The question of whether fish hear has been debated for a long time. It has now been established that fish hear and make sounds themselves. Sound is a chain of regularly repeating compression waves of a gaseous, liquid or solid medium, i.e. in an aquatic environment, sound signals are as natural as on land. Compression waves in the aquatic environment can propagate at different frequencies. Low-frequency vibrations (vibration or infrasound) up to 16 Hz are not perceived by all fish. However, in some species, infrasound reception has been brought to perfection (sharks). The spectrum of sound frequencies perceived by most fish lies in the range of 50-3000 Hz. Ability for fish to perceive ultra sound waves(over 20,000 Hz) has not yet been convincingly proven.
The speed of sound propagation in water is 4.5 times greater than in air. Therefore, sound signals from the shore reach the fish in a distorted form. The hearing acuity of fish is not as developed as that of land animals. Nevertheless, in some species of fish, quite decent musical abilities have been observed in experiments. For example, a minnow distinguishes 1/2 tone at 400-800 Hz. The capabilities of other fish species are more modest. Thus, guppies and eels differentiate two that differ by 1/2-1/4 octaves. There are also species that are completely musically mediocre (bladderless and labyrinthine fish).
Rice. 2.18. Connection between the swim bladder and the inner ear different types fish: a- Atlantic herring; b - cod; c - carp; 1 - outgrowths of the swim bladder; 2- inner ear; 3 - brain: 4 and 5 bones of the Weberian apparatus; common endolymphatic duct
Hearing acuity is determined by the morphology of the acoustic-lateral system, which, in addition to the lateral line and its derivatives, includes the inner ear, the swim bladder and the Weber’s apparatus (Fig. 2.18).
Both in the labyrinth and in the lateral line, the sensory cells are the so-called hairy cells. Displacement of the hair of a sensitive cell both in the labyrinth and in the lateral line leads to the same result - the generation of a nerve impulse entering the same acoustic-lateral center medulla oblongata. However, these organs also receive other signals (gravitational field, electromagnetic and hydrodynamic fields, as well as mechanical and chemical stimuli).
The hearing apparatus of fish is represented by the labyrinth, swim bladder (in bladder fish), Weber's apparatus and the lateral line system. Labyrinth. A paired formation - the labyrinth, or inner ear of fish (Fig. 2.19), performs the function of an organ of balance and hearing. Auditory receptors are present in large numbers in the two lower chambers of the labyrinth - the lagena and the utriculus. The hairs of the auditory receptors are very sensitive to the movement of endolymph in the labyrinth. A change in the position of the fish's body in any plane leads to the movement of endolymph in at least one of the semicircular canals, which irritates the hairs.
In the endolymph of the saccule, utriculus and lagena there are otoliths (pebbles), which increase sensitivity inner ear.
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Rice. 2.19. Fish labyrinth: 1-round pouch (lagena); 2-ampule (utriculus); 3-saccula; 4-channel labyrinth; 5- location of otoliths
Their total three on each side. They differ not only in location, but also in size. The largest otolith (pebble) is located in a round sac - lagena.
On the otoliths of fish, annual rings are clearly visible, by which the age of some fish species is determined. They also provide an assessment of the effectiveness of the fish's maneuver. With longitudinal, vertical, lateral and rotational movements of the fish's body, some displacement of the otoliths occurs and irritation of the sensitive hairs occurs, which, in turn, creates a corresponding afferent flow. They (otoliths) are also responsible for the reception of the gravitational field and the assessment of the degree of acceleration of the fish during throws.
The endolymphatic duct departs from the labyrinth (see Fig. 2.18.6), which is closed in bony fishes, and open in cartilaginous fishes and communicates with the external environment. Weber apparatus. It is represented by three pairs of movably connected bones, which are called stapes (in contact with the labyrinth), incus and maleus (this bone is connected to the swim bladder). The bones of the Weberian apparatus are the result of the evolutionary transformation of the first trunk vertebrae (Fig. 2.20, 2.21).
With the help of the Weberian apparatus, the labyrinth is in contact with the swim bladder in all bladder fish. In other words, the Weber apparatus provides communication between the central structures of the sensory system and the periphery that perceives sound.
Fig.2.20. Structure of the Weberian apparatus:
1- perilymphatic duct; 2, 4, 6, 8- ligaments; 3 - stapes; 5- incus; 7- maleus; 8 - swim bladder (vertebrae are indicated by Roman numerals)
Rice. 2.21. General diagram of the structure of the hearing organ in fish:
1 - brain; 2 - utriculus; 3 - saccula; 4- connecting channel; 5 - lagena; 6- perilymphatic duct; 7-steps; 8- incus; 9-maleus; 10- swim bladder
Swim bladder. It is a good resonating device, a kind of amplifier of medium and low frequency vibrations of the medium. A sound wave from the outside leads to vibrations of the wall of the swim bladder, which, in turn, lead to a displacement of the chain of bones of the Weberian apparatus. The first pair of ossicles of the Weberian apparatus presses on the membrane of the labyrinth, causing displacement of the endolymph and otoliths. Thus, if we draw an analogy with higher terrestrial animals, the Weberian apparatus in fish performs the function of the middle ear.
However, not all fish have a swim bladder and Weberian apparatus. In this case, the fish show low sensitivity to sound. In bladderless fish, the auditory function of the swim bladder is partially compensated by the air cavities associated with the labyrinth and the high sensitivity of the lateral line organs to sound stimuli (water compression waves).
Side line. It is a very ancient sensory formation, which, even in evolutionarily young groups of fish, simultaneously performs several functions. Taking into account the exceptional importance of this organ for fish, let us dwell in more detail on its morphofunctional characteristics. Different ecological types of fish demonstrate various options lateral system. The location of the lateral line on the body of fish is often a species-specific feature. There are species of fish that have more than one lateral line. For example, the greenling has four lateral lines on each side, hence
This is where its second name comes from - “eight-line chir”. In most bony fish, the lateral line stretches along the body (without interruption or interruption in some places), reaches the head, forming a complex system of canals. The lateral line canals are located either inside the skin (Fig. 2.22) or openly on its surface.
An example of an open superficial arrangement of neuromasts is structural units lateral line - is the lateral line of the minnow. Despite the obvious diversity in the morphology of the lateral system, it should be emphasized that the observed differences concern only the macrostructure of this sensory formation. The organ's receptor apparatus itself (the chain of neuromasts) is surprisingly the same in all fish, both morphologically and functionally.
The lateral line system responds to compression waves of the aquatic environment, flow currents, chemical stimuli and electromagnetic fields with the help of neuromasts - structures that unite several hair cells (Fig. 2.23).
Rice. 2.22. Fish lateral line channel
The neuromast consists of a mucous-gelatinous part - a capsule, into which the hairs of sensitive cells are immersed. Closed neuromasts communicate with the external environment through small holes that pierce the scales.
Open neuromasts are characteristic of the canals of the lateral system extending onto the head of the fish (see Fig. 2.23, a).
Channel neuromasts stretch from head to tail along the sides of the body, usually in one row (fishes of the family Hexagramidae have six rows or more). The term “lateral line” in common usage refers specifically to canal neuromasts. However, neuromasts are also described in fish, separated from the canal part and looking like independent organs.
Channel and free neuromasts, located in different parts of the fish’s body, and the labyrinth do not duplicate, but functionally complement each other. It is believed that the sacculus and lagena of the inner ear provide the sound sensitivity of fish from a great distance, and the lateral system makes it possible to localize the sound source (though already close to the sound source).
Rice. 2.23. The structure of the neuromastaryba: a - open; b - channel
It has been experimentally proven that the lateral line perceives low-frequency vibrations, both sound and those associated with the movement of other fish, i.e. low-frequency vibrations arising from a fish hitting the water with its tail are perceived by other fish as low-frequency sounds.
Thus, the sound background of a reservoir is quite diverse and fish have a perfect system of organs for perceiving wave physical phenomena under water.
Waves arising on the surface of the water have a noticeable influence on the activity of fish and the nature of their behavior. The causes of this physical phenomenon are many factors: the movement of large objects ( big fish, birds, animals), wind, tides, earthquakes. Excitement serves as an important channel for informing aquatic animals about events both in the body of water and beyond. Moreover, the disturbance of the reservoir is perceived by both pelagic and bottom fish. The reaction to surface waves on the part of fish is of two types: the fish sinks to greater depths or moves to another part of the reservoir. The stimulus acting on the body of the fish during the period of disturbance of the reservoir is the movement of water relative to the body of the fish. The movement of water when it is agitated is sensed by the acoustic-lateral system, and the sensitivity of the lateral line to waves is extremely high. Thus, for afferentation to occur from the lateral line, a displacement of the cupula by 0.1 μm is sufficient. At the same time, the fish is able to very accurately localize both the source of wave formation and the direction of wave propagation. The spatial diagram of fish sensitivity is species-specific (Fig. 2.26).
In the experiments, an artificial wave generator was used as a very strong stimulus. When its location changed, the fish unmistakably found the source of disturbance. The response to the wave source consists of two phases.
The first phase - the freezing phase - is the result of an indicative reaction (innate exploratory reflex). The duration of this phase is determined by many factors, the most significant of which are the height of the wave and the depth of the fish's dive. For cyprinid fish (carp, crucian carp, roach), with a wave height of 2-12 mm and fish immersion of 20-140 mm, the orientation reflex took 200-250 ms.
The second phase is the movement phase - a conditioned reflex reaction is developed in fish quite quickly. For intact fish, from two to six reinforcements are sufficient for its occurrence; in blinded fish, after six combinations of wave formation of food reinforcement, a stable search food-procuring reflex was developed.
Small pelagic planktivores are more sensitive to surface waves, while large bottom-dwelling fish are less sensitive. Thus, blinded verkhovs with a wave height of only 1-3 mm already after the first presentation of the stimulus demonstrated indicative reaction. Marine bottom fish are characterized by sensitivity to strong waves on the sea surface. At a depth of 500 m, their lateral line is excited when the wave height reaches 3 m and length 100 m. As a rule, waves on the surface of the sea generate rolling motion. Therefore, during waves, not only the lateral line of the fish becomes excited, but also its labyrinth. The results of experiments showed that the semicircular canals of the labyrinth respond to rotational movements in which water currents involve the body of the fish. The utriculus senses the linear acceleration that occurs during the pumping process. During a storm, the behavior of both solitary and schooling fish changes. During a weak storm, pelagic species in the coastal zone descend to the bottom layers. When the waves are strong, fish migrate to the open sea and go to greater depths, where the influence of waves is less noticeable. It is obvious that strong excitement is assessed by fish as unfavorable or even dangerous factor. It suppresses feeding behavior and forces fish to migrate. Illogical changes in eating behavior are also observed in fish species living in inland waters. Fishermen know that when the sea is rough, the fish stop biting.
Thus, the body of water in which the fish lives is a source of various information transmitted through several channels. Such awareness of fish about fluctuations in the external environment allows it to respond to them in a timely and adequate manner with locomotor reactions and changes in vegetative functions.
Fish signals. It is obvious that fish themselves are a source of various signals. They produce sounds in the frequency range from 20 Hz to 12 kHz, leave a chemical trace (pheromones, kairomones), and have their own electric and hydrodynamic fields. Acoustic and hydrodynamic fields of fish are created in various ways.
The sounds made by fish are quite varied, however, due to low pressure They can only be recorded using special highly sensitive equipment. The mechanism of sound wave formation in different fish species may be different (Table 2.5).
