Location of paired and unpaired fins in guppies. Organs of movement - fins

TOPIC 1.

Rib fins. Organi dikhannya, dawn that hearing.

FISH FINNERS

Fins are a characteristic feature of the structure of fish. They are subdivided into paired, corresponding to the limbs of higher vertebrates, and unpaired, or vertical.

Paired fins include the pectoral and pelvic fins. Unpaired consist of dorsal (one to three), caudal and anal (one or two). Salmonids, grayling and other fish have an adipose fin on their backs, while mackerel, tuna, and saury have small accessory fins behind the dorsal and anal fins. The position of the fins on the body, their shape, size, structure and function are very diverse. Fish use their fins for movement, maneuvering and balance. In moving forward, the caudal fin plays the main role in most fish. It does the work of the most advanced swing-out propeller and stabilizes motion. The dorsal and anal fins are a kind of keels for giving the body of the fish the desired stable position.

Two sets of paired fins serve for balance, braking and steering.

The pectoral fins are usually located behind the branchial openings. The shape of the pectoral fins is related to the shape of the tail: they are rounded in fish that have a rounded tail. Good swimmers have pointed pectoral fins. The pectoral fins are especially strongly developed in flying fish. Due to the high speed of movement and blows of the tail fin, flying fish jump out of the water and soar on the pterygoid pectoral fins, covering a distance of up to 100-150 m through the air. Such flights help them escape from the pursuit of predators.

The pectoral fins of the monkfish have a segmented fleshy base. Leaning on them, the anglerfish moves along the bottom in jumps, as if on legs.

The location of the pelvic fins varies from fish to fish. In low-organized (sharks, herring, carp), they are on the belly. In the more highly organized, the pelvic fins move forward, taking a position under the pectorals (perch, mackerel, mullet). In codfish, the pelvic fins are in front of the pectorals.

In gobies, the pelvic fins are fused into a funnel-shaped suction cup.

In an even more surprising adaptation, the pelvic fins of the Pinagor have changed. Their suction cup holds the fish so firmly that it is difficult to tear it off the stone.

Of the unpaired fins, the caudal fins deserve special attention, the complete absence of which is very rare (stingrays). According to the shape and location relative to the end of the spine, several types of caudal fins are distinguished: asymmetric (heterocercal) - in sharks, sturgeons, etc .; false symmetric (homocercal) - in most teleost fish.

The shape of the caudal fin is closely related to the fish's lifestyle6 and especially to the ability to swim. Good swimmers are fish with crescent, pitchfork, and grooved tails. Less mobile fish have a truncated, rounded tail fin. In sailing ships, it is very large (up to 1.5 m long), they use it as a sail, setting it above the surface of the water. In spiny-finned fish, the rays of the dorsal fin are strong spines, often equipped with poisonous glands.

A peculiar transformation is observed in adherent fish. Her dorsal fin moves to her head and turns into a suction disc, with the help of which she attaches to sharks, whales, ships. In anglers, the dorsal fin is displaced to the snout and pulled out into a long thread that serves as a bait for prey.

All fins in fish are subdivided into paired ones, which correspond to the limbs of higher vertebrates, as well as unpaired ones. Paired fins include pectoral (P - pinna pectoralis) and abdominal (V - pinna ventralis). Unpaired fins include dorsal (D - p. Dorsalis); anal (A - p. analis) and tail (C - p. caudalis).

A number of fishes (salmonids, haracins, killer whales, etc.) have an adipose fin behind the dorsal fin; it is devoid of fin rays (p.adiposa).

Pectoral fins are common in bony fish, while in moray eels and some others, they are absent. Lampreys and myxines are completely devoid of pectoral and pelvic fins. In skates, the pectoral fins are greatly enlarged and play the main role as their organs of movement. The pectoral fins are especially strongly developed in flying fish. The three rays of the pectoral fin in the sea rooster act as legs when crawling on the ground.

The pelvic fins can be in different positions. Abdominal position - they are located approximately in the middle of the abdomen (sharks, herring-like, carp-like) When thoracic, they are displaced towards the front of the body (perch-like). Jugular position, fins are located in front of the pectorals and on the throat (cod).

