With the help of gills and the presence of fins. Fish that love fast currents (trout, grayling, brown trout, etc.) have a spindle-shaped body shape, while fish that live in calm water (carp, etc.) have compressed sides. This body shape allows them to move quickly among aquatic vegetation and turn vertically. But bottom-dwelling fish are inactive, and have a thick, round body, rarely flattened.
Despite the many different body shapes of fish, the most common are fish with a pointed head (without a neck), which imperceptibly passes into the body, and then into the tail. Here it is the gill section that marks the boundary between the head and the body, and the anus – the boundary between the body and the tail.
Different fish have different head shapes too.. There are also differences in the position of the mouth. For example, the mouth is adapted for taking food from the bottom (it can even extend like a proboscis), and the mouth is adapted for grasping prey. But the fish, which feeds near the very surface of the water on various falling insects, has an upper mouth.
And fish have teeth also very different. In addition to the sharp fangs on the lower jaw, the pike also has many sharp small teeth in its mouth (sloping inward to the mouth). And a fish that falls into the mouth of such a toothy predator is, of course, doomed. But in carp fish, the teeth are located in the throat itself. With the help of such teeth, fish can grind (crush) rough food.
Forward movement is achieved in a smooth manner with the help of the caudal fin, as well as wavy curves of the body. Other fins mainly perform guiding and coordinating functions: paired fins (pectoral and ventral) support the fish in a horizontal position and facilitate its turns. The unpaired fins (dorsal and caudal) are keels. The fins consist of bony rays with a membrane stretched over them. The sizes, shape, color and position of all fins vary widely among different fish.
Internal structure of fish
The presence of a swim bladder (hydrostatic organ) in fish allows them to stay in certain layers of water by changing their specific gravity: whether a fish floats or sinks depends on the volume of the swim bladder itself. But there are fish that do not have a swim bladder (for example, the goby), and in order for it to rise to the surface, great efforts have to be made.
The bodies of fish differ from each other not only in their shape, but also in color, which is adapted to the color and light conditions of the reservoir. Those fish that live in thickets of aquatic plants (hiding from enemies or using the vegetation themselves as an ambush site) have various stripes or spots on their bodies that make them less noticeable. Fish that swim closer to the surface of the water have a different, but also protective, coloration. Their back is usually dark - therefore they are less visible from above (for example, for birds), and their sides and belly are light, silver, they camouflage the fish when observed from below - protection from predatory fish. Bottom-dwelling fish have a peculiar dark body color, so they blend better with the background of the bottom. In this regard, the color of the flounder is most indicative: it can literally blend in color with the background of the bottom, and if necessary (for example, in another place), then change color to match the color of the bottom.
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1. What characteristic features do animals belonging to the chordate type have?
2. What distinguishes the lancelet from invertebrates?
3. How do cyclostomes differ from lancelets?
4. What are the characteristics of Cranial and Cranial chordates?
General characteristics. The chordate phylum includes bilaterally symmetrical animals with internal skeleton, which is represented by a strong axial rod - chord. Lower chordates– lancelet, lamprey, hagfish have a chord in the form of an elastic elastic cord located on the dorsal side of the body from the head to the tail.
Higher chordates– fish, amphibians, reptiles, birds, mammals (including humans) have a notochord in the embryonic state. As these organisms grow and develop, it is replaced by a cartilaginous or bony spine. The notochord or spine is the support for muscle attachment.
The nervous system is represented by a tubular cord lying above the notochord. In higher chordates, the neural tube in the anterior part expands and turns into the brain. The digestive system in the form of a tube is located under the notochord. Terrestrial chordates have gill slits during the early stages of embryonic development. The circulatory system of chordates is closed. Chordates are predominantly free-living organisms.
In the phylum chordates we will consider the subphylum Skullless and subtype Cranial, or Vertebrates.
