Pisces class- This is the most numerous group of modern vertebrates, which unites more than 25 thousand species. Fish are inhabitants of the aquatic environment, they breathe with gills and move with the help of fins. Fish are common in different parts of the planet: from high-mountain reservoirs to ocean depths, from polar waters to equatorial ones. These animals inhabit the salty waters of the seas, are found in brackish lagoons and the mouths of large rivers. They live in fresh rivers, streams, lakes and swamps.

External structure of fish

The main elements of the external structure of the fish body are: head, gill cover, pectoral fin, pelvic fin, trunk, dorsal fins, lateral line, caudal fin, tail and anal fin, as can be seen in the figure below.

Internal structure of fish

Fish organ systems
	1. Skull (consists of the cerebral box, jaws, branchial arches and gill covers) 2. The skeleton of the trunk (consists of vertebrae with processes-arcs and ribs) 3. Skeleton of fins (paired - pectoral and abdominal, unpaired - dorsal, anal, caudal)	1. Brain protection, food capture, gill protection 2. Protection of internal organs 3. Movement, maintaining balance
Musculature	Wide muscle bands, divided into segments	Movement
Nervous system	1. Brain (sections - anterior, middle, oblong, cerebellum) 2. Spinal cord (along the spine)	1. Control of movements, unconditioned and conditioned reflexes 2. Implementation of the simplest reflexes, conduction of nerve impulses 3. Perception and conduct of signals
Sense organs	3. The organ of hearing 4. Tactile and taste cells (on the body) 5. Side line	2. Smell 4. Touch, taste 5. Feeling the direction and strength of the current, the depth of immersion
Digestive system	1. Digestive tract (mouth, pharynx, esophagus, stomach, intestines, anus) 2. Digestive glands (pancreas, liver)	1. Capturing, chopping, moving food 2.excretion of juices that facilitate the digestion of food
Swim bladder	Filled with a mixture of gases	Adjusts the immersion depth
Respiratory system	Branchial lobes and branchial arches	Carry out gas exchange
Circulatory system (closed)	Heart (bicameral) Arteries Capillaries	Supplying all body cells with oxygen and nutrients, removing decay products
Excretory system	Kidneys (two), ureters, bladder	Isolation of decay products
Breeding system	In females: two ovaries and oviducts; In males: testes (two) and vas deferens

The figure below shows the main systems of the internal structure of fish.

Pisces class classification

Currently living fish are divided into 2 main classes: cartilaginous fish and bony fish. Important distinguishing features cartilaginous fish- the presence of an internal cartilaginous skeleton, several pairs of gill slits that open outward, and the absence of a swim bladder. Almost all modern cartilaginous fish live in the seas. Among them, sharks and rays are the most common.

The overwhelming majority of modern fish belong to the class of bony fish. Members of this class have an ossified internal skeleton. A pair of external gill slits are covered with gill covers. Many bony fish have swim bladder.

The main orders of Pisces

Squads of fish	The main signs of the detachment	Representatives
	Cartilaginous skeleton, no swimming bladder, no gill covers; predators	Tiger shark, whale shark, katran
	Manta stingray
Sturgeon	Bone-cartilaginous skeleton, scales - five rows of large bone plates, between which there are small plates	Sturgeon, beluga, sterlet
Dipnoi	Have lungs and can breathe atmospheric air; notochord is preserved, no vertebral bodies	Australian horntooth, African flake
Kistepery	The skeleton is mainly composed of cartilage, there is a notochord; poorly developed swim bladder, fins in the form of fleshy outgrowths of the body	Latimeria (sole representative)
Carps	Mostly freshwater fish, there are no teeth on the jaws, but there are pharyngeal teeth for chopping food	Carp, crucian carp, roach, bream
Herring	Most are flock sea ​​fish	Herring, sardine, sprat
Cod	A distinctive feature is the presence of a mustache on the chin; most are cold-water marine fish	Haddock, herring, na-wag, burbot, tres

Ecological groups of fish

Depending on the habitat, ecological groups of fish are distinguished: freshwater, anadromous, brackish and marine.

Ecological groups of fish	The main signs
Freshwater fish	These fish constantly live in fresh water. Some, such as crucian carp and tench, prefer stagnant bodies of water. Others, such as gudgeon, grayling, chub, have adapted to life in the flowing waters of rivers.
Anadromous fish	This includes fish that move from sea water to fresh water for reproduction (for example, salmon and sturgeon) or from fresh water go to breed in salted (some types of eels)
Brackish fish	They inhabit freshened areas of the seas, the mouths of large rivers: such are many whitefish, roach, goby, river flounder.
Sea fish	They live in the salty water of the seas and oceans. The water column is inhabited by such fish as anchovy, mackerel, tuna. Stingray and flounder live at the bottom.