In some fish, the pelvic fins are transformed into thorns (stickleback) or into a sucker (pinegora). In male sharks and rays, the posterior rays of the pelvic fins have evolved into copulatory organs. They are completely absent in eels, catfish, etc.

There may be a different number of dorsal fins. In herring and carp, it is one, in mullet and perch - two, in cod - three. Their location can be different. In pike, it is shifted far back, in herring, carp - in the middle of the body, in perch and cod - closer to the head. The longest and highest dorsal fin in the sailfish fish. In the flounder, it looks like a long ribbon running along the entire back and, simultaneously with almost the same anal fin, is their main organ of movement. Mackerel, tuna and saury have small accessory fins behind the dorsal and anal fins.

Individual rays of the dorsal fin sometimes stretch into long filaments, while in the anglerfish the first ray of the dorsal fin is shifted to the snout and transformed into a kind of fishing rod, like in the deep-sea anglerfish. The first dorsal fin of the adherent fish also shifted to the head and turned into a real sucker. The dorsal fin in sedentary benthic fish species is poorly developed (catfish) or absent (stingrays, electric eel).

Caudal fin:
1) isobathic — the upper and lower lobes are the same (tuna, mackerel);
2) hypobatic — the lower lobe is lengthened (flying fish);
3) epibatous — the upper lobe is lengthened (sharks, sturgeons).

Types of caudal fins: forked (herring), notched (salmon), truncated (cod), rounded (burbot, gobies), crescent (tuna, mackerel), pointed (eelpout).

From the very beginning, the fins were assigned the function of movement and balance, but sometimes they also perform other functions. The main fins are the dorsal, caudal, anal, two ventral and two pectoral fins. They are subdivided into unpaired - dorsal, anal and caudal, and paired - pectoral and abdominal. Some species also have an adipose fin located between the dorsal and caudal fins. All fins are driven by muscles. In many species, the fins are often modified. Thus, in males of viviparous fish, the modified anal fin has become a mating organ; some species have well-developed pectoral fins that allow the fish to jump out of the water. Gourami have special tentacles, which are filamentous pelvic fins. And in some species that burrow into the ground, fins are often absent. Guppy tail fins are also an interesting creation of nature (there are about 15 species of them and their number is growing all the time). The tail and tail fin begin the movement of the fish, which send the body of the fish forward with a strong blow. The dorsal and anal fins ensure a balanced body position. The pectoral fins move the body of the fish during slow swimming, serve as a rudder and, together with the pelvic and caudal fins, provide a balanced position of the body when it is immovable. In addition, some species of fish can rely on pectoral fins or move with their help on hard surfaces. The pelvic fins perform mainly the function of balance, but in some species they are changed into a suction disc, which allows the fish to stick to a hard surface.

1. Dorsal fin.

2. Adipose fin.

3. Caudal fin.

4. Pectoral fin.

5. Pelvic fin.

6. Anal fin.

The structure of the fish. Caudal fin types:

Truncated

Split

Lyre-shaped

24. The structure of the skin of fish. The structure of the main types of fish scales, its functions.

Fish skin has a number of important functions. Located on the border of the external and internal environment of the body, it protects the fish from external influences. At the same time, by separating the fish organism from the surrounding liquid medium with chemicals dissolved in it, the fish skin is an effective homeostatic mechanism.

Fish skin regenerates quickly. Through the skin, on the one hand, a partial release of the final metabolic products occurs, and on the other hand, the absorption of certain substances from the external environment (oxygen, carbonic acid, water, sulfur, phosphorus, calcium and other elements that play an important role in life). The skin plays an important role as a receptor surface: thermo-, barochemo- and other receptors are located in it. In the thickness of the corium, the integumentary bones of the skull and the girdle of the pectoral fins are formed.

In fish, the skin also performs a rather specific - supporting - function. On the inner side of the skin, the muscle fibers of the skeletal muscles are fixed. Thus, it acts as a supporting element in the musculoskeletal system.

Fish skin consists of two layers: the outer layer of epithelial cells, or epidermis, and the inner layer of connective tissue cells - the skin itself, dermis, corium, cutis. A basement membrane is distinguished between them. The skin is underlain by a loose connective tissue layer (subcutaneous connective tissue, subcutaneous tissue). In many fish, fat is deposited in the subcutaneous tissue.

