FRS Rubtsovsk Guster. Biology at the Lyceum Unpaired fins of fish

; their organs that regulate movement and position in water, and in some ( flying fish) - also planning in the air.

The fins are cartilaginous or bony rays (radials) with skin-epidermal coverings on top.

The main types of fish fins are dorsal, anal, caudal, pair of abdominal and pair of pectoral.
Some fish also have adipose fins(they lack fin rays), located between the dorsal and caudal fins.
The fins are driven by muscles.

Often different types fish fins are modified, for example, males viviparous fish use the anal fin as an organ for mating (the main function of the anal fin is similar to the function of the dorsal fin - it is a keel when the fish moves); at gourami modified thread-like pelvic fins are special tentacles; highly developed pectoral fins allow some fish to jump out of the water.

The fins of fish actively participate in movement, balancing the body of the fish in the water. In this case, the motor moment begins from the caudal fin, which pushes forward with a sharp movement. The tail fin is a kind of propulsion device for the fish. The dorsal and anal fins balance the fish's body in the water.

Different species of fish have different numbers of dorsal fins.
Herring and carp-like have one dorsal fin mullet-like and perch-like- two, y codlike- three.
They can also be located differently: pike- displaced far back herring-like, carp-like- in the middle of the ridge, at perch and cod- closer to the head. U mackerel, tuna and saury there are small additional fins behind the dorsal and anal fins.

The pectoral fins are used by the fish when swimming slowly, and together with the ventral and caudal fins they maintain the balance of the fish’s body in the water. Many bottom fish move along the ground using pectoral fins.
However, in some fish ( moray eels, for example) pectoral and ventral fins are absent. Some species also lack a tail: gymnots, ramfichtidae, seahorses, stingrays, sunfish and other species.

Three-spined stickleback

In general, the more developed a fish's fins are, the more suited it is to swimming in calm water.

In addition to movement in water, air, on the ground; jumping, jumping, fins help different types of fish attach to the substrate (sucker fins in bulls), look for food ( triggles), have protective functions ( sticklebacks).
Some types of fish ( scorpionfish) at the bases of spines dorsal fin have poisonous glands. There are also fish without fins at all: cyclostomes.

TOPIC 1.

Fish fins Organi dikhannya, zora ta rasmu.

FISH FINS

The fins are characteristic feature structure of fish. They are divided into paired, corresponding to the limbs of higher vertebrates, and unpaired, or vertical.

Paired fins include pectoral and ventral fins. Unpaired ones consist of a dorsal (one to three), caudal and anal (one or two). Salmon, grayling and other fish have an adipose fin on their back, and mackerel, tuna, and saury have small additional fins behind the dorsal and anal fins. The position of the fins on the body, their shape, size, structure and functions are very diverse. Fish use fins to move, maneuver and maintain balance. The caudal fin plays the main role in moving forward in most fish. It performs the work of the most advanced propeller with rotating blades and stabilizes the movement. The dorsal and anal fins are a kind of keels for giving the fish’s body the desired stable position.

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

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

The pectoral fins of the monkfish have a segmented, fleshy base. Relying on them, the monkfish moves along the bottom in leaps and bounds, as if on its feet.

Location of the pelvic fins different fish not the same. In lowly organized fish (sharks, herring, carp) they are located on the belly. In more highly organized fish, the ventral fins move forward, occupying a position under the pectoral fins (perch, mackerel, mullet). In cod fish, the pelvic fins are located in front of the pectoral fins.

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

The pelvic fins of the lumpfish have changed into an even more amazing adaptation. Their suction cup holds the fish so firmly that it is difficult to tear it off the stone.

From unpaired fins Special attention deserves a tail, complete absence which is observed very rarely (stingrays). Based on the shape and location relative to the end of the spine, several types of caudal fins are distinguished: asymmetrical (heterocercal) - in sharks, sturgeons, etc.; falsely symmetrical (homocercal) - in most bony fish.