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Sourse of information: Biology in tables and diagrams. / Edition 2e, - SPb .: 2004.

"Commercial fish" - Groups of commercial fish. Order Salmoniformes. Salmon. Detachment Codfish. Carps. Cod-like. Detachment Carps. Sturgeon. Variety of commercial fish. Detachment Herring. Detachment Sturgeon. Herring.

"Fish Class" - The fish organism is complex. What kind of environment do fish live in? The value of fish. Internal structure body of fish. What groups is the vertebrate subtype divided into. Answer the test questions. What have we learned. The external structure of fish. The main organ systems of fish. Sense organs. Respiratory system. Habitat. What group of living organisms are we studying?

"Fish biology" - Aquaculture has two main directions. Biology and pathology of fish. The main production and technological processes in pond fish farming. The purpose of the discipline: And second - artificial reproduction of aquatic biological resources.

"Amazing Fish" - Biology Presentation On Topic: Amazing Fish. Angler. Whale shark. The angler is a predatory sea fish. There is no chin barb, and there is a dysfunctional gut. Wart venom is extremely dangerous. Sailboat. Fish-dragon. The idiakant, or "fish-dragon", is a long flexible fish. Armored pike. This fish lives at depths of 600-1200 m on the coast of Australia and Tasmania.

"A fish is an animal" - The instinct is prophetically blind. Detachments. The source of glue production. Make a crossword puzzle. Name the fish. Classes of fish. Variety of fish appearance. Scat. Number of species. Finish the proverbs. Choose the correct judgments from the proposed ones. Large aquarium. general characteristics class of fish. Pipefish. Classification of fish.

"Variety of fish" - Birds. Are growing. Flounder. Cockerel. Mystery. Fish is the moon. Omnivores. Skate. Predators. Fins. Are developing. For parents and children All clothes are made of coins. Catfish. Breathe. Marine. Fish is a hobbyhorse. Crucian carp. V - already knew + - learned new? - I want to know. Scales. 2 legs, feathers, wings, beak breathe lightly. Fish. Head. Animals.

There are 18 presentations in total

FISH class cartilaginous(Chondrichthyes) Class FISH cartilaginous (Chondrichthyes).

subclass. Platybranch fish (elasmobranchh) Sharks (selachomorpha) Superorder Skata (batomorpha) Superorder Solid skull or whole-headed fish (Holocephali) Subclass: Elasmobranchii - Platybranch fish. This is the order with the greatest diversity of species among sharks. Appeared during the Jurassic period, representatives are found from the intertidal zone to the ocean depths almost everywhere. Outwardly, distinguishing features are very variable, but all are characterized by the presence of five gill slits, two dorsal fins (except for the single fin cat shark), and an anal fin. Reproduction methods are also very diverse - there are oviparous, ovoviviparous and viviparous species. Some have oophagia. Multi-toothed. They appeared in the Triassic period, and represent a detachment of nocturnal bottom sharks. Their external features are a dense body, two spined dorsal fins, and an anal fin. Distributed from the intertidal zone to the continental shelf. All species are oviparous. Polygill-shaped. The detachment is the oldest among existing sharks - it was formed during the Permian period. Consists of two families, differing in body shape - eel-like in frilled sharks and "traditional" torpedo-shaped in multigill sharks. Both families have six or seven branchial slits, one dorsal fin, and an anal fin. Mostly distributed in the cool depths of the tropics, ovoviviparous. Lam-like. Appeared in the Jurassic period. This order is dominated by large pelagic species. They are torpedo-shaped, with five gill slits, two dorsal fins, and an anal fin. Distributed from the intertidal zone to deep waters ocean, ovoviviparous. Wobbegong-like. Appeared in the Jurassic period. Distributed in warm and tropical seas from intertidal to deep waters. With the exception of the whale shark, all species live on the bottom. They have five gill slits, two dorsal fins, and an anal fin. Among the species are oviparous, ovoviviparous and viviparous. Some also have oophagy.

Saw-shaped. Perhaps the most easily identifiable unit. It appeared in the Jurassic period. Sharks of this order are distinguished by a specific long, sawtooth muzzle, dotted with teeth, as well as the absence of an anal fin, two dorsal fins and large spiracles. They live at the bottom, ovoviviparous. Katraniform. Appeared in the Jurassic period. This order is widespread and found all over the world, including - the only shark - in latitudes close to the poles. They live at great depths. Representatives of the detachment have a torpedo-shaped body, five gill slits, two dorsal fins, and an anal fin is missing. Ovoviviparous.