Subtype Skullless. Class Lancelets
General characteristics. Only one class belongs to the skullless subtype - Lancelets. These are translucent, fish-like marine animals, ranging from 1 to 8 cm in length (Fig. 79). The body shape resembles a lancet surgical instrument (hence their name). To date, about 30 species of lancelets are known, living in temperate and warm seas. They are common off the coast of the Atlantic, Indian and Pacific oceans.
Typically, lancelets live at a depth of 10 to 30 m. They burrow into the sand, exposing the front part of their body with a mouth opening surrounded by tentacles.
Rice. 79. Lancelet
Lancelets filter water. Their food is plankton - single-celled animals and algae suspended in water. Lancelets are defenseless and have many enemies. Disturbed, they instantly leave the shelter, swim to another place and quickly burrow into the ground again. Most active at night.
The body of lancelets is laterally compressed, pointed at both ends, and lacks a separate head. They have no skull, the brain is not formed, and there are no paired fins. There is an unpaired dorsal fin that stretches along the back, passes into the caudal fin and ends on the abdomen. On the outside, lancelets are covered with skin containing a large number of glandular cells that abundantly wet the body with mucus. The muscle layer of this animal is located on the sides of the body and is divided by partitions into 50–80 segments. The internal skeleton consists of a notochord, above which there is a neural tube with light-sensitive cells. The sense organs are very poorly developed. The notochord and neural tube are covered by a common membrane. Lancelets are dioecious organisms. At night, when conditions are favorable for reproduction, sexually mature individuals spawn small eggs and sperm. Fertilization of eggs is external. The larvae emerging from the eggs float in the water column for 3 months. They become sexually mature at 2–3 years of age and live 3–4 years.
Lancelets serve as good food for many aquatic vertebrates. The Asian lancelet serves as a special fishery object. Local residents of Southeast Asia eat lancelets fried, boiled and dried. Up to 35 tons of lancelets are caught annually, which corresponds to 280 million individuals of these animals.
Subtype Cranial or Vertebrate
General characteristics. Vertebrates are a group of animals that have a head skeleton, or scull, And spine, consisting of vertebrae The skull and spine protect the brain and spinal cord, which was formed from the neural tube of the skullless.
In vertebrates, sensory organs become more complex. The organs of hearing and vision are especially improved. Numerous muscle groups provide significant mobility to animals, carried out mainly with the help of paired limbs. There is a heart that pumps blood through a closed circulatory system. Respiration of aquatic animals occurs with the help of gills, and of terrestrial animals with the help of real lungs.
There are about 40–45 thousand species of vertebrates. They live in water and on land, some of them are adapted to flight and an underground lifestyle. The subtype of vertebrates, or cranial fish, includes the following classes: Cyclostomata, Cartilaginous fish, Bony fish, Amphibians, Reptiles, Birds, Mammals.
Class Cyclostomes
General characteristics. Cyclostomes are the most primitive group of modern vertebrates. This class includes lampreys And hagfish. They do not have bone tissue in the skeleton and retain a notochord throughout their lives. The mouth is round and has the shape of a suction funnel. There are horny teeth and a powerful tongue (Fig. 80). Cyclostomes do not have jaws or limbs. On the sides of the head there are underdeveloped eyes; unlike all vertebrates, the olfactory organ in cyclostomes opens at the anterior end of one nostril (Fig. 81). In water, cyclostomes move by making worm-like movements. Bare skin is abundantly moistened with mucus. Lampreys and hagfish live in seas and fresh water bodies. To date, about 45 of their species have been described.
Cyclostomes prefer to be at the bottom of reservoirs; they are able to burrow into the ground, but can swim freely both at the surface and at depth.
Hagfish- sea creatures. Their body shape resembles large worms. Hagfish prey on marine invertebrates and fish. When attacking a fish, the hagfish gnaws through the body of the victim and then gets inside. All that remains of the fish is the skin and skeleton.
