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Basic sensory organs in fish

Fishermen who devote a lot of time to their hobby know what determines the behavior of certain fish. They study the habits of peaceful and predatory fish. Based on existing knowledge, they build tactics for catching different fish at different times of the year.

In this article we will take a closer look at which sense organs are the main ones in fish. How they influence its behavior and what the fisherman should know in order to feel more confident on the pond.

What sense organs do fish have?

The sensory organs of fish, which directly influence their behavior in various situations, are the organs of vision, touch, smell, and the lateral line of hearing. With their help, fish determine the temperature of the environment, distinguish colors, determine the quality of water and the tastes and aromas of various objects and objects.

Tactile sensations have a great influence on the behavior of fish. The body of the fish is covered with many nerve endings, thanks to which it is easy for fish to navigate in the aquatic world.

Taste and smell in fish

Two openings on the frontal part of the head - the nostrils - are responsible for the sense of taste and smell in fish. Just like a human nose, fish have these holes to detect the smells and tastes of different objects. The olfactory organ in fish allows them to accurately determine the path to the spawning ground or find plant and animal food in the water.

The sense of smell is best developed in those fish that like to lead an active lifestyle at night and in places with low light. Such fish include burbot, catfish, bream, eel and, to some extent, carp. They distinguish salty, sweet, sour and bitter smells very well.

Taste buds are located inside the mouth, in the jaw area and on the whiskers of fish. If you look at how developed the oral organ is in bream and carp, and how easily they find food, then a lot becomes clear. For example, some fish species delay play away from their main habitats. These include, first of all, eels, salmon, roach, roach and crucian carp to some extent.

Interestingly, the fry, hatching from the eggs, cannot know where their natural habitat is. But they quickly find their way many hundreds of kilometers away and find themselves among their relatives. A striking example is salmon, which are born in the sea and then head home at high speed. Moreover, they find exactly the river where salmon live. They determine their native element by the composition of water and its taste. The olfactory organs are responsible for this. With their help, fish accurately determine for themselves the water in which they could live with the greatest comfort.

The same can be said about acne. These fish swim thousands of kilometers to lay eggs. And they easily find their native river. It is not surprising that at night these fish easily find worms and other food. By and large, they need vision for so many reasons.

The function of the organs of taste and smell is to determine the acidity of the environment and the amount of oxygen in the water. That is why the same bream or silver bream will not live in muddy areas of the reservoir. This water composition is not suitable for them, unlike crucian carp or crucian carp. Roughly speaking, if you artificially place fish in an environment that is unnatural for them, they will not take root there. The nostrils of fish are not connected to the nasopharynx. Therefore, taste buds are scattered throughout the body: on the antennae, fins and gills, as well as on the skin.

Eloquent examples are catfish and burbot, which love to hunt at night. These fish have very well developed organs responsible for tastes and smells: whiskers, fins and nostrils. With the help of whiskers and fins, burbot easily finds food in cold and dark times. Catfish do exactly the same thing, only in the warm season.

Most peaceful and predatory fish detect the electrical conductivity of water. The pits located on the body are responsible for this ability.

Fishermen should clearly understand that the sense organs discussed above affect the fish’s bite. Therefore, you can often find advice that you should not overdo it with flavorings. Humans and fish have a certain threshold of sensitivity to smells. When it passes, neither taste nor smell is felt. To understand how this can be, it is enough to inhale the aroma of a strong liquid concentrator with a pronounced odor. At first there is a smell, but then adaptation occurs. If you inhale a liquid with a stronger odor, you will not detect anything. The same thing happens with fish. If you throw bait with too strong a smell, the fish will not be able to distinguish it from the ground at the bottom by smell.

Vision in fish

It is easy to notice that every fish has a pair of eyes. Like other living things, the eyes are responsible for vision. This organ is differently adapted to water in different species of fish. The same burbot is practically blind. Catfish also do not have visual acuity. But the same pike or grayling are very well versed in both colors and shades. For them, vision is one of the main senses.

It has been established that fish are able to see well at a distance of 5 to 15 meters. Then only the silhouettes differ. This is due to the structural features of the lens and retina. In general, there is a clear relationship between the size of the eye and the ability to see. The more eyes, the farther their owner sees.

Using vision, fish detect prey or predators. Her eyes help her to hunt well, or to hide in time and not become an easy prey. Vision allows you to determine the size of objects, their shape, as well as find food and determine the distance between objects.

As for the ability to distinguish colors, they are better developed in predatory fish than in peaceful ones. Generally speaking, predators distinguish approximately the same number of colors as humans.

When talking about the objects that fish see, some nuances stand out. In the water she sees them just like a person. And she perceives objects located behind the water environment differently. Insects that lie on the surface of the water are clearly visible. Objects that are on the shore and people are visible blurry.

