ganoid and bone, and ganoid and bone are derivatives of the most ancient placoid scale (Fig. 4).
placoid scale, consisting of a rhombic plate lying in the dermis, and a spike protruding outward, covers the body of cartilaginous fish and is repeatedly replaced during their life.
The scales consist of organic matter impregnated with lime - dentin, which does not contain cellular elements. Outside, the spike is covered with a dense enamel-like substance - vitrodentin. The cavity of the tooth is filled with dental pulp - a pulp formed by loose connective tissue with blood vessels.
Rice. 4. The structure of various types of fish scales:
A - placoid; B - ganoid; B - bone: a - herring; b - bream; in - perch; g - scales (in section).
Some of the placoid scales grow strongly, forming placoid plaques, such as in the sea fox. All spines in cartilaginous fish are modified placoid scales.
Rice. 5. Placoid scales of cartilaginous fish.
ganoid scale has a rhombic shape and a lateral protrusion in the form of a tooth, with the help of which the scales are connected to each other, forming a kind of shell. This scale is characteristic of bony ganoids, multifeathers, is preserved on the tail of sturgeons and consists of three layers: the upper compacted (ganoin), the middle one, containing numerous tubules (cosmine), and the lower one, consisting of bone substance (isopedin). A variety of ganoid scales is cosmoid in lobe-finned fish (without the upper layer of ganoin).
Rice. 6. Cycloid scales of bony fish
bone scales was formed as a result of the transformation of the ganoid - the layers of ganoin and cosmine disappeared and only the bone substance remained. According to the nature of the surface, two types of bone scales are distinguished: cycloid with a smooth trailing edge (herring, carp) and ctenoid, the rear edge of which is armed with spines (perch).
There are three layers in the bone scales - the upper transparent shiny structureless, the middle integumentary and the lower main. The lower layer is composed of thin bone plates underlying one another. The growth of the scales occurs in such a way that under the small first plate, which is laid in the fry, on next year another is laid - a larger one, etc. Thus, the smallest and oldest record is on top, and the largest and youngest is below. The number of plates in the lower layer corresponds to the age of the fish. Above the lower main layer is an integumentary, mineralized layer with ribs, or sclerites.
With intensive growth, wide and distant sclerites with high ridges are formed on the cover layer, and with slower growth, narrow and close sclerites with low ridges are formed.
To determine the age of the fish, the surface layer of the scales with sclerites is studied. The zones of convergence of sclerites (usually darker) are called annual rings and their counting allows you to determine the age of the fish.
poison glands . Some fish have venom glands in the epidermis, located mainly at the base of the spines or spiny rays of the fins. Sometimes poisonous cells are formed and function only during reproduction, in other cases - constantly. Three types of venom glands are distinguished in fish (Fig. 7). The most primitive of them are separate cells of the epidermis containing poison and scattered at the base of the spines of the fins and spines of the gill cover (stargazer).
In other fish species, a complex of poisonous cells (stingray-stingray) is formed in the epidermis near the spines and spines. And finally, in many species, poisonous cells form an independent multicellular poisonous gland near spines and spines. strong poison(sea dragon, scary wart, sea bass)
In a stingray, when stabbed, the poison enters the wound through the groove of the thorn and causes acute pain, severe swelling, chills, nausea and vomiting, and in some cases death occurs.
The most powerful poison is produced in the poisonous glands of the terrible wart. It destroys red blood cells nervous system and leads to paralysis. If poison enters the bloodstream, death soon occurs. Fish that have a specialized poisonous apparatus are called toxic, and fish with poisonous organs and tissues are poisonous. The most poisonous fish are considered to be from the order of the symtomaxillaries, in which the gonads, liver, intestines, and skin contain a neurotoxin (tetrodotoxin) that can cause rapid death, since it is 10 times more toxic than curare poison. The meat of these fish is edible and in some countries (Japan) is highly valued, which often leads to fatal poisoning.
Rice. 7. The main types of poisonous glands in fish:
A - unicellular glands of the epidermis of the fin spine; B - a complex of unicellular glands of the epidermis of the caudal spike of the stingray; 5 - compact multicellular gland of the gill cover of the sea dragon; 1 - epidermis; 2 - mucous cells; 3 - glandular cells; 4 - supporting cells; 5 - false excretory duct; 6 - protruding poison; 7-thorn; 8 - poison gland.
Of the fish living in the waters of the Russian Federation, the caviar and milk of marinka and osman are poisonous. Lamprey mucus is also poisonous. However, those fish that, as a result of injury or poor-quality storage, become infected with toxic microbes (including botulinum) should not be classified as poisonous, and the consumption of which can lead to poisoning.
