Perch is a fish belonging to the subtype: Vertebrates - VERTEBRATA. Bony fish - Osteichthyes. All fish are aquatic animals that are adapted to live in water.
The body of the perch is streamlined, which allows the fish to swim faster; head, torso and tail are not separated by clear boundaries. The head of the perch and the spine are articulated with each other and have a smooth transition. The perch has a wide-opening mouth. Above the mouth is the head provided with nostrils entering the olfactory organ. Right and left - huge eyes.
River bass fins
During movement, the body of the river perch bends by means of the tail part of the body, creating wave-like movements in both directions, allowing the fish to move forward. During the advancement, fins perform an important mission. They have a membranous structure supported by fin rays. They consist of bone tissue... When the rays move apart, like the bellows of an accordion, the membranes stretch and increase the size of the entire fin.
The perch has two dorsal fins, one of which (front) is larger than the other. The caudal fin is bilobed. There are also fins in the lower part of the tail, one of which is anal. The named fins are not paired. Paired fins are located on the chest (pectorals), on both sides behind the head. On the back pair of limbs are the abdominal. They are located below the body of the perch. The caudal fin plays the most important role during the advancement of the fish. The body of the perch flexes as its muscles contract and relax. The head and fins of a fish are equipped with muscles that move its mouth and fins.
When turning, stopping or walking slowly, and to maintain balance, paired fins have essential in the life of a perch. To keep the fish's body stable while moving forward and on sharp turns, nature has provided the perch with anal and dorsal fins.
Skin and color of perch
The body of the perch is covered with bony scales, which are attached to the body “overlapping”: the front part of the scales is in the skin of the perch, and the back part lies on the scales of another row. All scales form a protective shell of the fish, which does not interfere with the movement of fish in the water. The scales that increase with the growth of the fish determine its age. The scales of perch and any other fish on the outside have a slippery consistency. This mucus is produced by special glands in the skin. Thanks to it, the fish is protected from friction against the water column. Mucus is also protective film from the penetration of various bacteria and fungi.
The color of the perch is in direct proportion to its habitat. If the bottom of the reservoir is dark, the perch is also darker in color than its counterparts living in open lakes, the bottom of which is sandy. These perches are lighter and bright in color. If the perch is accustomed to hunting in thickets of underwater vegetation, then it acquires a brownish-green color with almost black stripes located across the body. Such a war paint can make the fish invisible and helps to watch for a potential victim. To the left and to the right, a thin, almost black stripe, serving as a kind of sensory organ.
It is the base consisting of the spinal column and the skull. The vertebral column of the perch is created by several dozen vertebrae. They are all the same, and each of them is a double concave disc. The thickened parts of the vertebra are called the body. The spinal cord is located in the canals formed by the upper arches. There are also lower arcs. The brain is protected by them from any damage. From the disk, processes extend upward, which are closed together. The lateral processes are not connected.
The ribs are attached to the lower part of the vertebra, which are designed to support the muscles of the whole trunk, and also the ribs have the function of protecting all internal organs fishes. In the caudal part of the spine, the vertebrae are also equipped with arcs that form tubules with blood vessels passing through them.
The common perch, if not for its swim bladder, would have drowned, because the water is lighter. The bubble is in the belly of a predator and looks like a small ball filled with air. But there is gas inside. In order for the capacity of the bubble to be normal, the perches are at a certain height from the bottom, periodically floating up and down again. The swim bladder acts to keep the perch in the water and prevent it from drowning. Thanks to the bubble, the perch moves freely in the water space, without spending on it a large number of energy. It also enhances the hearing of the perch as it resonates well.
1. Features of the external structure of teleost fish on the example of river perch.
Fish are ancient primordial vertebrates. Unlike skullless ones, they lead an active lifestyle. Their structural features are associated with the aquatic environment. More than 20 thousand species of fish are known, which are combined into two classes: Cartilaginous and Bone. The most abundant and diverse are bony fishes, more than 90% of which are bony fishes. These include herring, cod, carp, salmon, perch, pike, etc.
A typical representative is river perch. The shape of the body is streamlined, the head smoothly passes into the body, and the body into the tail. On the head is a mouth with lips, large eyes, nostrils and gill covers. There are fins: paired (pectoral and abdominal) and unpaired - caudal, dorsal and anal. The skin is covered with bone scales. Che-Shuiks overlap each other in tiles. The skin glands secrete mucus that covers the scales and reduces body friction against water.
2. Features of the internal structure of teleost fish on the example of river perch.Material from the site
The skeleton of a river bass consists of a large number of bones. In it, the skull, spine, the skeleton of the shoulder and pelvic girdles, and the skeleton of fins are distinguished. The skull consists of the cerebral box, jaw bones, gill arches and gill roofs. The spine includes the trunk and tail vertebrae. The ribs are attached to the trunk vertebrae. The digestive system includes the mouth with teeth, pharynx, esophagus, stomach, small intestine, where the ducts of the gallbladder, liver and pancreas open, the posterior intestine, anus. There is a swim bladder (an outgrowth of the anterior intestine), filled with a mixture of gases. It participates in gas exchange and is a hydrostatic organ. Fish breathe with gills, which consist of gill arches and gill lobes, pierced by blood vessels. The perch has four pairs. For circulatory system characterized by a two-chambered heart and one circle of blood circulation. Venous blood flows through the heart, which becomes arterial in the gills. The excretory system includes long trunk kidneys, ureters and bladder... The nervous system consists of the brain and spinal cord and nerves extending from them. The brain is protected by the bones of the cranium and consists of five sections: the medulla oblongata, the cerebellum, the midbrain, the intermediate section, and small hemispheres of the forebrain with the olfactory lobes. The organs of vision - the eyes, have a flat cornea and a large crust-face. The eyelids are missing. The organs of smell are in the nasal cavity, the organ of hearing is the inner ear, the organ of taste is in the oral cavity and on the lips. A well-visible lateral line stretches along the body - an organ that perceives the direction and strength of the flow of water, as well as sound vibrations. Tactile cells are scattered throughout the body. Bony fish are single-sex animals. Reproductive organs: paired testes and ovaries, reproductive ducts. External fertilization. Development occurs with transformation (larva - fry - adult fish).
