5 7 open gill slits. Cartilaginous fish class

Publication date: 24.10.2015

Short description:

material preview

Mari El Republic

Gornomariysky municipal district

Abstract open lesson biology

in 7th grade on the topic:

"Cartilaginous fish"

Fulfilledand the teacher

biology and chemistry

MBOU "Oktyabrskaya OOSh"

Yakimova L.V.

November 2015

Equipment:

tables "Diversity of fish"; "Sea fish"

poster-booklet "Pisces";

physical map

encyclopedia for children

book "Life of animals vol. 4 Pisces"

Goals: introduce students to common characteristic class cartilaginous fish, with their diversity and significance, with the characteristics of the orders of sharks, rays, chimeras.

Lesson objectives:

To study the internal and external structure of cartilaginous fish.

To expand students' knowledge about the diversity, systematics and classification of representatives of the Cartilaginous fish class.

Introduce the meaning of the class Cartilaginous fish.

Continue to form a feeling careful attitude to nature.

Develop skills and abilities to work with additional

literature and create presentations

DURING THE CLASSES

1. Organizational moment. (1-2 min)

Preparatory stage:

A table is drawn on the board: "Squads of Cartilaginous Fishes." Tables are hanging: “The structure of fish”, “Variety of fish”, “Inhabitants of the sea”. Physical Map. The “Systematics of Fish” schemes, reference signals, blank sheets are laid out on the desks.

Hello guys! Sit down! Today in the lesson we will continue our acquaintance with representatives of the class of fish, with the variety of their features, and at the same time we will find out what types of fish are found in our reservoirs and are subject to protection.

1. Survey of students on previously studied material. (10 min).

But first, let's recall the characteristic features of the class of fish. On your desks are reference signals that will help you compose answers.

Frontal survey on the topic of fish breeding.

Who are fish and where do they live?

What body shape do they have?

What is their body covered with?

Why do fish have fins?

What do they need a swim bladder for?

What sensory organs do fish have?

What is a lateral line?

What is the meaning of fish?

Evaluation of student responses.

Generalization: fish are vertebrates that live in water. The conditions of their habitat, food composition, competitors and enemies are different everywhere, and a great variety in the structure and behavior of fish depends on this. In total, 20 thousand species of animals belong to the class of fish.

3. Learning new material.

History reference. Working with the map

What is the purpose of today's lesson? Children provide answers.

Correctly. - To get acquainted with the signs of representatives of the class Cartilaginous fish.

Working with the class.2) What is the relationship between appearance and depth of habitat in fish?

(Answer: fish moving in the water column usually have a spindle-shaped, well-streamlined body. Fish that live at great depths have a ribbon-like body shape. (saber fish). Bottom fish may have a flat, disc-shaped body; cylindrical serpentine blackhead body allows them to quickly crawl along the bottom. The inhabitants of the upper layers of the water 4) often have a dark back, silvery sides and belly.)

3) Question-judgment.

Why has the study of the living world always been one of the important aspects of human activity?

Suggested answer. For primitive people, life depended on it. Man needed to know which organisms could be used for food, clothing, protection, or housing, and which were dangerous or poisonous. Unfortunately, now we are studying them in order to protect them.

Slide 1 Introductory word of the teacher: The body of sharks is fusiform, they have a strong tail with a very elongated upper fin lobe. In most species, the head protrudes forward in the form of a pointed snout, and a wide mouth is located on the underside in the form of a transverse slit. There are no gill covers. On the sides of the head are a series of gill slits. Deeper, in special bags, gills sit. The skin is studded with special scales in the form of small, hard, bone-like grains, sometimes with spikes or teeth that make it rough. in the mouth sharp teeth sit in several rows. Triangular teeth are arranged in 5-6 or even 15 rows. The total number of teeth reaches several hundred, and each is sharper than a razor. The back teeth replace the front teeth as they wear out, like cartridges in a revolver. A shark can shed up to 24,000 teeth in 10 years. The skeleton is cartilaginous, the remnants of the notochord are preserved inside the spine. The swim bladder is missing. Only polar shark eggs look like caviar. For most of the rest, these are large eggs containing a large amount of yolk and dressed in a strong horny shell. The egg looks like an elongated quadrangular pillow, from the corners of which long twisted bundles extend; with them, the egg is fixed to the algae and hangs on them in this form until a relatively large cub hatches from it. Fertilization is internal.

Slide 2Class Cartilaginous fish(630 species) Appeared about 300 million years ago.(notebook entry)

Shark squad (250 species)

Order Stingrays (350 species)

Order Chimera (30 species)

Features of the structure of cartilaginous fish:

Cartilaginous skeleton (often mineralized)

Mouth - on the underside

Paired fins arranged horizontally

The muzzle is extended - rostrum

Gill covers missing

Gills open to the outside with independent openings

Usually 5-7 pairs of gill slits

no swim bladder

Internal fertilization

Question-judgment.

How can we determine if animals need protection, are they successful?

Suggested answer. In the world of wildlife, it is very easy to find out the success of organisms - alive means successful.

In the process of work, the table "Squads of Cartilaginous Fish" is filled in.

"Squads of Cartilaginous Fishes".

Order name, number of species.

Squad signs.

Habitats.

Squad representatives.

1. Sharks (250)

The body is elongated, torpedo-shaped, the skin is rough, there are 5-7 gill slits, there is no swim bladder, vision is poor, they lead an active lifestyle.

Seas and oceans.

Tiger shark, hammerhead shark, white shark.

2. Skates (350)

The body is flattened, diamond-shaped, the pectoral fins are fused, the caudal fin is in the form of a whip, there are no gills, there is no swim bladder.

Seas and oceans.

Manta, stingray, spotted bracken.

3. Chimera (30)

The anterior section of the body is developed, the caudal section ends with a filiform appendage, the skin is smooth, there are no gills, there is no swim bladder.

Seas and oceans.

European chimera, nosy chimera.

The table is filled in together with the students. In the process of filling - work with the textbook.

Independent work on filling out the table (order Chimera).

Slide 3. Shark Squad.

A) Features of the external structure:

Heterocercal (unequal) tail

The skin is covered with placoid scales, consists of dentin covered with enamel

(there is a tooth on the surface)

Scales cover the entire body and go along the edges of the oral fissure on the jaw (performs the function of teeth) - Shagreen leather

Shark teeth are homologous to placoid scales

Teeth grow and change throughout life. Each tooth lasts 8-10 days.

