Evolution of higher nervous activity in vertebrates. Fish being tested Do fish feel pain?
STUDYING THE BEHAVIOR AND ADAPTATION OF FISH TO EXTERNAL CONDITIONS
The study of fish behavior is one of the most important tasks of ichthyology and an immense field for conducting the most interesting and exciting experiments and research. In particular, the conservation of stocks of valuable anadromous and semi-anadromous fish in connection with hydraulic construction is impossible without a successful study of the behavior of these fish in spawning grounds, in the area of dams and fish passages. Equally important is the prevention of fish being sucked into water intakes. For this purpose, devices such as bubble curtains, electric fish barriers, mechanical gratings, etc. are already used or have been tested, but so far the devices used are not sufficiently effective and economical.
For the successful development of the fishery and the improvement of fishing gear, information on the behavior of fish in the fishing zone, dependence on the hydrometeorological situation and hydrological factors, and on daily and periodic vertical and horizontal migrations is extremely important. At the same time, a rational organization of fishing is not possible without studying the distribution and behavior of groups of different ages. The timing and power of migrations, the approaches of fish to spawning, feeding, and wintering places are largely determined by changes in environmental conditions and the physiological state of individuals.
The importance of the sense organs in the perception of abiotic and biotic signals
The study of fish behavior is carried out on the basis of regular natural observations, experiments in laboratory conditions and analysis of data on the interaction with the external environment of the higher nervous activity of the studied objects. In the process of interacting with the environment, fish show three ways of orientation:
Direction finding - reproduction of a signal coming from the outside world;
Location - sending signals and receiving their reflections;
Signaling is the sending of a signal by some individuals and their perception by others.
The perception of abiotic and biotic signals that affect the behavior of fish occurs through the sense organs, among which are primarily vision, hearing, lateral line, and smell. The reflex activity of fish is of particular importance.
Fish vision
Compared to the air environment, water, as a habitat for fish, is less favorable for visual perception. The illumination of the water layers by the sun's rays penetrating the water is directly dependent on the amount of dissolved and suspended particles, which cause the turbidity of the water and determine the boundaries of the action of the organs of vision of fish. In sea water, illumination reaches a depth of 200-300 m, and in fresh water only 3-10 m. The deeper the light penetrates into the water, the deeper the plants penetrate. The transparency of water is extremely different. It is greater away from the coast and decreases in the inland seas. The more living organisms in the water, the less transparent the water. The very clear waters of the seas, especially the beautiful rich blue color, are waters that are scarce in life. The most transparent seas are the Sargasso and the Mediterranean.
Fish have color vision. For individuals living in the illuminated zone, it is of great importance and determines their behavior. The nutrition of plankton feeders, including juvenile fish, is carried out thanks to well-developed organs of vision. The visual acuity inherent in fish allows, depending on the illumination and transparency of the water, to distinguish objects at a distance of up to several tens of meters. All of the above is of great importance for the nutritional and defensive reactions of fish. It has been proven that the formation and disintegration of flocks are also associated with the illumination of the aquatic environment.
The movement of fish against the current is controlled by the organs of vision, less often by the organs of smell. This is the basis for attempts to send fish in fish passages after the mock-ups. With Illumination is associated with rhythms and nutritional activity.
The phenomenon of vertical zonality and the predominant color of animals and plants is due to the uneven penetration of rays of different wavelengths into the water column. Animals are very often colored in the color of that part of the spectrum that penetrates to a given depth, as a result of which it acquires a protective color, they seem invisible. In the upper horizons, the animals are mostly painted in brownish-greenish colors, and deeper - in red. At great depths, deprived of light, the animals are mostly colored black or completely devoid of color (depigmented).
Hearing.
The acoustic properties of water are much stronger than those of air. Sound vibrations travel faster and penetrate farther. It has been established that the role of sound signaling increases with the onset of twilight, as visual perception decreases. The center of sound perception is the inner ear of fish. The perception of ultrasonic vibrations is not characteristic of fish, but they react to low-frequency sounds. The reaction to ultrasound is detected only under the action of a powerful source at a short distance and can rather be attributed to the pain sensation of the skin.
When there is a reaction to sound signals, the fish react in a directed (reflexive) manner, primarily to food stimuli or a danger signal. In the city, fish quickly get used to noises, even constant very loud sounds. Perhaps that is why, with the help of sound signals, it was not possible to organize the directed movement of salmon into the rivers or scare them away from sewage. Even near the airfields, the fish do not change their behavior and continue to peck at the bait. It is noted that intermittent sound affects fish more strongly than constant sound.
Lateral line
First of all, it should be noted the functional connection of the lateral line with the organs of hearing. It has been established that the lower part of sound vibrations (frequencies 1-25 Hz) are perceived by the lateral line. The meaning of the lateral line has not been fully studied. The main function of the lateral line is the perception of hydrodynamic fields and water jets. Hydrodynamic fields from large sources, which cause a defensive reaction in fish, are usually perceived at a considerable distance. However, in areas where fast currents are formed in the rivers below the dam, many fish quickly get used to the changed conditions.
The hydrodynamic fields caused by the movement of small bodies usually cause a feeding reaction in fish. With the help of the lateral line, fish are precisely oriented for an aimed throw over a relatively short distance of several tens of centimeters.
With the help of the lateral line, twilight, nocturnal, and overgrown predators navigate when reaching their prey. In juvenile fish and plankton feeders, the lateral line serves to detect predators and general orientation in the environment.
Smell of fish
Consideration should be given to the property of water as a good solvent. It has been established that fish react to negligible amounts of substances dissolved in water. Fishermen use scent to attract fish. At the same time, other substances, such as tincture of the skin of predatory fish and marine mammals, have a deterrent effect.
The perception of substances dissolved in water, apparently, is associated with the organs of taste. Anadromous fish find their way from the sea to the rivers with the help of their sense of smell. There is no doubt that fish are capable of memorization. This explains homing(from the English home - "house") - the ability of fish to enter exactly those rivers, channels or girls, from which they emerged as fry after development from caviar.
Higher nervous activity and behavior of fish
The ability of fish to acquire conditioned reflexes in combination with unconditioned reflexes makes it possible to control their behavior. Conditioned reflexes are developed in fish more slowly than in higher vertebrates, and quickly fade away if they are not reinforced by the same factors that contributed to their formation, but are capable of spontaneously arising after a certain time.
Water temperature plays a special role in the creation and extinction of reflexes. There is evidence (Yudkin, 1970) that conditioned reflexes in sturgeons are developed much worse in autumn than in summer. In goldfish, a decrease in water temperature below +13 °C and an increase above +30 °C caused the disappearance of all previously acquired reflexes. All this becomes quite understandable if we consider that the vital activity of fish, animals with a low blood temperature, depends on the temperature of the water.
Conditioned reflexes can occur in fish in the form of imitation. Untrained fish imitate others whose conditioned reflexes were formed after appropriate training or the acquisition of life experience. Quite indicative in this respect is the change in the behavior of fish in the zone of fishing with active and even stationary fishing gear. Often, one individual is enough to find a loophole to exit the fishing gear for most of the flock to leave it (for example, anchovy in fixed and cast nets).
Pilengas is able to overcome net formations, waddle over the upper line, jump out and even crawl, wriggling along an inclined canvas when hauling out seines.
Pilot-observers, who for a long time were engaged in aiming fishing vessels at shoals of fish, noted a gradual change in the behavior of the anchovy: a change in the direction of movement and exit from purse seines, “crouching”, scattering, etc.