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2.5. Fish sounds and the mechanism of their reproduction |
Fish sounds are species specific. In addition, the nature of the sound depends on the age of the fish and its physiological state. The sounds coming from the school and from individual fish are also clearly distinguishable. For example, the sounds made by bream resemble wheezing. The sound pattern of a school of herring is associated with squeaking. The Black Sea gurnard makes sounds reminiscent of the clucking of a hen. The freshwater drummer identifies itself by drumming. Roaches, loaches, and scale insects emit squeaks that are perceptible to the naked ear.
It is still difficult to unambiguously characterize the biological significance of the sounds made by fish. Some of them are background noise. Within populations, schools, and also between sexual partners, sounds made by fish can also perform a communicative function.
Noise direction finding is successfully used in industrial fishing. The excess of the sound background of fish over ambient noise is no more than 15 dB. The background noise of a ship can be ten times greater than the soundscape of a fish. Therefore, fish bearing is only possible from those vessels that can operate in “silence” mode, that is, with the engines turned off.
Thus, the well-known expression “dumb as a fish” is clearly not true. All fish have a perfect sound reception apparatus. In addition, fish are sources of acoustic and hydrodynamic fields, which they actively use to communicate within the school, detect prey, and warn relatives about possible danger and other purposes.
As is known, for a long time the fish were considered deaf.
After scientists conducted experiments here and abroad using the method of conditioned reflexes (in particular, among the experimental subjects were crucian carp, perch, tench, ruffe and other freshwater fish), it was convincingly proven that fish hear, the boundaries of the hearing organ were also determined, his physiological functions and physical parameters.
Hearing, along with vision, is the most important of the senses of remote (non-contact) action; with its help, fish navigate their environment. Without knowledge of the hearing properties of fish, it is impossible to fully understand how the connection between individuals in a school is maintained, how fish relate to fishing gear, and what the relationship between predator and prey is. Progressive bionics requires a wealth of accumulated facts on the structure and functioning of the hearing organ in fish.
Observant and savvy recreational fishermen have long benefited from the ability of some fish to hear noise. This is how the method of catching catfish with a “shred” was born. A frog is also used in the nozzle; Trying to free itself, the frog, raking with its paws, creates a noise that is well known to the catfish, which often appears right there.
So the fish hear. Let's look at their hearing organ. In fish you cannot find what is called the external organ of hearing or ears. Why?
At the beginning of this book, we mentioned the physical properties of water as an acoustic medium transparent to sound. How useful would it be for the inhabitants of the seas and lakes to be able to prick up their ears, like an elk or a lynx, in order to catch a distant rustle and timely detect a sneaking enemy. But bad luck - it turns out that having ears is not economical for movement. Have you looked at the pike? Her entire chiseled body is adapted for rapid acceleration and throwing - nothing unnecessary that would make movement difficult.
Fish also do not have the so-called middle ear, which is characteristic of land animals. In terrestrial animals, the middle ear apparatus plays the role of a miniature and simply designed transceiver of sound vibrations, carrying out its work through the eardrum and auditory ossicles. These “parts” that make up the structure of the middle ear of land animals have a different purpose, a different structure, and a different name in fish. And not by chance. The outer and middle ear with its eardrum is not biologically justified under conditions of high pressures of a dense mass of water that quickly increase with depth. It is interesting to note that in aquatic mammals - cetaceans, whose ancestors left land and returned to water, the tympanic cavity has no exit to the outside, since the external auditory canal is either closed or blocked by an ear plug.
And yet fish have a hearing organ. Here is its diagram (see picture). Nature took care that this very fragile, thin organized organ was sufficiently protected - by this she seemed to emphasize its importance. (And you and I have a particularly thick bone that protects our inner ear). Here's a labyrinth 2
. The hearing ability of fish is associated with it (semicircular canals - balance analyzers). Pay attention to the departments indicated by numbers 1
And 3
. These are lagena and sacculus - auditory receivers, receptors that perceive sound waves. When, in one of the experiments, the lower part of the labyrinth - the sacculus and lagena - was removed from minnows with a developed food reflex to sound, they stopped responding to signals.
Irritation along the auditory nerves is transmitted to the auditory center located in the brain, where the as yet unknown processes of converting the received signal into images and the formation of a response occur.
There are two main types of fish auditory organs: organs without connection with the swim bladder and organs with integral part which is the swim bladder.
The swim bladder is connected to the inner ear using the Weberian apparatus - four pairs of movably articulated bones. And although the middle ear no fish, some of them (cyprinids, catfishes, characinids, electric eels) have a substitute for it - a swim bladder plus a Weberian apparatus.
Until now, you knew that the swim bladder is a hydrostatic apparatus that regulates specific gravity body (and also the fact that the bladder is an essential component of a full-fledged crucian fish soup). But it is useful to know something more about this organ. Namely: the swim bladder acts as a receiver and transducer of sounds (similar to our eardrum). The vibration of its walls is transmitted through the Weber apparatus and is perceived by the fish’s ear as vibrations of a certain frequency and intensity. Acoustically, a swim bladder is essentially the same as an air chamber placed in water; hence the important acoustic properties of the swim bladder. Due to the differences in the physical properties of water and air, the acoustic receiver
such as a thin rubber bulb or swim bladder, filled with air and placed in water, when connected to the diaphragm of a microphone, it dramatically increases its sensitivity. Inner ear the fish is the “microphone” that works in conjunction with the swim bladder. In practice, this means that although the water-air interface strongly reflects sounds, fish are still sensitive to voices and noise from the surface.
The well-known bream is very sensitive during the spawning period and is afraid of the slightest noise. In the old days, it was even forbidden to ring bells during bream spawning.
The swim bladder not only increases hearing sensitivity, but also expands the perceived frequency range of sounds. Depending on how many times sound vibrations are repeated in 1 second, the frequency of sound is measured: 1 vibration per second - 1 hertz. The ticking of a pocket watch can be heard in the frequency range from 1500 to 3000 hertz. For clear, intelligible speech on the telephone, a frequency range from 500 to 2000 hertz is sufficient. So we could talk to the minnow on the phone, because this fish responds to sounds in the frequency range from 40 to 6000 hertz. But if guppies “came” to the phone, they would only hear those sounds that lie in the band up to 1200 hertz. Guppies lack a swimbladder, and their hearing system does not perceive higher frequencies.
At the end of the last century, experimenters sometimes did not take into account the ability of various species of fish to perceive sounds in a limited frequency range and made erroneous conclusions about the lack of hearing in fish.
At first glance, it may seem that the capabilities of the fish’s auditory organ cannot be compared with the extremely sensitive ear a person capable of detecting sounds of negligible intensity and distinguishing sounds whose frequencies lie in the range from 20 to 20,000 hertz. Nevertheless, fish are perfectly oriented in their native elements, and sometimes limited frequency selectivity turns out to be advisable, because it allows one to isolate from the stream of noise only those sounds that turn out to be useful for the individual.
If a sound is characterized by any one frequency, we have a pure tone. A pure, unadulterated tone is obtained using a tuning fork or a sound generator. Most of the sounds around us contain a mixture of frequencies, a combination of tones and shades of tones.
A reliable sign of developed acute hearing is the ability to distinguish tones. The human ear is capable of distinguishing about half a million simple tones, varying in pitch and volume. What about the fish?
Minnows are able to distinguish sounds different frequencies. Trained to a specific tone, they can remember that tone and respond to it one to nine months after training. Some individuals can remember up to five tones, for example, “do”, “re”, “mi”, “fa”, “sol”, and if the “food” tone during training was “re”, then the minnow is able to distinguish it from the neighboring one. a low tone "C" and a higher tone "E". Moreover, minnows in the frequency range 400-800 hertz are able to distinguish sounds that differ in pitch by half a tone. Suffice it to say that a piano keyboard, satisfying the most subtle human hearing, contains 12 semitones of an octave (a frequency ratio of two is called an octave in music). Well, perhaps minnows also have some musicality.
Compared to the “listening” minnow, the macropod is not musical. However, the macropod also distinguishes two tones if they are 1 1/3 octaves apart from each other. We can mention the eel, which is remarkable not only because it goes to spawn distant seas, but also because it is able to distinguish sounds that differ in frequency by an octave. The above about the hearing acuity of fish and their ability to remember tones makes us re-read the lines of the famous Austrian scuba diver G. Hass in a new way: “At least three hundred large silvery star mackerel swam up in a solid mass and began to circle around the loudspeaker. They kept a distance of about three meters from me and swam as if in a big round dance. It is likely that the sounds of the waltz - it was Johann Strauss's "Southern Roses" - had nothing to do with this scene, and only curiosity, or at best sounds, attracted the animals. But the impression of the waltz of the fish was so complete that I later conveyed it in our film as I observed it myself.”
Let's now try to understand in more detail - what is the sensitivity of fish hearing?
We see two people talking in the distance, we see the facial expressions of each of them, gestures, but we do not hear their voices at all. The flow of sound energy flowing into the ear is so small that it does not cause auditory sensation.
In this case, hearing sensitivity can be assessed by the lowest intensity (loudness) of sound that the ear detects. It is by no means the same across the entire range of frequencies perceived by a given individual.
The highest sensitivity to sounds in humans is observed in the frequency range from 1000 to 4000 hertz.
In one of the experiments, the brook chub perceived the weakest sound at a frequency of 280 hertz. At a frequency of 2000 hertz, his auditory sensitivity was halved. In general, fish hear low sounds better.
Of course, hearing sensitivity is measured from some entry level, taken as the sensitivity threshold. Since a sound wave of sufficient intensity produces quite noticeable pressure, it was agreed to define the smallest threshold strength (or loudness) of sound in units of the pressure it exerts. Such a unit is an acoustic bar. The normal human ear begins to detect sound whose pressure exceeds 0.0002 bar. To understand how insignificant this value is, let us explain that the sound of a pocket watch pressed to the ear exerts a pressure on the eardrum that exceeds the threshold by 1000 times! In a very “quiet” room, the sound pressure level exceeds the threshold by 10 times. This means that our ear records a sound background that we sometimes consciously fail to appreciate. For comparison, note that the eardrum experiences pain when the pressure exceeds 1000 bar. We feel such a powerful sound when standing not far from a jet plane taking off.
We have given all these figures and examples of the sensitivity of human hearing only in order to compare them with the auditory sensitivity of fish. But it is no coincidence that they say that any comparison is lame. The aquatic environment and the structural features of the auditory organ of fish make noticeable adjustments to comparative measurements. However, under conditions of increased environmental pressure, the sensitivity of human hearing also noticeably decreases. Be that as it may, the dwarf catfish has a hearing sensitivity no worse than that of humans. This seems amazing, especially since fish do not have the organ of Corti in their inner ear - the most sensitive, subtle “device”, which in humans is the actual organ of hearing.
It's all like this: the fish hears the sound, the fish distinguishes one signal from another by frequency and intensity. But you should always remember that the hearing abilities of fish are not the same not only between species, but also among individuals of the same species. If we can still talk about some kind of “average” human ear, then in relation to the hearing of fish, no template whatsoever is applicable, because the peculiarities of the hearing of fish are the result of life in a specific environment. The question may arise: how does a fish find the source of sound? It is not enough to hear the signal, you need to focus on it. It is vitally important for crucian carp, which has reached a formidable danger signal - the sound of food excitement of the pike, to localize this sound.