On the retina of the eye - pigment cells - The eyes of sharks glow in the dark

Shark eyelids close up

B) Features of the internal structure of sharks: When a fish swims, water enters its mouth and a respiratory process occurs, similar to the respiratory process of people. The respiration of fish is basically no different from the respiration of other vertebrates: the blood absorbs oxygen and releases carbon dioxide. We extract oxygen from the atmosphere, fish extract it from the air in the water. In the gill slits are gill filaments, densely permeated with blood vessels.

When the shark opens its mouth to take in water, the gaps close. Water bathes the gill filaments, carbon dioxide is released from the blood, and the oxygen in the water is absorbed by it. In addition to gill slits - usually there are five to seven pairs of them - sharks have another respiratory organ - a spray. It is believed that the function of the splashes, located, as a rule, above the shark's eyes, is to additionally oxygenate the blood vessels of the brain and visual apparatus.

Writing in a notebook

Slide 4 Features of the internal structure of sharks:

The swim bladder is absent, its functions are partially performed by a large

three-lobed liver, which contains dozens of times vitamin A

more than cod liver.

The blood is saturated with urea to maintain osmotic pressure.

The intestine is very short. The spiral valve greatly increases

intestinal area. Spiral shark stool

Dioecious fish

Fertilization is internal

The genital ducts empty into the cloaca

oviparous, ovoviviparous, viviparous

The sense organs are well developed.

AT) Shark sense organs.

The shark sees the world in black and white.

Enough "tight in the ear".

But she has a very subtle sense of smell.

A well-developed lateral line, which gives it a "sixth sense" that allows it to pick up the smallest vibrations in the water.

Thanks to the organs of the lateral line, the shark can feel the movement big fish at distances up to 300 meters.

On top of that, the shark has another organ on its head - the so-called Lorenzini cells, with the help of which it senses changes in pressure, electromagnetic permeability and temperature.

Slide 5-11

D) Representatives of the Shark order: Carcharadon (Great White); Mako (Grey-blue); whale; Brindle; Katran (Prickly); Hammerhead shark; Sea fox.

Student messages.

Slide 12 4. Stingray squad. Structural features

In stingrays, like in sharks, a cartilaginous skeleton, a transverse mouth on the underside of the head, and gill slits do not have covers. Their body is flat, flattened from top to bottom, has the shape of a rhombic, then a rounded shield. It seems even wider due to the pectoral fins - they stretch along the sides of the body and at the base of the tail pass into the ventral fins. The upper side of the body corresponds in color to the soil, the lower -

pale. Unlike sharks, stingrays move slowly, undulating their body along with wide fins, like a cloak fluttering in the wind. Some stingrays have peculiar defense tools. So, at the base of the tail in place of the dorsal fin, the sea cat has a jagged spike that secretes poisonous mucus. In an electric stingray, an electric organ is capable of delivering discharges of up to 80 V. The method of reproduction is like that of sharks, only they immerse their eggs in the sand. The gill slits are located on the ventral side, so they draw water for breathing through the spray, so as not to clog the gills with sand. Some rays live in the water column, feeding on small fish. These are eagle rays, mobuls and manti (sea devils). Mantas are the largest rays, the width of the disk reaches 6.6 m, and the mass is 2 tons. Mantas give birth to large cubs, which the mother feeds with nutritious

liquid. Rays live at the bottom of the seas, have a rounded body, but do not have placoid scales and spines. Eagle rays swim well and feed not only on bottom animals, but also on pelagic ones. The electric organs of stingrays are located on the sides of the head. The voltage during discharge can reach 60-300 volts at a current strength of up to 5 amperes. Skates are ovoviviparous or viviparous. Giant manta (or sea ​​Devil) reaches a diameter of 7 m and a mass of 2 tons. The meat of sharks and rays is quite edible. Sharks serve as an object of fishing, the skin of large species is used in leather production. Technical fish oil is obtained from the liver of sharks.

Writing in a notebook: 1) Features of the structure of the slopes.

Eyes on top of head

Tail in the form of a thin whip

Many have thorns

Mouth and gill slits are located on the ventral side

bottom fish

(Student messages)

Slides13

2) Representatives of the Stingrays squad: Manta; Stingray (monkfish); Sawmill; Spotted bracken; common electric ray

Slide 14 . 5. Chimera Squad - A poorly studied group of fish. They are also cartilaginous fish, but they do not have a cloaca and spiracles, the gill slits are covered, like in higher fish, with a cover - an outgrowth of the skin, the upper jaw fuses with the brain case. They feed on mollusks, chewing them with flattened teeth.

Features of animals of the order Chimeras

Has a gill cover

Cloaca and spritz are missing

The upper jaw fuses with the braincase

III. Generalization, conclusion:

Representatives of the class Cartilaginous fish live in the seas and oceans, have a diverse body shape, a cartilaginous skeleton, 5 - 7 gill slits, they do not have a swim bladder (notebook entries).

Question-judgment.

How can we concretize the meaning of biological knowledge in modern society And personally for you, students? What will change if you have this knowledge?

Suggested answer.

On the present stage- basis for bionics, cybernetics; preservation of the integrity of the biosphere.

Writing in notebooks Meaning of Cartilaginous Fish:

Link in the food chain
- eating (shark fins, liver - vitamin A, shark eggs)
- shark skin products (handbags, expensive shoes, wallets)
- aesthetic
- danger to humans

Tanned leather - shagreen leather, leather like sandpaper.

Make files

Student message.

IV. Summing up the lesson

V. Consolidation of the studied.

Reflection.

What moments of the lesson do you remember the most?

1) What is the structure of a shark?

2) How is a stingray different from a shark and what does it have in common with it?

3) Are all sharks dangerous to humans?

4) How will you behave in the aquatic environment (in a reservoir - a lake, in a river) so as not to drown?

Suggested Answer

Like stingrays - lie horizontally on the water, the water will push us out;

Like sharks - move.

Slide 15 Let's make a syncwine by squads.

1 concept (one word) - sharks

2 adjective 2 words - torpedo-shaped, dangerous

3. verb - devour, swim, attack.

4. sentence (of 4 words) sharks often attack people.

