Features of the external structure of bony fish. Bony fish – Teleostei. General characteristics of bony fishes as the most numerous and diverse group of modern fishes. The main groups and their representatives. Structure of bony fish

Features of the external structure of bony fish. Bony fish – Teleostei. General characteristics of bony fishes as the most numerous and diverse group of modern fishes. The main groups and their representatives. Structure of bony fish

03.02.2023 Medicines

Thanks to the fact that every being is endowed, we all receive what we cannot live without - oxygen. In all land animals and humans, these organs are called lungs, which absorb the maximum amount of oxygen from the air. fish, on the other hand, consists of gills that draw oxygen into the body from the water, where there is much less of it than in the air. It is because of this that the body structure of this biological species is so different from all spinal terrestrial creatures. Well, let's look at all the structural features of fish, their respiratory system and other vital organs.

Briefly about fish

First, let's try to figure out what kind of creatures these are, how and how they live, and what kind of relationship they have with humans. Therefore, now we are starting our biology lesson, the topic “Sea Fishes”. This is a superclass of vertebrates that live exclusively in the aquatic environment. A characteristic feature is that all fish are jawed and also have gills. It is worth noting that these indicators are typical for everyone, regardless of size and weight. In a person’s life, this subclass plays an economic role important role, since most of its representatives are eaten.

It is also believed that fish were around at the dawn of evolution. It was these creatures that could live under water, but did not yet have jaws, that were once the only inhabitants of the Earth. Since then, the species has evolved, some of them turned into animals, some remained under water. That's the whole biology lesson. The topic "Sea fish. A brief excursion into history" is considered. The science that studies marine fish is called ichthyology. Let's now move on to studying these creatures from a more professional point of view.

General structure of fish

Generally speaking, we can say that the body of each fish is divided into three parts - head, body and tail. The head ends in the area of the gills (at their beginning or end - depending on the superclass). The body ends at the line of the anus in all representatives of this class sea creatures. The tail is the simplest part of the body, which consists of a rod and a fin.

Body shape strictly depends on living conditions. Fish that lives in the middle water column (salmon, shark) have a torpedo-shaped figure, less often - arrow-shaped. Those that float above the very bottom have a flattened shape. These include foxes and other fish that are forced to swim among plants or stones. They acquire more maneuverable shapes, which have much in common with snakes. For example, the eel has a highly elongated body.

The business card of a fish is its fins

Without fins it is impossible to imagine the structure of a fish. Pictures that are presented even in children's books certainly show us this part of the body of sea inhabitants. What are they?

So, fins are paired and unpaired. The paired ones include the pectoral and abdominal ones, which are symmetrical and move synchronously. Unpaired ones are presented in the form of a tail, dorsal fins (from one to three), as well as anal and adipose fins, which are located immediately behind the dorsal fin. The fins themselves consist of hard and soft rays. It is based on the number of these rays that the fin formula is calculated, which is used to determine a specific type of fish. The location of the fin is determined by Latin letters (A - anal, P - pectoral, V - ventral). Next, the number of hard rays is indicated in Roman numerals, and soft rays in Arabic numerals.

Fish classification

Today, all fish can be roughly divided into two categories - cartilaginous and bony. The first group includes such inhabitants of the sea, whose skeleton consists of cartilage of various sizes. This does not mean that such a creature is soft and incapable of movement. In many representatives of the superclass, the cartilage hardens and becomes almost bone-like in density. The second category is bony fish. Biology as a science claims that this superclass was the starting point of evolution. It once contained a long-extinct lobe-finned fish, from which all land mammals may have descended. Next, we will take a closer look at the body structure of fish of each of these species.