The behavior and speed of reactions of fish in different physiological states are not identical. Fatty fish form aggregations faster, which are more stubborn than those formed by physiologically weakened individuals. Often, fish react not only to sudden changes in conditions, but also to emerging trends in environmental factors. With a slight increase in water temperature, the accumulations can simply disintegrate, despite the fact that the temperature will remain within the optimal range for fishing.
The formation of fish in schools is of great importance. The defensive value of a flock of fish is as great as that of birds. Also, covering a larger area of water, the flock finds feeding places faster than individual individuals.
Observations have shown the presence of vertical migrations in some fish species. So, on the Newfoundland bank, sea bass rises from depths of 500-600 m to depths of 300-400 m at sunset for 60-90 minutes. Cod and haddock behave in a similar way. In the Black Sea, vertical migrations are most characteristic of anchovy and horse mackerel, which descend to the lower horizons during the day and rise to the surface at night. Their behavior is associated with the movement of plankton. For many fish, being at different depths and at different distances from the coast is typical at different periods of the life cycle.
All of the above is directly related to the behavior of fish. This must be taken into account by the researcher in order to more effectively influence the behavior of fish in the fishing areas, where it is necessary to identify the leading factors for each specific case. At present, knowledge of the behavioral features is of particular importance for the successful development of the fishery. And this is due, first of all, to an increase in the intensity of fishing, a drop in stocks and an increase in the economic cost of work.
The study of behavioral features depending on environmental factors and the physiological state of fish allows researchers and fishers to tactically regulate fishing with an increase in its efficiency. Knowledge of the biology of the fishery object makes it possible to organize fishing during periods of maximum concentrations, at the depths of the greatest distribution and at water temperatures, when the accumulations are most stable. One of the tools for such studies is a multivariate correlation analysis of the most significant relationships between oceanological and biological criteria for the construction of mathematical models that describe the phenomena and processes of the life cycle of fish. For a long time and well in a number of basins, forecasts of the timing of autumn migrations, the formation and disintegration of wintering aggregations, and the start of fishing for mass commercial fish have proven themselves. This helps to reduce unproductive downtime of vessels and increase the level of intensity of fishing.
As examples of such models, one can cite the regression equations calculated at AzNIIRH for predicting the timing of the autumn migration of the Azov anchovy through the Kerch Strait to the Black Sea.
Start of move:
Y \u003d 70.41 +0.127 X 1, -0.229 X 2,
Y \u003d 27.68-0.18 X 2 - 0.009 (H).
Start of mass migration:
Y, \u003d 36.01 +0.648 X 3 -0.159 X 2,
where Y and Y 1 are the dates of the expected start of autumn migration and mass movement (counting from September 1); X 1 and Xz - the dates of the final transition of the water temperature through +16 and +14 ° С (respectively) in the southern part of the Sea of Azov (counting from September 1); X 2 - the number of fish (in%) in the population with a fatness coefficient of 0.9 or more as of September 1, H - the duration of feeding (degree / days) after spawning on September 1.
The error in forecasting the timing of the start of migrations according to the presented models does not exceed 2-3 days.
behavioral acts that promote passive and active migration. All fish are characterized by a food-procuring instinct, although it can be expressed in very different forms of behavior. The possessive instinct, expressed in the protection of territory and shelters, upholding the sole right to a sexual partner, is far from known for all species, sexual - for all, but its expression is very different.
Complexes of simple behavioral acts that have a certain sequence and purposefulness are sometimes called dynamic stereotypes - for example, a certain series of actions when obtaining a discrete portion of food, going to a shelter, building a nest, caring for protected eggs. The dynamic stereotype also combines congenital and acquired forms of behavior.
Acquired forms of behavior are the result of an organism's adaptation to changing environmental conditions. They allow you to acquire cost-effective, time-saving standard reactions. In addition, they are labile, that is, they can be redone or lost as unnecessary.
Different pisciformes have different complexity and development of the nervous system, so the mechanisms for the formation of acquired forms of behavior are different for them. For example, acquired responses in lampreys, although they are formed with 3-10 combinations of conditioned and unconditioned stimuli, are not developed during the time interval between them. That is, they are based on persistent sensitization of receptor and nerve formations, and not on the formation of connections between the centers of conditioned and unconditioned stimuli.
The training of laminabranchs and teleosts is based on true conditioned reflexes. The rate of development of simple conditioned reflexes in fish is approximately the same as in other vertebrates - from 3 to 30 combinations. But not every reflex can be worked out. Food and defensive motor reflexes are the most well studied. Defensive reflexes in laboratory conditions are studied, as a rule, in shuttle chambers - rectangular aquariums with an incomplete partition that allows one to move from one half of the chamber to the other. As a conditioned stimulus, an electric light bulb or a sound source of a certain frequency is most often used. As an unconditioned stimulus, an electric current from a network or battery with a voltage of 1-30 volts, supplied through flat electrodes, is usually used. The current is turned off as soon as the fish moves to another compartment, and if the fish does not leave, then after a certain time - for example, after 30 seconds. The number of combinations is determined when the fish performs the task in 50 and 100% of cases with a sufficiently large number of experiments. Food reflexes are usually developed for any action of the fish by rewarding the issuance of a portion of food. The conditioned stimulus is a light being turned on, a sound being emitted, an image appearing, etc. In this case, the fish should come to the feeder, press the lever, pull the bead, etc.
It is easier to develop an "environmentally adequate" reflex than to force the fish to do something that is not characteristic of it. For example, it is easier to make an eared perch, in response to a conditioned stimulus, grab a tube from which feed paste is squeezed out of its mouth than to throw a float from below. It is easy to develop in a loach the reaction of leaving to another compartment, but it is not possible to make it move while a conditioned and even unconditioned stimulus is acting - such a movement is not characteristic of this species, which is characterized by hiding after a jerk. Persistent attempts to make the loach constantly move along the annular channel lead to the fact that it stops moving and only flinches from electric shocks.
It should be said that the "abilities" of the fish are very different. What works with some instances doesn't work with others. A. Zhuikov, studying the development of defensive reflexes in juvenile salmon grown at a fish hatchery, divided the fish into four groups. In some fish, it was not possible at all to develop a motor defensive reflex in 150 experiments, in another part the reflex was developed very quickly, the third and fourth groups of experimental fish acquired the skill of accurately avoiding electric shock with an intermediate number of lamp ignitions. Studies have shown that fish that learn easily are significantly better at avoiding predators, while those that learn poorly are doomed. After the release of salmon from the hatchery, after a period of time sufficient to undergo rigorous selection when living together with predators (fish and birds), the learning ability of the survivors is much higher than that of the original material, since the "incapable" become the food of predators.
The simplest form of learning is habituation to an indifferent stimulus. If at the first demonstration of a frightening stimulus, for example, a blow to the water, the wall of an aquarium, a defensive reaction arises, then with repeated repetition, the reaction to it gradually weakens and, finally, completely stops. Fish become accustomed to a variety of stimuli. They get used to living in conditions of industrial noise, periodic drawdown of the water level, eye contact with a predator, fenced off by glass. In the same way, the developed conditioned reflex can be inhibited. With repeated presentation of a conditioned stimulus without reinforcement by an unconditioned stimulus, the conditioned reflex disappears, but after some time the "deception" is forgotten, and the reflex may spontaneously arise again.
