Fish - inhabitants of the aquatic environment
Fish live in water, water has a significant density and it is more difficult to move in it than in the air.
What should fish be like to survive in the aquatic environment?
Characteristic for fish:
Buoyancy
Streamlining and sliding:
Imbricated scales
Germicidal slime
The fastest fish is sailfish.She swims faster than a cheetah runs.
The speed of the sailfish is 109 km/h (the cheetah is 100 km/h)
Merlin – 92 km/h
Fish - wahoo - 77.6 km/h
Trout is 32 km/h faster than pike.
Madder – 19 km/h faster
Pike - 21 km/h
Crucian carp – 13 km/h
The silvery-white color of the fish and the shine of the scales largely depend on the presence of guanine in the skin (an amino acid, a breakdown product of proteins). The color varies depending on the living conditions, the age, and the health of the fish.
Protection from predators - dark back and light belly
Sense organs of fish
The eyes of a fish can only see close range due to the spherical lens, close to the flat cornea, which is an adaptation to vision in an aquatic environment. Typically, the eyes of a fish are “set” for vision at a distance of 1 m, but due to the contraction of smooth muscle fibers, the lens can be pulled back, thereby achieving visibility at a distance of up to 10-12 m.
2) German ichthyologists (scientists who study fish) found that fish distinguish colors well, incl. and red.
Flounder avoid red, light green, blue and yellow nets. But the fish probably don’t see gray, dark green and blue nets.
2) The olfactory organs are paired sacs in the front of the skull. They open outward with their nostrils. The sense of smell in fish is 3-5 times finer than in dogs.
Fish can detect the presence of vital substances at a distance of 20 km. Salmon catches the scent of its native river from a distance of 800 km from its mouth
1) A special organ runs along the sides of the fish - the lateral line. It serves as an organ of balance and for orientation in space.
Many fish make sounds.
The scienes purr, grunt, and squeak. When a flock of scienae swims at a depth of 10-12 m, a moo is heard
Naval midshipman - hisses and croaks
Tropical flounders make harp and bell ringing sounds
Talk like a fish:
Dark crucian carp - Khryap-khryap
Light croaker - three-three-three
Sea cock - track-track-track or ao-ao-hrr-hrr-ao-ao –hrr-hrr
River catfish - oink-oink-oink
Sea crucian carp - quack-quack-quack
Sprat - oo-oo-oo-oo-oo
Cod - tweet-chirp-chirp (quietly)
Herrings whisper quietly (tsh - tsh-tsh)
With all the diversity of fish, they all have a very similar external body structure, since they live in the same environment - aquatic. This medium is characterized by certain physical properties: high density, the action of the Archimedean force on objects immersed in it, illumination only in the uppermost layers, temperature stability, oxygen only in a dissolved state and in small quantities.
The BODY FORM of fish is such that it has maximum hydrodynamic properties that make it possible to overcome water resistance to the greatest extent. Efficiency and speed of movement in water is achieved the following features external structure:
Streamlined body: pointed front part of the body; there are no sharp transitions between the head, body and tail; there are no long branched outgrowths of the body;
Smooth skin covered with small scales and mucus; the free edges of the scales are directed backward;
The presence of fins with a wide surface; of which two pairs of fins - chest and abdominal - real limbs.
RESPIRATORY SYSTEM - gills having a large gas exchange area. Gas exchange in the gills is carried out by diffusion of oxygen and carbon dioxide gas between water and blood. It is known that in an aquatic environment the diffusion of oxygen is approximately 10,000 times slower than in air. Therefore, fish gills are designed and work to increase the efficiency of diffusion. Diffusion efficiency is achieved in the following way:
Gills have a very large area of gas exchange (diffusion), due to the large number gill filaments on each gill arch ; every
the gill filament, in turn, is branched into many gill plates; good swimmers have a gas exchange area 10 - 15 times larger embroiders the surface of the body;
The gill plates are very thin-walled, about 10 microns thick;
Each gill plate contains a large number of capillaries, the wall of which is formed by only one layer of cells; the thinness of the walls of the gill plates and capillaries determines the short diffusion path of oxygen and carbon dioxide;
A large amount of water is pumped through the gills due to the work of " gill pump"in bony fishes and ram ventilation- special breathing method in which the fish swims with open mouth and open gill cover; ram ventilation - predominant mode of respiration in cartilaginous fish ;
Principle counterflow: direction of water movement through the gills the plates and the direction of blood movement in the capillaries are opposite, which increases the completeness of gas exchange;
Fish blood contains hemoglobin in its red blood cells, which is why blood absorbs oxygen 10 to 20 times more efficiently than water.
The efficiency of fish extracting oxygen from water is much higher than that of mammals from the air. Fish extract 80-90% of dissolved oxygen from water, and mammals extract only 20-25% of oxygen from inhaled air.