The fish does not see objects at the bottom so clearly, but determines their location accurately. The fish sees best objects that are located on the same level as it. Since her eyes are located on the side, her viewing angle is greater than that of those living organisms whose eyes are in the front.

Thus, it can be argued that the fish perceives objects that move on the surface of the water well. This explains the good performance when fishing with fly and spinning rods using surface baits. Predatory fish notice the color of baits and see outlines and various elements.

Tactile sensations of fish

Pisces are good at determining the properties of objects when touching them. They also determine the temperature of the water. Any mechanical effects on the fish’s organs are transmitted through nerve endings. With the help of these senses, fish maintain contact with the outside world. Anglers do not always take into account the peculiarities of the tactile sensations of fish and make mistakes when fishing.

What is meant by tactile sensitivity in fish? First of all, this is a reaction to touching objects, to their movements, vibration and contact with various parts of the fish’s body. This is one of the manifestations of touch - the ability to sense objects through touching them.

How can fish’s ability to tactilely sense objects affect fishing? This manifests itself in different ways. For example, if you covered the bait table, you created a spot on the bottom. If the color of the bait does not alarm peaceful fish, then they begin to try the food. At the same time, the sense of smell and touch is activated. When the fish tastes grains, large and small particles of food, as well as animal components, it also evaluates the hardness of the components. If the fish is not very hungry, it may spit out solid pieces.

When catching predatory fish with all kinds of bait, there are single bites, after which the bite stops. It is quite possible that the same silicone or spinner was not to the liking of the predator, and after trying it, he spat it out.

When assessing objects in contact with them, fish use a whole range of senses. Subcutaneous tissues and mucous membrane are the main informants of fish. Thanks to the sensations received, the fish can act differently in different situations. Let's mention water temperature again. The behavior and activity of fish largely depend on how warm or cool the water is. She can determine temperature with high accuracy using her senses of touch.

The ends of the trigeminal nerve are located on the head of the fish, and parts of the spinal nerves are located on the tail and fins. They cover the body of the fish. With their help, they sense various objects, as well as pain.

Organs of touch in fish

The organs of touch in fish are fins, whiskers, rostrum, and fin rays. With the help of these organs, fish form a clear picture of the surrounding world. Naturally, baits, baits, groundbaits are also evaluated by these bodies. In particular, whiskers and fins touch objects and thus evaluation occurs. Pisces can either accept or reject objects if they make them wary.

Spilling fish have differently developed whiskers. In catfish, burbot and barbel, the whiskers move due to developed muscles. With the help of the fish's whiskers, the taste and density of the fish are determined by an object at the bottom. A mustache is very helpful in cases where it is dark and visibility is limited. If the mustache is damaged for any reason, then it quickly loses its functions.

The rays of the fins are of great importance in the fish’s perception of the surrounding world. They are located in almost all fins: on the back and belly. In some species the rays are long, in others they are short. With their help, fish explore the bottom in search of animal food.

Using rays on the fins of fish, the density of food and its composition are determined. This is a very important point for anglers to consider. This is why there is a difference in bait for roach, crucian carp and bream. Depending on what fish we are targeting and what time of year, one or another bait composition is selected. The density and composition of the bait largely determines whether we will be able to place the fish on the spot or not.

All fish develop tubercles on their heads during spawning. During the spawning period, these tubercles are the main sensory organs.

The organs of touch and tactile senses are more important for bottom fish - bream, catfish, burbot, eel, rotan. It is these fish that have well-developed fins and whiskers. They help to navigate well in the bottom layer, find food and avoid predators.

Lateral line in fish

The lateral line is a kind of bridge between the sense of touch and hearing in fish. In some cases, it can effectively replace vision. The lateral line, like a thread, runs from the head to the tail on the side of the body.

At the head the line divides and its branches surround the eyes and are located along the gills and lower jaw. Inside this organ there is fluid, nerve fibers that are connected to the brain. Thanks to the lateral line, fish feel confident in muddy water and at night and react to changes in water level and the strength of the current. With its help, they determine the depth in different parts of the water area, as well as vibrations. Therefore, it is necessary to walk very carefully along the shore and behave quietly in the boat and when fishing in a wade.

Hearing in fish

Fish do not have ears. But this absolutely does not mean that the fish do not hear anything. Just the opposite. It’s just that the organ responsible for recording various sounds is located inside the body. This is a swim bladder. The principle of its operation is in many ways similar to how the human eardrum works. Vibrations of the walls of the bladder are signals that are transmitted through special channels to the brain. The swim bladder has a fairly large volume. Therefore, fish are able to hear sounds at different frequencies from great distances. That is why you should behave very carefully and not make loud sounds so as not to scare away the fish.

