Internal structure of bony fishes - general arrangement and structure of internal organs. River perch
Fish - aquatic animals, adapted to life in fresh water bodies and sea water. They have a hard skeleton (bone, cartilaginous or partially ossified).
Let us consider the structural features and vital functions of fish using the example of river perch.
Habitat and external structure fish using the example of river perch
River perch lives in freshwater bodies (slowly flowing rivers and lakes) in Europe, Siberia and Central Asia. Water exhibits noticeable resistance to bodies moving in it. Perch, like many other fish, has streamlined shape- this helps him move quickly in the water. The perch's head smoothly transitions into the body, and the body into the tail. At the pointed front end of the head there is a mouth with lips that can open wide.
Figure: external structure of river perch
On the top of the head two pairs of small holes are visible - nostrils leading to the olfactory organ. On its sides there are two large eyes.
Perch fins
Bending the laterally flattened body and tail first to the right and then to the left, the perch moves forward. When swimming big role fins play. Each fin consists of a thin membrane of skin, which is supported by bony fin rays. When the rays spread out, the skin between them tightens and the surface of the fin increases. On the back of the perch there are two fin pins: front big And the rear one is smaller. Number of dorsal fins different types fish may vary. At the end of the tail there is a large two-lobed caudal fin, on the underside of the tail - anal. All these fins are unpaired. Fish also have paired fins - there are always two pairs of them. Pectoral fins(front pair of limbs) are placed on the sides of the perch’s body behind the head, paired pelvic fins (back pair of limbs) are on the underside of the body. Main role plays when moving forward caudal fin. The paired fins are important for turning, stopping, moving forward slowly, and maintaining balance.
The dorsal and anal fins give the fish body stability when moving forward and making sharp turns.
Cover and color of perch
The body of the perch is covered bone scales. Each scale with its front edge is immersed in the skin, and with its rear edge it overlaps the scales of the next row. Together they form a protective cover - scales that does not interfere with body movements. As the fish grows, the scales also increase in size and can be used to determine the age of the fish.
The outside of the scales is covered with a layer of mucus, which is secreted by the skin glands. Mucus reduces friction between the fish's body and water and serves as protection against bacteria and mold.
Like most fish, the belly of the perch is lighter than the back. Top back to to a certain extent merges with dark background bottom. From below, the light belly is less noticeable against the light background of the water surface.
The body color of a perch depends on the environment. In forest lakes with a dark bottom it has dark color, sometimes even completely black perches are found there. Perches with light and bright colors live in reservoirs with a light sandy bottom. Perch often hides in thickets. Here the greenish color of its sides with vertical dark stripes makes the perch invisible. This protective coloring helps him hide from enemies and better watch over his prey.
Along the sides of the perch's body from head to tail runs a narrow dark lateral line. This is a kind of sensory organ.
Skeleton of a river perch
The skeleton of a perch consists of large number bones. Its basis is the spine, which stretches along the entire body of the fish from the head to the caudal fin. The spine is formed a large number vertebrae (perch has 39-42).
Figure: Skeleton of a river perch
When a perch develops in the egg, a notochord appears in the place of its future spine. Later, vertebrae appear around the notochord. In adult perch, only small cartilaginous remains between the vertebrae are preserved from the notochord.
Each vertebra consists of body And upper arch, ending in a long upper process. Taken together, the upper arches together with the vertebral bodies form the spinal canal, which contains spinal cord.
IN trunk section the bodies are attached to the vertebrae laterally ribs. There are no ribs in the caudal region; each vertebra located in it is equipped with a lower arch ending in a long lower process.
In front, the skeleton of the head is firmly articulated with the spine - scull. There is also a skeleton in the fins.
In paired pectoral fins, the skeleton of the fins is connected to the spine by bones shoulder girdle. The bones connecting the skeleton of the paired pelvic fins to the spine are not developed in the perch.
The skeleton has great importance: it serves as a support for the muscles and protection for internal organs.
River perch muscles
Under the skin there are muscles attached to the bones that form muscles. The strongest of them are located on the dorsal side of the body and in the tail.
The contraction and relaxation of muscles causes the fish's body to bend, allowing it to move in the water. The head and fins contain muscles that move the jaws, gill covers and fins.
Swim bladder of river perch
River perch, like any fish, is heavier than water. Its buoyancy ensures swim bladder . It is located in the abdominal cavity above the intestines and has the shape of a translucent sac filled with gas.
Figure: Internal structure of river perch. Digestive and excretory system
The swim bladder is formed in the perch embryo as an outgrowth of the intestine on the dorsal side. It loses connection with the gut during the larval stage. The larva should float to the surface of the water 2-3 days after hatching and swallow a little atmospheric air to fill the swim bladder. If this does not happen, the larva cannot swim and dies.