Fish living in conditions of constant or seasonal lack of oxygen in water can use oxygen from the air. Many species simply swallow the air bubble. This bubble is either retained in the mouth or swallowed. For example, carp have highly developed capillary networks in the oral cavity, which receive oxygen from the bladder. The swallowed bubble passes through the intestine, and from it oxygen enters the capillaries of the intestinal wall (in loaches, loaches, crucian carp). Famous group labyrinth fish who have a system of folds (labyrinth) in the oral cavity. The walls of the labyrinth are abundantly supplied with capillaries, through which oxygen enters the blood from a swallowed air bubble.
Lungfish and lobe-finned fish have one or two lungs , developing as a protrusion of the esophagus, and nostrils that allow air to be inhaled with the mouth closed. Air enters the lung and through its walls into the blood.
Interesting features of gas exchange in Antarctic icy, or white-blooded fish that do not have red blood cells and hemoglobin in the blood. They effectively diffuse through the skin, because the skin and fins are abundantly supplied with capillaries. Their heart is three times heavier than that of close relatives. These fish live in Antarctic waters, where the water temperature is about -2 o C. At this temperature, the solubility of oxygen is much higher than in warm water.
The swim bladder is a special organ of bony fish that allows you to change the density of the body and thereby regulate the depth of immersion.
BODY COLOR largely makes the fish invisible in the water: along the back the skin is darker, the ventral side is light and silvery. From above the fish is invisible against the background of dark water, from below it merges with the silvery surface of the water.
The physical properties of water in the life of fish are enormous. The conditions of movement and fish in the water depend to a large extent on the width of the waters. water. The optical properties of water and the content of suspended particles in it affect both the hunting conditions of fish that navigate with the help of their visual organs, and the conditions for their protection from enemies.The swim bladder determines its specific gravity, and therefore its affinity to certain layers of water. Only a few fish that live in the water column do not have a swim bladder. Sharks and some mackerel do not have a swim bladder. These fish regulate their position in one or another layer of water only with the help of the movement of their fins.
The aquatic lifestyle of different groups of these species is very different. We can divide all deep-sea fish into two groups: ancient or true deep-sea and secondary deep-sea. The first group includes species belonging to such families, and sometimes suborders and orders, all representatives of which have adapted to living in the depths. The adaptations to the deep-sea lifestyle of these fish are very significant. Due to the fact that living conditions in the water column at depths are almost the same throughout the world's oceans, fish belonging to the group of ancient deep-sea fish are often very widespread. (Andriyashev, 1953) This group includes anglers - Ceratioidei, luminous anchovies - Scopeliformes, largemouths - Saccopharyngiformes, etc. (Fig. 9).
The second group, secondary deep-sea fish, includes forms whose deep-sea origins are historically more recent. Typically, the families to which species of this group belong include mainly fish. distributed within the continental stage or in the pelagic zone. Adaptations to life at depths in secondary deep-sea fish are less specific than in representatives of the first group, and their distribution area is much narrower; There are no worldwide widespread among them. Secondary deep-sea fish usually belong to historically younger groups, mainly perciformes - Perciogtea. We find deep-sea representatives in the families Cottidae, Liparidae, Zoarcidae, Blenniidae and others.
If in adult fish a decrease in specific gravity is ensured mainly by the swim bladder, then in fish eggs and larvae this is achieved in other ways (Fig. 10). In pelagic eggs, i.e. eggs developing in the water column in a floating state, a decrease in specific gravity is achieved due to one or several fat drops (many flounder), or due to the watering of the yolk sac (red mullet - Mullus), or by filling a large circular yolk - perivitelline cavity [grass carp - Ctenopharyngodon idella (Val.)], or swelling of the membrane [eight-tailed gudgeon - Goblobotia pappenheimi (Kroy.)].
The percentage of water contained in pelagic eggs is much higher than that of bottom eggs. Thus, in the pelagic eggs of Mullus, water makes up 94.7% of the live weight, in the bottom eggs of the silverside lt; - Athedna hepsetus ¦ L. - water contains 72.7%, and in the goby - Neogobius melanostomus (Pall.) - only 62 ,5%.
Pelagic fish larvae also develop peculiar adaptations.
As you know, the larger the area of a body in relation to its volume and weight, the greater the resistance it has when immersed and, accordingly, the easier it is for it to stay in a particular layer of water. Similar adaptations in the form of various spines and outgrowths, which increase the surface of the body and help retain it in the water column, are found in many pelagic animals, including
In other pelagic larvae, the role of a hydrostatic organ is played by the dorsal fin fold, which expands into a huge swollen cavity filled with liquid. This is observed, for example, in the larvae of sea crucian carp - Diplodus (Sargus) annularis L.
Life in flowing water is associated in fish with the development of a number of special adaptations. We observe especially fast flows in rivers, where sometimes the speed of water reaches the speed of a falling body. In rivers originating from mountains, the speed of water movement is the main factor determining the distribution of animals, including fish, along the stream bed.