Cartilaginous

In principle, the structure is not something complex or unusual. This is an ordinary skeleton, which consists of very hard and durable cartilage. Each connection is impregnated with calcium salts, thanks to which strength appears in the cartilage. The notochord retains its shape throughout life, while it is partially reduced. The skull is connected to the jaws, as a result of which the fish skeleton has an integral structure. Fins are also attached to it - caudal, paired abdominal and pectoral. The jaws are located on the ventral side of the skeleton, and above them are two nostrils. The cartilaginous skeleton and muscular corset of such fish are covered on the outside with dense scales, which are called placoid. It consists of dentin, which is similar in composition to ordinary teeth in all land mammals.

How do cartilage breathe?

The respiratory system of cartilaginous animals is represented primarily by gill slits. There are from 5 to 7 pairs on the body. Oxygen is distributed to the internal organs thanks to a spiral valve that stretches along the entire body of the fish. A characteristic feature of all cartilaginous animals is that they lack a swim bladder. That is why they are forced to constantly be on the move so as not to sink. It is also important to note that the body of cartilaginous fish, which a priori live in salty waters, contains minimal amount this very salt. Scientists believe that this is due to the fact that this superclass has a lot of urea in the blood, which consists mainly of nitrogen.

Bone

Now let’s look at what the skeleton of a fish that belongs to the bony superclass looks like, and also find out what else is characteristic of representatives of this category.

So, the skeleton is presented in the form of a head, a torso (they exist separately, unlike the previous case), as well as paired and unpaired limbs. The cranium is divided into two sections - the brain and the visceral. The second includes the maxillary and hyoid arches, which are the main components of the jaw apparatus. Also in the skeleton of bony fish there are gill arches, which are designed to hold the gill apparatus. As for the muscles of this type of fish, they all have a segmental structure, and the most developed of them are the jaw, fin and gill muscles.

Respiratory apparatus of bony sea creatures

It has probably already become clear to everyone that the respiratory system of fish of the bony superclass mainly consists of gills. They are located on the gill arches. Also an integral part of such fish are gill slits. They are covered with a lid of the same name, which is designed to allow the fish to breathe even in an immobilized state (unlike cartilaginous ones). Some representatives of the bone superclass can breathe through the skin. But those that live directly below the surface of the water, and at the same time never sink deeply, on the contrary, capture air with their gills from the atmosphere, and not from the aquatic environment.

Structure of the gills

Gills are a unique organ that was previously characteristic of all primordial aquatic creatures that lived on Earth. In it, the process of gas exchange occurs between the hydroenvironment and the organism in which they function. The gills of fish of our time are not much different from those gills that were characteristic of the earlier inhabitants of our planet.

As a rule, they are presented in the form of two identical plates, which are penetrated by a very dense network of blood vessels. An integral part of the gills is the coelomic fluid. It is she who carries out the process of gas exchange between the aquatic environment and the fish’s body. Note that this description of the respiratory system is characteristic not only of fish, but of many vertebrate and non-vertebrate inhabitants of the seas and oceans. But read on to find out what is special about the respiratory organs that are found in the body of fish.

Where are the gills located?

The respiratory system of fish is mostly concentrated in the pharynx. It is there that the gas exchange organs of the same name are located on which they are attached. They are presented in the form of petals that allow both air and various vital fluids that are inside each fish to pass through. In certain places the pharynx is pierced by gill slits. It is through them that the oxygen that enters the fish’s mouth with the water it swallows passes.

A very important fact is that in comparison with the body size of many marine inhabitants, their gills are quite large for them. In this regard, problems with the osmolarity of blood plasma arise in their bodies. Because of this, fish always drink sea water and release it through the gill slits, thereby speeding up various metabolic processes. It has a smaller consistency than blood, therefore it supplies the gills and other internal organs with oxygen faster and more efficiently.

The breathing process itself

When a fish is just born, almost its entire body breathes. Each of its organs is permeated with blood vessels, including the outer shell, therefore the oxygen that is in sea water, penetrates the body constantly. Over time, each such individual begins to develop gill breathing, since the gills and all adjacent organs are equipped with the largest network of blood vessels. This is where the fun begins. The breathing process of each fish depends on its anatomical features, therefore in ichthyology it is customary to divide it into two categories - active breathing and passive. If everything is clear with the active one (the fish breathes “usually”, taking oxygen into the gills and processing it like a person), then with the passive one we will now try to understand it in more detail.