A fish- a vertebrate animal adapted to live in aquatic environment... The body of the fish is streamlined. There is no clear boundary between the head, body and tail. With its tail, the fish beats forcefully from side to side, making wave-like movements. The head is motionlessly articulated with the spine. The backbone and skull form the basis of the internal skeleton of a fish.
A - general form: 1 - jaw; 2 - skull; 3 - gill cover; 4 - shoulder girdle; 5 - the skeleton of the pectoral fin; 6 - the skeleton of the pelvic fin; 7 - ribs; 8 - fin rays; 9 - vertebrae;
B - trunk vertebra; B - caudal vertebra: 1 - spinous process; 2 - upper arc; 3 - lateral process; 4 - lower arc
The spine consists of several dozen vertebrae that are similar to each other. Each vertebra has a thickened part - the vertebral body, as well as the upper and lower arches. The upper arches together form a canal in which the spinal cord lies (Fig. B). Arcs protect him from injury. Long spinous processes protrude upward from the arches. In the trunk region, the lower arches (lateral processes) are open. The ribs adjoin the lateral processes of the vertebrae - they cover the internal organs and serve as a support for the trunk muscles. In the caudal region, the lower arches of the vertebrae form a canal in which blood vessels pass.
In the skeleton of the head, a small cranium, or skull, is visible. The bones of the skull protect the brain. The main part of the skeleton of the head is made up of the upper and lower jaws, the bones of the eye sockets and the branchial apparatus.
Large gill covers are clearly visible in the branchial apparatus. If you raise them, you can see the gill arches - they are paired: left and right. There are gills on the gill arches. There are few muscles in the head part, they are located in the region of the gill covers, jaws and on the back of the head.
There are skeletons of unpaired and paired fins. The skeleton of unpaired fins consists of many elongated bones, reinforced in the thickness of the musculature. Skeleton paired fin consists of a skeleton of a belt and a skeleton of a free limb. The skeleton of the pectoral girdle is attached to the skeleton of the head. The skeleton of the free limb (the fin proper) includes many small and elongated bones. The abdominal girdle is formed by one bone. The skeleton of the free pelvic fin is composed of many long bones.
Thus, the skeleton is a support for the body and organs of movement, protects essential organs... The main muscles are distributed evenly in the dorsal part of the fish's body; the muscles that move the tail are especially well developed.
In the front of the head, above the upper jaw, there are paired nostrils. The eyes of the fish are rather large, mobile, they are devoid of eyelids, they are constantly open. On the sides of the head there are gill covers that cover the cavities with gills. Through the mouth, water enters the pharynx, is filtered through the gill lobes and pushed out through the gill openings. The exchange of gases is carried out using the capillaries of the branchial lobes.
In fish, there are paired and unpaired fins: unpaired - dorsal, anal and caudal, paired are pectoral and pelvic fins. The pectoral fins correspond to the forelimbs of land animals, and the pelvic fins correspond to the hind limbs... Fins are formations consisting of hard and soft rays, connected by a membrane or free. The number of fins, structure and arrangement of different fish species are different. In some species, the fins have grown together and formed the so-called fin edging. Support system creates an internal skeleton - a vertebral column, consisting of biconcave vertebrae with paired spinous processes that support the dorsal and abdominal swimming muscles. The fins have interneural bones for support, carrying fin rays. Muscle segments E-shaped, each one has a shell. The outer surface of the muscles is covered with skin, which is covered with a flexible, usually shell, formed by bone plates - scales. Thus, in a certain sense, fish have external skeleton... Numerous glands secrete mucus, which makes the surface of the fish slippery. Thanks to the mucus layer, the fish experiences less water resistance and is also protected from fungi and bacteria. On the sides of the fish, rows of scales of a different shape are visible. This is the side line. The side line may be broken, solid, or completely absent. It is located on both sides of the body from the operculum to the caudal fin.
The bicameral heart of a fish is located in front of the body. The circulatory system is the simplest: the heart pumps blood into the gills; enriched with oxygen, it goes to various organs of the body, and then again to the heart, gills, etc.
The mouth of many fish species is equipped with teeth; teeth are not only on the jaws, but often on the palatine bones, vomer, tongue. The teeth are renewed frequently. In predatory fish, they are usually cone-shaped, very sharp. The pharynx, short esophagus and stomach are elastic. There can be a varying number of blind outgrowths in the back of the stomach. The intestine is poorly differentiated into sections, ending in the anus located in front of the anal fin. Fat deposits are often formed around the intestines on the mesentery. The internal organs of fish also include the liver, gallbladder, pancreas and spleen.