The epidermis of fish skin is represented by a stratified epithelium, consisting of 2–15 rows of cells. The cells of the upper layer of the epidermis are flat. The lower (germ) layer is represented by one row of cylindrical cells, which, in turn, originate from the prismatic cells of the basement membrane. The middle layer of the epidermis consists of several rows of cells, the shape of which varies from cylindrical to flat.

The outermost layer of epithelial cells is keratinized, but unlike terrestrial vertebrates in fish, it does not die off, maintaining a connection with living cells. During the life of a fish, the intensity of keratinization of the epidermis does not remain unchanged, it reaches the greatest extent in some fish before spawning: for example, in male cyprinids and whitefishes in some places of the body (especially on the head, gill covers, sides, etc.), the so-called pearl rash - a mass of small white bumps that give the skin a roughness. After spawning, it disappears.

The dermis (cutis) consists of three layers: a thin upper (connective tissue) layer, a thick middle reticular layer of collagen and elastin fibers, and a thin basal layer of tall prismatic cells, giving rise to two upper layers.

In active pelagic fish, the dermis is well developed. Its thickness in areas of the body that provide intensive movement (for example, on the tail stem of a shark) is greatly increased. The middle layer of the dermis in active swimmers can be represented by several rows of strong collagen fibers, which are also connected with each other by transverse fibers.

In slow-swimming littoral and bottom fish, the dermis is loose or generally underdeveloped. In fast-swimming fish, the subcutaneous tissue is absent in the areas of the body that provide swimming (for example, the caudal peduncle). In these places, muscle fibers are attached to the dermis. In other fish (most often slow ones), the subcutaneous tissue is well developed.

The structure of fish scales:

Plakoid (it is very ancient);

Ganoid;

Cycloid;

Ctenoid (youngest).

Plakoid fish scales

Plakoid fish scales(photo above) is typical for modern and fossil cartilaginous fish - and these are sharks and rays. Each such scale has a plate and a thorn sitting on it, the tip of which goes out through the epidermis. In this scale, dentin is the basis. The spike itself is covered with even harder enamel. The plakoid scale has a cavity inside, which is filled with pulp - pulp; it has blood vessels and nerve endings.

Ganoid Fish Scale

Ganoid Fish Scale looks like a rhombic plate and the scales are connected to each other, forming a dense shell on the fish. Each of these scales consists of a very hard substance - the upper part is ganoin, and the lower part is bone. This type of scale has a large number of fossil fish, as well as the upper parts in the caudal fin in modern sturgeon fish.

Cycloid fish scales

Cycloid fish scales occurs in teleost fish and lacks a layer of ganoin.

Cycloid scales have a rounded neck with a smooth surface.

Ctenoid fish scales

Ctenoid fish scales also found in bony fish and does not have a layer of ganoin, on the back it has spines. Typically, the scales in these fish are tiled, and each scale is covered in front and on both sides with the same scales. It turns out that the rear end of the scale goes out, but it is also covered with another scale from below, and this type of cover retains the flexibility and mobility of the fish. The annual rings on the fish scales allow you to determine its age.

The arrangement of scales on the body of the fish goes in rows and the number of rows and the number of scales in the longitudinal row does not change with the age of the fish, which is an important systematic feature for different species. Take this example - the side line of the goldfish has 32-36 scales, while the pike has 111-148.

Fins. Their sizes, shape, quantity, position and function are different. The fins help maintain body balance and participate in movement.

Rice. 1 Fins

Fins are subdivided into paired, corresponding to the limbs of higher vertebrates, and unpaired (Fig. 1).

TO paired relate:

1) chest P ( pinna pectoralis);

2) abdominal V. ( R. ventralis).

TO unpaired:

1) dorsal D ( p. dorsalis);

2) anal A (R. analis);

3) tail C ( R. caudalis).

4) fatty ap (( p.adiposa).

In salmonids, haracins, killer whales, etc., behind the dorsal fin there is adipose fin(Fig. 2), devoid of fin rays ( p.adiposa).

Rice. 2 Adipose fin

Pectoral fins common in bony fish. In skates, the pectoral fins are enlarged and are the main organs of movement.