Adaptation to life in a river along the current occurs in different representatives of the ichthyofauna in different ways. Based on the nature of the habitat in a fast stream and the adaptation associated with this adaptation, the Hindu researcher Hora (1930) divides all fish inhabiting fast streams into four groups:
^1. Small species that live in stagnant places: in barrels, under waterfalls, in creeks, etc. These fish, by their structure, are the least adapted to life in a fast flow. Representatives of this group are the fast grass - Alburnoides bipunctatus (Bloch.), lady's stocking - Danio rerio (Ham.), etc.
2. Good swimmers with a strong wavy body that can easily overcome fast currents. This includes many river species: salmon - Salmo salar L., marinka - Schizothorax,
Fish, less than any other group of vertebrates, are associated with a solid substrate as support. Many species of fish never touch the bottom in their entire lives, but a significant, perhaps most, fish are in one or another connection with the soil of the reservoir. Most often, the relationship between soil and fish is not direct, but is carried out through food objects adapted to a certain type of substrate. For example, the association of bream in the Aral Sea, at certain times of the year, with gray silty soils is entirely explained by the high biomass of the benthos of this soil (the benthos serves as food for the bream). But in a number of cases there is a connection between the fish and the nature of the soil, caused by the adaptation of the fish to a certain type of substrate. For example, burrowing fish are always confined in their distribution to soft soils; fish, confined in their distribution to rocky soils, often have a suction cup for attaching to bottom objects, etc. Many fish have developed a number of rather complex adaptations for crawling on the ground. Some fish, which are sometimes forced to move on land, also have a number of features in the structure of their limbs and tail, adapted to movement on a solid substrate. Finally, the color of fish is largely determined by the color and pattern of the soil on which the fish is located. Not only adult fish, but bottom - demersal eggs (see below) and larvae are also in very close connection with the soil of the reservoir on which the eggs are deposited or in which the larvae are kept.
There are relatively few fish that spend a significant part of their lives buried in the ground. Among cyclostomes, a significant part of their time is spent in the ground, for example, the larvae of lampreys - sandworms, which may not rise to the surface for several days. The Central European thornbill, Cobitis taenia L., also spends considerable time in the ground. Just like the sandmoth, it can even feed by burying itself in the ground. But most fish species burrow into the ground only in times of danger or when the reservoir is drying up.
Almost all of these fish have a snake-like elongated body and a number of other adaptations associated with burrowing. Thus, in the Indian fish Phisoodonbphis boro Ham., which digs passages in liquid mud, the nostrils have the form of tubes and are located on the ventral side of the head (Noga, 1934). This device allows the fish to successfully make its moves with its pointed head, and its nostrils are not clogged with silt.The burrowing process is carried out through undulating movements
bodies similar to the movements that a fish makes when swimming. Standing at an angle to the surface of the ground with the head down, the fish seems to be screwed into it.
Another group of burrowing fish have flat bodies, such as flounders and rays. These fish usually don't burrow that deep. Their burrowing process occurs in a slightly different way: the fish seem to throw soil over themselves and usually do not bury themselves entirely, exposing their head and part of the body.
Fish that burrow into the ground are inhabitants of predominantly shallow inland reservoirs or coastal areas of the seas. We do not observe this adaptation in fish from the deep parts of the sea and inland waters. Of the freshwater fish that have adapted to burrowing into the ground, we can mention the African representative of the lungfish - Protopterus, which burrows into the ground of a reservoir and falls into a kind of summer hibernation during drought. Among the freshwater fish of temperate latitudes, we can name the loach - Misgurnus fossilis L., which usually burrows when water bodies dry up, and the spiny loach - Cobitis taenia (L.), for which burying in the ground serves mainly as a means of protection.
Examples of burrowing marine fish include the sand lance - Ammodytes, which also burrows into the sand, mainly to escape persecution. Some gobies - Gobiidae - hide from danger in shallow burrows they have dug. Flounders and stingrays also bury themselves in the ground mainly to be less noticeable.
Some fish, burrowing into the ground, can exist for quite a long time in wet silt. In addition to the lungfish noted above, common crucian carp can often live in the mud of dry lakes for a very long time (up to a year or more). This was noted for Western Siberia, Northern Kazakhstan, and the south of the European part of the USSR. There are known cases when crucian carp were dug out from the bottom of dry lakes with a shovel (Rybkin, 1*958; Shn"itnikov, 1961; Goryunova, 1962).
Many fish, although they do not burrow themselves, can penetrate relatively deep into the ground in search of food. Almost all benthic-eating fish dig up the soil to a greater or lesser extent. They usually dig up the soil with a stream of water released from the mouth opening and carrying small silt particles to the side. Direct swarming movements are observed less frequently in benthivorous fish.
