spawning aggregations of the large yellow perch Pseudosciaena crocea (Rich.) by the sounds made by the fish. Having approached the supposed place of accumulation of fish, the foreman of the fishermen lowers a bamboo pipe into the water and listens to the fish through it. In Japan, special radio beacons have been installed, "tuned" to the sounds made by some commercial fish. When a school of fish of this species approaches the buoy, it begins to send appropriate signals, notifying fishermen of the appearance of fish.
It is possible that the sounds made by fish are used by them as an echometric device. Location by perceiving sounds is especially common, apparently, in deep-sea fish. In the Atlantic, in the Porto Rico region, it was found that biological sounds made, apparently, by deep-sea fish, were then repeated in the form of a weak reflection from the bottom (Griffin, 1950) .. Protasov and Romanenko showed that the beluga makes rather strong sounds, sending which , it can detect objects that are up to 15 .and further away from it.
Electric currents, electromagnetic oscillations
In natural waters, there are weak natural electrical currents associated with both terrestrial magnetism and solar activity. Natural Teluric currents have been established for the Barents and Black Seas, but they apparently exist in all significant water bodies. These currents are undoubtedly of great biological importance, although their role in biological processes in water bodies is still very poorly understood (Mironov, 1948).
Fish subtly react to electrical currents. At the same time, many species can not only produce electrical discharges themselves, but, apparently, also create an electromagnetic field around their body. Such a field, in particular, is established around the head region of the lamprey - Petromyzon matinus (L.).
Fish can send and receive electrical discharges with their senses. The discharges produced by fish can be of two types: strong, serving for attack or defense (see p. 110 below), or weak, having a signal
meaning. In the sea lamprey (cyclostomes), a voltage of 200-300 mV, which is created near the front of the head, apparently serves to detect (by changes in the field created) objects approaching the head of the lamprey. It is highly probable that the "electrical organs" described by Stensio (Stensio, P)27) in cephalaspids had a similar function (Yerekoper and Sibakin 1956, 1957). Many electric eels produce weak, rhythmic discharges. The number of discharges varied in the six studied species from 65 to 1000 days. The number of discharges also varies depending on the condition of the fish. So, in a calm state Mormyrus kannume Bui. produces one pulse per second; when disturbed, it sends up to 30 pulses per second. Floating hymnarch - Gymnarchus niloticus Cuv. - sends pulses with a frequency of 300 pulses per second.
Perception of electromagnetic vibrations in Mormyrus kannume Bui. carried out with the help of a number of receptors located at the base of the dorsal fin and innervated by the head nerves extending from the hindbrain. In Mormyridae, impulses are sent by an electrical organ located on the caudal peduncle (Wright, 1958).
Different types of fish have different susceptibility to the effects of electric current (Bodrova and Krayukhin, 1959). Of the studied freshwater fish, pike turned out to be the most sensitive, the least sensitive were tench and burbot. Weak currents are perceived mainly by fish skin receptors. Higher voltage currents also act directly on the nerve centers (Bodrova and Krayukhin, 1960).
According to the nature of the reaction of fish to electric currents, three phases of action can be distinguished.
The first phase, when the fish, having fallen into the field of action of the current, shows anxiety and tries to get out of it; in this case, the fish tends to take a position in which the axis of its body would be parallel to the direction of the current. The fact that fish react to an electromagnetic field is now confirmed by the development of conditioned reflexes in fish to it (Kholodov, 1958). When a fish enters the field of action of the current, its breathing rate quickens. Fish have a species-specific response to electric currents. So the American catfish - Amiurus nebulosus Le Sueur - reacts to the current more strongly than the goldfish - Carassius auratus (L.). Apparently, fish with highly developed receptors in the skin react more acutely to tok (Bodrova and Krayukhin, 1958). In the same species of fish, larger individuals react earlier to the current than smaller ones.
The second phase of the action of the current on the fish is expressed in the fact that the fish turns its head towards the anode and swims towards it, reacting very sensitively to changes in the direction of the current, even very slight ones. Possibly, the orientation of fish during migration to the sea to Teluric currents is associated with this property.