Luminous Organs. The luminous organs (photophores) of many deep-sea fishes consist of luminous cells (photocytes) containing a special substance, luciferin. Luminous photophore cells are derivatives of the glandular epidermis.
The structure of photophores, their location and emitted light are different. In luminous anchovies, for example, a cluster of luminous cells located in the muscle cavity is underlain by black pigment cells covered with a shiny layer that acts as a reflector. In front of the luminous cells there is a transparent, modified scale that acts as a lens. Some photophores have a diaphragm that allows you to change the direction and intensity of light.
Rice. 8 Glowing Organs deep sea fish, located in the form of crescents under the eyes
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4. Kotlyar O.A., Mamontova R.P., Course of lectures on ichthyology. – M.: Kolos, 2007.
5. Moiseev P.A., Azizova N.A., Kuranova I.I. Ichthyology: Textbook.-M.: Legk. and food. industry, 1981.- 384 p.
6. Naumov N.P., Kartashev N.N. Zoology of vertebrates. - Part 1. - Lower chordates, jawless, fish, amphibians: A textbook for biol. specialist. Univ. - M .: Higher School, 1970. - 333 p., ill.
7. Skornyakov V.I., Apollova T.A., Mukhordova L.L. Workshop on ichthyology: Textbook. - M.: Agropromidat, 1986.- 270 p.
Who is the most famous aquatic inhabitant? Of course, fish. But without the scales, her life in the water would be almost impossible. Why? Find out from our article.
Fish without scales practically do not exist. In some species, it covers the entire body from the head to the dorsal fin, in others it stretches parallel to the spine in separate stripes. If the scales are not visible at all, this means that it is reduced. It develops in the dermis, or corium of the skin, in the form of bone formations. This forms a dense protective cover. Examples of such fish are catfish, burbot, snake fishermen, sterlet, sturgeon and lamprey.
The scales of fish are bone or cartilaginous. Half of its chemical elements are inorganic substances. These include mineral salts, namely phosphates and carbonates of alkaline earth metals. The remaining 50% are organic substances represented by connective tissue.
Performing the same functions, skin derivatives differ in their origin and chemical composition. Depending on this, several types of scales are distinguished. In representatives of the class Cartilaginous, it is placoid. This species is the most ancient in its origin. The skin is covered with ganoid scales. In bone, it looks like scales that overlap one another.
This type of fish scale has been found in fossil species. Among modern species its owners are rays and sharks. These are diamond-shaped scales with a clearly visible spike that protrudes outward. Inside each such unit is a cavity. It is filled with connective tissue, permeated with blood vessels and neurons.
Very durable. In stingrays, it even turns into spines. It's all about its chemical composition, the basis of which is dentin. This substance is the basis of the plate. Outside, each scale is covered with a vitreous layer - vitrodentin. Such a plate is similar to the teeth of fish.
Loop-finned fish are covered with ganoid scales. It is also located on the tail of sturgeons. These are thick rhombic plates. Such fish scales are interconnected with the help of special joints. Their combination can be a solid shell, scutes or bones on the skin. On the body, it is located in the form of rings.
This type of scale got its name from the main component - ganoin. This is a shiny substance that is a shiny layer of enamel-like dentin. It has significant hardness. Below is the bone. Thanks to this structure, placoid scales perform not only a protective function, but also serve as the basis of the muscles, giving the body elasticity.
Bone scales, which are monogenic in composition, are of two types. Cycloid covers the body of herring, carp and salmon. Its plates have a rounded rear edge. They overlap each other like tiles, forming two layers: cap and fibrous. Nutrient tubules are located in the center of each scale. They grow with a cap layer along the periphery, forming concentric strips - sclerites. From them you can determine the age of the fish.
On the plates of the ctenoid scale, which is also a type of bone scale, small spikes, or ridges, are located along the posterior edge. It is they who provide the hydrodynamic abilities of fish.
Everyone knows that annual rings on the trunk can determine the age of a tree. There is also a way to determine the age of fish by scales. How is this possible?
Fish grow throughout their lives. In summer, the conditions are more favorable, since there is enough light, oxygen and food. Therefore, during this period, growth is more intense. And in winter, it slows down significantly or stops altogether. The activation of the metabolic process also causes the growth of scales. Its summer layer forms a dark ring, while its winter layer forms a white one. By counting them, you can determine the age of the fish.
The formation of new rings depends on a number of factors: fluctuations in temperature, amount of food, age and type of fish. Scientists have found that in young and mature individuals, rings form in different time of the year. For the first, it happens in the spring. Adult individuals at this time only accumulate substances by the summer period.