Very often, digging up soil in fish is associated with the construction of a nest. For example, nests in the form of a hole, where eggs are deposited, are built by some representatives of the family Cichlidae, in particular, Geophagus brasiliense (Quoy a. Gaimard). To protect themselves from enemies, many fish bury their eggs in the ground, where they
undergoes its development. Caviar developing in the ground has a number of specific adaptations and develops worse outside the ground (see below, p. 168). As an example of marine fish that bury eggs, the silverside Leuresthes tenuis (Ayres.) can be mentioned, and among freshwater fish, most salmon, in which both eggs and free embryos develop in the early stages, being buried in pebbles, thus protected from numerous enemies. For fish that bury their eggs in the ground, the incubation period is usually very long (from 10 to 100 or more days).
In many fish, the shell of the egg, when it gets into the water, becomes sticky, due to which the egg is attached to the substrate.
Fish that live on hard ground, especially in the coastal zone or in fast currents, very often have various organs of attachment to the substrate (see page 32); or - in the form of a sucker formed by modifying the lower lip, pectoral or ventral fins, or in the form of spines and hooks, usually developing on the ossifications of the shoulder and abdominal girdles and fins, as well as the gill cover.
As we have already indicated above, the distribution of many fish is confined to certain soils, and often close species of the same genus are found on different soils. For example, the goby - Icelus spatula Gilb. et Burke - is confined in its distribution to stony-pebble soils, and a closely related species - Icelus spiniger Gilb. - to sandy and silty-sandy. The reasons that cause fish to be confined to a certain type of soil, as mentioned above, can be very diverse. This is either a direct adaptation to a given type of soil (soft - for burrowing forms, hard - for attached ones, etc.), or, since a certain nature of the soil is associated with a certain regime of the reservoir, in many cases there is a connection in the distribution of fish with the soil through the hydrological regime. And finally, the third form of connection between the distribution of fish and the soil is a connection through the distribution of food objects.
Many fish that have adapted to crawling on the ground have undergone very significant changes in the structure of their limbs. The pectoral fin serves to support the ground, for example, in the larvae of the polypterus (Fig. 18, 3), some labyrinths, such as the Anabas, the Trigla, the Periophftialmidae and many Lophiiformes, for example , monkfish - Lophius piscatorius L. and chickweed - Halientea. In connection with adaptation to movement on the ground, the forelimbs of fish undergo quite significant changes (Fig. 16). The most significant changes occurred in legfins - Lophiiformes; in their forelimb a number of features similar to similar formations in tetrapods are observed. In most fish, the dermal skeleton is highly developed, and the primary one is greatly reduced, while in tetrapods the opposite picture is observed. Lophius occupies an intermediate position in the structure of its limbs; both its primary and cutaneous skeletons are equally developed. The two radialia of Lophius are similar to the zeugopodium of tetrapods. The musculature of the limbs of tetrapods is divided into proximal and distal, which is located in two groups.
It gives the impression that the whole fish is glowing. Most other deep-sea fish have special luminescent organs, sometimes quite complexly arranged. The most complex organ of luminescence in fish consists of an underlying layer of pigment, then there is a reflector, above which there are luminous cells covered with a lens on top (Fig. 22). Lighting location
5
Table 1
The nature of sound vibrations perceived by different fish
| Frequency in hertz |
|
Types of fish | | |
| from | BEFORE |
Phoxinus phoxinus (L.) | 16 | 7000 |
Leuciscus idus (L.) ¦ | 25 | 5524 |
Carassius auratus (L.) . | 25 | 3480 |
Nemachilus barbatulus (L.) | 25 | 3480 |
Amiurus nebulosus Le Sueur | 25 | 1300 |
Anguilla anguilla (L.) | 36 | 650 . |
Lebistes reticulatus Peters | 44 | 2068 |
Corvina nigra S. V | 36 | 1024 |
Diplodus annularis (L.) | 36 | 1250 |
Gobius niger L. | 44 | 800 |
Periophthalmus koelreiteri (Pallas) | 44 | 651 |
and turning off, which scares fish away from the gates of the seine during purse-netting (Tarasov, 1956).
Sounds are also used to attract fish to the fishing site. From now on, catching catfish "on a sliver" basis is possible. Catfish are attracted to the fishing site by peculiar gurgling sounds.
Powerful ultrasonic vibrations can kill fish (Elpiver, 1956).
By the sounds made by fish, it is possible to detect their concentrations. Thus, Chinese fishermen detect spawning aggregations of large yellow perch Pseudosciaena crocea (Rich.) by the sounds made by the fish. Having approached the expected place of fish accumulation, the fishermen’s foreman lowers a bamboo tube into the water and listens to the fish through it. In Japan, special radio beacons are installed, “tuned” to the sounds made by some commercial fish. When a school of fish of a given species approaches the buoy, it begins to send appropriate signals, notifying fishermen about the appearance of fish.