Passive breathing and what it depends on

This type of breathing is characteristic only of fast-moving inhabitants of the seas and oceans. As we said above, sharks, as well as some other representatives of the cartilaginous superclass, cannot remain motionless for a long time, since they do not have a swim bladder. There is another reason for this, namely, this is passive breathing. When a fish swims at high speed, it opens its mouth slightly and water automatically enters. Approaching the trachea and gills, oxygen is separated from the liquid, which feeds the body of the marine fast-moving inhabitant. That is why, being without movement for a long time, the fish deprives itself of the opportunity to breathe, without spending any strength and energy on it. Finally, we note that such fast-moving inhabitants of salt waters include mainly sharks and all representatives of mackerel.

The main muscle of the fish body

The fish is very simple, which, we note, has practically not evolved over the entire history of the existence of this class of animals. So, this organ is two-chambered. It is represented by one main pump, which includes two chambers - the atrium and the ventricle. The fish heart pumps only venous blood. In principle, this type of marine life has a closed system. The blood circulates through all the capillaries of the gills, then merges in the vessels, and from there again diverges into smaller capillaries, which already supply the rest of the internal organs. After this, the “waste” blood collects in the veins (fish have two of them - hepatic and cardiac), from where it goes directly to the heart.

Conclusion

So our short biology lesson has come to an end. The topic of fish, as it turned out, is very interesting, fascinating and simple. The organism of these sea inhabitants is extremely important for study, since it is believed that they were the first inhabitants of our planet, each of them is the key to the solution to evolution. In addition, studying the structure and functioning of a fish organism is much easier than any other. And the sizes of these inhabitants of the aquatic environment are quite acceptable for detailed consideration, and at the same time, all systems and formations are simple and accessible even for school-age children.

Exercise:

1. consider and sketch diagram of the structure of the pike brain (Fig. 1);

2. consider and sketch diagram of the circulatory system of pike (Fig. 2);

3. consider a diagram of a cross-section of a pike gill (Fig. 3);

4. note in the album:

1. progressive features of the organization of bony fishes, using the above characteristics.

Rice. 1. Pike brain from above, below and longitudinal section

1. olfactory bulbs; 2. optic chiasm; 3. body of the cerebellum; 4. striatum; 5. lateral projections of the cerebellum; 6. rhomboid fossa; 7. funnel; 8. lower lobes of the diencephalon; 9. optic lobes; 10. cerebellar valve; I–XII– cranial nerves

Rice. 2. Scheme of the circulatory system of pike

1. efferent branchial arteries; 2. anastomosis between the renal portal vein and the right posterior cardinal vein; 3. abdominal aorta; 4. atrium; 5. aortic bulb; 6. Cuvier's duct; 7. venous sinus; 8. tail vein; 9. anterior cardinal vein; 10. posterior cardinal vein; 11. ventricle; 12. hepatic vein; 13. inferior jugular vein; 14. portal vein of the liver; 15. renal portal vein; 16. efferent arteries of the branchial arches; 17. common carotid artery; 18. external carotid artery; 19. the external carotid artery itself; 20. internal carotid artery; 21. celiac artery; 22. hyoid artery; 23. dorsal aorta; 24. orbitonasal artery; 25. pseudobronchial artery; 26. subclavian artery; 27. roots of the dorsal aorta

Rice. 3. Scheme of a cross-section of a pike gill

1. gill rakers; 2. skeletal base of gill filament; 3. afferent branchial artery; 4. efferent branchial artery; 5. gill arch; 6. gill filaments

Lesson No. 15

Origin, diversity and ecology of bony fishes

Exercise:

1. consider the diagram of the origin of bony fish (Fig. 1);

2. consider and write down ecological groups of bony fishes (Table 1);

3. consider the diversity of bony fish (Table 2);

4. note in the album:

1. species of fish living in the Ulyanovsk region;

2. species of fish included in the Red Book of the Ulyanovsk region.

