Internal structure of perch: what is perch.

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Biology Animals 7th grade River perch External and internal structure The presentation was prepared by: teacher of biology and chemistry Merkulova E.V. School No. 26, Ryazan

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Systematic position of the river perch Type Chordata Subtype Cranial or Vertebrates Superclass Fishes Class Bony fishes Subclass Ray-finned Superorder Teleosts Order Perciformes Family Perch Genus Freshwater Perch Species River Perch

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What characteristics are common to chordates? General signs chordates: the body is bilaterally symmetrical; have axial skeleton- notochord, a dense supporting cord, in skullless animals it remains throughout life, in vertebrates it is replaced during the process individual development a spine consisting of individual vertebrae; the through intestine is located under the chord; central nervous system in the form of a neural tube located above the notochord, on the dorsal side of the body; from the anterior part of the digestive tube - the pharynx, organs develop respiratory system(gills or lungs); the circulatory system is closed; the heart is located on the ventral side of the body, under the digestive canal.

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River perch is a common inhabitant fresh water. In the USSR it is found in rivers and lakes almost everywhere, except Far East. Water exhibits noticeable resistance to bodies moving in it. Perch, like many other fish, has a streamlined shape - this helps it move quickly in the water. The perch's head smoothly transitions into the body, and the body into the tail. At the pointed front end of the head there is a mouth with lips that can open wide. On the top of the head two pairs of small holes are visible - nostrils leading to the olfactory organ. On its sides there are two big eyes. Fins. Bending the laterally flattened body and tail first to the right and then to the left, the perch moves forward. When swimming, fins play an important role. Each fin consists of a thin membrane of skin, which is supported by bony fin rays. When the rays spread out, the skin between them tightens and the surface of the fin increases.

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The perch has two dorsal fins: a large one in front and a smaller one in the back. Number of dorsal fins different types fish may vary. At the end of the tail there is a large two-lobed caudal fin, and on the underside of the tail there is an anal fin. All these fins are unpaired. Fish also have paired fins - there are always two pairs of them. The pectoral paired fins (front pair of limbs) are placed on the sides of the body behind the head of the perch! ventral paired fins (rear pair of limbs) - on the underside of the body. Main role When moving forward, the caudal fin plays. The paired fins are important for turning, stopping, moving forward slowly, and maintaining balance. The dorsal and anal fins give the fish body stability when moving forward and making sharp turns.

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Covers and coloring. The body of the perch is covered with bony scales. Each scale with its front edge is immersed in the skin, and with its rear edge it overlaps the scales of the next row. Together they form a protective cover - scales that do not interfere with body movements. As the fish grows, the scales also increase in size and can be used to determine the age of the fish. The outside of the scales is covered with a layer of mucus, which is secreted by the skin glands. Mucus reduces friction between the fish's body and water and serves as protection against bacteria and mold. Like most fish, the belly of the perch is lighter than that of the epine. From above, the back to a certain extent merges with the dark background of the bottom. From below, the light belly is less noticeable against the light background of the water surface. The body color of a perch depends on environment: In forest lakes with a dark bottom it has dark color, sometimes even completely black perches are found there. Perches with light and bright colors live in reservoirs with a light sandy bottom. Perch often hides in thickets. Here the greenish color of its sides with vertical dark stripes makes the perch invisible. This protective coloring helps him hide from enemies and better watch over his prey. A narrow dark lateral line runs along the sides of the perch’s body from head to tail.

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The skeleton of a perch consists of large quantity bones. Its basis is the spine, which stretches along the entire body of the fish from the head to the caudal fin. The spine is formed a large number vertebrae (perch has 39-42). Fish and other animals whose skeleton is based on the spine are called vertebrates, and all other animals are called invertebrates. When a perch develops in the egg, a notochord appears in the place of its future spine. Later, vertebrae appear around the notochord. In adult perch, only small cartilaginous remains between the vertebrae are preserved from the notochord. In beluga, sturgeon and some other species of fish, as well as in the lancelet, the notochord is maintained throughout life. Each vertebra consists of a body and a superior arch ending in a long superior process. Together, the upper arches form the spinal canal, in which the spinal cord is located. In the trunk section of the body, the ribs are attached to the vertebrae from the sides. There are no ribs in the caudal region; each vertebra located in it is equipped with a lower arch ending in a long lower process.

