Home Vegetables The oldest bony fish are cross-finned fish. Origin of cartilaginous and bony fish. General characteristics of the superclass of fish

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The oldest bony fish are cross-finned fish. Origin of cartilaginous and bony fish. General characteristics of the superclass of fish

Bony fish are the largest class of vertebrates, with about 20,000 species. The most ancient representatives of this class descended from cartilaginous fish at the end of the Silurian. Currently, 99% of the class belongs to the so-called bony fish, which first appeared in the middle of the Triassic, but their evolution was slow for a long time and only at the end of the Cretaceous period accelerated sharply and reached an amazing heyday in the Tertiary period. They inhabit a wide variety of water bodies (rivers, seas and oceans down to the greatest depths, found in Arctic waters). Thus, bony fishes are vertebrates most adapted to living in the aquatic environment. In addition to bony fish, the class also includes several dozen species of ancient bony fish that have retained some of the features of cartilaginous fish.

general characteristics

Most species of this class are adapted to fast swimming, and their body shape is similar to that of sharks. Less fast swimming fish have a taller body (for example, in many carp species). Species leading a sedentary lifestyle at the bottom (for example, flounders) have the same flattened body shape as rays (Fig. 81).

Rice. 81. Bony fish:

1 - herring (family Herring); 2 - salmon (family Salmon); 3 - carp (family Carp); 4 - catfish (family Catfish); 5- pike (family Pike); 6- eel (family Acne);

7 - pike perch (family Perch); 8 - river goby (family Goby); 9 - flounder (family flounder)

Veils. The body length of fish is different - from a few centimeters to several meters. In contrast to cartilaginous and ancient bony fish, there are many small species among teleosts that have mastered small biotopes that are inaccessible to larger species. The skin of the overwhelming majority of teleost fish is covered with small bony, relatively thin scales that overlap each other in tiles. They protect fish well from mechanical damage and provide sufficient flexibility to the body. Distinguish between cycloid scales with a rounded upper edge and ctenoid with small teeth on the upper edge. The number of scales in longitudinal and transverse rows for each species is more or less constant and is taken into account when determining the species of fish. In cold weather, the growth of fish and scales slows down or stops, so annual rings are formed on the scales, counting which you can determine the age of the fish. In a number of species, the skin is bare, devoid of scales. There are many glands in the skin, the mucus secreted by them reduces, like other fish-like fish, friction during swimming, protects against bacteria, etc. In the lower layers of the epidermis there are various pigment cells, thanks to which fish are hardly noticeable against the background of their environment. In some species, body coloration may change in accordance with changes in substrate coloration. Such changes are carried out under the influence of nerve impulses.

Nervous system. The size of the brain in relation to the size of the body is somewhat larger than that of cartilaginous fish. The forebrain is relatively small in comparison with other regions, but its striated bodies are large and, through their connections with other parts of the Central nervous system, influence the implementation of some rather complex forms of behavior. Nerve cells in the roof of the forebrain are absent. The diencephalon and the epiphysis and pituitary gland separated from it are well developed. The midbrain is larger than other parts of the brain, in its upper part there are two well-developed visual lobes. The cerebellum is large in well-swimming fish. The size and complexity of the structure of the medulla oblongata and the spinal cord has grown. The subordination of the latter to the brain, in comparison with that observed in cartilaginous fish, increased (Fig. 82).

Rice. 82. The brain of a perch:

1 - olfactory capsule; 2 - olfactory lobes; 3 - forebrain; 4 - midbrain; 5 - cerebellum; 6 - medulla oblongata; 7 - spinal cord; 8 - the orbital branch of the trigeminal nerve; 9 - auditory nerve; 10 - vagus nerve

Sense organs. There were some complications in the sense organs. Seismosensory organs are located in the channels of the lateral walls of the body and form a dense network on the head. The round sac of the labyrinth is more developed, and contrary to the long-standing opinion that bony fishes perceive only rough shaking of the environment, numerous experiments have shown that they react to various sound vibrations and use them to communicate within the population. The ability to perceive various chemical irritants is very well expressed. Many species perceive even small changes in temperature in their surrounding water. The vision of teleost fish is calculated, like that of other fish, at close range; the lens is spherical, unable to change its curvature, the sharpness of the image is achieved by moving it with the help of contraction of a special muscle - the crescent bone.

Skeleton. During the evolution of the class in question, the skeleton gradually became ossified. The chord was preserved only among the lower representatives of the class, the number of which is insignificant. When studying the skeleton, it must be borne in mind that some bones arise as a result of the replacement of cartilage with bone tissue, while others develop in the connective tissue layer of the skin. The first are called the main, the second - the integumentary bones.