The third phase is galvanonarcosis and the subsequent death of the fish. The mechanism of this action is associated with the formation of acetylcholine in the blood of fish, which acts as a drug. At the same time, breathing and cardiac activity of the fish are disturbed.
In fisheries, electric currents are used when catching fish, by directing its movement towards fishing gear or by causing a state of shock in the fish. Electric currents are also used in electric barriers to keep fish out of the turbines of hydroelectric stations, into irrigation canals, to direct fish to the mouths of fish passages, etc. (Gyul'badamov, 1958; Nusenbeum, 1958).
X-rays and radioactivity
X-rays have a sharp negative effect on adult fish, as well as on eggs, embryos and larvae. As shown by the experiments of G. V. Samokhvalova (1935, 1938), carried out on Lebistes reticulatus, a dose of 4000 g is lethal for fish. Smaller doses when exposed to the gonad Lebistes reticulatus cause a decrease in litter and degeneration of the gland. Irradiation of young immature males causes them to underdevelop secondary sexual characteristics.
When penetrating into water, "X-rays quickly lose their strength. As shown in fish, at a depth of 100 m, the strength of X-rays is reduced by half (Folsom and Harley, 1957; Publ. 55I).
Radioactive radiation has a stronger effect on fish eggs and embryos than on adult organisms (Golovinskaya and Romashov, 1960).
The development of the nuclear industry, as well as the testing of atomic hydrogen bombs, led to a significant increase in the radioactivity of air and water and the accumulation of radioactive elements in aquatic organisms. The main radioactive element that is important in the life of organisms is strontium 90 (Sr90). Strontium enters the fish body mainly through the intestines (predominantly through the small intestines), as well as through the gills and skin (Danilchenko, 1958).
The bulk of strontium (50-65%) is concentrated in the bones, much less - in the viscera (10-25%) and gills (8-25%), and quite a bit - in the muscles (2-8%). But strontium, which is deposited mainly in the bones, causes the appearance of radioactive yttrium -I90 in the muscles.
Fish accumulate radioactivity both directly from sea water and from other organisms that serve them as food.
Accumulation of radioactivity in young fish is faster than in adults, which is associated with a higher metabolic rate in the former.
More mobile fish (tunas, Cybiidae, etc.) remove radioactive strontium from their bodies faster than inactive ones (for example, Tilapia), which is associated with different metabolic rates (Boroughs, Chipman, Rice, Publ, 551, 1957). In fish of the same species located in a similar environment, as shown in the example of the eared perch - Lepomis, the amount of radioactive strontium in the bones can vary by more than five pa? (Krumholz, Goldberg, Boroughs, 1957* Publ. 551). At the same time, the radioactivity of fish can be many times higher than the radioactivity of the water in which it lives. Thus, on Tilapia, it was found that when fish were kept in radioactive water, their radioactivity, compared with water, was the same after two days, and six times higher after two months (Moiseev, 1958).
The accumulation of Sr9° in the bones of fish causes the development of the so-called Urov's disease / associated with a violation of calcium metabolism. Human consumption of radioactive fish is contraindicated. Since the half-life of strontium is very long (about 20 years), and it is firmly held in the bone tissue, the fish remain infected for a long time. However, the fact that strontium is concentrated mainly in the bones makes it possible to use boneless fish fillets in food after a relatively short aging in storage (refrigerators), since ytrium concentrated in meat has a short half-life,
/water temperature /
In the life of fish, water temperature is of great importance.
Like other poikilthermal, i.e., with a variable body temperature, fish animals are more dependent on the temperature of the surrounding water than homothermal animals. Moreover, the main difference between them* lies in the quantitative side of the process of heat generation. In cold-blooded animals, this process proceeds much more slowly than in warm-blooded animals, which have a constant temperature. So, a carp, weighing 105 g, releases 10.2 kcal of heat per kilogram per day, and a starling, weighing 74 g, already 270 kcal.
In most fish, the body temperature differs by only 0.5-1 ° from the temperature of the surrounding water, and only in tuna this difference can reach more than 10 ° C.
Changes in the rate of metabolism in fish are closely related to changes in the temperature of the surrounding water. In many cases! temperature changes act as a signal factor, as a natural stimulus that determines the beginning of a particular process - spawning, migration, etc.