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In front, the skeleton of the head, the skull, is firmly articulated with the spine. There is also a skeleton in the fins. In paired pectoral fins, the skeleton of the fins is connected to the spine by the bones of the shoulder girdle. The bones connecting the skeleton of the paired pelvic fins to the spine are not developed in the perch. The skeleton has great importance: it serves as a support for the muscles and protection for internal organs. Musculature of fish. Under the skin of fish there are muscles attached to the bones that form the musculature. The strongest of them are located on the dorsal side of the body and in the tail. The contraction and relaxation of muscles causes the fish's body to flex, helping it move through the water. The head and fins contain muscles that move the jaws, gill covers and fins.

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Body cavity. In the body section of the fish, under the spine, there is a large body cavity in which the internal organs are located. Digestive system. Perch is a predator. It feeds on a variety of aquatic animals, including other species of fish. The perch captures and holds its prey with sharp teeth sitting on its jaws. After swallowing, food passes through the pharynx and esophagus into the stomach. Perch swallows its prey whole, and therefore its stomach has the ability to greatly stretch. Microscopic glands in the walls of the stomach secrete gastric juice. Under its influence, food begins to be digested. The partially modified food then passes into the small intestine, where it is acted upon by the digestive juice of the pancreas and bile coming from the liver. The supply of bile accumulates in gallbladder. Nutrients penetrate through the walls into the blood, and undigested residues enter the hindgut and are thrown out.

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Swim bladder. In perch, like in many other fish, the intestine has a special thin-walled outgrowth filled with a mixture of gases - a swim bladder. In an adult perch, the connection between the bladder and the intestine is lost, but in its larvae and in some other fish (for example, roach or carp), a small tube remains between the intestine and the bladder for the rest of its life. As the fish descends into the depths, the bubble decreases in volume and the density of the fish increases. This promotes rapid immersion. When floating, the volume of the bubble increases and the fish becomes relatively lighter. As long as the fish is at the same depth, the volume of the bubble does not change. This allows the fish to remain motionless, as if hanging in the water column.

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Respiratory system. Fish breathe oxygen dissolved in water. The fish constantly swallows water. From oral cavity water passes through the gill slits, which permeate the walls of the pharynx, and washes the respiratory organs - the gills. In perch, they consist of gill arches, on each of which there are bright red gill filaments on one side and whitish gill rakers on the other. Gill rakers are a filtering apparatus: they prevent prey from slipping out through the gill slits. The gill filaments are penetrated by the smallest blood vessels - capillaries. Through the thin walls of the gill filaments, oxygen dissolved in water penetrates into the blood, and carbon dioxide is removed from the blood into the water. If there is little oxygen, then the fish rise to the surface and begin to take in air with their mouths. Prolonged exposure to water containing little oxygen can cause fish death. In winter, there is sometimes a lack of oxygen under ice in reservoirs. Then the fish die. To prevent freezing, it is useful to make holes in the ice. Dried gill filaments cannot allow oxygen and carbon dioxide to pass through. Therefore, fish taken out of the water quickly die. On the outside, the delicate gills are covered with protective gill covers.

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Circulatory system closed fish. It consists of the heart and blood vessels. The vessels leaving the heart are called arteries; vessels that bring blood to the heart are veins. The heart of the fish is two-chambered. It consists of the atrium and ventricle, the muscular walls of which alternately contract. From the atrium, blood is pushed into the ventricle, and from it into a large artery - the abdominal aorta. Valves prevent blood from flowing back. The abdominal aorta goes to the gills, and smaller vessels extend from it to the right and left. The blood flowing in them is dark in color, saturated with carbon dioxide and is called venous. In the gills, the vessels branch into capillaries. The blood flowing in them is freed from carbon dioxide and saturated with oxygen. In the vessels extending from the gills, scarlet, oxygenated arterial blood flows. It gathers into the dorsal aorta, which runs along the body under the spine. In the caudal region, the dorsal aorta passes through the lower vertebral arches. From the dorsal aorta branch smaller arteries that branch in various organs to capillaries. Through the walls of these capillaries, oxygen and nutrients enter the tissues, and from them carbon dioxide and other waste products enter the blood. Gradually, the scarlet arterial blood darkens and turns into venous blood, containing a lot of carbon dioxide and little oxygen. Venous blood collects in the veins and flows through them into the atrium. Thus, the blood continuously circulates in one closed circulatory circle

