Internal structure of a bony fish, female perch. Fish
Fish - aquatic animals adapted to life in fresh water oemah 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 (slowly 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 streamlined shape- this helps him 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 big 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 big role fins play. 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. Number dorsal fins at different types fish may vary. 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. Main role plays when moving forward caudal fin. The paired fins are important for turning, stopping, moving forward slowly, and maintaining balance.
Dorsal and anal fins give the fish's 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. Top back to to a certain extent merges with dark background 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.
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 large number bones. Its basis is the spine, which stretches along the entire body of the fish from the head to caudal fin. The spine is formed a large number 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 trunk section the bodies are attached to the vertebrae laterally 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 has great importance: it serves as a support for the 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 inner surface bubble 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 passes through this duct into the intestines, and from there through the mouth and gill slits in 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.
Class Bony fish.
river perch.
Like cartilaginous fish, the body of bony fish is divided into three sections. The boundary between the head and the body is the gill slit, and between the body and the tail is the anus. There are at least 12 different morphological types of fish appearance: torpedo-shaped (tuna, herring, cod), serpentine (eels), ribbon-shaped (saberfish), flattened (bream, flounder).
There are eyes on the sides of the head. In front of them are the olfactory openings - the nostrils. The squirter is preserved only in sturgeons. The gill arches are located in the gill cavity and are covered by bony gill covers. Paired fins include pectoral and ventral. The unpaired fins include the dorsal, anal and caudal fins. In front of the anal fin there are three openings: anal, genital and excretory.
Veils.
The multilayered epidermis contains numerous unicellular glands. The mucus secreted by these glands performs numerous functions: it has bactericidal properties, participates in the release of metabolic products and water-salt metabolism, accelerates blood clotting and reduces the friction of fish on water, and secretes a secretion when the skin is damaged (ichthyopterin), which is also called the “substance of fear” , it serves as a signal of danger and releases pheromones.
In the lower layers of the epidermis there are pigment cells - chromatophores.
Below the epidermis is the dermis.
The scales of bony fishes are represented by bony scales that form in the corium. The most primitive is ganoid scale (armored pike and polyfins), cosmoid (in lobefins and lungfishes), in most bony fishes the scales are elasmoid, formed only by bony plates. Depending on the condition of the outer edge, cycloid and ctenoid scales are distinguished. Each scale lies in a special pocket. The scales overlap each other in the form of tiles. Light (wide) and dark (narrow) colors are visible on the scales. tree rings. The light wide layer is the summer growth of scales, the dark narrow layer is winter growth. They can be used to determine the age of the fish.
Skeleton.
It is formed by bones; only sturgeons retain a significant amount of cartilaginous elements throughout their lives.
1. Axial skeleton includes the spinal column and skull. Unlike cartilaginous fish, whose ribs limit the body cavity only from above, bony fish have long ribs and also limit the body cavity from the sides. The last caudal vertebra has the attachment surface for the supporting structures of the caudal fin. Each type of fish is characterized by a certain total vertebrae The visceral also includes the bones of the gill cover.
2. Additional.
The belt of the forelimbs—the pectoral fins—is formed by a small scapula and coracoid. The pectoral fins lack basalia, so the bony radials are attached directly to the bones of the girdle. The skeleton of the fins themselves is formed by bony rays of cutaneous origin, which are attached to the radials.
The belt of the hind limbs consists of two fused bones, freely lying in the thickness of the muscles, to which the bony rays of the ventral fins are attached.
Muscular system.
Better developed than cartilaginous ones. It is represented by the muscles of the torso, head and fins.
Clusters of specialized muscle fibers form the electrical organs of fish, which can be located in different parts bodies. The electrical organ resembles a battery; it consists of special muscle plates separated by gelatinous tissue. The more powerful the electric organ, the more plates it contains.
Digestive system.
The oral cavity is equipped with numerous teeth. Typically, teeth are fused to the surface of the bone. The basis of the tooth is dentin, covered on the outside with a thin layer of enamel. In fish feeding plant foods or plankton teeth are missing. The pharynx, penetrated by gill slits, is actively involved in the digestion process. The entry of food into the oral cavity occurs due to the movement of the gill covers, while water along with food is sucked into the oral cavity, passes from it into the pharynx and is pushed out of it through the gill slits. In this case, the food remains in the pharynx, since the gill rakers do not allow it to pass through. In fish that feed on plankton, the stamens form a powerful filtering apparatus; in predators they are short. Esophagus. Stomach. The small intestine, where the ducts of the liver and pancreas flow. The small intestine of bony fishes is much longer and forms loops. This is where the main breakdown and absorption occurs. The large intestine opens into the anus. The anatomically formed pancreas is absent, its structures are dissociated in the liver tissue.