5. noun (one word) - predators.

front poll.
1) What cartilaginous fish do you know?
2) What features unite sharks, rays, chimeras? ,
3) How do cartilaginous fish reproduce?
2. Individual survey.
CARD #1
What kind of fish has skin so rough that you can make files out of it?
(Answer: from the skin of sharks, the inhabitants of the islands Pacific Ocean they make files that can be used to polish wood and even marble.)
CARD #3
How often do sharks and rays breed, and how big are their offspring?
(Answer: most of these fish breed once a year, and large species- less often. The polar shark, whose length is 8 m, lays 500 medium-sized eggs. The most numerous offspring bear Tiger shark- 80 cubs, and the hammerhead shark - 40 sharks

cartilaginous- the skeleton is cartilaginous, the skin is covered with scales in structure resembling teeth. There are no gill covers; the gill slits open outwards on their own.

holes, no swim bladder.

Sharks are an elongated torpedo-shaped body, up to 20 m. They feed on fish and garbage.

Stingrays - the body is flattened in the dorsal-abdominal direction, bottom, gill slits on the ventral side. Manti - the largest slopes, width - 7 m, weight - 2 tons.

Generalization, conclusion: representatives of the class Cartilaginous and bony fish live in the seas and oceans, have a diverse body shape, a cartilaginous skeleton, 5 - 7 gill slits, they do not have a swim bladder (entries in notebooks).

Homework:

Study from 182-183 textbook.

Answer questions No. 9, 10, 12 (y); With. 184; dictionary work p.185 (y).

Sinkwine by stingrays and chimeras.

Literature

Lesson according to the program developed by a team of authors under the guidance of V.V. Latyushin V.A. Shapkin.2001.

Encyclopedia for children. M. "Avanta +" 1994.

"Life of animals vol. 4 Pisces"

TESTING

MATERIAL AND EQUIPMENT

For two to four students, the following is required: 1. A set of material for identification (representatives of various groups of cyclostomes and fish fixed in alcohol). 2. Enamel bath. 3. Dissecting needles - 2. 4. Tweezers. 5. Loupe 4 - 6 x.

EXERCISE

1. Determine sequentially the class, subclass, superorder and order to which the given animal belongs. Draw the contour of his body, marking with arrows the "key" signs of the detachment to which the individual being determined belongs. 2. Disassemble the available collection material according to life forms (bottom and pelagic, predators and “peaceful” fish, etc.). Pay attention to the similarities and differences among representatives of different groups similar in lifestyle. 3. At the instruction of the teacher, identify some animals to the species, using special determinants for this.

TABLE FOR DEFINITION OF CLASSES

1(2). There are no paired limbs. Jaws are absent; mouth in the form of a suction funnel. One unpaired nostril. Caudal fin protocercal

Class Cyclostomes, Cyclostomata

2(1). There are paired limbs. The mouth is equipped with movable jaws not in the form of a funnel. Nostrils paired; the opening of each of them can be subdivided into two parts. The caudal fin is not protocercal.

3(4). Gill openings open outwards in the form of slits in the amount of 5-7 pairs

Class Cartilaginous fish, Chondrichthyes(subclass Elastobranchial, Elasmobranchii)

4(3). The gill slits are covered by the gill cover and open outwards with one common opening behind its posterior edge.

5(6). Gill cover in the form of a skin fold without a bone skeleton

Class Cartilaginous fish, Chondrichhtyes(subclass Chimera, or Whole-headed, Holocephali)

6(5). Gill cover bone

Class Bony fish, Osteichthyes(subclass Ray-finned, Actinopterygii).

CLASS CYCLOSTOMATA

TABLE FOR DEFINITION OF SUBCLASS

1(2). External gill openings 7 pairs. There are clearly visible eyes located under the skin. Nostril on top of head between eyes

Subclass Lamprey, Petromyzones

Within the subclass, the only order is Petromyzoniformes with one family, Petromyzonidae. The distribution is wide: the Atlantic Ocean, the rivers of Europe, Northern and East Asia, as well as the Southern Hemisphere (the coasts of Australia, Tasmania, in South America - Chile, New Zealand). Most species live in the seas, but enter rivers for spawning; there are also non-migratory freshwater forms. Many lamprey species are of commercial importance. 2(1). External gill openings, one on each side of the body. The eyes are reduced (not visible). The nostril is located at the anterior end of the head, directly above the suction funnel.

Subclass of Mixins, Myxini

In the subclass, the only detachment of Myxiniformes is represented in the fauna of the USSR by one species - Myxina glutinosa L. European and American coasts of the Atlantic Ocean, rare in the waters of the USSR. They have no commercial value.

CLASS CARTILAGE FISH, CHONDRICHTHYES

SUBCLASS PLASTINOGRANCH,ELASMOBRANCHII

1(2). The body is more or less rounded in cross section. The anterior edge of the pectoral fins is not fused with the sides of the body and with the head. External gill openings are located on the sides of the head

Superorder Selyahoidnye, or Sharks, Selachomorpha

2(1). The body is strongly flattened in the dorsal-abdominal direction. The anterior edge of the pectoral fins is fused with the sides of the body and the head. External gill openings are located on the ventral side

Superorder Batoid, or Stingrays, Batomorpha

There are several orders in the superorder of stingrays. In the fauna of the USSR (Black, White, Barents and Far Eastern seas), representatives of the orders diamond-shapedstingrays, Rajiformes (tail ends with a small tail fin) and eagle-like, or caudate-shaped, Myliobatiformes (gradually thinning caudal peduncle does not carry a caudal fin; in some species, there is one (rarely two) long and sharp serrated horn needle in the middle of the caudal peduncle).

SUPERORDER SHARKS, SELACHOMORPHA

1(2). External gill openings 6 pairs

Order Frilled sharks. Chlamydoselachiformes

In the fauna of the USSR (Barents Sea) there is the only representative of this detachment of primitive sharks - frilled shark, Chlamidoselachus anguineus Grm. (family Chlamidoselachidae). 2(1). External gill openings 5 ​​pairs

3(4). Anal fin present

Order Lamniformes, or Herring sharks, Lamniformes

There are 6 families in the detachment: herring sharks, Laminoididae (northern parts of the Atlantic and Pacific Oceans), blue sharks, Carcharinidae, etc. 4(3). No anal fin

Squad Catranoid, or Spiny Sharks, Squaliformes

This includes families: spiny sharks Squalidae (in the waters of the USSR, the only species is Squalus acanthias L.) and polar sharks Scymnidae (there is also only one species in the waters of the USSR).

