Sense organs. Vision.

The organ of vision, the eye, in its structure resembles a photographic apparatus, and the lens of the eye is similar to a lens, and the retina is similar to the film on which the image is obtained. In terrestrial animals, the lens is lenticular in shape and is capable of changing its curvature, so animals can adapt their vision to distance. The lens of fish is spherical and cannot change shape. Their vision is adjusted to different distances as the lens approaches or moves away from the retina.

The optical properties of the aquatic environment do not allow the fish to see far. Almost the limit of visibility for fish in clear water is considered to be a distance of 10-12 m, and fish can see clearly no further than 1.5 m. Diurnal predatory fish living in clear water (trout, grayling, asp, pike) see better. Some fish see in the dark (pike perch, bream, catfish, eel, burbot). They have special light-sensitive elements in their retina that can perceive weak light rays.

The angle of view of fish is very large. Without turning their bodies, most fish are able to see objects with each eye in a zone of about 150° vertically and up to 170° horizontally.

(Fig. 1) Otherwise, the fish sees objects above the water. In this case, the laws of refraction of light rays come into force, and the fish can see without distortion only objects that are directly overhead - at the zenith. Obliquely incident light rays are refracted and compressed into an angle of 97°.6.

(Fig. 2)

The sharper the angle of entry of the light beam into the water and the lower the object, the more distorted the fish sees it. When the light beam falls at an angle of 5-10°, especially if the water surface is choppy, the fish stops seeing the object. Rays coming from the fish's eye outside the cone shown in rice. 2,

are completely reflected from the water surface, so it appears mirror-like to the fish. On the other hand, the refraction of rays allows the fish to see seemingly hidden objects. Let's imagine a body of water with a steep, steep bank.(Fig. 3)

.beyond the refraction of rays by the water surface can see a person.

Color vision in fish is confirmed by their ability to change color depending on the color of the ground (mimicry). It is known that perch, roach, and pike, which stay on a light sandy bottom, have a light color, and on a black peat bottom they are darker. Mimicry is especially pronounced in various flounders, capable of adapting their color to the color of the ground with amazing accuracy. If a flounder is placed in a glass aquarium with a chessboard placed under the bottom, then chess-like cells will appear on its back. Under natural conditions, a flounder lying on a pebble bottom blends so well with it that it becomes completely invisible to the human eye. At the same time, blinded fish, including flounder, do not change their color and remain dark-colored. From this it is clear that the change in color by fish is associated with their visual perception.

Experiments of feeding fish from multi-colored cups confirmed that fish clearly perceive all spectral colors and can distinguish similar shades. The latest experiments based on spectrophotometric methods have shown that many species of fish perceive individual shades not worse than a man.

Using food training methods, it has been established that fish also perceive the shape of objects - they distinguish a triangle from a square, a cube from a pyramid.

Of particular interest is the attitude of fish to artificial light. Even in pre-revolutionary literature they wrote that a fire built on the river bank attracts roaches, burbot, catfish and improves fishing results. Recent studies have shown that many fish - sprat, mullet, syrty, saury - are directed to sources of underwater lighting, so electric light is currently used in commercial fishing. In particular, this method is used to successfully catch sprat in the Caspian Sea, and saury near the Kuril Islands.

Attempts to use electric light in sport fishing have not yet yielded positive results. Such experiments were carried out in winter in places where perch and roach accumulated. They cut a hole in the ice and lowered an electric lamp with a reflector to the bottom of the reservoir. Then they fished with a jig and added bloodworms in a neighboring hole and in a hole cut away from the light source.

For sport fishing, it is tempting to use baits coated with luminous compounds.

It has been established that fish grab luminous baits. However, the experience of Leningrad fishermen did not show their advantages; In all cases, fish take regular bait more readily. The literature on this issue is also not convincing. It describes only cases of catching fish with luminous baits, and does not provide comparative data on fishing under the same conditions with ordinary baits.

The visual characteristics of fish allow us to draw some conclusions that are useful for the fisherman. It is safe to say that a fish located at the surface of the water is not able to see a fisherman standing on the shore further than 8-10 m and sitting or wading - further than 5-6 m; The transparency of the water also matters. In practice, we can assume that if an angler does not see a fish in the water when he looks at a well-lit water surface at an angle close to 90°, then the fish does not see the angler. Therefore, camouflage makes sense only when fishing in shallow places or on top in clear water and when casting over a short distance. On the contrary, items of fishing equipment close to the fish (lead, sinker, net, float, boat) should blend into the surrounding background.