The period of formation of annual rings also depends on the species. For example, in young breams this happens in the spring, and in mature breams in the fall. It is also known that annual rings are also formed in fish. tropical zone. And this is despite the fact that the seasons of the year, fluctuations in temperature and the amount of food are absent here. This proves that annual rings are the result of a combination of several factors: environmental conditions, metabolic processes and humoral regulation in the body of fish.
It would seem that what could be unusual in scales? In fact, in many fish it has unique characteristics. For example, coelacanth scales on the outside have a large number of bulges. This makes the fish look like a saw. No modern view has a similar structure.
A goldfish is called so because of the scales. Actually this decorative form The first goldfish were bred in the 6th century in China by Buddhist monks. Now more than 50 breeds of this species are known with red, golden and yellow coloring.
At first glance, the eel is a fish without scales. In fact, it is so small that it is almost invisible. It is also difficult to feel it to the touch, as the skin of the eel secretes a large amount of mucus and is very slippery.
So, the scales of fish is a derivative of the skin. It is one of the features of the structure, which provides adaptation to life in the aquatic environment. Depending on the chemical composition, placoid, ganoid and bone scales are distinguished.
Fish are permanent residents aquatic environment. The body of most fish is streamlined and covered with scales. The scales perform a protective function and from physical damage in the water, because the skin of the fish itself is very thin, and on the outside it is covered with a layer of mucus, which is secreted by the skin glands.
Fish without scales practically do not exist. In some species, it covers the entire body from the head to the dorsal fin, in others it stretches parallel to the spine in separate stripes. If the scales are not visible at all, this means that it is reduced. It develops in the dermis, or corium of the skin, in the form of bone formations. This forms a dense protective cover.
Fish without scales are forbidden by the Jews. The holy scripture "Torah" states that only species with fins and a lamellar coating can be eaten. Fish without scales are compared to dirty reptiles like molluscs.
There are several explanations for this. The first has to do with the impure nature of the species. Fish without scales, as a rule, burrow into the silt and feed on carrion. The second explanation is the toxicity of many "naked" inhabitants of water bodies. There is also an ethical dimension. Fish without scales repulsive in appearance. Those who serve the Creator should not eat such things. The combination of these factors has led to the “recording” of naked fish in non-kosher products along with pork, shrimp, black pudding. So, a complete list of fish without scales.
Burbot is a member of the cod family. Its peculiarity lies in the fact that, unlike other species of this family - the inhabitants of the sea, burbot constantly lives and breeds only in freshwater reservoirs.
Young individuals of burbot have a dark gray color in black speck , and then brighten with age and acquire a yellowish tint, in addition, the quality of the water has a significant effect on the color. It is also believed that burbot remotely resembles catfish. On his back he has two fins (small and large), on his chin there is a characteristic mustache, the body is covered with small scales deeply seated in the skin and a large amount of mucus. As for size, individuals are known that have reached 2 meters in length and a mass of 30 kg, but this is the exception rather than the rule. On average, the weight of an adult burbot is in the range of 1 to 2 kilograms. At the same time, males can barely grow to half the weight of their females.
Burbot is a widespread fish. It can be found in a number of European countries, in countries North America and of course in Russia. The main habitats of burbot are rivers flowing into the Arctic Ocean. Sometimes it appears in the lower reaches of the rivers of the Caspian and Black Sea basins.
In sufficient quantities, burbot is found in the reservoirs of the Leningrad region, here it can be found almost everywhere, in particular in the lakes Ilmen, Ladoga, Onega, Pskov-Chudskoye, as well as in the Neva and other rivers flowing into the Gulf of Finland. The largest individuals are found in the Irtysh, on the Ob and in the Pechora.
Burbot prefers clean and cold water rivers and lakes with rocky, sometimes covered with silt, bottom. It does not like fast currents, therefore it reaches its maximum size in flat areas. northern rivers and flowing lakes.
The most comfortable water temperature for burbot is no more than 12°C, when it rises to 15°C, the fish goes to the most protected places from sunlight and falls into a kind of hibernation, during which it may not hunt for up to several weeks.
The sturgeon has an elongated, spindle-shaped body. The snout is short, blunt. The antennae are located closer to the end of the snout than to the mouth. The lower lip is interrupted. There are 27-51 rays in the dorsal fin, 18-33 in the anal fin. Dorsal scutes - 8-18, lateral - 24-50, abdominal - 6-13. The body between the rows of scutes is covered with stellate plates, sometimes small bone plates are scattered between the scutes.
Coloration varies greatly. Usually the back is grayish-black, the sides of the body are grayish-brown, the belly is white. A large sturgeon reaches (in the past) in the Black Sea a length of 236 cm and a mass of 115 kg, and in the Caspian, respectively, 215 cm and a mass of 65 kg. The maximum size of the sturgeon, judging by the analysis of archaeological materials, is 300 cm, and life expectancy can reach 50 years. Today, the average commercial weight of the Volga sturgeon is 12-16 kg, the Kura sturgeon 22-24 kg and the Azov sturgeon 15 kg.