The cerebral section of the skull is a box that protects the brain and the senses: smell, sight, balance and hearing (Fig. 83).

Rice. 83. The layout of the bones in the skull of a teleost fish. The visceral skeleton is separated from the cerebral skull. The operculum is not drawn. The main bones and cartilage are covered with dots, the integumentary bones are white:

/ - angular; 2 - articulated; 3 - the main occipital; 4 - the main wedge-shaped; 5 - copula; 6 - dental; 7 - lateral olfactory; 8 - outer pterygoid; 9 - inner pterygoid; 10 - lateral occipital; 11 - frontal; 12 - pendants; 13 - hyoid; 14 - ossified ligament; 15 - lateral wedge-shaped; 16 - middle olfactory; 17- posterior pterygoid; 18 - maxillary; 19 - nasal; 20 - eye-wedge-shaped; 21 - parietal; 22 - palatine; 23 - premaxillary; 24 - parasphenoid; 25 - square; 26 - superior occipital; 27 - additional; 28 - opener; 29-33 - ear bones; I-V - branchial arches

The roof of the skull is formed by paired nasal, frontal, parietal bones. The latter adjoin the superior occipital bone, which, together with the paired lateral occipital bones and the main occipital bone, forms the back of the skull. The bottom of the skull consists (from front to back) of a vomer, a parasphenoid (a wide, long bone, very characteristic of the skull of fish) and a main bone. The front of the skull is occupied by a capsule that protects the organs of smell; on the sides are the bones surrounding the eyes, and a number of bones (usually 5) that protect the organs of hearing and balance.

The visceral part of the skull consists of a series of bony branchial arches that support and protect the branchial apparatus and the anterior part of the digestive system. Each of the mentioned arcs includes several bones. Most fish have 5 arcs to which the gills are attached (on each side). At the bottom, the branchial arches are connected to each other, and the anterior one is connected to the hyoid arch, which consists of several bones. The upper of these bones - the sublingual-maxillary (hyomandibular) is attached to the cerebral section of the skull in the area of the auditory section and is connected through the square bone with the bones surrounding the oral cavity. Thus, the hypoglossal arch serves to connect the branchial arches with the rest of the visceral section, and its upper bone - with the cerebral section of the skull.

The edges of the mouth and the entire oral cavity are reinforced with a number of bones. The maxillary row of bones is represented (on each side) by the intermaxillary and maxillary bones. Next comes a series of bones: palatine, somewhat pterygoid, and square. The square bone at the top is adjacent to the pendant (hyomandibular), and at the bottom - to the lower jaw. The latter consists of several bones: dental (largest), angular and articular, which connects to the square bone. In ancient fish (which still had a cartilaginous skeleton), all the arches of the visceral part of the skull were carried by the gills; later, the anterior arches of these arches turned into the hyoid arches and jaw rows of bones.

The vertebral column consists of a large number of biconcave (amphitic) vertebrae, in the intervals between which the remains of the chord are preserved. A long spinous process extends upward and slightly backward from each vertebra. The bases of these processes are separated and they form a canal through which the spinal cord runs. Two short transverse processes extend from the underside of the vertebral bodies, to which long curved ribs are attached in the trunk region. They end freely in the muscles and form the frame of the lateral walls of the body. In the tail part of the body, only the lower spinous processes extend downward from the vertebrae.

Organs of movement. In bony fishes, as in cartilaginous fishes, they are represented by unpaired (dorsal, anal, caudal) and paired (pectoral and pelvic) fins. The fin lobes are supported by bony rays. Some rays are soft, consisting of a number of bony sections, while others are hard, solid, the ends of which are pointed in many species. The rays of the dorsal and anal fins rest on bones - basals (fin props), which lie in the muscles at the edge of the body. Paired fins rest on the girdle of the extremities lying between the muscles: the pectorals - on the shoulder (or front) girdle, consisting of several bones, the upper of which is attached to the skull (Fig. 84), the pelvic fins - on the pelvic (or posterior) girdle, consisting, as usually a pair of bones.

Rice. 84. Belt of the forelimbs and pectoral fin of ray-finned fish:

/ - primary belt; 2 - scapula; 3 - coracoid; 4 - basal elements; 5 - radials; 6 - skin rays

The caudal fin rays rest on the posterior part of the vertebral column. In lower bony fishes (as in cartilaginous fishes), the caudal fin is heterocercal, the upper lobe of which is much larger than the lower lobe. In teleost fishes, the caudal fin is homocercal, since both lobes are approximately equal.