By regulating the volume of the swim bladder, the perch stays at a certain depth, floats up or sinks. When the bladder contracts, excess gas is absorbed by the blood in the capillaries inner surface bubble If the bubble expands, gas enters it from the blood. When the perch sinks into the depths, the bubble decreases in volume - and the density of the fish increases. This promotes rapid immersion. When floating, the volume of the bubble increases and the fish becomes relatively lighter. At the same depth, the volume of the fish's bladder does not change. This allows the fish to remain motionless, as if hanging in the water column.
Unlike river perch, in other fish, such as carp, bream, roach, herring, the swim bladder remains connected to the intestine using an air duct - a thin tube throughout life. Excess gas exits through this duct into the intestines, and from there through the mouth and gill slits into the water.
The main function of the swim bladder is to provide buoyancy for fish. In addition, it helps fish hear better, since, being a good resonator, it amplifies sounds.
CLASS BONE FISHES (OSTEICHTHYES)
Lesson 6. DIVERSITY OF BONE FISHES IN CONNECTION WITH EXISTENCE CONDITIONS. EXTERNAL AND INTERNAL STRUCTURE OF BONE FISHES BY THE EXAMPLE OF RIVER PERCH
Systematic object position
Phylum Chordata
Subphylum Vertebrata
Group Jaws (Gnathostomata)
Superclass Pisces
Class Bony fishes (Osteichthyes)
Subclass Ray-finned (Actinopterigii)
Superorder Teleostei
Order Perciformes
Family Percidae
Representative - river perch (Perca fluviatilis)
Equipment and materials
1. Fresh fish (one for two students).
2. Ready-made preparations: 1) opened fish; 2) digestive system; 3) injected circulatory system; 4) brain (one for two students).
3. Dissecting tools: scalpel, scissors, tweezers, dissecting needle, stationery pins (one set for two students).
4. Baths (one for two students).
5. Tables: 1) tables on diversity; 2) appearance bony fish; 3) general location internal organs; 4) digestive system; 5) circulatory system; 6) reproductive organs of the male and female; 7) brain.
Introductory Notes
Variety of bony fish
The class of Bony fishes includes more than 20 thousand modern species. They live in a variety of bodies of water: seas, oceans, rivers, lakes, ponds, streams.
Fish are adapted to a variety of aquatic conditions. They live in bodies of water with varying degrees of salinity, only avoiding oversaturation with salt. They inhabit waters with different temperature conditions: cold-blooded fish (ice, saber) live in waters with a temperature level of about 0°C. Some freshwater species (crucian carp) are able to survive when water bodies freeze in winter. There are fish in hot springs (from the family Cyprinodontiformes). They have different demands on the oxygen content in water. Bony fish have mastered different depths of the World Ocean and water flows from at different speeds moving water.
Representatives of this class are extremely diverse in their appearance and lifestyle (Fig. 25). According to the nature of connections with the environment, fish are divided into various ecological groups ( life forms). First of all, a distinction is made between marine and freshwater fish. In the seas of the World Ocean live most herrings, cod (haddock, pollock, navaga, cod), tuna, mackerel, garfish, flounder, sailfish, pufferfish and many others. Freshwater bodies of temperate climate
Rice. 25. Environmental groups fish:
Fishes that live in the water column (nektonic; pelagic). Sea: 1 - tuna; 2 - sailboat; 3 - body; 4 - moon fish; freshwater: 5 - crucian carp; 6 - carp; 7 - bream. Bottom fish (benthic). Marine: 8 - flounder; 9 - sand goby; 10 - angler; 11 - deep sea anglerfish; freshwater: 12 - common catfish; 13 - loach; 14 - pike. Specific adaptations in fish: 15 - flying fish; 16 - mudskipper
inhabited by representatives of cyprinids (rudd, carp, silver carp, gudgeon, crucian carp, catfish, loach, etc.). Perch species (perch, pike perch, ruffe) and stickleback species also live here. In the tropical waters of different continents live polyfins, piranhas, shellfish, etc. There are species that occupy an intermediate position - these are migratory fish. They live either in fresh or salty environments, depending on biological needs: for example, sturgeon and salmon fish go from seas to rivers to spawn, making so-called anadromous migrations, and river eels To spawn, they swim from rivers to the ocean; their migrations are called catadromous.
Inside a reservoir, some fish stay in the water column (nektonic, pelagic), others - near the bottom (bottom, benthic). Habitat leaves its mark on appearance fish. In accordance with this, different ecological types of fish are distinguished. Nektonic (pelagic) fish are usually distinguished by their speed and good buoyancy. Their elongated body is torpedo-shaped (sailfish, mackerel, tuna) or strongly flattened laterally (herring). Fish swim quickly thanks to frequent lateral oscillatory movements of the back of the body, tail and well-developed caudal fin. Some salmon fish overcome rapid oncoming water flows and successfully move forward. The speed of a hunting sailboat exceeds 100 km/h, and that of a salmon exceeds 20 km/h.