The rate of development of fish is also largely related to changes in temperature. Within a certain temperature range, a direct dependence of the development rate on temperature change is often observed.
Fish can live in a wide variety of temperatures. The highest temperature above + 52 ° C is carried by a fish from the Cyprinodontidae family - Cyprinodoti macularius Baird.- et Gir., which lives in small hot springs in California. On the other hand, crucian carp - Carassius carassius (L.) - and dahlia, or black fish * Dallia pectoralis Bean. - withstands even freezing, however, provided that the body juices remain unfrozen. Polar cod - Boreogadus saida (Lep.) - leads an active lifestyle at a temperature of -2°C.
Along with the adaptability of fish to certain temperatures (high or low), the amplitude of temperature fluctuations at which the same species can live is also very important for the possibility of their settlement and life in various conditions. This temperature range for different fish species is very different. Some species can withstand fluctuations of several tens of degrees (for example, crucian carp, tench, etc.), while others are adapted to live with an amplitude of no more than 5-7 °. Typically, fish in the tropical and subtropical zones are more stenothermic than fish in temperate and high latitudes. Marine forms are also more stenothermal than freshwater ones.
While the overall temperature range at which a species of fish can live can often be very large, for each stage of development it usually turns out to be much smaller.
Fish react differently to fluctuations in temperature and depending on their biological state. So, for example, salmon caviar can develop at temperatures from 0 to 12°C, and adults easily tolerate fluctuations from negative temperatures to 18-20°C, and possibly even higher.
Common carp successfully endure winter at temperatures ranging from negative to 20 ° C and above, but it can only feed at temperatures not lower than 8-10 ° C, and, as a rule, breeds at temperatures not lower than 15 ° C.
Typically, fish are divided into stenothermic, i.e., adapted to a narrow amplitude of temperature fluctuations, and eurythermal - those. which can live within a significant temperature gradient.
Fish species are also associated with the optimal temperatures to which they are adapted. Fish of high latitudes have developed a type of metabolism that allows them to feed successfully at very low temperatures. But at the same time, in cold-water fish (burbot, taimen, whitefish), at high temperatures, activity sharply decreases and the intensity of feeding decreases. On the contrary, in fish of low latitudes, intensive metabolism occurs only at high temperatures;
Within the limits of optimal temperatures for a given type of fish, an increase in temperature usually leads to an increase in the intensity of food digestion. So, in the vobla, as can be seen from the graph (Fig. 27), the rate of digestion of food at
L
th
II"*J
about
zo zі
1-5" 5th 10-15" 15-20" 20-26"
Temperature
5§.
I
S"S-
Figure 27. Daily intake (dotted line) and rate of feed digestion (solid line) of roach Rutilus rutilus casplcus Jak. at different temperatures (according to Bokova, 1940)
15-20 ° C is three times more than at a temperature of 1-5 ° C. Due to the increase in the rate of digestion, the intensity of feed consumption also increases.
Rice. 28., Change in oxygen concentration lethal for carp with temperature change (from Ivlev, 1938)
Changes with temperature changes and the digestibility of feed. So, in roach at 16 ° C, the digestibility of dry matter is 73.9%, and at 22 ° C -
81.8%. Interestingly, at the same time, the digestibility of nitrogen compounds in roach remains almost unchanged within these temperatures (Karzinkin, J952); in carp, i.e., in fish that are more animal-eating than roach, with an increase in temperature, the digestibility of feed increases both in general and in relation to nitrogen compounds.
Naturally, є temperature change is very
the gas exchange of fish also changes greatly. At the same time, the minimum concentration of oxygen at which the fish can live often also changes. So for carp, at a temperature of 1 ° C, the minimum oxygen concentration is 0.8 mg / l, and at 30 ° C - already 1.3 mg / l (Fig. 28). Naturally, the quantity
65
5th century NIKOLSKY
kisyofbda, consumed by fish at different temperatures, is also connected with the state of the fish itself. " Г lt; "1 .
A change in temperature,: influencing .; on „: a change in the intensity of fish metabolism, is also associated with a change in the toxic effects of various substances on its body. Thus, at 1°C the lethal CO2 concentration for carp is 120 mg/l, and at 30°C this amount drops to 55-60 mg/l (Fig. 29).