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Excretory system. In the upper part of the body cavity there are two ribbon-shaped red-brown buds. In the capillaries of the kidneys, waste products are filtered from the blood, forming urine. It passes through two ureters into the bladder, which opens outward behind the anus. NERVOUS SYSTEM, SENSE ORGANS AND BEHAVIOR OF FISH

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Sense organs allow fish to navigate their environment well. Important role at the same time the eyes play. Perch sees only relatively close range, he distinguishes the shape and color of objects. In front of each eye of the perch there are two openings - nostrils, leading to a blind sac with sensitive cells. This is the organ of smell. The hearing organs are not visible from the outside; they are located on the right and left in the bones of the back of the skull. Due to the density of water, sound waves are well transmitted through the bones of the skull and are perceived by the hearing organs of the fish. Experiments have shown that fish can hear the steps of a person walking along the shore, the ringing of a bell, a gunshot. Taste organs - sensitive cells - are located in perch, like in other fish, not only in the oral cavity, but also scattered over the entire surface of the body. There are also tactile cells there. Some fish (for example, catfish, carp, cod) have tactile antennae on their heads.

Fish body cavity

In the body section of the fish, under the spine, there is a large body cavity in which the internal organs are located.

Drawing: Internal structure river perch. Digestive and excretory system

The digestive system of fish using the example of river perch

Perch is a predator. It feeds on a variety of aquatic animals, including other species of fish. The perch captures and holds its prey with sharp teeth sitting on its jaws. After swallowing, food passes through the pharynx and esophagus into the stomach. Perch swallows its prey whole, and therefore its stomach has the ability to greatly stretch. Microscopic glands of the stomach walls secrete gastric juice. Under its influence, food begins to be digested. The partially modified food then passes into the small intestine, where it is acted upon by the digestive juice of the pancreas and bile coming from the liver. The supply of bile accumulates in gallbladder. Nutrients penetrate through the walls into the blood, and undigested residues enter the hindgut and are thrown out.

The respiratory system of fish using the example of river perch

Fish breathe oxygen dissolved in water, constantly swallowing water. From the oral cavity, water passes through gill slits, which permeate the walls of the pharynx, and washes the respiratory organs - gills. In perch, they consist of gill arches, on each of which they sit on one side bright red gill filaments, and on the other - whitish gill rakers. Gill rakers are a filtering apparatus: they prevent prey from slipping out through the gill slits. The gill filaments are penetrated by the smallest blood vessels - capillaries. Through the thin walls of the gill filaments, oxygen dissolved in water penetrates into the blood, and carbon dioxide is removed from the blood into the water.

If there is little oxygen, then the fish rise to the surface and begin to take in air with their mouths. Prolonged exposure to water containing little oxygen can cause fish death. In winter, there is sometimes a lack of oxygen under ice in reservoirs. Then the fish die. To prevent freezing, it is useful to make holes in the ice.

Dried gill filaments cannot allow oxygen and carbon dioxide to pass through. Therefore, fish taken out of the water quickly die. On the outside, the delicate gills are covered with gill covers.

The circulatory system of fish using the example of river perch

Figure: Internal structure of river perch. Circulatory system

Figure: Structure and function of river perch gills

The circulatory system of fish is closed. It consists of the heart and blood vessels. The vessels leaving the heart are called arteries, vessels that bring blood to the heart - veins. The heart of the fish is two-chambered. It consists of atria And ventricle, the muscular walls of which alternately contract. From the atrium, blood is pushed into the ventricle, and from it into large artery - abdominal aorta. Valves prevent blood from flowing back. The abdominal aorta goes to gills, in them the blood is dark in color, saturated with carbon dioxide and is called venous. In the gills the vessels branch into capillaries. The blood flowing in them is freed from carbon dioxide and saturated with oxygen. In the vessels extending from the gills, a scarlet, saturated with oxygen flows. rterial blood. She's going to dorsal aorta, which stretches along the body under the spine. In the caudal region, the dorsal aorta passes through the lower vertebral arches.

From the dorsal aorta branch smaller arteries that branch in various organs to capillaries. Through the walls of these capillaries, oxygen and nutrients enter the tissues, and from them carbon dioxide and other waste products enter the blood.

