Locomotor system of bony fish. The musculoskeletal system (skeleton) of fish. Nervous system and sensory organs of amphibians

U cartilaginous fish skeleton more advanced, compared to cyclostomes. Expressed differentiation to departments, the number of components elements. Chord almost is being forced out developing cartilaginous bodies biconcave (amphicoelous) vertebrae. The spinal column is divided into two sections - trunk and tail. Scull also has more complex building - appears occipital region, is developing jaw apparatus, the connection between the brain and visceral parts is strengthened ( amphistyly and hyostyly). The limbs and their attachment become more complex. Despite the cartilaginous basis, the skeleton has great strength.

Has undergone significant changes muscular system, which increased in mass and underwent further differentiation, although it largely remained metamerically st. Complications in support apparatus are not accidental, since cartilaginous fish are large in size, have significant biomass and are in almost constant motion.

The structure of the skull

The head skeleton of cartilaginous fish consists of two interconnected sections – cerebral and visceral. Each of them, in turn, is usually divided into component parts. IN brain department included roof, sides, bottom and back of the head. Visceral department contains jaw, hyoid arches and skeleton of the branchial apparatus (Fig. 21).

Rice. 21. Shark Skull:

1 – nasal capsule, 2 – rostrum, 3 – orbit, 4 – occipital capsule, 5 – palatoquadrate cartilage, 6 – Meckel’s cartilage, 7 – labial cartilages, 8 – hyomandibular (suspension), 9 – hyoid, 10 – branchial arches .

brain skull sharks serve as protection for the brain and consist from the braincase, paired capsules of the sensory organs and rostrum. From these cartilaginous formations are formed following departments:

Cerebral roof – incomplete, has a hole (fontanelle), which is covered with dense connective tissue. Sides of the skull form large depressions - eye sockets, and behind them, growing into the braincase, are paired auditory capsules. At the front end are nasal capsule And rostrum from three rod-shaped cartilages, fused together and supporting the snout. On the sides of the base of the rostrum lie olfactory capsules, on the underside of which there are large holes. The capsules of the sensory organs, merging with each other, form the so-called orbit. The walls of the skull are pierced with openings for the passage of nerves and blood vessels.

In some cartilaginous fish (sawfish, sawfish) rostrum is very elongated and is flattened, lined with sharp teeth on the sides, which are modified placoid scales, and serves as a weapon of attack and defense.

Occipital region comprises unpaired cartilage, evolutionarily arose from the first vertebra; it contains in the middle big hole to connect the brain and spinal cord.

Floor of the skull not formed, the brain is protected from below by the cartilaginous elements of the visceral apparatus.

Visceral skull evolutionarily formed from gill arches that supported the pharyngeal region of ancient fish. In modern cartilaginous fish, as mentioned above, it is represented by three parts - maxillary, hyoid arches and arches of the gill apparatus.

Front component - jaw arch consists of two paired elements. One pair growing together into the palatoquadrate cartilage, forms upper jaw. Another pair in the form Meckel's cartilage composes lower jaw. On both jaws there are paired labial cartilages, increasing the surface of attachment of powerful visceral muscles. Both jaws are equipped with teeth derived from placoid scales.

Hyoid arch located behind the jaw arch. Its basis is paired hyoids, which are theirs upper ends attached to hyomandibular cartilages (hyomandibulare). Each of them, with its upper end, is attached to the brain skull in the region of the auditory capsule, while the lower end is connected through fibrous tissue to the maxillary arch and the middle element of the hyoid arch - hyoid. Therefore, the hyomandibular plays role suspension for jaws.

This type of attachment of the visceral skull to the brain is called hyostyly. A number of primitive sharks have amphistyly in the form of a combination of hyostyly with additional attachment of the process of the palatoquadrate cartilage to the base of the medulla. The right and left hyoids at the level of the bottom of the pharynx are connected to each other by means of unpaired cartilage - copulas, or sublingual cartilage.