504*
Rice. 29. Changes in the concentration of carbon dioxide lethal for carp due to changes in temperature (from Ivlev, 1938)
With a significant drop in temperature, fish can fall into a state close to suspended animation, and stay for a more or less long time in a supercooled state, even freezing into ice, such as crucian carp and black fish. ¦
Kai - experiments showed that when the body of a fish freezes into ice, its internal juices remain unfrozen and have a temperature of about - 0.2, - 0.3 ° C. Further cooling, provided that the fish is frozen in water, leads to a gradual decrease in temperature fish body, freezing of abdominal fluids and death. If a fish freezes out of water, then usually its freezing is associated with preliminary hypothermia and a drop in body temperature for a short time even to -4.8 °, after which freezing of body fluids occurs and a slight increase in temperature as a result of the release of latent heat of freezing. If the internal organs and gills freeze, then the death of the fish is inevitable.
The adaptation of fish to life at certain, often very narrow, temperature amplitudes is associated with the development in them of a rather subtle reaction to the temperature gradient.
. What is the minimum temperature gradient? react fish
; "Ch. (by Bull, 1936). :
Pholis gunnelus (L.) "J . . .... . . 0.03°
Zoarces viviparus (L.) . .. . . . , / .... . , 0.03°
Myoxocepfiqlus scorpius (L.) , . . . . . . . . . . . 0.05°
Gadus morhua L. . . . . :. . . . i¦. . . ..gt; . . . 0.05°
Odontogadus merlangus (L.) . ... . .4 . . . ... 0.03"
Pollachius virens (L.) 0.06°
Pleuronectes flesus L. . . . 0.05°.
Pteuroriectes platessa (L.) . Y , . . . . . . . . . . . 0.06°
Spinachia spinachia (L!) 0.05°
Nerophis lumbriciformes Penn. , . . . . . . . . . , 0.07°
Since fish are adapted to life under a certain
Tridenal temperature in
Rice. ZO. Distribution:
1 - Ulcina olriki (Lutken) (Agonidae); 2 - Eumesogrammus praecisus (Kroyer) (Stichaeidae) in connection with the distribution of near-bottom temperatures (from Andriyashev, 1939)
temperature, it is natural that its distribution in a reservoir is usually associated with the temperature distribution. With changes in temperature, both seasonal and long-term, are associated with changes in the distribution of fish.
"The confinement of individual fish species to certain temperatures can be clearly judged by the given curve of the frequency of occurrence of individual fish species in connection with the temperature distribution (Fig. 30). As an example, we have taken representatives of the family -
Agonidae - Ulcina olriki (Lfltken) and Stichaeidae -
Eumesogrammus praecisus (Kroyer). As can be seen from fig. 30, both of these species are confined in their distribution to quite specific different temperatures: Ulcina occurs at a maximum at a temperature of -1.0-1.5 ° C, a * Eumesogrammus - at +1, = 2 ° C.
, Knowing the confinement of fish to a certain temperature, it is often possible, when searching for their commercial concentrations, to be guided by the temperature distribution in the reservoir, f Long-term changes in water temperature (as, for example, in the North Atlantic due to the Hansen and Nansen, 1909), During the years of warming in the White Sea, there were cases of catching such relatively warm-water fish as mackerel - Scomber scombrus L., and in Kanin's nose - garfish * - Belone belone (L.). Cod penetrates into the Kara Sea during periods of melting, and its commercial concentrations appear even off the coast of Greenland. .
On the contrary, during periods of cooling, arctic species descend to lower latitudes. For example, the polar cod Boreogadus saida (Lepechin) enters the White Sea in large numbers.
Sudden changes in water temperature sometimes cause mass death of fish. An example of this kind is the case of the chameleonhead-¦ Lopholatilas chamaeleonticeps Goode et Bean (Fig. 31). Until 1879, this species was not known off the southern coast of New England.
In subsequent years, due to warming, it appeared
Rice. 31. Lopholatilus hamaeleonticeps Goode et Bean (chameleonheads)
here in large numbers and became an object of fishing. As a result of a sharp cold snap that occurred in March 1882, a lot of individuals of this species died. They covered the surface of the sea with their corpses for miles. After this incident, for a long time, the chameleon head completely disappeared from the indicated area and only in recent years has reappeared in a fairly significant number. .