The Russian sturgeon is characterized by a complex intraspecific structure: it has winter and spring forms, and within each there are smaller groups that differ in terms of entry into rivers, fish sizes, duration of stay in fresh water, etc.
The sturgeon is an anadromous fish, although in the past the Middle and Upper Volga may have been inhabited by a small, resident, slow-growing form. In the sea, adult sturgeon feed mainly on shellfish fields at depths of 2 to 100 m, juveniles at depths of 2 to 5 m. In addition to mollusks, fish are also found in the stomachs of sturgeons: in the Black Sea - gobies, anchovy, sprat, in the Caspian - gobies and sprats.
Sexual maturity in most males occurs at the age of 11-13 years, in females - at 12-16 years. In the Sea of Azov, they usually mature 2 years earlier than other populations. For spawning from the Caspian, it enters the Volga, to a lesser extent the Urals, in very small numbers it enters the Terek, Sudak, Samur, along the Iranian coast into the Sefidruzh and occasionally into the Gorgan, Babol and other rivers. The spawning migration of sturgeon to the Volga stretches from late March - early April to November with a maximum in July. Fish of a later course winter in the river. Spawning of spring sturgeon in the Volga occurs in mid-May - early June at a water temperature of 8 to 15°C.
Moray eels are a genus of ray-finned fish from the moray family. Found in the Atlantic, Pacific and Indian Oceans, widely distributed in the Mediterranean and Red Seas.
They have a length of up to 1.5 meters and a mass of up to 50 kg, but, as a rule, there are individuals about a meter long. The body is serpentine, the skin is naked, without scales. The color of moray eels is very diverse, helping them to disguise themselves: brown, green, greenish-yellow, spotted, striped, "marble".
Moray eels live in the bottom layer of water, one might say, at the bottom. During the day, they sit in crevices of rocks or corals, sticking their heads out and usually moving them from side to side, looking for passing prey. At night, moray eels get out of their shelters to hunt. Usually they feed on fish, but they attack both crustaceans and octopuses, which they catch from ambush, jumping out of their shelters with an arrow and grabbing a victim swimming by.
Moray eel meat after processing can be eaten. It was especially valued by the ancient Romans. A fish bite can be dangerous to humans. Previously, their teeth were considered poisonous, but this data has not been confirmed. However, a moray eel sting is extremely painful. There are cases of fish attacks on scuba divers.
Catfish is the largest predatory fish that lives in freshwater lakes and rivers. It belongs to the class of ray-finned fish, the catfish order, the catfish family.
Catfish is quite widespread in the water bodies of Europe and Asia, while living in rivers flowing into the seas, it often swims into their salty waters. Unfortunately, in such conditions, only one species of catfish, the channel catfish, can exist for a long time, the rest of the individuals from this family are not adapted to such a “salty” life.
The catfish fish has a long, flattened and rather powerful body, which is devoid of scales and covered with a layer of mucus, which provides gliding and maneuverability of the fish in the water. The wide head of the catfish usually has a flattened shape. On it are small, slightly blind eyes of a catfish. The wide mouth of the fish is "armed" with small, but present in large numbers of teeth. Almost all catfish have one feature: long mustaches are located on the jaws of this predatory fish. Catfish's whiskers are the most important tactile organ with which the fish finds food. Depending on the species, which scientists number about 500, the appearance of the catfish, its color and size can vary significantly.
Catfish in nature prefers to lead a bottom lifestyle, lying in pits with a large accumulation of silt deposits. In nutrition, he is unpretentious: catfish happily eats plant remains, small fish, larvae, frogs, shells, crayfish, or birds, mice and other animals that accidentally fall into a pond. Catfish also feed on carrion. Often he "hunts" prey near old and forgotten fishing nets. A large hungry catfish can even eat a dog or a calf that accidentally entered the water.
There are many interesting and unusual representatives in the catfish family.
Catfish in the aquarium
Common catfish (European) can reach a length of up to 5 meters and weigh up to 400 kg. It lives in the rivers and lakes of Europe and Russia. Cases of common catfish attacks on people are described.
Numerous aquarium varieties are widely known among catfish: ancistrus catfish, tarakatum, platidoras, glass catfish, cuckoo catfish, shifter catfish and others. And their variety of colors is simply amazing.
Golomyanka is a small unusual fish that lives in Lake Baikal. It is slightly pink, transparent or translucent, and besides, it prefers deep waters and the bottom. But the lucky ones managed to film her moving under the ice near the surface of the lake several times. The fish belongs to endemics- local small species that live only in this area.
