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

2. Remember the features of the structure of cartilaginous fish. What features of sturgeons emphasize their similarity to cartilaginous fish?

The spine retains the notochord

3. Sturgeons are also called anadromous fish. Explain this name

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

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

In summer - from 9.5 to 61 thousand caviar

Spring - from 2 to 20 thousand caviar

Yes, most salmon species can be considered anadromous

6. Why are piranhas dangerous for animals and humans?

The piranha's teeth allow them to tear large chunks of meat from the body of their prey.

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

Electrical discharges serve to protect against enemies and to obtain food.

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

There are areas of tissue that allow you to absorb oxygen

9. List the types of fish bred in fish farms

Carp, tench, pike, zander, sabrefish

10. Name the types of fish of the cyprinoid order, bred in aquatic aquariums

Barbs, labeo, goldfish

11. How can perch-like fish be distinguished by the appearance of the structure

The pelvic fins are located under the pectorals. The fin has the shape of an undivided sharp spike

12. Complete the scheme "Families of the order Perciformes"

1. stone perch

2. perch with childbirth

3. scad

4. crucian carp

5. rotosthenic

6. catfish

7. bull

8. sailboats

13. Look at pictures 94 and 95 of the textbook (pp. 111 and 112). Write down the species names of fish of the Cyprinidae and Perciformes orders, which you caught in the rivers and lakes of your area

Squad Cyprinoid: bream, carp

Order Perciformes: perch, pike perch

14. Look at the pictures. Write down the numbers of the fish included in the corresponding orders.

Order Sturgeons: 6, 3

Order Herring-like: 5, 7

Order Salmonformes: 10, 8

Order Cyprinidae: 2, 4

Order Perciformes: 1, 9

15. Look at the pictures, sign the names of the fish

16. Why are protoptera, lepidosiren, horntooth classified 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 up of the reservoir

18. What changes in the fins of coelacanths allow us to call them lobe-finned fish?

Paired fins serve as support, represent lobes, consisting of several cystic segments

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

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

20. Explain why lungfish and lobe-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 gill covers, the border between the body and tail is the anal fin.

Insert Flash

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

• corium or dermis
• and a multi-layered 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 ventral fins, which are mainly responsible for vertical movement, as well as an unpaired caudal fin, which acts as a rudder.

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

Fins:

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

The 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. limb skeleton, which includes:

• skeleton of paired fins (free part and girdles)
• and a skeleton of unpaired fins.

Skeleton of fish - the figure shows the skeleton of a bone fish

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

In representatives of the class Cartilaginous fish, the skeleton consists only of cartilaginous tissue. Representatives of the class Bony fish in the skeleton contain both cartilage and bone tissue.

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 tail. The vertebrae of the thoracic spine have lateral processes to which the ribs are attached.

The skeleton of the head is represented by a cranium, to which the jaws and gill arches are connected, and in bony fish, gill covers. Cartilaginous fish do not have 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 an anus, which opens in front of the anal fin.

Only bony fish have a swim bladder.

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

Respiratory system fish

Fish breathe with gills

Fish breathe with the help of gills. Water enters the mouth, then from the pharynx, water passes through the gills into the external environment, while the blood vessels located in the gill filaments are saturated with oxygen.

The circulatory system of fish is closed

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

Insert Flash

The nervous system consists of:

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

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

The nervous system of fish consists of the brain and spinal cord and outgoing nerves

The olfactory lobes of the forebrain are well developed, since fish are very important role play the organs of chemical sense - smell and taste. 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 consists of paired kidneys, ureters, and bladder, which opens with the urethra, which is located next to the anus.

The reproductive system of fish

Most fish have separate sexes, males have two testes, females have two ovaries. Females spawn 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, fertilization is internal, females give birth to fry.

Systematics of fish

At the moment, about 30 thousand species of fish are known. The taxonomy of fish is quite complicated, we will consider a somewhat simplified scheme. Currently, different sources can be found different versions of taxonomy.