The death of cold-water fish - trout, white salmon - can be caused by an increase in temperature, but usually temperature does not affect death directly, but through a change in the oxygen regime, violating breathing conditions.
Changes in the distribution of fish due to changes in temperature also took place in previous geological epochs. It has been established, for example, that in the reservoirs located on the site of the basin of the modern Irtysh, in the Miocene there were fish that were much warmer than those that inhabit the Ob basin now. Thus, the Neogene Irtysh fauna included representatives of the genera Chondrostoma, Alburnoides, and Blicca, which are now not found in the Arctic Ocean basin in Siberia, but are distributed mainly in the Ponto-Aralo-Caepian province and, apparently, were. forced out of the Arctic Ocean basin as a result of climate change towards cooling (V. Lebedev, 1959). “. %
And at a later time, we find examples of changes in the distribution area and number of species under the influence of
changes in ambient temperature. Thus, the cooling caused by the onset of glaciers at the end of the Tertiary and the beginning of the Quaternary led to the fact that representatives of the salmon family, confined to cold waters, were able to significantly move south to the Mediterranean basin, including the rivers of Asia Minor and North Africa. At that time, salmon were much more abundant in the Black Sea, as evidenced by the large number of bones of this fish in the food remains of Paleolithic man.
In the post-glacial period, climate fluctuations also led to changes in the composition of the ichthyofauna. So, for example, during the climatic optimum about 5,000 years ago, when the climate was somewhat warmer, the fish fauna of the White Sea basin contained up to 40% of more warm-water species such as asp - Aspius aspius (L.), rudd - Scardinius eryth- rophthalmus (L.) and blue bream - Abramis ballerus (L.) Now these species are not found in the White Sea basin; they were undoubtedly forced out of here by the cooling that occurred even before the beginning of our era (Nikolsky, 1943).
Thus, the relationship between the distribution of individual species and temperature is very large. The attachment of representatives of each faunal complex to certain thermal conditions causes the frequent coincidence of boundaries between individual zoogeographic regions in the sea and certain isotherms. For example, the Chukotka temperate arctic province is characterized by very low temperatures and, accordingly, the predominance of the Arctic fauna. Most of the boreal elements penetrate only into the eastern part of the Chukchi Sea along with warm currents. The fauna of the White Sea, identified as a special zoogeographical area, is much more cold-water in its composition than the fauna of the southern part of the Barents Sea located to the north of it.
The nature of distribution, migrations, spawning and feeding areas of the same species in different parts of its distribution area may be different due to the distribution of temperature and other environmental factors. For example, the Pacific cod Gadus morhua macrocephalus Til. - off the coast of the Korean Peninsula, breeding sites are located in the coastal zone, and in the Bering Sea at depths; feeding areas are the opposite (Fig. 32).
The adaptive changes that take place in fish with changes in temperature are also associated with some morphological rearrangement. So, for example, in many fishes, the adaptive response to changes in temperature, and thus the density of water, is a change in the number of vertebrae in the caudal region (with closed hemal arches), i.e., a change in hydrodynamic properties due to adaptation to movement in water of a different density.
Similar adaptations are also observed in fish developing at different salinities, which is also associated with a change in density. At the same time, it should be noted that the number of vertebrae changes with changes in temperature (or salinity) during the segment
February
200
№
Depth 6 m Bering burrow
Western
Kamchatka
Tatar proliy ~1
Southern part of the 3“ Japanese muzzle,
b "°
Dgust 100 200
Southern part of the Sea of Japan
Rice. 32. Distribution of Pacific cod Gadus morhua macrocephalus Til. in various parts of its area of distribution in connection with the distribution of temperature; oblique shading - breeding sites (from Moiseev, 1960)
W
Depth 6 m
beringovo
sea
Western
Kamchatka
Tatar
prolius
body movements. If this kind of influence takes place at later stages of development, then there is no change in the number of metameres (Hubbs, 1922; Taning, 1944). A similar phenomenon was observed for a number of fish species (salmon, cyprinids, etc.). A similar kind of change in some species of fish takes place.
and in the number of rays in unpaired fins, which is also associated with adaptation to movement in water of various densities.