But not only the swim bladder is the organ of hearing in fish. The lateral line and skin help to sense sound vibrations. The first organ perceives low sounds, and the second - loud ones

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Like the vast majority of vertebrates, fish perceive light, sound, taste, smell, and touch from the environment. For this purpose, there are corresponding sensory organs of fish: eyes (organs of vision), ears (organs of hearing), taste, olfactory and tactile receptors (organs of taste, smell and touch). In addition, there is a sensory organ unique to fish - the lateral line. With its help, fish perceive water pressure, which allows them to determine the distance to objects, etc. Fish can also sense magnetic and electric fields.

All sense organs are connected to the nervous system, where the information received from them is processed.

Structure fish eyes differs from that, for example, in mammals. Both groups of organisms have a lens in the eye. But to bring clarity to the image in a fish’s eye, the distance from the retina to the lens changes, i.e. the lens moves. In mammals, the lens is capable of changing its shape. The fish lens is more round.

The eye is an important sensory organ of fish, allowing them to navigate well in space. The eyes of fish are designed in such a way that they see well only at close range (up to about 15 meters). But in water it is often impossible to see into the distance due to the low transparency of the water as a habitat. In deep-sea fish species that live where light rays do not penetrate, the eyes may be reduced (underdeveloped or absent altogether). In the dark, fish navigate using the lateral line organ.

The eyes of fish are large and mobile, and have an eyelid that cannot close. The location of the eyes on the sides of the head allows you to see almost the entire space around. Fish are able to distinguish colors.

The organ of hearing in fish is connected to the organ of balance.. Fish do not have an external ear. This is not necessary, since sound vibrations travel better in water (higher sound conductivity) and can penetrate through the bones of the fish’s skull, directly to the inner ear. It consists of three semicircular canals and sacs. The inner ear also includes an organ of balance (weighed small pebbles), which allows one to determine the top and bottom, i.e., determine the position of the body in space.

Fish not only hear sounds, but can also make them by rubbing various parts of the body (for example, teeth).

Fish sensory organs such as smell and taste are called chemical sense organs. Taste buds in fish are located not only in the mouth (tongue and other parts of the oral cavity), but also on the body. That is, the fish can taste it, for example, by touching the prey with its lip, or even with its head and side. The olfactory organs are located deep in the nostrils. Using the perception of smell, fish search for food, and transitional fish also determine spawning sites (based on the chemical composition of the waters where they were born).

Touch receptors make it possible to feel touch. They are scattered throughout the body of the fish. Some fish have tactile antennae on their heads (for example, catfish).

Lateral line organ- This is a special sensory organ of fish. Most often it is a canal on the sides of the body. In the depths of this channel there are nerve endings. And the channel communicates with the external environment through openings, usually visible to the naked eye as dotted lines on the scales on the sides of the fish. Water is poured into these holes, and the fish can feel its pressure. This allows her to determine the distance to objects, the speed and direction of the current, and navigate the flock.

Characteristic features of chordates:

• three-layer structure;
• secondary body cavity;
• the appearance of a chord;
• conquest of all habitats (water, land and air).

During evolution, organs improved:

• movements;
• reproduction;
• breathing;
• blood circulation;
• digestion;
• feelings;
• nervous (regulating and controlling the work of all organs);
• body coverings changed.

Biological meaning of all living things:

general characteristics

live— freshwater bodies of water; in sea water.

Lifespan- from several months to 100 years.

Dimensions- from 10 mm to 9 meters. (Fish grow all their lives!).

Weight- from a few grams to 2 tons.

Fish are the most ancient proto-aquatic vertebrates. They are able to live only in water; most species are good swimmers. The class of fish in the process of evolution was formed in the aquatic environment, and the characteristic structural features of these animals are associated with it. The main type of translational movement is lateral wave-like movements due to contractions of the muscles of the tail or the whole body. The pectoral and ventral paired fins serve as stabilizers, used to raise and lower the body, turn stops, slow smooth movement, and maintain balance. The unpaired dorsal and caudal fins act as a keel, giving stability to the fish's body. The mucous layer on the surface of the skin reduces friction and promotes rapid movement, and also protects the body from pathogens of bacterial and fungal diseases.

External structure of fish

Side line

The lateral line organs are well developed. The lateral line perceives the direction and strength of water flow.

Thanks to this, even when blinded, it does not bump into obstacles and is able to catch moving prey.

Internal structure

Skeleton

The skeleton is the support for well-developed striated muscles. Some muscle segments were partially rebuilt, forming muscle groups in the head, jaws, gill covers, pectoral fins, etc. (ocular, epibranchial and hypobranchial muscles, muscles of paired fins).

swim bladder

Above the intestines is a thin-walled sac - a swim bladder, filled with a mixture of oxygen, nitrogen and carbon dioxide. The bladder formed from an outgrowth of the intestine. The main function of the swim bladder is hydrostatic. By changing the pressure of gases in the swim bladder, the fish can change the depth of its dive.

