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Why is the midline needed in fish? Remote “touch.” Why do fish have a “lateral line”?

A significant role in the behavior of fish is played by sensory organs - the lateral line, or seismosensory system. It unites all the sensitive displacement receptor cells that can be found in various areas of the body and head.

The lateral line runs in the form of a longitudinal canal, immersed in the skin and opening outwards with holes. Visually, the lateral line is visible as a dark or light stripe on both sides of the body from the head to the end of the caudal peduncle. Its structure, external shape and location on the body of the fish vary greatly among different species.

Most fish have one channel on each side, and some have up to 5 or more, for example, greenlings. In some fish it is arched, in others it has one or several tubercles; in some, it is hardly noticeable visually, in others, its branches are clearly visible on the head. In some fish, free neuromasts or canal organs are scattered throughout the body or individual parts of it, most often on the head. In sea ducks, for example, seismosensory canals are present only on the head; they are absent on the body and are replaced by openly seated seismosensory points. Fishes of the cetacean family have thick lateral line canals with huge round pores. At the same time, there are fish in which the lateral line is absent or incomplete. These fish include mullet, dallium, many carp-toothed fish, silversides and others.

Sensitive cells of the lateral line, free neuromasts and canal sensory organs end at the apex with papillae or hairs, and on the opposite side with a nerve branch. The displacement of the papilla or hair creates a generator potential that transmits information along the nerves to the acousticolateral center of the brain. The lateral line organs also contain ampullary and ampullary-like cells that perform electroreceptor functions.

Visual observations have established that a thunderstorm discharge causes panic among ruffes and rudd. Fish detect earthquakes before the most sensitive instruments. Some species of sharks sense even minor electrical impulses that accompany the muscular efforts of a swimming person. Using the lateral line, they can find fish in the dark that do not move, but only breathe on the seabed.

Sharks react differently to electrical impulses of varying strengths. If the source is weak, then they attack; if it is strong, they swim away. Taking into account this behavior, a method was developed and is used today to scare sharks away from sea beaches: exposure to the lateral line with electrical discharges that are harmless to humans.

The lateral line system analyzers are located differently on the fish’s body and functionally complement each other. This allows fish that have similar receptors to differentially perceive irritations coming from outside. Open neuromasts (genipores, buccal pores) receive vibrations of water, mainly from its contact with the surface of the body. Most fish species living in the coastal zone or near the bottom have predominantly or exclusively genipores on their heads. Receptors of closed channels of the lateral line are more or less isolated from surface stimuli. They perceive fluctuations in hydrodynamic fields, sound and infrasonic vibration. This type of structure of the lateral line organs is characteristic, first of all, of predator fish that live in open waters and can only occasionally approach the shores.

With the help of the lateral line and other receptors of the seismosensory system, fish detect the approach of an enemy or prey. Waves run in front of a swimming fish, reflecting from underwater objects, and, returning to the fish, are perceived by its lateral line.

Free neuromasts and canal organs of the lateral line are mechanoreceptors that perceive flows of water and sound as vibrations. With their help, the fish picks up tiny vibrations (from 6 vibrations per second or more), determining the direction of the flow of water and sound, the proximity of neighbors, obstacles, etc. By sensing water currents with their lateral line - strong or barely noticeable - fish can distinguish the size of an obstacle or objects moving in the water.

The lateral line organs, as displacement receptors, function effectively in the near acoustic field. Sources of mechanical stimuli are also determined by the lateral line organs at close range. Fish have two types of sound receptors: pressure receptors (hearing organs), which allow them to sense sound waves over long distances, and displacement receptors - lateral line organs, which allow them to subtly analyze the acoustic situation. Fish can use skin receptors for these purposes, which are also displacement receivers.