Gradually, the scarlet arterial blood darkens and turns into venous blood, containing a lot of carbon dioxide and little oxygen. Venous blood collects in the veins and flows through them into the atrium. Thus, the blood continuously circulates one at a time closed circle of blood circulation.

Excretory system of fish using the example of river perch

In the upper part of the body cavity lie two ribbon-shaped red-brown kidneys. In the capillaries of the kidneys, waste products are filtered from the blood, forming urine. It passes through two ureters to bladder, opening outwards behind anus.

Metabolism of fish

In the body of a fish, like all other living organisms, processes take place that ensure their growth, vital activity, reproduction, constant contact and exchange with external environment. The combination of all these processes is called the metabolism of living organisms.

Nervous system of fish

Figure: Internal structure of river perch. Nervous system

Fish spinal cord

The central nervous system of fish, like that of the lancelet, has the shape of a tube. Her posterior region is spinal cord located in the spinal canal formed by upper bodies and vertebral arches. From the spinal cord between each pair of vertebrae, nerves extend to the right and left that control the functioning of the muscles of the body and fins and organs located in the body cavity.

Signals of irritation are sent along nerves from sensory cells on the fish’s body to the spinal cord.

Fish brain

The anterior part of the neural tube of fish and other vertebrates is modified into brain, protected by the bones of the skull. The vertebrate brain has different divisions: forebrain, diencephalon, midbrain, cerebellum And medulla. All parts of the brain are of great importance in the life of a fish. For example, the cerebellum controls the animal's coordination and balance. The medulla oblongata gradually passes into the spinal cord. It plays a big role in controlling breathing, blood circulation, digestion and others. the most important functions body.

Sense organs of fish using the example of river perch

Sense organs allow fish to navigate their environment well. An important role is played in this eyes. Perch sees only at a relatively close distance, but distinguishes the shape and color of objects.

Two holes are placed in front of each eye of the perch - nostrils, leading to a blind sac with sensitive cells. This is the organ of smell.

Hearing organs of river perch

Hearing organs They are not visible from the outside, they are placed on the right and left of the skull, in the bones of the back part. Due to the density of water, sound waves are well transmitted through the bones of the skull and are perceived by the hearing organs of the fish. Experiments have shown that fish can hear the footsteps of a person walking along the shore, the ringing of a bell, or a gunshot.

Taste organs of river perch

The taste organs are sensitive cells. They are located in perch, like other fish, not only in the oral cavity, but also scattered over the entire surface of the body. There are also tactile cells there. Some fish (for example, catfish, carp, cod) have tactile antennae on their heads.

Side line

Fish are characterized by a special sensory organ - the lateral line. A series of holes are visible on the outside of the body. These holes are connected to a channel located in the skin. The canal contains sensory cells connected to a nerve running under the skin.

The lateral line perceives the direction and strength of water flow. Thanks to the lateral line, even blinded fish do not bump into obstacles and are able to catch moving prey.

Reflexes of fish using the example of river perch

Observing the behavior of a perch in an aquarium, you can notice that its responses to irritation can manifest themselves in two ways.

If you touch the perch, it will instantly dart to the side. His response to the type of food is just as quick. A greedy predator, he quickly rushes at his prey ( small fish and various invertebrates - crustaceans, worms). At the sight of prey, excitation goes along the optic nerve to the central nervous system of the perch and immediately returns from it through the motor nerves to the muscles. The perch swims to the prey and captures it. The mechanism of such body responses to irritation is innate - such reflexes called, as you already know, congenital or unconditional. All animals have the same species without conditioned reflexes are the same. They are inherited.

If feeding fish in an aquarium is accompanied by any actions (conditions), for example, lighting a light bulb or tapping on glass, then after a while such a signal begins to attract fish on its own, without feeding. In response to such signals, fish produce acquired, or conditional reflexes, arising under certain conditions.

Unlike innate reflexes conditioned reflexes are not inherited. They are individual and are produced during the life of the animal.

Fish - aquatic animals, adapted to life in fresh water bodies and sea ​​water. They have a hard skeleton (bone, cartilaginous or partially ossified).

Let us consider the structural features and vital functions of fish using the example of river perch.