If the volume of the swim bladder does not change, the fish is at the same depth, as if hanging in the water column. When the volume of the bubble increases, the fish rises. When lowering, the reverse process occurs. The swim bladder of some fish can participate in gas exchange (as an additional respiratory organ), serve as a resonator when producing various sounds, etc.

Body cavity

Organ system

Digestive

The digestive system begins with the mouth. Perch and other predatory bony fish have numerous small, sharp teeth on their jaws and many bones in their mouths that help them capture and hold prey. There is no muscular tongue. Through the pharynx into the esophagus, food enters the large stomach, where it begins to be digested under the influence of hydrochloric acid and pepsin. Partially digested food enters the small intestine, where the ducts of the pancreas and liver empty. The latter secretes bile, which accumulates in the gallbladder.

At the beginning of the small intestine, blind processes flow into it, due to which the glandular and absorptive surface of the intestine increases. Undigested residues are excreted into the hindgut and removed through the anus.

Respiratory

The respiratory organs - gills - are located on four gill arches in the form of a row of bright red gill filaments, covered on the outside with numerous thin folds, increasing the relative surface of the gills.

Water enters the fish's mouth, is filtered through the gill slits, washes the gills, and is thrown out from under the gill cover. Gas exchange occurs in numerous gill capillaries, in which blood flows towards the water washing the gills. Fish are able to absorb 46-82% of oxygen dissolved in water.

Opposite each row of gill filaments are whitish gill rakers, which are of great importance for the nutrition of fish: in some they form a filtering apparatus with a corresponding structure, in others they help retain prey in the oral cavity.

Blood

The circulatory system consists of a two-chambered heart and blood vessels. The heart has an atrium and a ventricle.

excretory

The excretory system is represented by two dark red ribbon-like buds, lying below the spinal column almost along the entire body cavity.

The kidneys filter waste products from the blood in the form of urine, which passes through two ureters into the bladder, which opens outward behind the anus. A significant part of the toxic decomposition products (ammonia, urea, etc.) are excreted from the body through the gill filaments of fish.

Nervous

The nervous system looks like a hollow tube thickened in front. Its anterior end forms the brain, which has five sections: the forebrain, diencephalon, midbrain, cerebellum and medulla oblongata.

The centers of different sense organs are located in different parts of the brain. The cavity inside the spinal cord is called the spinal canal.

Sense organs

Taste buds, or taste buds, are located in the mucous membrane of the oral cavity, on the head, antennae, elongated fin rays, and scattered over the entire surface of the body. Tactile corpuscles and thermoreceptors are scattered in the superficial layers of the skin. Receptors of electromagnetic sense are concentrated mainly on the head of fish.

Two big eyes are located on the sides of the head. The lens is round, does not change shape and almost touches the flattened cornea (therefore fish are myopic and see no further than 10-15 meters). In most bony fishes, the retina contains rods and cones. This allows them to adapt to changing light conditions. Most bony fish have color vision.

Hearing organs represented only by the inner ear, or membranous labyrinth, located on the right and left in the bones of the back of the skull. Sound orientation is very important for aquatic animals. The speed of sound propagation in water is almost 4 times greater than in air (and is close to the sound permeability of fish body tissues). Therefore, even a relatively simple organ of hearing allows fish to perceive sound waves. The hearing organs are anatomically connected to the balance organs.

A series of holes stretches along the body from the head to the caudal fin - lateral line. The holes are connected to a channel immersed in the skin, which branches strongly on the head and forms a complex network. The lateral line is a characteristic sensory organ: thanks to it, fish perceive water vibrations, the direction and strength of the current, and waves that are reflected from various objects. With the help of this organ, fish navigate in water flows, perceive the direction of movement of prey or predators, and do not bump into solid objects in barely transparent water.

Reproduction

Fish breed in water. Most species lay eggs, fertilization is external, sometimes internal, and in these cases viviparity is observed. The development of fertilized eggs lasts from several hours to several months. The larvae that emerge from the eggs have a remnant of the yolk sac with a supply of nutrients. At first they are inactive and feed only on these substances, and then they begin to actively feed on various microscopic aquatic organisms. After a few weeks, the larva develops into a small fish covered with scales and resembling an adult fish.

Fish spawn at different times of the year. Most freshwater fish lay their eggs among aquatic plants in shallow water. The fertility of fish, on average, is much higher than the fertility of terrestrial vertebrates; this is associated with a large loss of eggs and fry.

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 their 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 tree decorations, 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).