Rice. 1. Origin of bony fishes

26. Primitive bony fish; 27–30. Ray-finned ( Actinorterygii); (27. Cartilaginous ganoids ( Chondrostei); 28. Paleoniski ( Palaeonisci); 29. Bony ganoids ( Holostei); 30. Bony fish ( Teleostei)); 31. Multifeathers ( Brachiopterygii); 32 - 34 . Lobe-finned ( Sarcopterygii) (32. Dipnoi; 33. lobe-finned; 34. Ripidistii

Table 1

Ecological groups of fish

Basis of classification, sign	Group name	Representatives
Presence of poison	Poisonous fish	Sea dragon, stargazer, sea ruffe, sea bass, sea cat
Non-poisonous fish
Ability to generate electric fields	Highly electric species	Electric eel, electric stingray
Weakly electric types	Some stingrays
Non-electric types	Many marine and freshwater fish
Oxygen content in water	Fish that can withstand low oxygen levels	Carp, crucian carp, tench, catfish, loach
Fish with a moderate oxygen requirement	Sterlet, sturgeon, stellate sturgeon
Fish with a high oxygen requirement	Whitefish, smelt, perch, ruff, char
Habitat and lifestyle	Marine	Sprat, gobies, cod
Passing	Beluga, pink salmon, fisherman, eel, beluga
Semi-through	Roach, semi-anadromous forms of bream, pike perch
Freshwater rheophiles lake-river limnophiles	Asp, bersh, ruff Pike, perch, minnows Tench, crucian carp, carp
Nutritional nature	Predators	Pike perch, catfish, burbot
Benthophages	Bream, silver bream
Zooplanktivores	Bleak, sabrefish, bluegill
Phytoplanktonophages	Silver carp
Macrophytophages	Bel.Amur, rudd
Periphytonophages	Podust
Euryphages	Common crucian carp, roach
Reproduction method	Spawn-marking	Most fish
Viviparous	Guppies, swordtails
Type of spawning	Simultaneously spawning	Pike perch, bream
Portion-spawning	Ruff, bersh, silver bream
Spawning time	Spring spawners early spring non-spawning spring spawners spring-summer spawning	Ide, pike, perch, silver bream, bleak
Summer spawners	Catfish, carp
Autumn spawners	Trout, vendace
Winter spawners	Burbot
Spawning substrate	Phytophiles	Pike
Lithophiles	Ide
Cladophiles	Asp
Pelagophiles	Chekhon
Psammophiles	Gudgeon
Ostracophiles	Gorchak

table 2

Variety of bony fish

Subclass	Superorder	Squad	Family	View
Lobe-finned	Dipnoi	Horntoothed (Monopulmonate)	Horntoothed	Horntooth
Dipteroids (Two-pulmonated)	Squamate	Protopter, Amer. lepidoptera
lobe-finned	Coelacanths	Coelacanths	Coelacanth
Ray-finned	Cartilaginous	Sturgeon	Sturgeon	Beluga
Paddlefish	paddlefish
Bone ganoids	Mud fish		Amiya (mud fish)
Shell pike		Shelled pike
Multifeathers	Multi-feathered	Multi-feather	Multi-feather
Bony	Herring	Herrings	Tulka
Anchovy	Anchovy
Salmonidae	Salmonidae	Trout
Whitefish	vendace
Grayling	Grayling
Smelts	capelin
Pike	Common pike
Eels	Acne	river eel
Carp-like	Carp	Carp
Chukuchanovs	Buffalo
Balitorovye	Whiskered Char
Loaches	Loach
Catfish	Catfish	Som
Killer whales	killer whale
catfish	Channel catfish
Cyprinodontiformes	Poeciliaceae	Guppy
Garfish	Flying fish	Flying fish
Scumbreschukidae	Saira
Sarganaceae	Garfish
Codfish	cod	Pollock
Burbot	Burbot
Whiting	Hake
Anglerfishes	Anglerfish	Angler
Sticklebacks	Sticklebacks	Three-spined stickleback
Acicular	Needle	Sea Horse
Perciformes	Mackerels	Tuna
Sailboats	sailboat
Mullet	Loban
Perch	Zander
Goloveshkovye	Rotan
Gobies	Round goby
Snakeheads	Snakehead
Swordfish	Swordfish
Scorpiformes	Scorpionidae	Sea ruff
Kerchakovs	Slingshot
Golomyankovye	Golomyanka