Habitat and external structure of fish using the example of river perch

River perch lives in freshwater bodies of water (slow-flowing rivers and lakes) in Europe, Siberia and Central Asia. Water exhibits noticeable resistance to bodies moving in it. Perch, like many other fish, has a streamlined shape - this helps it move quickly in the water. The perch's head smoothly transitions into the body, and the body into the tail. At the pointed front end of the head there is a mouth with lips that can open wide.

Drawing: external structure river perch

On the top of the head two pairs of small holes are visible - nostrils leading to the olfactory organ. On its sides there are two large eyes.

Perch fins

Bending the laterally flattened body and tail first to the right and then to the left, the perch moves forward. When swimming, fins play an important role. Each fin consists of a thin membrane of skin, which is supported by bony fin rays. When the rays spread out, the skin between them tightens and the surface of the fin increases. On the back of the perch there are two fin pins: front big And the rear one is smaller. The number of dorsal fins may vary between different fish species. At the end of the tail there is a large two-lobed caudal fin, on the underside of the tail - anal. All these fins are unpaired. Fish also have paired fins - there are always two pairs of them. Pectoral fins(front pair of limbs) are placed on the sides of the perch’s body behind the head, paired pelvic fins (back pair of limbs) are on the underside of the body. The main role in moving forward is played by caudal fin. The paired fins are important for turning, stopping, moving forward slowly, and maintaining balance.

The dorsal and anal fins give the fish body stability when moving forward and making sharp turns.

Cover and color of perch

The body of the perch is covered bone scales. Each scale with its front edge is immersed in the skin, and with its rear edge it overlaps the scales of the next row. Together they form a protective cover - scales that does not interfere with body movements. As the fish grows, the scales also increase in size and can be used to determine the age of the fish.

The outside of the scales is covered with a layer of mucus, which is secreted by the skin glands. Mucus reduces friction between the fish's body and water and serves as protection against bacteria and mold.

Like most fish, the belly of the perch is lighter than the back. From above, the back to a certain extent merges with the dark background of the bottom. From below, the light belly is less noticeable against the light background of the water surface.

The body color of a perch depends on the environment. In forest lakes with a dark bottom it has a dark color, sometimes even completely black perches are found there. Perches with light and bright colors live in reservoirs with a light sandy bottom. Perch often hides in thickets. Here the greenish color of its sides with vertical dark stripes makes the perch invisible. This protective coloring helps him hide from enemies and better watch over his prey.

Along the sides of the perch's body from head to tail runs a narrow dark lateral line. This is a kind of sensory organ.

Skeleton of a river perch

The skeleton of a perch consists of a large number of bones. Its basis is the spine, which stretches along the entire body of the fish from the head to the caudal fin. The spine is formed by a large number of vertebrae (perch has 39-42).

Figure: Skeleton of a river perch

When a perch develops in the egg, a notochord appears in the place of its future spine. Later, vertebrae appear around the notochord. In adult perch, only small cartilaginous remains between the vertebrae are preserved from the notochord.

Each vertebra consists of body And upper arch, ending in a long upper process. Taken together, the upper arches together with the vertebral bodies form the spinal canal, which contains spinal cord.

In the trunk section of the body, they are attached to the vertebrae at the sides ribs. There are no ribs in the caudal region; each vertebra located in it is equipped with a lower arch ending in a long lower process.

In front, the skeleton of the head is firmly articulated with the spine - scull. There is also a skeleton in the fins.

In paired pectoral fins, the skeleton of the fins is connected to the spine by bones shoulder girdle. The bones connecting the skeleton of the paired pelvic fins to the spine are not developed in the perch.

The skeleton is of great importance: it serves as a support for muscles and protection for internal organs.

River perch muscles

Under the skin there are muscles attached to the bones that form muscles. The strongest of them are located on the dorsal side of the body and in the tail.

The contraction and relaxation of muscles causes the fish's body to bend, allowing it to move in the water. The head and fins contain muscles that move the jaws, gill covers and fins.

Swim bladder of river perch

River perch, like any fish, is heavier than water. Its buoyancy ensures swim bladder. It is located in the abdominal cavity above the intestines and has the shape of a translucent sac filled with gas.