The kidneys are located under the spine, along it. When gutting fish, the kidneys can easily be mistaken for clotted blood. The bladder is located near the anus.
The reproductive organs - the ovaries in females and the testes in males - have excretory canals into the genital opening. Of the internal organs, except for the gonads, only the kidneys are paired.
Internal structure bone fish(female perch): 1 - mouth; 2 - gills; 3 - heart; 4 - liver; - gallbladder; 6 - stomach; 7 - swim bladder; 8 - intestines; 9 - brain; 10 - spine; 11 - spinal cord; 12 - muscles; 13 - kidney; 14 - spleen; 15 - ovary; 16 - anus; 17 - genital opening; 18 - urinary opening; 19 - bladder
In the body cavity under the kidneys, there is a swim bladder - a hydrostatic apparatus for swimming fish at different depths. In some fish species, the swim bladder and the pharyngeal cavity communicate through a special duct, but the perch, for example, does not have such a duct. The swim bladder is filled with gas, which includes nitrogen, oxygen, carbon dioxide... Their ratio is regulated by the blood vessel system of the bladder walls. Fish with a swim bladder open type, can change depth faster than fish with a closed swim bladder because excess gas is released through the duct between the swim bladder and the pharyngeal cavity. If a fish with a closed swim bladder is pulled out of the water too quickly with great depth, it will swell and force the stomach out through the mouth.
In carp fish, the swim bladder consists of two parts and is always inflated. When the fish dies, the muscles of the swim bladder relax and the fish floats to the surface of the water. The bubble allows fish with low muscle energy expenditure to swim easily in the water.
All fins have a special effect on the movement of the fish. The dorsal and anal fins act as stabilizers. Fins other than the caudal fins are used to regulate body position. Sometimes the fish uses the pectoral fins for slow movement. The metabolism of fish is slowed down by a lady, in cold water... In it, the fish get tired faster than in warm water.
Circulatory system closed fish (Fig. A). Blood flows continuously through the vessels due to the contraction of the two-chambered heart, consisting of the atrium and the ventricle. Venous blood containing carbon dioxide passes through the heart. When the ventricle contracts, it directs blood forward into a large vessel - the abdominal aorta. In the area of the gills, it splits into four pairs of the branchial arteries. They branch on capillaries forward in the branchial lobes. Here the blood is freed from carbon dioxide, enriched with oxygen (becomes arterial) and through the outflowing branchial arteries is directed to the dorsal aorta. This second major vessel carries arterial blood to all organs of the body and to the head. In organs and tissues, the blood gives off oxygen, is saturated with carbon dioxide (becomes venous) and enters the heart through the veins.
: A - scheme of the circulatory system: 1 - heart; 2 - abdominal aorta; 3 - bringing branchial arteries: 4 - outgoing branchial arteries; 5 - carotid artery (carries blood to the head); 6 - dorsal aorta; 7 - cardinal veins (carry blood to the heart); 8 - abdominal vein; 9 - capillary network of internal organs: B - branchial arch: 1 - branchial stamens; 2 - gill petals; 3 - gill plate; B - breathing pattern: 1 - direction of water flow; 2 - gills; 3 - gill covers
Respiratory system located in the pharynx (Fig. B, C). The skeletal support of the branchial apparatus is provided by four pairs of vertical branchial arches, to which the branchial plates are attached. They are divided into fringed gill petals. Thin-walled blood vessels branching into capillaries pass inside them. Gas exchange takes place through the walls of the capillaries: the absorption of oxygen from the water and the release of carbon dioxide. Water moves between the gill lobes due to the contraction of the pharyngeal musculature and the movement of the gill covers. From the side of the pharynx, the bony branchial arches bear the branchial stamens. They protect soft delicate gills from clogging with food particles.
Fish are aquatic animals adapted to life in fresh water and sea water. They have a hard skeleton (bony, cartilaginous or partially ossified).
Let us consider the features of the structure and life of fish using the example of river perch.
Habitat and external structure fish on the example of river perch
River perch lives in freshwater bodies of water (slowly flowing rivers and lakes) in Europe, Siberia and Central Asia. Water provides a noticeable resistance to bodies moving in it. The perch, like many other fish, has a streamlined shape - this helps it move quickly in the water. The head of the perch merges smoothly into the body, and the body into the tail. At the pointed front end of the head, a mouth with lips is placed, capable of opening wide.
Pattern: external structure of river perch
On the top of the head, two pairs of small openings are visible - the nostrils leading to the olfactory organ. There are two large eyes on its sides.
Perch fins
Bending the body and tail flattened from the sides to the right, then to the left, the perch moves forward. Fins play an important role in swimming. Each fin consists of a thin skin membrane supported by bony fin rays. When the rays are spread apart, the skin between them stretches and the surface of the fin increases. On the back of the perch, two s pin fin: front large and rear smaller... The number of dorsal fins in different fish species may vary. At the end of the tail is a large two-bladed tail 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. Paired pectoral fins(front pair of limbs) are placed at the perch on the sides of the body behind the head, abdominal paired fins (rear pair of limbs) - on the lower side of the body. Main role when moving forward plays tail fin... 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 in tight turns.
Covers and coloration of perch
Perch body covered bone scales... Each scale is immersed in the skin with its front edge, and overlaps the scales of the next row with its rear edge. Together they form a protective cover - scales that does not interfere with body movements. As the fish grows, the scales also increase in size, by which you can find out the age of the fish.