Cartilaginous and bony fish

The superclass of fish includes two classes - these are Cartilaginous fish and Bone fish.

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

Cartilaginous fish include sharks, rays and chimeras

To the class Cartilaginous fish relate:

• squad Sharks,
• detachment Stingrays
• and the order Chimaeriformes.

Cartilaginous fish are characterized by the following features - they do not have a swim bladder, there are no gill covers.

Cartilaginous fish - sharks and rays

The order Bony fish is the most numerous, up to 96% of fish species belong to it.

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

cartilaginous fish

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

Rice. 1. Cartilaginous skeleton (Source)

Rice. 2. Shark (Source)

Cartilage may be impregnated with calcium salts. Movable no gill covers, instead of them gill slits located on the ventral 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 naked or covered with scales, which in structure and composition resemble teeth, they are called so - skin teeth.

The class includes three divisions: Sharks, Rays, Chimeras(Fig. 4).

Rice. 4. Detachments (Source)

body shape: elongated torpedo-shaped body.

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

Leather: rough, covered with teeth and scales.

Fins: paired ventral and pectoral fins are horizontal, provide movement of the fish up or down. Forward movement and turns are provided by the bending of the tail or body.

Sense organs: 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 water and thus learn about prey at a great distance.

fertilization

Some sharks can attack people. Most sharks are marine fish, but some swim in fresh water. One species lives permanently in the freshwater lake of Nicaragua (Fig. 6). Some types of sharks are eaten by people, most often the Japanese, especially the liver and fins are considered 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: expanded pectoral fins on the sides, the caudal fin looks like a long thin whip.

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

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

Leather: naked or with skin teeth, there are glandular cells that secrete mucus.

fertilization: internal, reproduce by live birth or ovoviviparity.

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

Rice. 7. Skat (Source)

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

body shape: there is a powerful 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 filiform appendage.

Leather: naked and devoid of scales.

fertilization: internal, reproduce by laying eggs.

In total, about 30 species of chimera-like fish are known. The most studied European chimera lives in the Barents Sea at depths of more than 1000 m (Fig. 8). Nosed chimeras live in the Pacific and Atlantic Oceans (Fig. 9).

Rice. 8 European Chimera (Source)

Rice. 9 Nosed Chimera (Source)

BONE FISH

Class Bony fishincludes the vast majority of representatives of the superclass Pisces (about 20 thousand species) inhabiting fresh and salt water bodies.The name of the class indicates the presence of a bone skeleton, the body is covered with bony scales or plates, there are no skin teeth, unlike cartilaginous fish, the gill cavity is covered with gill covers that are mobile, there is a swim bladder, which may disappear in benthic and inactive 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 lungfish. Most of this once huge group died out in the Triassic period, but there are also several modern groups of lungfish (Fig. 2).

Rice. 2 Australian Horntooth

In total, there are about 20 thousand species of bony fish, although this is not very often talked about, but bony fish are the most numerous class of vertebrates. Features of ecology, structure and physiology of individual species make it possible to divide all this vast diversity into several dozen orders.

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

Sturgeons are 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. Sturgeons

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

Most sturgeons feed on aquatic invertebrates, some species feed on small or even large fish.

Meat and especially sturgeon caviar is 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 fact is that adult fish cannot climb up the river through the dam (Fig. 5).

Rice. 4. Black sturgeon caviar

Rice. 5. Hydroelectric power plant

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

Rice. 6. Herring

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

Rice. 7. Commercial value of herring

Includes fish similar to herring, from 2.5 cm to 1.5 m long (Fig. 8). Most representatives of the salmon family are migratory fish, but there are also freshwater forms.

Rice. 8. Salmon

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

Rice. 9. Wedding attire of salmon

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

Rice. 10. Salmon fishing

Representatives of this order are very similar to herring-like ones, but differ from them in the 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 cyprinids, there are both herbivorous, omnivorous and even predatory fish. Predatory fish include, for example, piranha and electric eel (Fig. 12).