Figure: Internal structure of river perch. Digestive and excretory systems

The swim bladder is formed in the perch embryo as an outgrowth of the intestine on the dorsal side. It loses connection with the gut during the larval stage. The larva should float to the surface of the water 2-3 days after hatching and swallow a little atmospheric air to fill the swim bladder. If this does not happen, the larva cannot swim and dies.
By regulating the volume of the swim bladder, the perch stays at a certain depth, floats up or sinks. When the bladder contracts, excess gas is absorbed by the blood in the capillaries of the inner surface of the bladder. If the bubble expands, gas enters it from the blood. When the perch sinks into the depths, the bubble decreases in volume - and the density of the fish increases. This promotes rapid immersion. When floating, the volume of the bubble increases and the fish becomes relatively lighter. At the same depth, the volume of the fish's bladder does not change. This allows the fish to remain motionless, as if hanging in the water column.
Unlike river perch, in other fish, such as carp, bream, roach, herring, the swim bladder remains connected to the intestine using an air duct - a thin tube throughout life. Excess gas exits through this duct into the intestines, and from there through the mouth and gill slits into the water.
The main function of the swim bladder is to provide buoyancy for fish. In addition, it helps fish hear better, since, being a good resonator, it amplifies sounds.

Perch is a medium-sized fish with very variegated and bright colors. Body length up to 50 cm, weight up to 1.5 kg, rarely up to 3 kg. The mouth has small bristle-like teeth. Big orange eyes. The tail, anal fin and pelvic fins are bright red, the pectoral fins are yellow. The first dorsal fin is gray with a large black spot in the rear, the second is greenish-yellow (Ostroumov, Zvereva, 1972).

There are 53-74 scales in the lateral line; they do not extend to the caudal fin. The number of gill rakers is 16-29. Vertebrae 38-44. The first dorsal fin has 13-16, rarely 12 rays. The second has 1-4 spiny rays and 12 to 17 soft rays. The anal fin, as a rule, always has 2 spiny rays; occasionally there may be one or three. The number of non-spiny rays ranges from 7 to 11. The pectoral fin has 1 non-branched ray and 13-16 soft branched rays. The ventral fin consists of one spiny fin and 4 to 6 soft rays (Atlas., 2003).

The perch has a greenish-yellow color with black transverse stripes on the sides, of which there can be from 5 to 9; The belly of the perch is white. Characteristics the structures of individual stripes can be used for individual tagging of fish (Michel et al., 1983).

The body of the perch is laterally compressed, the scales are ctenoid. The scaly cover on the head is poorly developed. It partially covers the parietal bones, on the gill cover - only the upper corner. The cheeks are covered with 7-8 longitudinal rows of thin and weakly attached scales. (Pokrovsky, 1951). The operculum has a slightly curved posterior margin and is usually equipped with one spine. Radial striations, if present, are weakly expressed. The intermaxillary bones are retractable. The gill membranes are not fused to each other (Berg, 1949).

The pectoral and pelvic fins are rounded at the ends, the caudal fin is moderately deep. The base of the pectoral fin is located below the vertical end of the head or slightly behind it and is covered with a weak scale cover. The two dorsal fins touch or are slightly apart, with the first dorsal fin higher than the second (Gulyaevva, 1951).

Variability of river perch

As is known, body proportions change with age in vertebrates. Most often, body height and eye size, the length of the caudal fin and caudal peduncle change as they grow. The length of the head changes the least.

Comparing the main external morphological features of a typical perch with descriptions of this species by other researchers, V.V. Pokrovsky (1961) established two main directions in deviations from the typical form, along which the acquisition, inheritance and consolidation in the process of selection of new characters in perches of individual reservoirs occurs. In accordance with this, the author identified two ecological types that have morphological and biological differences.

The adaptive value of some of the listed characteristics is quite reasonable. Such features include the structural features of the gill and jaw apparatus, the length of the caudal peduncle and the morphology of the fins (Pokrovsky, 1961).

In large lakes and reservoirs with a rich and varied food supply and an abundance of suitable biotopes, perch forms 2 or 3 ecological forms, differing in habitat, food composition and growth rate. Small coastal perch grows very slowly and feeds on invertebrates, while deep-dwelling perch grows quickly and feeds mainly predatory image life, feeding on the juveniles of different species of fish, mainly carp and perch (Atlas., 2003).

Of all the diversity of ecological forms of perch, V.V. Pokrovsky identifies two main ecological types, giving them taxonomic status. These are Perca fluviatilis vulgaris and Perca fluviatilis gracilis.