Outside, the scales are covered with a layer of mucus, which is secreted by the skin glands. The mucus reduces the friction of the fish's body against the 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 dark background bottom. Below, the light belly is less noticeable against the light background of the water surface.
The body color of the perch depends on environment... In forest lakes with a dark bottom, it has a dark color, sometimes even completely black perches are found there. In reservoirs with a light sandy bottom, perches with a light and bright color live. Perch often lurk in thickets. Here, the greenish color of its sides with vertical dark stripes makes the perch invisible. Such a protective coloration helps him to hide from enemies and better watch out for the victim.
A narrow dark lateral line... This is a kind of sensory organ.
River bass skeleton
The skeleton of a perch consists of a large number of bones. Its base 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 (in the perch there are 39-42).
Pattern: Skeleton of River Bass
When the perch develops in the egg, a notochord appears in the place of the future spine. Later, vertebrae appear around the notochord. In an adult perch, only small cartilaginous remains between the vertebrae are preserved from the notochord.
Each vertebra consists of body and upper arc ending in a long upper process. In their totality, the upper arches, together with the vertebral bodies, form the spinal canal, in which there is spinal cord.
In the trunk of the body, they are attached to the vertebrae from the side ribs... There are no ribs in the tail section; each vertebra located in it is equipped with a lower arch ending in a long lower process.
In front of the spine, the skeleton of the head is firmly articulated - scull... The fins also have a skeleton.
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 with the spine are not developed in the perch.
The skeleton has great importance: it serves as a support for muscles and protection for internal organs.
Muscles of river bass
Under the skin are muscles attached to the bones that form musculature... The strongest of them are found on the dorsal side of the trunk and in the tail section.
The contraction and relaxation of the muscles causes the body to bend the fish, due to which it moves in the water. The head and fins contain the muscles that set the jaws, gill covers, and fins in motion.
River bass swim bladder
River perch, like any fish, is heavier than water. Its buoyancy ensures swim bladder... He is in abdominal cavity above the intestines and has the form of a translucent sac filled with gas.
Figure: Internal structure of river perch. Digestive and excretory systems
The swim bladder forms in the perch embryo as an outgrowth of the intestines on the dorsal side. It loses contact with the gut during the larval stage. The larva, 2-3 days after hatching, should float to the surface of the water and swallow some atmospheric air to fill the swim bladder. If this does not happen, the larva cannot swim and dies.
By adjusting the volume of the swim bladder, the perch stays at a certain depth, floats or sinks. When the bladder contracts, excess gas is absorbed by the blood in the capillaries inner surface bubble. If the bubble expands, then the gas enters it from the blood. As the perch sinks into the depths, the bubble decreases in volume - and the density of the fish increases. This facilitates a quick immersion. When floating up, the volume of the bubble increases and the fish becomes relatively lighter. At the same depth, the volume of the fish bubble does not change. This allows the fish to be held without movement, as if hanging in the water column.
Unlike river perch, in other fish, such as carp, bream, roach, herring, the swim bladder maintains a connection with the intestine with the help of an air duct - a thin tube throughout its life. Excess gas flows out 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 to the fish. It also helps fish to hear better, as, being a good resonator, it amplifies sounds.
CLASS BONE FISH (OSTEICHTHYES)
Lesson 6. VARIETY OF BONE FISH IN CONNECTION WITH THE CONDITIONS OF EXISTENCE. EXTERNAL AND INTERNAL STRUCTURE OF BONE FISH ON THE EXAMPLE OF RIVER PERCH
Systematic position of the object
Chordata type
Subtype Vertebrates (Vertebrata)
Group Jaw (Gnathostomata)
Pisces superclass
Class Bony fish (Osteichthyes)
Subclass Ray-finned (Actinopterigii)
Superorder Bony fishes (Teleostei)
Order Perciformes
Family Perch (Percidae)
Representative - river perch (Regsa fluviatilis)
Equipment and materials
1. Fresh fish (one for two students).
2. Finished preparations: 1) opened fish; 2) the digestive system; 3) injected circulatory system; 4) the brain (one for two students).
3. Dissecting instrument: scalpel, scissors, tweezers, dissecting needle, office pins (one set for two students).
4. Baths (one for two students).
5. Tables: 1) tables for diversity; 2) appearance bony fish; 3) the general location of the internal organs; 4) the digestive system; 5) the circulatory system; 6) reproductive organs of the male and female; 7) the brain.
Introductory remarks
Variety of bony fish
The class of Bony fish includes more than 20 thousand. modern species... They live in a wide variety of water bodies: seas, oceans, rivers, lakes, ponds, streams.
Fish are adapted to a variety of aquatic conditions. They live in bodies of water with varying degrees salinity, avoiding only oversaturation with salt. They inhabit waters with different temperature regime: cold-blooded fish (ice, saber) live in waters with a temperature level of about 0 ° C. Some freshwater species (crucian carp) are able to survive during the winter freezing of water bodies. Fish are found in hot springs (from the family Carp-toothed). They are differently demanding on the oxygen content in water. Bony fishes have mastered different depths of the World Ocean and water flows from different speed moving water.