Squat-like. Appeared in the Triassic period. The habitat is usually the silt or sand of the continental shelf and intertidal zone in cool temperatures, as well as deeper areas in tropical waters. Sharks of this order are distinguished by a wide flattened body, a short muzzle, five gill slits, large pectoral and pelvic fins, and the absence of an anal fin. Outwardly, they resemble stingrays, but the difference is that the gills open on the sides of the body, and not below, and wide pectoral fins are clearly visible, clearly separated from the head. All species are ovoviviparous. Order: Carcharhiniformes Compagno - Carchariniformes Order: Heterodontiformes Berg - Motley Order: Hexanchiformes Buen - Polygillipods Order: Lamniformes - Lam-shaped Order: Orectolobiformes Compagno-like Squid-like Squid-like Squid-like Squid-like

52 taxonomy of cartilaginous fishes, a variety of rays. Class FISH CARRYING (Chondrichthyes).

subclass. Elasmobranchh (Anacanthobatidae) Rhombic rays (Rajidae) Rhinidae Rhinobatidae (Rhinobatidae) Shark-tailed rays (Rhynchobatidae)

Representatives of this order have a strongly flattened rhomboid body; on the pelvic cartilages there are peculiar outgrowths and traces of gill folds in the squirt. In the skates of this order, tail spines are absent, and the caudal fin is greatly reduced. They are typically benthic. Also, some stingrays of this order have large spines along the middle of the body. The color of individuals depends on the color of the soil of the environment in which they live. Stingrays are predominantly nocturnal, and during the day they are not very active and burrow into the ground, leaving only their eyes on the surface. They predominantly live in coastal waters, although deep-sea rays also exist.

Today this order is the most numerous and includes about 200 species of rays. Distributed everywhere, however, the greatest diversity is reached in the polar regions and regions with a temperate climate. IN Russian waters the order is represented by only one family - the family of rhomboid rays (Rajidae). They feed on small fish and benthic invertebrates. Reproduction takes place by laying cornea-coated eggs.

53 question The main features of the organization. Cartilaginous fish, characteristics of lamellar and whole-headed fish. Lamellibranchian * (Lamellibranchiata) - a class of molluscs type. Characteristic P.: the body is usually quite symmetrical, almost always laterally compressed, laterally covered by two large mantle lobes, between which there is a large mantle cavity enclosing the lower body and leg of the animal, two gills attached to the sides of the body, and 2 pairs of triangular oral lobes; a shell of two lateral valves connected to each other at the dorsal margin and brought together by 1 or 2 muscles extending from one valve to the other; detached head, cephalic tentacles, pharynx, jaws and radula are absent; paired kidneys and gonads; a heart with 2 atria; dioecious or hermaphrodites, exclusively aquatic animals, freshwater and marine, mostly free, less often, in an adult state, attached. Despite the significant diversity in software appearance and structure, P. represent a very natural group, easily distinguishable from other representatives of the type of molluscs. In the vast majority of P., the body is quite pronounced two-sided symmetry; less often, symmetry is disturbed by the unequal development of the right and left halves due to the fact that an adult animal is either attached to underwater objects (usually grown) on one side (e.g., an oyster), or usually lies on one side (e.g., some species scallop - Pecten); at the same time, the valves differ in size, shape, thickness, color, sculpture, and internal organs also represent a more or less significant deviation from symmetry. The shell valves are for the most part large and can completely cover the body of the animal, but sometimes they are very small (for example, in a woodworm; see Molluscs, corresponding fig.). In addition to the shell valves, the mantle can secrete lime deposits in the form of additional plates or a layer lining the channels in which the mollusk (woodworm) lives, or in the form of a tube replacing the shell, while the minor valves of the latter merge with the tube (in Kropilets - see. , or water jug ​​- Aspergillum). On the dorsal edge of the valve, the so-called. a strand (ligamentum), which, when the muscles contract, that is, the shell is closed, is compressed, and when the muscles relax, it pushes the flaps. In addition to the strand, on the dorsal edge of the valves of some P. there is a lock - more or less developed protrusions and depressions of the inner surface of the valves, the location and shape of which are such that when the valves are closed, the protrusions of one enter the depressions of the other, facilitating the tight connection of the valves of the closed shell. On the inner surface of the valves, there is a line corresponding to the edge of the mantle and the attachment points of 1 or 2 strong muscles bringing the valves closer together. Adjacent valves are not always completely in contact: they often leave a more or less significant opening (gaping shells) open. Both lobes of the mantle can be completely free at the front, bottom and rear edges, or be spliced ​​together over a more or less significant extent in one, two, rarely three places. Due to the fusion or sometimes close adhesion of the mantle blades to each other in certain places, the entrance to the mantle cavity splits into 2-4 sections: through the rearmost one, the water that washed the gills is removed, together with feces and excretion products, through the next, water enters the mantle cavity, a leg extends through the front opening; behind the latter, there is occasionally another small hole, probably corresponding to the byssus, if there are only two holes, then water is discharged through the back, water is introduced through the front, and the leg with the byssus extends. The edge of the mantle can be simple or thickened with special sense organs (papillae, tentacles, eyes). The edges of both posterior openings are often lengthened, forming two tubular siphons: through one (lower) water enters (gill siphon), through the other (upper) it exits (anal siphon); siphons can be many times the length of the shell; sometimes they are more or less connected to each other (see. acc. Fig.) The body of the animal, devoid of a separate head section, ends from below in a muscular, more or less strongly developed, but sometimes rudimentary leg; most often the leg is conical or wedge-shaped, but in some P. of the most primitive structure, the leg is equipped with an extended flat sole (in Nucula, Leda, Yoldia). Many P. have a special gland in the leg that secretes dense filaments similar to horny ones - the so-called Byssus, with which the animal can temporarily attach itself to underwater objects. The order True lamellar-gill family includes more than one hundred families and is divided into four suborders: Split-toothed (Schizodonta), Multi-toothed (Heterodonta) - the largest in the number of families, genera and species, Adapedonta and Anomalodesmata. ) Possessing a number of unique features, representatives of this subclass of fish, in addition, in the most bizarre way combine the features of the plate-gill (Elasmobranchii) and bony fish (Osteichthyes). It is no coincidence that the great Linnaeus gave one of the genera the name "Chimera". With lamellar gills (selachia), they are, first of all, related by the presence of paired copulatory organs (pterygopodia) in males; the ability of females to lay large eggs enclosed in horny capsules; the presence in the external skeleton of placoid scales ("skin teeth") and the complete absence of ossification of the internal cartilaginous skeleton, some elements of which are sometimes strengthened due to calcification (should not be mixed with ossification). In addition, in the heart of modern fused cranials, as well as of lamellibranchs, there is an arterial cone, equipped with three rows of valves; a spiral valve passes through the intestine; large nostrils are brought close to the transverse mouth and communicate with its posterior corners with the help of furrows dissecting the upper lip; the outer lobes of the fins are supported by a large number of thin elastoidin filaments (elastotrichia), while in teleost fishes their homologous fin rays are replaced by bony rays (lepidotrichia); the fleshy lips are supported by labial cartilage, and, like the laminobranchs, the brain and heart are arranged, and the swim bladder is initially absent.