The topography of the displacement receptors of the seismosensory system is extremely important for determining the direction and distance from the source of mechanical, acoustic, and electromagnetic vibrations. Almost all fish that have a well-developed seismosensory system are perfectly oriented with its help when moving in schools, in feeding fields and spawning areas. Displacement receptors, directly related to the fish’s hearing, function simultaneously with vision. So, for example, when attacking prey, a pike is guided by vision and displacement receptors - the organs of the lateral line, which are well developed on its head, especially on the lower jaw and on the sides of the body. These are, of a kind, small primitive radars that determine the location of the victim target with great accuracy. It is thanks to this “guidance” that the pike does not make idle throws at the hunted victim.

The lateral line also functions well in sea eels. This voracious predator of the sea, like pike in fresh water, lies in wait for its prey in ambush, from where it rushes at the victim according to the indications of the displacement organs.

In monkfish, the lateral line organs are located in the grooves of the skin on the upper surface of the strongly flattened body, which allows it to perceive vibrations and currents of water coming mainly from above. This fish lies motionless on the ground, and the leathery brush of a separate dorsal ray moves above its head. This lazy predator “invites” its prey. As soon as the trusting fish saw the “worm-shaped tip” and approached it, it instantly finds itself in the huge toothy mouth of the monkfish.

The seismosensory system of cyprinid fish is well developed. For many of them, the sense of the lateral line, along with the sense of smell and touch, is leading in the search for food. Cod and many other cod fish have a well-developed lateral line on both sides of the body, and it is especially complexly branched on the head. On each side of the head, the lateral line forms many canals: preopercular-mandibular, infraorbital and supraorbital with a short commissure connecting the right and left canals. The interorbital commissure of the supraorbital canal is located in a special depression, the frontal - mucus fossa, the external shape of which varies greatly among different cod fish; in cod, haddock and pollock, the mucus pit is closed. In some cod it is open.

Along each of the channels of the lateral line system on the head there are multi-membered groups of nerve endings - genipores, or these channels open outwards with a number of pores. Cod, for example, has 26-27. Moreover, single genipores are also present in this case. The lateral line of some cod representatives is continuous (haddock, pollock), while in others it is discontinuous (cod). In some codfish, such as cod, the lateral line is continuous on the body and discontinuous on the caudal peduncle. Such a complex seismosensory system - displacement receptors - allows cod, cod and other cod fish to navigate in the complete darkness of the sea depths, find food, move in a coordinated manner in schools, and avoid enemies, including getting caught in trawl fishing gear. In conditions of poor visibility, cod uses the senses of the lateral line organs to find moving food (mainly small fish), and with the senses of smell and tactile senses (taste, touch) it looks for stationary, favorite food (mollusks, licks). Thus, in the Barents Sea, a blind cod was caught with a lot of food in its stomach - capelin. The fat content of the cod (the ratio of liver weight to body weight as a percentage) was quite high, which indicates good feeding conditions.

This example, as, by the way, other similar catches, indicates that cod, being blind, finds and obtains enough food for itself thanks to a well-developed sense of smell and touch, and the presence of a complex seismosensory system.

There are naturally blind cave fish - anopgichi, which, with the help of a seismosensory system, provide themselves with normal conditions of existence and reproduction. In underground karst waters live blind-eyes, which have highly developed lateral line organs and organs of touch on the head, body and caudal peduncle. They replace not only vision for these fish, but also other remote sensory organs.

The lateral line plays a significant role in spawning waters to attract a female or in competition between males over her. In some species of fish, the male, having built a nest house, sends acoustic-mechanical signals, which the female takes as an invitation to “enter the house” as a “young mistress.” In other species, the male, with an energetic movement of his tail, directs the flow of water towards his opponent and, thus, influences his lateral line, informing the enemy that the spawning area is occupied.

The functions of the lateral line and other displacement receptors, which allow fish to detect water vibrations in a certain frequency spectrum, have been poorly studied from the point of view of their significance in the schooling behavior of fish. Thus, the seismosensory system of fish is a unique invention of nature. It provides fish with the opportunity to adequately change their behavior depending on the biotic and abiotic environment, and in each specific case - and how, and is the most important sensory organ in the struggle for life.