Representatives of this class are extremely diverse in their appearance and lifestyle (Fig. 25). By the nature of the relationship with the habitat, various ecological groups (life forms) are distinguished among fish. First of all, there are marine and freshwater fish... The majority of herring, cod (haddock, pollock, navaga, cod), tuna, mackerel, garfish, flounder, sailfish, blowfish and many others live in the seas of the World Ocean. Freshwater bodies of a temperate climate
Rice. 25. Environmental groups fish:
Fish living in the water column (nekton; pelagic). Marine: 1 - tuna; 2 - sailboat; 3 - box; 4 - moon fish; freshwater: 5 - crucian carp; 6 - carp; 7 - bream. Bottom fish (benthic). Marine: 8 - flounder-kalkan; 9 - sand goby; ten - angler; 11 - deep-sea angler; freshwater: 12 - common catfish; 13 - loach; 14 - pike. Specific adaptations in fish: 15 - flying fish; 16 - Mud Hopper
inhabited by representatives of carps (rudd, carp, silver carp, gudgeon, crucian carp, catfish, loach, etc.). Perch (perch, pike perch, ruff) and sticklebacks also live here. In the tropical waters of different continents live mnogopers, piranhas, shells, etc. There are species that occupy an intermediate position - these are anadromous fish. They live in a fresh or in a salty environment, depending on biological needs: for example, sturgeon and salmon fish go to spawn from seas to rivers, making so-called anadromous migrations, and river eels for spawning they swim from rivers to the ocean, their migrations are called catadromous.
Inside the reservoir, some fish keep in the water column (nekton, pelagic), others - near the bottom (bottom, benthic). The habitat leaves its mark on appearance fishes. In accordance with this, different ecological types fish. Nektonic (pelagic) fish are distinguished, as a rule, by their speed and good buoyancy. Their elongated body is torpedo-shaped (sailboats, mackerels, tuna) or strongly flattened from the sides (herring-like). Fish swim quickly due to frequent lateral oscillatory movements of the hind body, tail and well-developed caudal fin. Some salmon fish overcome the rapid oncoming streams of water and successfully move forward. The speed of a hunting sailboat is over 100 km / h, salmon is over 20 km / h.
There are species among pelagic fish that are not capable of developing great speed on one's own. They "attach" to the body of a fast-swimming fish (pilots) or stick to it (sticky fish).
Elongated paired fins help some fish to move quickly. They are used by sargan-like flying fish... Fleeing from predators, they jump out of the water and cover more than 200 m with a gliding flight.
Many nekton fish are gregarious, have a consistent behavior and are good at maneuvering in the water.
Bottom fish are rather slow, often lead single image life. Their body is either strongly flattened, like in flounders, or elongated and closer to the tail, compressed from the sides, like in catfish, loaches, moray eels. Their dorsal and anal fins grow, their wave-like movements are involved in the slow movements of these fish near the bottom. In some benthic fishes, modified pectoral fins make it possible to quickly move ("crawl") along the bottom (sea cocks, scorpions, gobies).
Deep-sea (abyssal) fish species also have specific adaptations.
By the nature of their diet, they distinguish: 1) active predators (large sturgeon, sailfish, tuna, etc.); 2) plankton beetles (herring, anchovies, moonfish); 3) benthic beetles (flounders, eels, anglers). In fresh water bodies, pike perch, pike, and perch are active predators; they eat plankton - roach, rudd, and other cyprinids extract food, digging in the bottom soil, there are herbivorous species among them.
General features of the organization
Despite the great external and systematic diversity, all bony fishes are characterized by specific traits distinguishing them from cartilaginous fish. The skeleton of bony fish is, to one degree or another, a bony integumentary or chondral origin. In the overwhelming majority of species, the intergill septa are reduced and the branchial lobes sit directly on the gill arches. The branchial apparatus is covered by the operculum. There is a swim bladder - an important hydrostatic organ. Fertilization in most bony fish is external, eggs are small, and their number is large.
The peculiarities of the organization of bony fishes will be considered on the example of the superorder of bony fishes from the subclass of ray-finned fishes, which make up more than 90% of the living fish species. Compared to cartilaginous fishes, bony fishes are characterized by a simplification of the skeleton of paired fins: there are no basals in the pectoral and pelvic fins, and radials in the ventral fins. The pectoral fins are located vertically under the body. The mouth is at the end of the head, but can be positioned differently. The caudal fin is homocercal. There is no spiral valve in the colon. In many teleost fish, the intestine has blind (pyloric) outgrowths and ends in the anus. There is no cloaca. The body is covered with bone scales, consisting of thin plates. Instead of the arterial cone, an aortic bulb appears.
Examine the external and internal structure of the perch.
Consider:
External structure
Dismemberment of the body into the head, trunk and tail; fins: paired - pectoral and abdominal, unpaired - dorsal, caudal (anal) and caudal; mouth opening; paired nostrils; eyes; gill covers; lateral line; genital, excretory and anus; bone scales.
Internal structure
Digestive system: oral cavity; pharynx; esophagus; stomach; small, large, rectum; pyloric outgrowths; liver; gallbladder; pancreas.
Respiratory system: four pairs of gills.
Circulatory system: bicameral heart (atrium and ventricle); aortic bulb; abdominal aorta; four pairs of branchial arteries. Follow the pattern of blood circulation using the preparation, figure and table.
Excretory organs: trunk kidneys; ureters; bladder.
Reproductive organs: testes; ovaries; reproductive ducts.
Central nervous system: brain (forebrain hemispheres with olfactory lobes, diencephalon, midbrain, cerebellum, medulla oblongata); eyes; the cross of the optic nerves (chiasm); spinal cord.