The gradual ossification of the skeleton was of great adaptive value in the evolution of fish, since it contributed to the development of strong support for muscles and reliable protection of the central nervous system and internal organs. Since a large number of small bones can be part of the bone skeleton, this was an important condition for the emergence of many species with a small body size.

The bone skeleton has a greater mass than the cartilaginous one, which could make it difficult for the fish in question to swim. Therefore, in the latter, the swim bladder developed by branching from the front of the intestine, which lies above the intestine and is filled with a mixture of gases (nitrogen, oxygen and carbon dioxide), due to which the body weight of the fish has significantly decreased. In primitive bony fish species (open-bladder), the bladder remains connected to the intestinal tube throughout life. In most species (closed vesicular) that appeared later, it is completely separated from the intestine. In the walls of the bubble there are dense plexuses of capillaries, which ensure its filling with gases. The volume of gases in an enclosed space, as is known, can greatly decrease during compression and, conversely, increase sharply with decreasing compression. The increase and decrease in the volume of the bladder occurs due to the work of the muscles surrounding the abdominal cavity. Therefore, the swim bladder not only reduces body weight, but also plays a hydrostatic role, that is, it makes it easier for the fish to rise upward when it expands and sinks when it contracts. The swim bladder was reduced in a number of fish species that lead a sedentary lifestyle at the bottom, and in those species that, possessing strong muscles, are able to quickly move upward or inward. The presence of a bubble in the latter could cause, during its rapid ascent, its strong expansion and eversion of the viscera, as has been proven by many observations. In some fish, a swim bladder connected by a row of bones (Weber apparatus) with a labyrinth facilitates the transmission of some sound waves to the latter.

Digestive system. Most bony fish have some peculiarities. There is no spiral fold; an increase in the intestinal surface occurs due to its lengthening. In addition, pyloric processes extend from the initial part of the intestine in many higher teleost fishes, which also increase the surface of the intestine. Feces are removed through the anus; no cloaca. The structure of the system under consideration is different depending on the nature of the diet. Predators attacking other fish and larger invertebrates have a wide mouth, usually seated with large, sharp teeth; the stomach is large, sharply separated from the esophagus and the beginning of the intestine; the total length of the intestine is much shorter than in herbivorous species. In the latter, and especially in species feeding on small invertebrates and organic remains, teeth are small or absent; the stomach is almost indistinct or absent. Cyprinids and some other fish in the pharynx have special pharyngeal teeth for mechanical processing of food. The liver is well developed, although it does not reach the same size as in many cartilaginous fish. The pancreas is represented by separate lobules located in the liver or in the walls of the initial part of the intestine, that is, it does not yet have a compact form, but it is better developed than in cartilaginous fish.

The study of the food composition of different fish, especially commercial fish, is of great practical importance, since if there is information about the qualitative and quantitative composition of the organic world of certain water bodies, it makes it possible to find out which species and in what quantity can inhabit each of them, at what combination of species the food base reservoirs can be comprehensively used without prejudice to its subsequent restoration, etc. These issues are specially studied in courses on fish farming.

Respiratory system. The main organs of the respiratory system are the gills, consisting of many petals attached by the proximal ends to the gill arches, in contrast to the gill plates of cartilaginous fish, attached on one side to the intergill septa. Consequently, the surface of the gills of bony fish is much larger than that of cartilaginous fish. The mechanism of inhalation and exhalation is also more perfect. A fairly significant part of gas exchange (on average about 10%) occurs through the skin. The swim bladder and some parts of the intestine can take part in gas exchange.

Circulatory system. The heart consists of an atrium and a ventricle, the circle of blood circulation is one. There is no arterial cone in teleost fish, and the arterial vessel extending from the ventricle begins with the aortic bulb. The number of erythrocytes is much higher than that of cartilaginous fish, which contributes to an increase in the intensity of dissimilation processes. The spleen is well developed (Fig. 85).

Rice. 85. Opened perch (female):

/ - gills; 2 - heart; 3 - liver; 4 - swim bladder; 5 - spleen; 6 - ovary; 7 - stomach; 8 - pyloric appendages; 9 - intestine; 10 - bladder; 11 - anal opening; 12 - urogenital opening; 13 - stamens of the branchial arch

Excretory system. In the excretory system, the trunk kidneys play a special role, located in the form of two long dark red narrow ribbons along the spinal column. The distal ends of the ureters (wolf canals) are connected and opened outward by a common opening behind the anus. The bladder departs from the distal part of the fused ureters.