It is noteworthy that this Baikal fish of the Golomyankovye family does not have scales and consists of fat by one third. This compensates for her lack of a swim bladder. Both large and small species (Dybovsky's golomyanka; named after the naturalist Benedikt Dybovsky, who discovered the fish in 1830) are most often found at a depth of 0.5 to 0.25 km, but also live deeper - up to 1.6 km.
In addition to the sizes, which gave the basis for the names of the species, there are a number of distinguishing features:
The method of catching food is the opening of the mouth and frequent biting. The main diet of golomyanka is planktonic crustaceans of Baikal waters (cyclops, Jurassic amphipods, epishura). Large individuals often trade in cannibalism in their families or among young gobies. Interestingly, the golomyanka goes up for food at night, and during the day it hides from predators like omul or seal closer to the bottom. If, after a storm, the fish is washed ashore, it becomes the prey of local birds.
The Baikal golomyanka is viviparous, it does not spawn, does not spawn and does not migrate. All this is incredible, because in cold waters, populations survive only on eggs. But the oily fish managed to overcome the forces of nature and become a legend of Baikal.
Before giving birth, she rises to the mark where plankton lives in order to provide food for the offspring. It was believed that the fish most often died during childbirth, but later studies have refuted this assumption. A large species breeds at the end of summer (the water is as warm as possible) and until mid-autumn. The small species prefers spring. The presence of travelers and swimmers does not bother the fish. In the process of childbirth, up to 2500 larvae appear at a time big view and about 1500 small larvae. The sexual cycle is usually one-time.
Alepisaurus is a large predatory fish belonging to the Alepisaurus family. The appearance of this creature is truly awesome. With its large mouth with large dagger-shaped fangs, the fish resembles a daggertooth. And the huge fin makes Alepisaurus look like a sailfish.
Alepisaurus are truly creepy creatures. Only one mouth with teeth is worth something. But there is still a fish body, the length of which can reach up to two meters. The body itself is narrow, its front part is slightly flattened from the sides, and the tail part has a cylindrical shape. Yes, by the way, the scales of this fish are really completely absent.
The back of the alepisaurus is adorned with a huge fin that stretches along the entire body. If the fin is straightened, then it is twice as tall as its owner. The color of the fanged fish is also gloomy - black-gray-blue. There is very little information about the reproduction of these representatives of marine fauna. But given that alepisaurs are not averse to eating their fellows sometimes, it can be assumed that they are generally hermaphrodites, and each individual has both female and male organs.
The first mention of this sea monster dates back to 1741. Then the description of the alepisaurus gave famous member Georg Wilhelm Steller of the second Kamchatka expedition, who was lucky enough to see a copy of a hitherto unknown fish thrown ashore by a wave. Then the traveler called his find Plagyodontis. On that study of this marine life and ended.
Only in 1811 did interest in the alepisaurus awaken again. This time, the zoologist Peter-Simon Pallas, taking Steller's drink and the find dried by him as a basis, compiled a detailed description of the fish, highlighting a separate genus for it - Plagyodum. Later, the name was transformed into Alepisaurus ferox, which is translated from Greek as "lizard", "scaleless beast".
Like many deep-dwelling fish, alepisaurs practice daily vertical migrations. At night, they try to move closer to the surface, and during the day they return to the depths. Such "walks" are associated with the movement of food, for which alepisaurs use various types of fish and crustaceans. If food is very tight, then predatory fish will not disdain their smaller relatives.
Big White shark known to many as the man-eating shark, or carcharodon. This animal belongs to the class of cartilaginous fish and the herring shark family. Today, the population of this species slightly exceeds three thousand individuals, so the great white shark belongs to the category of predatory animals that are on the verge of extinction.
The length of the largest of all modern predatory sharks is eleven meters or a little more. The most common are individuals with a body length of not more than six meters, and a mass in the range of 650-3000 kg. The back and sides of the white shark have a characteristic gray coloration with slight brownish or black tones. The surface of the ventral part is off-white.
It is known that white sharks existed relatively recently, the body length of which could reach thirty meters. In the mouth of such an individual, living at the end of the Tertiary period, eight adults could freely settle down.
Modern white sharks lead a predominantly solitary lifestyle. Adults can be found not only in the waters of the open ocean, but also along the coastline. As a rule, the shark tries to stay close to the surface, and prefers warm or moderately warm ocean waters. Prey is destroyed by the white shark with the help of very large and wide, triangular teeth. All teeth have jagged edges. Very powerful jaws allow the aquatic predator to bite through not only cartilaginous tissues, but also rather large bones of its prey without much effort. Hungry white sharks are not particularly picky about their food choices.