Skeleton of the gill apparatus, next to the hyoid arch, represents five pairs of arcs. Each gill arch consists of four doubles elements that are movably connected to each other, and one unpaired, through which the right and left sides of the arcs are connected. Numerous cartilaginous rays extend from the hyoid and branchial arches, supporting the walls of the interbranchial septa.

Spine shark is firmly articulated with the occipital region brain skull and stretches to the end of the tail, entering its upper blade. There are two sections in the spine - trunk and tail. The vertebrae of a shark, like all cartilaginous fish, are biconcave ( amphicoelous). The notochord is preserved only in the intervertebral spaces and in the center of the vertebral body.

Every vertebra(Fig. 22) consists of vertebral body, superior and inferior arches. Between the upper arches of the vertebrae there are cartilaginous insert plates. The ends of the upper arcs, connecting, form spinal canal.

The lower arches in the vertebrae of the trunk are short, directed somewhat to the sides and form transverse processes, to which ribs are attached. In the caudal section, these arches, closing, form hemal canal where the caudal artery and vein pass.

Friends! We continue to study animals belonging to the phylum Chordata and the subphylum Vertebrata or Cranial. Today we move on to the Pisces superclass. This is a fairly extensive topic and its study will be divided into several video lessons.

Today we will talk about general characteristics and the taxonomy of the superclass of Fish, in the next two issues we will analyze in detail the structure of fish using the example of river perch, and then move on to consider the characteristics of reproduction and study the diversity of fish orders.

The external structure of fish

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

The body of fish can be divided into:

• head
• torso
• and tail

The boundary between the head and the body is the posterior edge of the gill covers, and the boundary between the body and the tail is the anal fin.

The top of the fish body is covered with skin, which consists of:

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

The epidermis contains numerous mucous glands; the 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 serves as a rudder.

Paired fins of fish - pectoral and ventral, unpaired - dorsal, anal and caudal

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

Fins:

• paired breasts
• paired abdominal
• unpaired dorsal (1 or more)
• unpaired anal
• unpaired caudal

Musculoskeletal system of fish

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 belts)
• and the skeleton of unpaired fins.

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

The skeleton of a 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 cartilage tissue. Representatives of the class Bony fish have both cartilage and bone tissue in their skeleton.

The spine provides support and protective function — spinal cord protected by vertebral arches. The spine consists of two sections - the trunk and the caudal. The vertebrae of the trunk spine have lateral processes to which the ribs are attached.

The skeleton of the head is represented by the 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 liver and gallbladder ducts open, as well as the pancreas. The intestines end anus, which opens in front of the anal fin.

Only bony fish have a swim bladder.

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

Respiratory system fish

Fish breathe using gills

Fish respiration is carried out using gills. Water enters the mouth, then from the pharynx the water passes through the gills into external environment, wherein blood vessels located in the gill filaments are saturated with oxygen.

Circulatory system of closed fish

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

Nervous system comprises:

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

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

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

The olfactory lobes of the forebrain are well developed, since the chemical sense organs of smell and taste play a very important role for fish. 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 kidneys, ureters and bladder.

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

Reproductive system of fish

Most fish are dioecious; males have two testes and females have two ovaries. Females spawn eggs (eggs) into the water, males spawn sperm. Fertilization occurs in the external environment.

Fish eggs - eggs

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

Taxonomy of fish

IN currently About 30 thousand species of fish are known. The taxonomy of fish is quite complex; we will consider a somewhat simplified diagram. Currently in different sources can be found various options systematics.

Classes cartilaginous and bony fish

The superclass of fish includes two classes - cartilaginous fish and bony fish.

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

Cartilaginous fish include sharks, rays and chimaeras

To the class Cartilaginous fish relate:

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

Cartilaginous fish are characterized by the following features: they have no swim bladder and no gill covers.

Cartilaginous fish - sharks and rays

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

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

To the class of bony fish include two subclass —

• Lobe-finned
• and ray-finned fish.