Reproduction. The reproductive system of teleost fish is simplified in comparison with cartilaginous and ancient bony fish, but it is capable of producing a large number of gametes. Two elongated testes (often called milks) are located under the kidneys on the sides of the swim bladder. The seed does not come out through the Wolffian canal, but through a short tube formed by the sheath of the testis. Both vas deferens open outward with a common genital opening behind the anal and urinary openings or with a common urogenital opening. The ovaries (there are usually two of them) during the breeding season are bulky sacs filled with eggs, which come out not through the Müllerian canals (they are reduced), but through short tubes that go from the gonads and open outward as an independent opening or into the common urogenital opening. Consequently, mature eggs do not enter the body cavity, but quickly leave the body of females. Fertilization in the overwhelming majority of bony fish species is external. Internal fertilization, as well as viviparity, is characteristic of relatively few representatives of this class. Caviar is thrown onto aquatic plants and, less often, onto other underwater substrates, and in a minority of species, into the water column. In connection with external fertilization, the mass of gametes, zygotes and fry perishes. Therefore, the fertility of bony fish is very high. For example, carp produces more than 1 million eggs, pike - about 1 million, halibut - 2-3.5 million, cod - up to 1 million. The maturation of the gonads depends on various factors - internal and external. The pituitary hormones have an accelerating effect on the maturation of the gonads.

Fertilization of eggs can be carried out in artificial conditions by mixing eggs and fish seeds in the presence of a small amount of water. Currently, this technique is well developed and successfully applied on a large scale in the so-called fish hatcheries. Fertilized eggs develop in favorable conditions, usually to the stage of fry, capable of foraging in natural reservoirs, where they are released. Such measures contribute to the restoration of valuable commercial fish, the number of which has sharply decreased due to pollution of water bodies, difficulties in migrating fish to their breeding sites, and their intensive prey.

The growth rate of fish is influenced by various living conditions: nutrition, temperature, the composition of substances dissolved in water, etc. Growth, depending on changes in living conditions, is uneven. It is known, for example, that it slows down in cold weather, which can be traced on the annual rings of fish scales. Studies of the growth of fish in different reservoirs are of great theoretical and practical importance, since thanks to them it is possible to find out what conditions favor it, which, on the contrary, delay it, how the stocks of commercial fish are restored, etc.

The life span of fish is different: some live less than a year (some types of anchovy, etc.), others - several years (Pacific salmon - chum salmon, pink salmon, etc.), others - several tens of years and even about 100 years (large sturgeon, pike, carp, etc.).

Fish-like (jawless and fish) have adaptations (that have arisen over a long evolution) for movement in water, obtaining food, rescuing from predators, etc.

On the basis of these adaptations, they developed regular movements characteristic of different periods of their life - migration. The shortest and most frequent of these are diurnal migrations. They depend on the time of day. Longer seasonal migrations depend on the season of the year. These include, in particular, wintering migrations, when fish go to a depth and in a sedentary state, without eating, wait out an unfavorable season for them. For example, anchovy, which feeds and reproduces in the Sea of Azov, overwinters in the Black Sea, since the water in it does not undergo such strong cooling as in the shallow Sea of Azov.

Long, in a number of species distant migrations, called forage migrations, many fish make to places where there are enough organisms on which they feed. For example, after the end of the breeding season in the Atlantic Ocean, cod migrates to the Barents Sea and some other northern seas.

Spawning migrations are widespread among fish, ensuring their reproduction sometimes in very distant places from areas where they live, feed and grow for a long time. These species include anadromous fish that live in the seas, but breed in rivers flowing into these seas. So, very valuable sturgeon fish (sturgeon, stellate sturgeon, beluga, etc.) live in the Caspian, Azov and Black seas before the onset of the breeding season, and for spawning they go to the upper reaches of the rivers flowing into the named seas. After that, they return to the seas, where they live until the next breeding season. The fry, which have developed from eggs deposited and fertilized in rivers, are carried by the current to the seas, where they grow for a long time.

Such fish reproduce several times during their life. But there are fish that live for several years in the oceans and seas, but reproduce only once in a lifetime. These include Pacific salmon (chum salmon, pink salmon, chinook salmon, etc.), which go to the Far Eastern rivers of Russia, the rivers of North America, Japan, Korea, China for breeding, in which they spawn. During spawning migrations, fish, as a rule, do not feed and die as a result. Unlike the aforementioned fish, the freshwater eel, which lives for a long time (up to 20 years or more) in the rivers of Europe, never reproduces there, but makes distant migrations (7000-8000 km) to the Sargasso Sea, where it spawns and then dies. Eel fry are caught by the Gulf Stream and after 2 years they reach the shores of Europe and then enter the rivers.