Question 54 General characteristics of the Bone class, the system up to subclasses. The bony fish class represents the largest superclass of fish. It includes about 20,000 species. This class is common in almost all water bodies of the surrounding world. The living conditions of bony fish are very diverse, which explains the richness of this group of species and their diversity. The Osteichtyes class consists of a wide variety of fish species. Their scales are ctenoid or cycloid, as well as serrated or smooth, depending on the shape. The class of bony fish is several times more diverse than the class of cartilaginous fish. The skeleton is predominantly bony. The appearance of the skeleton is possible in two main ways. The initial type of ossification is the integumentary or skin bones. Embryonic ossification occurs in the connective layer of the skin, regardless of the presence of cartilaginous components of the skeleton, since it is only attached to them. Based on the above features, the development of the integumentary bone often has the form of plates. In addition to the presence of integumentary bones, the skeleton of fish has cartilaginous or chondral bones. Their occurrence occurs in the embryonic period due to the replacement of cartilage with bone substance that produces osteoblasts. As chondral bones appear, the skeleton of fish gradually ossifies, which makes its own adjustments to the general structure of the skeleton. Due to the formation of integumentary ossifications, new elements of the skeleton appear, which significantly complicates its overall structure. There is a reduction in the intercostal septa of the respiratory apparatus. The gill petals are located directly outside the branchial apparatus. Most species of the bony fish class have a swim bladder. Almost all species of fish of this class reproduce by external fertilization. The laid eggs are small, without horn-like shells. A negligible number of bone-class fish species have live-born offspring. The classification of bony fish is so complex that at present there are several views on the taxonomy of this group. Subclass Ray-finned fish (Actinopterygii) Subclass Lobster-finned fish (Sarcopterygii).