The shape of the caudal fin is closely related to the fish's lifestyle6 and especially to its ability to swim. Good swimmers are fish with lunate, fork-shaped and notched tails. Less mobile fish have a truncated, rounded caudal fin. In sailboats it is very large (up to 1.5 m long), they use it as a sail, placing 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 the sticky fish. Its dorsal fin moves to its head and turns into a suction disk, with the help of which it attaches to sharks, whales, and ships. In angler fish, the dorsal fin moves to the snout and extends into a long thread that serves as a bait for prey.

The habitat of fish is all kinds of bodies of water on our planet: ponds, lakes, rivers, seas and oceans.

Fish occupy very vast territories; in any case, the ocean area exceeds 70% earth's surface. Add to this the fact that the deepest depressions go 11 thousand meters into the ocean depths and it becomes clear what spaces the fish own.

Life in water is extremely diverse, which could not but affect the appearance of fish, and led to the fact that the shape of their bodies is varied, like underwater life itself.

On the head of fish there are gill wings, lips and mouth, nostrils and eyes. The head merges into the body very smoothly. Starting from the gill wings to the anal fin there is a body that ends with a tail.

Fins serve as organs of movement for fish. In essence, they are skin outgrowths that rest on bony fin rays. The most important thing for fish is the caudal fin. On the sides of the body, in its lower part, there are paired ventral and pectoral fins, which correspond to the hind and forelimbs of vertebrates living on the earth. In different species of fish, paired fins can be located differently. At the top of the fish’s body there is a dorsal fin, and at the bottom, next to the tail, there is an anal fin. Moreover, it is important to note that the number of anal and dorsal fins in fish can vary.

Most fish have an organ on the sides of their body that senses the flow of water, called the “lateral line.” Thanks to this, even a blind fish is able to catch moving prey without bumping into obstacles. The visible part of the lateral line consists of scales with holes.

Through these holes, water penetrates into the channel running along the body, where it is sensed by the endings passing through the channel. nerve cells. The lateral line in fish can be continuous, intermittent, or absent altogether.

Functions of fins in fish

Thanks to the presence of fins, fish are able to move and maintain balance in the water. If the fish is deprived of fins, it will simply turn over with its belly up, since the center of gravity of the fish is located in its dorsal part.

The dorsal and anal fins provide the fish with a stable body position, and the caudal fin in almost all fish is a kind of propulsion device.

As for the paired fins (pelvic and pectoral), they mainly perform a stabilizing function, since they provide an equilibrium position of the body when the fish is immobilized. With the help of these fins, the fish can take the body position it needs. In addition, they are load-bearing planes during the movement of the fish, and serve as a rudder. As for the pectoral fins, they are a kind of small motor with which the fish moves during slow swimming. The pelvic fins are primarily used to maintain balance.

Body shape of fish

Fish are characterized by a streamlined body shape. This is a consequence of its lifestyle and habitat. For example, those fish that are adapted to long and fast swimming in the water column (for example, salmon, cod, herring, mackerel or tuna) have a body shape similar to a torpedo. Predators that practice lightning-fast throws over very short distances (for example, saury, garfish, taimen or) have an arrow-shaped body shape.

Some species of fish that are adapted to lying on the bottom for a long time, such as flounder or stingray, have a flat body. Some species of fish even have bizarre body shapes, which may resemble a chess knight, as can be seen in the horse, whose head is located perpendicular to the axis of the body.

The seahorse inhabits almost everything sea ​​waters Earth. His body is encased in a shell like that of an insect, his tail is tenacious like that of a monkey, his eyes can rotate like those of a chameleon, and the picture is complemented by a bag similar to that of a kangaroo. And although this strange fish can swim, maintaining a vertical body position, using the vibrations of the dorsal fin for this, it is still a useless swimmer. The seahorse uses its tubular snout as a “hunting pipette”: when prey appears nearby, the seahorse sharply inflates its cheeks and draws the prey into its mouth from a distance of 3-4 centimeters.

The smallest fish is the Philippine goby Pandaku. Its length is about seven millimeters. It even happened that women of fashion wore this bull in their ears, using aquarium earrings made of crystal.

But the most big fish is, whose body length is sometimes about fifteen meters.

Additional organs in fish

In some fish species, such as catfish or carp, antennae can be seen around the mouth. These organs perform a tactile function and are also used to determine taste qualities food. Many deep sea fish, such as photoblepharon, anchovy, hatchet fish and have luminous organs.