There is also a group of semi-anadromous fish living in the desalinated parts of the seas and breeding in the lower reaches of rivers flowing into these seas. These include the populations of roach, carp, bream living in the north of the Caspian Sea.

Migrations are also known in many invertebrates with rather efficient modes of movement. In vertebrates, they are the most complex and long-lasting due to the high development of their nervous, motor, and other organ systems. Migrations are carried out by hereditarily fixed instincts that have developed as a result of long-term natural selection. Thanks to migrations, animals make full use of various parts of their ranges. Migration studies are of great importance for nature conservation and the rational use of commercial species of animals.

The practical importance of fish. Bony fish are sources of protein and a number of other substances necessary for a good nutrition of people. World population during the XX century. and especially in recent decades has increased greatly. In this regard, the catch of fish (as well as aquatic molluscs, crustaceans and other invertebrates) has increased dramatically. In pre-revolutionary Russia, fish was caught mainly in rivers, in other freshwater bodies of water and in the southern seas of the country.

The development of pond fish farming plays a significant role in increasing fish production. In ponds, fish feed on insect larvae (mainly chironomid larvae), crustaceans, worms, etc. In order to increase the fish productivity of ponds, fish are fed with oilcakes, legumes, etc. Most often, various races of carp are grown in ponds. Together with carp in ponds, you can breed crucian carp, tench and other types of fish that are not competitors in nutrition. In properly organized pond farms, there are several types of reservoirs (for breeding, raising fry, feeding marketable fish, wintering, etc.). In such farms, you can get 15-20 centners of fish and more from 1 hectare. Pond fish farming is one of the lucrative livestock industries.

Systematic review

Nowadays existing bony fish belong to two subclasses - ray-finned and lobe-finned fish.

Most species of fish belong to the class of bony fish - over 20,000. There are two classes of bony fish: ray-finned (Actinopterygii) and lobe-finned (Sarcopterygii). Fish are the largest class of vertebrates in terms of the number of species; they number up to 20-25 thousand species, which are combined into 33 orders. Units of the class of bony fish: amie-like, aravan-like, atherine-like, batracho-like, beryx-like, gonorhynchiformes, puffer-like, flounder-like, carps-toothed, carp-like, cephalic-like, cetacean-like, beak-like, spiky-like, myciform-like, salmon-like , percopsiformes, sucker-shaped, horn-toothed, sargan-like, herring-like, scorpion-like, merged-saber-like, sun-like, cat-like, spin-like, tarpon-like, cod-like, eel-like, angler-like, coelacanth-like.

I will give a description of some orders of bony fish.

Sturgeon detachment. Representatives of the order sturgeon belong to the subclass cartilaginous. These are the most ancient bony fish in origin, with some features resembling sharks. Their axial skeleton is represented by a notochord, which persists for life. The vertebral bodies are undeveloped, but their cartilaginous arches are laid. But sturgeons have gill covers, a swim bladder, and bony parts of the skeleton. Modern cartilaginous fish are benthic forms. These include sterlet, sturgeon, stellate sturgeon, beluga, kaluga. In contrast to cartilaginous fish, they form overhead bones of the skull, bony gill covers, and the bony base of the skull; outside along the body there are three or five rows of large bony plaques and small bony grains between them. Sturgeons feed on animal food, most often invertebrates. Food is collected using the rostrum, digging at the bottom. Large sturgeon (beluga and kaluga) can feed on fish and sometimes young seals. Beluga lives in the waters of the Volga-Caspian basin sometimes up to 100 years and reaches a mass of up to 1,000 kg. The Far Eastern kaluga - "Queen of the Amur" - is not inferior to it in size.

A typical representative of sturgeon is the Russian sturgeon, an inhabitant of the Volga-Caspian and Black Sea basins. It is an anadromous fish that lives in the sea, but goes into rivers for spawning. The sturgeon has no teeth, and it gropes for food with its antennae, and then pulls out its mouth (rostrum) and draws it into the pharynx. It feeds on shellfish. In winter, it lies in deep holes, most often in the mouth of the river. In spring it goes against the current to the rivers for spawning. Caviar develops in the bottom layer of water. Juveniles slide down the rivers into the seas, where they live until maturity.

The sterlet, unlike other sturgeons, spends its entire life in fresh water. She is the smallest of them. It feeds on insects. Its weight reaches 3-6 kg.