Rice. 80. Lamprey oral sucker
Rice. 81. Sea lamprey (A) and hagfish (B)
Chord. Scull. Spine. Vertebra. Skullless. Lancelets. Cranial, or Vertebral.
Questions
1. What is the most significant difference between lancelets and invertebrates?
2. What features of adaptation to life in water does the lancelet have?
3. Which previously studied animals does the lancelet resemble in appearance?
4. Is it possible to say that cyclostomes are extremely harmful animals?
5. Do representatives of cyclostomes live in your area?
6. What do the diets of lancelets and bivalves have in common?
Tasks
1. Using various sources of information, prepare a report about the larvae of lampreys - sandworms.
2. Prove that cyclostomes are not invertebrate animals.
VertebratesDo you know that…
Lancelet was first described in the 18th century. The discoverer of the lancelet, the Russian scientist P. S. Pallas, mistook it for a mollusk and called it a lanceolate slug. Only 60 years later it was clarified that the lancelet belonged to the chordates.
1. What are the distinctive features of fish?
2. What is the difference between cartilaginous fish and bony fish?
General characteristics. Fish are vertebrates that live only in water. Fish appeared more than 400 million years ago in the fresh waters of the continents, and then mastered sea salt water. Today, about 20 thousand species of fish are known, which differ in body shape, size and weight. Most of them have a cartilaginous or bony skeleton, a well-developed brain, a swim bladder, gills covered by gill covers, bony scales, paired pectoral and ventral fins.
Depending on the structure, nutrition, reproduction and lifestyle of fish, they were divided into 2 classes: Cartilaginous And Bone.
Cartilaginous fish. Most of them are permanent inhabitants of the marine environment; only a few species are found in fresh waters. Modern cartilaginous fish have retained a number of ancient features in their structure: a cartilaginous skeleton, gill slits, a transverse mouth opening on the underside of the head, and a number of others.
Bony fish- the most numerous group of fish that lives in the seas and oceans, in rivers and lakes, in permanent and temporary reservoirs. They make up 96% of all modern fish on Earth. The body shape is varied (Fig. 82): elongated (pike, pike perch, cod), circular (angelfish, sunfish), torpedo-shaped (burbot, catfish, swordfish), flattened, leaf-shaped (flounder, halibut), serpentine (moray eel , loach, eel).
The most common fish are from the following orders: herring-shaped: oceanic herring, iwasi herring; salmoniformes: chum salmon, pink salmon, salmon, omul, taimen; carp-shaped: roach, ide, crucian carp, tench, bream, roach, ram; pike-like: common pike; perciformes: perch, pike perch, mackerel, tuna; cod: cod, navaga, haddock, burbot.
The excellent adaptability of bony fishes to various conditions of the aquatic environment, developed in the process of long evolution, allowed them to populate a variety of water bodies. Some fish have even adapted to live in underground waters.
Rice. 82. Fish body shapes
The body of most fish has an elongated shape (Fig. 83). The head, pointed at the front, is fused with the body, which starts from the free edge of the gill covers and ends with the anal fin. Next comes the tail section.
Rice. 83. External structure of fish
The outside of the fish skin is covered scales. Scales their ends overlap each other, arranged in a tile-like manner, in rows (Fig. 84). The resulting cover protects fish from mechanical damage. The scales can be microscopic, such as in the conger eel. The barbels living in the rivers of India have very large scales, the size of a palm.
The skin of fish contains various glands, such as mucus-secreting and poison-secreting glands; some fish have luminous cells. The secreted mucus helps reduce friction and promote rapid movement in the water.
The internal skeleton of bony fishes consists of bones the head, forming the skull, spine, skeleton of paired and unpaired fins. Paired fins - pectoral and ventral - ensure the horizontal position of the fish, perform turns, and facilitate upward and downward movement. Caudal, dorsal, anal - unpaired fins. The caudal fin carries out forward movement and serves as a rudder when changing direction.