Rice. 12. Piranha and electric eel

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

Rice. 13. Fish farms

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

Rice. 14. Japanese koi

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

Rice. 15. Perciformes

Perch-like species are distributed in water bodies of all continents, in all seas and oceans. Body length - from 1 cm to 5 meters. Mass - from fractions of a gram to a ton or more. For example, a fish moon can be up to 3 meters long and weigh almost one and a half tons (Fig. 16).

Rice. 16. Moonfish

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

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

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

Rice. 17. Coelacanths

Modern lungfish

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

Lungfish have both a number of primitive features and a number of features that unite them with amphibians, the most important such feature being, of course, the presence of lungs. The most famous of the modern lungfish is the genus Protopter (Fig. 18).

Rice. 18. Protopter

Protopters live in temporary drying 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 up of the reservoir.

electric eel

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

Electric eels live in waters with low oxygen content. Electric eels have the ability to use the oxygen in the air, for this the fish rises to the surface of the water and captures the air with its mouth.

The electric eel is capable of generating a discharge of up to 350 volts, thus, these fish protect themselves or hunt with electricity (Fig. 19).

Rice. 19. Electric eel

The Amazing Story of the Coelacanth

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

Rice. 20. Coelacanth

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

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 world: 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.

The external structure of the fish

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

The internal structure of fish

Fish organ systems
	1. Skull (consists of the braincase, jaws, gill arches and gill covers) 2. The skeleton of the body (consists of vertebrae with processes-arcs and ribs) 3. Skeleton of fins (paired - pectoral and ventral, unpaired - dorsal, anal, caudal)	1. Brain protection, food capture, gill protection 2. Protection of internal organs 3. Movement, balance
musculature	Wide muscle bands divided into segments	Motion
Nervous system	1. Brain (sections - anterior, middle, oblong, cerebellum) 2. Spinal cord (along the spine)	1. Movement control, unconditioned and conditioned reflexes 2. Implementation of the simplest reflexes, conduction of nerve impulses 3. Perception and conduction of signals
sense organs	3. Organ of hearing 4. Touch and taste cells (on the body) 5. Lateral 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, grinding, moving food 2. secretion of juices that contribute to the digestion of food
swim bladder	Filled with a mixture of gases	Adjusts the immersion depth
Respiratory system	Gill filaments and gill arches	Carry out gas exchange
Circulatory system (closed)	Heart (double-chambered) arteries capillaries	Supply of all cells of the body with oxygen and nutrients, removal of 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 the fish

Fish Class Classification

Currently living fish are divided into 2 main classes: cartilaginous fish and bony fish. Important distinguishing features of cartilaginous fish are 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. The most common among them are sharks and rays.

The vast majority of modern fish belongs to the class of bony fish. Representatives of this class have a ossified internal skeleton. A pair of external gill slits are covered with gill covers. Many bony fish have a swim bladder.

The main groups of Pisces

Squads of fish	The main features of the detachment	Representatives
	Cartilaginous skeleton, no swim bladder, no gill covers; predators	Tiger shark, whale shark, katran
	Manta, stingray
Sturgeons	Osteo-cartilaginous skeleton, scales - five rows of large bone plates, between which there are small plates	Sturgeon, beluga, sterlet
Dipnoi	They have lungs and can breathe atmospheric air; notochord preserved, no vertebral bodies	Australian horned tooth, African flake
Crossopterygians	The skeleton mainly consists of cartilage, there is a notochord; poorly developed swim bladder, fins in the form of fleshy outgrowths of the body	Latimeria (the only representative)
Cypriniformes	Mostly fresh water fish, no teeth on the jaws, but there are pharyngeal teeth for grinding food	Carp, crucian carp, roach, bream
herring	Most are schooling marine 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-vaga, burbot, cod

Ecological groups of fish

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

Ecological groups of fish	Main features
freshwater fish	These fish constantly live in fresh water. Some, such as carp and tench, prefer stagnant water. Others, such as the common minnow, grayling, chub, have adapted to life in the flowing waters of rivers.
migratory fish	This includes fish that migrate from sea water to fresh water to breed (for example, salmon and sturgeon) or from fresh water to breed in salt water (some types of eels)
brackish fish	They inhabit desalinated areas of the seas, the mouths of large rivers: such are many whitefish, roach, goby, river flounder.
sea ​​fish	They live in the salt water of the seas and oceans. The water column is inhabited by fish such as anchovy, mackerel, tuna. At the bottom live stingray, flounder.