The dominance of females over males prevails, and the largest individuals over smaller sharks. Conflict situations in the process of hunting are resolved by rituals or demonstrative behavior. Fights between individuals of the same population are certainly possible, but are quite rare. As a rule, sharks of this species in conflicts are limited to not too strong, warning bites.
A distinctive feature of the white shark is the ability to periodically raise its head above the water surface in the process of hunting and searching for prey. According to scientists, in this way the shark manages to capture smells well even at a considerable distance.
Navaga is a cold-loving sea fish, it belongs to the cod family. There are two types of this fish, the northern saffron cod and the Far East, known as wahnya. The body length of saffron cod usually reaches 30 cm, its weight at this length is 250 grams, there are also larger individuals, up to half a meter in length, weighing about 1 kg. The Far Eastern wahnia is much larger than the northern saffron cod.
The body of the saffron cod has a more rounded appearance than that of other cod fish, the head is smaller in size, the fish is distinguished by the peculiarity of the structure of the spine - there are peculiar swellings on its short ribs. The upper jaw of the fish is longer than the lower jaw, with a single barbel on the lower jaw. There are many dark spots on the brown-gray back of the saffron cod. The sides of the fish are lighter than the back, the belly is white. The belly of the Far Eastern wahna is also painted in White color, but the color of its back is greenish-gray, the sides are silver-violet.
Navaga can be found from the White Sea to the Gulf of Ob, the Far Eastern wahna lives in the Chukchi, Bering, Okhotsk, and Japan Seas. Navaga is not found in the open sea; it is a coastal fish. In spring, when the water on the coast becomes too warm, it moves away from the coast for a short distance in search of colder water. In the autumn-winter period, navaga flocks move closer to the coast, shoals of Far Eastern navaga often enter lakes and river mouths. Navaga belongs to the bottom fish
Navaga is a predator, it feeds on caviar and juveniles of other fish, crustaceans, and various worms. In the spring, when the fish is forced to look for cold water, its food is not enough, as cold weather sets in, the navaga returns closer to the shore for fattening.
Sea eel is a fish of the eel family. Latin name this fish Conger conger. There is also a second name for the sea eel - conger.
A person who sees an eel for the first time may confuse it with a ribbon sea snake, which is very poisonous. This is quite understandable due to the long cigar-shaped body and three fins fused into one (dorsal, caudal and anal fins). The small head of an eel with large oval eyes and a wide mouth complete the resemblance between an eel and a snake. The outer teeth of the eel, which form the cutting edge, are well developed. Gill openings in the form of slits reach the abdominal part. Immediately behind them are the pectoral fins. Completely devoid of scales, the skin of the eel is abundantly covered with a layer of mucus secreted by special glands.
The color of eels does not differ in particular variety and is dictated by the need for camouflage during hunting. Therefore, most often conger eels are painted in various shades of gray, black, brownish or greenish. Sometimes there are specimens with contrasting spotted coloring. Sea eels are much larger than their freshwater relatives and can reach a length of up to 3 m and weigh up to 100 kg.
The distribution area of conger eels is quite wide and includes the warm waters of the Indian, Pacific and Atlantic Oceans and adjacent seas. Some types of conger eels tolerate colder waters better and can be found in the Mediterranean and North Atlantic. In the Northern, Baltic and Black Sea sea eel fish swim quite rarely. These fish are inhabitants of both the coastal zone and the open sea, not sinking deeper than 500 m.
Eels are nocturnal and prefer to sleep in a secluded place during the day. By nature, they are voracious predators with powerful teeth. The basis of the diet is small fish, crustaceans and molluscs. They will not miss the catch entangled in fishing nets. Not having good eyesight, eel fish prefer to lie in wait for prey in ambush, because thanks to their excellent sense of smell, they can feel it from afar. There are types of eels that disguise themselves as bottom vegetation. A vertical hole in the ground with the help of a strong tail and leaning halfway out of it, conger eels are waiting for prey. In case of danger, they immediately hide in the hole completely.
As a rule, pearl fish are called fish from the carapace family, which belong to the lecheper. The history of the name of this group of living organisms is quite fascinating. One day, one of the pearl divers discovered a translucent snake-like creature inside the shells of an oyster. The fish managed to turn into mother-of-pearl during its stay in the "house", which gave the false impression that it itself has a pearl color.
Depending on the degree of independence of their existence, one can distinguish:
In 1977, a New Zealand biologist recorded about 15 species of these fish, most of which lived in the body of a sea cucumber.
Carapaces live in the tropical waters of such oceans:
The depth of habitat is quite high and can reach a couple of kilometers. A typical dwelling is located in the region of ocean slopes and a gently sloping bottom.