During the development of conditioned reflexes in fish, the phenomena of summation and differentiation may occur. Numerous experiments are an example of summation, when a reflex developed to one sound frequency or to one color of a light source manifested itself upon presentation of other sound frequencies or colors. Differentiation occurs in the presence of the resolving power of the receptor organs in fish: if food reinforcement is given at one frequency and pain at another, then differentiation occurs. The fish manage to develop reflexes of the second order, that is, reinforcement is given after the light source is turned on only if it is preceded by a sound stimulus. The reaction in this case is observed directly to the sound without waiting for the light. In the development of chain reflexes, fish are inferior to higher animals. For example, in children, reflexes up to the sixth order can be observed.
CONDITIONAL REFLECTOR ACTIVITY OF FISH
In the process of evolution, animals have developed a special mechanism that makes it possible to respond not only to conditioned stimuli, but also to a mass of indifferent (indifferent) stimuli. Coinciding in time with unconditioned stimuli. Thanks to this mechanism, the appearance of indifferent stimuli signals the approach of those agents that are of biological significance. The connection of the animal with the outside world is expanding. The animal gets the opportunity to better adapt to the conditions of the external environment. Therefore, conditioned reflexes are necessary for life.
IP Pavlov pointed out that during the formation of a conditioned reflex in the cerebral cortex, the nervous connection between the excited centers of the conditioned and unconditioned stimulus is closed.
The cortex of the cerebral hemispheres of higher vertebrates (neopalhum), which is formed in the process of phylogeny from the forebrain and is of exceptional importance for the formation of conditioned connections, is still absent in fish. It has been proven that the middle and diencephalon play an important role in the formation of conditioned reflexes. In this regard, the ability of fish to engage in conditioned reflex activity has been established by numerous studies by various authors. goby, cod, etc.) are able to develop conditioned reflexes (or, in the terminology of German authors, "train") to a wide variety of stimuli.
At the same time, it should be noted that only in the works of Frolov was a deep analysis of the specific features of the conditioned reflex activity of fish, based on the laws discovered by IP Pavlov, given;
In the Black Sea, as, probably, in other warm seas, there is an amazing way of amateur fishing "for tyrant". A fisherman, accustomed to cautious and capricious freshwater fish, is taken aback when he first gets on sea fishing. The tackle, in other words, the “tyrant” itself, is a long fishing line, to one end of which four or five hooks are attached to short leashes. Nothing else is required - no rod, no bait. The fisherman goes to a deep place, lowers the hooks into the water, and winds the other end of the fishing line around his finger. He sits in the boat and from time to time tugs at the line until he feels that it is getting heavier. Then drags. And what do you think, pulls out a fish, and sometimes not one, but two or three at once. True, a fish, as a rule, does not take empty hooks in its mouth, but hooks on them with its belly, gills, even tail. And still it seems that you need to be completely stupid to fall for such a frankly dangerous tackle, and even not promising any benefits.
Maybe, indeed, fish are very stupid creatures. Let's try to figure it out. The main criterion of the mind is the ability to learn. Pisces are diligent students. They easily develop different skills. Everyone can verify this for himself. At home, many keep tropical fish. In two or three days, it is easy to teach the inhabitants of the aquarium to swim up to the glass, if you first tap it lightly with your finger, and then throw some tasty food there. After fifteen or twenty such procedures, the fish, having heard the call, will drop all their fish business and rush to the appointed place, hoping to get a portion of worms for diligence.
The skills acquired by bees, ants and fish are not similar to those developed in quite primitive animals. In their complexity, in the duration of their retention, they rarely differ from habituation reactions and from summation reflexes. The high perfection of the nervous system of these animals allowed them to develop adaptive reactions of a new type. They are called conditioned reflexes.
This type of reflexes was discovered and studied by I.P. Pavlov on dogs. The name is not given by chance. The formation, preservation or elimination of these reflexes occurs only under special conditions.
For the emergence of conditioned reflexes, it is necessary that the action of two specific stimuli coincide several times in time. One of them - it is necessary that he act first - should not be of any particular importance to the animal, neither to frighten him, nor to cause him a food reaction. Otherwise, it is absolutely indifferent what kind of irritant it will be. It may be some sound, the sight of any object or other visual stimulus, any smell, heat or cold, touching the skin, and so on.
The second stimulus, on the contrary, should cause some kind of innate reaction, some kind of unconditioned reflex. This may be a food or defensive reaction. After several combinations of such stimuli, the first of them, previously a completely indifferent stimulus for the animal, begins to evoke the same reaction as the unconditioned one. It was in this way that I developed a food conditioned reflex in the inhabitants of my aquarium. The first stimulus, tapping on glass, was at first absolutely indifferent to the fish. But after it coincided fifteen to twenty times with the action of a food irritant - ordinary fish food - the tapping acquired the ability to cause a food reaction, forcing the fish to rush to the feeding place. Such a stimulus is called a conditioned stimulus.
Even in ants and fish, conditioned reflexes persist for a very long time, and in higher animals - almost all their lives. And if at least occasionally the training of the conditioned reflex is carried out, it is able to serve the fish indefinitely. However, when the conditions that led to the formation of the conditioned reflex change, if the action of the conditioned stimulus no longer follows the unconditioned stimulus, the reflex is destroyed.
In fish, conditioned reflexes are easily formed even without our help. My fish immediately swim out of all corners as soon as I find myself near the aquarium, although no one specially accustomed them to this. They firmly know that I will not approach them empty-handed. Another thing is if the aquarium is crowded with children. Kids like to knock on glass more, scare the inhabitants of the aquarium, and the fish hide in advance. This is also a conditioned reflex, only the reflex is not food, but defensive.
There are many types of conditioned reflexes. Their names emphasize some one feature of the reaction, developed in such a way that everyone immediately understands what is at stake. Most often, the name is given in accordance with the reaction that the animal performs. A food conditioned reflex, when a fish swims up to a feeding place, and if it hurries to hide in the thick of underwater plants, they say that it has formed a defensive conditioned reflex.
When studying the mental abilities of fish, they often resort to the development of both food and defensive conditioned reflexes. Usually, the subjects come up with a task a little more difficult than the ability to quickly arrive at the feeding place or hastily escape. The scientists of our country love to make fish grab a bead with their mouths. If you lower a small red ball tied to a thin thread into the water, it will definitely interest the fish. In general, red color attracts them. The fish will certainly grab the ball with its mouth in order to taste it, and, pulling the thread, will try to take it away with it, in order to calmly figure out somewhere on the sidelines whether this thing is edible or not. A conditioned reflex is developed to light or to a call. While the fish swims up to the bead, the light is on, and as soon as the bead is in the mouth of the fish, they throw a worm to it. One or two procedures are enough for the fish to continuously grab the bead, but if the development of the reflex is continued, it will eventually notice that the worm is being given as long as the light is on. Now, as soon as the light comes on, the fish will hastily rush to the bead, and the rest of the time it will not pay any attention to it. She remembered the connection between light, bead and worm, which means that she developed a food reflex to light.
Pisces are capable of solving more complex problems. Three beads are immediately lowered into the aquarium to the minnow, and on the outside, a simple picture is attached to the glass opposite each of them, for example, a black triangle, the same square and circle. The minnow, of course, will immediately become interested in the beads, and the experimenter is closely watching his actions. If they are going to develop a conditioned reflex to a circle, then as soon as the fish swims up to this picture and grabs the bead hanging opposite it, they throw a worm at it. Pictures during the experiment are constantly swapped, and soon the minnow will understand that the worm can only be obtained by pulling the bead hanging against the circle. Now he will not be interested in other pictures and other beads. He developed a food conditioned reflex to the image of a circle. This experience convinced scientists that fish are able to distinguish pictures and remember them well.