Among pelagic fish there are species that are not capable of developing higher speed on one's own. They “attach” to the body of a fast-swimming fish (pilots) or stick to it (sticking fish).
The rapid movement of some fish is aided by elongated paired fins. They are used by garfish flying fish. Fleeing from predators, they jump out of the water and cover more than 200 m in a gliding flight.
Many nektonic fish lead a schooling lifestyle, have coordinated behavior and maneuver well in the water.
Bottom fish are rather slow and often lead a solitary lifestyle. Their body is either strongly flattened, like those of flounders, or elongated and laterally compressed closer to the tail, like those of catfish, loaches, and moray eels. Their dorsal and anal fins grow, and their wave-like movements are involved in the slow movements of these fish near the bottom. In some benthic fish, modified pectoral fins allow them to quickly move (“crawl”) along the bottom (sea cocks, scorpionfish, gobies).
Deep-sea (abyssal) fish species also have specific adaptations.
Based on the nature of their diet, they distinguish: 1) active predators (large sturgeon, sailfish, tuna, etc.); 2) planktivores (herring, anchovies, sunfish); 3) bottom benthic eaters (flounder, eels, anglerfish). In fresh water bodies, active predators are pike-perch, pike, and perch; They eat plankton - roach, rudd, and other cyprinids extract food by digging in the bottom soil; among them there are herbivorous species.
General features of the organization
Despite the great external and systematic diversity, all bony fishes are characterized by character traits, distinguishing them from cartilaginous fish. The skeleton of bony fishes is, to one degree or another, bony of integumentary or chondral origin. In the vast majority of species, the interbranch septa are reduced and the gill filaments sit directly on the gill arches. The gill apparatus is covered with an operculum. There is a swim bladder, an important hydrostatic organ. Fertilization in most bony fish is external, the eggs are small and their quantity is large.
Features of the organization of bony fishes will be considered using the example of the superorder of bony fishes from the subclass of ray-finned fishes, which make up more than 90% of living fish species. Compared to cartilaginous fish, bony fish are characterized by a simplified structure of the skeleton of paired fins: the pectoral and ventral fins lack basalia, and the pelvic fins also lack radials. The pectoral fins are located vertically, under the body. The mouth is located at the end of the head, but can have different positions. The caudal fin is homocercal. The colon does not have a spiral valve. In many bony fish, the intestine has blind (pyloric) outgrowths and ends in the anus. There is no cloaca. The body is covered with bone scales consisting of thin plates. Instead of the arterial cone, the aortic bulb appears.
Explore the external and internal structure perch
Consider:
External structure
The body is divided into head, torso and tail; fins: paired - pectoral and abdominal, unpaired - dorsal, subcaudal (anal) and caudal; mouth opening; paired nostrils; eyes; gill covers; lateral line; genital, excretory and anal openings; bone scales.
Internal structure
Digestive system: oral cavity; pharynx; esophagus; stomach; small, thick, rectum; pyloric growths; liver; gallbladder; pancreas.
Respiratory system: four pairs of gills.
Circulatory system: two-chambered heart (atrium and ventricle); aortic bulb; abdominal aorta; four pairs of gill arteries. Using the drug, drawing and table, trace the blood circulation pattern.
Excretory organs: trunk buds; ureters; bladder.
Reproductive organs: testes; ovaries; genital ducts.
Central nervous system: brain (forebrain hemispheres with olfactory lobes, diencephalon, midbrain, cerebellum, medulla); eyes; optic chiasm (chiasm); spinal cord.
Sketch:
1) general location of internal organs; 2) brain (top); 3) diagram circulatory system(homework).
External structure
The body of bony fish, like cartilaginous fish, is divided into the head, body and tail. The boundary between the head and the body is the gill slit, and between the body and the tail is the anus (Fig. 26). The mouth of bony fishes is located at the anterior end of the head, which is why such fish are called limb-stomes in contrast to the transverse-mouthed shark fishes. It can be moved slightly up or down. There are large eyes on the sides of the head. They have a flat cornea and a round lens. Eyelids are missing. Paired nostrils are visible in front - the organs of smell. Each nostril is divided by a valve into two openings: when the fish moves, water enters through the front and exits through the back. This is how the epithelium of the olfactory fossa is washed. The right and left nostrils do not communicate with each other or with the oral cavity.