We recommend starting to become familiar with the internal structure of bony fish by studying the features of the location of systems and organs using the materials presented in the lesson manuals, look at the pictures and diagrams. After theoretical preparation, proceed to the task on fish dissection .

Digestive system bony fish, compared to cartilaginous fish, has a number of differences. Overall, she less differentiated than in cartilaginous fish, especially in the intestinal area, where practically there are no clear boundaries between its departments.

The digestive tract begins oral cavity , in which they are located language (as in cartilaginous fish, does not have its own muscles) and bone teeth. The shape and number of teeth vary considerably among different species. Predatory fish have numerous sharp teeth, directed with their ends somewhat back, towards the pharynx, which helps to hold slippery prey. Some fish have teeth small needle-shaped(herring, carp species).

Some bottom fish (pufferfish, flounder, wrasse, etc.) have teeth in in the form of large plates, with the help of which dense plant tissues are crushed, shells and shells of benthic species (crustaceans, echinoderms) are crushed. This is also facilitated by powerful pharyngeal teeth, sitting on the last pair of gill arches.

Throughout life there is change of teeth, but it is irregular. In this case, new teeth grow in the spaces between existing teeth. Planktivorous fish(herring, carp) are deprived dental apparatus and have a peculiar filter device in the form of gill rakers that help filter plankton.

The oral cavity is followed wide throat , short esophagus , passing Vstomach . The size and shape of the stomach are determined by the type of food. U predatory fish (perch, pike) the stomach is more voluminous, with easily extensible walls and sharply demarcated from the intestine. Against , boundaries between the stomach and intestines herbivores fish (species of carp fish - silver carp, grass carp, etc.) little noticeable.

departs from the stomach intestines in the form of a long round tube forming a loop, but without external divisions into departments. In front small intestine there are special formations - pyloric growths, which delay the passage of food and increase the absorption surface of the intestine. In fact, they perform the same function as the spiral valve of cartilaginous fish. River perch has only three pyloric outgrowths, but in some fish (salmonids) their number reaches two hundred.

Anterior section the small intestine is duodenum, where do they flow liver ducts andpancreas. The liver is well developed in all fish. Entering the small intestine bile with the enzymes it contains, it promotes active digestion of food. In addition, the liver produces urea, accumulates glycogen. It also plays an important role in neutralizing toxic substances ( barrier organ).

Pancreas in many fish it is represented in in the form of small fat-like formations, lying on the mesentery in the bends of the intestinal tube. In some fish (pike) it is more compact.

Small intestine imperceptibly turns into thick, next comes rectum which ends anus.

Respiratory system bony fish gill type, presented four pairs gills; fifth – unpaired and greatly reduced. In the gill apparatus, unlike cartilaginous fish, no partitions separating the gills. The basis of each gill is arc(Fig. 26), on internal the side on which the short bones are located stamens, representing a filtering apparatus. It prevents food from coming back out.

WITH external the sides of the arc are soft gill filaments where capillaries branch and gas exchange occurs. Attached to the inner side of the gill cover is a rudimentary falsebranch, has lost its gas exchange function. Gill cover, covering the opening leading to the gills, is a hard plate consisting from several bones elements.