Podkass lobe-finned includes two superorder —

• lobe-finned
• and lungfish.

Most of the representatives of lobe-finned and lungfish have become extinct; they are considered the ancestors of reptiles.

TO subclass of ray-finned fish are superorders:

• Cartilaginous ganoids
• and bony fish.

TO Cartilaginous ganoids applies

• order Sturgeon or Bony-cartilaginous fish.

Their skeleton consists of both cartilaginous and bone tissue.

Superorder Bony fishes the most numerous, most of the modern fish belong to it - these are squads, How

• Herring,
• Salmonidae,
• Carp-like,
• Perciformes,
• Codfish.

Characteristics of various orders of fish will be presented in future issues.

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

The body of fish can be divided into:

• head
• torso
• and tail

The boundary between the head and the body is the posterior edge of the gill covers, and the boundary between the body and the tail is the anal fin.

Insert Flash

The top of the fish body is covered with skin, which consists of:

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

The epidermis contains numerous mucous glands; the 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 serves as a rudder.

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

Fins:

• paired breasts
• paired abdominal
• unpaired dorsal (1 or more)
• unpaired anal
• unpaired caudal

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 belts)
• and the skeleton of unpaired fins.

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

The skeleton of a 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 have both cartilage and bone tissue in their skeleton.

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

The skeleton of the head is represented by the 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 liver and gallbladder ducts open, as well as the pancreas. The intestine ends at the anus, which opens in front of the anal fin.

Only bony fish have a swim bladder.

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

Respiratory system of fish

Fish breathe using gills

Fish respiration is carried out using gills. Water enters the mouth, then from the pharynx the water passes through the gills into the external environment, while the blood vessels located in the gill filaments are saturated with oxygen.

Circulatory system of closed fish

The circulatory system has one 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 section, which is represented by the brain and spinal cord and
• peripheral section, consisting of cranial and spinal nerves.

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

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

The olfactory lobes of the forebrain are well developed, since the organs of chemical sense - smell and taste - play a very important role for fish. 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 kidneys, ureters and bladder.

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

Reproductive system of fish

Most fish are dioecious; males have two testes and females have two ovaries. Females spawn eggs (eggs) into the water, males spawn sperm. Fertilization occurs in the external environment.

Fish eggs - eggs

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

Systematics of fish

Currently, about 30 thousand species of fish are known. The taxonomy of fish is quite complex; we will consider a somewhat simplified diagram. Currently, various taxonomy options can be found in different sources.

Classes cartilaginous and bony fish

The superclass of fish includes two classes - cartilaginous fish and bony fish.

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

Cartilaginous fish include sharks, rays and chimaeras

To the class Cartilaginous fish relate:

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

Cartilaginous fish are characterized by the following features: they have no swim bladder and no gill covers.

Cartilaginous fish - sharks and rays

The order Bony fishes 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 often 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 can be impregnated with calcium salts. Mobile no gill covers, instead of them gill slits, located on the abdominal part of the fish’s body or on the sides of the body (Fig. 3).

Rice. 3. Example of a whale shark's gill slits (Source)

There is no swim bladder. The skin can be bare or covered with scales, which in structure and composition resemble teeth, they are called - dermal teeth.

The class includes three units: Sharks, Rays, Chimaeras(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 pelvic and pectoral fins are located horizontally, allowing the fish to move up or down. Forward movement and turns are achieved by bending the tail or body.

Sense organs: the eyes are located on the sides of the head, vision is black and white. They have a strong sense of smell, feel the slightest vibrations in water, and thus learn about prey from a great distance.

Fertilization

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

Rice. 5. Tiger shark (Source)

Rice. 6. Nicaraguan freshwater shark (Source)

Body Shape: flattened in the dorso-ventral direction.

Fins: pectoral fins widened 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 stingrays can be about 12 cm in length.

Eyes and mouth: In benthic species, the eyes are located on the upper side of the head, in pelagic species - on the sides. The 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 viviparity or ovoviviparity.