Most fish studied are capable of localizing sounds in space at distances from sources approximately equal to the length of the sound wave; At long distances, fish usually lose the ability to determine the direction to the source of sound and make prowling, searching movements, which can be deciphered as an “attention” signal. This specificity of the action of the localization mechanism is explained by the independent operation of two receivers in fish: the ear and the lateral line. The fish's ear often works in combination with the swim bladder and perceives sound vibrations in a wide range of frequencies. The lateral line records the pressure and mechanical displacement of water particles. No matter how small the mechanical displacements of water particles caused by sound pressure are, they must be sufficient to be noted by living “seismographs” - sensitive cells of the lateral line. Apparently, the fish receives information about the location of the source of low-frequency sound in space by two indicators at once: the amount of displacement (lateral line) and the amount of pressure (ear). Special experiments were carried out to determine the ability of river perches to detect sources of underwater sounds emitted through a tape recorder and waterproof dynamic headphones. The previously recorded sounds of feeding were played into the water of the pool - the capture and grinding of food by perches. This kind of experiment in an aquarium is greatly complicated by the fact that multiple echoes from the walls of the pool seem to smear and muffle the main sound. A similar effect is observed in a spacious room with a low vaulted ceiling. Nevertheless, perches showed the ability to directionally detect the source of sound from a distance of up to two meters.
The method of food conditioned reflexes helped to establish in an aquarium that crucian carp and carp are also capable of determining the direction to the source of sound. Some sea fish(mackerels, roulens, mullet) in experiments in an aquarium and in the sea, they detected the location of the sound source from a distance of 4-7 meters.
But the conditions under which experiments are carried out to determine this or that acoustic ability of fish do not yet give an idea of how sound signaling is carried out in fish in a natural environment where the ambient background noise is high. An audio signal carrying useful information only makes sense when it reaches the receiver in an undistorted form, and this circumstance does not require special explanation.
Experimental fish, including roach and river perch, kept in small schools in an aquarium, developed a conditioned food reflex. As you may have noticed, the food reflex appears in many experiments. The fact is that the feeding reflex is quickly developed in fish, and it is the most stable. Aquarists know this well. Who among them has not performed a simple experiment: feeding the fish with a portion of bloodworms, while tapping on the glass of the aquarium. After several repetitions, hearing a familiar knock, the fish rush together “to the table” - they have developed a feeding reflex to the conditioned signal.
In the above experiment, two types of conditioned food signals were given: a single-tone sound signal with a frequency of 500 hertz, rhythmically emitted through an earphone using a sound generator, and a noise “bouquet” consisting of sounds pre-recorded on a tape recorder that occur when individuals feed. To create noise interference, a stream of water was poured into the aquarium from a height. The background noise it created, as measurements showed, contained all frequencies of the sound spectrum. It was necessary to find out whether fish are able to isolate a food signal and respond to it under camouflage conditions.
It turned out that fish are able to isolate useful signals from noise. Moreover, the fish clearly recognized a monophonic sound, delivered rhythmically, even when a trickle of falling water “clogged” it.
Sounds of a noise nature (rustling, slurping, rustling, gurgling, hissing, etc.) are emitted by fish (like humans) only in cases where they exceed the level of surrounding noise.
This and other similar experiments prove the ability of fish hearing to isolate vital signals from a set of sounds and noises that are useless for an individual of a given species, which are present in abundance in natural conditions in any body of water that has life.
On several pages we examined the hearing capabilities of fish. Aquarium lovers, if they have simple and accessible instruments, which we will discuss in the corresponding chapter, could independently carry out some simple experiments: for example, determining the ability of fish to focus on a sound source when it has biological significance for them, or the ability of fish to emit such sounds against the background of other “useless” noise, or detection of the hearing limit of a particular type of fish, etc.
Much is still unknown, much needs to be understood in the structure and operation of the hearing apparatus of fish.
The sounds made by cod and herring have been well studied, but their hearing has not been studied; in other fish it is just the opposite. The acoustic capabilities of representatives of the goby family have been more fully studied. So, one of them, the black goby, perceives sounds not exceeding a frequency of 800-900 hertz. Everything that goes beyond this frequency barrier does not “touch” the bull. His auditory capabilities allow him to perceive the hoarse, low grunt emitted by his opponent through the swim bladder; this grumbling in a certain situation can be deciphered as a threat signal. But high-frequency components of sounds that arise when bulls feed are not perceived by them. And it turns out that for some cunning bull, if he wants to feast on his prey in private, the direct calculation is to eat for a little more high tones- his fellow tribesmen (aka competitors) will not hear him and will not find him. This is of course a joke. But in the process of evolution, the most unexpected adaptations were developed, generated by the need to live in a community and depend on a predator on its prey, a weak individual on its stronger competitor, etc. And advantages, even small ones, in the methods of obtaining information (fine hearing, sense of smell, sharper vision, etc.) turned out to be a blessing for the species.
In the next chapter we will show that sound signals have such a great importance in the life of the fish kingdom, which was not even suspected until recently.
Water is the keeper of sounds .........................................................................................
9
How do fish hear?
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17
A language without words is a language of emotions...........................................................................................
29
"Mute" among fish? ........................................................ ........................................................ ...... 35
Fish “Esperanto” .................................................... ........................................................ ............. 37
Bite on the fish! ........................................................ ........................................................ .................... 43
Don't worry: the sharks are coming! ........................................................ ........................................ 48
About the “voices” of fish and what is meant by this
and what follows from this................................................... ........................................................ .......... 52
Fish signals associated with reproduction................................................................. ........................... 55
“Voices” of fish during defense and attack.................................................... ................................ 64
The Baron's Undeservedly Forgotten Discovery
Munchausen......................................................... ........................................................ .................... 74
“Table of ranks” in a school of fish .................................................... ........................................................ .. 77
Acoustic milestones on migration routes.................................................... ................................ 80
Swim bladder improves
seismograph................................................. ........................................................ ........................... 84
Acoustics or electricity? ........................................................ ........................................... 88
On the practical benefits of studying fish “voices”
and hearing...................................................................................................................................
97
“Excuse me, can’t you be more gentle with us..?” ........................................................ ................97
The fishermen advised the scientists; scientists move on................................................... ............... 104
Report from the depths of the joint.................................................... ........................................................ ..... 115
Acoustic mines and demolition fish.................................................. ........................ 120
Bioacoustics of fish in the reserve of bionics.................................................... ................................... 124
For the amateur underwater hunter
sounds ..................................................................................................................................
129
Recommended reading................................................... ........................................................ 143
Fish have neither an external ear nor an eardrum. Sound waves are transmitted directly through tissue. The labyrinth of fish also serves as an organ of balance. The lateral line allows the fish to navigate, feel the flow of water or the approach of various objects in the dark. The lateral line organs are located in a canal immersed in the skin, which communicates with the external environment through holes in the scales. The canal contains nerve endings.
The hearing organs of fish also perceive vibrations in the aquatic environment, but only higher frequency, harmonic or sound ones. They are structured more simply than other animals.
Fish have neither an outer nor a middle ear: they do without them due to the higher permeability of water to sound. There is only the membranous labyrinth, or inner ear, enclosed in the bony wall of the skull.
Fish hear, and very well, so the fisherman must maintain complete silence while fishing. By the way, this became known only recently. Some 35-40 years ago they thought that fish were deaf.
In terms of sensitivity, hearing and the lateral line come to the fore in winter. It should be noted here that external sound vibrations and noise penetrate through the ice and snow cover to a much lesser extent into the fish habitat. There is almost absolute silence in the water under the ice. And in such conditions, the fish relies more on its hearing. The organ of hearing and the lateral line help the fish to determine the places where bloodworms accumulate in the bottom soil by the vibrations of these larvae. If we also take into account that sound vibrations attenuate in water 3.5 thousand times slower than in air, it becomes clear that fish are able to detect the movements of bloodworms in the bottom soil at a considerable distance.
Having buried themselves in a layer of silt, the larvae strengthen the walls of the passages with hardening secretions of the salivary glands and make wave-like oscillatory movements with their bodies in them (Fig.), blowing and cleaning their home. From this, acoustic waves are emitted into the surrounding space, and they are perceived by the lateral line and hearing of the fish.
Thus, the more bloodworms there are in the bottom soil, the more acoustic waves emanate from it and the easier it is for fish to detect the larvae themselves.
Fish have ears! says Yulia Sapozhnikova, researcher at the ichthyology laboratory. Only they do not have an external ear, the same pinna that we are used to seeing in mammals.
Some fish do not have an ear, in which there would be auditory bones - the hammer, incus and stapes - also components of the human ear. But all fish have an inner ear, and it is designed in a very interesting way.
Fish ears are so small that they fit on tiny metal “tablets”, a dozen of which could easily fit in the palm of a human hand.
Gold plating is applied to various parts of the inner ear of the fish. These gold-plated fish ears are then examined under an electron microscope. Only gold plating allows a person to see the details of the inner ear of fish. You can even photograph them in a gold frame!
The pebble (otolith), under the influence of hydrodynamic and sound waves, makes oscillatory movements, and the finest sensory hairs catch them and transmit signals to the brain.
This is how the fish distinguishes sounds.
The ear pebble turned out to be a very interesting organ. For example, if you split it, you can see rings on the chip.
These are annual rings, just like those found on cut trees. Therefore, by the rings on the ear stone, like the rings on the scales, you can determine how old the fish is.
The organs of hearing and balance in fish are represented by the inner ear; they do not have an outer ear. The inner ear consists of three semicircular canals with ampoules, an oval sac and a round sac with a projection (lagena). Fish are the only vertebrates with two or three pairs of otoliths, or ear stones, which help maintain a certain position in space. Many fish have a connection between the inner ear and the swim bladder through a chain of special ossicles (Weberian apparatus of cyprinids, loaches and catfishes) or through the forward processes of the swim bladder reaching the auditory capsule (herring, anchovies, cod, many sea crucians, rock perches) .
Can fish hear?
The saying “dumb as a fish” has long lost its relevance from a scientific point of view. It has been proven that fish can not only make sounds themselves, but also hear them. For a long time there has been debate over whether fish hear. Now the answer of scientists is known and unambiguous - fish not only have the ability to hear and have the appropriate organs for this, but they themselves can also communicate with each other through sounds.
A little theory about the essence of sound
Physicists have long established that sound is nothing more than a chain of regularly repeating compression waves of a medium (air, liquid, solid). In other words, sounds in water are just as natural as on its surface. In water, sound waves, the speed of which is determined by the compression force, can propagate at different frequencies:
- most fish perceive sound frequencies in the range of 50-3000 Hz,
- vibrations and infrasound, which refer to low-frequency vibrations up to 16 Hz, are not perceived by all fish,
- are fish capable of perceiving ultrasonic waves whose frequency exceeds 20,000 Hz) - this question has not yet been fully studied, therefore, convincing evidence regarding the presence of such an ability in underwater inhabitants has not been obtained.
It is known that sound travels four times faster in water than in air or other gaseous media. This is the reason that fish receive sounds that enter the water from the outside in a distorted form. Compared to land dwellers, fish's hearing is not as acute. However, experiments by zoologists have revealed very Interesting Facts: in particular, some types of slaves can distinguish even halftones.
More about the sideline
Scientists consider this organ in fish to be one of the most ancient sensory formations. It can be considered universal, since it performs not one, but several functions at once, ensuring the normal functioning of fish.
The morphology of the lateral system is not the same in all fish species. There are options:
- The very location of the lateral line on the body of the fish may refer to a specific feature of the species,
- In addition, there are known species of fish with two or more lateral lines on both sides,
- In bony fish, the lateral line usually runs along the body. For some it is continuous, for others it is intermittent and looks like a dotted line,
- In some species, the lateral line canals are hidden inside the skin or run open along the surface.
In all other respects, the structure of this sensory organ in fish is identical and it functions in the same way in all types of fish.
This organ reacts not only to the compression of water, but also to other stimuli: electromagnetic, chemical. Main role Neuromasts, consisting of so-called hair cells, play a role in this. The very structure of the neuromasts is a capsule (mucous part), into which the actual hairs of the sensitive cells are immersed. Since the neuromasts themselves are closed, they are connected to the external environment through microholes in the scales. As we know, neuromasts can also be open. These are characteristic of those species of fish in which the lateral line canals extend onto the head.