Sturgeons are of great commercial importance. Meat, caviar (black) and even chord are used for food. But due to overfishing and a number of changes in the environment, the number of sturgeon fish has significantly decreased. Therefore, fishing on them has decreased. Some species - sterlet, sturgeon, Black Sea beluga - are listed in the Red Book.

The herring detachment. Representatives of the herring order have a flat silvery body, a very short lateral line, or it is completely absent. The head of the herring is not covered with scales, the fins are soft. The swim bladder is constantly connected to the intestines.

Most herring live in the water column and feed on plankton. About 300 species of these valuable commercial fish are known. The most common are Atlantic and Pacific herring. Their body length is 40-50 cm. The Atlantic herring that lives in the Baltic Sea is called herring. The Black Sea herring lives in the Black Sea (body length up to 40 cm, weight up to 1 kg). Part of the individuals leaving for spawning in the river. Danube is called Danube herring. The Black Sea sprat, tulka and others are found in the Black Sea. Anchovy fish belong to herring: European anchovy, or anchovy, which are of great commercial value.

Squad salmon. Their body is rounded or slightly compressed from the sides. A characteristic feature is the presence of an adipose fin located on the dorsal side in front of the caudal fin.

Most salmonids are anadromous fish (salmon), but some species constantly live in fresh water bodies (trout, whitefish, omul, etc.). Many salmonids are widespread in the Far East, for example chum salmon, pink salmon, sockeye salmon, chinook salmon, etc. During spawning, they migrate over a distance of several thousand kilometers (chum salmon - 1,000 km, chinook salmon - 4,000 km). In the reservoirs of the CIS countries, salmon species such as European grayling, trout, Danube and Black Sea salmon are found. Trout lives in mountain rivers, it is artificially bred in Transcarpathia, Crimea.

Salmon are commercial fish, highly valued for their high quality meat ("red fish") and red caviar.

Detachment carp. The order carp has about 3000 species, most of which live in fresh water. Some of them go to spawn in the sea (roach, ram). They have soft fins, a swim bladder like herring. There are no teeth, but there are pharyngeal teeth that serve to grind food.

The best known is the domestic carp, the ancestor of which is the freshwater carp. Carp have been artificially bred for a long time. Breeders have bred various breeds of carp: mirror, Ukrainian, etc. Carp can weigh up to 20 kg, length 1 m. It is grown in fish farms to a marketable weight of 500-2000 g in 2-3 years. Carp becomes sexually mature in 3-5 years. Very fertile: lays 600,000 800,000 eggs. Of the carp in our water bodies there are: crucian carp, tench, bream, roach, grass carp, silver carp, blue bream, silver bream, sabrefish, etc. Carp are excellent objects of fishing and sport fishing.

Squad of perch. The perch order - about 6500 species. A characteristic feature is that their swim bladder loses its connection with the intestines and exists on its own. Fins with spines. The body length is from 1 cm to 5 m, and the weight reaches 500 kg. For example, a swordfish is 4 m long and 300 kg in weight. She, chasing prey, can reach speeds of up to 120 km per hour. Perch include tuna (up to 3 m long and 680 kg in weight), horse mackerel, gobies.

In the Black Sea there are: common mackerel, common horse mackerel, common tuna, gobies. In the fresh water bodies of the country, commercial species such as river perch and pike perch are widespread. A number of representatives of percidae - common goby, golden goby, striped ruff - are listed in the Red Book.

Bony fish are of great practical importance for humans. Millions of people are engaged in fishing, breeding and processing fish, building boats and making fishing equipment. In some countries, the population feeds mainly on fish, and its well-being depends mainly on the size of the catch. Hundreds of thousands of people are fond of fishing and spearfishing, and this wonderful sport gives them health and relaxation. There are even more aquarists creating a colorful, quiet world in the glass containers of their aquariums. In addition to food, fish are used as raw materials for medicine (fish oil), feed for livestock and poultry (feed meal), fertilizer for fields (fertilizer), technical fat, glue, leather and other products used in the food and light industry.