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

Rice. 7. Skat (Source)

Chimaeras are a small and unique 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 thread-like appendage.

Leather: naked and without scales.

Fertilization: internal, reproduce by laying eggs.

In total, about 30 species of chimera-like fish are known. The most studied is the European chimera, which 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. Nose Chimera (Source)

BONE FISH

Class Bony fishincludes the vast majority of representatives of the superclass Fish (about 20 thousand species) inhabiting fresh and salt water bodies.The name of the class indicates the presence of a bony skeleton, the body is covered with bony scales or plates, there are no cutaneous teeth, unlike cartilaginous fish, the gill cavity is covered with gill covers that are mobile, there is a swim bladder, which can disappear in benthic and sedentary forms (Fig. 1).

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 became extinct in the Triassic, but several modern groups of lungfish exist (Fig. 2).

Rice. 2. Australian Horntooth

There are about 20 thousand species of bony fish, although this is not often talked about, but bony fish are the largest class of vertebrates. Features of the ecology, structure and physiology of individual species make it possible to divide all this enormous diversity into several dozen orders.

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

Sturgeons are a small group that has preserved a number of ancient characteristics that emphasize their similarity to cartilaginous fish. Thus, these fish retain their notochord throughout their lives, and their skeleton is osteochondral. The body is elongated, the head begins with a flattened snout (Fig. 3).

Rice. 3. Sturgeon

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

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

Sturgeon meat and especially caviar are extremely highly valued as delicacies (Fig. 4). Because of this, sturgeon have always been subject to poaching. The construction of hydroelectric power stations has led to the almost complete extinction of sturgeon 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 station

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

Rice. 6. Herring

Most herrings are marine fish, but there are also anadromous species, and some representatives have also colonized fresh water bodies. The most famous of the order is the Herring family. These are small to medium sized marine fish. Herring, sardines and sprat are of great commercial importance (Fig. 7).

Rice. 7. Commercial importance 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. Salmoniformes

Often, when entering rivers, salmonids develop a bright mating plumage (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 their tasty meat and caviar. Many salmonids are bred in special fish farms. It must be remembered that the diversity of the salmonidae order is by no means limited to the Salmonidae family (Fig. 10).

Rice. 10. Salmon fishing

Representatives of this order are very similar to herrings, but differ from them in the unique structure of their spine. The number of species in this order represents about 15 percent of the total diversity of bony fishes (Fig. 11).

Rice. 11. Cyprinids

Among the 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 importance 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 carp (Fig. 14). Some tropical cyprinids with beautiful and bright colors have become objects for keeping in aquariums.

Rice. 14. Japanese koi carp

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

Perciformes are widespread 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 moon fish can be up to 3 meters long and weigh up to almost one and a half tons (Fig. 16).

Rice. 16. Moonfish

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

It is obvious that many representatives of the order are eaten. Small perch are often favorites of aquarists.

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

Rice. 17. Coelacanths

Modern lungfishes

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 carp-like 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 of 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 producing a discharge of up to 350 volts, so these fish defend themselves or hunt using electricity (Fig. 19).

Rice. 19. Electric eel

The amazing story of the coelacanth

Fossil remains of coelacanth fishes have been known since the Devonian period. After the Cretaceous period, 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 living coelacanth (Fig. 20). The discovery of such a living fossil, of course, became a sensation. The fish was named coelacanth. Imagine: was found live fish, all of whose relatives went extinct during the age of dinosaurs.

Compared to cartilaginous fish , skeleton of bony fish almost completely bone And more differentiated. It is being composed two types of bones: chondral, arising through ossification of cartilage, which is formed embryonically, and skin (overhead), formed in the connective tissue layer of the skin. The structure of the parts of the brain and visceral skull changes significantly.