Hearing.

The presence of hearing in fish was denied for a long time. Facts such as fish approaching the feeding place when called, attracting catfish by hitting the water with a special wooden mallet (“knocking” catfish), and reacting to the whistle of a steamboat have not yet proved much. The occurrence of the reaction could be explained by irritation of other sense organs. Recent experiments have shown that fish respond to sound stimuli, and these stimuli are perceived by the auditory labyrinths in the fish’s head, the surface of the skin, and the swim bladder, which plays the role of a resonator.

Lateral line organ.

The lateral line organ is present only in fish and amphibians that constantly live in water. The lateral line is most often a canal that stretches along the body from head to tail. Nerve endings branch out in the canal, perceiving even the most insignificant water vibrations with great sensitivity. With the help of this organ, fish determine the direction and strength of the current, feel the currents of water formed when underwater objects are washed away, feel the movement of a neighbor in the school, enemies or prey, and disturbances on the surface of the water. In addition, the fish also perceives vibrations that are transmitted to the water from the outside - soil shaking, impacts on the boat, blast waves, vibration of the ship's hull, etc.

The role of the lateral line in the fish’s grasping of prey has been studied in detail. Repeated experiments have shown that a blinded pike is well oriented and accurately grabs a moving fish, not paying attention to a stationary one. A blind pike with a destroyed lateral line loses the ability to orient itself, bumps into the walls of the pool and... being hungry, she does not pay attention to the swimming fish.

With this in mind, anglers must be careful both on shore and in the boat. Shaking the soil under your feet, a wave from careless movement in the boat can alert the fish and scare it away for a long time. The nature of the movement of artificial baits in the water is not indifferent to the success of fishing, since predators, when pursuing and seizing prey, feel the water vibrations created by it. Of course, those baits that most fully reproduce the characteristics of the usual prey of predators will be more catchy.

Organs of smell and taste.

The organs of smell and taste in fish are separated. The organ of smell in bony fishes is paired nostrils, located on both sides of the head and leading into the nasal cavity, lined with olfactory epithelium. Water enters one hole and leaves the other. This arrangement of the olfactory organs allows the fish to sense the odors of substances dissolved or suspended in water, and during the current the fish can only smell the stream carrying the odorous substance, and in calm waters - only in the presence of water currents.

The olfactory organ is least developed in diurnal predatory fish (pike, asp, perch), and stronger in nocturnal and crepuscular fish (eel, catfish, carp, tench).

The taste organs are located mainly in the mouth and pharyngeal cavity; In some fish, taste buds are located in the area of ​​the lips and whiskers (catfish, burbot), and sometimes located throughout the body (carp). As experiments show, fish are able to distinguish between sweet, sour, bitter and salty. Just like the sense of smell, the sense of taste is more developed in nocturnal fish.

In the literature there are instructions on the advisability of adding various odorous substances to bait and bait that seem to attract fish: mint oil, camphor, anise, laurel-cherry and valerian drops, garlic and even kerosene. Repeated use of these substances in food did not show any noticeable improvement in biting, and when large quantities odoriferous substances, on the contrary, fish almost completely stopped being caught. A similar result was given by experiments carried out on aquarium fish, which were reluctant to eat food soaked in anise oil, valerian, etc. At the same time, the natural smell of fresh bait, especially hemp cake, hemp and

sunflower oil , rye crackers, freshly cooked porridge, undoubtedly attracts fish and speeds up their approach to the feeder.

The importance of certain sense organs when finding food by various fish is shown in

table 1.

Table 1

As it turned out, the fish can perfectly see everything that is located on the shore. For this reason, every fisherman has a question: is a fish able to understand that a person standing above on the shore is its enemy?

Diagram of visual angles at which fish see objects underwater

What fish see and what they don't

Everyone has long known that bright clothes, in any situation, scare away fish, and they will swim away from this place, as they say, just in case of fire. In addition, the fish's ability to see what is happening on land is significantly influenced by the transparency and calmness of the water.