On the scales of fish you can sometimes find protective spines, which may be located in different parts bodies. For example, the body of a hedgehog fish is almost completely covered with spines. Certain fish species, such as the wartfish, sea ​​Dragon and, have special organs of attack and defense - poisonous glands, which are located at the base of the fin rays and the base of the spines.

Body coverings in fish

On the outside, the skin of fish is covered with thin translucent plates - scales. The ends of the scales overlap each other, arranged like tiles. On the one hand, this provides the animal with strong protection, and on the other hand, it does not interfere with free movement in the water. The scales are formed by special skin cells. The size of the scales can vary: in those they are almost microscopic, while in the Indian longhorned beetle they are several centimeters in diameter. Scales are distinguished by great diversity, both in their strength and in quantity, composition and a number of other characteristics.

The skin of fish contains chromatophores (pigment cells), when they expand, the pigment grains spread over a significant area, making the color of the body brighter. If the chromatophores are reduced, then the pigment grains will accumulate in the center and most of the cell will remain uncolored, due to which the body of the fish will become paler. When pigment grains of all colors are evenly distributed inside the chromatophores, the fish has a bright color, and if they are collected in the centers of the cells, the fish will be so colorless that it may even appear transparent.

If only yellow pigment grains are distributed among the chromatophores, the fish will change its color to light yellow. All the variety of colors of fish is determined by chromatophores. This is especially typical for tropical waters. In addition, the skin of fish contains organs that perceive chemical composition and water temperature.

From all of the above, it becomes clear that the skin of fish performs many functions at once, including external protection, protection from mechanical damage, and communication with external environment, and communication with relatives, and facilitating gliding.

The role of color in fish

Pelagic fish often have a dark back and a light-colored belly, for example, like a representative of the family cod fish abadejo. Many fish living in the middle and upper layers water color of the upper part of the body is much darker than the lower part. If you look at such fish from below, then its light belly will not stand out against the light background of the sky shining through the water column, which disguises the fish from those lying in wait for it. sea ​​predators. In the same way, when viewed from above, its dark back merges with the dark background of the seabed, which protects not only from predatory sea animals, but also from various fishing birds.

If you analyze the coloration of fish, you will notice how it is used to imitate and camouflage other organisms. Thanks to this, the fish demonstrates danger or inedibility, and also gives signals to other fish. IN mating season, many species of fish tend to acquire very bright colors, while the rest of the time they try to blend in with their environment or imitate a completely different animal. Often this color camouflage is complemented by the shape of the fish.

Internal structure of fish

The musculoskeletal system of fish, like that of land animals, consists of muscles and a skeleton. The skeleton is based on the spine and skull, consisting of individual vertebrae. Each vertebra has a thickened part called the vertebral body, as well as lower and upper arches. Together, the upper arches form a canal in which the spinal cord is located, which is protected from injury by the arches. In the upper direction, long spinous processes extend from the arches. In the body part the lower arches are open. In the caudal part of the spine, the lower arches form a canal through which blood vessels pass. The ribs are adjacent to the lateral processes of the vertebrae and perform a number of functions, primarily protection internal organs, and creating the necessary support for the muscles of the trunk. The most powerful muscles in fish are located in the tail and back.

The skeleton of a fish includes bones and bony rays of both paired and unpaired fins. In unpaired fins, the skeleton consists of many elongated bones attached to the thickness of the muscles. There is a single bone in the abdominal girdle. The free pelvic fin has a skeleton consisting of many long bones.

The skeleton of the head also includes a small skull. The bones of the skull serve as protection for the brain, but most of the skeleton of the head is occupied by the bones of the upper and lower jaws, the bones of the gill apparatus and the eye sockets. Speaking about the gill apparatus, we can primarily note the large gill covers. If you lift the gill covers a little, then underneath you can see paired gill arches: left and right. Gills are located on these arches.

As for the muscles, there are few of them in the head; they are located mostly in the area of ​​the gill covers, on the back of the head and jaws.