55. Characteristics of the Blade: features of the organization, their origin and evolution.

Lobe-finned (lat. Sarcopterygii) or choanic - a class of bony fish. The axial skeleton is based on an elastic chord. Known from the early Devonian (300-400 million years ago), they combine both archaic and progressive features. The superorders are lung-finned and cross-finned superorders. Lobe-finned fish (in contrast to ray-finned fish) have moved to living in inland water bodies, their outgrowth of the esophagus turns into a lung, the leading analyzer is the sense of smell, and in comparison with other fish, the brain changes. The scales are cosmoid or bony. Throughout life, the notochord is preserved, surrounded by a dense connective tissue fibrous-elastic sheath. The upper and lower arches develop, and in the caudal region there are sometimes underdeveloped vertebral bodies (in some fossil groups they were better developed than in living species). The skull is amphilistic or autostylish. Scaly bone is present among the integumentary bones of the skull. The tail is heterocercal (fossil) or dificercal. Paired fins with a fleshy blade covered with scales at the base; their skeleton is of a bead type. There is a cone arterial in the heart. The intestine has a spiral valve and opens into the cloaca. As outgrowths of the ventral side of the initial part of the esophagus, one or two bubbles are formed, which perform the function of the lungs. Known from the Lower Devonian. Superorder cross-finned fishes (CROSSOPTER YGIMORPHA). The cerebral skull is divided into two parts - the olfactory and proper cerebral, movably connected to each other. The degree of ossification of the skull varies, integumentary ossification is developed. The skull is amphistilic; in some species, a transition to autostyly is planned. The secondary jaws are well developed, the teeth are strong and sharp. There may be vertebral bodies with a shortened central axis and a well-developed basal element at the base. They occur from the Lower Devonian in the form of several, already clearly limited groups. Freshwater predators that have repeatedly entered the seas.

1. Draw a table in a notebook and fill it out as you study the orders of bony fish

2. Remember the features of the structure of cartilaginous fish. What features of sturgeon fish emphasize their resemblance to cartilaginous fish?

The spine keeps the chord

3. Sturgeon fish are also called anadromous fish. Explain this variation of the name

They spend most of their life in salt water, climb into rivers for spawning

4. White Sea herring spawning in summer (“summer”) breed under conditions of significantly higher activity of predators than herring spawning in spring (“spring”). Scientists have found that herring of one of these groups spawn from 2.3 thousand to 21 thousand eggs, while others from 9.2 thousand to 62 thousand eggs. Determine the fertility of the "summer" and "spring" herrings. Argument your answer

In summer - from 9, 5 to 61 thousand calves

Spring - from 2 to 20 thousand calves

Yes, most salmon species can be considered anadromous

6. What are piranhas dangerous for animals and humans?

Piranha teeth allow large chunks of meat to be pulled out of the body of prey

7. Explain why one type of eel is called electric. Why does he need electrical discharges?

Electrical discharges are used to protect against enemies and to get food.

8. What feature in behavior and respiration of electric eels allows them to live in reservoirs with a minimum amount of oxygen?

There are areas of tissue that allow you to absorb oxygen

9. List the types of fish farmed in fish farms

Carp, tench, pike, walleye, saberfish

10. Name the species of fish of the order carp, bred in aquatic aquariums

Barbs, labeo, goldfish

11. How can one distinguish fish of the order perchiformes by the appearance of the structure?

The pelvic fins are located under the pectorals. The fin is shaped like an undivided sharp thorn

12. Complete the scheme "Squad Perch Families"

1.stone perch

2.perch with childbirth

3. horse mackerel

4.sea carp

5. rotosthenic

6. catfish

7.gobies

8.sailboats

13. Review figures 94 and 95 of the textbook (pages 111 and 112). Write down the species names of the fish of the Carp and Perch orders, which you caught in the rivers and lakes of your area

Order Carp: bream, carp

Perch-like order: perch, pike perch

14. Consider the pictures. Write down the numbers of the fish included in the corresponding units

Sturgeon squad: 6, 3

Herring Squad: 5, 7

Order Salmonidae: 10, 8

Carp squad: 2, 4

Percoid squad: 1, 9

15. Consider the pictures, sign the names of the fish

16. Why are the protoptera, lepidosiren, and cattle-toothed referred to as lungfish?

They breathe in water and on land

17. What do the habitats of lungfish living in Africa, America and Australia have in common?

They have a prototype of the lung, they can withstand the drying out of the reservoir

18. What changes in the fins of coelacanths make it possible to call them cross-finned fishes?

Paired fins serve for support, represent blades consisting of several brush-like segments

19. Remember the similarities between sharks and cross-finned fish

Two-chambered heart, live in water. axial skeleton in the form of a chord

20. Explain why lungfish and cross-finned fish can be considered transitional forms between aquatic and terrestrial animals

In the absence of water, they can switch to pulmonary respiration.

Fish are aquatic animals. In order to actively move in the aquatic environment, the body of the fish has a streamlined shape.

The body of fish can be divided into:

• head
• torso
• and tail

The border between the head and the body is the posterior edge of the operculums, and the border between the body and the tail is the anal fin.

Insert Flash

From above, the body of the fish is covered with skin, which consists of:

• corium or dermis
• and a multilayer epidermis (as in all vertebrates).