Linea lateralis ll is a peculiar sensory organ of fish that perceives low-frequency vibrations of water; it is a subcutaneous canal lined with sensitive epithelial cells with nerve endings approaching it. The channel communicates with the external environment through holes piercing the scales or integument of the body. The lateral line has a systematic meaning. Her appearance is very diverse. In most fish, the lateral line runs in the form of a straight line along the sides of the body from the head to the caudal fin (bream, carp, perch, etc.). This lateral line is called complete. In some species of fish, the lateral line forms a sharp bend above the pectoral fins (sichel fish, halibut). In smelt and verkhovkas the lateral line is incomplete; it occupies several scales. The lateral line can be located on the belly (garfish) or on the back (gerbil). Terpugidae have 4-5 pairs of lateral lines, but toteniaceae have 1-3. Herrings, gobies and some other fish do not have a lateral line. Its function is performed by a highly developed system of sensory channels on the head or genipora. Fishes with a lateral line (cod, navaga) also have sensory canals and genipores (Fig. 21). The characteristic of the lateral line can be written by the formula. To compile the lateral line formula, the number of scales along the lateral line, above and below it is calculated. So, the formula for the ide line is:

What does it mean: 56 – the smallest number of scales along the lateral line for the species; 61 – the largest number of scales along the lateral line for the species; 8-9 – number of scales above the lateral line to the dorsal fin; 4-5 – number of scales under the lateral line to the ventral fins. It is not always possible to accurately calculate the scales above and below the side line, so sometimes they are limited to calculating the scales only along the side line. In this case, the ide formula will look like this: ll =56-61.

Figure 21 – Genipores and sensory canals:

1 – on the head of the cod; 2 - on the head of navaga.

Side line is the oldest 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 4 lines on each side. This is where its second name comes from - eight-line chir.

In most bony fishes, the lateral line stretches along the body (without interruption or interruption in some places), extends onto the head, where it forms a complex system of canals. The lateral line channels are located either deep in the skin or open on the surface of the skin.

An example of the open surface arrangement of neuromasts - 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, to flow currents, to chemical stimuli and to electromagnetic fields with the help of neuromasts - structures that unite several hair cells. 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.

Channel neuromasts stretch from head to tail along the sides of the body, usually in one row (fishes of the family Hexagramidae have six or more rows). The term “lateral line” in common usage refers specifically to canal neuromasts. However, in the world of fish, neuromasts are also described, separated from the canal part and looking like independent organs.

The labyrinth and canal and free neuromasts, located in different parts of the fish’s body, do not duplicate, but functionally complement each other.

It is believed that the sacculus and lagena of the inner ear are responsible for sound sensitivity from a great distance, and the lateral system allows you to localize the source of sound at close range. It has been experimentally proven that the lateral line perceives low-frequency vibrations, both sound and those arising from 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.

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. Water disturbance serves as an important channel for informing aquatic animals about events both in the reservoir itself and beyond. Moreover, the disturbance of the reservoir is perceived by both pelagic fish 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 stimuli 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. Moreover, the sensitivity of the lateral line to waves is extremely high. Thus, for afferentation to occur from the lateral line, a displacement of water relative to 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.

As a rule, waves on the surface of a reservoir generate rolling motion. Therefore, when excited, not only the lateral line of the fish, but its labyrinth becomes excited. Experiments have shown that the semicircular canals of the labyrinth respond to rotational movements in which water currents involve the body of the fish. The utriculus receives the linear acceleration that occurs during the rolling process.

Observations of marine fish indicate that during a storm, fish, both solitary and schooling, change their behavior. 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. Disturbance suppresses feeding behavior and forces fish to migrate. Similar changes in feeding behavior are observed in fish species inhabiting inland waters. Anglers know this: when there is excitement, the fish stop biting.

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The sense organs have a huge influence in the life of a fish, which also affects their behavior. This is a seismosensory system, or otherwise it is called the lateral line. This line unites all receptor cells located not only in the head, but also in other parts of the body.