CLASS BONE FISH, OSTEICHTHYES

SUBCLASS RAY-FINISHED, ACTINOPTERYGII

TABLE FOR DETERMINING SUDO-ORDERS

1(2). The tail is heterocercal. The mouth is in the form of a transverse slit, located on the ventral side behind a more or less elongated snout. On the dorsal side and on the sides of the body there are large relief bone plates - "bugs", located in five regular longitudinal rows

Superorder Ganoid, Ganoidomorpha (Cartilaginous ganoids)

In the fauna of the USSR, the only detachment - sturgeons, Acipenseriformes with one family sturgeons, Acipenseridae. Representatives of this family are anadromous or freshwater fish. Distributed in Europe, North Asia and North America. In the USSR, representatives of sturgeons - Russian sturgeon, stellate sturgeon, sterlet, beluga and others - are of great commercial importance. 2(1). The tail is homocercal. Mouth at the anterior end of the head (no snout). There are no bone "bugs" - the body is covered with rounded thin bone scales or naked

Superorder group of bony fishes, Teleostei.

SUPERORDER GROUP OF BONEY FISHES, TELEOSTEI

TABLE FOR DEFINITION OF UNITS

1(2). Both eyes are on the same (left or right) side of the head. The skull is asymmetrical. Body sharply flattened laterally

Order Flatfish, Pleuronectiformes

The most widespread members of the families flatfish, Pleuronectidae and diamonds, Bothidae - inhabitants of coastal areas of the sea. Representatives of the third family are found in the Black Sea and in the Far Eastern seas - maritime languages Soleidae. All these fish are of commercial importance. 2(1). The skull is symmetrical. The eyes are located on both sides of the head

3(4). The pectoral fins have a fleshy base, which gives them an external resemblance to the paws of terrestrial vertebrates. The body is slightly flattened in the dorsal-abdominal direction. The anterior ray of the dorsal fin is greatly elongated (an organ for attracting prey)

Order Angler-shaped, or leg-finned, Lophiiformes

Coastal or bathypelagic fish of tropical, warm and temperate seas. A peculiar feature is the transformation of the anterior ray of the dorsal fin into a long flexible outgrowth - a "bait" that attracts smaller fish to the predator. In the USSR (the Black Sea, less often the Barents Sea and Far Eastern waters), there are representatives of one of the families of this order - the family sea ​​devils, Lophiidae. They have no commercial value. 4(3). Pectoral fins are normal. The dorsal fin does not have a strongly elongated ray

5(12). No pelvic fins

6(7). The body is covered with bony shields. A small mouth is placed at the end of a long snout extended into a tube. no teeth

Suborder Needle-shaped, SyngnathoideiOrder of the Sticklebacks, Gasterosteiformes

Mostly marine (as a rare exception - freshwater) forms. They live in coastal (rarely pelagic) biotopes, mainly among thickets. In the USSR - 2 families: marine needles, Syngnathidae and Sea Horses, Hippocampidae. Distributed in the Baltic, Black, Azov Seas and in some bays of Primorye. Representatives of the suborder have no commercial value. 7(6). There are no bony scutes (the body is covered with ordinary scales or naked). There is no snout extended into the tube

8(9). Body strongly elongated, serpentine

Order Eels, Anguilliformes

Family river eels, Anguillidae is characterized by features of the life cycle: adult eels live in rivers (mainly in the basins of the Black and Baltic Seas), but for reproduction they migrate to the Atlantic Ocean - to the Sargasso Sea region. The larvae hatched from the eggs are passively transported by sea currents to the shores of Europe; during this migration, the larvae develop into adult eels that actively enter rivers. Members of another family conger eels, Congridae are distributed in the North Atlantic, Baltic and Black Seas. Third family - deep sea eels, Synaphobranchidae is distributed in the North Pacific. River eels are of commercial importance. 9(8). Body is not serpentine

see 10

10(11). The body is short. The mouth is beak-shaped. The jaws are subdivided by a vertical groove, forming 4 large "teeth"

Order Pufferfishes (Ostomaxillary), Tetrodontiformes

Of the 7 families in the fauna of the USSR 4: moons are fish, Molidae; triggerfish, Balistidae; hedgehog fish, Diodontidae and fakhaki, Tetrodontidae. Found in the seas of the Far East ( triggerfish also in the Black Sea). They have no commercial value. 11(10). The mouth is not coracoid. Regular shaped teeth

Order Perciformes (Prickly-finned), Perciformes

There are up to 20 suborders in the detachment, 7 in the fauna of the USSR, some of them with several families. Suborder perciform, Percoidei includes 13 families, some of which are of significant commercial importance: red mullet, Mullidae; horse mackerel, Carangidae; perch, Percidae; serranaceae, Serranidae and some others. Except for the family perch, almost all representatives of the suborder are marine forms. In suborder blennies, Blennoidei - 7 families. All inhabitants of the seas, some (for example, families eelpouts, Zoarcidae and catfish, Anarhichadidae) are of commercial importance. In suborder mackerels, Scombroidei 4 families, 3 of which are of great commercial importance: mackerel, or mackerel, Scombridae; bonito, Cybiidae and tuna, Thunnidae. All these fish are marine. The suborder includes sword - fish family Xiphiidae, occasionally found in the Black Sea. To suborder gobies, Gobioidei are marine and freshwater species from the families gobies, Gobiidae and firebrands, Eleotridae; the latter are found only in the Amur basin. Both families are important in the fishery. 12(5). Pelvic fins present

see 13

13(14). Pelvic fins modified into spines

Suborder Prickly-shaped, GtasterosteoideiOrder Spine-like, Gasterosteiformes

In the USSR, the only family - stickleback, Gasterosteidae. Distributed in the Baltic, northern seas, Okhotsk and their basins. 14(13). Pelvic fins of normal appearance (not turned into spines)

see 15

15(18). The pelvic fins are located under the pectorals, in front of them or only slightly behind.

see 16

16(17). An unpaired mustache on the chin. Rays of fins dissected (soft)

Order Codfishes, Gadiformes

In the USSR, the most diverse family cod Gadidae. In the northern seas of the USSR, their intensive fishing is carried out; in the global fisheries cod take second place. 17(16). There are no antennae on the chin or they are paired. In the fins, as a rule, there are undivided (spiny) rays

Order Perciformes (Prickly-finned, Perciformes)

18(15). The pelvic fins are located far behind the pectorals.

see 19

19(30). There is only one real dorsal fin; if there are two of them, then the back, the so-called "fat", is soft and does not contain rays

see 20

20(21). The jaws are narrow and strongly protruding; if the jaws are of a different type, then the pectoral fins are very long, wing-shaped, adapted for flight (the tail in this case is hypocercal, that is, its lower lobe is noticeably longer than the upper one). The dorsal fin is located above the anal

