Organ of vision
Vision is one of the main sense organs in fish. The eye consists of a round shaped lens that has a hard structure. It is located near the cornea and allows you to see at a distance of up to 5 m at rest, maximum vision reaches 10-14 m.
Structure of a fish's eye
The lens captures many light rays, allowing you to see in several directions. Often the eye has an elevated position, so it receives direct rays of light, oblique, as well as from above, below, and from the sides. This significantly expands the fish’s field of vision: in the vertical plane up to 150°, and in the horizontal plane up to 170°.
Monocular vision - the right and left eyes receive a separate image. The eye consists of three membranes: the sclera (protects from mechanical damage), the vascular (supplies nutrients), and the retinal (provides light perception and color perception due to the system of rods and cones).
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.
Hearing organ
The hearing aid (inner ear or labyrinth) is located in the back of the skull and includes two compartments: the upper oval and round lower sacs. The oval sac contains three semicircular canals - this is an organ of balance; endolymph flows inside the labyrinth; in cartilaginous fish it connects with the environment through the excretory duct; in bony fish it ends blindly.
The organ of hearing in fish is combined with the organ of balance.
The inner ear is divided into three chambers, each containing the otolith (part of the vestibular apparatus that responds to mechanical stimulation). The auditory nerve ends inside the ear, forming hair cells (receptors); when the position of the body changes, they are irritated by the endolymph of the semicircular canals and help maintain balance.
The perception of sounds is carried out due to the lower part of the labyrinth - a round sac. Fish are able to detect sounds in the range of 5Hz – 15kHz. The hearing aid includes the lateral line (allows you to hear low-frequency sounds) and the swim bladder (acts as a resonator, connected to the inner ear through the Weberian apparatus, consisting of 4 bones).
Fish are myopic animals, they often move in muddy water, with poor lighting; some individuals live in the depths of the sea, where there is no light at all. What sense organs and how do they allow one to navigate in water under such conditions?
Fins - taste organs
Experiments show that fish distinguish between sweet, bitter, sour and salty, four taste qualities that are also perceived by humans. For example, many fish spit out food soaked in quinine or wormwood bitters, as if the bitter taste was “unpleasant” to them. And they treat sweets very well. Thus, sea burbot readily eats meat soaked in sugar syrup.
As is known, the water of different parts of the seas and oceans has different salinity. And the fact that fish can distinguish between salinity sometimes explains their ability to navigate during long-distance migrations. There are no designated roads underwater, and at the same time, fish usually travel along very specific routes. It is possible that they really recognize their path “by taste”.
The location of the taste organs in fish is not limited to the mouth, as in most animals. Fish live in an aquatic environment, and taste substances can be important to them not only when they enter the mouth, but also when they simply touch the outer surface of the body. In catfish, cod fish, and carp fish, taste buds are located, for example, on the whiskers. They are also found on elongated fin rays, like in burbot, whiting and other fish.
In this regard, a very interesting fish with large fins is the sea cock, or three hundred. She seems to walk along the bottom on some thin strange fingers - the rays of the pectoral fins. It turns out that these free fin rays serve the gurnard not only for support. They also have taste sensitivity. Having felt with them the prey hidden at the bottom, three hundred immediately grabs it.
Many fish have taste buds literally throughout their body. Such fish are able to find food by touching it with any part of the body. They can also feed at night. Taste, as can be seen, helping the fish to navigate and find food under water, turns out to be a rather comprehensive sense for it, and the surrounding world is largely represented for the fish in the form of taste sensations.
Smell and taste . The organs of smell in fish are the nostrils located on both sides of the head. By passing water in which certain substances are dissolved through the nostrils, the fish catches their odors. The sense of smell helps her search for food and recognize enemies. It is believed that salmon use their scent to find spawning grounds in the rivers where they hatched.
Despite the fact that only one tenth of one percent of sound vibrations penetrates from air into water, you should speak quietly. If you do this loudly, you can again cause vibrations in the soil, which will be transmitted to the water.