Rice. 84. Different shapes of fish scales
Rice. 85. Internal structure of perch
The digestive system consists of the mouth, oral cavity, pharynx, esophagus, stomach, intestines, digestive glands - liver and pancreas, anus (Fig. 85).
swim bladder Many bony fish have. Bottom-dwelling fish and fish that perform rapid vertical movements in water do not have a swim bladder. The bubble is filled with a mixture of gases. Increasing the volume of the bubble reduces the density of the body and promotes free movement to the surface of the water. Reducing the volume increases the density of the body and makes it easier to dive.
The respiratory organs of fish are gills (see Fig. 157, B). They are located on both sides of the head of the body and are covered with gill covers. Gills carry out gas exchange between water and the body's circulatory system. The breathing process is carried out thanks to the movement of water washing the gills. The pumping of water into the oral cavity and pushing it out is carried out by the gill covers and the mouth opening. The circulatory system is closed. Consists of the heart and one circle of blood circulation. The heart is two-chambered, consists of an atrium and a ventricle and is located in the anterior part of the body.
The excretory organs of fish are the kidneys, located under the spine in the form of ribbons (see Fig. 167).
The reproductive organs of fish are paired ovaries in females and testes in males. Fish are dioecious. The ovaries form eggs - eggs, testes - sperm. Fertilization in most bony fishes is external, in water. Females lay eggs, males lay milk containing sperm.
The nervous system is primitive. The parts of the brain are arranged linearly and are characterized by small sizes (see Fig. 176). For example, in pikes the brain makes up 1/3000 of the total body weight.
The sense organs are represented by the organs of vision, hearing, smell, and touch. The organs of vision are the eyes, located on the sides of the head and adapted to clearly see objects at close range.
The hearing organ of fish is represented by the inner ear - a labyrinth located in the back of the skull.
Lateral line of fish- a kind of organ that perceives the direction and speed of the flow (see Fig. 177). It is clearly visible from the side and stretches from the front end of the body to the back.
The olfactory organs are represented by two olfactory, blindly closed pits located at the tip of the muzzle. The bottom and walls of the nasal fossae are equipped with nerve endings. Fish perceive different odors in water.
The taste organs of fish are located in the mouth, in the skin and even in the tail. Fish distinguish between bitter, sweet, sour, salty, and those with pre-oral antennae, such as catfish and burbot, recognize the taste of food without touching it.
Economic importance of fish big for a person. Fish is a valuable food product; it serves as one of the main sources of dietary protein. Every year, 70–74 million tons of fish are caught in the seas and oceans and about 9 million tons in fresh water bodies. Fish oil, a healing product for humans, contains vitamin D. It is obtained from the liver of some fish, such as cod. The fins and swim bladder of sturgeons serve as a source of glue production.
Laboratory work No. 7
External structure and movement of fish
Equipment:
demonstration aquariums (2–3 pcs.), aquarium fish. Microscopes, carp scales.
Progress:
1. Look at the swimming fish in the aquarium.
Note what the fish's body shape is; Is the body of the fish evenly colored? is the lateral line visible? what is the position of the mouth; are there scales? Note the arrangement of paired and unpaired fins; on the nature of the movement of the fins when the fish stands still; when it moves (it’s better to look from above); on the synchronicity of the movements of the mouth and gill covers; is there a connection between them; what is the attitude of individuals of different species to a sharp wave of the hand at the glass, knocking on the glass; what is the nature and speed of movement of fish at the moment of fright.
2. Examine the scales of the fish under a microscope.
3. Write conclusions from observations about the structure and movement of fish.
Cartilaginous fish. Bony fish. Scales. Swim bladder. Side line.
Questions
1. What is the structural feature of all bony fish?
2. How do bony fish differ in external and internal structure from previously studied chordates?
3. What is a lateral line?
Tasks
2. Compose a reminder for tourists vacationing on the coast of seas and oceans, where sharks, moray eels and other dangerous fish live.