This sensitive organ, meaning the lateral line, is also present in some amphibians and their larvae, and not only in fish. Such an organ is used for several purposes, namely:

so that the fish can navigate;
and also for hunting.

If you look closely, this organ looks like a thin line that exists on both one and the other side of the body and it stretches, starting from the gill slits, and ending at the tail. Some species of fish have a certain part of the receptors in the lateral line, which are converted into so-called electroreceptors, which allow them to catch electrical vibrations produced by the environment.

Anatomy of the lateral line

Each channel of the seismosensory system on the head has a genipore in length - nerve endings, and in large numbers. Also, such channels can open outward. For example, cod has as many as 26 such channels.

The lateral line can be either continuous or interrupted.

This complex system allows fish to perfectly navigate in the depths of water, in pitch darkness. Also, using their seismic sensor system, they:

find food;
can move in a coordinated manner while in a flock;
running away from enemies or other danger.

If visibility is poor, then the lateral line helps to look for moving food, usually small fish. But with the help of tactile senses, such as touch and taste, she finds motionless food - licking or a shellfish. There are several examples where a blind fish can perfectly take care of its food, which is achieved by the presence of such a complex seismosensory system.

There is such a species of fish as the blind cave fish, although it does not have vision by nature - these are anopgihi. And thanks to its seismosensory system, it perfectly provides itself with good conditions not only for existence, but also for reproduction. There is another type of fish - blind-eyes, which live in the so-called karst waters. They have a well-developed lateral line, as well as organs of touch, which are present on the head, as well as on the body, and also on the tail. All this replaces not only the organs of vision, but also some other organs.

It is worth saying that the lateral line also plays an important role during spawning. It helps attract a female. There are species of fish in which the male builds a nest house, and then sends specialized acoustic-mechanical signals to the female, inviting her to visit such a “house.” Some males direct the water flow towards their opponent. This makes him understand that this spawning site has already been occupied.

So we can safely say that the seismosensory system is a unique natural invention that allows fish to detect water vibrations, which are still very poorly understood in relation to the schooling behavior of marine individuals.

Side line

Anatomy[ | code]

Lateral line in fish[ | code]

Astyanax mexicanus

Links[ | code]

Scorpis violacea from the kyphosis family Esox lucius

The lateral line and its role in fish behavior. Ichthyological minimum

With the help of the lateral line and other receptors of the seismosensory system, fish detect the approach of an enemy or prey.

Waves run in front of a swimming fish, reflecting from underwater objects, and, returning to the fish, are perceived by its lateral line.

Fish can use skin receptors for these purposes, which are also displacement receivers.

Along each of the channels of the lateral line system on the head there are multi-membered groups of nerve endings - genipores, or these channels open outwards with a number of pores. Cod, for example, has 26-27. Moreover, single genipores are also present in this case. The lateral line of some cod representatives is continuous (haddock, pollock), while in others it is discontinuous (cod). In some codfish, such as cod, the lateral line is continuous on the body and discontinuous on the caudal peduncle. Such a complex seismosensory system—displacement receptors—allows cod, cod and other cod fish to navigate in the complete darkness of the sea depths, find food, move in a coordinated manner in schools, and avoid enemies, including getting caught in trawl fishing gear. In conditions of poor visibility, cod uses the senses of the lateral line organs to find moving food (mainly small fish), and with the senses of smell and tactile senses (taste, touch) it looks for stationary, favorite food (mollusks, licks). Thus, in the Barents Sea, a blind cod was caught with a lot of food in its stomach - capelin. The fat content of the cod (the ratio of liver weight to body weight as a percentage) was quite high, which indicates good feeding conditions.

Side line- a sensitive organ in fish, as well as in the larvae of amphibians and some adult amphibians, perceiving movement and vibrations of the surrounding water. Used for orientation and also for hunting. Externally it looks like a thin line on both sides of the body, stretching from the gill slits to the base of the tail. In some species, some of the lateral line receptors are converted into electroreceptors and can detect electrical vibrations in the environment. Some representatives of crustaceans and cephalopods have similar organs.