Most have a swim bladder, which embryonically develops as an outgrowth of the esophagus. Depending on whether the connection between the bladder and the esophagus is maintained, fish can be open-vesical or closed-vesical. The swim bladder is filled with air, which significantly reduces specific gravity fish and allows it to hang in the water. Fish can arbitrarily change the volume of gas in the bubble, which leads to a decrease or increase in buoyancy. For this purpose, closed bladders have a special network of blood capillaries in the wall of the bladder.
Respiratory system.
Every gill bony fish consists of a gill arch on which gill filaments sit in two rows. From internal walls gill rakers extend from the gill arches.
The respiratory act of bony fishes includes two stages. In the first of them, the fish lifts its gill covers and fresh water enters through the mouth. At the second stage, the retracted gill covers are pressed against the body with force and water exits into the environment through the gills. At high speed When swimming, the bones switch to the shark type of breathing.
Circulatory system.
Features: 4 gill vessels;
Excretory system.
Mesanephros. The main end product of nitrogen metabolism is ammonia.
Nervous system.
The brain is more primitive.
A taste organ has appeared - small taste buds that are scattered over the entire outer surface of the skin.
Reproductive system.
Male reproductive system - paired elongated sac-shaped testes, vas deferens, genital opening.
The female reproductive system is paired ovaries. Part of the membrane is elongated and forms a duct, which opens into the genital opening.
Fertilization is external. The process of laying eggs is called spawning. Development is direct or with the larval stage.
Description of the presentation by individual slides:
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Biology Animals Grade 7 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 river perch Type Chordata Subtype Cranial or Vertebrates Superclass Fishes Class Bony fishes Subclass Ray-finned Superorder Teleosts Order Perciformes Family Perciformes Genus Freshwater perches 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 section of the digestive tube - the pharynx, the organs of the respiratory system (gills or lungs) develop; the circulatory system is closed; the heart is located on ventral side body, under the alimentary canal.
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River perch is a common inhabitant of fresh waters. 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 large 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. 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, 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. The main role when moving forward is played by the 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.
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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 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. 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 by a large number of 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 is of great importance: it serves as a support for 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 sharp teeth sitting on the 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 the 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 the 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. Oxygen dissolved in water penetrates into the blood through the thin walls of the gill filaments, and is removed from the blood into the water. carbon dioxide. 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 an atrium and a 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 at a relatively close distance; it 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.
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FISH REPRODUCTION AND DEVELOPMENT
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Reproductive organs. Perches, like most fish, are dioecious. In females, in the body cavity there is a large ovary in which egg cells (eggs) develop, in males there is a pair of long testes. During the breeding season, the testes are filled with a thick white liquid - milt. Milk contains millions of sperm. The genitals open outward on the ventral side of the body through the genital opening. Spawning. When the reproductive cells mature, the reproductive instinct appears in fish. At this time, they move to places more favorable for the development of their offspring. Perch reaches maturity in the second year. Its spawning begins only after the disappearance of ice on reservoirs. Some time before spawning, the color of the perches becomes especially bright. They gather in flocks in creeks, oxbow lakes and other places that are shallow and without a current. Females spawn eggs, glued together in the form of ribbons, onto aquatic plants. Males emit milk at this time. Motile sperm swim up to the eggs and penetrate them. The complex instinctive behavior of fish during the breeding season is called spawning.
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Development. The fertilized egg begins to divide. A multicellular embryo is formed, in which a yolk sac is visible on the ventral side - the remainder of the reserve nutrients caviar. In perch, 9-14 days after fertilization, the larva leaves the egg shell and begins to feed on its own, first with microorganisms, and then with small crustaceans and other animals suspended in the water column. After some time, the larva becomes similar to an adult perch - it is a fry. It grows relatively quickly: after about two months its length reaches 2 cm, and after a year the young perch has a length of about 10 cm. Caring for the offspring. Perch eggs often die from drying out reservoirs, and larvae and fry die from enemies. Only due to the fact that during spawning a female perch spawns up to 300 thousand eggs, some of the offspring survive to adulthood. The number of eggs in fish of other species can be even greater than in river perch. For example, cod spawns several million of them. Those fish species that are characterized by caring for their offspring usually lay a small amount of eggs, but most of their eggs, larvae and fry do not die.