3. Observing the behavior of fish in the aquarium, try to develop in them a conditioned reflex to knocking. Note the time it takes for the reflex to develop. Watch it fade away. Discuss the significance of the formation and extinction of conditioned reflexes in the life of fish.
Do you know that…
Predatory fish, such as pike, pike perch, perch, and catfish, have a large mouth equipped with sharp teeth. Plankton-eating fish, such as herring, have a medium-sized mouth without teeth. Carp, bream, asp and a number of other fish do not have teeth in their mouths and chew food with pharyngeal teeth, which received this name for their location.
1. What are the similarities and differences between cartilaginous fish and cyclostomes?
2. Are all sharks dangerous to people?
Cartilaginous fish include sharks, rays and chimaeras. Their skeleton is not bone, but cartilage. There are no operculums, and there are 5–7 gill slits on each side. There is no swim bladder.
Shark Squad. Sharks include fish with an elongated torpedo-shaped body and a length from 20 cm to 20 m (Fig. 86). For example, the midget shark from the group prickly, living in the Gulf of Mexico, does not exceed a length of 20 cm in adulthood. Whale shark, 18–20 m long and weighing about 10 tons, it is a giant among all the fish that currently exist on our planet.
Rice. 86. Sharks
Rice. 87. Structure of a shark
The skin of sharks is rough, covered with scales and numerous denticles and teeth. The scales have the appearance of rhombic plates with a sharp spine curved at the top. The paired pectoral and pelvic fins are located horizontally and allow the fish to move down or up. The upper lobe of the caudal fin is usually longer than the lower one. Forward movement and turns are carried out by bending the caudal fin to the left or right. There are underdeveloped eyes on the head, capable of seeing objects only in black and white. Sharks breathe using gills. Their gill arches are studded with gill filaments with a richly branched circulatory system (Fig. 87).
Herring sharks- rather large fish, have an equal-lobed caudal fin, with the exception of sea fox, and are viviparous. They are distributed in the Atlantic and Pacific oceans, in their temperate and subtropical waters.
There are many sharks that are dangerous to humans. Having an excellent sense of smell and a system for detecting the slightest vibrations in water, sharks quickly appear where people swim or there is the smell of blood. Some species of sharks can attack people. The most dangerous are sharks brindle, blunt-nosed, hammer, gray And large white(Fig. 86, 88).
Rice. 88. Hammerhead shark
Sharks live in the seas and oceans, as well as in the South American rivers of the Atlantic coast.
Squad Stingray. These are relatively large fish, some of them reach a width of 6–7 m and a weight of 2.5 tons (Fig. 89). The smallest of them, for example dipterous stingray, lives in the Yellow Sea and is 10–15 cm wide. The largest representative of the order is manta ray having a mass of about 2.5 tons and belonging to the family broad devils. Representatives of most species lead a benthic lifestyle and have mastered both shallow waters near the coast and significant depths (up to 2700 m). Large rays, such as manta rays, live in the water column.
Adaptations to bottom existence are reflected in the general body structure of stingrays. Their body is flat, flattened in the dorsal-ventral direction, diamond-shaped - with fused pectoral fins expanded on the sides. The caudal fin has the appearance of an elongated thin whip. In bottom-dwelling fish, the eyes are located on the upper side of the head. The transverse mouth and five pairs of gill slits are located on the ventral side. The skin of some stingrays is smooth, but many of them have scales and spines similar to those of a shark. The scales of stingrays are called dermal teeth. The skin, which does not have scales or spines, is protected by mucus produced by the skin glandular cells.
Rice. 89. Stingrays
Rice. 90. European chimera
Order Chimeraformes. This order includes a small, unique, predominantly deep-sea group of sedentary cartilaginous fish (Fig. 90). Their body has a powerful anterior section, gradually turning into a thin posterior caudal fin, which ends in a thread-like appendage. Body length ranges from 60 cm to 2 m. The skin is bare. About 30 species of chimera are known. They live in the seas of the Indian, Atlantic and Pacific oceans.