Anatomy

The lateral line receptors are called neuromasts, each of which consists of a group of hair cells. The hairs are located in a convex jelly-like cupule, about 0.1-0.2 mm in size. Hair cells and cupules of neuromasts are usually found in the lower part of the grooves and pits that make up the lateral line organs. The hair cells of the lateral line are similar to the hair cells of the inner ear, suggesting that these organs have a common origin.

The lateral line organs of bony fishes and elasmobranchs usually have the form of canals, in which the neuromasts are not directly connected to the external environment, but through canal pores. In the lateral lines of some fish and various parts of the fish's body surface, free-standing neuromasts not associated with the canals may also be present.

Lateral line in fish

The development of the lateral line organs is associated with the animal’s lifestyle. For example, in actively swimming fish, neuromasts are usually located in canals. The lateral line itself is located at the maximum distance from the pectoral fins, which may reduce the distortion that occurs when the fish moves.

The lateral line organs help fish navigate, sense the direction and speed of currents, and detect prey or enemies. For example, in the blind cave fish Astyanax mexicanus There are rows of neuromasts on the head, which are used for precise detection of food objects. Some carp-toothed fish are able to sense ripples that occur when an insect moves on the surface of the water. Experiments with pollock have shown that the lateral line is of key importance in the schooling movement of fish.

Links

Tubular scales of the lateral line of roach.
A clearly visible dark lateral line running from the gills to the tail in fish of the species Scorpis violacea from the kyphosis family Small holes on the pike's head ( Esox lucius) belong to the seismosensory channels of the lateral line.

Surrounding water. Used for orientation and also for hunting. Externally it looks like a thin line on both sides of the body, stretching from the gill slits to the base of the tail. In some species, some of the lateral line receptors are transformed into electroreceptors and can detect electrical vibrations in the environment. Some representatives of crustaceans and cephalopods have similar organs.

Anatomy

The lateral line receptors are called neuromasts, each of which consists of a group of hair cells. The hairs are located in a convex jelly-like cupule, about 0.1-0.2 mm in size. Hair cells and neuromast cupules are usually found in the lower part of the grooves and pits that make up the lateral line organs. The hair cells of the lateral line are similar to the hair cells of the inner ear, suggesting that these organs have a common origin.

The lateral line organs of bony fishes and elasmobranchs have the form of canals, in which the neuromasts are connected to the external environment not directly, but through canal pores. Additional neuromasts may be present at various points on the surface of the fish's body.

Lateral line in fish

The development of the lateral line organs is associated with the animal’s lifestyle. For example, in actively swimming fish, neuromasts are usually found in canals rather than openings. The lateral line itself is located at the maximum distance from the pectoral fins, which may reduce the distortion that occurs when the fish moves.

Lateral line organs help fish avoid collisions, navigate water currents, and detect prey. For example, the blind cavefish Astyanax mexicanus has rows of neuromasts on its head that are used to accurately detect food in the absence of vision. Some carp-toothed fish are able to sense ripples that occur when an insect moves on the surface of the water. Experiments with pollock have shown that the lateral line is of key importance in the schooling movement of fish.

Links

Lateral organs- article from
Side line- article from the Great Soviet Encyclopedia
// Encyclopedic Dictionary of Brockhaus and Efron: In 86 volumes (82 volumes and 4 additional ones). - St. Petersburg. , 1890-1907.

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07.06.2016

WHAT THE SIDE LINE CAN DO AND WHY YOU NEED IT

The organs of the lateral line of fish are a very popular topic, and as often happens, excessive popularity has led to the fact that one can sometimes read absolutely fantastic things about the capabilities of this “organ of the sixth sense.” Therefore, I would like to dwell on this topic in more detail.

DEVICE

First of all, we need to start with the fact that the term “side line” itself is completely unclear and only adds to the confusion. Firstly, it is not clear what the line is, and, secondly, why it is lateral.