Pelvic fins occupy a different position in fish, which is associated with a shift in the center of gravity caused by a contraction of the abdominal cavity and the concentration of the viscera in the front of the body.

Abdominal position- the pelvic fins are in the middle of the abdomen (sharks, herring-like, carp-like) (Fig. 3).

Rice. 3 Abdominal position

Thoracic position- the pelvic fins are displaced to the anterior part of the body (perch-shaped) (Fig. 4).

Rice. 4 Thoracic position

Jugular position- the pelvic fins are located in front of the pectorals and on the throat (cod) (Fig. 5).

Rice. 5 Jugular position

Dorsal fins there can be one (herring-like, carp-like), two (mullet-like, perch-like) or three (cod-like). Their location is different. In pike, the dorsal fin is displaced back, in herring, carp, it is located in the middle of the body, in fish with a massive front part of the body (perch, cod) one of them is located closer to the head.

Anal fin usually there is one, the cod has two, the barbed shark does not.

Tail fin differs in a varied structure.

Depending on the size of the upper and lower blades, there are:

1)isobathic type - in the fin, the upper and lower lobes are the same (tuna, mackerel);

Rice. 6 Isobate type

2)hypobatic type - the lower blade is lengthened (flying fish);

Rice. 7 Hypobatic type

3)epibate type - the upper blade is lengthened (sharks, sturgeons).

Rice. 8. Epibate type

According to the shape and location relative to the end of the spine, several types are distinguished:

1) Protocercal type - in the form of a fin border (lamprey) (Fig. 9).

Rice. 9 Protocercal type -

2) Heterocercal type - asymmetrical, when the end of the spine goes into the upper, most elongated lobe of the fin (sharks, sturgeons) (Fig. 10).

Rice. 10 Heterocercal type;

3) Homocercal type - outwardly symmetric, while the modified body of the last vertebra enters the upper lobe (bony) (

Rice. 11 Homocercal type

The fin rays serve as a support for the fins. In fish, branched and unbranched rays are distinguished (Fig. 12).

Unbranched fin rays may be:

1)articulated (able to bend);

2)unsegmented hard (thorny), which in turn are smooth and serrated.

Rice. 12 Types of fin rays

The number of rays in the fins, especially in the dorsal and anal fins, is a specific feature.

The number of thorny rays is denoted by Roman numerals, branchy ones - by Arabic numerals. For example, the dorsal fin formula for river bass is:

DXIII-XVII, I-III 12-16.

This means that the perch has two dorsal fins, of which the first consists of 13 - 17 spiny rays, the second of 2 - 3 spiny and 12-16 branched rays.

Functions of the fins

· Tail fin creates a driving force, provides high maneuverability of the fish when turning, acts as a rudder.

· Thoracic and abdominal (paired fins ) maintain balance and are rudders when cornering and at depth.

· Dorsal and anal the fins act as a keel, preventing the body from rotating around its axis.

Habitats and external structure of fish

The habitat of fish is various reservoirs of our planet: oceans, seas, rivers, lakes, ponds. It is very vast: the area occupied by the oceans exceeds 70% of the Earth's surface, and the deepest depressions go into the depths of the oceans by 11 thousand meters.

The variety of living conditions in water influenced the appearance of fish and contributed to a wide variety of forms of their body: the emergence of many adaptations to living conditions both in structure and in biological features.

General plan of the external structure of fish

On the head of the fish are the eyes, nostrils, mouth with lips, gill covers. The head merges smoothly into the body. The body extends from the operculums to the anal fin. The body of the fish ends with a tail.

The outside of the body is covered with skin. Protects the skin of most fish covered with mucus scales .

The organs of movement of fish are fins ... Fins are outgrowths of skin supported by bone fin rays ... The caudal fin is of the greatest importance. Paired fins are located below the sides of the body: pectoral and abdominal fins. They correspond to the fore and hind limbs of terrestrial vertebrates. The position of paired fins varies in different fish. Above the body of the fish is the dorsal fin, below, closer to the tail - the anal. The number of dorsal and anal fins varies.