The most famous type is European chimera, or sea cat, found in the Barents Sea at a depth of over 1000 m. In the moderately calm zones of the Pacific and Atlantic oceans they live Nosed chimeras. Chimera-like creatures have no commercial significance: their meat is considered inedible. The fat extracted from the huge liver is used in medicine, and in some industries it is used as a lubricant.
Cartilaginous fish: sharks, rays.
Questions
1. Why are sharks and rays considered the most primitive fish?
2. What is the importance of sharks and rays in nature and human life?
Tasks
Prove that sharks and rays are relatives of lancelets. What do they have in common?
Do you know that…
The gray shark family is common in warm waters. Among them, the soup shark is considered commercial. Its fins are used to prepare a delicious soup.
Shark meat is eaten, but the liver and fins are especially valued. The liver of some species contains up to 60–75% fat and many vitamins. Beautiful products are made from shagreen, a specially tanned shark skin.
Some species of stingrays have electrical organs. The discharge lasts 0.03 s, but there is rarely just one, usually there are from 12 to 100 of them in a row with a voltage of up to 220 V. Electric rays are inactive and usually lie at the bottom, buried in the silt.
The weapons of other species of stingrays are needles or spines on the tail. They are often poisonous, causing muscle cramps in the victim and a drop in blood pressure.
We continue our traditional section Tips from experienced fishermen - today we present material explaining the structure and shape of the fish’s body, and its movements:
Navigation: About fish - organs, instincts
The structure of the body of fish and the shape of their body are adapted for living in water. Water is many times denser than air, and moving around in it is not so easy. Gradually, over many generations, fish developed special devices that facilitate movement, and developed special techniques that allow them to swim easily and quickly. The movement is greatly facilitated by the mucus that covers the body of the fish. All fish are characterized by a streamlined body shape, gill breathing, and the presence of fin-shaped limbs. The most perfect form is spindle-shaped - in fish that make long voyages, rise up the river against currents, or in fish that stay with the current. A body of this shape allows asp, trout and some other fish to easily overcome rapids and swim without getting tired for a long time.
Sedentary bottom fish have a round, thick body, sometimes flattened from top to bottom, and a darker color (catfish, burbot). And in fish that live in calm water (bream, crucian carp, carp, roach, etc.), the body is laterally compressed. This helps them move among aquatic plants and turn in a vertical plane.
In most fish, the pointed head imperceptibly (without a neck) passes into the body, and the latter into the tail section. The boundary between the head and the body is marked by gill slits, and between the body and the caudal peduncle is the anus.
Fish also differ in the position of their mouth. In bream, for example, it is adapted to take food from the bottom (its mouth can even extend into a tube), in pike it is adapted to grab prey, and in sabrefish, which feeds on falling insects at the very surface of the water, it has an upper mouth. In cyprinids, teeth are located in the pharynx; they help them crush rough food.
The body of the fish is equipped with fins: unpaired (dorsal and caudal) and paired (pectoral and abdominal). Located on the back and under the tail are the keels. The forward movement is carried out by the caudal fin, as well as by the wave-like bends of the body. Paired fins support the fish in a horizontal position and facilitate its turns (Fig. 1). In the movement of fish in the vertical direction, the swim bladder filled with gases is of great importance. A change in the volume of the swim bladder causes the fish to float or submerge. But some species of fish do not have a swim bladder, so they have to make great efforts to rise to the upper layers of water (for example, eels).
The body color of fish is always adapted to the color and light conditions of the reservoir. This is why sometimes the same species of fish has different shades of color in different bodies of water.
Fish that live in thickets of aquatic plants have spots or transverse stripes on their bodies, making them less noticeable against the background of algae (perch, pike). Upland fish are painted in dark colors from above, making them difficult to see from above, where their constant enemies - birds - live. The silvery-white sides and belly camouflage the fish when viewed from below, from where predators can attack it. But bottom-dwelling fish have a dark color that blends with the background of the bottom.