This name comes from the English language (lateral line), from those times when the microscope had not yet been invented, and scientific descriptions of animals consisted of a simple listing of their external characteristics, visible to the naked eye. Indeed, in many fish on the sides of the body you can see on each side a thin, as if dotted line, which goes from the head to the tail. This is what they called the “side line.”

If you use a microscope, you can see (diagram below) that this line is a chain of special sensory organs that are placed in a thin channel running under the skin and piercing the scales. From this channel, short branches extend outwards, which open with a small hole - sometimes. Inside the channels, which are filled with a special viscous liquid, there are sensory organs of the lateral line - neuromasts.

But the channels on the body are not the entire “lateral line”. The fact is that there are channels on the head of the fish and it is here that they are especially well developed. On the head, the lateral line canals branch in complex ways; they are usually expanded, pass inside the bones and communicate with the external environment through numerous openings.

But this is not the whole “side line”. In addition to neuromasts lying inside the canals, fish also have so-called free neuromasts, which are located directly on the surface of the skin, mainly again on the head.

PURPOSE

What can neuromasts do and why do fish have two types of them - canal and free?

The role of the lateral line organs in the perception of low-frequency sounds and in determining the direction to the source of these sounds in the “RR” has already been discussed. But the significance of the side line does not end there.

A neuromast is, in fact, a bunch of special cells bearing sensory hairs. The movement of water near the fish's body puts pressure on the sensitive hairs, their angle of inclination changes - and an electrical signal is sent along the nerve to the brain. Neuromasts thus perceive the speed and direction of the current surrounding the fish's body.

But this only happens with open - free - neuromasts. The same neuromasts that are hidden in the canals are protected from direct exposure to water viscous mucus that fills the canal. Channel neuromasts do not “feel” directed water flows near the fish’s body. Their purpose is different. They are “tuned” to perceive very small-scale accelerations of water particles surrounding the fish. These displacements cause a corresponding displacement of the fluid filling the canals, and this is already perceived by the canal neuromasts. The uniqueness of this system lies in the fact that channel neuromasts are able to distinguish the smallest disturbances in the water against the background of its constant movement around the fish. This is similar to how people on the subway can distinguish the voices of passengers over the hum of a passing train.

Thus, the lateral line organs of the fish are represented by two types of “receivers”. One of them (free neuromasts) controls the flow of water flowing around the body of the fish, and the other (channel neuromasts) controls various “disturbances” in these flows, such as small turbulences and oscillatory movements of water particles.

WHY DOES FISH DO THIS?

Thanks to the work of free neuromasts, the fish controls its speed and direction of movement relative to the surrounding water. It is thanks to them that she unmistakably navigates the currents. For example, as you know, fish most often stand with their heads against the current. How does it determine the direction of the flow? It is with the help of free neuromasts (they are also helped by vision and touch, however).

But the work of channel neuromasts is more interesting for us. The fact is that with their help, fish perceive the presence of nearby moving and stationary objects. This could be potential food, or, conversely, a predator, or some inanimate object - some obstacle, or, for example, a fishing line.

With moving objects, everything is more or less clear - movement causes disturbance in the aquatic environment, and neuromasts sense it. But how does this happen in the case of a stationary object? The point here is that with the help of the lateral line, the fish perceives not the objects themselves, but the movement of the water around them. Therefore, an object can be stationary - the main thing is that water flows around it. When encountering obstacles, water changes the direction of its movement, forming vortices, zones of acceleration and deceleration of the flow. All this is “tracked” by the lateral line, and the fish, even in the dark or in completely muddy water, is constantly “aware” of what surrounds it.

Moreover, her own movement also helps her. Swimming fish themselves cause disturbances in the aquatic environment. In particular, she literally “drives the wave” ahead of her. When encountering obstacles, this wave changes its shape, and neuromasts react to this by sending appropriate signals to the brain. This mechanism is very similar to the electrolocation mechanism discussed in one of the previous issues of RR. Moreover, it must be taken into account that the side line is a very finely tuned mechanism. Many experiments have proven that it allows fish to determine not only the size of objects, but also their shape, as well as the speed and direction of movement.