It is possible that the sounds made by fish are used by them as an echometric device. Location by perceiving emitted sounds is apparently especially common among deep-sea fish. In the Atlantic near Porto Rico, it was discovered that biological sounds, apparently emitted by deep-sea fish, were then repeated in the form of weak reflections from the bottom (Griffin, 1950). Protasov and Romanenko showed that the beluga makes rather strong sounds, sending , it can detect objects located from it at a distance of up to 15 and further.
Electric currents, electromagnetic vibrations
Natural waters contain weak natural electrical currents associated with both terrestrial magnetism and solar activity. Natural teluric currents have been established for the Barents and Black Seas, but they apparently exist in all significant bodies of water. These currents undoubtedly have great biological significance, although their role in biological processes in reservoirs is still very poorly studied (Mironov, 1948).
Pisces react subtly to electric currents. At the same time, many species themselves can not only produce electrical discharges, but, apparently, also create an electromagnetic field around their body. Such a field, in particular, is established around the head region of the lamprey - Petromyzon matinus (L.).
Pisces can send and perceive electrical discharges with their senses. The discharges produced by fish can be of two types: strong^ serving for attack or defense (see below p. 110), or weak, having a signal
meaning. In the sea lamprey (cyclostomata), a voltage of 200-300 mV created near the front of the head apparently serves to detect (by changes in the created field) objects approaching the lamprey’s head. It is very likely that the “electrical organs” described by Stensio (P)27) in cephalaspids had a similar function (Sibakin 1956, 1957). Many electric eels produce weak, rhythmic discharges. The number of discharges varied in the six studied species from 65 to 1 000 discharges. The number of digits also varies depending on the condition of the fish. Thus, in a calm state Mormyrus kannume Bui. produces one pulse per second; when worried, it sends up to 30 impulses per second. Swimming gymnarch - Gymnarchus niloticus Cuv. - sends pulses with a frequency of 300 pulses per second.
Perception of electromagnetic oscillations in Mormyrus kannume Bui. carried out using a number of receptors located at the base of the dorsal fin and innervated by the head nerves extending from the hindbrain. In Mormyridae, impulses are sent by an electrical organ located on the caudal peduncle (Wright, 1958).
Different species of fish have different susceptibility to the effects of electric current (Bodrova and Krayukhin, 1959). Of the freshwater fish studied, the most sensitive was pike, the least sensitive were tench and burbot. Weak currents are perceived mainly by fish skin receptors. Currents of higher voltage act directly on the nerve centers (Bodrova and Krayukhin, 1960).
Based on the nature of the fish’s reaction to electric currents, three phases of action can be distinguished.
The first phase, when the fish, having entered the field of action of the current, shows anxiety and tries to leave it; in this case, the fish strives to take a position in which the axis of its body would be parallel to the direction of the current. The fact that fish react to an electromagnetic field is now confirmed by the development of conditioned reflexes in fish to it (Kholodov, 1958). When a fish enters the current field, its breathing rhythm increases. Fish have species-specific reactions to electric currents. So the American catfish - Amiurus nebulosus Le Sueur - reacts to current more strongly than gold fish- Carassius auratus (L.). Apparently, fish with highly developed receptors in the skin react more sharply to tok (Bodrova and Krayukhin, 1958). In the same species of fish, larger individuals respond to currents earlier than smaller ones.
The second phase of the action of the current on the fish is expressed in the fact that the fish turns its head towards the anode and swims towards it, reacting very sensitively to changes in the direction of the current, even very minor ones. Perhaps this property is associated with the orientation of fish when migrating into the sea towards teluric currents.
The third phase is galvanonarcosis and subsequent death of the fish. The mechanism of this action is associated with the formation of acetylcholine in the blood of fish, which acts as a drug. At the same time, the breathing and cardiac activity of the fish are disrupted.
In fisheries, electric currents are used to catch fish by directing their movement towards fishing gear or by causing a state of shock in the fish. Electric currents are also used in electric barriers to prevent fish from reaching the turbines of hydroelectric power stations, into irrigation canals, to direct the rift to the mouths of fish passages, etc. (Gyulbadamov, 1958; Nusenbeum, 1958).
X-rays and radioactivity
X-rays have a sharp negative effect on adult fish, as well as on eggs, embryos and larvae. As G.V. Samokhvalova’s experiments (1935, 1938) conducted on Lebistes reticulatus showed, a dose of 4000 g is lethal for fish. Smaller doses when affecting the gonad of Lebistes reticulatus cause a decrease in litter and degeneration of the gland. Irradiation of young immature males causes underdevelopment of secondary sexual characteristics.
When X-rays penetrate into water, they quickly lose their strength. As shown in fish, at a depth of 100 m the strength of X-rays is reduced by half (Folsom and Harley, 1957; Publ. 55I).