Sketch:
1) the general location of the internal organs; 2) the brain (top); 3) a diagram of the circulatory system (homework).
External structure
The body of bony fish, like cartilaginous fish, is divided into head, trunk and tail. The border between the head and the body is the branchial cleft, and between the body and the tail is the anus (Fig. 26). The mouth in teleost fishes is located at the front end of the head, which is why such fishes are called finite-moths, in contrast to the cross-mouthed shark fishes. It can be moved slightly up or down. There are large eyes on the sides of the head. They have a flat cornea and a round lens. The eyelids are missing. Ahead are visible paired nostrils - the organs of smell. Each nostril is divided by a valve into two openings: when the fish moves, water enters through the front and exits through the back. This is how the epithelium of the olfactory fossa is washed. The right and left nostrils do not communicate with each other or with the oral cavity.
The bony operculum is a characteristic formation for teleost fish. In this regard, instead of five gill openings, as in cartilaginous fish, on the surface of the body of the bony fish one gill slit is visible. Paired fins, in comparison with those of cartilaginous fish, are simplified and located in a vertical plane. The caudal fin is homocercal type. The vertebral column extends into the upper lobe of the caudal fin, but both fin lobes are the same. Dorsal fins
Rice. 26. Internal structure of the perch:
1 - mouth with teeth; 2 - operculum (part of it removed); 3 - bone scales; 4 - homocercal caudal fin; 5 - dorsal fins; 6 - anal fin; 7 - eye; 8 - nostril; 9 - lateral line; 10 - anus; 11 - genital opening; 12 - excretory hole; 13 - opened stomach with longitudinal folds; 14 - intestines; 15 - pyloric outgrowths; 16 - rectum; 17 - liver; 18 - gallbladder; 19 - pancreas; 20 - gill petals; 21 - spleen; 22 - swim bladder; 23 - kidney; 24 - ureter; 25 - bladder; 26 - ovary; 27 - atrium; 28 - ventricle; 29 - aortic bulb; 30 - abdominal aorta; 31 - gill stamens
equipped with soft branched or hard spiny rays. The rays are interconnected by a thin leathery membrane.
On the underside of the body, closer to the posterior end, there is a sub-caudal, or anal, fin. In front of it, in a common depression, there are three openings: anal, genital and excretory (cartilaginous fish have a cloaca). A clearly visible lateral line stretches along the body - an organ that perceives weak movements of water and infrasonic vibrations.
The body of the bony fish is covered with skin. It distinguishes between epidermis and cutis. On their border is the basement membrane. There are bone scales in the skin. Each scale lies with one edge in a skin pocket. The scales overlap each other in a tiled manner. The structure of the scales can be seen by highlighting it with tweezers and examining it under light or under a microscope. The scales can be cycloid, with a smooth inner edge, and ctenoid, with a serrated edge. Light (wide) and dark (narrow) annual rings are visible on the scales. In summer, with the intensive growth of fish, a significant increase in scales occurs - a wide,
light layer. In winter, the growth of fish and the growth of scales are insignificant - the layer is compacted, narrow, dark. Counting under a microscope light and dark rings on the scales of a fish, you can determine its age.
The cutaneous glands of the epidermis secrete mucus, which abundantly covers the body of the fish. It promotes better movement of fish in dense aquatic environments. For the color of fish, it is characteristic that the dorsal side is usually darker than the belly.
Internal structure
Opening
Take small fish v left hand belly up. Insert the sharp end of the scissors into the anus and make an incision along the abdominal side of the body towards the head, all the way to the mouth. In this case, it is necessary to press with scissors from the bottom up, without lowering their ends inward, so as not to damage the internal organs. Cut the shoulder girdle that will meet in the path of the incision. After making a longitudinal incision, place the fish on its right side, insert the blunt end of the scissors into the incision made near the anus and cut the body wall up towards the lateral line. Make a second cross-section near the operculum. Next, make a longitudinal cut along the side line, connecting both cross-sections. Unscrew the resulting patch of fabric and remove it.
At the front end of the body, expose the gills and heart. To do this, cut off the operculum and shoulder girdle. The heart lies almost immediately under the gills. In order to expose the brain, the skull cover must be carefully removed. Take the fish in your left hand with your back up, head away from you. Make a cross-sectional incision with scissors at the back of the cerebral box at the back of the head. Make the lateral incisions along the edges of the skull forwards. Finish off with a cross-cut at the front of your head (in front of your eyes). Grasp the skull roof with tweezers and carefully remove it. View the brain from above.
To view the brain from below, you need to cut the medulla oblongata and throw the brain forward. To see the structure of the eye, it must be removed from the orbit of the eye.
General arrangement of internal organs
On the opened fish, consider the general arrangement of the internal organs (see Fig. 26). The trunk musculature is clearly visible under the skin. It has a metameric structure.
Under the operculum there are four pairs of gill arches, on which there are gills, behind them below is a two-chambered heart. In front of the ventricle, the expansion of the abdominal aorta is noticeable - the aortic bulb, from which the abdominal aorta originates. In the anterior part of the abdominal cavity, a large liver is clearly visible, covering the stomach. There is a gallbladder, the duct of which opens into duodenum... An intestinal tube leaves the stomach. On the border of the stomach and intestines, pyloric outgrowths are visible. The pancreas of most fish is dispersed between the stomach and the adjacent intestinal loop. In one of the intestinal loops is a maroon spleen.