Representatives detachment sturgeon belong to the subclass cartilage. These are the most ancient bony fish in origin, with some features resembling sharks. Their axial skeleton is represented by a notochord, which persists for life. The vertebral bodies are undeveloped, but their cartilaginous arches are laid. But sturgeons have gill covers, a swim bladder, and bony parts of the skeleton. Modern cartilaginous fish are benthic forms. These include sterlet, sturgeon, stellate sturgeon, beluga, kaluga... In contrast to cartilaginous fish, they form false bones of the skull, bony gill covers, bony base of the skull, outside along the body there are three or five rows of large bony plaques and small bony grains between them. Sturgeons feed on animal food, most often invertebrates. Food is collected using the rostrum, digging at the bottom. Large sturgeon ( beluga and kaluga) can feed on fish and sometimes juvenile seals. Beluga lives in the waters of the Volga-Caspian basin sometimes up to 100 years and reaches a mass of up to 1,000 kg. In terms of size, it is not inferior to the Far Eastern kaluga- "Queen of Cupid".

A typical representative of sturgeon - Russian sturgeon, inhabitant of the Volga-Caspian and Black Sea basins. It is an anadromous fish that lives in the sea, but goes into rivers for spawning. The sturgeon has no teeth, and it gropes for food with its antennae, and then pulls out its mouth (rostrum) and draws it into the pharynx. It feeds on shellfish. In winter, it lies in deep holes, most often in the mouth of the river. In spring, it goes against the current to the rivers for spawning. Caviar develops in the bottom layer of water. Juveniles slide down the rivers into the seas, where they live until maturity.

Sterlet, unlike other sturgeon, spends all its life in fresh water. She is the smallest of them. It feeds on insects. Its weight reaches 3-6 kg.

Squad herring

Representatives detachment of herring have a flat silvery body, a very short lateral line, or it is completely absent. The head of the herring is not covered with scales, the fins are soft. The swim bladder is constantly connected to the intestines.

Most herring live in the water column and feed on plankton. About 300 species of these valuable commercial fish are known. Most common atlantic and pacific herring... Their body length is 40-50 cm. Atlantic herring living in the Baltic Sea is called herring... Lives in the Black Sea black sea herring(body length up to 40 cm, weight up to 1 kg). Part of the individuals leaving for spawning in the river. Danube is called Danube herring. In the Black Sea meets black sea sprat, tulle and others. Herrings include anchovy fish: European anchovy, or anchovy of great commercial value.

Salmon squad

Their body is rounded or slightly compressed from the sides. A characteristic feature is the presence of an adipose fin located on the dorsal side in front of the caudal fin.

Most salmonids are anadromous fish ( salmon), but some species constantly live in fresh water bodies ( trout, whitefish, omul and etc.). Many salmonids are common in the Far East, for example chum, pink salmon, red salmon, chinook salmon etc. During spawning, they migrate over a distance of several thousand kilometers (chum salmon - 1,000 km, chinook salmon - 4,000 km). In the reservoirs of the CIS countries there are salmon such as European grayling, trout, Danube and Black Sea salmon. Trout lives in mountain rivers, it is artificially bred in Transcarpathia, Crimea.

Salmon are commercial fish, highly valued for their high quality meat ("red fish") and red caviar.

Detachment carp

Detachment carp has about 3,000 species, most of which live in fresh water. Some of them go to spawn in the seas ( vobla, ram). They have soft fins, a swim bladder like herring. There are no teeth, but there are pharyngeal teeth that serve to grind food.

Most famous home carp whose ancestor is carp living in fresh water. Carp have been artificially bred for a long time. Breeders have bred various breeds of carp: mirror, Ukrainian, etc. Carp can weigh up to 20 kg, length 1 m. It is grown in fish farms to marketable weight of 500-2000 g in 2-3 years. Carp becomes sexually mature in 3-5 years. Very fertile: lays 600,000-800,000 eggs. Of the cyprinids in our reservoirs are found: crucian carp, tench, bream, roach, White amur, fathead, blue bream, silver bream, sabrefish and etc. Carp are excellent objects of fishing and sport fishing.

Perch squad

Perch squad- about 6,500 species. A characteristic feature is that their swim bladder loses its connection with the intestines and exists on its own. Fins with spines. The body length is from 1 cm to 5 m, and the weight reaches 500 kg. For example, swordfish- length 4 m, weight 300 kg. She, chasing prey, can reach speeds of up to 120 km per hour. Perch include tuna(up to 3 m long and 680 kg in weight), horse mackerel, bulls.

In the Black Sea there are: common mackerel, common horse mackerel, common tuna, bulls... In fresh water bodies of the country, such commercial species are widespread as river perch, zander. A number of representatives of percidae - common goby, golden goby, striped ruff - are listed in the Red Book.