Radioactive radiation has a stronger effect on fish eggs and embryos than on adult organisms (Golovinskaya and Romashov, 1960).
The development of the nuclear industry, as well as the testing of atomic and hydrogen bombs, led to a significant increase in the radioactivity of air and water and the accumulation of radioactive elements in aquatic organisms. The main radioactive element important in the life of organisms is strontium 90 (Sr90). Strontium enters the fish body mainly through the intestines (mainly through the small intestines), as well as through the gills and skin (Danilchenko, 1958).
The bulk of strontium (50-65%) is concentrated in the bones, much less in the viscera (10-25%) and gills (8-25%) and very little in the muscles (2-8%). But strontium, which is deposited mainly in the bones, causes the appearance of radioactive ytrium -I90 in the muscles.
Fish accumulate radioactivity both directly from sea water and from other organisms that serve as food for them.
The accumulation of radioactivity in young fish occurs more quickly than in adults, which is associated with a higher metabolic rate in the former.
More active fish (tuna, Cybiidae, etc.) remove radioactive strontium from their bodies faster than sedentary fish (for example, Tilapia), which is associated with different metabolic rates (Boroughs, Chipman, Rice, Publ, 551, 1957). In fish of the same species in a similar environment, as shown in the example of the eared perch - Lepomis, the amount of radioactive strontium in the bones can vary by more than five pa? (Krumholz, Goldberg, Boroughs, 1957* Publ. 551). Moreover, the radioactivity of the fish can be many times higher than the radioactivity of the water in which it lives. Thus, in Tilapia it was found that when fish were kept in radioactive water, their radioactivity, compared to water, after two days was the same, and after two months it was six times greater (Moiseev, 1958).
The accumulation of Sr9° in fish bones causes the development of the so-called Urov disease/associated with a disorder of calcium metabolism. Human consumption of radioactive fish is contraindicated. Since the half-life of strontium is very long (about 20 years), and it is firmly retained in bone tissue, fish remain infected for a long time. However, the fact that strontium is concentrated mainly in bones makes it possible to use fish fillets, cleaned from bones, after a relatively short period of aging, in storage (refrigerators), since the ytrium concentrated in meat has a short half-life,
/water temperature /
In the life of fish, water temperature is of great importance.
Like other poikilthermic animals, i.e., with an unstable body temperature, animal fish are more dependent on the temperature of the surrounding water - than homothermic animals. At the same time, the main difference between them* lies in the quantitative side of the process of heat formation. In cold-blooded animals, this process is much slower than in warm-blooded animals, which have a constant temperature. Thus, a carp weighing 105 g emits 10.2 kcal of heat per day per kilogram, and a starling weighing 74 g emits 270 kcal.
In most fish, the body temperature differs by only 0.5-1° from the temperature of the surrounding water, and only in tuna this difference can reach more than 10° C.
Changes in the metabolic rate of fish are closely related to changes in the temperature of the surrounding water. In many cases! temperature changes act as a signal factor, as a natural stimulus that determines the beginning of a particular process - spawning, migration, etc.
The rate of development of fish is largely related to changes in temperature. Within a certain temperature amplitude, a direct dependence of the rate of development on temperature changes is often observed.
Fish can live at a wide variety of temperatures. The highest temperatures above +52° C are tolerated by a fish from the family Cyprinodontidae - Cyprinodoti macularius Baird.- et Gir., which lives in small hot springs in California. On the other hand, crucian carp - Carassius carassius (L.) - and dalia, or black fish * Dallia pectoralis Bean. - even withstands freezing, however, provided that the body juices remain unfrozen. Arctic cod - Boreogadus saida (Lep.) - leads an active lifestyle at a temperature of -2°.
Along with the adaptability of fish to certain temperatures (high or low), the amplitude of temperature fluctuations at which the same species can live is also very important for the possibility of their settlement and life in different conditions. This temperature range is very different for different fish species. Some species can withstand fluctuations of several tens of degrees (for example, crucian carp, tench, etc.), while others are adapted to live with an amplitude of no more than 5-7°. Typically, fish from tropical and subtropical zones are more stenothermic than fish from temperate and high latitudes. Marine forms are also more stenothermic than freshwater forms.
While the overall range of temperatures at which a fish species can live can often be very large, for each stage of development it usually turns out to be significantly less.
Fish react differently to temperature fluctuations and depending on their biological state. For example, salmon eggs can develop at temperatures from 0 to 12°C, and adult salmon easily tolerate fluctuations from negative temperatures to 18-20°C, and possibly higher.
Carp successfully withstands winter at temperatures ranging from negative to 20°C and above, but it can feed only at temperatures not lower than 8-10°C, and reproduces, as a rule, at temperatures not lower than 15°C.
Fish are usually divided into stenothermic, i.e., those adapted to a narrow amplitude of temperature fluctuations, and eurythermic, those. that can live across significant temperature gradients.