Thus, the lateral line organs give the fish detailed information about everything that is happening around. The question is from what distance the side line is capable of receiving information. It turns out that in this regard its capabilities are not very impressive. The lateral line is a short-range organ. In most cases, we can talk about distances of no more than 1-1.5 meters, but more often the distance of perception of signals by the side line is calculated in tens of centimeters, or even centimeters. This depends on many parameters - on the size and shape of the signal source, on the nature of its own movement, on the state of the water environment itself.

But even at short distances, information from the lateral line organs is very important for fish. Indeed, in most cases, visibility under water is low, and the lateral line allows the fish to largely compensate for the lack of visual information.

Alexey TSESSARSKY

Speaking about the role that the lateral line organs play in the life of a fish, we can recall the discussions that at one time took place on the Internet and in the media about the pros and cons of “invisible fishing line” - fluorocarbon. The material from which this fishing line is made has almost the same refractive index of light as water and is therefore considered to be invisible in water. The question arises whether this is good from a fishing point of view or not. At first glance, the answer is obvious - the more inconspicuous the tackle, the better. However, during the debate another point of view was expressed. Imagine, its proponents said, that you suddenly stumble upon some invisible object. Naturally, your first reaction is fear. The same thing happens with a fish, which, having taken the bait, suddenly “bumps” with its lips on an invisible fishing line. In theory, she should also get scared and throw the bait.

It looks plausible. But given what is known about the sideline, one has to admit that such a point of view is naive. Experiments have long been known in which minnows swam for a long time in complete darkness in an aquarium in which thin (about 0.1 mm) vertical threads were stretched at a close distance from each other. Despite the complete lack of visibility, the minnows unerringly avoided these obstacles, perfectly sensing their presence using the side line.

Therefore, you should not think that by making the fishing line completely invisible, we will mislead the fish. Of course, having approached the bait at a sufficiently close distance, the fish probably “notices” the presence of this invisible fishing line in the same way as the experimental minnows noticed the stretched threads. Therefore, it is unlikely that direct contact with the fishing line will be something completely unexpected for the fish.

In order to successfully hunt and escape from enemies, it is not enough for fish to see and hear well - by the way, their hearing is not that great - but here other senses come to their aid, and, above all, the so-called lateral line . This organ of the “sixth sense” is found only in fish and amphibians that constantly live in water. The lateral line is a canal that usually runs along the body from head to tail. The canal contains sensory papillae, connected to the external environment by tiny holes located in the scales, and by nerves to the brain. Sometimes the lateral line is discontinuous, and sometimes, as in herrings, it is located on the head.

The lateral line perceives even the slightest water vibrations and helps fish determine the strength and direction of the current, catch reflected water currents, feel movement in the school, and excitement on the surface. Using their “sixth sense”, fish can swim at night in muddy water without bumping into underwater objects or each other.

The lateral line also makes it possible to capture those vibrations that are transmitted to the water from the outside - as a result of soil shaking, impacts on the water, or a blast wave.

It was the lateral line that helped the fish feel the shaking of the table caused by the sounding alarm clock, as described in.

Fish feel such vibrations with much greater sensitivity than vibrations in the air. Therefore, experienced fishermen are careful not to knock on the boat, walk along the shore without stomping, but are not afraid to talk loudly.

The lateral line plays an extremely important role in predatory fish during hunting. For example, a blinded woman does not lose orientation in the water and accurately grasps a moving fish. But a blind pike with a destroyed lateral line loses its ability to navigate, it bumps into the walls of the pool and, even very hungry, does not pay any attention to the fish swimming nearby.

Among flounders there are often blind from birth, and they do not die, are normally well-fed and live to a ripe old age. This once again confirms that the lateral line plays a great role in the life of fish.