_______________

The source of information: Biology in tables and diagrams. / Edition 2e, - St. Petersburg: 2004.

Class FISH CARTILAGE(Chondrichthyes) Class FISH CARTILAGE (Chondrichthyes).

subclass. Elasmobranchh fishes (elasmobranchh) Sharks (selachomorpha) Superorder Rays (batomorpha) Superorder Fish fused or whole-headed (Holocephali) Subclass Subclass: Elasmobranchii - Elasmobranchh fishes Superorder: Selachimorpha - Sharks More than 450 species of existing sharks are united in 8 orders and 30 families: Carchariformes. This is the detachment that has 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. External distinguishing features vary greatly, but all are characterized by the presence of five gill slits, two dorsal fins (except for the one-fin cat shark (English)), and also an anal fin. The methods of reproduction are also very diverse - there are oviparous, ovoviviparous and viviparous species. Some people have oophagia. Miscellaneous. They appeared in the Triassic period, and represent a detachment of bottom sharks leading a nocturnal lifestyle. Their external features are a dense body, two spiny dorsal fins, and an anal fin. Distributed from the intertidal zone to the continental shelf. All species are oviparous. Polygilloid. The detachment is the oldest among the existing sharks - it was formed during the Permian period. It consists of two families that differ in body shape - eel-shaped in frilled sharks and the "traditional" torpedo-shaped in polygills. Both families are characterized by six or seven gill slits, one dorsal fin, and the presence of an anal fin. Predominantly common in the cool depths of the tropics, ovoviviparous. laminar. Appeared during the Jurassic period. This order is dominated by pelagic species. large sizes. They are torpedo-shaped, have five gill slits, two dorsal fins and an anal fin. Distributed from intertidal zone to deep waters ocean, ovoviviparous. Wobbegong-like. Appeared during the Jurassic period. Distributed in warm and tropical seas from the intertidal zone to deep waters. With the exception of the whale shark, all species are bottom dwellers. They have five gill slits, two dorsal fins and an anal fin. Among the species there are oviparous, ovoviviparous and viviparous. Some also have oophagia.

Sawtooth. 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. Live at the bottom, ovoviviparous. Katra-shaped. Appeared during the Jurassic period. This detachment is widespread and is found all over the world, including - the only shark - in latitudes close to the poles. They live at great depths. Representatives of the order have a torpedo-shaped body, five gill slits, two dorsal fins, and no anal fin. Ovoviviparous.

Squatoid. Appeared in the Triassic period. The habitat is typically continental shelf and intertidal silt or sand in cool temperatures, as well as deeper locations in tropical waters. The sharks of this order are distinguished by a wide flattened body, a short muzzle, five gill slits, large pectoral and ventral 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 from below, and wide pectoral fins are clearly visible, clearly separated from the head. All species are ovoviviparous.

52 taxonomy of cartilaginous fishes, diversity of rays. Class FISH CARTILAGE (Chondrichthyes).

subclass. Elasmobranchh Fish Rays (Anacanthobatidae) Diamond Rays (Rajidae) Rhinidae Dead Rays (Rhinobatidae) Sharktail 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 spiracles. The stingrays of this order lack caudal spines, and the caudal fin is greatly reduced. They typically lead a benthic lifestyle. 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 mostly live in coastal waters, although there are also deep-sea stingrays.