Special attention should be paid to the significance of ice in the life of fish. The forms of influence of ice on fish are very diverse] This is a direct effect of temperature, since when Water freezes, the temperature rises, and when ice melts, it decreases. But other forms of ice influence are much more important for fish. Especially great is the importance of the ice cover as an insulator of water in the atmosphere. During freeze-up, the influence of winds on water almost completely stops, the supply of oxygen from the air, etc., slows down greatly (see below). By isolating water from air, ice also makes it difficult for light to penetrate into it. Finally, ice sometimes has on fish and mechanical impact: There are cases when, in the coastal zone, fish and caviar kept near the coast were crushed by ice. Ice also plays a certain role in changing the chemical composition of water and salinity: water, and during massive ice formation, not only the salinity of the water changes, while increasing, but also the ratio of salts. The melting of ice, on the contrary, causes a decrease in salinity and a change in the salt composition of the opposite nature. "then.-/that'
Fish - inhabitants of the aquatic environment
Fish live in water, water has a significant density and it is more difficult to move in it than in air.
What kind of fish should be in order to survive in the aquatic environment?
Fish are characterized by:
- Buoyancy
- streamlining
- Slip
- Infection protection
- Orientation in the environment
Buoyancy
- Spindle-shaped body
- The body is laterally compressed, streamlined
- Fins
Streamline and glide:
Tiled scales
germicidal mucus
Fish movement speed
The fastest fish sailfish.She swims faster than a cheetah runs.
The speed of a sailboat fish is 109 km / h (for a cheetah - 100 km / h)
Merlin - 92 km / h
Fish - wahoo - 77.6 km / h
Trout - 32 km / h faster than pike.
Madder - 19 km/h faster
Pike - 21 km/h
Karas - 13 km / h
And did you know that…
The silvery-white color of fish and the luster of scales largely depend on the presence of guanine in the skin (an amino acid, a breakdown product of proteins). The color changes depending on the living conditions, age, and health of the fish.
Most fish have a silvery color and at the same time the abdomen is light and the back is dark. Why?
Protection from predators - dark back and light abdomen
Sense organs of fish
Vision
The eyes of fish can only see at close range due to the spherical lens close to the flat cornea, which is an adaptation for vision in the aquatic environment. Usually the eyes of the fish are “set” for vision at 1 m, but due to the contraction of smooth muscle fibers, the lens can be pulled back, which achieves visibility at a distance of up to 10-12 m.
2) German ichthyologists (scientists who study fish) have found that fish distinguish colors well, incl. and red.
Flounder bypasses red, light green, blue and yellow nets. But the fish probably does not see gray, dark green and blue nets.
Smell and taste
1) The taste organs of fish are located in the mouth, on the lips, on the scalp, body, on the antennae and on the fins. They determine, first of all, the taste of water.
2) The organs of smell are paired sacs in the front of the skull. Outward they open with nostrils. The sense of smell in fish is 3-5 times finer than in dogs.
The presence of vital substances of fish can be established at a distance of 20 km. Salmon catches the smell of the native river from a distance of 800 km from its mouth
Lateral line
1) A special organ runs along the sides of the fish - the lateral line. It serves as an organ of balance and for orientation in space.
Hearing
Scientist Karl Frisch studied not only vision, but also the hearing of fish. He noticed that his blind fish for experiments always surfaced when they heard the whistle. Pisces hear very well. Their ear is called the inner ear and is located inside the skull.
Norwegian scientists have found that some species of fish are able to distinguish sound vibrations from 16 to 0.1 Hz. This is 1000 times greater than the sensitivity of the human ear. It is this ability that helps the fish to navigate well in muddy water and at great depths.
Many fish make sounds.