Fish viewing angle

It is extremely important for the fisherman to know that when observing from under water to land, there is a “blind” zone phenomenon. Which means that at a particular viewing angle, everything that happens on the shore becomes invisible to the fish.

Conclusion

For example, the sharpest viewing angle makes viewing impossible. How can this information be useful to the fisherman? As it turned out, the fisherman should stand as far from the shore as possible, then the fish will not be able to see him.

Optical refractions of water can play another unpleasant joke on fishermen

Also, a person standing at the very edge of the water will definitely be noticed by fish. Optical refractions of water can play another unpleasant joke on fishermen. If the bank is high, then the fish, being under the water below it, will be able to see the person perfectly, but the fisherman will not.

Although their sensory experiences are different from ours, they are no less interesting and varied than those of higher vertebrates. And, of course, the full development of these organs is associated with the fish’s habitat - water.

1. Vision.

The importance of vision is not so great in aquatic inhabitants compared to terrestrial ones.

It's connected, Firstly, with the fact that with increasing depth the illumination decreases significantly, Secondly, very often fish are forced to live in conditions of low water transparency, Thirdly, the aquatic environment allows them to use other senses with much greater efficiency.

Almost all fish have eyes located on both sides, which provides them with panoramic vision in the absence of a neck and, as a consequence, the impossibility of turning the head without turning the body. Low elasticity of the lens makes fish myopic and they cannot see clearly at long distances.

Many species have adapted their vision to highly specific living conditions: coral reef fish have not only color vision, but are also able to see in the ultraviolet spectrum; some fish that collect food from the surface of the water have eyes divided into two halves: the upper one sees what is happening in the air, the lower one - under water, in fish living in mountain caves, the eyes are generally reduced.

2. Hearing.

Surprisingly, fish have well-developed hearing, despite their lack external signs. Their hearing organs are combined with the balance organs and are closed sacs with otoliths floating in them. Very often the swim bladder acts as a resonator. In a dense aquatic environment, sound vibrations travel faster than in air, so the importance of hearing for fish is great.

It is a well-known fact that fish in water hear the footsteps of a person walking along the shore.

Many fish are capable of making various purposeful sounds: rubbing their scales together, vibrating various parts body and thus carry out sound communication.

3. Smell.

The sense of smell plays a significant role in the life of fish.

This is due to the fact that odors spread very well in water.

Everyone knows that a drop of blood falling into the water attracts the attention of sharks located several kilometers from this place.

In particular, salmon going to spawn use their sense of smell to find their way home.

Such a subtle sense of smell is developed in fish due to the fact that the olfactory bulb occupies a significant part of their brain.

4. Taste.

Flavoring substances are also perfectly distinguished by fish, because perfectly soluble in water. Taste buds are located not only in the mouth, but also throughout the rest of the body, especially on the head and antennae. For the most part, the taste organs are used by fish to search for food, as well as for orientation.

5. Touch.

Fish have ordinary mechanical receptors, which, like the taste organs, are located mainly at the tips of the antennae, and are also scattered over the skin. However, in addition to this, fish have a completely unique receptor organ - lateral line.

This organ, located along the middle on both sides of the body, is capable of perceiving the slightest fluctuations and changes in water pressure.

Thanks to the lateral line, fish can obtain information about the size, volume and distance to distant objects. With the help of the lateral line, fish are able to go around obstacles, avoid predators or find food, and maintain their position in the school.

6. Electrosensitivity.

Electrosensitivity is highly developed in many species of fish. It is an excellent addition to the already listed sense organs and allows fish to defend themselves, detect and obtain food, and navigate.

Some fish use electrolocation for communication, and thanks to the ability to sense the Earth's magnetic field, they can migrate over very long distances.

How do fish see? Can they see us? And who are we to them? Aliens, for whom the inhabitants of the underwater world are only a food product, or friendly aliens exploring their unknown and mysterious world. The life of underwater inhabitants is full of wonderful and amazing secrets.

The role of vision for underwater animals is extremely important. With its help, as with other senses (smell, touch, hearing), fish receive information about the environment, and also provide contact between individuals of their species. Vision also determines the feeding activity of fish. In predatory animals, it has one goal - to find prey and hide from a stronger inhabitant of the sea in order to avoid attack and rush again in search of less protected and weaker individuals. And for defenseless herbivorous fish, nothing is more important than to get away from a predator and hide in a secluded place.