Lateral line organs . This is what scientists call the feeling kidneys of fish, which are sensitive cells with hairs located in a gelatinous protrusion that sways easily under the influence of water currents. In most bony fishes, the sensory buds are located in closed canals and form a lateral line that can extend onto the head. The canals are filled with mucus, into which the gelatinous protrusions of the kidneys protrude. The channels are connected to the external environment by small holes in the scales.
With the help of this sensory organ, fish determine the direction, strength of current and waves, and the size of objects moving in the water. When visibility is poor, the lateral line replaces the fish's vision.
Smell and taste . The organs of smell in fish are the nostrils located on both sides of the head. By passing water in which certain substances are dissolved through the nostrils, the fish catches their odors. The sense of smell helps her search for food and recognize enemies. It is believed that salmon use their scent to find spawning grounds in the rivers where they hatched.
Taste buds of fish are located in the mouth, on the antennae, gills, head, fin rays and on the surface of the body. Fish perceive different shades of taste: sweet, bitter, salty, sour.
Touch . Not all fish have organs of touch. They are mainly the antennae at the end of the lips. Some fish have only one antennae, others have pairs. Antennae help fish search for food at the bottom.
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The organs of touch are clusters of sensory cells (tactile bodies) scattered over the surface of the body. They perceive the touch of solid objects (tactile sensations), water pressure, as well as temperature changes (heat-cold) and pain.
In fish, as in other vertebrates, they are located in the front part of the head and are represented by paired olfactory (nasal) sacs (capsules) that open outward with nostril openings. The bottom of the nasal capsule is lined with folds of epithelium, consisting of supporting and sensory cells (receptors). The outer surface of the sensory cell is equipped with cilia, and the base is connected to the endings of the olfactory nerve. The olfactory epithelium contains numerous cells that secrete mucus.
The size of the nostrils is related to the lifestyle of the fish: in active fish they are small, since during fast swimming the water in the olfactory cavity is quickly renewed; In sedentary fish, on the contrary, the nostrils are large; they allow a larger volume of water to pass through the nasal cavity, which is especially important for poor swimmers, in particular those living near the bottom.
In experiments, when the nasal cavity of these fish was washed with water from their native spawning ground, a strong electrical reaction occurred in the olfactory bulb of the brain. The reaction to water from downstream tributaries was weak, and the receptors did not react at all to water from other spawning grounds.
The olfactory receptor of fish, in addition to chemical ones, is capable of perceiving mechanical influences (flow jets) and temperature changes.
They are represented by taste buds, formed by clusters of sensory (and supporting) cells. The bases of the sensory cells are intertwined with the terminal branches of the facial, vagus and glossopharyngeal nerves.
The perception of chemical stimuli is also carried out by the free nerve endings of the trigeminal, vagus and spinal nerves. The perception of taste by fish is not necessarily associated with the oral cavity, since taste buds are located both in the oral mucosa and on the lips, and in the pharynx, on the antennae, gill filaments, fin rays and throughout the surface of the body, including the tail.
Catfish perceive taste mainly with the help of their whiskers: it is in their epidermis that clusters of taste buds are concentrated. In the same individual, the number of taste buds increases as the body size increases. Pisces distinguish the taste characteristics of food: bitter, salty, sour, sweet. In particular, the perception of salinity is associated with a pit-shaped organ located in the oral cavity.
The sensitivity of the taste organs in some fish is very high: for example, the cave fish Anoptichthys, being blind, sense a glucose solution at a concentration of 0.005%.
Lateral line sensory organs
Branches of the lateral line are also present on the head. At the bottom of the canal (in groups there are sensory cells with cilia. Each such group of receptor cells, together with the nerve fibers in contact with them, forms the organ itself - a neuromast. Water flows freely through the canal, and the cilia sense its pressure. In this case, nerve impulses of different frequencies arise. Organs The lateral line is connected to the central nervous system by the vagus nerve.