A characteristic formation for bony fish is the bony gill cover. In this regard, instead of five gill openings, like in cartilaginous fish, on the surface of the body bone fish one gill slit is visible. Paired fins, compared to those of cartilaginous fish, are simplified and located in a vertical plane. The caudal fin is homocercal type. The vertebral column extends into the upper lobe of the caudal fin, but both fin lobes are identical. Dorsal fins
Rice. 26. Internal structure of perch:
1 - mouth with teeth; 2 - gill cover (part of it has been removed); 3 - bone scales; 4 - homocercal caudal fin; 5 - dorsal fins; 6 - anal fin; 7 - eye; 8 - nostril; 9 - lateral line; 10 - anus; 11 - genital opening; 12 - excretory opening; 13 - opened stomach with longitudinal folds; 14 - intestines; 15 - pyloric outgrowths; 16 - rectum; 17 - liver; 18 - gallbladder; 19 - pancreas; 20 - gill filaments; 21 - spleen; 22 - swim bladder; 23 - kidney; 24 - ureter; 25 - bladder; 26 - ovary; 27 - atrium; 28 - ventricle; 29 - aortic bulb; 30 - abdominal aorta; 31 - gill rakers
equipped with soft branched or hard spiny rays. The rays are interconnected by a thin leathery membrane.
On the lower side of the body, closer to the rear end, there is a subcaudal, or anal, fin. In front of it, in a common recess, there are three openings: anal, genital and excretory (cartilaginous fish have a cloaca). A clearly visible lateral line stretches along the body - an organ that perceives weak movements of water and infrasonic vibrations.
The body of the bony fish is covered with skin. It distinguishes between the epidermis and cutis. At their border is the basement membrane. The skin contains bone scales. Each scale lies with one edge in a skin pocket. The scales overlap each other in a tiled manner. The structure of the scale can be seen by selecting it with tweezers and examining it against the light or under a microscope. The scales can be cycloid, with a smooth inner edge, or ctenoid, with a jagged edge. Light (wide) and dark (narrow) colors are visible on the scales. tree rings. In summer, with intensive growth of fish, a significant increase in scales occurs - a wide,
light layer. In winter, fish growth and scale growth are insignificant - the layer is compacted, narrow, dark. By counting the light and dark rings on a fish's scales under a microscope, its age can be determined.
The skin glands of the epidermis secrete mucus, which abundantly covers the body of the fish. It promotes better movement of fish in dense aquatic environment. The coloring of fish is characterized by the fact that dorsal side usually darker than belly.
Internal structure
Opening
Take a small fish left hand belly up. Insert the sharp end of the scissors into the anus and make an incision along ventral side body to head, all the way to the mouth. In this case, you need to press the scissors from the bottom up, without lowering their ends deep, so as not to damage the internal organs. Cut shoulder girdle, which will be encountered on the path of the cut. After making a longitudinal incision, place the fish on its right side, insert the blunt end of the scissors into the incision made near the anus and cut the body wall upward, towards the lateral line. Make a second transverse incision near the operculum. Next, make a longitudinal cut along the lateral line, connecting both transverse cuts. Unscrew the resulting flap of fabric and remove it.
At the anterior end of the body, expose the gills and heart. To do this, cut off the gill cover and shoulder girdle. The heart lies almost immediately under the gills. To expose the brain, the skull cap must be carefully removed. Take the fish in your left hand with its back up, head away from you. Make a transverse incision with scissors in the back of the brain case at the back of the head. Make the side cuts along the edges of the skull forward. Finish with a cross-cut at the front of the head (in front of the eyes). Grasp the skull roof with tweezers and carefully remove it. View the brain from above.
To view the brain from below, you need to cut the medulla oblongata and tilt the brain forward. To examine the structure of the eye, it should be removed from the eye orbit.
General location of internal organs
Using an opened fish, let's look at the general location of the internal organs (see Fig. 26). The trunk muscles are clearly visible under the skin. It has a metameric structure.
Under the operculum lie four pairs of gill arches, on which there are gills, and behind them, below them, there is a two-chambered heart. In front of the ventricle, there is a noticeable expansion of the abdominal aorta - the aortic bulb, from which the abdominal aorta originates. In the anterior abdominal cavity, a large liver covering the stomach is clearly visible. There is a gallbladder, the duct of which opens into duodenum. An intestinal tube extends from the stomach. Pyloric growths are visible at the border of the stomach and intestines. The pancreas of most fish is located dispersedly between the stomach and the adjacent intestinal loop. In one of the intestinal loops there is a dark burgundy spleen.
In the back of the body cavity lie the genital organs - the testes or ovaries. The degree of their development depends on the season in which the fish was caught and its age. The testes are distinguished by their milky-cream color, which is why they are called milts. The ovaries are represented by elongated bags of yellowish-orange color with a granular structure (caviar).
Above all the abdominal organs, under the spinal column, lies the swim bladder. It is known that it is absent in cartilaginous fish. The swim bladder is embryonically formed from the dorsal wall of the intestine. This is an important hydrostatic organ that allows fish in the water column to maintain the density of their body in balance with the buoyant force and gravity, maintaining neutral buoyancy at each depth. With the help of the swim bladder, the fish can perceive external pressure and transmit its changes to the balance organs. In some fish, the swim bladder can serve as a respiratory organ and contribute to the perception and production of sounds. Under the spine, dark red buds stretch along the upper side of the body cavity. Bony fish have a bladder.