On the sides of the body of most fish there is a kind of organ that perceives the flow of water. This lateral line ... Thanks to the lateral line, even a blinded fish does not bump into obstacles and is able to catch moving prey. The visible part of the lateral line is formed by scales with holes. Through them, water enters the channel that runs along the body, to which the endings of the nerve cells fit. The side line may be dashed, solid, or completely absent.

Functions of the fins

Thanks to the fins, the fish is able to move and maintain balance in the aquatic environment. Deprived of fins, it turns belly up, since the center of gravity is placed in the dorsal part.

Unpaired fins (dorsal and anal) provide stability to the body. The caudal fin in the overwhelming majority of fish functions as a mover.

Paired fins (thoracic and abdominal) serve as stabilizers, i.e. provide an equilibrium position of the body when it is motionless. With their help, the fish maintains the body in the desired position. When driving, they serve as load-bearing planes, a steering wheel. The pectoral fins move the body of the fish during slow swimming. The pelvic fins mainly perform the function of balance.

Fish have a streamlined body shape. It reflects the characteristics of the habitat and lifestyle. In fish adapted to fast long swimming in the water column ( tuna(2) mackerel, herring, cod, salmon ), "Torpedo" shape of the body. For predators who practice quick throws at a short distance ( pike, taimen, barracuda, garfish (1) , saury), it is "arrow-shaped". Some fish adapted to long-term occurrence on the bottom ( slope (6) , flounder (3) ) have a flat body. In some species, the body has a bizarre shape. For instance, sea ​​Horse resembles a corresponding chess piece: its head is at right angles to the axis of the body.

Sea Horses inhabit different oceans of the globe. These fish surprise everyone who observes them: the body, like an insect, is enclosed in a shell, a prehensile monkey's tail, rotating chameleon's eyes and, finally, a bag, like a kangaroo.

Although this cute fish can swim upright with the swinging motion of the dorsal fin, it is a poor swimmer and hangs most of the time, clinging to algae with its tail and looking out for small prey. The tubular snout of the ridge acts like a pipette - when the cheeks swell sharply, prey is quickly drawn into the mouth from a distance of up to 4 cm.

The smallest fish is considered filipino goby pandaku ... Its length is about 7 mm. At one time, women of fashion wore these fish in ... ears. In crystal earrings-aquariums!

The largest fish is considered whale shark, which reaches a length of 15 m.

Additional fish organs

In some species of fish (for example, carp or catfish), antennae are located around the mouth. These are additional organs of touch and determination of the taste of food. Many deep sea fish (e.g. deep-sea angler, hatchet fish, anchovy, photoblepharon ) developed luminous organs.

There are protective spikes on the fish scales. They can be located in different parts of the body. For example, thorns cover the body hedgehog fish .

Some fish, for example scorpionfish, sea dragon, wart have defense and attack organs - poisonous glands located at the base of spines and fin rays.

Body covers

Outside, the fish skin is covered with scales - thin translucent plates. Scales with their ends overlap each other, arranged in tiles. This ensures

strong protection of the body and at the same time does not create obstacles to movement. The scales are formed by special skin cells. The size of the scales is different: from microscopic to eels up to several centimeters at Indian barbel ... There is a wide variety of scales: in shape, strength, composition, quantity and some other characteristics.

In the skin lie pigment cells - chromatophores : when they expand, the pigment grains spread over a larger space and the body color becomes bright. If the chromatophores contract, the pigment grains accumulate in the center, leaving most of the cell unstained, and the body color fades. If the pigment grains of all colors are evenly distributed inside the chromatophores, the fish has a bright color; if pigment grains are collected in the centers of cells, the fish becomes almost colorless, transparent; if only the yellow pigment grains are distributed over their chromatophores, the fish changes color to light yellow.

Chromatophores determine all the variety of fish coloration, especially bright in the tropics. Thus, the skin of the fish serves as an external protection. It protects the body from mechanical damage, facilitates sliding, determines the color of the fish, and communicates with the external environment. The skin contains organs that sense the temperature and chemical composition of water.

Color value

Pelagic fish often have a dark "back" and a light "belly", like this fish abadejo family of cod.

Indian glass catfish can serve as a guide to the study of anatomy.