In the back of the body cavity lie the genitals - the testes or ovaries. The degree of their development depends on the season in which the fish was caught and on its age. Testes are distinguished by their milky cream color, as a result of which they are called milk. The ovaries are represented by elongated yellowish-orange sacs with a granular structure (eggs).
Above all the organs of the abdominal cavity, under the spinal column, lies the swim bladder. It is known to be absent in cartilaginous fish. The swimbladder is embryo formed from the dorsal wall of the intestine. It is an important hydrostatic organ that allows fish in the water column to maintain their body density in balance with buoyancy and gravity, maintaining neutral buoyancy at every depth. With the help of the swim bladder, the fish can perceive external pressure and transmit its changes to the organs of balance. In some fish, the swim bladder can serve as a respiratory organ, facilitate the perception and production of sounds. Under the spine, dark red kidneys stretch along the upper side of the body cavity. Teleost fish have a bladder.
Organ systems
Digestive system
The digestive system of bony fish in comparison with that of cartilaginous fish is lengthened, but less differentiated. The intestine is represented by a homogeneous tube, and the boundaries between the anterior, middle and posterior intestines are difficult to see.
The mouth is equipped with jaws that carry teeth. Often the teeth sit on the vomer and gill bones. Oral cavity passes into the wide pharynx, which, in turn, into the short esophagus and stomach. The size and shape of the stomach depends on the nature of the diet. In predatory
In fish (for example, in a perch), a voluminous stomach, capable of stretching, differs sharply from the subsequent sections of the intestine. If a large prey is swallowed, the stomach predatory fish expands due to stretching of the longitudinal folds of its walls. In herbivorous fish (for example, cyprinids), the boundaries between the stomach and intestines are hardly noticeable. The intestines leave the stomach. In teleost fishes, in contrast to lamellibranchs, it is longer and forms loops. In many fish, an increase in the absorptive surface of the intestine is carried out due to the blind processes, pyloric outgrowths extending from the anterior part of the small intestine. The river perch has three pyloric outgrowths, some salmon fish their number reaches four hundred. Carps, pikes, catfish do not have them.
The ducts of the liver, gallbladder and pancreas flow into the anterior part of the small intestine - the duodenum. Under the influence of enzymes in the alkaline environment of the intestine, the main components of food are broken down.
The small intestine smoothly passes into the large intestine, followed by the rectum, which ends with the anal (anal) opening.
All fish have a developed liver, an important digestive gland. Her secret: bile accumulates in the gallbladder, and then enters the anterior intestine through the bile ducts. Bile emulsifies fats and activates an enzyme that breaks down fat (lipase). In addition to participating in digestion, the liver plays an important role in detoxifying poisonous substances and harmful metabolic products. Therefore, it is called the barrier organ. Glycogen accumulates in the liver, urea is formed.
The second digestive gland, the pancreas, is usually diffusely or in the form of lobules located on the mesentery at the beginning of the small intestine. In some fish (for example, in pikes), it is a compact formation, in others (carp) it is scattered in the form of small fat-like inclusions between the bends of the intestinal tube. The pancreas secretes a complex of digestive enzymes that break down proteins, fats and carbohydrates. At the same time, it is an endocrine gland that ensures the balance of carbohydrate metabolism.
Respiratory system
The branchial apparatus of bony fish, in contrast to that of cartilaginous fish, is characterized by the absence of intergill septa. The branchial lobes sit directly on the branchial arches (Fig. 27). There is a gill cover - a hard bone plate,
Rice. 27. Gills of a shark (A, C) and bony fish (B, D):
A - frontal section through the oropharyngeal cavity of the shark; B - the same bony fish; B - cross section through the gill of a shark; D - the same bony fish: 1 - oropharyngeal cavity; 2 - esophagus; 3 - jaw arch; 4 - hyoid arch; 5 - squirt; 6 - internal gill slits; 7 - external gill slits; 8 - gill cover; 9 - branchial arches; 10 - gill petals; 11 - intergill septa
covering the gills, as a result of which only one branchial opening is preserved.
Each gill of bony fish is composed of two semi-gills attached to the bony branchial arch, to which the gill lobes are attached. They are pierced by the capillaries of the bringing branchial artery. Like cartilaginous fish, gill lobes are of ectodermal origin. On inside branchial arches are located gill stamens, forming a kind of filtering apparatus - a sieve that prevents the penetration of food to the gills, but allows water to pass into the peri-gill cavity. In teleost fishes, four pairs of branchial arches are well developed; the arch of the fifth pair is greatly shortened.
On the inner side of the operculum, the remains of an accessory semi-gill - pseudo-gill - can be noted. She most likely does not take an active part in the exchange of gases.
The act of respiration of bony fish is carried out thanks to the suction mechanism due to the movement of the operculum. When the operculum rises, the thin leathery operculum located along the edge of the operculum is pressed against the operculum under the influence of external water pressure. As a result, a space with
reduced pressure. This causes the flow of water entering through the mouth opening to rush through the pharynx into the peri-abdominal cavity. When the lid is lowered, excess pressure is created in the peri-gill cavity and water, pushing back each gill lid, is pushed out through the external gill openings. With the rapid movement of the fish, the flow of water passes through the branchial apparatus without the participation of the gill covers (ram breathing).