Today, this detachment is the most numerous and includes about 200 species of rays. They are distributed everywhere, however, they reach the greatest diversity in the subpolar regions and regions with a temperate climate. IN Russian waters the order is represented by only one family - the family of diamond-shaped rays (Rajidae). They feed on small fish and benthic invertebrates. The process of reproduction occurs by laying cornea-covered eggs.

53 question The main features of the organization. Cartilaginous fish, characteristics of lamellar-gill and whole-headed. Lamellar gills * (Lamellibranchiata) - a class of type of molluscs. Characteristics of P.: the body is usually quite symmetrical, almost always laterally compressed, covered from the sides by two large lobes of the mantle, between which there is a large mantle cavity containing the lower part of the body and the leg of the animal, two gills attached to the sides of the body and 2 pairs of triangular oral lobes; shell of two lateral valves connected to each other at the dorsal margin and brought together by means of 1 or 2 muscles extending from one valve to the other; there is no separate head, head tentacles, pharynx, jaws and radula; kidneys and sex glands are paired; heart with 2 atria; dioecious or hermaphrodite, exclusively aquatic animals, freshwater and marine, mostly free, less often, in adulthood, attached. Despite the considerable diversity in appearance and structure, P. represent a very natural group, easily distinguishable from other representatives of the mollusk type. In the vast majority of P., the body represents a completely pronounced two-sided symmetry; less often, symmetry is broken by the unequal development of the right and left halves due to the fact that the animal in its adult state is either attached to underwater objects (usually grown) on one side (for example, an oyster), or usually lies on one side (for example, some species scallop - Pecten); while 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 the wood borer; see Mollusks, respectively fig.). In addition to the shell valves, the mantle may exude calcareous deposits in the form of additional plates or a layer lining the channels in which the mollusk (wood borer) lives, or in the form of a tube replacing the shell, while the minor valves of the latter merge with the tube (in the sprinkler - see Fig. , or watering cans - Aspergillum). On the dorsal edge, the valves are connected by the so-called. a strand (ligamentum), which, when the muscles contract, i.e., close the shell, is compressed, and when the muscles relax, it pushes the valves apart. In addition to the cord, 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 close, the protrusions of one enter into the depressions of the other, contributing to the tight connection of the valves of the closed shell. On the inner surface of the valves, a line is visible corresponding to the edge of the mantle, and the attachment points of 1 or 2 strong muscles that bring the valves together. Approximate valves do not always completely touch: they often leave a more or less significant hole open (gaping shells). Both lobes of the mantle may be completely free at the anterior, lower, and posterior edges, or may be fused to each other over a more or less significant extent in one, two, rarely in three places. Due to adhesions or sometimes close fit in certain places to each other of the lobes of the mantle, the entrance to the mantle cavity breaks up into 2-4 sections: through the posteriormost - the water that washed the gills is removed, along with feces and excretion products, through the next one enters the mantle cavity, water enters the mantle cavity, the leg extends through the anterior opening; behind the latter, there is occasionally another small opening, probably corresponding to the byssus; if there are only two openings, then water is discharged through the back, water is introduced through the anterior, 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 often elongate, forming two tubular siphons: through one (lower) water enters (gill siphon), through the other (upper) it exits (anal siphon); siphons can reach a length many times greater than the length of the shell; sometimes they are more or less connected to each other (cf. resp. fig.) Deprived of a separate head section, the body of the animal ends below with a muscular, more or less strongly developed, but sometimes rudimentary leg; most often, the foot is conical or wedge-shaped, but in some P. of the most primitive structure, the foot is equipped with an expanded flat sole (in Nucula, Leda, Yoldia). Many P. have a special gland in the leg that secretes dense threads similar to horn ones, the so-called Byssus, with which the animal can temporarily attach itself to underwater objects. The order True laminabranchs includes more than a hundred families and is divided into four suborders: Split-toothed (Schizodonta), Odd-toothed (Heterodonta) - the largest in terms of the number of families, genera and species, Adapedonta (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 elasmobranchii (Elasmobranchii) and bone fish (Osteichthyes). It is no coincidence that the great Linnaeus gave the name "Chimera" to one of the genera. First of all, they are related to elasmobranchial (selachia) by the presence of paired copulatory organs (pterygopodia) in males; the ability of females to lay large eggs enclosed in horn capsules; the presence of placoid scales (“skin teeth”) in the external skeleton and the complete absence of ossification of the internal cartilaginous skeleton, some elements of which are sometimes strengthened by calcification (should not be confused with ossification). In addition, in the heart of modern fused-cranials, as well as elasmobranchs, there is an arterial cone, equipped with three rows of valves; a spiral valve passes through the intestines; large nostrils are close to the transverse mouth and communicate with its rear corners with the help of furrows that cut the upper lip; the outer lobes of the fins are supported by a large number of thin elastoidine filaments (elastotrichia), while in bony fish the fin rays homologous to them are replaced by bony rays (lepidotrichia); the fleshy lips are supported by the labial cartilages, and just like in the elasmobranchs, the brain and heart are arranged and initially there is no swim bladder.