Order Garfish, Beloniformes

There are 2 suborders in the squad. Suborder flying fish, Exocoetoidei with a single family, Exocoetidae, includes peculiar fish that, when moving rapidly, jump out of the water and make a long soaring jump in the air. At flying fish pectoral fins are strongly developed, supporting them in flight. The lower lobe of the tail is much longer than the upper one and serves to give translational motion to the fish jumping out of the water. In suborder mackerel pike, Scomberesocoidei 3 families: mackerel, Scomberesocidae; half-snouts, Hemirhamphidae and garfish, Belonidae. All garfish- marine fish ( half-snouts also enter the mouths of rivers); live in tropical and temperate waters. In the USSR, the most numerous garfish(mainly the Baltic and Black Seas). 21(20). Jaws not strongly elongated; normal pectoral fins

see 22

22(27). The maxillary bone in the posterior region is free (not immersed in the skin; its posterior end can be raised)

see 23

23(24). The dorsal fin is located on the tail stalk, above the anal fin.

Suborder Pike, Esocoideiorder Salmonformes, Salmoniformes

This suborder includes freshwater fish that live mainly among thickets of underwater plants. Widespread in the waters of the Northern Hemisphere. In the USSR, the most common pike(family Esocidae). There are representatives of two more families: black fish, Dalliidae (rivers of the Chukchi Peninsula) and evdoshkovye, Umbridae (lower reaches of the Dniester). 24(23). The real dorsal fin is located approximately in the middle of the back, not above the anal (on the stalk of the tail above the anal fin there may be a soft, rayless "adipose" fin)

see 25

25(26). On the tail stalk above the anal fin there is no soft, rayless "adipose" fin

Order Herring, Clupeiformes

Includes 2 families: herring, Clupeidae and anchovy, Engraulidae. The former are widespread in the Arctic Ocean basin, Far Eastern waters, the Baltic, Black and Azov Seas, and are of paramount commercial importance. 26(25). On the tail stalk above the anal fin is a small, soft, rayless "adipose" fin.

Order Salmonformes, Salmoniformes

Includes marine, anadromous and freshwater forms. Representatives of the families salmon, Salmonidae and smelt, Osmeridae. In addition to them, representatives of the families grayling, Thymallidae and fish noodles, Salangoidae, also of commercial importance. This order also includes the suborder pike, Esocoidei (Ref: Para. 23); often pike assigned to an independent group. 27(22). The maxillary bone is immersed in the skin, its posterior edge does not protrude

see 28

28(29). The pectoral fins have powerful jagged spiny bone rays, the mouth is not retractable, there are small teeth on the jaw bones, no scales

Order Catfish, Siluriformes

Representatives of the family meet in the USSR catfish, Siluridae, widespread in the fresh waters of Europe and Asia; are of commercial importance. In addition, the families represented in the USSR killer whales, Bagridae (basin of the Amur River) and sisorides, Sisoridae (Amu Darya, Syr Darya and some other water bodies). Representatives of the family acclimatized in the western regions of the USSR american catfish, Amiuridae. 29(28). There are no powerful jagged bone rays in the pectoral fins, the mouth is retractable, there are no teeth on the jaw bones, the body is covered with scales (it can be very small and immersed in the skin)

Order Cypriniformes, Cypriniformes

In the USSR, there is a single suborder - cyprinids, Cyprinoidei, widespread mainly in fresh waters all parts of the world except Australia, South America and Madagascar. In the USSR, representatives of the family carp,Cyprinidae; many species are of commercial importance. In addition to them, in the USSR there are representatives of the family loach, Cobitidae and one species of the family Chukuchan, Catostomidae. 30(19). Has two true (ray-bearing) dorsal fins

Order Mullet-shaped, Mugiliformes

The order includes marine (coastal and pelagic; some species enter rivers) fish of great commercial importance. There are 2 suborders in the detachment: mullet-shaped, Mugiloidei with families mullet, Mugilidae (in the USSR - the waters of the Black and Far Eastern seas) and atherinic, Atherinidae (Black, Azov and Caspian seas) and sphyrenoid, Sphyraenoidei with the only family Sphyraenidae (in the USSR - the Black Sea and the waters washing southern Primorye). . SUPERCLASS TERRESTRIAL VERTEBRATESTETRAPODACLASS AmphibiansAMPHIBIA

Fish are divided into two classes - Cartilaginous fish (sharks, rays) and Bony fish (sturgeon, salmon, herring, crucian carp, perch, pike, etc.). The main criterion for such a division is the substance that makes up the internal skeleton of fish (cartilage or bones).

Class Cartilaginous fish

Cartilaginous fish include:

• sharks.

• Stingrays.

• Chimeras.

The main characteristic features of cartilaginous fish are:

• cartilaginous skeleton that persists throughout life;
• lack of a swim bladder;
• gill covers absent, gills open outward with \(5\)–\(7\) gill slits;
• placoid scale;
• internal fertilization;
• most species live in salty waters, although there are also freshwater ones.

Class Bony fish

Signs of bony fish:

• there are bony gill covers covering the gill slits;
• internal skeleton, at least partially, bony;
• the fins are supported by bony rays (with the exception of lungfish);
• scales ganoid or bony (but not placoid);
• there is either a swim bladder (which may be secondarily underdeveloped), or (in rare cases) a lung.
• external fertilization, small eggs.

Bony fish are divided into osteocartilaginous, lungfish, lobe-finned and bony.

bony fish

To bony fish includes the majority of fish species that live in almost all water bodies of the Earth. This group includes fish herring detachments(herring, sardines, anchovies, two types of which are called anchovies), salmonids (noble salmon, or salmon, chum salmon, pink salmon, chinook salmon, sockeye salmon, whitefish, grayling, smelt), cyprinids (chub, roach, bream, ide, dace, asp, carp, crucian carp), catfish (catfish), cod-like (cod, saffron cod, haddock, blue whiting, pollock, burbot), flatfishes(flounder, halibut).

Osteocartilaginous, or sturgeon

osteocartilaginous, or sturgeon, fish have a bone-cartilaginous skeleton with a well-developed chord, there are gill covers, a swim bladder. Along the body of sturgeon there are \(5\) rows of bone plates, between which there are small bone plates.

Sturgeons are migratory fish of the northern hemisphere. They live up to \(50\)–\(100\) or more years. These fish are widely known for their special tasty meat and black caviar.

Examples: beluga, sterlet, Russian sturgeon.