Breathing mechanism bony fishes are carried out mainly due to the movements of the gill cover, which ensures a constant flow of water through the mouth and gill apparatus. When inhaling, the gill covers move to the sides, and their thin leathery membranes are pressed against the gill openings. Due to this, a space with reduced pressure is formed in the peribranchial cavity; water enters the oropharyngeal cavity through the mouth opening and washes the gills. When the lids move back, excess pressure is created and water, bending their leathery edges, comes out through the holes.

With this method of breathing, fish are able to absorb up to 46–82% oxygen, dissolved in water. Some fish living in oxygen-deficient waters develop and other devices: cutaneous respiration can account for up to 20–30% or more of the total gas exchange; there are fish that additionally use atmospheric oxygen, capturing air with your mouth from the surface of the water.

Circulatory system bony fish (Fig. 27), compared to cartilaginous fish, is different a number of signs. Instead of an arterial cone, it departs from the ventricle aortic bulb, which has smooth muscles and is the beginning of the abdominal aorta. In the area of the gill apparatus only four pairs of afferents and efferents arteries.

The venous system has also undergone changes: no side veins; occurs in many species asymmetry of the renal portal system- only left cardinal vein forms a capillary network in the kidney tissue, the right cardinal vein passes through the kidney without interruption.

On the ventral side of the front part of the body is located heart , which is contained in pericardial sac. TO atrium , having smooth muscles and a dark burgundy color, adjacent venous sinus where venous blood collects. Departs from the atrium ventricle , characterized by a bright red color and thick muscular walls. The difference in coloring of the atrium and ventricle is due to the thickness of the walls - venous blood is visible in the thin-walled atrium.

Departs from the ventricle abdominal aorta, the beginning of which is aortic bulb. Blood from the abdominal aorta gill bearers arteries is sent to the gills, where it is enriched with oxygen, then along enduringgill arteries flow into steam rooms aortic roots. From the roots of the aorta are formed carotid arteries and dorsal aorta, breaking up into smaller arteries that carry blood to organs and tissues (in an opened fish, the dorsal aorta is clearly visible between the kidneys).

From the back of the body, venous blood collects through unpaired caudal vein, which splits into paired rear cardinal. Moving away from the head anterior cardinal(jugular), which at the level of the heart merge with the posterior cardinal veins to form Cuvier's ducts. The portal system is present only in the left kidney (see above). The portal system of the liver is formed by unpairedsubintestinalvein. From the liver, venous blood enters the hepatic veins into the venous sinus.

Excretory system. Excretory organs of bony fish similar to those of cartilaginous fish, however not related to the reproductive system. Trunk buds (mesonephros) long, dark red in color and located on the sides of the spine above the swim bladder. The ureters serve willfov channels, which stretch along the inner edge of the kidneys. Bony fish have bladder .

Reproduction system. Bony fish are dioecious; As a rare case, there is a manifestation of hermaphroditism (sea bass). The reproductive system is represented in males testes , in females - ovaries . The gonads of both males and females have independent ducts. In males wolf channel performs only the function of urination. Elongated structures extend from the ovaries, ending in a genital opening through which eggs are laid out ( Müllerian canals are absent).

Central nervous system and sensory organs.

Like other vertebrates, central nervous system comprises head And spinal sections.

Brain in bony fishes, in general, relatively larger in size, but of a more primitive structure than that of cartilaginous fish: forebrain relatively small, in his roof absent nervous substance, cavities of the cerebral hemispheres (lateral ventricles) not separated partition . The most pronounced development midbrain and cerebellum.

Forebrain looks like small hemispheres in which there is no brain matter (their epithelial roof). The main part of the hemispheres consists of the so-called striatum, lying on the bottom. In the front are olfactory lobes, the sizes of which are inferior to those of cartilaginous fish.