To develop a defensive conditioned reflex, the aquarium is divided into two parts by a partition. A hole is left in the partition so that the fish can move from one part to another. Sometimes a door is hung on a hole in the partition, which the fish can easily open by pushing with its nose.
The development of the reflex is carried out according to the usual scheme. A conditioned stimulus is turned on, for example, a bell, and then for a moment they turn on the electric current and continue to spur the fish on with the current until it guesses to open the door in the partition and go to another part of the aquarium. After several repetitions of this procedure, the fish will understand that soon after the start of the sound of the call, very unpleasant and painful effects await it, and, not waiting for them to begin, hastily swims away behind the partition. Conditioned defensive reflexes are often developed faster and last much longer than food ones.
In this chapter, we met with animals that have well-developed conditioned reflexes. In terms of their mental development, animals are approximately the same. True, some of them, namely social insects, are the highest representatives of their branch of the animal kingdom, the highest link in the development of arthropods. There are no smarter arthropods than bees, wasps, ants and termites. Another thing is the fish. They stand at the very first steps in the development of their branch - vertebrates. Among them, they are the most primitive, underdeveloped creatures.
Both ants and fish are able to learn, they are able to notice the patterns of the world around them. Their training, acquaintance with various natural phenomena proceeds through the formation of simple conditioned reflexes. For them, this is the only way to know the world.
All accumulated knowledge is stored in their brain in the form of visual, sound, olfactory and gustatory images, that is, as if duplicates (or copies) of those impressions that were formed at the moment of perception of the corresponding stimuli. The light above the aquarium lit up - and revived in the animal's brain the image of a bead, the image of its own motor reactions, the image of a worm. Obeying this chain of images, the fish swims up to the bead, grabs it and waits for the due reward.
The peculiarity of the knowledge acquired by animals due to the formation of simple conditioned reflexes is that they can notice only those patterns of the surrounding world that are of direct importance to them. The minnow will certainly remember that after a flash of light, under certain conditions, delicious food may appear, and after the sound of the bell, you will feel pain if you do not immediately clean up to another room. My pet fish don't care what I wear when I go to their tank, as it doesn't involve any special benefit or trouble, and they don't care about my clothes. But my dog instantly perks up as soon as I go to the hanger and take the coat. She has long noticed that I go out into the street in a coat, and every time she hopes that they will take her for a walk.
Conditioned reflexes are easily formed and persist for a long time, even if they are not trained, but they can just as easily be destroyed, destroyed. And this is not a defect, but a great advantage of conditioned reflexes. Due to the fact that it is possible to make changes in the developed reflexes and even destroy them, the knowledge acquired by the animal is constantly refined and improved. After the flash of light, the experimenters stopped throwing worms into the aquarium, you see, after a few days the crucian stopped grabbing the bead. The reaction became useless, no reward was given for it, and the conditioned reflex, as scientists say, faded away. They stopped giving the minnow a worm when he pulls a bead hanging against the circle, and the conditioned reflex will soon fade away. They began to give food when he grabs a bead hanging against a square, and a new conditioned reflex is developed in the fish.
From early childhood to very old age, the animal can form more and more conditioned reflexes, and those that have become unnecessary are extinguished. Thanks to this, knowledge is constantly accumulated, refined and polished. They are very necessary for animals, helping to find food, escape from enemies, in general, to survive.
Questions about the sensitivity of fish, their behavioral reactions to capture, pain, stress are constantly raised in scientific specialized publications. Do not forget about this topic and magazines for amateur anglers. True, in most cases, publications highlight personal fabrications about the behavior of a particular species of fish in stressful situations for them.
This article continues the topic raised by the author in the last issue of the journal (No. 1, 2004)
Are fish primitive?
Until the end of the 19th century, fishermen and even many biologists were firmly convinced that fish were very primitive, stupid creatures that did not have not only hearing, touch, but even a developed memory.
Despite the publication of materials refuting this point of view (Parker, 1904 - on the presence of hearing in fish; Zenek, 1903 - observations of the reaction of fish to sound), even in the 1940s, some scientists adhered to the old views.
Now it is a well-known fact that fish, like other vertebrates, are perfectly oriented in space and receive information about their surrounding aquatic environment using the organs of sight, hearing, touch, smell, and taste. Moreover, in many ways the sense organs of "primitive fish" can argue even with the sensory systems of higher vertebrates, mammals. For example, in terms of sensitivity to sounds ranging from 500 to 1000 Hz, the hearing of fish is not inferior to the hearing of animals, and the ability to pick up electromagnetic waves and even use their electroreceptor cells and organs to communicate and exchange information is generally a unique ability of some fish! And the "talent" of many species of fish, including the inhabitants of the Dnieper, to determine the quality of food due to ... the touch of a fish to a food object with a gill cover, fins and even a tail fin?!
In other words, today no one, especially experienced amateur fishermen, will be able to call representatives of the fish tribe creatures “stupid” and “primitive”.
Popular about the nervous system of fish
The study of the physiology of fish and the characteristics of their nervous system, behavior in natural and laboratory conditions has been carried out for a long time. The first major work on the study of the sense of smell in fish, for example, was carried out in Russia as early as the 1870s.
The brain in fish is usually very small (in pike, the brain mass is 300 times less than body weight) and is arranged primitively: the forebrain cortex, which serves as an associative center in higher vertebrates, is completely undeveloped in bony fish. In the structure of the fish brain, a complete separation of the brain centers of different analyzers was noted: the olfactory center is forebrain, visual - average, the center for the analysis and processing of sound stimuli perceived by the lateral line, - cerebellum. Information received by different fish analyzers simultaneously cannot be processed in a complex manner, therefore fish cannot “think and compare”, much less “think” associatively.
However, many scientists believe that bony fish ( which include almost all of our inhabitants of fresh waters - R. N. ) have memory- the ability to figurative and emotional "psychoneurological" activity (albeit in its most rudimentary form).
Fish, like other vertebrates, due to the presence of skin receptors, can perceive various sensations: temperature, pain, tactile (touch). In general, the inhabitants of the kingdom of Neptune are champions in terms of the number of peculiar chemical receptors they have - taste kidneys. These receptors are the endings of the facial ( presented in the skin and on the antennae), glossopharyngeal ( in the mouth and esophagus), wandering ( in the oral cavity on the gills), trigeminal nerves. From the esophagus to the lips, the entire oral cavity is literally strewn with taste buds. In many fish, they are on the antennae, lips, head, fins, scattered throughout the body. Taste buds inform the host about all substances dissolved in water. Fish can taste even those parts of the body where there are no taste buds - with the help of ... their skin.
By the way, thanks to the work of Koppania and Weiss (1922), it turned out that freshwater fish (golden carp) can regenerate a damaged or even cut spinal cord with complete restoration of previously lost functions.
Human activity and conditioned reflexes of fish
A very important, practically dominant, role in the life of fish is played by hereditary and non-hereditary behavioral reactions. Hereditary include, for example, the obligatory orientation of fish with their heads towards the current and their movement against the current. From non-hereditary interesting conditional and unconditioned reflexes.