The muscles that provide movement are attached to the skeletal bones. The main part of the muscles is evenly located in the dorsal part of the animal’s body. The most developed muscles are those that move the tail.

Functions musculoskeletal system in the body of fish are very different. The skeleton serves as protection for internal organs, bony fin rays protect the fish from rivals and predators, and the entire skeleton in combination with muscles allows this inhabitant of the waters to move and protect itself from collisions and impacts.

Digestive system in fish

Begins digestive system a large mouth, which is located in front of the head and is armed with jaws. There are large small teeth. Behind the oral cavity is the pharyngeal cavity, in which you can see the gill slits, which are separated by interbranchial septa on which the gills are located. Outside, the gills are covered with gill covers. Next is the esophagus, followed by a fairly voluminous stomach. Behind it is the intestine.

The stomach and intestines, using the action of digestive juices, digest food, and gastric juice acts in the stomach, and in the intestine several juices are secreted by the glands of the intestinal walls, as well as the walls of the pancreas. Bile coming from the liver and gallbladder is also involved in this process. Water and food digested in the intestines are absorbed into the blood, and undigested remains are thrown out through the anus.

A special organ that is found only in bony fish is the swim bladder, which is located under the spine in the body cavity. The swim bladder arises during embryonic development as a dorsal outgrowth of the intestinal tube. In order for the bladder to be filled with air, the newly born fry floats to the surface of the water and swallows air into its esophagus. After some time, the connection between the esophagus and the swim bladder is interrupted.

It is interesting that some fish use their swim bladder as a means by which they amplify the sounds they make. True, some fish do not have a swim bladder. Usually these are those fish that live on the bottom, as well as those that are characterized by vertical rapid movements.

Thanks to the swim bladder, the fish does not sink under its own weight. This organ consists of one or two chambers and is filled with a mixture of gases, which in its composition is close to air. The volume of gases contained in the swim bladder can change when they are absorbed and released through the blood vessels of the swim bladder walls, as well as when air is swallowed. Thus, specific gravity fish and the volume of its body and can change in one direction or another. The swim bladder provides the fish with balance between its body mass and the buoyant force acting on it at a certain depth.

Gill apparatus in fish

As a skeletal support for the gill apparatus, fish serve four pairs of gill arches located in a vertical plane, to which the gill plates are attached. They consist of fringe-like gill filaments.

Inside the gill filaments there are blood vessels that branch into capillaries. Gas exchange occurs through the walls of the capillaries: oxygen is absorbed from the water and released back carbon dioxide. Thanks to the contraction of the muscles of the pharynx, as well as due to the movements of the gill covers, water moves between the gill filaments, which have gill rakers that protect the delicate soft gills from clogging them with food particles.

Circulatory system in fish

Schematically, circulatory system fish can be depicted as consisting of vessels vicious circle. The main organ of this system is the two-chamber heart, consisting of an atrium and a ventricle, which ensures blood circulation throughout the animal’s body. Moving through the vessels, blood ensures gas exchange, as well as the transfer nutrients in the body, and some other substances.

In fish, the circulatory system includes one circulation. The heart sends blood to the gills, where it is enriched with oxygen. This oxygenated blood is called arterial blood, and is carried throughout the body, distributing oxygen to the cells. At the same time, it is saturated with carbon dioxide (in other words, it becomes venous), after which the blood returns back to the heart. It should be recalled that in all vertebrates, the vessels leaving the heart are called arteries, while those returning to it are called veins.

The excretory organs in fish are responsible for removing metabolic end products from the body, filtering blood and removing water from the body. They are represented by paired kidneys, which are located along the spine by the ureters. Some fish have a bladder.

The kidneys remove excess fluid from the blood vessels, harmful products exchange and salts. The ureters carry urine into the bladder, from where it is pumped out. Externally, the urinary canal opens with an opening located slightly behind the anus.

Through these organs, fish remove excess salts, water and metabolic products harmful to the body.

Metabolism in fish

Metabolism is the totality of chemical processes occurring in the body. The basis of metabolism in any organism is the construction of organic substances and their breakdown. When complex substances enter the fish’s body along with food organic matter, during the process of digestion, they are transformed into less complex ones, which, being absorbed into the blood, are carried throughout the cells of the body. There they form the proteins, carbohydrates and fats required by the body. Of course, this uses up the energy released during breathing. At the same time, many substances in cells break down into urea, carbon dioxide and water. Therefore, metabolism is a combination of the process of construction and breakdown of substances.