In the course of numerous experiments conducted by ichthyologists in different countries it was established for certain that the lateral line perceives low-frequency vibrations, not only sound waves, but waves from the movement of other fish.
How hearing organs warn fish of danger
In the wild, as well as in a home aquarium, fish take adequate measures when they hear the most distant sounds of danger. While the storm in this area of the sea or ocean is still just beginning, the fish change their behavior ahead of time - some species sink to the bottom, where wave fluctuations are the smallest; others migrate to quiet locations.
Uncharacteristic fluctuations in water are regarded by the inhabitants of the seas as an approaching danger and they cannot help but react to it, since the instinct of self-preservation is characteristic of all life on our planet.
In rivers, the behavioral reactions of fish may be different. In particular, at the slightest disturbance in the water (from a boat, for example), the fish stop eating. This saves her from the risk of being hooked by a fisherman.
The hearing organ of fish is represented only by the inner ear and consists of a labyrinth, including the vestibule and three semicircular canals located in three perpendicular planes. The fluid inside the membranous labyrinth contains auditory pebbles (otoliths), the vibrations of which are perceived by the auditory nerve. Fish have neither an external ear nor an eardrum. Sound waves are transmitted directly through tissue. The labyrinth of fish also serves as an organ of balance. The lateral line allows the fish to navigate, feel the flow of water or the approach of various objects in the dark. The lateral line organs are located in a canal immersed in the skin, which communicates with the external environment through holes in the scales. The canal contains nerve endings. The hearing organs of fish also perceive vibrations in the aquatic environment, but only higher frequency, harmonic or sound ones. They are structured more simply than other animals. Fish have neither an outer nor a middle ear: they do without them due to the higher permeability of water to sound. There is only the membranous labyrinth, or inner ear, enclosed in the bony wall of the skull. Fish hear, and very well, so the fisherman must maintain complete silence while fishing. By the way, this became known only recently. Some 35-40 years ago they thought that fish were deaf. In terms of sensitivity, hearing and the lateral line come to the fore in winter. It should be noted here that external sound vibrations and noise penetrate through the ice and snow cover to a much lesser extent into the fish habitat. There is almost absolute silence in the water under the ice. And in such conditions, the fish relies more on its hearing. The organ of hearing and the lateral line help the fish to determine the places where bloodworms accumulate in the bottom soil by the vibrations of these larvae.
Do fish have hearing?
If we also take into account that sound vibrations attenuate in water 3.5 thousand times slower than in air, it becomes clear that fish are able to detect the movements of bloodworms in the bottom soil at a considerable distance. Having buried themselves in a layer of silt, the larvae strengthen the walls of the passages with hardening secretions of the salivary glands and make wave-like oscillatory movements with their bodies in them (Fig.), blowing and cleaning their home. From this, acoustic waves are emitted into the surrounding space, and they are perceived by the lateral line and hearing of the fish. Thus, the more bloodworms there are in the bottom soil, the more acoustic waves emanate from it and the easier it is for fish to detect the larvae themselves.
internally only
Section 2
HOW FISHES HEAR |
As you know, for a long time fish were considered deaf.
After scientists conducted experiments here and abroad using the method of conditioned reflexes (in particular, among the experimental subjects were crucian carp, perch, tench, ruffe and other freshwater fish), it was convincingly proven that fish hear, the boundaries of the hearing organ were also determined, its physiological functions and physical parameters.
Hearing, along with vision, is the most important of the senses of remote (non-contact) action; with its help, fish navigate their environment. Without knowledge of the hearing properties of fish, it is impossible to fully understand how the connection between individuals in a school is maintained, how fish relate to fishing gear, and what the relationship between predator and prey is. Progressive bionics requires a wealth of accumulated facts on the structure and functioning of the hearing organ in fish.
Observant and savvy recreational fishermen have long benefited from the ability of some fish to hear noise. This is how the method of catching catfish with a “shred” was born. A frog is also used in the nozzle; Trying to free itself, the frog, raking with its paws, creates a noise that is well known to the catfish, which often appears right there.
So the fish hear. Let's look at their hearing organ. In fish you cannot find what is called the external organ of hearing or ears. Why?
At the beginning of this book, we mentioned the physical properties of water as an acoustic medium transparent to sound. How useful would it be for the inhabitants of the seas and lakes to be able to prick up their ears, like an elk or a lynx, in order to catch a distant rustle and timely detect a sneaking enemy. But bad luck - it turns out that having ears is not economical for movement. Have you looked at the pike? Her entire chiseled body is adapted for rapid acceleration and throwing - nothing unnecessary that would make movement difficult.
Fish also do not have the so-called middle ear, which is characteristic of land animals. In terrestrial animals, the middle ear apparatus plays the role of a miniature and simply designed transceiver of sound vibrations, carrying out its work through the eardrum and auditory ossicles. These “parts” that make up the structure of the middle ear of land animals have a different purpose, a different structure, and a different name in fish. And not by chance. The outer and middle ear with its eardrum is not biologically justified under conditions of high pressures of a dense mass of water that quickly increase with depth. It is interesting to note that in aquatic mammals - cetaceans, whose ancestors left land and returned to water, the tympanic cavity has no exit to the outside, since the external auditory canal is either closed or blocked by an ear plug.
And yet fish have a hearing organ. Here is its diagram (see picture). Nature made sure that this very fragile, finely structured organ was sufficiently protected - by this she seemed to emphasize its importance. (And you and I have a particularly thick bone that protects our inner ear). Here is labyrinth 2. The hearing ability of fish is associated with it (semicircular canals - balance analyzers). Pay attention to the sections designated by numbers 1 and 3. These are the lagena and sacculus - auditory receivers, receptors that perceive sound waves. When, in one of the experiments, the lower part of the labyrinth - the sacculus and lagena - was removed from minnows with a developed food reflex to sound, they stopped responding to signals.
Irritation along the auditory nerves is transmitted to the auditory center located in the brain, where the as yet unknown processes of converting the received signal into images and the formation of a response occur.
There are two main types of auditory organs in fish: organs without connection with the swim bladder and organs of which the swim bladder is an integral part.
The swim bladder is connected to the inner ear using the Weberian apparatus - four pairs of movably articulated bones. And although fish do not have a middle ear, some of them (cyprinids, catfish, characinids, electric eels) have a substitute for it - a swim bladder plus a Weberian apparatus.
Until now, you knew that the swim bladder is a hydrostatic apparatus that regulates the specific gravity of the body (and also that the bladder is an essential component of a full-fledged crucian fish soup). But it is useful to know something more about this organ. Namely: the swim bladder acts as a receiver and transducer of sounds (similar to our eardrum). The vibration of its walls is transmitted through the Weber apparatus and is perceived by the fish’s ear as vibrations of a certain frequency and intensity. Acoustically, a swim bladder is essentially the same as an air chamber placed in water; hence the important acoustic properties of the swim bladder. Due to the differences in the physical properties of water and air, the acoustic receiver
such as a thin rubber bulb or swim bladder, filled with air and placed in water, when connected to the diaphragm of a microphone, it dramatically increases its sensitivity. The inner ear of a fish is the “microphone” that works in conjunction with the swim bladder. In practice, this means that although the water-air interface strongly reflects sounds, fish are still sensitive to voices and noise from the surface.
The well-known bream is very sensitive during the spawning period and is afraid of the slightest noise. In the old days, it was even forbidden to ring bells during bream spawning.
The swim bladder not only increases hearing sensitivity, but also expands the perceived frequency range of sounds. Depending on how many times sound vibrations are repeated in 1 second, the frequency of sound is measured: 1 vibration per second - 1 hertz. The ticking of a pocket watch can be heard in the frequency range from 1500 to 3000 hertz. For clear, intelligible speech on the telephone, a frequency range from 500 to 2000 hertz is sufficient. So we could talk to the minnow on the phone, because this fish responds to sounds in the frequency range from 40 to 6000 hertz. But if guppies “came” to the phone, they would only hear those sounds that lie in the band up to 1200 hertz. Guppies lack a swimbladder, and their hearing system does not perceive higher frequencies.
At the end of the last century, experimenters sometimes did not take into account the abilities various types fish perceive sounds in a limited frequency range and made erroneous conclusions about the lack of hearing in fish.
At first glance, it may seem that the capabilities of the fish’s auditory organ cannot be compared with the extremely sensitive human ear, capable of detecting sounds of negligible intensity and distinguishing sounds whose frequencies range from 20 to 20,000 hertz. Nevertheless, fish are perfectly oriented in their native elements, and sometimes limited frequency selectivity turns out to be advisable, because it allows one to isolate from the stream of noise only those sounds that turn out to be useful for the individual.
If a sound is characterized by any one frequency, we have a pure tone. A pure, unadulterated tone is obtained using a tuning fork or a sound generator. Most of the sounds around us contain a mixture of frequencies, a combination of tones and shades of tones.
A reliable sign of developed acute hearing is the ability to distinguish tones. The human ear is capable of distinguishing about half a million simple tones, varying in pitch and volume. What about the fish?
Minnows are able to distinguish sounds of different frequencies. Trained to a specific tone, they can remember that tone and respond to it one to nine months after training. Some individuals can remember up to five tones, for example, “do”, “re”, “mi”, “fa”, “sol”, and if the “food” tone during training was “re”, then the minnow is able to distinguish it from the neighboring one. a low tone "C" and a higher tone "E". Moreover, minnows in the frequency range 400-800 hertz are able to distinguish sounds that differ in pitch by half a tone. Suffice it to say that a piano keyboard, satisfying the most subtle human hearing, contains 12 semitones of an octave (a frequency ratio of two is called an octave in music). Well, perhaps minnows also have some musicality.
Compared to the “listening” minnow, the macropod is not musical. However, the macropod also distinguishes two tones if they are separated from each other by 1 1/3 octaves. We can mention the eel, which is remarkable not only because it goes to spawn distant seas, but also because it is able to distinguish sounds that differ in frequency by an octave. The above about the hearing acuity of fish and their ability to remember tones makes us re-read the lines of the famous Austrian scuba diver G. Hass in a new way: “At least three hundred large silvery star mackerel swam up in a solid mass and began to circle around the loudspeaker. They kept a distance of about three meters from me and swam as if in a big round dance. It is likely that the sounds of the waltz - it was Johann Strauss's "Southern Roses" - had nothing to do with this scene, and only curiosity, or at best sounds, attracted the animals. But the impression of the waltz of the fish was so complete that I later conveyed it in our film as I observed it myself.”
Let's now try to understand in more detail - what is the sensitivity of fish hearing?
We see two people talking in the distance, we see the facial expressions of each of them, gestures, but we do not hear their voices at all. The flow of sound energy flowing into the ear is so small that it does not cause auditory sensation.
In this case, hearing sensitivity can be assessed by the lowest intensity (loudness) of sound that the ear detects. It is by no means the same across the entire range of frequencies perceived by a given individual.
The highest sensitivity to sounds in humans is observed in the frequency range from 1000 to 4000 hertz.
In one of the experiments, the brook chub perceived the weakest sound at a frequency of 280 hertz. At a frequency of 2000 hertz, his auditory sensitivity was halved. In general, fish hear low sounds better.