During life, any fish gains experience and "learns". Changing her behavior in any new conditions, developing a different reaction - this is the formation of the so-called conditioned reflex. For example, it was found that during experimental fishing for ruff, chub, and bream with a fishing rod, these freshwater fish developed a conditioned defensive reflex as a result of 1-3 observations of the capture of fellow flocks. Interesting fact: it is proved that even if the same bream over the next, say, 3-5 years of its life, fishing tackle will not come across on the way, the developed conditioned reflex (catching bream) will not be forgotten, but only slowed down. Seeing how a spotted brother “soars” to the surface of the water, the wise bream will immediately remember what to do in this case - run away! Moreover, to disinhibit the conditioned defensive reflex, only one glance will be enough, and not 1-3! ..
A huge number of examples can be cited when the formation of new conditioned reflexes in relation to human activity was observed in fish. It is noted that in connection with the development of spearfishing, many large fish have accurately recognized the distance of a shot of an underwater gun and do not allow an underwater swimmer closer to this distance. This was first written by J.-I. Cousteau and F. Dumas in the book "In the World of Silence" (1956) and D. Aldridge in "Spearfishing" (1960).
Many anglers are well aware that defensive reflexes to hook tackle, to swinging a rod, walking along the shore or in a boat, fishing line, bait are very quickly created in fish. Predatory fish unmistakably recognize many types of spinners, "learned by heart" their vibrations and vibrations. Naturally, the larger and older the fish, the more conditioned reflexes (read - experience) it has accumulated, and the more difficult it is to catch it with “old” gear. Changing the fishing technique, the range of lures used for a while dramatically increase the catches of anglers, but over time (often even within one season), the same pike or pike perch “master” any new items and put them on their “black list”.
Do fish feel pain?
Any experienced fisherman who fishes different fish from a reservoir can already tell at the stage of hooking which inhabitant of the underwater kingdom he will have to deal with. Strong jerks and desperate resistance of pike, powerful "pressure" to the bottom of the catfish, the practical absence of resistance from pike perch and bream - these "calling cards" of fish behavior are immediately identified by skilled fishermen. Among fishing enthusiasts, there is an opinion that the strength and duration of the struggle of fish directly depends on its sensitivity and the degree of organization of its nervous system. That is, it is understood that among our freshwater fish there are species that are more highly organized and "neurally sensitive", and that there are also fish that are "rough" and insensitive.
This point of view is too straightforward and essentially wrong. In order to know for sure whether our inhabitants of water bodies feel pain and how exactly, let us turn to rich scientific experience, especially since the specialized “ichthyological” literature since the 19th century provides detailed descriptions of the physiology and ecology of fish.
INSERT. Pain is a psychophysiological reaction of the body that occurs with strong irritation of sensitive nerve endings embedded in organs and tissues.
TSB, 1982
Unlike most vertebrates, fish cannot communicate the pain they feel by screaming or moaning. We can judge the pain feeling of fish only by the protective reactions of its body (including characteristic behavior). Back in 1910, R. Gofer found that a pike at rest, with artificial skin irritation (prick), produces a tail movement. Using this method, the scientist showed that the "pain points" of the fish are located on the entire surface of the body, but they were most densely located on the head.
Today it is known that due to the low level of development of the nervous system, pain sensitivity in fish is low. Although, undoubtedly, a spotted fish feels pain ( remember the rich innervation of the head and mouth of fish, the taste buds!). If the hook has stuck into the gills of the fish, the esophagus, the periorbital region, its pain in this case will be stronger than if the hook had pierced the upper / lower jaw or caught on the skin.
INSERT. The behavior of fish on the hook does not depend on the pain sensitivity of a particular individual, but on its individual reaction to stress.
It is known that the pain sensitivity of fish strongly depends on the water temperature: in pike, the rate of nerve impulse conduction at 5°C was 3-4 times lower than the rate of excitation conduction at 20°C. In other words, caught fish are 3-4 times more sick in summer than in winter.
Scientists are sure that the furious resistance of the pike or the passivity of the zander, the bream on the hook during the fight, is only to a small extent due to pain. It has been proven that the reaction of a particular fish species to capture depends more on the severity of the stress received by the fish.
Fishing as a deadly stress factor for fish
For all fish, the process of catching them by an angler, playing them is the strongest stress, sometimes exceeding the stress of fleeing from a predator. For anglers who practice the “catch and release” principle, it will be important to know the following.
Stress reactions in the body of vertebrates are caused by catecholamines(adrenaline and noradrenaline) and cortisol, which operate during two different but overlapping periods of time (Smith, 1986). Changes in the body of fish, caused by the release of adrenaline and norepinephrine, occur in less than 1 second and last from several minutes to hours. Cortisol causes changes that start in less than 1 hour and sometimes last weeks or even months!
If the stress on the fish is prolonged (for example, during a long haul) or very intense (strong fright of the fish, aggravated by pain and, for example, lifting from a great depth), in most cases the caught fish is doomed. She will surely die within a day, even being released into the wild. This statement has been repeatedly proven by ichthyologists in natural conditions (see "Modern Fishing", No. 1, 2004) and experimentally.
In the 1930s-1940s. Homer Smith stated the lethal stress response of the anglerfish to being caught and placed in an aquarium. In a frightened fish, the excretion of water from the body with urine increased sharply, and after 12-22 hours it died ... from dehydration. The death of fish came much faster if they were injured.
A few decades later, fish from American fish ponds were subjected to rigorous physiological studies. Stress in fish caught during planned activities (replanting spawners, etc.) was due to increased activity of fish during seine pursuit, attempts to escape from it, and short-term stay in the air. The caught fish developed hypoxia (oxygen starvation) and, if they still had a loss of scales, the consequences in most cases were lethal.
Other observations (for brook trout) showed that if a fish loses more than 30% of its scales when caught, it dies on the very first day. In fish that lost part of their scale cover, swimming activity faded, individuals lost up to 20% of their body weight, and the fish quietly died in a state of mild paralysis (Smith, 1986).
Some researchers (Wydowski et al., 1976) noted that when trout were caught with a rod, the fish were less stressed than when they lost their scales. The stress reaction proceeded more intensively at high water temperatures and in larger individuals.
Thus, an inquisitive and scientifically "savvy" angler, knowing the peculiarities of the nervous organization of our freshwater fish and the possibility of acquiring conditioned reflexes, learning ability, their attitude to stressful situations, can always plan their vacation on the water and build relationships with the inhabitants of the Neptune kingdom.
I also sincerely hope that this publication will help many anglers to effectively use the rules of fair play - the principle of "catch and release" ...
HIGH NERVOUS ACTIVITY OF LARVAR-CHORD CYCLOSTOMES AND FISH
The higher nervous activity of vertebrates reflects one of the important trends in their evolution - individual perfection. This trend is manifested in increasing life expectancy, a reduction in the number of offspring, an increase in body size, and an increase in the conservatism of heredity. The same tendency is also expressed in the fact that, on the basis of a limited number of species instincts, each individual, in the order of personal life experience, can form a greater number of the most diverse conditioned reflexes.
In such lower chordates as larval-chordates and cyclostomes, conditioned reflexes are of a primitive nature. With the development of the analytical-synthetic activity of the brain and the use of more and more subtle signals in fish, conditioned reflexes begin to play an increasingly significant role in their behavior.
Conditioned reflexes of larval-chordates
Despite the regression of its nervous system, the ascidia can form a conditioned protective reflex of closing the siphons to a sound, or rather, a vibration-mechanical signal.