For peaceful fish, the “sixth sense” is also useful - it helps them detect enemies in time. Using the lateral line, peaceful fish distinguish the vibrations created by predatory fish from the vibrations created by their fellows. The fish perfectly “understand” that movement helps the predator to detect them, and therefore at night small fish stand calmly. Particularly typical in this regard is the behavior of the Atlantic herring, which sleeps “deadly” at night.

In addition to the “sixth sense”, touch and smell help fish navigate in the water. The organs of touch in some fish are located almost throughout the body, such as in. But most often they are located near the mouth. In cod, the organ of touch is the antennae on the lower lip. Our catfish has two long movable barbels, while its close overseas relatives have up to sixteen such barbels.

The deep-sea fish Gigantactis, which lives in the Indian Ocean, is armed with an amazing probe. The fish does not exceed five centimeters, but on its nose there is a probe almost the same length as itself. The probe ends in a luminous growth resembling a mushroom cap. Gigantactis deftly wields it, turning it up, down, right and left.

Some fish have organs of touch that look like a real beard. The deep sea devil fish looks funny. She has a whole spreading bush growing on her chin. This fish is the size of an orange. Found in the Atlantic Ocean at a depth of over 500 meters.

And the fish Ultimostomias Mirabilis, caught at a depth of 1800 meters, has a beard reaching 40 centimeters, while the fish itself is no longer than 4 centimeters.

In the Black Sea trigla and the deep-sea “walking” fish Benthosaurus, the elongated rays of the pectoral fins serve as organs of touch. In the labyrinth gourami fish, the pectoral fins are elongated into long thread-like processes. They are very mobile, and a gourami, without moving, can simultaneously feel objects with one whisker in front and the other in the back.

Many fish, including our freshwater ones, are guided by their sense of smell when searching for food.

In bony fish, the olfactory organs are paired nostrils. They are located on both sides of the head and lead into the nasal cavity. Water enters one hole and leaves another. This arrangement of the olfactory organs allows the fish to sense the odors of substances dissolved or suspended in water. However, during the current, the fish senses odors only in the stream carrying odorous substances, and in calm waters - only in the direction of the water currents. Anglers can tell you a lot about the sense of smell of fish. They know well that the smell of fresh bait made from rye crackers, hemp cake, and just cooked porridge attracts many peaceful fish.

Sharks can smell far away. When whaling ships are cutting up their prey, they gather around in masses.

As if by magic, South American piranha fish flock to the smell of fresh blood. Once you put a freshly killed animal into the river, it will soon be left with a cleanly gnawed skeleton.

When hunting, fish use several senses simultaneously.

Diurnal predators, when searching for prey, are guided mainly by vision and water vibrations.

The sense of smell in diurnal predators is poorly developed, but they still smell. often does not pay attention to a naked jig, but rushes towards it from afar if a worm or piece of fish is attached to the hook.

It is believed that some fish, such as the seahorse and beluga, use echolocation, that is, when they make sounds, they can catch their reflection from the bottom or other underwater objects. True, this has not yet been proven, but some fish have radars - devices that use electromagnetic waves rather than sound waves.

The muddy waters of the Nile are home to the long-snout fish, or water elephant. They named it so for its long snout, elongated in the form of a trunk. This is a large fish, reaching two meters in length. The Arabs have long treated the long-snout with superstitious fear, believing that it can see... with its tail. But in 1953, the East African Institute found that the water elephant has a kind of “alternating current generator” near its tail. The “batteries” of this “generator” have a voltage of about six volts. When discharged, the “batteries” create an electromagnetic field around the fish. If any object enters this field, it is distorted, and a special receiver on the fish’s back registers the distortion.

“Radar” allows the longsnout to detect a grain of sand falling behind its tail or a bait hanging on a hook. It is very sensitive, and it is no coincidence that the water elephant almost never gets caught in fishing nets.

Apparently, other fish that have electric organs also have a “radar system”: electric eels, electric catfish, and torpedo rays.

V. B. Sabunaev
"Entertaining ichthyology"