Sciens purr, grunt, squeak. When a flock of sciens swims at a depth of 10-12m, lowing is heard
Marine midshipman - hisses and croaks
Tropical flounders make the sounds of a harp, bell ringing
Talk like fish
Dark carp - Khryap-khryap
Light croaker - try-try-try
Guinea cock - track-track-track or ao-ao-xrr-xrr-ao-ao-hrr-hrr
River catfish - oink-oink-oink
Sea carp - quack-quack-quack
Sprats - u-u-u-u-u-u
Cod - chirp-chirp-chirp (quietly)
Herring - whisper softly (tsh - tsh-tsh)
In the cold and dark depths of the oceans, the water pressure is so great that no land animal could withstand it. Despite this, there are creatures that have been able to adapt to such conditions.
In the sea you can find a variety of biotopes. In marine depths In the tropical zone, the water temperature reaches 1.5-5 ° C, in the polar regions it can drop below zero.
A wide variety of life forms are represented below the surface at a depth where sunlight is still able to receive, provides the possibility of photosynthesis, and, therefore, gives life to plants, which in the sea are the initial element of the trophic chain.
Incomparably more animals live in tropical seas than in Arctic waters. The deeper, the species diversity becomes poorer, there is less light, the water is colder, and the pressure is higher. At a depth of two hundred to a thousand meters, about 1000 species of fish live, and at a depth of one thousand to four thousand meters - only one hundred and fifty species.
The belt of waters with a depth of three hundred to a thousand meters, where twilight reigns, is called the mesopelagial. At a depth of more than a thousand meters, darkness is already setting in, the excitement of the water here is very weak, and the pressure reaches 1 ton 265 kilograms per square centimeter. Deep-sea shrimp of the genus Myobiotis, cuttlefish, sharks and other fish, as well as numerous invertebrates, live at such depths.
OR DO YOU KNOW THAT...
The dive record belongs to the cartilaginous fish basogigasu, which was spotted at a depth of 7965 meters.
Most invertebrates living at great depths are black in color, and most deep-sea fish are brown or black. Thanks to this protective coloration, they absorb the bluish - green light of deep waters.
Many deep-sea fish have an air-filled swim bladder. And until now, researchers do not understand how these animals withstand the enormous pressure of water.
Males of some species of deep-sea anglerfish attach by mouth to the abdomen of larger females and adhere to them. As a result, the man remains attached to the female for life, feeds at her expense, they even have a common circulatory system. And the female, thanks to this, does not have to look for a male during the spawning period.
One eye of a deep-sea squid that lives near the British Isles is much larger than the second. With the help of a large eye, he navigates the depth, and he uses the second eye when he rises to the surface.
Eternal twilight reigns in the depths of the sea, but numerous inhabitants of these biotopes glow in different colors in the water. The glow helps them attract a partner, prey, and also scare off enemies. The glow of living organisms is called bioluminescence.
BIOLUMINESCIENCE
Many species of animals that inhabit the dark sea depths can emit their own light. This phenomenon is called the visible glow of living organisms, or bioluminescence. It is caused by the enzyme luciferase, which catalyzes the oxidation of substances produced by the light-luciferin reaction. This so-called "cold light" can be created by animals in two ways. Substances necessary for bioluminescence, located in their body or in the body of luminous bacteria. In the European anglerfish, light-emitting bacteria contained in vesicles at the end of the dorsal fin grow in front of the mouth. Bacteria need oxygen to glow. When the fish does not intend to emit light, it closes off the blood vessels that lead to the place in the body where the bacteria reside. Spotted scalpelus fish (Pryobuchiernatm paireimus) carries billions of bacteria in special pouches under its eyes; with the help of special leather folds, the fish completely or partially closes these pouches by regulating the intensity of the emitted light. To enhance the glow, many crustaceans, fish and squids have special lenses or a layer of cells that reflect light. The inhabitants of the deep use bioluminescence in different ways. Deep sea fish glow in different colors. For example, the photophores of a ribs-birch radiate greenish, and the photophores of an astronest emit a violet-blue color.