Organ systems
Digestive system
The digestive system of bony fish in comparison with that of cartilaginous fish is elongated, but less differentiated. The intestine is represented by a homogeneous tube, and the boundaries between the foregut, middle and hindgut are difficult to notice.
The mouth is equipped with jaws that bear teeth. Often the teeth sit on the vomer and gill bones. The oral cavity passes into the wide pharynx, which, in turn, into the short esophagus and stomach. The size and shape of the stomach depends on the nature of the diet. In carnivores
In fish (for example, perch), the stomach is voluminous, capable of stretching, and differs sharply from subsequent sections of the intestine. If swallowed large production The stomach of a predatory fish expands due to stretching of the longitudinal folds of its walls. In herbivorous fish (for example, cyprinids), the boundaries between the stomach and intestines are little noticeable. The intestines extend from the stomach. In bony fish, unlike elasmobranchs, it is longer and forms loops. In many fish, the increase in the absorptive surface of the intestine is carried out due to the caeca, pyloric processes extending from the anterior part of the small intestine. River perch has three pyloric outgrowths, some salmon fish their number reaches four hundred. Carp, pike, and catfish do not have them.
To the anterior section small intestine- duodenum - the ducts of the liver, gall bladder and pancreas flow into it. Under the influence of enzymes in the alkaline environment of the intestine, the main components of food are broken down.
The small intestine smoothly passes into the large intestine, then comes the rectum, which ends at the anus (anus).
All fish have a developed liver - an important digestive gland. Its secret: bile accumulates in the gallbladder, and then bile ducts enters the anterior intestine. Bile emulsifies fats and activates the enzyme that breaks down fat (lipase). In addition to participating in digestion, the liver plays important role in neutralization toxic substances And harmful products metabolism. Therefore, it is called a barrier organ. Glycogen accumulates in the liver and urea is formed.
The second digestive gland - the pancreas - is usually located diffusely or in the form of lobules on the mesentery at the beginning of the small intestine. In some fish (for example, pike) it is a compact formation, in others (cyprinids) it is scattered in the form of small fat-like inclusions between the bends of the intestinal tube. The pancreas secretes a complex of digestive enzymes that break down proteins, fats and carbohydrates. At the same time, it is an endocrine gland that ensures the balance of carbohydrate metabolism.
Respiratory system
The gill apparatus of bony fish, in contrast to that of cartilaginous fish, is characterized by the absence of interbranchial septa. The gill filaments sit directly on the gill arches (Fig. 27). There is an operculum - a hard bony plate,
Rice. 27. Gills of a shark (A, C) and bony fish (B, D):
A - frontal section through the oropharyngeal cavity of the shark; B - the same as bony fish; B - cross section through the gill of a shark; D - the same for bony fish: 1 - oropharyngeal cavity; 2 - esophagus; 3 - jaw arch; 4 - hyoid arch; 5 - spray bottle; 6 - internal gill slits; 7 - external gill slits; 8 - gill cover; 9 - gill arches; 10 - gill filaments; 11 - interbranchial septa
covering the gills, as a result of which only one gill opening is preserved.
Each gill of bony fishes is composed of two semi-gills attached to a bony gill arch, to which gill filaments are attached. They are pierced by the capillaries of the afferent branchial artery. Like cartilaginous fish, the gill filaments are of ectodermal origin. On inside Gill rakers are located on the gill arches, forming a kind of filtering apparatus - a sieve that prevents food from penetrating to the gills, but allows water to enter the peribranchial cavity. In bony fishes, four pairs of gill arches are well developed, the arch of the fifth pair is greatly shortened.
On the inner side of the operculum, one can note the remains of an additional semi-branch - a pseudobranch. She most likely does not take an active part in the exchange of gases.
The act of respiration of bony fish is carried out thanks to the sucking mechanism due to the movement of the gill cover. When the operculum is raised, the thin, leathery gill membrane located along the edge of the operculum is pressed against the gill slit under the influence of external water pressure. As a result, a space with
low blood pressure. This causes the flow of water entering through the mouth to rush through the pharynx into the peribranchial cavity. When the lid is lowered, excess pressure is created in the peribranch cavity and water, pushing each gill cover aside, is pushed out through the external gill openings. When a fish moves rapidly, the current of water passes through the gill apparatus without the participation of gill covers(ram type of breathing).