Due to their tiny size and the almost complete lack of means of repelling aggression, these fish are forced to spend a significant part of their lives inside other organisms more.
And only with the onset of darkness does their time come, and they swim out of the body of the owner in order to feed.
This fish is practically unsuitable for food due to its tiny mass and lack of any useful substances. However, it is possible that there is a risk of eating it by mistake along with the organism in which it lives.
Loach is a freshwater River fish class of ray-finned, order of cyprinids, family of loaches, genus of loaches. The fish was named loach because it has a certain feature of squirming like a snake.
The length of some types of loaches reaches 30 centimeters, but on average these fish do not exceed 15-18 centimeters. Loaches are covered with small but noticeable scales. The body is elongated, serpentine in shape. Loach is a peeping fish: if you pull it out of the water, it will wriggle and squeak very strongly. The caudal fin of a fish of the loach family is small and has a rounded shape. The mouth has 6 to 12 antennae. The nostrils are extended into small tubes.
Unlike females, males have a thickened and elongated second ray of the pectoral fin. And also there is a thickening on the sides, behind the dorsal fin, which is formed by adipose tissue. The life expectancy of loaches is about 10 years.
The loach lives in the waters of Europe, as well as the South and East Asia. This fish can live in any freshwater reservoir where there is silt or mud. Loach is a fish that adapts very easily to the environment. If the reservoir dries up, these fish burrow into the mud and wait for the moment when it rains and their habitat is filled with water again.
The most common types of loaches:
Loach fish feed on insect larvae, small mollusks, worms, crustaceans and even silt. Also, the loach is considered a well-known thief of someone else's caviar. He spends all the time at the bottom, so it will not be difficult for him to find caviar.
The spawning of loaches lasts from April to June. The female loach is very prolific, she spawns 11,000-38,000 eggs. After 7-8 days, larvae hatch, the length of which does not exceed 5 mm. With the help of gluing organs, the larvae attach themselves to plants. The young loach grows quite quickly, in the first year of life it reaches 4 cm in length, and at 3 years the length of the fish is already about 13 cm. The ability to reproduce in loaches occurs at 3 years.
Among the wide variety of the fish world, the division into aquatic inhabitants covered with scales and some species without it is common. Common religions (Judaism, Islam) forbid eating fish without scales. This is because many scaleless water creatures are scavengers, and some of them are poisonous. In this article, we will consider which fish do not have scales.
A dense layer of bony plates forms a shell that protects the insides from high pressure water. The scaly shell protects the body from being injured by hard and sharp stones. Scales play a role in camouflage of fish in algae and against the background of the bottom landscape. Greenish and silvery shades of color reduce the visibility of the individual in the water layers and sunlight.
Sometimes representatives of the water element do not have a scaly cover. Scaleless fish is a generic name for all species, even those with small scales, like a shark. In some fish, for example, in sturgeons, the remnants of the scales are represented by a number of bone plates.
A fish that does not have scales is often a bottom cleaner of a reservoir from the cadaveric remains of various organisms, as well as a predator that performs a sanitary function to free water expanses from sick or old individuals. A far from complete list of scaleless species includes the following names:
The largest predatory river fish without scales is catfish. It belongs to the class of ray-finned fish. The body of the catfish is long, flattened and powerful, covered with mucus for maneuverability and gliding. Contrary to the common belief that catfish do not have scales, its skin is covered with inconspicuous microscopic scales. A wide head with a large mouth ensures quick swallowing of prey.
The catfish does not have good eyesight - its lack is replaced by a mustache that performs a tactile function. Catfish lead a bottom life, living in muddy pits. They feed on any living creatures, not disdaining carrion. Cases of their attacks on birds, small animals and even people have been recorded.
Predators are nocturnal, falling into hibernation for the winter. The historical weight of the record holder of this species reached 400 kg, and the length - up to 5 meters. But now there are rarely catfish more than 100 kg. Good gastronomic qualities contribute to the massive catch of catfish, which does not allow them to live to a possible 80 years.
- a small river bottom fish that lives in stagnant muddy ponds overgrown with dense algae. Near swampy reservoirs, you can hear the squeak of a loach that has risen to the surface for a portion fresh air. The loach can live in places where, due to the lack of oxygen, no other individual lives.
It can survive dry times by burrowing deep into the mud and hibernating until rainy weather arrives. The length of the bindweed does not exceed 30 cm, and the weight is 150 g. They feed on larvae, worms, crustaceans, mollusks and detritus. The caviar of other species of loaches is eaten so actively that they can completely exterminate other individuals in the reservoir.