Optimal temperatures to which they are adapted are also associated with species specificity in fish. Fish from high latitudes have developed a type of metabolism that allows them to successfully feed at very low temperatures. But at the same time, in cold-water fish (burbot, taimen, whitefish) at high temperatures, activity sharply decreases and feeding intensity decreases. On the contrary, in fish from low latitudes, intensive metabolism occurs only at high temperatures;
Within the optimal temperature range for a given type of fish, an increase in temperature usually leads to an increase in the intensity of food digestion. Thus, in roach, as can be seen from the graph above (Fig. 27), the rate of food digestion at
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th
II"*J
O
zo zi
Figure 27. Daily consumption (dashed line) and rate of food digestion (solid line) of the roach Rutilus rutilus casplcus Jak. at different temperatures (according to Bokova, 1940)
15-20° C is three times more than at a temperature of 1-5° C. Due to the increase in the rate of digestion, the intensity of feed consumption also increases.
Similar adaptations are observed in fish developing at different salinities, which is also associated with changes in density. It should be noted that the number of vertebrae changes with changes in temperature (or salinity) during the segmentation period.
February
200
tations of the body. If this kind of influence occurs at later stages of development, then there is no change in the number of metameres (Hubbs, 1922; Taning, 1944). A similar phenomenon was observed for a number of fish species (salmon, carp, etc.). Similar changes occur in some fish species
and in the number of rays in unpaired fins, which is also associated with adaptation to movement in water of varying densities.
Particular attention should be paid to the meaning of ice in the Life of Fish. The forms of influence of ice on fish are very diverse] This is a direct temperature effect, since when Water freezes, the temperature rises, and when ice melts, it decreases. But other forms of ice influence are much more important for fish. The importance of ice cover is especially great as an insulator of water 6 tons of the atmosphere. During freeze-up, the influence of winds on water almost completely stops, the supply of oxygen from the air, etc., slows down greatly (see below). By isolating water from air, ice also makes it difficult for light to penetrate into it. Finally, ice sometimes has on fish and mechanical impact: There are known cases when, in the coastal zone, ice washed ashore crushed fish and eggs that were holding near the shore. Ice also plays some role in changing the chemical composition of water and the value of salinity: The salt composition of ice is different from the salt composition of the sea water, and with massive ice formation, not only the salinity of the water changes, increasing, but also the salt ratio. Melting ice, on the contrary, causes a decrease in salinity and a change in the salt composition of the opposite nature. " then.-/that ‘
In the cold, dark depths of the oceans, the water pressure is so great that no land animal could withstand it. Despite this, there are creatures here that have been able to adapt to such conditions.
In the sea you can find a variety of biotopes. In the sea depths tropical zone The water temperature reaches 1.5-5 ° C; in the polar regions it can drop below zero.
A wide variety of life forms are presented below the surface at a depth where sunlight is still able to receive, provides the possibility of photosynthesis, and, therefore, gives life to plants, which in the sea are the initial element of the trophic chain.
Tropical seas are home to incomparably more animals than arctic waters. The deeper you go, the species diversity becomes poorer, there is less light, the water is colder, and the pressure is higher. At a depth of two hundred to a thousand meters, about 1,000 species of fish live, and at a depth of one thousand to four thousand meters, there are only one hundred and fifty species.
A belt of water with a depth of three hundred to a thousand meters, where twilight reigns, is called the mesopelagial. At a depth of more than a thousand meters, darkness has already set in, the water waves here are very weak, and the pressure reaches 1 ton 265 kilograms per square centimeter. At this depth live deep-sea shrimp of the genus MoIobiotis, cuttlefish, sharks and other fish, as well as numerous invertebrates.
OR DID YOU KNOW THAT...
The diving record belongs to the cartilaginous fish Basogigas, which was spotted at a depth of 7965 meters.
Most invertebrates living at great depths are black, and most deep-sea fish are brown or black. Thanks to this protective coloring, they absorb the bluish-green light of deep waters.
Many deep-sea fish have an air-filled swim bladder. And it is still not clear to researchers how these animals can withstand enormous water pressure.
The males of some species of deep-sea anglerfish attach with their mouths to the bellies of larger females and grow attached to them. As a result, the man remains attached to the female for the rest of his life, feeds at her expense, and they even have a common circulatory system. And thanks to this, the female does not have to look for a male during the spawning period.
One eye of a deep-sea squid that lives near the British Isles is much larger than the other. With the help of his large eye he orients himself at depth, and he uses his second eye when he rises to the surface.
In the depths of the sea, eternal twilight reigns, but in the water, numerous inhabitants of these biotopes glow in different colors. The glow helps them attract mates, prey, and also scare away enemies. The glow of living organisms is called bioluminescence.