54 question general characteristics Bone class, system up to subclasses. The bony fish class is the largest superclass of fish. It includes about 20,000 species. This class is distributed in almost all water bodies of the world. The living conditions of bone fish are very diverse, which is the reason for 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, and also serrated or smooth, depending on the shape. The class of bony fishes in its diversity is several times greater than the class of cartilaginous ones. The structure of the skeleton is predominantly bone. The emergence of the bone skeleton is possible in two main ways. The initial type of ossification is 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 features described above, 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 producing osteoblasts. As chondral bones appear, the fish skeleton gradually ossifies, which makes its own adjustments to the overall structure of the skeleton. Due to the formation of integumentary ossifications, new elements of the skeleton appear, which greatly complicates its overall structure. There is a reduction of the intercostal septa of the respiratory apparatus. The lobes of the gills are located directly outside the gill apparatus. Most bony fish species have a swim bladder. Almost all fish species of this class reproduce by external fertilization. The laid eggs are small, without horn-shaped shells. A negligible number of fish species of the bone class have live-born offspring. The classification of bony fish is so complex that at present there are several views on the systematics of this group. Subclass Ray-finned fish (Actinopterygii) Subclass Lobe-finned fish (Sarcopterygii).

55. Characteristics of the Lobe-finned: features of the organization, their origin and evolution.

Lobe-finned (lat. Sarcopterygii) or choan - a class of bony fish. The basis of the axial skeleton is an elastic chord. Known since the early Devonian (300-400 million years ago), they combine both archaic and progressive features. The lobe-finned superorders include the lobe-finned and lobe-finned superorders. Lobe-finned fish (unlike ray-finned fish) moved to living in inland waters, their outgrowth of the esophagus turns into a lung, the leading analyzer is the sense of smell, and compared to other fish, the brain changes. Scales cosmoid or bony. Throughout life, the notochord is preserved, surrounded by a dense connective tissue fibrous-elastic membrane. Upper and lower arches develop, and the caudal region sometimes has underdeveloped vertebral bodies (some fossil groups were better developed than living species). The skull is amphilic or autostylic. Among the integumentary bones of the skull there is a squamosal bone. The tail is heterocercal (fossil) or diphycercal. Paired fins with a fleshy lobe covered with scales at the base; their skeleton is of the biserial type. There is an arterial cone in the heart. The intestine has a spiral valve and opens into the cloaca. As outgrowths of the abdominal side of the initial part of the esophagus, one or two bubbles are formed that perform the function of the lungs. Known from the Lower Devonian. Superorder lobe-finned fishes (CROSSOPTER YGIMORPHA). The brain skull is divided into two parts - the olfactory and the brain proper, movably connected to each other. The degree of ossification of the skull varies, integumentary ossifications are developed. The skull is amphistylic, in some species there is a transition to autostyly. 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 defined groups. Freshwater predators that have repeatedly penetrated into the seas.

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