Diencephalon covered by the anterior and middle parts of the brain. In its back part there is a small endocrine gland - pineal gland and on the lower side there is a rounded outgrowth - pituitary.

Midbrain It has large optic lobes , where incoming processing takes place visual information, and the abdominal part contains communication centers with the cerebellum, medulla oblongata and spinal cord.

Cerebellum overlaps the midbrain and significantly covers the beginning medulla oblongata, which has rhomboid fossa(fourth ventricle). The cerebellum determines the activity of somatic muscles, the activity of movement and the maintenance of balance.

Like cartilaginous fish, from the brain ten pairs of nerves arise , coordinating the work of systems and organs.

The spinal cord does not have any special differences in comparison with cartilaginous fish, but the autonomy of its functions is less pronounced.

Sense organs bony fish are diverse, but the most important in their life are smell and taste.

Despite the weak development of the olfactory lobes of the forebrain, compared with cartilaginous fish, the resolution in capturing smells in most bony fishes it is quite high, especially in schooling and migratory fishes. This is due to the special structure olfactory bags which have well-developed folds olfactory epithelium And flickering eyelashes, increasing the flow of water through the nasal openings.

Taste buds, defining the function taste , located in the oral mucosa, antennae, body surface and fins. They allow you to clearly recognize all taste sensations - bitter, sweet, sour and salty.

Lateral line organs well developed and represent channels passing through the thickness of the skin. With the help of small holes in the scaly cover of fish, they communicate with the external environment. Thanks to the sensory cells of the canal walls, fish receive information about water fluctuations, navigate its currents, and determine the location of prey or dangerous objects.

Touch function performed by clusters of sensory cells (“tactile corpuscles”), scattered over the entire surface of the body. There are especially many of them concentrated near the mouth - on the antennae, lips, and also on the fins, which allows the fish to feel the touch of hard objects.

In the superficial layers of the skin there is thermoreceptors , with the help of which fish perceive temperature changes in the environment with an accuracy of 0.4 degrees. On the head of the fish there are receptors, catching changes electric and magnetic fields and thus contributing to the spatial orientation and coordination of actions of individuals of schooling fish.

A number of species have electrical organs, which are modified areas of the body’s muscles. They can be located on the head, sides and tail of fish, determining orientation towards other individuals, methods of defense and attack. They serve as receptors "neuroglandular cells" located on the body and in the lateral line channels.

Vision mainly helps fish in short-range orientation(up to 10–15 m), because due to the structure of the eye they are “myopic”: the lens is spherical, the cornea is flat, the accommodation of the eye is insignificant. However, the retina of the eyes of bony fishes contains not only sticks(black and white vision), but also cones, defining color perception. Vision is important when searching for food, protecting from danger, and intraspecific communication, especially during the breeding season.

Organ of hearing and balance presented only inner ear, which is surrounded by a cartilaginous capsule with its external ossification. The basis of the inner ear is membranous labyrinth with three semicircular canals and an oval sac, what makes up the vestibular apparatus, or organ of balance. Next to it is the actual organ of hearing - round pouch , equipped with a hollow outgrowth - lagena. The sensory cells of the lagena and saccules serve as sound receptors. Inside the sacs and lagena lie auditory pebbles, or otoliths, enhancing the perception of information about body position. In a number of fish, the vestibular apparatus is connected to the swim bladder, which increases sensitivity when maintaining balance.

general arrangement of internal organs .

Directly under the operculum visible four pairs gills arcs are bright red. Behind them is two chamber heart with the aortic bulb, from which it originates abdominal aorta, carrying blood to the gill apparatus. Between the gill cavity and the abdominal cavity there is thin vertical partition.

Located in the anterior part of the abdominal cavity liver, under which lies stomach with the one moving away from him intestines. At the beginning of the intestinal tube, finger-shaped pyloric growths(perch has three). Pancreas in most fish, in the form of lobules, it is located on the mesentery at the level of the stomach and the beginning of the intestine. In one of the intestinal loops there is maroon spleen(contains hematopoietic and lymphoid tissues).