In the epidermis there are numerous mucous glands, on top of the epidermis in most fish is covered with scales.

The streamlined body shape, mucous glands and scales help the fish move quickly and easily in the water.

They move with the help of the bends of the body and with the help of paired pectoral and pelvic fins, which are mainly responsible for vertical movement, as well as an unpaired caudal fin, which acts as a rudder.

Also, the dorsal and anal fins, which stabilize the body of the fish in an upright position, are also unpaired fins in fish.

Fins:

• paired chest
• paired abdominal
• unpaired dorsal (1 or more)
• unpaired anal
• unpaired tail

Musculoskeletal system of fish

Insert Flash

Fish have a well-developed skeleton, which is divided into:

1.axial skeleton, which includes:

• spine,
• skull or head skeleton
• and ribs

2.skeleton of the limbs, which includes:

• skeleton of paired fins (free part and belts)
• and the skeleton of unpaired fins.

Fish skeleton - the picture shows the skeleton of a bony fish

The skeleton of fish consists of the skull, spine, ribs and the skeleton of paired and unpaired fins

In representatives of the class of Cartilaginous fish, the skeleton consists only of cartilaginous tissue. In representatives of the class Bony fish, both cartilaginous and bone tissue are present in the skeleton.

The spine performs supporting and protective functions - the spinal cord is protected by the arches of the vertebrae. The spine consists of two sections - the trunk and the caudal. The vertebrae of the trunk spine have lateral processes to which ribs are attached.

The skeleton of the head is represented by the cranium, to which the jaws and branchial arches are connected, and in bony fish, also the branchial covers. Cartilaginous fish have no gill covers.

The digestive system consists of the mouth, pharynx, esophagus, stomach and intestines, into which the ducts of the liver and gallbladder, as well as the pancreas, open. The intestine ends with the anal opening, which opens in front of the anal fin.

Only bony fish have a swim bladder

Fish have a swim bladder, which is an outgrowth of the intestinal tube. The swim bladder is filled with gases and can expand and contract. At the same time, the specific density of the body changes and the fish can move in the water column in the vertical direction. Only bony fish have a swim bladder, but cartilaginous ones do not.

Respiratory system of fish

Fish breathe with their gills

Respiration of fish is carried out with the help of gills. Water enters the mouth, then water from the pharynx passes through the gills into the external environment, while the blood vessels located in the gill lobes are saturated with oxygen.

Circulatory system of fish closed type

The circulatory system has one circle of blood circulation in all fish, except for lungs. There is a two-chambered heart, consisting of an atrium and a ventricle.

Insert Flash

The nervous system consists of:

• the central section, which is represented by the brain and spinal cord and
• the peripheral section, consisting of the cranial and spinal nerves.

The brain in fish, like in all vertebrates, consists of five sections.

The nervous system of fish consists of the head and spinal cord and the nerves extending from them

The olfactory lobes of the forebrain are well developed, since for fish it is very important role the organs of the chemical sense - smell and taste - play. The visual centers are located in the midbrain.

The cerebellum is also well developed, which is responsible for a variety of movements. There are lateral line organs that allow fish to determine the direction of water movement. There are organs of balance and hearing.

The excretory system of fish consists of the kidneys, ureters and bladder.

The excretory system is represented by paired ribbon-shaped kidneys, ureters and bladder, which opens with the urethra, which is located next to the anus.

The reproductive system of fish

Most fish are dioecious, males have two testes, and females have two ovaries. Females lay eggs (eggs) into the water, males - sperm. Fertilization takes place in the external environment.

Fish eggs - eggs

In many cartilaginous fish and in some bony fish, fertilization is internal; females give birth to fry.

Fish taxonomy

At the moment, about 30 thousand species of fish are known. The taxonomy of fish is quite complex, we will consider a somewhat simplified diagram. Currently, in various sources you can find different options taxonomy.

Classes cartilaginous and bony fish

The superclass of fish includes two classes - Cartilaginous fish and Bony fish.

The skeleton of cartilaginous fish, as the name suggests, consists only of cartilaginous tissue.

Cartilaginous fish include sharks, rays and chimera

To the class of Cartilaginous fish relate:

• detachment Sharkiformes,
• squad Skaty
• and the Chimera squad.

For cartilaginous fish, the following features are characteristic - they have no swim bladder, no gill covers.

Cartilaginous fish - sharks and rays

The order Bone fishes is the most numerous; it includes up to 96% of fish species.

Bony fish include the subclasses Ray-finned and Lobe-finned

CARILY FISH

Class Cartilaginous fish.A relatively small group of fish (about 730 species),whose skeleton remains cartilaginous for life. The body shape is often spindle-shaped.The class is called so because of the presence of a cartilaginous skeleton (Fig. 1), they do not have bone tissue. For example, a shark's jaw, like its skeleton, is also made of cartilage (Fig. 2).