IN brain skull appear bone roof and bottom, becomes more complicated occipital region and lateral part. IN visceral skull undergoing changes jaw apparatus– appear secondary jaw And new elements, components primary jaw. Are being formed gill covers, performing the function of protecting the breathing apparatus and pumping water during gas exchange.

Vertebrae like all fish, amphicoelous type. They are attached to each other using articular processes located at bases of the upper arc. This ensures additional strengthening of the spinal skeleton while maintaining the necessary flexibility. TO lower arches vertebrae of the trunk are attached ribs, which cover the internal cavity of the body not only from above, but also from the sides. IN muscles many types are available thin bones strengthening motor muscle fibers. The skeleton of the limbs and their girdles is strengthened, which corresponds to a more active lifestyle

Let us consider in more detail the structure of the skeleton according to its constituent departments.

Scull

For the head skeleton bony fish are typical a large number of chondral and integumentary ossifications, providing more reliable protection to the brain.

Brain department the skull consists of well-formed four departments (Fig. 30). roof of the skull make up paired nasals, large frontal and relatively small parietal, between which lies unpaired interparietal. Located on the side of the nasal and frontal bones middle olfactory and doubles lateral olfactory. Skull roof bones integumentary aboutorigins with the exception of the middle and lateral olfactory bones, which are of mixed origin.

Bottom of the skull form two unpaired integumentary covers bones – rod-shaped parasphenoid and vomer, which has teeth. Occipital chondral origin and made up of four elements – unpaired superior occipital, inferior occipital And paired lateral occipital bones. The superior occipital is wedged into the parietal bones of the roof of the skull. The fusion of the bones of the occipital region forms a large foramen magnum to connect the brain and spinal cord.

Sides of the skull consists of the following chondral elements. In area auditory organ are five ear bones in front of which they lie sphenoid bones, forming the orbit - unpaired main wedge-shaped, paired lateral pterygo-sphenoid and oculocune-shaped. In front of the eye socket lies lachrymal bone, and at the bottom are located infraorbital, forming the orbital ring. Named elements of cutaneous origin.

Visceral skull.

Like cartilaginous fishes, the visceral skull of bony fishes consists of three parts – jaw arch, hyoid arch and skeleton of the branchial apparatus, however, the composition of their constituent elements differs significantly. Has undergone particularly strong changes jaw arch . The palate-square cartilage, which makes up the upper jaw in cartilaginous fish, has been replaced by a number of bone elements in bony fish. Lies in front of the jaw palatine bone, and in the back – square(chondral). Between them are located three pterygoids bones, two of which are integumentary, and one (next to the quadrate) is chondral. Due to such transformations, the primary upper jaw acquired greater strength, lengthened, but to a large extent lost the function of capturing food. This function is mainly performed by the so-called secondary jaw, consisting of paired maxillary and premaxillary integumentary bones. With their upper edges, they are attached to the underside of the primary jaw, which greatly strengthens the jaw apparatus. Teeth located on vomer and secondary jaw.

Rice. 30. Diagram of the structure of the skull of a bony fish

(the operculum and the periorbital ring have been removed).

Chondral bones are indicated by a dotted line:

1 - infero-occipital bone, 2 - lateral occipital, 3 - superoccipital, 4 - auricular, 5 - pterygosphenoid, 6 - oculosphenoid, 7 - interolfactory, 8 - lateral olfactory, 9 - parietal, 10 - frontal, 11 - nasal, 12 - parasphenoid , 13 – vomer, 14 – palatine, 15 – quadrate, 16 – pterygoid, 17 – premaxillary, 18 – maxillary, 19 – articular, 20 – dental, 21 – angular, 22 – hyomandibular, 23 – symplecticum, 24 – branchial arches, 25 – hyoid, 26 – copula

SKETCH

The basis lower jaw make up the integumentary bones - dental and angular. At the junction of the upper and lower jaws lies the chondral articular, which evolved evolutionarily from Meckel's cartilage. The jaw apparatus is attached to the hyoid arch through the jaw joint formed by the quadrate and articular bones.