Lies under the spinal column swim bladder, which represents hydrostatic organ, allowing the fish to change the position of its body in the water column. Functionally it is connected with inner ear, which allows the fish to determine external pressure and, transmitting its changes to the auditory apparatus (otoliths), maintain balance. In some fish, the swim bladder takes part in gas exchange and can contribute to the production of sounds.

Closer to the tail are the genitals - testes or ovaries. Testes smooth, milky cream color, which is why they got the name milk. Ovaries have granular structure and yellowish-orange color.

Rice. 29. External and internal structure of perch:

1 – mouth with teeth, 2 – gill cover, 3 – bony scales, 4 – homocercal caudal fin, 5 – anal fins, 6 – eyes, 8 – nostril, 9 – lateral line, 10 – anus, 11 – genital opening, 12 - excretory opening, 13 - open stomach, 14 - intestine, 15 - pyloric outgrowths, 16 - rectum, 17 - liver, 18 - gall bladder, 19 - pancreas, 20 - gills, 21 - spleen, 22 - swim bladder , 23 – kidneys, 24 – ureters, 25 – bladder, 26 – ovaries, 27 – atrium, 28 – ventricle, 29 – aortic bulb

The complex of progressive structural features of bony fishes is especially clearly and fully expressed in the youngest and most progressive branch of this class - the bony fishes Teleostei, which includes the vast majority of living forms of this class.

The axial skeleton of bony fishes is composed of numerous bony vertebrae. The vertebral bodies are concave in front and behind - such vertebrae are called amphicoelous. The space formed between the concave surfaces of adjacent vertebrae and the narrow canal running through the center of the vertebral bodies are filled with the remains of the notochord (Fig. 34, 1), which has a beaded shape. The spine is divided into two sections: the trunk (pars thoracalis) and the caudal (pars caudalis); the vertebrae of these sections differ in their structure.

Like cartilaginous fish, the skull of bony fishes consists of two sections: the axial skull, or braincase (neurocranium), and the facial, or visceral, skull (splanchnocranium). But unlike cartilaginous fish, the skull of bony fish is almost entirely formed by bone tissue and consists of numerous individual bones.

In the internal structure of bony fishes, the most striking feature is the appearance of a swim bladder - a hydrostatic organ that increases “buoyancy” and allows the fish to maneuver without significant expenditure of energy. In cartilaginous fish this is only possible during movement, which naturally requires significant energy expenditure. The swim bladder also performs some additional functions: it serves as a resonator for the sounds produced by the fish, can serve as a reservoir for accumulating a reserve supply of oxygen (and in some species, as an organ of air respiration), etc.

The absence of a spiral valve, characteristic of cartilaginous fish, is compensated in bony fish by an increase in the relative length of the intestine and the development of pyloric appendages in many species, which also increase the total absorptive surface of the intestine. These transformations help increase the intensity and efficiency of digestion.

Unique structure genitourinary system bony fish. They, like cartilaginous fish, have mesonephric (trunk) kidneys with ureters corresponding to Wolffian canals. Unlike cartilaginous fish, bony fish have bladder. As for the reproductive ducts of bony fish, they are special formations that are not homologous to either the Wolffian or Müllerian canals. These features arise as a result of changes in the course of embryonic development of the gonads and, apparently, are associated with adaptation to the excretion of a large number of reproductive products; The fertility of bony fish is much higher than that of cartilaginous fish. However, the considered features of the genitourinary system are a specific property only of bony (and some other bony) fish and did not receive further development in the evolution of vertebrates.

The skeleton contains bone tissue; the skull of bony fish is almost entirely formed by bone tissue and consists of numerous individual bones. In the internal structure of bony fishes there is the appearance of a swim bladder, the gills have become not attached plates, but separately hanging petals, covered with an operculum, and there is a bladder.