Of course, hearing sensitivity is measured from some initial level, taken as the sensitivity threshold. Since a sound wave of sufficient intensity produces quite noticeable pressure, it was agreed to define the smallest threshold strength (or loudness) of sound in units of the pressure it exerts. Such a unit is an acoustic bar. The normal human ear begins to detect sound whose pressure exceeds 0.0002 bar. To understand how insignificant this value is, let us explain that the sound of a pocket watch pressed to the ear exerts a pressure on the eardrum that exceeds the threshold by 1000 times! In a very “quiet” room, the sound pressure level exceeds the threshold by 10 times. This means that our ear records a sound background that we sometimes consciously fail to appreciate. For comparison, note that the eardrum experiences pain when the pressure exceeds 1000 bar. We feel such a powerful sound when standing not far from a jet plane taking off.
We have given all these figures and examples of the sensitivity of human hearing only in order to compare them with the auditory sensitivity of fish. But it is no coincidence that they say that any comparison is lame.
Do fish have ears?
The aquatic environment and the structural features of the auditory organ of fish make noticeable adjustments to comparative measurements. However, under conditions of increased environmental pressure, the sensitivity of human hearing also noticeably decreases. Be that as it may, the dwarf catfish has a hearing sensitivity no worse than that of humans. This seems amazing, especially since fish do not have the organ of Corti in their inner ear - the most sensitive, subtle “device”, which in humans is the actual organ of hearing.
It's all like this: the fish hears the sound, the fish distinguishes one signal from another by frequency and intensity. But you should always remember that the hearing abilities of fish are not the same not only between species, but also among individuals of the same species. If we can still talk about some kind of “average” human ear, then in relation to the hearing of fish, no template whatsoever is applicable, because the peculiarities of the hearing of fish are the result of life in a specific environment. The question may arise: how does a fish find the source of sound? It is not enough to hear the signal, you need to focus on it. It is vitally important for crucian carp, which has reached a formidable danger signal - the sound of food excitement of the pike, to localize this sound.
Most fish studied are capable of localizing sounds in space at distances from sources approximately equal to the length of the sound wave; At long distances, fish usually lose the ability to determine the direction to the source of sound and make prowling, searching movements, which can be deciphered as an “attention” signal. This specificity of the action of the localization mechanism is explained by the independent operation of two receivers in fish: the ear and the lateral line. The fish's ear often works in combination with the swim bladder and perceives sound vibrations in a wide range of frequencies. The lateral line records the pressure and mechanical displacement of water particles. No matter how small the mechanical displacements of water particles caused by sound pressure are, they must be sufficient to be noted by living “seismographs” - sensitive cells of the lateral line. Apparently, the fish receives information about the location of the source of low-frequency sound in space by two indicators at once: the amount of displacement (lateral line) and the amount of pressure (ear). Special experiments were carried out to determine the ability of river perches to detect sources of underwater sounds emitted through a tape recorder and waterproof dynamic headphones. The previously recorded sounds of feeding were played into the water of the pool - the capture and grinding of food by perches. This kind of experiment in an aquarium is greatly complicated by the fact that multiple echoes from the walls of the pool seem to smear and muffle the main sound. A similar effect is observed in a spacious room with a low vaulted ceiling. Nevertheless, perches showed the ability to directionally detect the source of sound from a distance of up to two meters.
The method of food conditioned reflexes helped to establish in an aquarium that crucian carp and carp are also capable of determining the direction to the source of sound. In experiments in aquariums and in the sea, some marine fish (mackerel mackerel, roulena, mullet) detected the location of the sound source from a distance of 4-7 meters.
But the conditions under which experiments are carried out to determine this or that acoustic ability of fish do not yet give an idea of how sound signaling is carried out in fish in a natural environment where the ambient background noise is high. An audio signal carrying useful information only makes sense when it reaches the receiver in an undistorted form, and this circumstance does not require special explanation.
Experimental fish, including roach and river perch, kept in small schools in an aquarium, developed a conditioned food reflex. As you may have noticed, the food reflex appears in many experiments. The fact is that the feeding reflex is quickly developed in fish, and it is the most stable. Aquarists know this well. Who among them has not performed a simple experiment: feeding the fish with a portion of bloodworms, while tapping on the glass of the aquarium. After several repetitions, hearing a familiar knock, the fish rush together “to the table” - they have developed a feeding reflex to the conditioned signal.
In the above experiment, two types of conditioned food signals were given: a single-tone sound signal with a frequency of 500 hertz, rhythmically emitted through an earphone using a sound generator, and a noise “bouquet” consisting of sounds pre-recorded on a tape recorder that occur when individuals feed. To create noise interference, a stream of water was poured into the aquarium from a height. The background noise it created, as measurements showed, contained all frequencies of the sound spectrum. It was necessary to find out whether fish are able to isolate a food signal and respond to it under camouflage conditions.
It turned out that fish are able to isolate useful signals from noise. Moreover, the fish clearly recognized a monophonic sound, delivered rhythmically, even when a trickle of falling water “clogged” it.
Sounds of a noise nature (rustling, slurping, rustling, gurgling, hissing, etc.) are emitted by fish (like humans) only in cases where they exceed the level of surrounding noise.
This and other similar experiments prove the ability of fish hearing to isolate vital signals from a set of sounds and noises that are useless for an individual of a given species, which are present in abundance under natural conditions in any body of water in which there is life.
On several pages we examined the hearing capabilities of fish. Aquarium lovers, if they have simple and accessible instruments, which we will discuss in the corresponding chapter, could independently carry out some simple experiments: for example, determining the ability of fish to focus on a sound source when it has biological significance for them, or the ability of fish to emit such sounds against the background of other “useless” noise, or detection of the hearing limit of a particular type of fish, etc.
Much is still unknown, much needs to be understood about the design and operation hearing aid fish
The sounds made by cod and herring have been well studied, but their hearing has not been studied; in other fish it is just the opposite. The acoustic capabilities of representatives of the goby family have been more fully studied. So, one of them, the black goby, perceives sounds not exceeding a frequency of 800-900 hertz. Everything that goes beyond this frequency barrier does not “touch” the bull. His auditory capabilities allow him to perceive the hoarse, low grunt emitted by his opponent through the swim bladder; this grumbling in a certain situation can be deciphered as a threat signal. But high-frequency components of sounds that arise when bulls feed are not perceived by them. And it turns out that some cunning bull, if he wants to feast on his prey in private, has a direct plan to eat at slightly higher tones - his fellow tribesmen (aka competitors) will not hear him and will not find him. This is of course a joke. But in the process of evolution, the most unexpected adaptations were developed, generated by the need to live in a community and depend on a predator on its prey, a weak individual on its stronger competitor, etc. And advantages, even small ones, in the methods of obtaining information (fine hearing, sense of smell, sharper vision, etc.) turned out to be a blessing for the species.
In the next chapter we will show that sound signals have such a great importance in the life of the fish kingdom, which was not even suspected until recently.
Water is the keeper of sounds………………………………………………………………………………….. 9
How do fish hear? …………………………………………………………………………………………….. 17
A language without words is a language of emotions…………………………………………………………………………………. 29
"Mute" among fish? ……………………………………………………………………………………………. 35
Fish “Esperanto”……………………………………………………………………………………………………………. 37
Bite on the fish! ………………………………………………………………………………………………………… 43
Don't worry: the sharks are coming! ……………………………………………………………………………… 48
About the “voices” of fish and what is meant by this
and what follows from this………………………………………………………………………………………… 52
Fish signals associated with reproduction …………………………………………………………….. 55
“Voices” of fish during defense and attack……………………………………………………………….. 64
The Baron's Undeservedly Forgotten Discovery
Munchausen ………………………………………………………………………………………………………… 74
“Table of ranks” in a school of fish …………………………………………………………………………………. 77
Acoustic landmarks on migration routes …………………………………………………………………… 80
Swim bladder improves
seismograph……………………………………………………………………………………………………………. 84
Acoustics or electricity? ………………………………………………………………………………… 88
On the practical benefits of studying fish “voices”
and hearing…………………………………………………………………………………………………………….. 97
“Excuse me, can’t you be more gentle with us..?” ………………………………………………………97
The fishermen advised the scientists; scientists go further………………………………………………………. 104
Report from the depths of the school………………………………………………………………………………….. 115
Acoustic mines and demolition fish ………………………………………………………………………………… 120
Bioacoustics of fish in reserve for bionics…………………………………………………………………………………. 124
For the amateur underwater hunter
sounds……………………………………………………………………………………………………………. 129
Recommended reading………………………………………………………………………………….. 143
How do fish hear? Ear device
We do not find any fish ears, no ear holes. But this does not mean that the fish does not have an inner ear, because our outer ear itself does not sense sounds, but only helps the sound reach the real auditory organ - the inner ear, which is located in the thickness of the temporal cranial bone.
The corresponding organs in fish are also located in the skull, on the sides of the brain. Each of them looks like an irregular bubble filled with liquid (Fig. 19).
Sound can be transmitted to such an inner ear through the bones of the skull, and we can discover the possibility of such sound transmission from our own experience (with your ears tightly plugged, bring a pocket or wrist watch close to your face - and you will not hear it ticking; then put the watch on your teeth - ticking hours will be heard quite clearly).
However, it is hardly possible to doubt that the original and main function of the auditory vesicles, when they were formed in the ancient ancestors of all vertebrates, was the sensation vertical position and that, first of all, for an aquatic animal they were static organs, or organs of balance, quite similar to the statocysts of other free-swimming aquatic animals, starting with jellyfish.
Such is their importance vital meaning and for fish, which, according to Archimedes’ law, in the aquatic environment is practically “weightless” and cannot feel the force of gravity. But the fish senses every change in body position with auditory nerves going to its inner ear.
Its auditory vesicle is filled with liquid, in which tiny but weighty auditory ossicles lie: rolling along the bottom of the auditory vesicle, they give the fish the opportunity to constantly feel the vertical direction and move accordingly.
The question of whether fish hear has been debated for a long time. It has now been established that fish hear and make sounds themselves. Sound is a chain of regularly repeating compression waves of a gaseous, liquid or solid medium, i.e. in an aquatic environment, sound signals are as natural as on land. Compression waves in the aquatic environment can propagate at different frequencies. Low-frequency vibrations (vibration or infrasound) up to 16 Hz are not perceived by all fish. However, in some species, infrasound reception has been brought to perfection (sharks). The spectrum of sound frequencies perceived by most fish lies in the range of 50-3000 Hz. The ability of fish to perceive ultrasonic waves (over 20,000 Hz) has not yet been convincingly proven.
The speed of sound propagation in water is 4.5 times greater than in air. Therefore, sound signals from the shore reach the fish in a distorted form. The hearing acuity of fish is not as developed as that of land animals. Nevertheless, in some species of fish, quite decent musical abilities have been observed in experiments. For example, a minnow distinguishes 1/2 tone at 400-800 Hz. The capabilities of other fish species are more modest. Thus, guppies and eels differentiate two that differ by 1/2-1/4 octaves. There are also species that are completely musically mediocre (bladderless and labyrinthine fish).
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Rice. 2.18. The connection of the swim bladder with the inner ear in different species of fish: a- Atlantic herring; b - cod; c - carp; 1 - outgrowths of the swim bladder; 2- inner ear; 3 - brain: 4 and 5 bones of the Weberian apparatus; common endolymphatic duct
Hearing acuity is determined by the morphology of the acoustic-lateral system, which, in addition to the lateral line and its derivatives, includes the inner ear, the swim bladder and the Weber’s apparatus (Fig. 2.18).
Both in the labyrinth and in the lateral line, the sensory cells are the so-called hairy cells. Displacement of the hair of the sensitive cell both in the labyrinth and in the lateral line leads to the same result - the generation of a nerve impulse entering the same acoustic-lateral center of the medulla oblongata. However, these organs also receive other signals (gravitational field, electromagnetic and hydrodynamic fields, as well as mechanical and chemical stimuli).