The optical properties of water do not allow the animal to see far. The lens in fish cannot change shape and adapt vision to distance. Its pungency depends on the transparency of the water. Fish can see well in clear water at a distance of no more than 1.5-2 meters, but they can distinguish objects within 12-15 meters.

Predatory fish living in flowing clear water (trout, grayling, asp) see better. Since the eyes of fish are located on the sides of the head and at some elevation above the surface of the body, their angle of vision is very large and, without turning, they can see with each eye not only in front, but also on the sides - up to 1700 horizontally and about 1500 horizontally. verticals.

The hammerhead shark, due to the strange shape of its head, sees clearly in all directions: not only what is happening in front of it, but also vertically - above and below, to the side and behind.

In muddy and low-transparent water, fish are able to navigate through second sight - the lateral line, a unique device that functions as a kind of radar that allows it to detect the slightest fluctuations in the water. The eyes of fish do not have eyelids, and they are constantly open. Sea water washes them and cleanses them of foreign impurities.

Now let's return to the question of whether the fish can see us. This is especially often asked by amateur fishermen. Not entirely good, but fish can also see the surface world. According to the law of refraction of light rays, they see relatively clearly, without distortion, objects located directly above their heads, for example, a boat or a bird flying over the water.

Obliquely incident rays are refracted. And the sharper the angle and lower the object, the more distorted it appears to the fish. For example, an angler standing on the shore is visible to the fish quite well. But if he sits down, the fish practically does not see him, especially in stormy weather.

When fishing for mullet with a lifting hatchery, a fish caught in a net trap clearly sees the wall blocking its path and strives to escape, trying to jump over it. Sometimes large mullet conduct initial reconnaissance by slightly jumping out of the water, assessing the height of the wall, and only then make a powerful jump.

Finding themselves not in their environment, on the shore, fish do not lose their ability to navigate. For example, an eel calmly crawls from one body of water to another. And try throwing a live, freshly caught large fish ashore: it will do everything to find itself in its native element. Pisces can not only see, but also remember what they see.

An amazing incident occurred off the coast of Puerto Rico. A large mako shark was shot with a hunting harpoon gun. Having made a dash towards the sea and freed herself from the arrow, she rushed to the shore. To the amazement of those present, she tried to grab the unlucky hunter standing on the shore, not paying attention to the people nearby.

And some fish have eyes that are specially adapted for observation not only in water, but also in the air. Anableps fish is a four-eyed fish native to the Amazon. Her eyes are divided into upper and lower chambers, equipped with special optics. The upper part of the eye is adapted for observation in the air, the lower part - in water. This fish perfectly sees both a mosquito in the air and a small crustacean in the water.

Predatory fish see much better than herbivores. They need keen vision when tracking and pursuing victims. The peculiarity of the visual apparatus of some fish allows them to divide the movement of escaping prey into separate phases and guess its direction and speed, which allows them to catch a fast and agile prey with a lightning-fast throw. Small schooling fish see much worse.

Research has confirmed that fish even distinguish the shape of an object, distinguish a square from a triangle, and a cube from a pyramid, which even some land animals cannot do.

Pisces can see color. Especially those living in the surface layers of water, where the sun's rays penetrate well. This has long been proven by numerous experiments and is confirmed by their rich body coloration with various color shades, especially during the spawning period. And fish brides are more favorable towards a male with a bright and variegated coloring - they still accept him based on his clothes.

But who knows what else fish females are guided by when choosing a partner for procreation. Many species of fish know by sight the “husbands” they have chosen for life together and do not allow a stranger to invade their lives and ruin family happiness.

Color vision allows fish to adapt to their environment to protect themselves from predators. For example, fish living on a light pound have a light color, and those living among algae have striped camouflage clothing.

Well, some fish, such as flounder, change color literally on the move depending on the color of the soil and blend in with it so much that a predator, swimming over the hidden fish, does not notice it. However, blind fish, including flounder, do not change their color depending on the change in the color of the ground, and visual perception in this case remains fundamental.

Diurnal predator fish are sharper than others. These include pike, trout, and grayling. At night - pike perch, bream, catfish. They have light-sensitive elements in the retina of their eyes that perceive very weak light rays, which make it possible to distinguish the shadows of the victim in the dark.