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Friends! Today we will continue to study the structure of river perch.
The circulatory system of river perch.
Circulatory system closed type . Heart of the river perch two-chamber, it consists of the atrium and ventricle. The blood in the heart is only venous. After the ventricle contracts, blood is expelled through the aortic bulb into the abdominal aorta.
They arise from the abdominal aorta afferent branchial arteries, which carry venous blood to the gills.
Then, in the gill filaments, which are washed by water, the venous blood releases carbon dioxide and is saturated with oxygen dissolved in the water. In this case, the blood becomes arterial.
By efferent branchial arteries oxygenated blood moves to the dorsal aorta.
Paired carotid arteries run from the dorsal aorta to the head. In the caudal part, the dorsal aorta smoothly passes into the caudal artery, which is located inside the lower arches of the caudal vertebrae.
Numerous arteries branch off from the dorsal aorta to all organs of the river perch. Arteries break up into capillaries in which gas exchange occurs.
The venous blood then collects through the capillaries into the veins. From the front of the body, venous blood collects in pairs anterior cardiac veins. From the back of the body, blood collects in posterior paired cardiac veins. Venous blood from digestive system going to unpaired hepatic vein.
Thus into the atrium blood is flowing from five large veins - paired anterior and posterior cardiac and azygos hepatic veins.
Nervous system of river perch.
The central nervous system consists of the brain and spinal cord. The peripheral nervous system is represented by cranial nerves, which arise from the brain, and spinal nerves, respectively, from the spinal cord.
The perch's brain consists of five sections, like all vertebrates. These are the forebrain, diencephalon, midbrain, cerebellum and medulla oblongata.
The perch has very well developed olfactory lobes of the forebrain. The midbrain contains the visual centers, from diencephalon the optic nerves depart. IN medulla oblongata the centers of the hearing organs and the lateral line are located.
Sense organs.
The olfactory organs of river perch consist of paired sacs, which are covered with olfactory capsules. The nostrils lead to the olfactory sacs. In river perch, the nostrils are not through, that is, they do not lead into the nasopharynx, but end in blind olfactory sacs.
The structure of the eye of the river perch is similar to the structure of the eye of all vertebrates, but there are also differences. The lens of the river perch has spherical shape, like other fish species. While in terrestrial vertebrates the lens has the shape of a lens. Perch cornea flat, and in terrestrial vertebrates it is convex.
Accommodation, that is, the ability to see objects at different distances, is carried out due to the movement of the lens along the optical axis (unlike terrestrial vertebrates, which are capable of changing the curvature of the lens).
The organ of hearing of the river perch is combined with the organ of balance and is represented only by the inner ear. Sound vibrations are picked up the entire surface of the body.
The organs of taste are taste buds or taste buds, which are located not only in the oral cavity, but also on the entire surface of the body. With the help of taste buds, river perch can determine chemical composition water.
River perch, like all fish, has lateral line organs. Special sensory cells in the lateral line are located inside channels located under the skin.
From the outside, the lateral line channels open with holes. Thanks to the lateral line, the perch detects the direction of the water flow.
Excretory system of river perch.
The excretory organs of perch are trunk buds. They have a ribbon-like shape and are located under the spine. The ureters extend from the kidneys, at the junction of which there is a small bladder. Bladder ends with the urethra.
Reproductive system of river perch.
The gonads of river perch are paired. Females have a pair of ovaries, males have a pair of testes. The paired glands merge at the posterior end of the body and open outward into the genital opening.
adminWater 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 large eyes. 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 dorsal fins: the large anterior one and the posterior one. smaller number The dorsal fins may be different in different species of fish. 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. Pectoral paired fins (front pair of limbs) are placed on the sides of the perch's body behind the head, paired ventral fins (back pair of limbs) are located on the underside of the body. The caudal fin plays the main role when moving forward. Paired fins are important when turning, stopping, moving slowly forward and maintaining balance. The dorsal and anal fins give the fish body stability when moving forward and making sharp turns. The body of the perch is covered with bony scales. Each scale with its front edge is embedded 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 the back. From above, the back merges to a certain extent 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 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. This is a kind of sensory organ, the structure and meaning of which you will become familiar with later.