Circulatory system
The circulatory system of bony fish, when compared with the circulatory system of cartilaginous fish, differs in some features. Thus, in bony fish (Fig. 28), in the initial part of the abdominal aorta, instead of the arterial cone, an aortic bulb develops. It is a thickening of the aorta and has, like everyone else, blood vessels, smooth muscles. There are only four pairs of afferent and efferent gill arteries (cartilaginous fish have five pairs). The lateral veins disappear. The heart is located on the ventral side of the body near the head. It is enclosed in the pericardial sac. The dark burgundy atrium is clearly visible. Above the atrium is the venous sinus (sinus), which looks like a funnel and collects venous blood from the entire body. Bottom to
Rice. 28. Diagram of the circulatory system of a bony fish:
1 - atrium; 2 - ventricle; 3 - aortic bulb; 4 - abdominal aorta; 5 - afferent gill arteries; 6 - efferent branchial arteries; 7 - aortic roots; 8 - dorsal aorta; 9 - carotid arteries; 10 - subclavian arteries; 11 - tail vein; 12 - right posterior cardinal vein; 13 - left posterior cardinal vein; 14 - renal portal system; 15 - subintestinal vein; 16 - portal system of the liver; 17 - duct of Cuvier; 18 - hepatic vein; 19 - anterior cardinal or jugular veins; 20 - left portal vein of the kidney. Vessels containing venous blood are painted black.
The atrium is adjacent to a bright red muscular ventricle. The difference in color of the atrium and ventricle is due to the thickness of their walls. In the thin-walled atrium, venous blood shines through and creates a darker color tone of its wall. Thick muscular walls are clearly visible in the ventricle.
The abdominal aorta extends forward from the ventricle, which at its base expands into the aortic bulb. (Remember that in elasmobranch fishes the arterial cone lies in this place.) From the abdominal aorta, blood is directed through the afferent gill arteries to the gills, in the capillaries of which it gives off carbon dioxide, then flows through the efferent branchial arteries into the paired roots of the aorta and then goes to the dorsal aorta. The vessels that carry arterial blood to the head are called carotid arteries.
The dorsal aorta, which lies under the spine, carries blood to the tail. This aorta gives branches to all organs: the stomach, intestines, genitals, kidneys, fore and hind limbs. On the body of an opened fish, the dorsal aorta is clearly visible between the kidneys.
Venous blood, as in cartilaginous fish, returns to the heart through the azygos caudal vein and through the paired posterior and anterior cardinal (jugular) veins. The posterior cardinal veins, passing through the kidneys, break up into a network of capillaries, forming the renal portal system.
The posterior cardinal veins on each side of the body merge with the anterior cardinal veins to form the ducts of Cuvier. The intestinal vein passes through the liver, breaking up there into capillaries and forming the portal system of the liver. A short hepatic vein emerges from the liver and flows into the sinus venosus.
Excretory organs
The excretory organs of bony fish are similar to those of cartilaginous fish. The difference is that the excretory system in bony fish is not connected to the reproductive organs.
Long dark red trunk kidneys (mesonephric) lie on the sides of the spine above the swim bladder. The ureters are the Wolffian canals, which run along the inner edge of the kidneys. Bony fish have a developed bladder.
Reproductive organs
Unlike cartilaginous fish, female bony fish lack Müllerian canals. The thin membrane of the sac-shaped ovary continues into a narrow duct. A mature egg is thrown over it
out. In males, reproductive products are ejected through the vas deferens and their gonads are not connected to the Wolffian canals. Thus, the Wolffian channel performs only one function - the removal of metabolic products, i.e. ureter.
The separation of the reproductive and excretory systems of bony fishes is apparently due to the abundance of reproductive products.
Depending on the season and age of the fish, the degree of development of the reproductive organs may vary. In young specimens or in individuals caught outside the breeding season, the genitals are poorly developed. During the breeding season, the size of the gonads increases greatly.
central nervous system
Relative sizes brain in general, they increase in bony fish compared to cartilaginous fish (Fig. 29). However, the forebrain is relatively small. It is divided into two hemispheres by a longitudinal groove. The roof of the hemispheres does not contain nerve cells, it is epithelial. The main mass of the forebrain consists of the striatal bodies lying in its thickness. In front, the olfactory bulbs with olfactory nerves leading to the nasal capsules are visible. The cavities inside the hemispheres form two cerebral ventricles.
Diencephalon covered from above cerebral hemispheres and midbrain. The epiphysis (endocrine gland) is located on top of it, and the pituitary gland (endocrine gland) is adjacent to the bottom. Inside is the cavity of the third ventricle.
Midbrain in bony fishes it is noticeably larger than other sections. Two large optic lobes are visible from above. The cerebellum is also quite large, especially in active fish species. It significantly covers the medulla oblongata.