Dipnoi

lungfish - ancient group fish. There are only \ (6 \) species, for example, the Australian horntooth, African and South American flake.

lungfish the notochord persists throughout life, the vertebral bodies do not develop, which indicates their antiquity. Along with the gills these fish have lungs developed from the swim bladder. The structure of the heart has also changed: the atrium is divided by an incomplete septum into the left and right halves. The right half receives blood from the gills, and the left half receives blood from the lungs.

Australian horntooth lives in rivers heavily overgrown with plants. In summer, when the reservoirs become shallow, it completely switches to breathing atmospheric air.

Other representatives of the lungfish - African flake(up to \ (2\) m long) and South American flake (up to \ (1\) m long) during the drying up of reservoirs they dig into the silt and hibernate.

lobe-finned fish

The lobe-finned fish are an ancient group of fish close to the lungfish. The swim bladder has become a paired lung. The nostrils communicate with the oropharynx. Currently, one modern representative is known - coelacanth.

Today we'll talk about large group animals - inhabitants of the aquatic environment - fish.

This is an extensive group of animals, according to various estimates, from 25 to 30 thousand species. All of them belong to jawed mouths with gill type breathing at all stages of development. They live in all in all reservoirs of the world with both fresh and salt water.

They are divided into several classes according to the structural features in connection with the time of origin. The most ancient in origin are representatives of the class of cartilaginous fish.

Class Cartilaginous fish. There are very few of them left, about 800 living species. However, they are well known. These are fish with a cartilaginous skeleton. They have no skin bones, placoid scales, with tooth-like spines. It should be noted especially that teeth are formed from the same rudiments on the jaws.

Sharks are an excellent representative of this class. These amazing creatures are perfectly adapted to life in their element. We note the features of their structure.

1. They have 5-7 gill slits on each side (not covered by anything) and well-developed spiracles located behind the eyes. Behind the slits are gills, consisting of gill arches, on which are located gill petals. Sharks constantly swim with their mouths open to provide a continuous flow of water containing oxygen dissolved in water. Water enters the mouth opening and exits through the gill slits, while washing the gill filaments. This is how gas exchange works.

2. Respiratory system closely related to the circulatory system. Here there is one circle of blood circulation. A two-chambered heart, consisting of one atrium and one ventricle, filled with venous blood.

3. Fish locomotion (movement). In any thriving species we find many adaptations to environmental conditions, and fish are no exception. Their body has a streamlined shape, pointed at both ends. Thanks to this, the flow of water easily bends around the body, reducing resistance to almost nothing. Fish have no protruding body parts, with the exception of fins. Shark heavier than sea water because it does not have a swim bladder, and if it stops, it will begin to sink to the bottom (simply sink). To prevent this from happening, the paired pectoral and ventral fins work as hydrofoils. They can turn at different angles to the long axis of the body when the fish needs to rise or fall in the water column. shark heterocercal caudal fin - its dorsal lobe is larger than the ventral one.

4. Digestive system normally consists of the pharynx. It opens into the esophagus and then into the stomach. The stomach opens into the intestine, which is divided into the small and large intestines. The anus, together with the urogenital opening, often opens into the cloaca. Digestive glands are well developed: pancreas and liver.

5. excretory system fish is represented by the middle kidney - two ribbons on the sides of the spine, stretching along the body cavity. In them venous blood releases waste products. Urine is collected in paired ureters, which open into the cloaca through a common opening. In males, the genital and urinary organs often have a common excretory duct.

6. Sharks are dioecious. Among them are oviparous and viviparous.

stingrays similar to sharks, but their body is flattened in the dorsal-ventral direction. These are usually bottom fish. Their gill slits have moved to the ventral side, so they draw water for breathing through the sprinklers so as not to clog the gills with sand. Sawfish rays (fish-saws) again acquired a shark-like shape, but their gills remained on the lower surface of the head. Like sharks, rays can be both oviparous and viviparous. They feed on benthic organisms and fish. In stingrays, at the base of the tail, there is a long dagger-shaped needle (32–35 cm), often serrated, with a groove that secretes poison. A stingray's tail can pierce a leather boot. Their injections often lead to death. On the islands of Oceania, spearheads were made from the needles of these animals in the old days.

Other slopes - electrical have electric organs on the sides of the body. They are modified muscles that can generate a discharge of up to 220 V. With such a blow, the stingray kills prey, usually small fish, and can stun a person who accidentally touches it.

Some stingrays broke away from the bottom and moved on to life in the water column. Everyone knows the manta - the largest stingray. The width of its disc-shaped body reaches 6.5 m, and the body weight is up to 2 tons. When they swim, it seems that they rather fly, flapping their fins like birds wings. They can sometimes fly out of the water. They give birth to rather large cubs, which are in the oviducts of the mother for a long time feeds with nutrient fluid.

I propose to get acquainted with the features of the external structure in more detail by completing a virtual laboratory work on the website http://www.virtulab.net/index.php?option=com_content&view=article&id=160:2009-08-23-11-44-36&catid=42:7&Itemid=103.

In internal structure This vast group is also undergoing changes.

1. Nervous system represented by the brain, consisting of five sections, and the spinal cord. The brain is small in size, the most developed midbrain and cerebellum associated with fine coordination of movements. Of the sense organs, the organ of taste is best developed. taste buds located not only in the oral cavity, but also scattered over many parts of the body in the outer layer of the skin. This allows migratory fish, such as salmon, to focus on chemical composition water, find freshwater sources in which they were born.

2. Digestive system arranged differently depending on the nature of the food. In most species, the oral cavity is armed conical unimodal teeth. The oral cavity is not separated from the pharynx leading to a short esophagus. Stomach of various shapes and sizes, in some it is very poorly developed. At deep sea predators forced to fast often and for a long time in anticipation of prey, the stomach can stretch to such a size that the prey may not fit inside the body. Then the stomach is stretched so much that it hangs under the body of the fish. Intestines poorly differentiated. Liver provided with a gallbladder. Pancreas in the form of small lobules scattered over the mesentery.

There is a swim bladder.

Please complete the following tasks and answer the questions.

1. Briefly describe how the respiratory and circulatory systems of fish interact.

2. What is the primitive structure of cartilaginous fish?

3. Where does the swim bladder come from? What is its function? Do all fish have the same structure?

Cartilaginous fish class skeleton representatives structure difference swim bladder system signs organs gill covers characteristic

Latin name Condrichtities

general characteristics

A relatively small modern (about 600 species) group of fish, in the organization of which primitive features are combined (mainly) with features of progressiveness.