The hearing apparatus of fish is represented by the labyrinth, swim bladder (in bladder fish), Weber's apparatus and the lateral line system. Labyrinth. A paired formation - the labyrinth, or inner ear of fish (Fig. 2.19), performs the function of an organ of balance and hearing. Auditory receptors are present in large numbers in the two lower chambers of the labyrinth - the lagena and the utriculus. The hairs of the auditory receptors are very sensitive to the movement of endolymph in the labyrinth. A change in the position of the fish's body in any plane leads to the movement of endolymph in at least one of the semicircular canals, which irritates the hairs.
In the endolymph of the saccule, utriculus and lagena there are otoliths (pebbles), which increase the sensitivity of the inner ear.
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Rice. 2.19. Fish labyrinth: 1-round pouch (lagena); 2-ampule (utriculus); 3-saccula; 4-channel labyrinth; 5- location of otoliths
There are a total of three on each side. They differ not only in location, but also in size. The largest otolith (pebble) is located in a round sac - lagena.
On the otoliths of fish, annual rings are clearly visible, by which the age of some fish species is determined. They also provide an assessment of the effectiveness of the fish's maneuver. With longitudinal, vertical, lateral and rotational movements of the fish's body, some displacement of the otoliths occurs and irritation of the sensitive hairs occurs, which, in turn, creates a corresponding afferent flow. They (otoliths) are also responsible for the reception of the gravitational field and the assessment of the degree of acceleration of the fish during throws.
The endolymphatic duct departs from the labyrinth (see Fig. 2.18.6), which is closed in bony fishes, and open in cartilaginous fishes and communicates with the external environment. Weber apparatus. It is represented by three pairs of movably connected bones, which are called stapes (in contact with the labyrinth), incus and maleus (this bone is connected to the swim bladder). The bones of the Weberian apparatus are the result of the evolutionary transformation of the first trunk vertebrae (Fig. 2.20, 2.21).
With the help of the Weberian apparatus, the labyrinth is in contact with the swim bladder in all bladder fish. In other words, the Weber apparatus provides communication between the central structures of the sensory system and the periphery that perceives sound.
Fig.2.20. Structure of the Weberian apparatus:
1- perilymphatic duct; 2, 4, 6, 8- ligaments; 3 - stapes; 5- incus; 7- maleus; 8 - swim bladder (vertebrae are indicated by Roman numerals)
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Rice. 2.21. General diagram of the structure of the hearing organ in fish:
1 - brain; 2 - utriculus; 3 - saccula; 4- connecting channel; 5 - lagena; 6- perilymphatic duct; 7-steps; 8- incus; 9-maleus; 10- swim bladder
Swim bladder. It is a good resonating device, a kind of amplifier of medium and low frequency vibrations of the medium. A sound wave from the outside leads to vibrations of the wall of the swim bladder, which, in turn, lead to a displacement of the chain of bones of the Weberian apparatus. The first pair of ossicles of the Weberian apparatus presses on the membrane of the labyrinth, causing displacement of the endolymph and otoliths. Thus, if we draw an analogy with higher terrestrial animals, the Weberian apparatus in fish performs the function of the middle ear.
However, not all fish have a swim bladder and Weberian apparatus. In this case, the fish show low sensitivity to sound. In bladderless fish, the auditory function of the swim bladder is partially compensated by the air cavities associated with the labyrinth and the high sensitivity of the lateral line organs to sound stimuli (water compression waves).
Side line. It is a very ancient sensory formation, which, even in evolutionarily young groups of fish, simultaneously performs several functions. Taking into account the exceptional importance of this organ for fish, let us dwell in more detail on its morphofunctional characteristics. Different ecological types of fish exhibit different variations of the lateral system. The location of the lateral line on the body of fish is often a species-specific feature. There are species of fish that have more than one lateral line. For example, the greenling has four lateral lines on each side, hence
This is where its second name comes from - “eight-line chir”. In most bony fish, the lateral line stretches along the body (without interruption or interruption in some places), reaches the head, forming a complex system of canals. The lateral line canals are located either inside the skin (Fig. 2.22) or openly on its surface.
An example of an open surface arrangement of neuromasts, the structural units of the lateral line, is the lateral line of the minnow. Despite the obvious diversity in the morphology of the lateral system, it should be emphasized that the observed differences concern only the macrostructure of this sensory formation. The organ's receptor apparatus itself (the chain of neuromasts) is surprisingly the same in all fish, both morphologically and functionally.
The lateral line system responds to compression waves of the aquatic environment, flow currents, chemical stimuli and electromagnetic fields with the help of neuromasts - structures that unite several hair cells (Fig. 2.23).
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Rice. 2.22. Fish lateral line channel
The neuromast consists of a mucous-gelatinous part - a capsule, into which the hairs of sensitive cells are immersed. Closed neuromasts communicate with the external environment through small holes that pierce the scales.
Open neuromasts are characteristic of the canals of the lateral system extending onto the head of the fish (see Fig. 2.23, a).
Channel neuromasts stretch from head to tail along the sides of the body, usually in one row (fishes of the family Hexagramidae have six rows or more). The term “lateral line” in common usage refers specifically to canal neuromasts. However, neuromasts are also described in fish, separated from the canal part and looking like independent organs.
Channel and free neuromasts, located in different parts of the fish’s body, and the labyrinth do not duplicate, but functionally complement each other. It is believed that the sacculus and lagena of the inner ear provide the sound sensitivity of fish from a great distance, and the lateral system makes it possible to localize the sound source (though already close to the sound source).
2.23. The structure of the neuromastaryba: a - open; b - channel
Waves arising on the surface of the water have a noticeable influence on the activity of fish and the nature of their behavior. The causes of this physical phenomenon are many factors: the movement of large objects (large fish, birds, animals), wind, tides, earthquakes. Excitement serves as an important channel for informing aquatic animals about events both in the body of water and beyond. Moreover, the disturbance of the reservoir is perceived by both pelagic and bottom fish. The reaction to surface waves on the part of fish is of two types: the fish sinks to greater depths or moves to another part of the reservoir. The stimulus acting on the body of the fish during the period of disturbance of the reservoir is the movement of water relative to the body of the fish. The movement of water when it is agitated is sensed by the acoustic-lateral system, and the sensitivity of the lateral line to waves is extremely high. Thus, for afferentation to occur from the lateral line, a displacement of the cupula by 0.1 μm is sufficient. At the same time, the fish is able to very accurately localize both the source of wave formation and the direction of wave propagation. The spatial diagram of fish sensitivity is species-specific (Fig. 2.26).
In the experiments, an artificial wave generator was used as a very strong stimulus. When its location changed, the fish unmistakably found the source of disturbance. The response to the wave source consists of two phases.
The first phase - the freezing phase - is the result of an indicative reaction (innate exploratory reflex). The duration of this phase is determined by many factors, the most significant of which are the height of the wave and the depth of the fish's dive. For cyprinid fish (carp, crucian carp, roach), with a wave height of 2-12 mm and fish immersion of 20-140 mm, the orientation reflex took 200-250 ms.
The second phase - the movement phase - a conditioned reflex reaction is developed in fish quite quickly. For intact fish, from two to six reinforcements are sufficient for its occurrence; in blinded fish, after six combinations of wave formation of food reinforcement, a stable search food-procuring reflex was developed.
Small pelagic planktivores are more sensitive to surface waves, while large bottom-dwelling fish are less sensitive. Thus, blinded verkhovkas with a wave height of only 1-3 mm demonstrated an indicative reaction after the first presentation of the stimulus. Marine bottom fish are characterized by sensitivity to strong waves on the sea surface. At a depth of 500 m, their lateral line is excited when the wave height reaches 3 m and length 100 m. As a rule, waves on the surface of the sea generate rolling motion. Therefore, during waves, not only the lateral line of the fish becomes excited, but also its labyrinth. The results of experiments showed that the semicircular canals of the labyrinth respond to rotational movements in which water currents involve the body of the fish. The utriculus senses the linear acceleration that occurs during the pumping process. During a storm, the behavior of both solitary and schooling fish changes. During a weak storm, pelagic species in the coastal zone descend to the bottom layers. When the waves are strong, fish migrate to the open sea and go to greater depths, where the influence of waves is less noticeable. It is obvious that strong excitement is assessed by fish as an unfavorable or even dangerous factor. It suppresses feeding behavior and forces fish to migrate. Similar changes in feeding behavior are also observed in fish species living in inland waters. Fishermen know that when the sea is rough, the fish stop biting.
Thus, the body of water in which the fish lives is a source of various information transmitted through several channels. Such awareness of fish about fluctuations in the external environment allows it to respond to them in a timely and adequate manner with locomotor reactions and changes in vegetative functions.
Fish signals. It is obvious that fish themselves are a source of various signals. They produce sounds in the frequency range from 20 Hz to 12 kHz, leave a chemical trace (pheromones, kairomones), and have their own electric and hydrodynamic fields. Acoustic and hydrodynamic fields of fish are created in various ways.
The sounds produced by fish are quite varied, but due to the low pressure they can only be recorded using special highly sensitive equipment. The mechanism of sound wave formation in different fish species may be different (Table 2.5).
Fish sounds are species specific. In addition, the nature of the sound depends on the age of the fish and its physiological state. The sounds coming from the school and from individual fish are also clearly distinguishable. For example, the sounds made by bream resemble wheezing. The sound pattern of a school of herring is associated with squeaking. The Black Sea gurnard makes sounds reminiscent of the clucking of a hen. The freshwater drummer identifies itself by drumming. Roaches, loaches, and scale insects emit squeaks that are perceptible to the naked ear.
It is still difficult to unambiguously characterize the biological significance of the sounds made by fish. Some of them are background noise. Within populations, schools, and also between sexual partners, sounds made by fish can also perform a communicative function.
Noise direction finding is successfully used in industrial fishing.
Do fish have ears?
The excess of the sound background of fish over ambient noise is no more than 15 dB. The background noise of a ship can be ten times greater than the soundscape of a fish. Therefore, fish bearing is only possible from those vessels that can operate in “silence” mode, that is, with the engines turned off.
Thus, the well-known expression “dumb as a fish” is clearly not true. All fish have a perfect sound reception apparatus. In addition, fish are sources of acoustic and hydrodynamic fields, which they actively use to communicate within the school, detect prey, warn relatives about possible danger, and other purposes.
Any sound source located on the substrate, in addition to emitting classical sound waves propagating in water or air, dissipates part of the energy in the form of various types of vibrations propagating in the substrate and along its surface.
Under auditory system we understand a receptor system capable of perceiving one or another component of sound study, localizing and assessing the nature of the source, creating the prerequisites for the formation of specific behavioral reactions of the body.
The auditory function in fish is carried out, in addition to the main organ of hearing, by the lateral line, the swim bladder, and also specific nerve endings.
The hearing organs of fish developed in an aquatic environment, which conducts sound 4 times faster and at long distances than the atmosphere. The range of sound perception in fish is much wider than in many land animals and people.
Hearing plays a very important role in the life of fish, especially fish that live in muddy water. In the lateral line of the fish, formations were discovered that record acoustic and other water vibrations.
The human auditory analyzer perceives vibrations with a frequency from 16 to 20,000 Hz. Sounds with a frequency below Hz are referred to as infrasounds, and sounds above 20,000 Hz are referred to as ultrasounds. The best perception of sound vibrations is observed in the range from 1000 to 4000 Hz. The spectrum of sound frequencies perceived by fish is significantly reduced compared to humans. So, for example, crucian carp perceives sounds in range 4 (31-21760 Hz, dwarf catfish -60-1600 Hz, shark 500-2500 Hz.