Perca fluviatilis infraspecies vulgaris is an active predator, characterized, relative to the characteristics of a typical perch, by a decrease in the number of vertebrae, scales in the lateral line, rays in the first dorsal fin, gill rakers and their shortening, an increase in the size of the head and lengthening of the jaws, an increase in body height, anterodorsal distance, the length of the caudal peduncle, the base of the pectoral and anal fins, the development of rigid, firmly attached scales.

Perca fluviatilis infraspecies gracilis is a peaceful perch that does not make rapid movements. Here, in comparison with the original form, there is a decrease in the number of scales in the lateral line, the size of the head and the length of the jaws, the height of the body, the antedorsal distance, the length of the caudal peduncle and the base of the anal and pectoral fins. At the same time, the height of the first dorsal fin, the length of the gill rakers and their number increase.

The divergence of a single population of perch within one reservoir into two ecotypes provides the species with the most rational use feeding areas, migration routes and breeding sites. A similar phenomenon aimed at reducing intraspecific competition, is observed in many species of fish, such as roach, bream and roach, and whitefish (Pokrovsky, 1961).

The meristic characters of perch are also subject to environmental variability. Depending on the type of reservoir, the number of vertebrae changes. Thus, in lakes, perch have an increase in the number of vertebrae. This phenomenon is called the “lake effect” (Kozhara et al., 1999). Some increase in the number of vertebrae is also observed in samples of perch from the upper reaches and small tributaries large rivers. (Makarova, 1993).

Meristic characters are also subject to geographic variability. Thus, the number of spiny rays in the dorsal fins and the number of soft rays in the anal fin tend to decrease from north to south and increase from west to east. Within the same basin, these signs hardly differ. The number of rays in paired fins is usually more stable (Popova et al., 1993).

The number of gill rakers on the first gill arch decreases to the west and east (there are exceptions). The value of this indicator depends on the latitude of the reservoir, temperature regime reservoir and its food supply (Popova et al., 1993).

Of all the meristic characters, the most variable is the number of scales in the lateral line. When comparing fish different generations sometimes they can, significant differences in the average values ​​are revealed. More scales are observed in perch from northern reservoirs and mountain lakes. A small number of scales in the lateral line is typical for the lower reaches of large southern rivers(Popova et al., 1993).

Note that unfavorable changes in environmental conditions at the edge of the range may lead to an increase in the level and strong fluctuations in phenotypic diversity in the perch population from the extreme northern and southern reservoirs (Makarova, 1993).

Age variability of perch is manifested in relatively few signs. The diameter of the eye and caudal notch correlates with body length. The number of vertebrae, fin rays, gill rays and the number of gill rakers does not change. Perch 3-5 cm long have the same number of gill rakers as adults. Subsequently, only a change occurs in their shape, relative length and armament with denticles. The outermost stamens turn into tubercles, the number of denticles on all stamens increases, and the stamens become relatively shortened (Pokrovsky, 1951).

In populations of predatory perch in different parts area there are differences in the ratio of protein and fat metabolism. Under optimal conditions, the metabolism of perch of all size groups is characterized high degree use nutrients feed for growth and energy needs of the body. Perch in the southern regions did not deposit significant fat reserves throughout the growing season. In sexually mature individuals of perch from northern populations, there is a tendency to accumulate fat reserves in the body cavity throughout the year (Makarova, Shatunovsky, 1993).

Pisces are the first creatures with a developed spinal structure. During the process of evolution, these creatures underwent many changes that allowed them to adapt to aquatic environment. Internal structure bone fish(female perch) may seem primitive in comparison with many vertebrates that live on land, but this is not true. The body of the perch is well adapted for life in the aquatic environment, so this fish is widespread in freshwater bodies around the world.

The anatomy of fish is often studied using these individuals as examples, since making a stuffed perch is not difficult. Perches are among the extremely bony fish; the fish has a developed musculoskeletal system. The spine of an adult fish consists of more than 30 vertebrae. They vary in size depending on location, but have a similar structure. The vertebral body has a slightly flattened shape. The upper and lower arcs extend from this element.

The upper arches close to form a special canal in which the spinal cord lies. The skeleton of a perch is mobile due to the fact that the bone elements are connected by cartilage tissue.

The lateral processes of the vertebrae are quite rigid and serve as ribs that protect the internal organs from mechanical damage. The external and internal structure of perches is due to the fact that they are aquatic animals; their bony structure allows them to move.