The ability to catch waves reflected from living and inanimate objects is very important for deep-sea fish, since in the darkness of great depths the usual visual perception of surrounding objects and communication between individuals is impossible.
It is assumed that the waves created during the mating games of many fish, perceived by the lateral line of the female or male, serve as a signal for them. The function of the skin sense is performed by the so-called skin buds - cells found in the integument of the head and antennae, to which nerve endings are suitable, but they are of much less importance.
The organs of touch are clusters of sensory cells (tactile bodies) scattered over the surface of the body. They perceive the touch of solid objects (tactile sensations), water pressure, as well as temperature changes (heat-cold) and pain.
There are especially many sensory skin buds in the mouth and lips. In some fish, the function of the organs of touch is performed by the elongated rays of the fins: in gourami this is the first ray of the pelvic fin, in the trigla (guinea cock) the sense of touch is associated with the rays of the pectoral fins, feeling the bottom, etc. In inhabitants of turbid waters or bottom fish, the most active at night, the largest number of sensory buds are concentrated on the antennae and fins. However, in catfish, the whiskers serve as receptors for taste, not touch.
Fish apparently feel mechanical injuries and pain less than other vertebrates: sharks that have attacked prey do not react to blows to the head with a sharp object; During operations, fish are often relatively calm, etc.
Thermoreceptors. They are the free endings of sensory nerves located in the surface layers of the skin, with the help of which fish perceive water temperature. There are receptors that perceive heat (thermal) and cold (cold). Points of heat perception are found, for example, on the pike’s head, and cold perception points are found on the surface of the body. Bony fish detect temperature changes of 0.1–0.4°C.
Electric sense organs
The importance of vision is not so great in aquatic inhabitants compared to terrestrial ones.
It is generally accepted that since fish are at a lower level of organization than mammals, their sense organs are also more primitive. Actually this is not true!
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.
Vision.
The importance of vision is not so great in aquatic inhabitants compared to terrestrial ones.
This is due, firstly , to the fact that with increasing depth, illumination decreases significantly, secondly , very often fish are forced to live in conditions of low water transparency, and 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.
Hearing.
Oddly enough, fish have perfectly developed hearing , despite their lack of 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 against each other, vibrating various parts of the body and thus carrying out sound communication.
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.
Taste.
Flavoring substances are also perfectly distinguishable 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.
Touch.
Fish have ordinary mechanical receptors , which, like taste organs, are located mainly at the tips of their antennae, and are also scattered over the skin. However, in addition to this, fish have a completely unique receptor organ - the 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.
Side line
First of all, this is the lateral line - the main sensory organ in fish. It is a channel that runs under the skin along the entire body and branches in the head area, forming a complex network. It has holes through which it communicates with the environment. Inside there are sensitive kidneys (receptor cells) that perceive the slightest changes around.
This way they can determine the direction of the current, navigate the area at night, and sense the movement of other fish, both in a school and of predators approaching them. The lateral line is equipped with mechanoreceptors; they help aquatic inhabitants to dodge pitfalls and foreign objects, even in poor visibility.
The lateral line can be complete (located from the head to the tail), incomplete, or can be completely replaced by other developed nerve endings. If the lateral line is injured, the fish will no longer be able to survive for long, which indicates the importance of this organ.
The lateral line of fish is the main organ of orientation
Aqualover
How do fish feel?
The answer to this question has not yet been fully clarified; for example, it has not yet been reliably determined whether fish feel pain, and if so, how much. But, nevertheless, knowledge of the anatomy of fish, the structure and functions of their receptors allows us to draw certain conclusions about the fish’s sensory organs: first of all, smell, taste, spatial orientation, vision, hearing. Like humans, fish have all senses that are closely interconnected. Fish receptors register stimuli of both physical and chemical nature: pressure, sound, temperature, color, electric and magnetic fields, smell, taste.