The hearing organs of fish have the ability to adapt to environmental factors, in particular, constant or monotonous and frequently repeated noise, for example the operation of a dredge; the fish quickly gets used to it and is not afraid of its noise. Also, the noise of a passing steamship, train, and even people swimming fairly close to the fishing site does not scare away the fish. The fish's fear is very short-lived. The impact of the spinner on the water, if it is made without much noise, not only does not frighten the predator, but perhaps alerts it in anticipation of the appearance of something edible for it. Fish can perceive individual sounds if they cause vibrations in the aquatic environment. Due to the density of water, sound waves are well transmitted through the bones of the skull and are perceived by the hearing organs of the fish. Pisces can hear the footsteps of a person walking along the shore, the ringing of a bell, or a gunshot.
Anatomically, like all vertebrates, the main organ of hearing - the ear - is a paired organ and forms a single whole with the organ of balance. The only difference is that fish do not have ears and eardrums, since they live in a different environment. The organ of hearing and the labyrinth in fish is at the same time an organ of balance; it is located in the back of the skull, inside the cartilaginous or bone chamber, and consists of upper and lower sacs in which otoliths (pebbles) are located.
The hearing organ of fish is represented only by the inner ear and consists of a labyrinth. The inner ear is a paired acoustic organ. In cartilaginous fish, it consists of a membranous labyrinth enclosed in a cartilaginous auditory capsule - a lateral extension of the cartilaginous skull behind the orbit. The labyrinth is represented by three membranous semicircular canals and three otolithic organs - the utriculus, sacculus and lagena (Fig. 91,92,93). The labyrinth is divided into two parts: the upper part, which includes the semicircular canals and utriculus, and the lower part, the sacculus and lagena. The three curved tubes of the semicircular canals lie in three mutually perpendicular planes and their ends open into the vestibule or membranous sac. It is divided into two parts - the upper oval sac and the larger lower - round sac, from which a small outgrowth extends - the lagena.
The cavity of the membranous labyrinth is filled with endolymph, in which small crystals are suspended otoconia. The cavity of the round sac usually contains larger calcareous formations otoliths consisting of calcium compounds. Vibrations that are perceived by the auditory nerve. The endings of the auditory nerve approach individual areas of the membranous labyrinth, covered with sensory epithelium - auditory spots and auditory ridges. Sound waves are transmitted directly through vibration-sensing tissues, which are perceived by the auditory nerve.
The semicircular canals are located in three mutually perpendicular planes. Each semicircular canal flows into the utriculus at two ends, one of which expands into the ampulla. There are elevations called auditory maculae, where clusters of sensitive hair cells are located. The finest hairs of these cells are connected by a gelatinous substance, forming a cupula. The endings of the VIII pair of cranial nerves approach the hair cells.
The utriculus of bony fish contains one large otolith. Otoliths are also located in the lagena and sacculus. The sacculus otolith is used to determine the age of fish. The sacculus of cartilaginous fish communicates with the external environment through a membranous outgrowth; in bony fishes, a similar outgrowth of the sacculus ends blindly.
The work of Dinkgraaf and Frisch confirmed that auditory function depends on the lower part of the labyrinth - the sacculus and lagena.
The labyrinth is connected to the swim bladder by a chain of Weberian ossicles (cyprinids, common catfishes, characins, gymnothids), and fish are able to perceive high-pitched sound tones. With the help of the swim bladder, high-frequency sounds are transformed into low-frequency vibrations (displacements), which are perceived by receptor cells. In some fish that do not have a swim bladder, this function is performed by air cavities associated with the inner ear.
Fig.93. Inner ear or labyrinth of fish:
a- hagfish; b - sharks; c - bony fish;
1 - posterior crista; 2-crista horizontal channel; 3- anterior crista;
4-endolymphatic duct; 5 - macula of the sacculus, 6 - macula of the utriculus; 7 - macula lagena; 8 - common pedicle of semicircular canals
Pisces also have an amazing “device” - a signal analyzer. Thanks to this organ, fish are able to isolate from all the chaos of sounds and vibrational manifestations around them the signals that are necessary and important for them, even those weak ones that are at the stage of emerging or on the verge of fading.
Fish are able to amplify these weak signals and then perceive them with analyzing formations.
The swim bladder is believed to act as a resonator and transducer of sound waves, which increases hearing acuity. It also performs a sound-producing function. Fish widely use sound signaling; they are capable of both perceiving and emitting sounds in a wide range of frequencies. Infrasonic vibrations are well perceived by fish. Frequencies equal to 4-6 hertz have a detrimental effect on living organisms, since these vibrations resonate with the vibrations of the body itself or individual organs and destroy them. It is possible that fish react to the approach of inclement weather by perceiving low-frequency acoustic vibrations emanating from approaching cyclones.
Pisces are able to “predict” weather changes long before they occur; fish detect these changes by the difference in the strength of sounds, and possibly by the level of interference for the passage of waves of a certain range.
12.3 The mechanism of body balance in fish. In bony fishes, the utriculus is the main receptor for body position. The otoliths are connected with the hairs of the sensitive epithelium using a gelatinous mass. When the head is positioned with the crown up, the otoliths press on the hairs; when the head is positioned down, they hang on the hairs; when the head is positioned sideways, there is a different degree of tension on the hairs. With the help of otoliths, the fish takes the correct position of the head (vertex up), and therefore the body (back up). To maintain correct body position, information coming from visual analyzers is also important.
Frisch found that when the upper part of the labyrinth (the utriculus and semicircular canals) is removed, the balance of the minnows is disturbed; the fish lie on their sides, bellies, or backs at the bottom of the aquarium. When swimming, they also adopt different body positions. Sighted fish quickly restore the correct position, but blind fish cannot restore their balance. Thus, the semicircular canals are of great importance in maintaining balance, in addition, with the help of these canals, changes in the speed of movement or rotation are perceived.
At the beginning of the movement or when it accelerates, the endolymph lags somewhat behind the movement of the head and the hairs of the sensitive cells deviate in the direction opposite to the movement. In this case, the endings of the vestibular nerve are irritated. When movement stops or slows down, the endolymph of the semicircular canals continues to move by inertia and deflects the hairs of sensitive cells along the way.
Studying functional value various departments labyrinth for the perception of sound vibrations was carried out using a study of fish behavior based on the development of conditioned reflexes, as well as using electrophysiological methods.
In 1910, Pieper discovered the appearance of action currents during irritation lower parts labyrinth - sacculus of freshly killed fish and the absence of such in case of irritation of the utriculus and semicircular canals.
Later, Frolov experimentally confirmed the perception of sound vibrations by fish, conducting experiments on cod, using a conditioned reflex technique. Frisch developed conditioned reflexes to whistling in dwarf catfish. Stettee. in catfish, minnows and loaches, he developed conditioned reflexes to certain sounds, reinforcing them with meat crumbs, and also caused inhibition of the food reaction to other sounds by hitting the fish with a glass rod.
Local sensitivity organs of fish. The ability of fish to echolocation is carried out not by the hearing organs, but by an independent organ - the location sense organ. Echolocation is the second type of hearing. In the lateral line of fish there is a radar and sonar - components of the location organ.
Fish use electrolocation, echolocation, and even thermolocation for their life activities. Electrolocation is often called the sixth sense organ of fish. Electrolocation is well developed in dolphins and bats. These animals use ultrasonic pulses with a frequency of 60,000-100,000 hertz, the duration of the signal sent is 0.0001 seconds, the interval between pulses is 0.02 seconds. This time is required for the brain to analyze the information received and form a specific response from the body. For fish this time is slightly shorter. During electrolocation, where the speed of the sent signal is 300,000 km/s, the animal does not have time to analyze the reflected signal; the sent signal will be reflected and perceived at almost the same time.
Freshwater fish cannot use ultrasound for location. To do this, fish must constantly move, and fish need to rest for a significant period of time. Dolphins are on the move around the clock; their left and right half of their brain rests alternately. Fish use wide-range low-frequency waves for location. It is believed that these waves serve fish for communication purposes.
Hydroacoustic studies have shown that fish are too “chatty” for an unreasonable creature; they produce too many sounds, and “conversations” are conducted at frequencies that are beyond the normal range of perception by their primary organ of hearing, i.e. their signals are more appropriate as location signals sent by fish radars. Low-frequency waves are poorly reflected from small objects, are less absorbed by water, are heard over long distances, propagate evenly in all directions from the sound source, their use for location gives fish the opportunity to panoramic “seeing and hearing” the surrounding space.
12.5 CHEMORECEPTION The relationship of fish with the external environment is combined into two groups of factors: abiotic and biotic. The physical and chemical properties of water that affect fish are called abiotic factors.
Animal perception of chemical substances using receptors is one of the forms of organisms’ response to the influence of the external environment. In aquatic animals, specialized receptors come into contact with substances in a dissolved state, therefore, the clear division characteristic of terrestrial animals into olfactory receptors, which perceive volatile substances, and taste receptors, which perceive substances in a solid and liquid state, does not appear in aquatic animals. However, morphologically and functionally, the olfactory organs in fish are quite well separated. Based on the lack of specificity in the functioning, localization and connection with nerve centers, it is customary to combine taste and the general chemical sense with the concept of “chemical analyzer”, or “non-olfactory chemoreception”.
OLFACTORY ORGAN belongs to the group of chemical receptors. The olfactory organs of fish are located in the nostrils located in front of each eye, the shape and size of which varies depending on the environment. They are simple pits with a mucous membrane, penetrated by branching nerves leading to a blind sac with sensitive cells coming from the olfactory lobe of the brain.
In most fish, each of the nostrils is divided by a septum into autonomous anterior and posterior nasal openings. In some cases, the nasal openings are single. In ontogenesis, the nasal openings of all fish are initially single, i.e. are not divided by a septum into the anterior and posterior nostrils, which are separated only by more late stages development.
The location of the nostrils in different species of fish depends on their lifestyle and the development of other senses. In fish with well-developed vision, the nasal openings are located on the upper side of the head between the eye and the end of the snout. In Selakhshe, the nostrils are located on the lower side and close to the mouth opening.
The relative size of the nostrils is closely related to the speed of movement of the fish. In fish that swim slowly, the nostrils are comparatively larger, and the septum between the anterior and posterior nasal openings looks like a vertical shield that directs water to the olfactory capsule. In fast fish, the nasal openings are extremely small, since at high speeds of the oncoming flowing skate, the water in the nasal capsule is washed off quite quickly through the relatively small openings of the anterior nostrils. In benthic fish, in which the role of smell is in common system reception is very significant, the anterior nasal openings extend in the form of tubes and approach the oral fissure or even hang down from the upper jaw, this is the case in Typhleotris, Anguilla, Mnreana, etc.
Odorous substances dissolved in water enter the mucous membrane of the olfactory area, irritate the endings of the olfactory nerves, from here the signals enter the brain.
Through the sense of smell, fish receive information about changes in the external environment, distinguish food, find their school, partners during spawning, detect predators, and calculate prey. On the skin of some species of fish there are cells that, when the skin is wounded, release a “fear substance” into the water, which is a signal of danger to other fish. Pisces actively use chemical information to give alarm signals, warn of danger, and attract individuals of the opposite sex. This organ is especially important for fish living in turbid waters, where, along with tactile and sound information, fish actively use and olfactory system. The sense of smell has a great influence on the functioning of many organs and systems of the body, toning or inhibiting them. There are known groups of substances that have a positive (attractant) or negative (repellent) effect on fish. The sense of smell is closely connected with other senses: taste, vision and balance.
At different times of the year, the olfactory sensations of fish are not the same; they become more intense in spring and summer, especially in warm weather.