SEARCHING FOR A PARTNER
The inhabitants of the deep sea resort to various ways to attract a partner in the dark. Light, smell and sound play an important role in this. In order not to lose the female, males even use special tricks. The relationship between males and females of the Woodlanders is interesting. The life of the European anglerfish is better studied. Males of this species usually find a large female without any problems. With their large eyes, they notice her typical light signals. Having found a female, the male firmly attaches to her and grows to her body. From that time on, he leads an attached lifestyle, even feeding through the female's circulatory system. When a female anglerfish lays her eggs, the male is always ready to fertilize her. Males of other deep-sea fishes, for example, gonostomas, are also smaller than females, some of them have a well-developed sense of smell. Researchers believe that in this case, the female leaves behind an odorous trail that the male finds. Sometimes males of the European anglerfish are also found by smell of females. In water, sounds travel a long distance. That is why the males of the three-headed and toad-like ones move their fins in a special way and make a sound that should attract the attention of the female. Toad fish give out horns, which are transmitted as "boop".
At such a depth there is no light, and plants do not grow here. Animals that live in the depths of the sea can only hunt the same deep-sea inhabitants or eat carrion and decaying organic remains. Many of them, such as holothurians, starfish, and bivalves, feed on microorganisms that they filter out of the water. Cuttlefish usually prey on crustaceans.
Many species of deep-sea fish eat each other or hunt small prey for themselves. Fish that feed on molluscs and crustaceans must have strong teeth to crush the shells that protect the soft bodies of their prey. Many fish have a bait located directly in front of the mouth that glows and attracts prey. By the way, if you are interested in an online store for animals. contact.
Deep sea fish are considered one of the most amazing creatures on the planet. Their uniqueness is explained primarily by the harsh conditions of existence. That is why the depths of the world's oceans, and especially deep-sea depressions and trenches, are not at all densely populated.
and their adaptation to the conditions of existence
As already mentioned, the depths of the oceans are not as densely populated as, say, the upper layers of the water. And there are reasons for this. The fact is that the conditions of existence change with depth, which means that organisms must have some adaptations.
- Life in the dark. With depth, the amount of light decreases sharply. It is believed that the maximum distance that a sunbeam travels in water is 1000 meters. Below this level, no traces of light were found. Therefore, deep-sea fish are adapted to life in total darkness. Some fish species do not have functioning eyes at all. The eyes of other representatives, on the contrary, are very strongly developed, which makes it possible to capture even the weakest light waves. Another interesting device is luminescent organs that can glow using the energy of chemical reactions. Such light not only facilitates movement, but also lures potential prey.
- High pressure. Another feature of the deep-sea existence. That is why the internal pressure of such fish is much higher than that of their shallow relatives.
- Low temperature. With depth, the temperature of the water decreases significantly, so the fish are adapted to life in such an environment.
- Lack of food. Since the diversity of species and the number of organisms decreases with depth, there is, accordingly, very little food left. Therefore, deep-sea fish have supersensitive organs of hearing and touch. This gives them the ability to detect potential prey at a great distance, which in some cases is measured in kilometers. By the way, such a device makes it possible to quickly hide from a larger predator.
You can see that the fish living in the depths of the ocean are truly unique organisms. In fact, a huge area of the world's oceans is still unexplored. That is why the exact number of deep-sea fish species is unknown.
Diversity of fish living in the water depths
Although modern scientists know only a small part of the population of the depths, there is information about some very exotic inhabitants of the ocean.
Bathysaurus- the deepest predatory fish that live at a depth of 600 to 3500 m. They live in tropical and subtropical water spaces. This fish has almost transparent skin, large, well-developed sensory organs, and its oral cavity is littered with sharp teeth (even the tissues of the palate and tongue). Representatives of this species are hermaphrodites.
viper fish- Another unique representative of the underwater depths. It lives at a depth of 2800 meters. It is these species that inhabit the depths. The main feature of the animal is its huge fangs, which are somewhat reminiscent of the poisonous teeth of snakes. This species is adapted to existence without constant food - the stomachs of fish are so stretched that they can swallow whole a living creature much larger than themselves. And on the tail of the fish there is a specific luminous organ, with the help of which they lure prey.
Angler- a rather unpleasant-looking creature with huge jaws, a small body and poorly developed muscles. It lives on Since this fish cannot actively hunt, it has developed special adaptations. has a special luminous organ that releases certain chemicals. Potential prey reacts to light, swims up, after which the predator swallows it completely.
In fact, there are much more depths, but not much is known about their way of life. The fact is that most of them can exist only under certain conditions, in particular, at high pressure. Therefore, it is not possible to extract and study them - when they rise to the upper layers of the water, they simply die.