Subclass cross-finned

Subclass cross-finned is an ancient and almost completely extinct branch of vertebrates that lived in shallow fresh water bodies. Currently, only one species of living cross-fin is known - coelacanth, or cellocant... The discovery of this fish in 1938 caused a real sensation in the scientific world, since at that time it was believed that the cross-finned were extinct. Since then, several specimens of these fish have been caught off the eastern coast of South Africa (1952). When studying them, it turned out that due to the migration of the wild ancestors of coelacanth to the ocean and the revitalization of the bottom spaces by them, some of the details of the respiratory apparatus disappeared: there are no through nostrils, the lung is filled with fat. However, paired fins, as organs of movement on the ground, fully retained the structural features characteristic of the ancient cross-finned. Coelacanth- a predator living at a depth of 400-1,000 m, its length is up to 180 cm, its weight is up to 90 kg. It is of great importance for the study of the origin of terrestrial vertebrates.

Subclass lungs

Subclass lungs- This is a small group of fish, combining features of a primitive organization with features of specialization and adaptation to life in oxygen-depleted water bodies. A representative of lungs - neoceratode- the largest living fish of this group (length up to 175 cm). Along with the gills, the neoceratode also has an organ for breathing with atmospheric air - the pulmonary sac. This fish lives in the rivers of Eastern Australia. In summer, when reservoirs become shallow and depleted in oxygen, it breathes mainly with the lungs, often rises to the surface and swallows air. Spending life in non-drying water bodies, the neoceratode does not hibernate. In contrast, another representative of lungs, which is widespread in the fresh waters of Africa, is protopterus- when the reservoir dries up, it buries itself in silt and goes into hibernation, which lasts about 5 months. At this time, he breathes only with a pair of lungs.

Bony fish (Osteichthyes) branched off from the common fish trunk extremely early. Their fossil remains are found almost simultaneously with the remains of ancient cartilaginous fish already in freshwater deposits of the Devonian. Bony fish are characterized by the following progressive structural features that give them an advantage over the ancient cartilaginous fish.

Their lighter and stronger bony skeleton gave them an advantage in movement, as did the important new organ, the swim bladder. They have developed a gill cover and a better breathing method. Primary bony fishes (Osteichthyes? 5) split into two groups already in the Devonian.

One group - ray-finned, or ray-finned (Actinopterygii), evolved towards adaptation to life in open reservoirs and was the ancestor of higher bony fish; cartilaginous ganoids, or sturgeon (Chondrostei), paleoniscides (Palaeoniscoidea), bony ganoids (Holstei) and bony fishes (Teleostei). They are characterized by the presence of a dorsal swim bladder, which serves as an important adaptation for swimming, highly developed organs of vision, and the cerebellum of the brain. The most perfect in this respect, the youngest group of teleost fishes (Teleostei) appeared only at the end of the Triassic and very quickly reached complete dominance in all water bodies of the world, both marine and freshwater (out of 20 thousand species of all fish, about 19.5 thousand belong to bony fish).

Another group of the most ancient bony fish inhabited coastal zones of freshwater reservoirs and was characterized by adaptation to life in coastal thickets; their fins are adapted to support the body at the bottom, there is a heavy scaly cover of complex ganoid or cosmoid scales, the organs of vision and the cerebellum are poorly developed, in addition to the gills, they have developed abdominal swim bladders as additional respiratory organs. The presence of choanas was found in the skull, indicating the presence of pulmonary respiration; therefore, they are currently combined into a general subclass of choanates (Choanichthyes, or Sarcopterygii).

This group of fish includes Crossopterygii and Dipnoi. Of the cross-finned, one group (Rhipidistia) became extinct in the Permian period, and the other (Coelacantini) in the form of relics has survived to the present time (Latimeria). The lungfish branched off from common ancestors with cross-finned fish back in the Devonian and continue to exist in the form of relics to this day (Ceratodus in Australia, Lepidosiren in America and Protopterus in Africa).

The African mnogoperus, or polypterus (Polypterus), is very close in lifestyle to the cross-finned fish. However, many ichthyologists consider this similarity to be convergent and, by the presence of ganoid scales in polypterus, consider it a multioperative related to fossil paleoniscides. Together with cartilaginous ganoids, they are referred to the group of ancient ray-finned fish (Paleopterygii). Recently, mnogoperovykh have been distinguished into an independent subclass of Brachiopterygii.

According to paleontological data, the ancient group of cross-fins (Rhipidistia) was the ancestor of the ancestors of terrestrial vertebrates, and the branch of the primary tetrapods (Quadrupeda) is diverted from this group of fish in the Devonian period. They had fleshy fins, adapted to crawling along the bottom, and a skull structure very similar to the skull of the oldest fossil amphibians - Stegocephals.