The spine is crowned by a caudal fin. It is represented by a vertical plate divided into 2 halves. The dorsal fin acts as a stabilizer. Thanks to it, the fish can make sharp turns. In addition, the dorsal fin is crowned with spines, which perform a protective function.

Quantity unpaired fins in perch it reaches 3 pieces: 2 of them are located on the back, another 1 - in the anus. The paired fins of river perch are both pectoral and ventral. These fins consist of 5-6 small bones. The limbs (the fin itself) are crowned with sharp protrusions.

The body of the fish is covered with small scales. It has a gray-green color, the color allows the perch to remain unnoticed in muddy water.

The perch skull is relatively small in size. The bone elements of the skull protect the brain from mechanical damage. The main part of the skull is represented by the lower and upper jaws. There are gills on the sides of the head; there are few muscles in the head of the fish. On the side of the pharynx, bony gill arches cover the respiratory apparatus of the fish.

Considering the external structure of river perch, it should be noted that these fish are distinguished by well-developed muscles. The muscles are attached to the spine, gill processes and other bone elements of the musculoskeletal system, providing high speed of movement. Perches have a well-developed swim bladder. This is a special organ located inside the fish, which is a bubble filled with a mixture of gases. This organ allows the fish to more easily control the depth of its dive, preventing it from sinking under the weight of its own body.

Digestive system

When considering the internal structure of river perch, you should first of all pay attention to the digestive system of this creature. It is represented by the following elements:

• oral cavity;
• pharynx;
• esophagus;
• stomach;
• intestines;
• pancreas;
• gallbladder.

There are many teeth on the upper and lower jaws of the fish. Food from the oral cavity enters the pharynx, then, thanks to muscle contractions, is pushed into the esophagus and stomach. The main digestive organ of this fish is large. Here, under the influence of gastric juice, food undergoes primary processing. After this, the digested food enters the intestines, where nutrients are released from it under the influence of juices produced by the pancreas.

The digestion process also involves juices released from special glands located on the intestinal walls, and bile. The intestines absorb nutrients and water into the blood.

Respiratory

The opening of the respiratory system is located in the pharynx. Here the gills come to the surface, which are covered with bone plates. The bone plates move back due to the work of the muscles, providing an influx of oxygenated water to the gills. The respiratory apparatus is represented by 4 pairs of vertical rigid arches, to which many gill filaments are attached.

Inside the petals there are many small capillaries, which ensure gas exchange, i.e. oxygen from water enters the blood, and carbon dioxide is removed from the body. The gills on the side of the pharynx are equipped with special stamens that prevent the leaves from clogging with food particles.

Circulatory system

The circulatory system of perch is closed. Blood is pumped by the perch's two-chambered heart, consisting of a ventricle and an atrium. Blood circulation is continuous. Blood rich in carbon dioxide is pumped through the heart.

Once the blood enters the gills, it is distributed through the capillaries, where it is saturated with oxygen. The blood is then redirected to the dorsal aorta. Thanks to this vessel, blood is delivered to all organs of the body, as well as the brain.

Excretory system

The genitourinary and excretory systems of fish are interconnected. Support normal chemical composition kidney blood. They are located along the spine. After this, waste products and excess salts are excreted through the ureters and bladder. Waste is removed from the bladder through a special opening.

The ovaries are located near the bladder. The eggs mature here during the breeding season. Females have a separate genital opening through which ripe eggs are released.

Nervous system of perch

The central nervous system of the perch is represented by the brain and spinal cord. The cranial nerves innervate the gills.

The spinal roots control the functioning of muscles and organs. They ensure the implementation of inherent reflexes and instincts.

Sense organs

The main sensory organ of the female perch is the eyes. The lens of the eye has a round shape. Thanks to the movement of the lens along the optical axis, the fish has the ability to see equidistant objects. The cornea is flat. This structure of the main elements of the eye provides the aquatic creature with good vision in water.

In addition, fish have well-developed olfactory organs. The nostrils are represented by inlet and outlet openings. Inside the nose there is an olfactory sac, in which there are many folds covered with olfactory epithelium.

The fish's hearing organ ensures the capture of sound vibrations.

It is believed that the capture of sound waves in the water of this creature occurs over the entire surface of the body. After this, the signals are transmitted to the auditory analyzer. The organ of hearing is combined with receptors responsible for balance.