The fish has a serpentine shape, therefore it is distinguished by amazing resourcefulness. Some loaches crawl large areas of land from one body of water to another. Bindweed is called a living barometer: before bad weather, it protrudes up to 15 times per minute on the surface of the water. The Japanese predict earthquakes and tsunamis by the behavior of loaches.
Sturgeon is a popular marine fish in industrial production. Variety and species of sturgeons include dozens of commercial fish.
On the elongated body of sturgeons, the scales sit in the form of five rows of spikes, between which there are bone plates. There are no scales on the rest of the body. The elongated, cone-shaped head has fleshy lips with four barbels and a toothless retractable jaw. The cartilaginous skeleton is a chordate invertebrate structure.
For spawning, sturgeons enter the same shallow freshwater reservoirs. Sturgeons are highly prolific - adults can lay up to a million eggs. They sometimes overwinter in fresh waters. Sturgeon species feed on mollusks and small fish: sprat, anchovy, gobies.
Many scientists consider the absence of scales to be a loss in some species in the course of evolution, while others believe the device of the outer cover is a protective function of the body, developed by necessity in a particular way of life and exposure to the external environment.
The long, serpentine bodies of scaleless fish require not so much lamellar skin protection as an abundance of mucus for maneuverability and the impossibility of being captured by predators. For the same purpose, mucus is sometimes poisonous.
The shell created by the scales is necessary when the fish lives near stones, so as not to injure the body, and also serves as a defense against predators. And if the fish lives in spacious water layers or at the muddy bottom, the scales lose their significance. Each species evolves according to its natural needs.
"Scaly world" - so we lovingly call the fish. But which of us was more closely involved in these remarkable outward signs many fish, from pike to carp? Is the structure of scales in fish of all species the same? Are there fish without scales? What does scales tell us about fish and what is its role?
Based on scientific definition, scales are the skin of most fish, which is formed in the subcutaneous layer and consists of bone plates. So, in any case, it is written in zoological books. The scales of our local fish have a complex structure. Basically, it consists of a transparent integumentary layer and an underlying bony layer of the base. It is reinforced with cartilage fibers and is characterized by so-called growth rings, which are interrupted in the radial direction so that the scales remain flexible.
There are different types of scales. We are primarily interested in large groups of round and comb scales. Shark placoid scales are not true scales. The so-called ganoid scale consists of a ganoid layer covered with bony plates, which is therefore not a true fish scale.
In ichthyology, round scales are divided into six types.
The scales of some fish are formed so characteristically that they can be used to identify their owner. In the eructation of cormorants, for example, along with fish bones, undigested scales are encountered. Her research provides fairly accurate information about the food spectrum of fish-eating birds. The large, silvery, shiny scales of the “white” fish are noteworthy. In fish of some species, it is very thin and, like bleak, falls off very easily when touched. The scales of such fish, which have a silvery sheen, are used to make artificial pearls. Characteristic is the hard golden-shiny round scales of the carp or the large “mirror” scales of its breeding forms. The reticulated pattern of scales in the chub is an important identification feature of this species.
Ganoid scales are found in perch fish such as river perch, or walleye. It is small, firmly attached to the skin and has small teeth. The side of the scales sticking out from under the skin is jagged, so these fish seem rough to the touch. Round and ganoid scales form a tiled covering of the surface of the body of fish. Thanks to its ideal position, it does not impede the movement of fish when swimming and is also sufficient protection against damage. Under the scales is the integumentary skin. It contains mucous cells that form a smooth, closed mucous layer. If the scales are very small, like eels or tenches, the mucous layer is strengthened. Scaleless fish like catfish are very slimy. Their skin is tight. And the color cells are located here on top of the scaly layer. When the scales are removed, the fish lose their beautiful coloration, only the main tone under the skin, gray or green, remains.
In summer, fish grow (and scales grow with them) faster than in winter, so that distinct annual rings form on the scales, which can be used to determine the age of the fish. By the time of spawning, growth slows down, which leaves traces on the scale rings. From an enlarged image of a single scale, experts can learn a lot about the life history of a fish.
Scale formation occurs in fish at a young age. The number of scales during her life remains the same. The scales grow evenly with the fish. The scales lost as a result of wounds are quickly restored. The newly formed scales grow very quickly, but often the harmonious original scaly appearance is no longer achieved. In the scar tissue of the skin, scales most often grow at random.
Some scales, especially those located along, are striking. There they have clearly visible openings, thanks to which the sense organs lying under the scales make contact with water. In fish of some species, similar scales are located outside the lateral line. Outwardly very similar cyprinids such as the Danube roach and ide, whitefish (madder) or golden and silver carp can be accurately distinguished by the number of scales along their lateral line.
Scales in some areas also have a mystical meaning. Some people put a Christmas carp scale in their wallet every year so that it never gets empty.