Rice. 1. Cartilaginous skeleton (Source)

Rice. 2. Shark (Source)

The cartilage can be impregnated with calcium salts. Mobile no gill covers instead of them gill slits located on the abdominal part of the fish body or on the sides of the body (Fig. 3).

Rice. 3. An example of the gill slits of a whale shark (Source)

The swim bladder is missing. The skin is bare or covered with scales, which in structure and composition resemble teeth, they are called so - dermal teeth.

The class includes three squads: Sharks, Stingrays, Chimera(fig. 4).

Rice. 4. Units (Source)

Body shape: elongated torpedo body shape.

Length: from 20 cm to 20 m (fig. 5).

Leather: rough, covered with teeth and scales.

Fins: Paired pelvic and pectoral fins are horizontal, allowing the fish to move up or down. Forward movement and turns are provided by the bend of the tail or body.

Senses: eyes are located on the sides of the head, vision is black and white. They have a strong sense of smell, feel the slightest fluctuations in the water and so they learn about prey at a great distance.

Fertilization

Some sharks can attack humans. Most sharks are marine fish, but some also swim in fresh waters. One species lives permanently in the freshwater lake of Nicaragua (Fig. 6). Some species of shark are eaten by people, most often the Japanese, liver and fins are considered especially valuable. Leather is used in industry.

Rice. 5. Tiger shark (Source)

Rice. 6. Nicaraguan Freshwater Shark (Source)

Body shape: flattened in the dorsal-abdominal direction.

Fins: Widened pectoral fins on the sides, tail fin shaped like a long, thin whip.

Dimensions (edit): relatively large fish, some reach 6–7 m in width, weight can be in the region of 2.5 tons (Fig. 7). The smallest slopes can be about 12 cm in length.

Eyes and mouth: in benthic species, the eyes are located on the upper side of the head, in pelagic species, on the sides. The lateral mouth and gill slits are located on the ventral side of the body.

Leather: Naked or with dermal teeth, mucus secreting glandular cells.

Fertilization: internal, reproduce by viviparity or ovoviviparity.

Representatives of the species lead a benthic lifestyle, large stingrays can live in the water column. Most stingrays are marine, but there are freshwater species as well. Some small freshwater rays are kept in aquariums.

Rice. 7. Skat (Source)

Chimera are a small and peculiar group of deep-sea fish.

Body shape: there is a strong anterior section and gradually tapers towards the tail.

Length: from 60 cm to 2 m.

Fins: The caudal fin is thin and ends in a thin filamentous appendage.

Leather: naked and devoid of scales.

Fertilization: internal, reproduce by oviposition.

In total, about 30 species of chimera-like fish are known. The most studied European chimera inhabiting the Barents Sea at depths of more than 1000 m (Fig. 8). The Pacific and Atlantic oceans are inhabited by nosed chimeras (Fig. 9).

Rice. 8. European Chimera (Source)

Rice. 9. Nosed Chimera (Source)

BONE FISH

Class Bony fishincludes the overwhelming majority of representatives of the Fishes superclass (about 20 thousand species) inhabiting fresh and salt water bodies.Its name of the class speaks of the presence of a bony skeleton, the body is covered with bone scales or plates, there are no dermal teeth, unlike cartilaginous fish, the gill cavity is covered with gill covers, which are mobile, there is a swim bladder, which can disappear in bottom and sedentary forms (Fig. one).

Rice. 1. Signs of bony fish

It is in bony fish that true lungs appear for the first time in evolution. Fish that have both gills and lungs are called lungs. Most of this once huge group became extinct in the Triassic, but there are several modern groups of lungworms (Fig. 2).

Rice. 2. Australian horntooth

In total, there are about 20 thousand species of bony fish, although this is not often talked about, but bony fish are the most numerous class of vertebrates. The peculiarities of the ecology, structure and physiology of certain species make it possible to divide all this enormous diversity into several tens of groups.

We will discuss only 6 of the most significant of them: Sturgeon-like, Herring-like, Salmon-like, Carp-like, Perch-like, Coelacanth-like.

The sturgeon is a small group that has retained a number of ancient features that emphasize their resemblance to cartilaginous fish. So, in these fish, the notochord is preserved throughout their life, and the skeleton is bone-cartilaginous. The body is elongated; the head begins with a flattened snout (Fig. 3).

Rice. 3. Sturgeon

Representatives of the sturgeon family are found mainly in the temperate latitudes of the Northern Hemisphere. Adult fish spend their entire life in the sea, and enter rivers only for spawning, however, there are also completely freshwater forms.

Most sturgeon feeds on aquatic invertebrates; some species feed on small or even large fish.