The body shape of fish is so diverse that it is impossible to give it a general description. When we pronounce the words “bird” and “beast,” we immediately imagine in the first case an animal with wings, in the second – with four legs. But about fish we can only say that it lives in water, but its body shape is amazingly diverse.
This is the law of the aquatic environment: if you want to live in water, learn to swim. It is easier to swim when the body has an oblong shape. Many fish have this exact shape. The spiny shark, whose body shape is similar to a submarine or torpedo, rushes quickly and deftly, covering long distances in herds. Other torpedo-shaped fish - salmon, mackerel - are also excellent swimmers. Well, fish with a worm-like or snake-like body shape (lamreys, eels) swim over long distances, twisting their bodies.
Less adapted to fast swimming are the so-called bottom-dwelling fish, with a flat (stingray) or laterally compressed (flounder) body.
The body, which has a spindle-shaped body, when encountering danger, inflates to such an extent that it becomes like a ball or bubble. In this form, it stays on the surface, turning upside down, the spines of its body spread out, like a hedgehog’s, and serve as reliable protection from enemies. And the terrifying appearance of this scarecrow with bared sharp jaws instills fear in attackers. When the danger has passed, the box throws out air from its stomach, falls down, and its body again takes on a spindle-shaped shape.
The body can be found in our Far Eastern Primorye. The length of this fish is up to 25 centimeters. Sometimes the boxfish is called a pufferfish.
The tropical seas are home to giant sunfish weighing more than 1000 kilograms and over 2 meters long. Her body is round, like the moon on a full moon, compressed from the sides.
The tail is almost invisible, as if chopped off, the dorsal and sub-caudal fins are high. The sunfish leads a pelagic lifestyle, that is, it swims in the water column. There is no detailed information about her life yet.
Off the coast of Australia there is a fish whose body shape surprisingly resembles seaweed. This fish received the ironic name “sea rag-picker”. When you look at a seahorse - a “rag picker”, you get the impression that it is all hung with rags, ribbons and threads of various lengths, painted in the colors of the algae among which this miracle of nature feeds and hides. This body shape makes the fish invisible among the algae and saves it from numerous enemies. The length of the sea rag picker is up to 25 centimeters.
Table 2. Aquarium fish
The shapes of aquarium fish are also amazing, look at table 2. It’s probably hard for you to believe that the ancestor of all the fish depicted is the common crucian carp, they are so different from their ancestor! Look at the fins. One of the fish has a tail fin similar to a rooster's tail, another one is like a grass panicle, the black fish resembles a tulip, and the top one on the right has a tail like a fan.
Goldfish, the varieties of which are presented in the table, were bred from crucian carp by aquarists in China and Japan. Among domesticated crucian carp, specimens with unusual fins or original coloring could appear, just as white ones with a peculiar tail shape sometimes appear among rock pigeons. They began to breed offspring from such special crucian carp. For a long time, over many years, those crucian carp were selected and bred that aquarists liked for their color, body shape, fins and tail. This is how the goldfish was eventually developed. This took decades. It is curious that in Japan there are families that maintain a hundred-year continuity in breeding aquarium fish. In general, the Japanese are big fans of aquarium fish.
There are many passionate aquarists in our country. I remember that shortly before the war, during the filming of a popular science film about fish, I visited the apartment of a Leningrader, a big fan of aquarium fish. Along the walls of the rooms there were aquariums with amazing fish of all shapes and colors. I felt as if I had entered a magical underwater kingdom. Many of the film's scenes were filmed here. The picture turned out to be interesting; there was a trial viewing of it. But before the siege of Leningrad, the film was transported to Detskoye Selo, and during its occupation by the Germans, the film disappeared.