BIOLUMINESCIENCE
Many species of animals that inhabit the dark depths of the sea can emit their own light. This phenomenon is called visible luminescence of living organisms, or bioluminescence. It is caused by the enzyme luciferase, which is a catalyst for the oxidation of substances produced as a result of the reaction of light - luciferin. Animals can create this so-called “cold light” in two ways. Substances necessary for bioluminescence found in their body or in the body of luminous bacteria. The European anglerfish has light-emitting bacteria contained in vesicles at the end of the dorsal fin in front of the mouth. Bacteria need oxygen to glow. When the fish does not intend to emit light, it closes the blood vessels that lead to the place in the body where the bacteria are located. The spotted scalpelus fish (Prigobiernat parapirebrais) carries billions of bacteria in special bags under its eyes; with the help of special leather folds, the fish completely or partially closes these bags, regulating the intensity of the emitted light. To enhance the glow, many crustaceans, fish and squids have special lenses or a layer of cells that reflect light. Inhabitants of the deep use bioluminescence in different ways. Deep sea fish glow in different colors. For example, the photophores of ribsocks emit a greenish color, while the photophores of astronest emit a violet-blue color.
SEARCHING FOR A PARTNER
The inhabitants of the deep sea resort to various methods of attracting a partner in the dark. Light, smell and sound play an important role in this. In order not to lose the female, males even use special techniques. The relationship between males and females of the Woodilnikovidae is interesting. The life of the European anglerfish has been better studied. Males of this species usually have no problem finding a large female. With the help of their large eyes, they notice its typical light signals. Having found a female, the male firmly attaches to her and grows to her body. From this time on, he leads an attached lifestyle, even feeding through the female’s circulatory system. When a female anglerfish lays eggs, the male is always ready to fertilize her. Males of other deep-sea fish, for example, gonostomidae, are also smaller than females, and some of them have a well-developed sense of smell. Researchers believe that in this case, the female leaves behind an odorous trail, which the male finds. Sometimes male European anglerfish are also found by the smell of females. In water, sounds travel a long distance. That is why the males of three-headed and toad-shaped animals move their fins in a special way and make a sound that should attract the attention of the female. Toadfish produce beeps that are rendered as "boop".
There is no light at this depth and no plants grow here. Animals that live in the depths of the sea can only hunt similar deep-sea inhabitants or feed on carrion and decaying organic matter. Many of them, such as sea cucumbers, sea stars and bivalves, feed on microorganisms that they filter from the water. Cuttlefish usually prey on crustaceans.
Many species of deep-sea fish eat each other or hunt small prey for themselves. Fish that feed on molluscs and crustaceans must have strong teeth to crush the shells that protect the soft bodies of their prey. Many fish have a bait located directly in front of their mouth that glows and attracts prey. By the way, if you are interested in an online store for animals. please contact us.
Living conditions in various areas of fresh water, especially in the sea, leave a sharp mark on the fish living in these areas.
Fishes can be divided into marine fish, anadromous fish, semi-anadromous fish, or estuarine fish, brackish water fish, and freshwater fish. Significant differences in salinity already have implications for the distribution of individual species. The same is true for differences in other properties of water: temperature, lighting, depth, etc. Trout requires different water than barbel or carp; Tench and crucian carp also live in reservoirs where perch cannot live because the water is too warm and muddy; asp requires clean, flowing water with fast riffles, and pike can also stay in standing water overgrown with grass. Our lakes, depending on the conditions of existence in them, can be distinguished as pike perch, bream, crucian carp, etc. Inside more or less large lakes and rivers, we can note different zones: coastal, open water and bottom, characterized by different fish. Fish from one zone can enter another zone, but in each zone one or another species composition predominates. The coastal zone is the richest. The abundance of vegetation, therefore food, makes this area favorable for many fish; This is where they feed, this is where they spawn. The distribution of fish among zones plays a big role in fishing. For example, burbot (Lota lota) is a demersal fish, and is caught from the bottom with nets, but not with floating nets, which are used to catch asp, etc. Most whitefish (Coregonus) feed on small planktonic organisms, mainly crustaceans. Therefore, their habitat depends on the movement of plankton. In winter, they follow the latter into the depths, but in the spring they rise to the surface. In Switzerland, biologists indicated places where planktonic crustaceans live in winter, and here the whitefish fishery arose; On Baikal, omul (Coregonus migratorius) is caught in winter nets at a depth of 400-600 m.
The demarcation of zones in the sea is more pronounced. The sea, according to the living conditions it provides for organisms, can be divided into three zones: 1) littoral, or coastal; 2) pelagic, or open sea zone; 3) abyssal, or deep. The so-called sublittoral zone, which constitutes the transition from coastal to deep, already displays all the signs of the latter. Their boundary is a depth of 360 m. The coastal zone begins from the shore and extends to a vertical plane delimiting the area deeper than 350 m. The open sea zone will be outward from this plane and upward from another plane lying horizontally at a depth of 350 m. The deep zone will be below from this last one (Fig. 186).
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