Hyoid arch has the same components as those of cartilaginous fish - paired hyoids, pendants (hyomandibulare) and unpaired copula. However they bone and contain additional elements in the form symplecticum, which strengthens the connection between the jaws and the hyoid arch. With the help of pendants, both arches are attached to the brain skull (hyostyly).

Skeleton of the gill apparatus comprises four pairs of gills arcs, each of which includes twoupper and two lower element, connected joints. Gypsy Gills arcs (fifths), having only alone elements, merging with each other, contribute to better fastening of the gill apparatus as a whole. In some fish (cyprinids) they sit on these unpaired elements. pharyngeal teeth. Hyoid and gill arches are of chondral origin.

Gill cover, covering the gills, consists of four integumentary bones. Adjacent to the posterior edge of the pendant and the quadrate bone is a large preopercular bone. Connected to her opercular, interopercular and subopercular bones. These elements, like the operculum as a whole, vary significantly in size and shape among different species.

The musculoskeletal system consists of large quantity bones combined into a skeleton and a muscle layer. Skull of the majority aquarium fish mainly bone, consisting of cranium and movable maxillobranchial apparatus. The spine consists of a varying number of biconcave vertebrae, with a pair of processes on top, forming on top of everything spinal column the canal in which the spinal cord is located. In the trunk section of the spine, saber-shaped ribs covering the abdominal cavity are attached to the paired transverse processes of the vertebrae.

The skeleton and muscles are components of the musculoskeletal system.

The skeleton provides support for the body and organs of movement, protects the most important organs. Due to the work of muscles, movement is carried out.

The skeleton is divided into 4 sections:

• head skeleton (skull)
• torso skeleton
• limb belt skeleton
• fin skeleton

Skeleton of the head and torso

The basis internal skeleton fish make up the spine and skull. The spine of a fish consists of large number vertebrae. It distinguishes between the trunk and caudal sections.

The vertebrae of the trunk have a body, an upper and a lower arch. The upper arches, following each other, form a canal in which the spinal cord is located. The lower arches grow laterally in the form of two transverse processes. Ribs are usually attached to them.

The upper and lower arches of the vertebrae of the caudal region have the same structure. The lower arches of the vertebrae form a canal through which blood vessels pass.

In front, the spine is motionlessly connected to the skull, which consists of the braincase and bones that form the jaws, bones of the eye sockets and gill apparatus (gill arches and gill covers).
Some bones (shown in brown and yellow) are part of the skeleton of the pectoral girdle of the limbs.

Under the large gill covers, if you lift them, you can see the gill arches. Gill arches make up the skeleton breathing apparatus, i.e. serve as a support. They have gills.

Skeletons of unpaired and paired fins

The skeleton of unpaired fins consists of many elongated bones embedded in the thickness of the muscles. The skeleton of the paired fin consists of the skeleton of the belt and the skeleton of the free limb. The skeleton of the pectoral girdle is attached to the skeleton of the head (bones highlighted in brown and yellow).

The skeleton of the free limb (the fin itself) includes many small and elongated bones. The abdominal girdle is formed by one bone. The skeleton of the free pelvic fin consists of many long bones. The main muscles are located evenly in the dorsal part of the fish's body; The muscles that move the tail are especially well developed.

The swim bladder is a special organ found in almost all bony fish and develops as an outgrowth of the esophagus. It helps the fish stay at a certain depth, where the weight of the water displaced by the fish is equal to the weight of the fish itself. When a fish drops below this level, its body, experiencing greater external pressure from the water, contracts, squeezing the swim bladder. At the same time, the weight of the displaced volume of water decreases and becomes less than the weight of the fish and the fish begins to fall down. The lower it falls, the stronger the water pressure becomes, the more the fish’s body is compressed and the faster its fall continues. On the contrary, when ascending closer to the surface, the gas in the swim bladder expands and reduces the specific gravity of the fish, which pushes the fish even more towards the surface.