The sense of smell is one of the most important ways in which fish perceive the world. Experienced fishermen always sprinkle the bait on the hook with aromatic bait: many fish are very sensitive to odors. The fish nose has special olfactory sacs with cilia. By narrowing and expanding these bags, the fish sniffs. Thanks to their sense of smell, fish distinguish food, find their school, partners during spawning, predators and prey. In addition, in some situations, fish can release “chemical signals” into the water (for example, when there is danger), which are also recognized by other fish. This is a very significant factor for fish living in turbid water, since collecting information through touch or sounds is difficult there, and fish actively use their sense of smell.
The sense of smell is especially well developed in migratory swimmers. For example, juvenile sockeye salmon use their sense of smell to distinguish the water of different lakes, solutions of various amino acids, and the concentration of calcium in water; The European eel, migrating from Europe to spawning grounds located in the Sargasso Sea, can determine the water of any of the reservoirs encountered on its way. In general, “chemical olfactory signals” play an important function in the life of fish: they come in different types. For example, signals “for our own” are called pheromones. The relationships between different fish species are determined by kairomones and allomones. Kairomones carry information useful to the species receiving the signal. Allomones, on the other hand, produce a behavioral response that is beneficial to the species that produced the signal.
The fish has four nostrils in its nose, which are abundantly equipped with sensitive cells that perceive odors. Substances dissolved in water, entering the nostrils, irritate these cells, transmitting a signal to the brain about a particular smell. Water circulates freely through the cavities of the nostrils thanks to special valves located in them. At the same time, the sense of smell in different species of fish is developed differently. However, smell is usually much more important for fish than vision.
Fish also have taste buds . Fish perfectly distinguishes bitter from sweet or salty. The taste perceptions of fish are different from the olfactory lobes of the brain! The taste buds of fish, which are sensitive cells, are located in the mouth (oral buds of the fish), on the lips, cheeks, mustache, as well as on the sides and head.
A characteristic and very important sensory organ for fish is the lateral line (also present in aquatic amphibians). The lateral line is a kind of sensor for movements and vibrations of water. With its help, for example, predators perfectly sense the slightest movements of a potential victim, and the victim, on the contrary, senses a hidden predator. And also thanks to this “sensor”, fish navigate in the underwater space, avoid stationary obstacles, determine the location of food, the direction of the current, etc.
The lateral line is a channel passing through the entire body and communicating with water through holes in the scales. It contains very sensitive cells that respond to atmospheric pressure and inform the brain about its changes. This sensitive channel is also called the seismosensory organ. Sensitive organs that respond to pressure fluctuations in water are also found on the head, jaws and gill covers of fish. The lateral line is connected to the Central Nervous System by the vagus nerve.
The lateral line can be complete: it runs along the entire body of the fish; incomplete, and it may also be absent (for example, in herring). However, fish that lack a lateral line have other, well-developed channels of nerve endings. Damage to the lateral line of a fish can very quickly cause its death.
Electroreception
Electroreception is a sensory organ of cartilaginous fish and some bony fish (electric catfish). Sharks and rays sense electric fields using ampullae of Lorenzini - small capsules filled with mucous contents and lined with specific sensitive cells, located in the head area and communicate with the surface of the skin using a thin tube.
Very susceptible and capable of sensing weak electric fields (the reaction occurs at a voltage of 0.001 mKV/m).
Thus, electrosensitive fish can track down prey hidden in the sand thanks to the electric fields that are created when muscle fibers contract during breathing.
The lateral line and electrosensitivity are sensory organs characteristic only of fish!
Olfactory organ
The sense of smell is carried out using cilia located on the surface of special sacs. When the fish smells the smell, the sacs begin to move: they contract and expand, capturing odorous substances. The nose includes 4 nostrils, sent out by many sensory cells.
With their sense of smell they easily find food, relatives, and a partner for the spawning period. Some individuals are able to signal danger by releasing substances to which other fish are sensitive. It is believed that the sense of smell for aquatic inhabitants is more important than vision.
Sense organs in fish