The intensity with which metabolism occurs in a fish’s body depends on its body temperature. Since fish are animals with variable body temperatures, that is, cold-blooded, their body temperature is in close proximity to the ambient temperature. As a rule, the body temperature of fish does not exceed the ambient temperature by more than one degree. True, in some fish, for example tuna, the difference can be about ten degrees.

Nervous system of fish

The nervous system is responsible for the coherence of all organs and systems of the body. It also ensures the body’s response to certain changes in environment. It consists of a central nervous system(spinal cord and brain) and the peripheral nervous system (branches extending from the brain and spinal cord). The fish brain consists of five sections: the anterior, which includes the optic lobes, the middle, intermediate, cerebellum and medulla oblongata. In all active pelagic fish, the cerebellum and optic lobes are quite large, since they need fine coordination and good vision. The medulla oblongata in fish passes into the spinal cord, ending in the caudal spine.

With the help of the nervous system, the fish’s body responds to irritations. These reactions are called reflexes, which can be divided into conditioned reflexes and unconditional. The latter are also called innate reflexes. Unconditioned reflexes in all animals belonging to the same species they manifest themselves in the same way, while conditioned reflexes are individual and are developed during the life of a particular fish.

Sense organs in fish

The sense organs of fish are very well developed. The eyes are able to clearly recognize objects at close range and distinguish colors. Fish perceive sounds through the inner ear located inside the skull, and smells are recognized through the nostrils. In the oral cavity, the skin of the lips and antennae, there are taste organs that allow fish to distinguish between salty, sour and sweet. The lateral line, thanks to the sensitive cells located in it, reacts sensitively to changes in water pressure and transmits corresponding signals to the brain.

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Take a closer look at the movements of the fish in the water, and you will see which part of the body takes the main part in this (Fig. 8). The fish rushes forward, quickly moving its tail to the right and left, which ends in a wide caudal fin. The body of the fish also takes part in this movement, but it is mainly carried out by the tail section of the body.

Therefore, the tail of the fish is very muscular and massive, almost imperceptibly merging with the body (compare in this regard with land mammals like a cat or a dog), for example, in a perch the body, inside of which all the insides are contained, ends only a little further than half the total length of its body, and the rest is its tail.

In addition to the caudal fin, the fish has two more unpaired fins - on top of the dorsal (in perch, pike perch and some other fish it consists of two separate protrusions located one behind the other) and below the subcaudal, or anal, which is so called because it sits on the underside of the tail, just behind the anus.

These fins prevent the body from rotating around the longitudinal axis (Fig. 9) and, like a keel on a ship, help the fish maintain a normal position in the water; In some fish, the dorsal fin also serves as a reliable weapon of defense. It can have such a meaning if the fin rays supporting it are hard, prickly needles that prevent more large predator swallow fish (ruff, perch).

Then we see the fish have more paired fins - a pair of pectoral and a pair of abdominal ones.

The pectoral fins sit higher, almost on the sides of the body, while the pelvic fins are closer together and located on the ventral side.

The location of the fins varies among different fish. Usually the pelvic fins are located behind the pectoral fins, as we see, for example, in pike (gastrofinned fish; see Fig. 52), in other fish the pelvic fins have moved to the front of the body and are located between the two pectoral fins (pectoral finned fish, Fig. 10) , and finally, in burbot and some sea ​​fish, for example, cod, haddock (Fig. 80, 81) and navaga, the pelvic fins sit in front of the pectoral fins, as if on the throat of the fish (throat-finned fish).

The paired fins do not have strong muscles (check this on a dried roach). Therefore, they cannot influence the speed of movement, and fish row with them only when moving very slowly in calm, standing water (carp, crucian carp, goldfish).

Their main purpose is to maintain body balance. A dead or weakened fish turns over with its belly up, since the back of the fish turns out to be heavier than its ventral side (we will see why during the autopsy). This means that a living fish has to make some effort all the time so as not to tip over on its back or fall to its side; this is achieved by the work of paired fins.