The most common body shape is fusiform. Fish of this shape have a laterally compressed body and a slightly pointed head. The spindle-shaped shape is characteristic of most fish, such as roach, perch, and herring. Fish with a spindle-shaped body live in the surface layers, in the water column and at the bottom, in coastal and open areas of water bodies.
Torpedo-shaped (often called spindle-shaped) - characterized by a pointed head, a rounded body with an oval shape in cross section, a thin caudal peduncle, often with additional fins. It is characteristic of good swimmers capable of long movements - tuna, mackerel, sharks, etc. Arrow-shaped - the bones of the snout are elongated and pointed, the body of the fish has the same height along the entire length, the dorsal fin is assigned to the caudal fin and is located above the anal, which creates an imitation of the plumage of an arrow . This form is typical for fish that do not move long distances, stay in ambush and develop high speeds of movement for a short period of time due to the push of the fins when throwing at prey or avoiding a predator. These are pikes (Esox), armored pikes (Lepisosteus), garfish (Belone), etc. Symmetrically laterally compressed body - strongly compressed laterally, tall with a relatively short length and tall. These are fish of coral reefs - bristletooths (Chaetodon), thickets of bottom vegetation - angelfish (Pterophyllum). This body shape helps them easily maneuver among obstacles. Some pelagic fish also have a symmetrically laterally compressed body shape, which need to quickly change position in space to disorient predators - vomer (Vamer) or to camouflage themselves in the water column when stalking prey - sunfish (Zeus). The sunfish (Mola mola L.) and bream (Abramis brama L.) have the same body shape. The body is asymmetrically compressed from the sides - the eyes are shifted to one side, which creates an asymmetry of the body. It is characteristic of bottom-dwelling, sedentary fish of the order Pleulonectiformes, helping them to camouflage well on the bottom.
The wave-like bending of the long dorsal and anal fins plays an important role in the movement of these fish. All these fish, except the black halibut (Reinchardtius hippoglossoides Walb), swim on one side of the body. The body, flattened in the dorsoventral direction, is strongly compressed in the dorsoventral direction; as a rule, the pectoral fins are well developed. Sedentary bottom fish have this body shape - most stingrays (Batomogrha), monkfish (Lophius piscatorius L.). The flattened body camouflages fish in the bottom conditions, and the eyes located on top help to see prey. For large stingrays - sea devils of the Mobulidae family, living in the pelagic zone, protection from predators is not their body shape, but their large size. Eel-shaped - the body of the fish is elongated, rounded, looking like an oval in cross section. The dorsal and anal fins are long, there are no ventral fins, and the caudal fin is small. It is characteristic of such benthic and demersal fish as eels (Anguilliformes), which move by laterally bending their body. Ribbon-shaped - the body of the fish is elongated, but unlike the eel-shaped form it is strongly compressed from the sides, which provides a large specific surface area and allows the fish to live in the water column. Their movement pattern is the same as that of eel-shaped fish. This body shape is characteristic of the saberfish (Trichiuridae), the herring king (Regalecus). Macro-shaped - the body of the fish is high in the front, narrowing in the back, especially in the tail. The head is large, massive, the eyes are large. Characteristic of deep-sea, sedentary fish - macrurus, chimera-like fish (Chimaeriformes). Asterolepid (or body-shaped) - the body is enclosed in a bony shell, which provides protection from predators. This body shape is characteristic of benthic inhabitants, many of which are found in coral reefs, such as the Ostracion. The spherical shape is characteristic of some species from the order Tetraodontiformes - ball fish (Sphaeroides), hedgehog fish (Diodon), etc. These fish are poor swimmers and move with the help of undulating movements of their fins over short distances. When in danger, fish inflate the air sacs of their intestines, filling them with water or air; At the same time, the thorns and thorns present on the body are straightened, protecting them from predators. The needle-shaped body shape is characteristic of pipefish (Syngnathus). Their elongated body, hidden in a bony shell, imitates the leaves of zoster, in the thickets of which they live. Fish lack lateral mobility and move using the undulating action of the dorsal fin.
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