Medulla elongated and gradually passes into the spinal cord. A diamond-shaped pattern is visible from above
Rice. 29. Perch brain from above:
1 - nasal capsule; 2 - olfactory lobes of the forebrain; 3 - forebrain; 4 - midbrain; 5 - cerebellum; 6 - medulla oblongata; 7 - spinal cord; 8 - diamond-shaped fossa; 9 - olfactory nerves
the fossa is the fourth ventricle of the brain. When examining the brain from below, the forebrain with the olfactory lobes, a rounded outgrowth on diencephalon- the pituitary gland and in front of it - the optic chiasm (chiasm). From the brain of bony fish, like cartilaginous fish, 10 pairs of cranial nerves depart.
Spinal cord lies in the canal formed by the upper vertebral arches.
Goals:
- Educational: to reveal the features of the external and internal structure of fish in connection with life in the aquatic environment.
- Developmental: developing students’ ability to make observations, work with natural objects, and draw independent conclusions.
- Educating : to cultivate the student’s independence and self-esteem, to develop interest in the subject.
Principles: scientific, accessible, systemic and consistent, visual.
Means: tables, laboratory equipment, live aquarium fish, river perch (wet preparations), instruction cards.
- verbal - explanation with elements of conversation.
- visual – the use of visual aids.
- practical – performing laboratory work
Lesson type: practical work
Lesson Plan
1. Organizational point:
- greeting students
- preparing students for work in the lesson, communicating the topic of the lesson.
- target setting
2. Studying a new topic:
Teacher's opening speech
The start of this lesson will be a riddle, the answer to which will suggest the topic of our lesson:
It has wings, but it doesn’t fly,
no legs, but can’t catch up?
(Fish)
Fish are aquatic animals. The reservoirs in which fish live differ in the salinity of the water, its oxygen saturation, and temperature. Most fish species live in the seas. Some of them live in the water column (sharks, tuna, cod), others (skate, flounder) live in the bottom layers of the reservoir or at the bottom.
Fish from different habitats differ in shape, color and other characteristics. In addition, they have common features buildings. What is the external and internal structure of fish, we will find out using an example aquarium fish and river perch. To do this, we will conduct laboratory work.
Practical work in small groups.
The class is divided into two groups, each group works on completing a problem practical task, the results of which allow us to draw a conclusion about a certain property of a living organism. The results of student work are summarized at the end of the lesson and conclusions are drawn.
Tasks for group No. 1. External structure of fish
Purpose of the work: To find out the features of the external structure of fish in connection with the aquatic lifestyle.
Object of study: aquarium fish, river perch, tables, textbook drawings, instruction cards.
Instruction card
- Watch the fish swimming in the aquarium. Note what parts her body consists of.
- Examine the fish's head. What organs are visible on the head? How are the fish's eyes located?
- Examine the body of the fish. Determine what it is covered with; how the scales are arranged. Why do the scales have this arrangement?
- Look at the lateral line on the fish's body - a chain of tiny holes.
- Examine the fins of the fish. How many are there; where are they located? Determine which fins are paired and which are unpaired.
- Observe the work of the fins when the fish is motionless, turns, floats up, dives, and quickly moves forward.
- Fill the table:
- Note the role of fins for the life of fish in the aquatic environment.
- In your notebook, write down your conclusion about the adaptability of the external structure of the fish to life in water.
Assignment for group No. 2. Internal structure of fish.
Purpose of the work: To study the location of the organs of the body cavity and the main stages of development of bony fish.
Facilities and equipment; wet preparations “Internal structure of fish”, “Development of bony fish”; tables, textbook drawings, instruction cards.
Instruction card.
- Using wet preparations, find out which organs are located in the body cavity of a fish? What systems do these organs belong to?
- Consider the wet preparation “Internal structure of fish”. Find the swim bladder, gills, heart, intestines, kidneys, and liver on it. What systems do these organs belong to?
- What organs belong to the reproductive system of fish? Find the organs of the reproductive system on the wet preparation “Internal structure of fish”.
- Most bony fish are spawning fish. Examine the wet preparation “Development of bone fish” and find on it the main stages of fish development.
- Using the textbook pictures, find out what characterizes the main stages of fish development?
Present the results of your work in your notebooks in the form of a table.- Fish body cavity organs
- A kind of sensory organ.
- Filled with a mixture of gases.
- Front pair of limbs.
- Respiratory system.
- Vessels leaving the heart.
- Small holes.
Protective cover.
4 2 6 1 3 5 7 Answers:
- 4. Lesson summary:
- analysis of students' work by the teacher;
issuing and commenting on ratings. Homework:
pp. 176 – 179, assignment on p. 185.
Pisces are the first creatures with a developed spinal structure. During the process of evolution, these creatures underwent many changes that allowed them to adapt to the aquatic environment. The internal structure of the bony fish (female perch) may seem primitive in comparison with many vertebrates that live on land, but this is not true. The body of the perch is well adapted for life in the aquatic environment, so this fish is widespread in freshwater bodies around the world.