Circulatory system
The circulatory system of bony fish, when compared with the circulatory system of cartilaginous fish, differs in some features. Thus, in teleost fish (Fig. 28), the aortic bulb develops in the initial part of the abdominal aorta instead of the arterial cone. It is a thickening of the aorta and, like all blood vessels, has smooth muscles. There are only four pairs of efferent and efferent branchial arteries (in cartilaginous fish there are five pairs of them). The lateral veins disappear. The heart is located on the ventral side of the body near the head region. It is enclosed in a pericardial sac. The maroon atrium is clearly visible. Above the atrium is the venous sinus (sinus), which looks like a funnel and collects venous blood from the whole body. Down to
Rice. 28. Diagram of the circulatory system of teleost fish:
1 - atrium; 2 - ventricle; 3 - aortic bulb; 4 - abdominal aorta; 5 - bringing gill arteries; 6 - efferent branchial arteries; 7 - the roots of the aorta; 8 - dorsal aorta; 9 - carotid arteries; 10 - subclavian arteries; 11 - tail vein; 12 - right posterior cardinal vein; 13 - left posterior cardinal vein; 14 - renal portal system; 15 - subintestinal vein; 16 - the portal system of the liver; 17 - cuvier duct; 18 - hepatic vein; 19 - anterior cardinal or jugular veins; 20 - left portal vein of the kidney. Vessels with venous blood are painted black.
the atrium is adjoined by a bright red muscular ventricle. The difference in the color of the atrium and ventricle is due to the thickness of their walls. In the thin-walled atrium, venous blood shines through and creates a darker tone for the color of its wall. Thick muscular walls are clearly visible in the ventricle.
From the ventricle, the abdominal aorta extends forward, which at the base expands into the aortic bulb. (Recall that in lamellar gill fishes, an arterial cone lies in this place.) From the abdominal aorta, blood is directed through the gill arteries to the gills, in the capillaries of which it gives off carbon dioxide, then through the outgoing gill arteries it flows into the paired roots of the aorta and then goes to the dorsal aorta ... The vessels that carry arterial blood to the head are called the carotid arteries.
Through the dorsal aorta, which lies under the spine, blood flows to the tail. This aorta branches out to all organs: stomach, intestines, genitals, kidneys, fore and hind limbs. On the body of the opened fish, the dorsal aorta is clearly visible between the kidneys.
Venous blood, like in cartilaginous fish, returns to the heart through the unpaired tail vein, through the paired posterior and anterior cardinal (jugular) veins. The posterior cardinal veins, passing through the kidneys, disintegrate into a network of capillaries, forming the renal portal system.
The posterior cardinal veins on each side of the body merge with the anterior cardinal veins to form the Cuvier ducts. The subintestinal vein passes through the liver, splitting there into capillaries and forming the portal system of the liver. A short hepatic vein emerges from the liver and flows into the venous sinus.
Excretory organs
The excretory organs of bony fish are similar to those of cartilaginous ones. The difference lies in the fact that the excretory system in bony fish is not associated with the reproductive organs.
Long, dark red trunk kidneys (mesonephric) lie on the sides of the spine above the swim bladder. The ureters are wolffian canals that run along the inner edge of the kidneys. Bony fishes have a developed bladder.
Reproductive organs
Unlike cartilaginous fish, female bony fish lack Müllerian canals. The thin membrane of the saccular ovary continues into a narrow duct. A mature egg is thrown over it
out. In males, the reproductive products are expelled through the vas deferens and their gonads are not connected with the wolf canals. Thus, the Wolf channel performs only one function - the removal of metabolic products, i.e. ureter.
The division of the reproductive and excretory systems of bony fish is apparently due to the abundance of reproductive products.
Depending on the season and age of the fish, the degree of development of the reproductive organs can be different. In young specimens or in specimens caught outside the breeding season, the genitals are poorly developed. During the breeding season, the size of the gonads greatly increases.
central nervous system
Relative sizes brain in general, they increase in bony fish in comparison with cartilaginous ones (Fig. 29). However, the forebrain is relatively small. It is divided into two hemispheres by a longitudinal groove. The roof of the hemispheres does not contain nerve cells, it is epithelial. The main mass of the forebrain is made up of striated bodies lying in its thickness. Olfactory bulbs with olfactory nerves leading to the nasal capsules are visible in front. The cavities inside the hemispheres form two cerebral ventricles.
Diencephalon covered from above large hemispheres and the midbrain. On top of it is the pineal gland (endocrine gland), below the pituitary gland (endocrine gland) adjoins. Inside is the cavity of the third ventricle.
Midbrain in bony fish, it is noticeably larger than the other sections. Two large visual lobes are visible from above. The cerebellum is also quite large, especially in mobile fish species. It significantly covers the medulla oblongata.
Medulla elongated and gradually passes into the spinal cord. Visible from above is a diamond-shaped
Rice. 29. The brain of the perch from above:
1 - nasal capsule; 2 - olfactory lobes of the forebrain; 3 - forebrain; 4 - midbrain; 5 - cerebellum; 6 - medulla oblongata; 7 - spinal cord; 8 - diamond-shaped fossa; 9 - olfactory nerves
fossa - the fourth ventricle of the brain. When examining the brain from below, the forebrain with the olfactory lobes is clearly visible, a rounded outgrowth on diencephalon- the pituitary gland and in front of it - the intersection of the optic nerves (chiasm). From the brain of a bone fish, like a cartilaginous one, 10 pairs of cranial nerves depart.
Spinal cord lies in the canal formed by the superior arches of the vertebrae.
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