To develop such a reflex, a dropper was installed over the ascidian sitting in the aquarium. With each impact of a drop on the surface of the water, the ascidia quickly closed the siphons, and with stronger irritation (drop falling from a great height), it pulled them in. The source of the conditioned signals was an electric bell mounted on a table next to the aquarium. Its isolated action lasted 5 s, at the end of which a drop fell. After 20–30 combinations, the bell itself could already evoke defensive movements of the siphons.
Removal of the central ganglion destroyed the developed reflex and made it impossible for the formation of new ones. Persistent attempts to develop similar conditioned reflexes to light in healthy animals were unsuccessful. Obviously, the absence of reactions to light signals is explained by the living conditions of ascidians.
In these experiments it was also found that as a result of combinations of a signal with an unconditioned reaction, the latter was more and more easily evoked by the unconditioned stimulus. It is possible that such a conditional increase in the excitability of the signaled reaction is the initial summation form of a temporary connection, from which more specialized ones developed later.
cyclostomes
The sea lamprey reaches a meter in length. The sexual instinct every spring makes her, like many marine fish, leave the depths of the sea and rise into the rivers for spawning. However, inhibition can be developed for this instinctive reaction (lampreys stopped entering rivers where they encountered polluted water).
The conditioned reflexes of the river lamprey were studied during reinforcement with electric shocks. A light signal (2 lamps of 100 W), to which, after 5–10 s of isolated action, a 1–2 second unconditioned electrocutaneous stimulation was added, after 3–4 combinations, it itself began to cause a motor defensive reaction. However, after 4–5 repetitions, the conditioned reflex decreased and soon disappeared. After 2–3 hours, it could be developed again. It is noteworthy that, simultaneously with a decrease in the conditioned defensive reflex, the value of the unconditioned one also decreased. The threshold of electrocutaneous stimulation to evoke a defensive reaction was increased in this case. It is possible that such changes depended on the traumatic nature of the electrical stimulation.
As was shown above with the example of ascidians, the formation of a conditioned reflex can manifest itself in an increase in the excitability of the signaled reaction. In this case, using the lamprey as an example, it can be seen how, when the conditioned reflex is inhibited, the causative agent of the signaled reaction decreases. Easily forming a conditioned defensive reflex to the light of a lamp, lampreys were unable to develop it to the sound of a bell. Despite 30–70 combinations of the bell with electric shocks, it never became a signal for defensive movements. This indicates a predominantly visual orientation of lampreys in the environment.
Lamprey perceives light stimuli not only with the help of the eyes. Even after transection of the optic nerves or complete removal of the eyes, the reaction to light persisted. It disappeared only when, in addition to the eye, the parietal organ of the brain, which has light-sensitive cells, was also removed. Some nerve cells of the diencephalon and cells located in the skin near the anal fin also have a photoreceptor function.
Having achieved high perfection in adaptation to an aquatic lifestyle, fish have significantly expanded their receptor capabilities, in particular, due to the mechanoreceptors of the lateral line organs. Conditioned reflexes constitute an essential part of the behavior of cartilaginous and especially bony fish.
Cartilaginous fish. The shark's gluttony is proverbial for a reason. Its powerful food instinct is difficult to slow down even with strong pain stimuli. Thus, whalers claim that the shark continues to tear and swallow pieces of the meat of a dead whale, even if you stick a spear into it. On the basis of such pronounced unconditioned food reactions in sharks in a natural setting, many conditioned food reflexes are apparently formed. This, in particular, is evidenced by descriptions of how quickly sharks develop a reaction to escort ships and even swim at a certain time to the board from which kitchen waste is thrown.
Sharks use olfactory food signals very actively. They have been known to follow wounded prey on a trail of blood. The importance of smell for the formation of food reflexes was shown in experiments on small Mustelus laevis, floating freely in the pond. These sharks found live hidden crabs in 10–15 min, and dead and opened crabs in 2–5 min. If the sharks had their nostrils covered with Vaseline cotton, they could not find the hidden crab.
Properties of formation of conditioned defensive reflexes in Black Sea sharks (Squalus acanthias) studied using the technique described above for lampreys. It turned out that sharks developed a conditioned reflex to a bell after 5–8 combinations, and to a lamp only after 8–12 combinations. The developed reflexes were very unstable. They did not last for 24 hours, and the next day they had to be worked out again, although this required fewer combinations than on the first day.
Similar properties of the formation of conditioned defensive reflexes were also found by other representatives of cartilaginous fish - rays. These properties reflect the conditions of their life. Thus, the spiny stingray, an inhabitant of the sea depths, needed 28–30 combinations to develop a reflex to a call, while 4–5 combinations were enough for a mobile inhabitant of coastal waters, the stingray. In these conditioned reflexes, the fragility of temporary connections also manifested itself. The conditioned reflex developed the day before disappeared the next day. It had to be restored each time with two or three combinations.
Bony fish. Due to the enormous diversity in body structure and behavior, bony fish have achieved excellent adaptability to a wide variety of habitat conditions. The little one belongs to these fishes. Mistichthus luzonensis(the smallest vertebrate, 12-14 mm in size), and a giant "herring king" (Regalecus) the southern seas, reaching 7 m in length.
The instincts of fish, especially food and sex, are extremely diverse and specialized. Some fish, such as the vegetarian crucian carp, swim peacefully in muddy ponds, while others, such as the carnivorous pike, live by hunting. Although most fish leave fertilized eggs to their fate, some of them show concern for offspring. For example, blennies guard the laid eggs until the juveniles hatch. The nine-spined stickleback builds a real nest of blades of grass, sticking them together with its mucous secretions. Having completed the construction, the male drives the female into the nest and does not release it until she spawns. After that, he waters the eggs with seminal fluid and guards at the entrance to the nest, from time to time ventilating it with special movements of the pectoral fins.
Freshwater fish from the family cichlidae in case of danger, they hide the hatched juveniles in their mouths. They describe the special "calling" movements of adult fish, with which they collect their fry. Pinagora leads fry, which can be attached to the father's body with special suckers.
Seasonal migrations are a striking manifestation of the strength of the sexual instinct of fish. For example, salmon at certain times of the year rush from the sea to rivers to spawn. Animals and birds exterminate them in masses, many fish die from exhaustion, but the rest stubbornly continue on their way. In an irresistible rush to the upper reaches of the river, the noble salmon, meeting an obstacle, jumps on stones, breaks into blood and again rushes forward until it overcomes it. He jumps rapids and climbs waterfalls. Protective and food instincts are completely inhibited, everything is subordinated to the task of reproduction.
The relationship of fish in a flock reveals a certain hierarchy of subordination to the leader, which can take various forms. Thus, observations are made of a flock of Malabar zebrafish, where the leader swims almost horizontally, which allows him to be the first to see and grab an insect that has fallen to the surface of the water. The rest of the fish are distributed according to ranks and swim with an inclination of 20 to 45 °. A large role in the behavior of fish is played by the pheromones they secrete. For example, when the minnow's skin is damaged, toribons, chemical alarm signals, enter the water. It was enough to drop such water into an aquarium with minnows so that they rushed to flight.
Conditioned reflexes to sound stimuli. Aquarium lovers know well how to train fish to gather at the surface of the water at the signal of tapping on the wall, if you practice this tapping before each feeding. Apparently, such a conditioned food reflex determined the behavior of the famous fish of the monastery pond in Krems (Austria), attracting the attention of tourists by the fact that they swam to the shore at the sound of a bell. Researchers who deny hearing in fish claim that the fish swam only when they saw a person coming to the pond or when his steps caused the ground to shake. However, this does not exclude the participation of sound as one of the parts of the complex stimulus.