The anatomy of fish is often studied using these individuals as examples, since making a stuffed perch is not difficult. Perches are among the extremely bony fish; the fish has a developed musculoskeletal system. The spine of an adult fish consists of more than 30 vertebrae. They vary in size depending on location, but have a similar structure. The vertebral body has a slightly flattened shape. The upper and lower arcs extend from this element.
The upper arches close to form a special canal in which the spinal cord lies. The skeleton of a perch is mobile due to the fact that the bone elements are connected by cartilage tissue. The lateral processes of the vertebrae are quite rigid and serve as ribs that protect the internal organs from mechanical damage
. The external and internal structure of perches is due to the fact that they are aquatic animals; their bony structure allows them to move. The spine is crowned. It is represented by a vertical plate divided into 2 halves. The dorsal fin acts as a stabilizer. Thanks to it, the fish can make sharp turns. Besides, dorsal crowned with thorns that perform a protective function.
The number of unpaired fins on a perch reaches 3: 2 of them are located on the back, another 1 is located in the anus. The paired fins of river perch are both pectoral and ventral. These fins consist of 5-6 small bones. The limbs (the fin itself) are crowned with sharp protrusions.
The body of the fish is covered with small scales. She has gray-green color, color allows the perch to remain unnoticed in muddy water.
The perch skull is relatively different small in size. The bone elements of the skull protect the brain from mechanical damage. The main part of the skull is represented by the lower and upper jaws. There are gills on the sides of the head; there are few muscles in the head of the fish. On the side of the pharynx, bony gill arches cover the respiratory apparatus of the fish.
Considering the external structure of river perch, it should be noted that these fish are distinguished by well-developed muscles. The muscles are attached to the spine, gill processes and other bone elements of the musculoskeletal system, providing high speed movement. Perches have a well-developed swim bladder. This is a special organ located inside the fish, which is a bubble filled with a mixture of gases. This organ allows the fish to more easily control the depth of its dive, preventing it from sinking under the weight of its own body.
Digestive system
When considering the internal structure of river perch, you should first of all pay attention to digestive system this creation. It is represented by the following elements:
- oral cavity;
- pharynx;
- esophagus;
- stomach;
- intestines;
- pancreas;
- gallbladder.
There are many teeth on the upper and lower jaws of the fish. Food from the oral cavity enters the pharynx, then, thanks to muscle contractions, is pushed into the esophagus and stomach. Main body The digestion capacity of this fish is large. Here, under the influence of gastric juice, food undergoes primary processing. After this, the digested food enters the intestines, where it is released nutrients occurs under the influence of juices produced by the pancreas.
The digestion process also involves juices released from special glands located on the intestinal walls, and bile. The intestines absorb nutrients and water into the blood.
Respiratory
Hole respiratory system located in the pharynx area. Here the gills come to the surface, which are covered with bone plates. The bone plates move back due to the work of the muscles, providing an influx of oxygenated water to the gills. The respiratory apparatus is represented by 4 pairs of vertical rigid arches, to which many gill filaments are attached.
Inside the petals there are many small capillaries, which ensure gas exchange, i.e. oxygen from water enters the blood, and carbon dioxide is removed from the body. The gills on the side of the pharynx are equipped with special stamens that prevent the leaves from clogging with food particles.
Circulatory system
The circulatory system of perch is closed. Blood is pumped by the perch's two-chambered heart, consisting of a ventricle and an atrium. Blood circulation is continuous. Blood saturated with carbon dioxide is pumped through the heart.
Once the blood enters the gills, it is distributed through the capillaries, where it is saturated with oxygen. The blood is then redirected to the dorsal aorta. Thanks to this vessel, blood is delivered to all organs of the body, as well as the brain.
Excretory system
The genitourinary and excretory systems of fish are interconnected. Support normal chemical composition kidney blood. They are located along the spine. After this, waste products and excess salts are excreted through the ureters and bladder. Waste is removed from Bladder through a special hole.
The ovaries are located near the bladder. The eggs mature here during the breeding season. Females have a separate genital opening through which ripe eggs are released.
Nervous system of perch
The central nervous system of the perch is represented by the brain and spinal cord. The cranial nerves innervate the gills.
The spinal roots control the functioning of muscles and organs. They ensure the implementation of inherent reflexes and instincts.
Sense organs
The main sensory organ of the female perch is the eyes. The lens of the eye is different rounded shape. Thanks to the movement of the lens along the optical axis, the fish has the ability to see equidistant objects. The cornea is flat. This structure of the main elements of the eye provides the aquatic creature with good vision in water.
In addition, fish have well-developed olfactory organs. The nostrils are represented by inlet and outlet openings. Inside the nose there is an olfactory sac, in which there are many folds covered with olfactory epithelium.
The fish's hearing organ ensures the capture of sound vibrations.
It is believed that capture sound waves in water this creature occurs over the entire surface of its body. After this, the signals are transmitted to the auditory analyzer. The organ of hearing is combined with receptors responsible for balance.