Many fish living in the upper and middle layers of the water have a darker color of the upper body and a lighter color of the lower one. The silvery belly of the fish, if you look at the fish from below, will not stand out against the light background of the sky. Likewise, the dark back, when viewed from above, will blend in with the dark background of the bottom.

Studying the color of fish, one can see how with its help disguise and imitation of other types of organisms occur, observe the demonstration of danger and inedibility, as well as the submission of other signals by fish.

In some periods of life, many fish acquire a bright breeding coloration. Often the color and shape of the fish complement each other.

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The hydrosphere is characterized by an extraordinary variety of conditions. These are fresh, flowing and stagnant waters, as well as salty seas and oceans inhabited by organisms at different depths. For existence in such diverse conditions, fish have developed both general principles of structure that meet the requirements of the environment (smooth, elongated body without protrusions, covered with mucus and scales; pointed head with pressed gill covers; fin system; lateral line), and adaptations inherent in individual groups (flattened body, light organs, etc.). Each type of fish has numerous and varied adaptations corresponding to a certain lifestyle.

External structure of fish

Fish and fish-like organisms have a body divided into three sections: head, torso and tail.

Head ends in bony fish (A) at the level of the posterior edge of the operculum, in cyclostomes (B) - at the level of the first branchial foramen. Torso(usually called the body) in all fish ends at the level of the anus. Tail consists of a caudal peduncle and a caudal fin.

Fish have paired and unpaired fins... TO paired fins include the pectoral and pelvic fins, to unpaired- caudal, dorsal (one to three), one or two anal fins and an adipose fin located behind the dorsal (salmon, whitefish). In gobies (B), the pelvic fins have changed into a kind of suckers.

Body shape in fish it is associated with habitat conditions. Fish living in the water column (salmon) are, as a rule, torpedo-shaped or arrow-shaped. Bottom fish (flounder) most often have a flattened or even completely flat body shape. The species that live among aquatic plants, stones and driftwood have a body that is strongly compressed from the sides (bream) or serpentine (eel), which provides them with better maneuverability.

Body fish can be naked, covered with mucus, scales or shell (needle-fish).

Scales freshwater fish of Central Russia can be of 2 types: cycloid(with a smooth trailing edge) and ctenoid(with spines along the posterior margin). There are various modifications of scales and protective bone formations on the body of fish, in particular, sturgeon beetles.

The scales on the body of fish can be arranged in different ways (solid cover or areas, like in a mirror carp), and also be different in shape and size.

Position of the mouth- an important feature for identifying fish. Fish are divided into species with lower, upper and final positions of the mouth; there are also intermediate options.

For fish of near-surface waters, the upper position of the mouth is characteristic (chekhon, verkhovka), which allows them to pick up prey that has fallen to the surface of the water.
For predator species and other inhabitants of the water column, the final position of the mouth (salmon, perch) is characteristic,
and for the inhabitants of the bottom zone and the bottom of the reservoir - the lower one (sturgeon, bream).
In cyclostomes, the mouth funnel, armed with horny teeth, performs the function of the mouth.

The mouth and mouth cavity of carnivorous fish are equipped with teeth (see below). Peaceful benthivorous fish have no teeth on their jaws, but they have pharyngeal teeth for grinding food.

Fins- formations, consisting of hard and soft rays, connected by a membrane or free. The fins of fish are composed of spiny (hard) and branched (soft) rays. Spiky rays can be in the form of powerful thorns (catfish) or serrated saws (carp).

According to the presence and nature of rays in the fins of most bony fish, fin formula, which is widely used in their description and definition. In this formula, the abbreviated designation of the fin is given in Latin letters: A - anal fin (from Latin pinna analis), P - pectoral fin (pinna pectoralis), V - pelvic fin (pinna ventralis) and D1, D2 - dorsal fins (pinna dorsalis). Roman numerals give the numbers of thorny rays, and Arabic numerals - soft rays.

Gills absorb oxygen from water and release carbon dioxide, ammonia, urea and other waste products into the water. Teleost fish have four branchial arches on each side.

Gill stamens the thinnest, longest and most numerous in fish that feed on plankton. In predators, the gill rakers are sparse and sharp. The number of stamens is counted on the first arch located immediately under the operculum.

Pharyngeal teeth located on the pharyngeal bones, behind the fourth branchial arch.