The question of the hearing of fish has long been controversial, especially since the fish has neither a cochlea nor the main membrane of the organ of Corti. It was resolved positively only by the objective method of conditioned reflexes (Yu. Frolov, 1925).
The experiments were carried out on freshwater (crucian carp, ruff) and marine (cod, haddock, goby) fish. In a small aquarium, the test fish swam on a leash tied to an air transfer capsule. The same thread was used to bring electric current to the body of the fish, the second pole was a metal plate lying on the bottom. The source of the sound was a telephone receiver. After 30–40 combinations of sounds with electric shocks, an auditory conditioned protective reflex was formed. When the phone was turned on, the fish dived without expecting an electric shock.
In this way, it was possible to develop conditioned reflexes also to various kinds of water vibrations and other signals, such as light.
The defensive reflexes developed on reinforcement with electric current turned out to be very strong. They persisted for a long time and were difficult to extinguish. At the same time, it was not possible to develop reflexes for traces of signals. If the beginning of the unconditioned reinforcement lagged behind the end of the action of the conditioned signal by at least 1 s, the reflex did not form. It was also found that the development of one conditioned reflex facilitated the formation of subsequent ones. Based on the results of these experiments, one can judge a certain inertia and weakness of temporary connections, which, however, are capable of training.
It is not difficult to develop a conditioned food reflex to sound in a golden orphan fish, accompanying the sound signal by lowering a bag of chopped worms into the aquarium. At the fish Umbra limi not only was a similar conditioned positive reflex to a tone of 288 oscillations/s formed, but also a differentiation of the tone of 426 oscillations/s was developed, which was accompanied by the supply of a lump of filter paper moistened with camphor alcohol instead of food.
In order to completely exclude the participation of vision, sound conditioned reflexes were developed on previously blinded pygmy catfish, minnows and loaches. In this way, the upper limit of the audibility of sounds was established, which turned out to be about 12,000 vibrations / s for the catfish, about 6000 for the minnow, and about 2500 for the char. When determining the lower limit of the audibility of sounds, it turned out that fish perceive very slow (2–5 vibrations / s) and even single vibrations of water, which for the human ear are not sounds. These slow fluctuations can be made conditioned stimuli of the food reflex and their differentiation can be worked out. Transection of the nerves of the lateral line organ destroys reflexes to low sounds, the lower limit of audibility rises to 25 Hz. Consequently, the lateral line organ is a kind of infrasonic hearing organ in fish.
Recently, information has been accumulated about the sounds made by fish. It has long been known that Malay fishermen dive into the water to learn by ear where a school of fish is. The "voices" of the fish are recorded on a tape recorder. They turned out to be different in different fish species, higher in fry and lower in adults. Among our Black Sea fish, the croaker turned out to be the most "vociferous". It is noteworthy that in the croaker, the conditioned reflex to the sound is formed after 3–5 combinations, i.e. faster than other studied fish, such as crucian carp, which required 9–15 combinations. However, the croaker develops conditioned reflexes to light signals worse (after 6–18 combinations).
Conditioned reflexes to light stimuli. A variety of conditioned reflexes to food reinforcement were developed during training of fish in order to study their vision. Thus, in experiments with minnows, it was established that they differentiate light stimuli well in terms of brightness, distinguishing between different shades of gray, it was also possible to distinguish between hatched figures by fish, and vertical hatching acquired a signal value faster than horizontal. Experiments with perches, minnows and minnows have shown that fish can differentiate according to the shape of such figures as a triangle and a square, a circle and an oval. It also turned out that visual contrasts are characteristic of fish, reflecting induction phenomena in the brain parts of the analyzers.
If you feed macropods with red chironomid larvae, then soon the fish attacked the aquarium wall when lumps of red wool, similar in size to larvae, were glued to the glass outside. The micropods did not respond to green and white lumps of the same size. If you feed the fish with spools of white bread crumb, then they begin to grab the white woolen lumps that are in sight.
They describe that once a coral predator was given a red-painted satin along with a jellyfish tentacle. The predatory fish at first grabbed the prey, but, having burned themselves on the stinging capsules, immediately released it. After that, she did not take red fish for 20 days.
Especially a lot of research has been carried out on the study of the properties of vision of carps. Thus, in experiments on the development of defensive conditioned reflexes to the presentation of lines as signals, it was shown that fish could differentiate them by the angle of inclination. Based on these and other experiments, suggestions were made about a possible mechanism of visual analysis in fish using detector neurons. The high development of the carp's visual perception is evidenced by its ability to distinguish the color of an object even in different lighting conditions. This property of perceptual constancy manifested itself in the carp in relation to the shape of the object, the reaction to which remained definite, despite its spatial transformations.
Conditioned olfactory, gustatory and temperature reflexes. Fish can develop olfactory and gustatory conditioned reflexes. After being fed musk-scented meat for some time, the minnow began to respond with a typical search response to a previously indifferent musky smell. The smell of skatole or coumarin could be used as an olfactory signal. The signal odor was differentiated from those not reinforced by feeding. Very easily becomes a positive signal for minnows the smell of mucus covering their body. It is possible that such a natural reflex explains some of the properties of the gregarious behavior of these fish.
If earthworms fed to minnows are pre-soaked in a sugar solution, then after 12–14 days the fish will pounce on cotton wool with a sugar solution lowered into the aquarium. Other sweet substances, including saccharin and glycerin, evoked the same reaction. You can develop taste conditioned reflexes to bitter, salty, sour. The threshold of irritation for minnow turned out to be higher for bitter, and lower for sweet than in humans. These reflexes did not depend on olfactory signals, since they persisted even after the removal of the olfactory lobes of the brain.
Observations are described that show that the development of chemoreceptors in fish is associated with the search for and discovery of food. Carps can develop instrumental conditioned reflexes to regulate salinity or acidity of water. In this case, the motor reaction led to the addition of solutions of a given concentration. At the fish Poecilia reticulata Peters developed conditioned food reflexes to the taste of beta-phenylethanol with differentiation to coumarin.
Convincing evidence has been obtained that salmonids, approaching the mouth of the river where they were born, use their sense of smell to find their "native" spawning ground. The high selective sensitivity of their chemoreception is indicated by the results of an electrophysiological experiment in which impulses were recorded in the olfactory bulb only when water from the “native” spawning ground was passed through the nostrils of the fish, and were absent if the water was from the “alien” one. It is known to use trout as a test object for assessing the purity of water after treatment facilities.
You can make the temperature of the water in which the fish swims a conditional food signal. At the same time, it was possible to achieve differentiation of temperature stimuli with an accuracy of 0.4 °C. There are reasons to believe that natural temperature signals play an important role in the sexual behavior of fish, in particular, in spawning migrations.
Complex food-procuring reflexes. For a better comparison of indicators of conditioned reflex activity of different animal species, natural food-procuring movements are used. Such a movement for fish is the grasping of a bead suspended on a string. The first random grasps are reinforced with food and combined with an auditory or visual signal, to which a conditioned reflex is formed. Such a conditioned visual reflex, for example, was formed and strengthened in crucian carp in 30–40 combinations. Differentiation by color and a conditional brake were also developed. However, repeated modifications of the signal value of positive and negative stimuli proved to be an extremely difficult task for fish and even led to disturbances in conditioned reflex activity.