Skeleton cartilaginous fish remains cartilaginous for life. The shoulder girdle of the limbs is represented by a solid cartilaginous arch, covering the body from the sides and from below.

Cartilaginous fish skin covered with the most primitive type of scales - placoid (rarely bare skin). There are relatively many gill slits (5-7), and each slit opens outwards with an independent slit-like opening (the exception is the frilled shark and chimeras). The paired fins are horizontal. There is no swim bladder.

Along with what has been said, cartilaginous fish are characterized by such progressive characters as the presence of nerve matter in the roof of the forebrain, internal insemination, and in many species, live birth.

The body sizes of cartilaginous fish are very different: from 20 cm to 15 and even 20 m. They are distributed in all seas (except the Caspian) and oceans, mainly in tropical latitudes. Some species enter rivers. In some places they are important in commercial fishing.

Cartilaginous fish are divided into two subclasses:

• Lamellar gills (Elasmobranchii)
• Whole-headed, or chimeric (Holocephali).

Subclass Lamellar gills (Elasmobranchii)

Such cartilaginous fish sharks and rays belong to this subclass. They are characterized by the presence of placoid scales. Each external branchial opening opens independently on the surface of the body. There is a cesspool. Due to the presence in most species of an outgrowth at the anterior end of the head, the so-called rostrum, the mouth opening is located on the underside of the head in the form of a transverse slit. The skull is often hyostylic, less often amphistylic.

For a more detailed understanding of the features of the organization of the lamellar gills, consider the structure of the shark.

Appearance.

The general body shape of most sharks is elongated, spindle-shaped. Anteriorly, the head bears a rostrum. On the sides of the head gill slits are visible, the number of which is usually 5 on each side; only a few modern sharks have up to 6-7 of them (Chlamydoselachidae and Hexanchidae). Behind the eyes are two openings leading to the pharynx. These are the so-called splashes, representing the rudiments of the gill slits located between the jaw and hyoid arches. On the lower surface of the body at the root of the tail is a cloaca. The caudal fin is unequal. The axis of the skeleton enters the upper, large lobe of the fin. This type of caudal fin is called heterocercal.

Paired limbs are represented by pectoral and ventral fins, which are located horizontally. In males, the inner parts of the pelvic fins form finger-like outgrowths that serve as copulatory organs.

Skin

The epidermis is multi-layered with numerous glandular cells that secrete their secret to the surface of the skin. Corium dense, fibrous. The skin is covered with placoid scales. The latter in the diagram represent a plate lying in the fibrous layer of the skin, and a tooth sitting on this plate; the top of the tooth is directed backwards. The scale develops in the corium and consists of the bone substance osteodentin, which is close to the dentin of the teeth of other vertebrates.

The tooth of the scale is covered on the outside with a thin cap of enamel, which is a derivative of the gland of the same name, which is formed during the development of scales in the inner layers of the epidermis. The scales cover the entire body of the fish and extend along the edges of the mouth opening onto the jaw. Here it is larger than on other parts of the body, and performs the function of teeth. This circumstance, as well as similarities in the development of teeth and placoid scales, emphasize their homology.

Cartilaginous fish Skeleton

The skeleton remains cartilaginous for life, although in some parts of it deposits of calcareous salts are observed.

The axial skeleton of cartilaginous fish consists of the vertebral column and the cerebral part of the skull. The spine is divided into only two sections: trunk and tail. Each vertebra consists of a vertebral body, from which the upper arches depart, having the form of an arch that limits the spinal canal; on top of these arcs, the superior spinous processes depart; lower arches extend from the lower lateral part of the vertebral bodies, which form the hemal canal in the caudal part of the spine, and in the trunk they are represented by short transverse processes extending to the sides.

The vertebral bodies are concave anteriorly and posteriorly (amphycoelous vertebrae). In the cavities formed between the bodies of adjacent vertebrae, the chord is preserved. In addition, the notochord is preserved inside the body of each vertebra, where it lies in a narrow foramen located in the center of the vertebral body.

The ribs attached to the spine limit the body cavity only from above and only slightly from the sides.

The brain skull consists of the brain case, capsules of the sense organs and the rostrum. All sensory capsules are paired; they are tightly fused with the basal lamina of the skull. The cartilaginous roof of the brain box is formed, which, however, is not complete, since in its front part there remains a large area covered with a membrane (anterior fountain). By growing into the skull of the first vertebra, the occipital region of the skull is formed.

The rostrum of cartilaginous fish consists of three rod-shaped cartilages extending from the front of the skull.

The visceral skeleton consists of the gill arches, the hyoid arch, and the jaw arch.

The jaw arch is made up of two paired cartilages. The upper pair of cartilages, called palatine square (palatoquadratum) cartilages, acts as the upper jaw. The lower pair of cartilages that act as the lower jaw are called Meckel's cartilages (cart, meckeli). In most sharks, the palatine-square cartilage is attached to the brain skull only in its anterior part. The posterior part of this cartilage is not directly connected with the skull, but is attached to it through the upper element of the hyoid arch - the hyomandibular cartilage (hyostyle). Only in a few species does the posterior portion of the palatine cartilage attach directly to the skull. However, in this case, the hyomandibular cartilage articulates with the palatine-square cartilage (amphistyly).

Anterior to the jaw arch are two pairs of small cartilages called labials, which represent the remains of the first and second visceral arches of ancient, primitive vertebrates. Consequently, the jaw arch of modern sharks is not the first, but the third visceral arch.

The hyoid, or hyoid, arch consists of a paired hyomandibular cartilage (hyomandibulare), a paired hyoid cartilage (hyoideum) and an unpaired cartilage - copula. The hyomandibular cartilage articulates with the skull and hyoid, as well as with the jaw arch. The copula connects the hyoids of the left and right sides.

Gill arches, of which there are usually five, consist of four paired cartilages and one unpaired one, lying on the ventral side of the arch and connecting its left and right parts. Cartilaginous rays sit along the posterior edge of the gill arches, serving as a support for the intergill septa.

limb skeleton

The skeleton of paired limbs of cartilaginous fishes is divided into the limb belt, which lies in the body of the body and serves as a support for the limbs, and into the skeleton of a free limb.

The belt of the forelimbs (pectoral fins) is represented by a cartilaginous arch lying freely in the thickness of the musculature and with its apex facing the abdominal surface. In the middle of each (left and right) half of the arc there are protrusions to which the skeleton of the free limb is attached. The sections of the belt lying upward from the indicated protrusion are called scapular, and those lying downwards are called coracoid.