Nocturnal fish (eel, burbot, catfish) have a highly developed sense of smell. The olfactory cells of these fish are capable of reacting to hundredths of concentrations of attractants and repellents.
Fish are able to sense a dilution of bloodworm extract in a ratio of one to a billion; crucian carp sense a similar concentration of nitrobenzene; higher concentrations are less attractive to fish. Amino acids serve as stimulants for the olfactory epithelium; some of them or their mixtures have a signaling value for fish. For example, an eel finds a mollusk by the complex it secretes, consisting of 7 amino acids. Vertebrates rely on a mixture of basic odors: musky, camphor, minty, ethereal, floral, pungent and rotten.
Olfactory receptors in fish, like other vertebrates, are paired and located on the front of the head. Only in cyclostomes are unpaired. Olfactory receptors are located on the blind recess - the nostril, the bottom of which is lined with olfactory epithelium located on the surface of the folds. The folds, diverging radially from the center, form an olfactory rosette.
U different fish olfactory cells are located on the folds in different ways: in a continuous layer, sparsely, on ridges or in a recess. A stream of water carrying odorant molecules enters the receptor through the anterior opening, often separated from the posterior exit opening only by a fold of skin. However, in some fish the entrance and exit holes are noticeably separated and are far apart. The anterior (entrance) openings of a number of fish (eel, burbot) are located close to the end of the snout and are equipped with skin tubes . It is believed that this sign indicates the significant role of smell in the search for food objects. The movement of water in the olfactory fossa can be created either by the movement of cilia on the surface of the lining, or by contraction and relaxation of the walls of special cavities - ampoules, or as a result of the movement of the fish itself.
Olfactory receptor cells, which have a bipolar shape, belong to the category of primary receptors, i.e., they themselves regenerate impulses containing information about the stimulus and transmit them along processes to the nerve centers. The peripheral process of the olfactory cells is directed to the surface of the receptor layer and ends in an extension - a club, at the apical end of which there is a tuft of hairs or microvilli. The hairs penetrate the mucus layer on the surface of the epithelium and are capable of movement.
The olfactory cells are surrounded by supporting cells, which contain oval nuclei and numerous granules of varying sizes. Basal cells that do not contain secretory granules are also located here. The central processes of receptor cells, which do not have a myelin sheath, having passed the basement membrane of the epithelium, form bundles of up to several hundred fibers, surrounded by the Schwann cell mesaxon, and the body of one cell can cover many bundles. The bundles merge into trunks, forming the olfactory nerve, which connects to the olfactory bulb.
The structure of the olfactory lining is similar in all vertebrates (Fig. 95), which indicates a similarity in the mechanism of contact reception. However, this mechanism itself is not yet entirely clear. One of them connects the ability to recognize odors, i.e., molecules of odorous substances, with the selective specificity of individual odor receptors. This is Eimour's stereochemical hypothesis. according to which, there are seven types of active sites on olfactory cells, and the molecules of substances with similar odors have the same shape of active parts that fit into the active points of the receptor, like a “key” to a lock. Other hypotheses link the ability to distinguish odors with differences in the distribution of substances adsorbed by the mucus of the olfactory lining over its surface. A number of researchers believe that odor recognition is provided by these two mechanisms, complementing each other.
The leading role in olfactory reception belongs to the hairs and club of the olfactory cell, which ensure the specific interaction of odorant molecules with the cell membrane and the translation of the interaction effect into the form of electrical potential. As already mentioned, the axons of the olfactory receptor cells form the olfactory nerve, which enters the olfactory bulb, which is the primary center of the olfactory receptor.
The olfactory bulb, according to A. A. Zavarzin, belongs to the screen structures. It is characterized by the arrangement of elements in the form of successive layers, and the nerve elements are interconnected not only within the layer, but also between the layers. There are usually three such layers: a layer of olfactory glomeruli with interglomerular cells, a layer of secondary neurons with mitral and brush cells, and a granular layer.
Information is transmitted to the higher olfactory centers in fish by secondary neurons and cells of the granular layer. The outer part of the olfactory bulb consists of fibers of the olfactory nerve, the contact of which with the dendrites of secondary neurons occurs in the olfactory glomeruli, where branching of both endings is observed. Several hundred fibers of the olfactory nerve converge in one olfactory glomerulus. The layers of the olfactory bulb are usually located concentrically, but in some fish species (pike), they lie successively in a rostrocaudal direction.
The olfactory bulbs of fish are anatomically well separated and are of two types: sessile, adjacent to the forebrain; stalked, located immediately behind the receptors (very short olfactory nerves).
In codfish, the olfactory bulbs are connected to the forebrain by long olfactory tracts, which are represented by the medial and lateral bundles, ending in the forebrain nuclei.
The sense of smell as a way of obtaining information about the surrounding world is very significant for fish. According to the degree of development of the sense of smell, fish, like other animals, are usually divided into macrosmatics and microsmatics. This division is associated with a different breadth of the spectrum of perceived odors.
U makresmatik The olfactory organs are capable of perceiving a large number of different odors, i.e. they use the sense of smell in more diverse situations.
Micromatics They usually perceive a small number of odors - mainly from individuals of their own species and sexual partners. A typical representative of macrosmatics is the common eel, while microsmatics are pike and three-spined stickleback. To perceive a smell, sometimes, apparently, it is enough for a few molecules of a substance to hit the olfactory receptor.
The sense of smell can play a guiding role in the search for food, especially in nocturnal and crepuscular predators such as eels. With the help of smell, fish can perceive school partners and find individuals of the opposite sex during the breeding season. For example, a minnow can distinguish a partner among individuals of its own species. Fish of one species are able to perceive chemical compounds released by the skin of other fish when wounded.
A study of the migrations of anadromous salmon has shown that at the stage of entering spawning rivers, they look for exactly the river where they themselves hatched, guided by the smell of water imprinted in memory at the juvenile stage (Fig. 96). The sources of the smell appear to be fish species that permanently inhabit the river. This ability has been used to direct migrating breeders to a specific site. Juvenile coho salmon were kept in a morpholine solution with a concentration of 0~5 M, and then, after they returned to their native river during the spawning period, they were attracted by the same solution to a certain place in the reservoir.
Rice. 96. Biocurrents of the olfactory brain of salmon during irrigation of the olfactory pits; 1, 2 - distilled water; 3 - water from the native river; 4, 5, 6 - water from foreign lakes.
Fish have a sense of smell, which is more developed in non-predatory fish. Pike, for example, do not use their sense of smell when searching for food. When it quickly rushes for prey, smell cannot play a significant role. Another predator - perch, when moving in search of food, usually swims quietly, picking up all kinds of larvae from the bottom; in this case, it uses the sense of smell as an organ that leads to food.
Organ of taste Almost all fish have a taste sensation that is transmitted to most of them through the lips and mouth. Therefore, the fish does not always swallow the captured food, especially if it is not to its taste.
Taste is a sensation that occurs when food and some non-food substances act on the taste organ. The organ of taste is closely related to the organ of smell and belongs to the group of chemical receptors. Taste sensations in fish appear when sensitive, tactile cells are irritated - taste buds or so-called taste buds, bulbs located in the oral cavity in the form of microscopic taste cells, on the antennae, over the entire surface of the body, especially on skin outgrowths. (Fig.97)
The main perceptions of taste are four components: sour, sweet, salty and bitter. The remaining types of taste are combinations of these four sensations, and taste sensations in fish can only be caused by substances dissolved in water.
Minimum perceptible difference in the concentration of substance solutions difference threshold- gradually worsens when moving from weak to stronger concentrations. For example, a one percent sugar solution has an almost maximally sweet taste, and a further increase in its concentration does not change the taste sensation.
The appearance of taste sensations can be caused by the action of inadequate stimuli on the receptor, for example, direct electric current. With prolonged contact of any substance with the organ of taste, its perception gradually becomes dulled; in the end, this substance will seem completely tasteless to the fish; adaptation occurs.
The taste analyzer can also influence some reactions of the body, activity internal organs. It has been established that fish react to almost all tasteful substances and at the same time have an amazingly subtle taste. Positive or negative reactions of fish are determined by their lifestyle and, above all, the nature of their diet. Positive reactions for sugar are characteristic of animals eating plant and mixed foods. The feeling of bitterness in most living beings is caused by negative reaction, but not those that feed on insects.
Fig.97. The location of taste buds on the body of the catfish is shown by dots. Each dot represents 100 taste buds
The mechanism of taste perception. The four basic taste sensations - sweet, bitter, sour and salty - are perceived through the interaction of flavor molecules with four protein molecules. Combinations of these types create specific taste sensations. In most fish, taste plays the role of contact reception, since taste sensitivity thresholds are relatively high. But in some fish, taste can acquire the functions of a distant receptor. Thus, freshwater catfish, with the help of taste buds, are able to localize food at a distance of about 30 body lengths. When taste buds are turned off, this ability disappears. With the help of general chemical sensitivity, fish are able to detect changes in salinity up to 0.3% of the concentration of individual salts, changes in the concentration of solutions organic acids(lemon) up to 0.0025 M (0.3 g/l), pH changes of the order of 0.05-0.07 carbon dioxide concentration up to 0.6 g/l.
Non-olfactory chemoreception in fish is carried out by taste buds and the free endings of the vagus, trigeminal and some spinal nerves. The structure of taste buds is similar in all classes of vertebrates. In fish, they are usually oval in shape and consist of 30-50 elongated cells, the apical ends of which form a canal. The nerve endings approach the base of the cells. These are typical secondary receptors. They are located in the oral cavity, on the lips, gills, in the pharynx, on the scalp and body, on the antennae and fins. Their number varies from 50 to hundreds of thousands and depends, like their location, more on the ecology than on the species. The size, number and distribution of taste buds characterize the degree of development of taste perception of a particular fish species. The taste buds of the anterior part of the mouth and skin are innervated by fibers of the recurrent branch facial nerve, and the mucous membrane of the mouth and gills - by fibers of the glossopharyngeal and vagus nerves. The trigeminal and mixed nerves are also involved in the innervation of taste buds.
Fish react to sounds: a clap of thunder, a shot, the sound of a boat's oar on the surface of the water causes a certain reaction in the fish, sometimes the fish even jumps out of the water at the same time. Some sounds attract fish, which fishermen use in their methods, for example, fishermen in Indonesia and Senegal lure fish using rattles made from coconut shells, imitating the natural crackling sound of a coconut in nature, which is pleasant for fish.
Fish make sounds themselves. The following organs are involved in this process: the swim bladder, the rays of the pectoral fins in combination with the bones of the shoulder girdle, jaw and pharyngeal teeth and other organs. The sounds made by fish resemble blows, clicking, whistling, grunting, squeaking, croaking, growling, crackling, ringing, wheezing, beeping, bird calls and chirping insects.
Sound frequencies perceived by fish are from 5 to 25 Hz by the lateral line organs, and from 16 to 13,000 Hz by the labyrinth. In fish, hearing is less developed than in higher vertebrates, and its acuity varies among different species: ide perceives vibrations whose wavelength is 25...5524 Hz, silver crucian carp - 25…3840 Hz, eel - 36…650 Hz. Sharks pick up vibrations made by other fish at a distance of 500 m.
They record fish and sounds coming from the atmosphere. Plays a major role in recording sounds swim bladder, connected to the labyrinth and serving as a resonator.
The hearing organs are very important in the life of fish. This includes the search for a sexual partner (in fish farms, traffic is prohibited near ponds during the spawning period), school affiliation, and information about finding food, territory control, and protection of juveniles. Deep-sea fish, which have weakened or absent vision, orient themselves in space and also communicate with their relatives using hearing, along with the lateral line and smell, especially considering the fact that sound conductivity at depth is very high. 