You can verify this through a simple experiment by depriving the fish of the opportunity to use its paired fins and tying them to the body with woolen threads.

In fish with tied pectoral fins, the heavier head end is pulled and lowered; fish whose pectoral or ventral fins are cut off or tied on one side lie on their sides, and a fish in which all paired fins are tied with threads turns upside down, as if dead.

(Here, however, there are exceptions: in those species of fish in which the swim bladder is located closer to the dorsal side, the belly may be heavier than the back, and the fish will not turn over.)

In addition, paired fins help the fish make turns: when wanting to turn to the right, the fish paddles with the left fin, and presses the right one to the body, and vice versa.

Let us return once again to clarify the role of the dorsal and subcaudal fins. Sometimes, not only in the students' answers, but also in the teacher's explanations, it seems as if they are the ones who give the body a normal position - back up.

In fact, as we have seen, paired fins perform this role, while the dorsal and subcaudal fins, when the fish moves, prevent its fusiform body from spinning around the longitudinal axis and thereby maintain the normal position that the paired fins gave the body (in a weakened fish swimming on its side or belly up, the same unpaired fins support the abnormal position already assumed by the body).

• Read: Variety of fish: shape, size, color

Fish fins: shape, structure.

• Read more: Buoyancy of fish;

Swimming fish;

Flying fish

Different fish have different sizes, shapes, numbers, positions and functions of fins. But their initial and main role boils down to the fact that the fins allow the body to maintain balance in the water and participate in maneuverable movement.

All fins in fish are divided into paired, which correspond to the limbs of higher vertebrates, and unpaired. Paired fins include pectoral (P - pinna pectoralis) and ventral (V - pinna ventralis). The unpaired fins include the dorsal (D - p. dorsalis); anal (A - r. analis) and caudal (C - r. caudalis). A number of groups of fish, in particular salmon, characins, killer whales, and others, have a so-called adipose fin behind the dorsal fin, which is devoid of fin rays (p.adiposa). Pectoral fins are common in bony fishes, while they are absent in moray eels and some others. Lampreys and hagfish are completely devoid of both pectoral and ventral fins. In stingrays, on the contrary, the pectoral fins are greatly enlarged and play the main role as organs of their movement. But pectoral fins have developed especially strongly in flying fish, which allows them to jump out onto high speed out of the water, literally soaring in the air, while flying long distances over the water. Three beams pectoral fin at

sea ​​cock completely separate and act as legs when crawling on the ground. The pelvic fins of various fish can occupy

In some species of fish, the pelvic fins are transformed into spines - like those of sticklebacks, or into suckers, like those of lumpfish. In male sharks and rays, the posterior rays of the ventral fins during the process of evolution were transformed into copulatory organs and are called pterygopodia. Pelvic fins are completely absent in eels, catfish, etc.

Different groups of fish may have different quantity dorsal fins. Thus, herring and cyprinids have one, mullet and perch have two dorsal fins, and cods have three. In this case, the location of the dorsal fins may be different. In pike, the dorsal fin is shifted far back, in herrings and carp-like fish it is located in the middle of the body, and in fish such as perch and cod, which have a massive front part of the body, one of them is located closer to the head. The longest and highest dorsal fin of the sailfish fish, reaching really large sizes. In flounder it looks like a long ribbon running along the entire back and, at the same time as the almost identical anal one, is their main organ of movement. And mackerel-like fish such as mackerel, tuna and saury acquired in the process of evolution small additional fins located behind the dorsal and anal fins.

Individual rays of the dorsal fin sometimes extend into long threads, and monkfish the first ray of the dorsal fin is shifted to the muzzle and transformed into a kind of fishing rod. It is he who plays the role of bait, just like deep sea anglerfish. The latter have a special bait on this fishing rod, which is their luminous organ. The first dorsal fin of the sticky fish also moved to the head and turned into a real sucker. The dorsal fin in sedentary bottom-dwelling fish species is poorly developed, such as in catfish, or may be completely absent, as in stingrays. The famous electric eel also lacks a dorsal fin....