Fish have adapted to navigate in constant darkness - in the deep-sea part of the ocean. The eyes, as a rule, are large and have a telescopic structure, allowing them to capture the slightest glimpses of light, usually emanating from the deep-sea inhabitants themselves.

Many of them have peculiar light organs - “flashlights”, built for convenience into some part of the body, for example, into the mouth. The hungry fish opens its mouth wide and the light automatically lights up. Small fish, attracted by the light, swim into the mouth, and the cunning predator immediately closes it. In some deep-sea fish, elongated processes emanating from the head “burn”, like antennas that perceive the voices of other underwater inhabitants - “friends” or “strangers”.

And others shine entirely, like Christmas trees New Year's toys, in the light of burning multi-colored garlands. The researchers, who descended in the submersible to great depths, into the utter kingdom of darkness, were amazed at the wonderful colorful world that opened up before them. Sparkling ghosts floated in front of them, shimmering in multicolor.

What beauty hides from human sight in the endless depths of the ocean! I would like for the underwater inhabitants to be just a peace-loving alien exploring this mysterious world.

Vladimir KORKOSH, ichthyologist, journalist (Kerch).

Can fish see in water? Agree that the question is rather strange, and the answer to it can only be in the affirmative. Another thing, how? Do they distinguish colors, can they perceive the above-water world, how does their vision depend on the transparency of the water, etc.?

Let's start with the fact that the visual acuity of fish depends entirely on the transparency of the water. Freshwater fish have poor vision. The water in ponds is always cloudy, and allows them to distinguish objects located at a distance of no more than two to three meters. For this reason, freshwater fish hunt and feed mainly at night. In clear water, the fish sees much further, up to 10 meters. But the outlines of objects are not clear, which is due to the special structure of the eye.

The eyes of fish resemble a camera, in which the lens acts as a lens, and the retina acts as a matrix on which the image is formed. The lens cannot change its shape, so fish see distant objects blurry. In order to somehow focus the image, it, like a camera lens, can bring the lens closer or move away from the retina, making the image more or less clear. Despite this, it is capable of distinguishing objects well at a distance of no more than one and a half meters. The viewing sector is quite wide and ranges from 150-170 degrees.

A person, as we know, sees very poorly in water, which is due to a completely different refraction of the sun's rays. The same goes for fish. She is able to perceive the surface world only in a distorted form. True, she sees objects at the zenith well. To understand how a fish sees the surface world, it is enough to immerse a mirror in the water at a slight angle and study the reflection that appears in it. However, some species of fish are blind out of water, while the same mudskipper sees perfectly well when on land.

Scientists have studied the vision of some species of fish and came to the conclusion that it depends on their living conditions, hunting methods, and the nature of the environment. Predatory fish have the sharpest vision. These include: pike perch, trout, perch, pike. Fish that lead a bottom lifestyle also have excellent vision. As we understand, visual acuity here is directly tied to the method of obtaining food. In addition, most predators are nocturnal, and it is extremely important for them to distinguish objects in complete darkness. For this purpose, the same bream uses a photosensitive secretion, which is secreted by its retina. The catfish has a slightly different night vision device, which is represented by nerve, light-sensitive fibers.

Marine deep-sea fish use luminous organs. These include, for example, photoblepharon. It illuminates the surrounding space with special “flashlights” located in the eye area. There are bacteria inside them that emit light. If desired, the fish can increase or decrease the intensity of the glow.

Fish eyes can be positioned differently. It all depends on their lifestyle. In bottom-dwelling fish such as flounder, they are located on top. Other representatives have them on both sides of their heads. In the fry of the same flounder, the eyes are located in the same way as in ordinary fish. And their body is not flat. The thing is that they live in the water column and feed on plankton. But, along with a change in lifestyle and the transition to a bottom existence, the shape of their body and the location of their eyes change. Despite this, the flounder's vision does not get worse. Her eyes can move independently of each other, which greatly expands their field of view.

In hammerhead fish, the eyes are located on both sides of the outgrowth, which is due to the peculiarities of its hunting. She hunts stingrays, which have a formidable weapon in the form of spikes on their tail. If the eyes had been positioned differently, the hammerhead fish would certainly have become their victim.