Studies of the behavior of fish in labyrinths have shown their ability to develop a reaction of unmistakably choosing the right path.
Yes, dark-loving fish Tundulus after 12–16 trials for two days, she began to swim through the openings of the screens, without going into dead ends, right into the corner where food was waiting. In similar experiments with goldfish, the time for searching for a way out of the maze for 36 trials decreased from 105 to 5 minutes. After a 2-week break in work, the acquired skill has changed only slightly. However, with more complex mazes, such as those used for rats, the fish could not cope, despite hundreds of trials.
Predatory fish can develop a conditioned reflex suppression of the hunting instinct.
If you place crucian carp behind a glass partition in an aquarium with a pike, then the pike will immediately rush at him. However, after several headbutts on the glass, the attacks stop. After a few days, the pike no longer tries to grab the crucian. The natural food reflex is completely extinguished. Then the partition is removed, and crucian carp can swim next to the pike. A similar experiment was carried out with predatory perches and minnows. Predators and their usual victims lived peacefully together.
Another example of a conditioned reflex transformation of instinctive behavior was shown by an experiment with cichlid fish, which, during their first spawning, had their eggs replaced with caviar of an alien species. When the fry hatched, the fish began to take care of them and protect them, and when they brought fry of their own species to the next spawning, they drove them as strangers. Thus, the developed conditioned reflexes turned out to be very conservative. On the basis of reinforcement with food and defensive reactions, various motor conditioned reflexes were developed in fish. For example, a goldfish was taught to swim through a ring, to make “dead loops”, a brilliant betta fighting fish, accustomed to pass through a hole in a barrier, began to jump into it even when it was raised above the water.
The behavior of fish, their unconditioned and conditioned reflexes are largely determined by the environmental factors of the habitat, which leaves its mark on the development of the nervous system and the formation of its properties.
Development of defensive conditioned reflexes in fry. The regulation of the flow of rivers, the construction of hydroelectric dams and reclamation systems, to a greater or lesser extent, makes it difficult for fish to reach natural spawning grounds. Therefore, artificial fish farming is becoming increasingly important.
Every year, billions of fry hatched at hatcheries are released into lakes, rivers and seas. But only a small part of them survive to commercial age. Grown in artificial conditions, they often turn out to be poorly adapted to life in the wild. In particular, fry that have not had life experience in the formation of protective reactions easily become the prey of predatory fish, from which they do not even try to escape. In order to increase the survival rate of fry released by fish breeding stations, experiments were undertaken to artificially develop in them protective conditioned reflexes to the approach of predatory fish.
In preliminary tests, the properties of the formation of such reflexes to visual, auditory and vibrational signals were studied. If, among the roach fry, shiny metal plates shaped like the body of a bee-eater are placed, and a current is passed through these plates, then the fry begin to avoid these figures even in the absence of a current. The reflex is developed very quickly (Fig. 84).
Rice. 84. Development of a conditioned defensive reflex in roach fry to the appearance of a predatory fish model for 1 hour (according to G.V. Popov):
1 - 35 day fry, 2 - 55 days
To assess how much the development of artificial defensive reflexes can increase the survival rate of juveniles, we compared the rate at which a predator eats fry that have undergone training and fry that have not had such training.
For this, cages were installed in the pond. One predatory fish was placed in each cage - a chub and a precisely counted number of fish fry. After 1 or 2 days, we counted how many fry remained alive and how many were eaten by the predator. It turned out that of the fry that did not develop defensive reflexes, almost half perished during the first day. It is noteworthy that the second day adds little in this regard. It can be assumed that the surviving fry have time to form natural conditioned defensive reflexes and successfully escape from the persecution of the predator. Indeed, if they are taken after such a natural preparation in special experiments, then the percentage of death turns out to be either relatively small, or even zero.
Fry with artificially developed conditioned defensive reflexes both to the appearance of the figure of a predatory fish and to the shaking of the water, imitating its movements, suffered the least from the chub. In most of the experiments, the predator, even within two days, was unable to catch a single one of them.
The recently developed simple technique for cultivating protective reflexes in the fry of commercial fish during their rearing can bring significant practical benefits to fish breeding.
From the book Reactions and Behavior of Dogs in Extreme Conditions author Gerd Maria AlexandrovnaHigher nervous activity Twenty to twenty-five days prior to the start of the experiments, an attempt was made to characterize the main features of the nervous processes of each experimental dog, for which examinations were carried out using the samples described in detail on p. 90 of this book. By virtue of
From the book Fundamentals of the Physiology of Higher Nervous Activity author Kogan Alexander BorisovichChapter 7 ANALYTICAL AND SYNTHETIC ACTIVITY OF THE BRAIN All higher nervous activity consists of continuous analysis - the division of stimuli of the surrounding world into their ever simpler elements, and synthesis - the reverse merging of these elements into a holistic perception
From the book A Brief History of Biology [From Alchemy to Genetics] author Asimov Isaac From the book Homeopathic Treatment of Cats and Dogs author Hamilton DonCHAPTER 13 THE HIGHEST NERVOUS ACTIVITY OF Amphibians, Reptiles, and Birds The modern descendants of the first inhabitants of the land have preserved in their organization and behavior many traces of the breakdown that accompanied the exit of animals from the water element. This is seen, for example, when
From the book Biology [A complete guide to preparing for the exam] author Lerner Georgy IsaakovichCHAPTER 14 THE HIGHEST NERVOUS ACTIVITY OF RODENTS AND UNGATES After the catastrophic end of the era of cold-blooded giants, unable to adapt to the new conditions of life, warm-blooded mammals occupied a dominant position in the animal kingdom. High level of exchange
From the book Fundamentals of Psychophysiology author Alexandrov YuriCHAPTER 15 THE HIGHEST NERVOUS ACTIVITY OF PREDATORS In the life of predators, the adaptive significance of higher nervous activity manifests itself most clearly in the fierce struggle for existence. In addition to the continuous development of new conditioned defense reflexes against stronger enemies,
From the book Embryos, Genes and Evolution the author Raff Rudolph ACHAPTER 16 THE HIGHER NERVOUS ACTIVITY OF MONKEYS The study of the higher nervous activity of monkeys is of particular interest for two reasons. Firstly, monkeys are the most highly developed animals mentally, and secondly, they are the closest representatives to humans.
From the book Origin of the Brain author Saveliev Sergey VyacheslavovichChapter 17 THE HIGHEST NERVOUS ACTIVITY OF HUMANS Life at every step shows the immeasurable superiority of the mind of people over the primitive mental abilities of animals. The huge gap between the mental life of man and animals has long served as a reason for
From the author's bookCHAPTER 10 THE NERVOUS SYSTEM Hypnotism Another type of disease that does not fall under Pasteur's theory is that of the nervous system. Such diseases have confused and frightened humanity from time immemorial. Hippocrates approached them rationalistically, but most
From the author's bookChapter XIII Nervous System Functions The nervous system of living beings has two main functions. The first is sensory perception, thanks to which we perceive and comprehend the world around us. Through the centripetal sensory nerves, impulses from all five organs
From the author's book From the author's book§ 25. Theories of the origin of chordates There are several points of view on the origin of chordates, which differ both in approaches to solving the problem and in animals chosen as representatives of ancestral groups. The most famous hypotheses of the origin of chordates
From the author's book§ 26. Origin of the nervous system of chordates The most frequently discussed hypotheses of origin cannot explain the appearance of one of the main features of chordates - the tubular nervous system, which is located on the dorsal side of the body. I would like to use