Meat and especially sturgeon caviar are extremely highly valued as delicacies (Fig. 4). Because of this, sturgeons have always been poached. The construction of hydroelectric power plants has led to the almost complete extinction of sturgeons in many rivers.

The point is that adult fish cannot climb up the river through the dam (Fig. 5).

Rice. 4. Black caviar of sturgeon

Rice. 5. Hydroelectric power plant

The order includes fish with an elongated body, slightly compressed from the sides (Fig. 6). Paired and non-paired fins are soft; the lateral line is usually not visible. The body length of the herring is usually 5 to 75 centimeters.

Rice. 6. Herring

Most of herring fish are marine fish, however, there are also anadromous species, and some representatives have mastered fresh water bodies too. The most famous of the detachment is the Herring family. These are small and medium sized marine fish. Herring, sardine and sprat are of great commercial importance (Fig. 7).

Rice. 7. Commercial value of herring

Includes fish similar to herring, with a length of 2.5 cm to 1.5 m (Fig. 8). Most members of the salmon family are anadromous fish, but there are freshwater forms as well.

Rice. 8. Salmonids

Often, when entering rivers, salmon have a bright mating outfit (Fig. 9). At this time, salmon do not feed, and only exist thanks to the supply of nutrients accumulated in the sea. After spawning, fish often die.

Rice. 9. Mating dress of salmon

All salmon are commercial fish highly valued for their delicious meat and caviar. Many salmon are bred in special fish farms. It should be remembered that the diversity of the order Salmonidae is by no means limited to the Salmonidae family (Fig. 10).

Rice. 10. Fishing for salmon

Representatives of this order are very similar to herring, but differ from them in a peculiar structure of the spine. The number of species of this order is about 15 percent of the total diversity of bony fish (Fig. 11).

Rice. 11. Carps

Among carps, there are both herbivorous and omnivorous and even predatory fish. Predatory fish include, for example, piranha and electric eel (Fig. 12).

Rice. 12. Piranha and the Electric Eel

The commercial value of carps is enormous; a number of species are artificially bred in pond farms (Fig. 13).

Rice. 13. Fish farms

The most famous decorative pond fish is the koi carp (Fig. 14). Some tropical carps with beautiful and bright colors have become objects for keeping in aquariums.

Rice. 14. Japanese koi carp

Perchiformes are the most numerous group of fish in terms of species composition. It includes more than 9 thousand species (Fig. 15).

Rice. 15. Perchiformes

Perchiformes are widespread in reservoirs of all continents, in all seas and oceans. Body length - from 1 cm to 5 meters. Weight - from fractions of a gram to a ton or more. For example, a moonfish can be up to 3 meters long and weigh up to one and a half tons (Fig. 16).

Rice. 16. Moonfish

A characteristic feature of the entire order is the presence of 2 dorsal fins with sharp spines. The most famous family of rock perches, perch proper, horse mackerel, catfish, gobies and sailfish.

Obviously, many members of the order are eaten. Small perches are often a favorite of aquarists.

The coelacanths are a very small but very important order of bony fish. In the modern fauna, they are represented by only two species. These last representatives of cross-finned fishes may well be called living fossils (Fig. 17). The fact is that once the first amphibians originated from such fish.

Rice. 17. Celacanthus

Modern lungs

By origin, lungs are a very ancient group of fish that appeared in the Devonian period. Only 2 families with 6 species have survived to this day.

Lungs have both a number of primitive features and a number of features that unite them with amphibians, the most important such feature is, of course, the presence of lungs. The genus Protopter is the best known of the modern lung-breathing species (Fig. 18).

Rice. 18. Protopter

Protopters live in the temporary drying up water bodies of Africa. Remarkable is the ability of these fish, falling into suspended animation and losing a lot of water, to survive the drying out of the reservoir.

Electric eel

A remarkable representative of the carp order is the electric eel, by the way, the electric eel has nothing to do with real eels, it is not a relative of them.

Electric eels live in oxygen-depleted water bodies. Electric eels have acquired the ability to use oxygen in the air, for this the fish rises to the surface of the water and captures air by mouth.

An electric eel is capable of producing a discharge of up to 350 volts, so these fish are protected or hunted by electricity (Fig. 19).

Rice. 19. Electric eel

The amazing story of coelacanth

Fossil remains of coelacanth fish have been known since the Devonian period. After the Cretaceous period, no trace of this group was found and it was considered completely extinct.

Rice. 20. Coelacanth

And suddenly the fish caught in 1938 turns out to be a real living celacanth (Fig. 20). The discovery of such a living fossil was, of course, a sensation. The fish was named coelacanth. Imagine: a live fish was found, all of whose relatives became extinct back in the era of the dinosaurs.