The skeleton of the most anterior limb consists of three sections. At the heart of the fin are three cartilages - basals, attached to the belt. Rod-shaped cartilages are attached to the basals on one side - radials, arranged in several rows. Such a fin is called uniserial (in contrast to the biserial fin, in which the radials are located on both sides of the basal). Finally, long and thin elastoidin filaments of skin origin are attached to the radials.

The belt of the hind limbs (ventral fins) consists of unpaired cartilage located across the body in front of the cloaca. The skeleton of the pelvic fin itself has only one or two basales. Radials are attached to their outer edge.

The skeleton of unpaired fins consists of radials and elastoidin filaments.

Digestive organs

The jaws, which limit the mouth opening, usually bear rather large teeth. The oral cavity passes into the pharynx, perforated by gill slits. The previously mentioned spiracles, representing rudimentary gill slits, also open into the pharynx. The short esophagus opens into an arcuately curved stomach, from which a short small intestine also departs. In the mesentery lies the pancreas. The large intestine has a significant diameter and is equipped with a spiral valve. The latter has the same meaning in sharks as in cyclostomes. But in its structure, attention is drawn to the steeper twists of the valve fold, in connection with which they form a greater number of revolutions than in cyclostomes. The bilobed liver is supplied with a gallbladder; the bile duct flows into the initial section of the small intestine.

As can be seen, a common morphological feature of the digestive tract of cartilaginous fish, which characterizes its complication, is, firstly, its greater division into sections than in cyclostomes and, secondly, the general elongation of the entire tract, which is associated with the formation of bends in the digestive tube. Recall that in cyclostomes the digestive tube is straight.

In the body cavity, near the convex side of the stomach, lies the spleen.

Respiratory system

Each gill slit opens at one end into the pharynx, and at the other - independently on the surface of the body. Gill openings are delimited from each other by wide intergill septa, in the thickness of which cartilaginous gill arches lie. Gill filaments sit on the anterior and posterior walls of the gill slits, where they form semigills.

Unlike cyclostomes, the gill filaments of fish are of ectodermal origin.

Circulatory system

The heart of cartilaginous fish is two-chambered, consisting of an atrium and a ventricle. A wide thin-walled venous sinus adjoins the atrium, into which venous blood flows. The arterial cone adjoins the final (by blood flow) part of the ventricle, which is essentially a part of the ventricle, although outwardly it looks like the beginning of the abdominal aorta. The belonging of the arterial cone to the heart is proved by the presence in it (as well as in other parts of the heart) of striated muscles.

The abdominal aorta originates from the arterial cone, giving five pairs of gill, arterial arches to the gills. Parts of the arches up to the gill filaments are called the afferent gill arteries, while their parts, coming from the gills and carrying already oxidized blood, are called the efferent gill arteries. The latter flow into paired longitudinal vessels - the roots of the aorta, which, merging, form the main arterial trunk - the dorsal aorta, which lies under the spine and supplies blood to the internal organs. Anteriorly from the roots of the aorta (or from the first pair of efferent branchial arteries), the carotid arteries depart, carrying blood to the head.

Venous blood from the head is collected in paired jugular veins (otherwise called anterior cardinal veins). From the trunk, blood is collected in paired cardinal veins, which at the level of the heart merge with the jugular veins of the corresponding side, resulting in the formation of paired Cuvier ducts that flow into the venous sinus. The cardinal veins form the portal circulatory system in the kidneys. From the intestines, blood enters through the subintestinal vein, which forms the portal circulatory system in the liver. From the liver, blood flows through the hepatic vein (often a steam room) into the venous sinus.

Nervous system

The brain is relatively large. Nerve substance in the hemispheres of the forebrain is present not only on its bottom and sides, but also on the roof of the brain. The midbrain is well developed, the cerebellum is large.

There are eleven pairs of head nerves. They have typical places otkhozhdeniye and sphere of an innervation.

sense organs

The olfactory sacs are paired and terminate blindly. There is no parietal "eye". Paired eyes have a typical structure for fish: their cornea is flat, the lens is spherical, there are no upper and lower eyelids. In a few species there is a nictitating membrane that can tighten the eyeball from its lower inner edge to the upper one. The organ of hearing is represented only by the inner ear - the membranous labyrinth. There are three semicircular canals. The lateral line is well defined. In most, it represents a canal that lies in the skin and communicates with the external environment through quite often located holes. In primitive sharks (Chlamydoselachus), the lateral line represents a channel open from above - a furrow.

Urogenital organs.

The organs of excretion are the primary kidneys - mesonephros. As their excretory ducts, a paired Wolf canal functions, which flows into the cloaca.

Most ovaries are paired. Paired oviducts (Müllerian canals) are not connected to the ovaries, but open into the body cavity in their immediate vicinity. The shell glands are located in the upper part of the oviducts. The expanded lower sections of the oviducts open into the cloaca. The genital and urinary tracts of females are separated throughout.

Paired testes are connected by a system of tubules with the anterior sections of the kidneys. These tubules pass through the substance of the kidneys and flow into the Wolf channels. Thus, these latter serve in males not only as ureters, but also as vas deferens. The anterior sections of the kidneys do not have an excretory function and serve as appendages of the testes. Only the posterior sections of the kidneys function as excretory organs.

The vas deferens in their lower section are expanded and form thin-walled seminal vesicles. Both Wolfian canals empty into the urogenital sinus, which opens into the cloaca.

Classification General characteristics of units

Shark Order (Selachoidei)

The body shape is usually fusiform and only in a few species is somewhat flattened. Gill slits open on the sides of the anterior part of the body. The fins are developed proportionally. Numerous teeth with sharp apices. Body sizes are varied - from 20 cm to 15 m (sometimes more). About 10 families are known. Distributed in all oceans and seas (not found in the Caspian Sea). The total number of species is about 250.

Order Stingrays (Batoidei)

Cartilaginous fish with a body flattened in the dorsal direction and strongly developed pectoral fins. Due to the flattening of the body, the gill openings are located on the ventral side of the body. The spatters are better developed than those of sharks. The stingrays lying on the bottom draw water for breathing through sprays. Stingrays have adapted to a sedentary benthic lifestyle. The caudal fin, the most important organ of translational movement, is very poorly developed in them. Stingrays often feed on sedentary benthic animals - mollusks, crustaceans. Their teeth are usually blunt, adapted for grinding the shells and chitinous covers of arthropods.