Causes of adaptation of fish in the aquatic environment. How are fish adapted to life in the water? Diversity of fish living in the water depths

The conditions of life in various areas of fresh waters, and especially in the sea, leave a strong imprint on the fish living in these areas.
Fish can be divided into marine, anadromous, semi-anadromous or estuarine fish, brackish water fish, and freshwater fish. Already significant differences in salinity are important for the distribution certain types. The same is true of differences in other properties of water: temperature, lighting, depth, etc. Trout requires different water than barbel or carp; tench and crucian carp also keep in such reservoirs where perch cannot live due to too warm and muddy water; asp requires clean flowing water with fast rifts, and pike can also stay in stagnant water overgrown with grass. Our lakes, depending on the conditions of existence in them, can be distinguished as zander, bream, crucian, etc. Within 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 one or another species composition predominates in each zone. The coastal zone is richest of all. The abundance of vegetation, hence food, makes this area favorable for many fish; here they feed, here they throw an acre. The distribution of fish into zones plays a big role in fisheries. For example, burbot (Lota lota) is a demersal fish, and is caught from the bottom with venters, but not with the flowing nets 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 to the depths, but in the spring they rise to the surface. In Switzerland, biologists pointed out the places where planktonic crustaceans live in winter, and here the whitefish fishery arose after that; on Lake Baikal, omul (Coregonus migratorius) is caught with nets in winter at a depth of 400-600 m.
The demarcation of the zone in the sea is more pronounced. The sea, according to the living conditions that it provides for organisms, can be divided into three zones: 1) littoral, or coastal; 2) pelagic, or zone high seas; 3) abyssal, or deep. The so-called sublittoral zone, which constitutes the transition from the coastal to the deep, already reveals all the signs of the latter. Their boundary is a depth of 360 m. The coastal zone starts from the coast and extends to a vertical plane that limits 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 deep zone will be below this last (Fig. 186).

Deep sea fish are among the most amazing creatures on the planet. Their uniqueness is explained primarily by the harsh conditions of existence. That is why the depths of the world's oceans, and especially deep-sea depressions and trenches, are not at all densely populated.

and their adaptation to the conditions of existence

As already mentioned, the depths of the oceans are not as densely populated as, say, the upper layers of the water. And there are reasons for this. The fact is that the conditions of existence change with depth, which means that organisms must have some adaptations.

1. Life in the dark. With depth, the amount of light decreases sharply. It is believed that the maximum distance that a sunbeam travels in water is 1000 meters. Below this level, no traces of light were found. Therefore, deep-sea fish are adapted to life in total darkness. Some fish species do not have functioning eyes at all. The eyes of other representatives, on the contrary, are very strongly developed, which makes it possible to catch even the weakest light waves. Another interesting device is the luminescent organs, which can glow using energy chemical reactions. Such light not only facilitates movement, but also lures potential prey.
2. High pressure. Another feature of the deep-sea existence. That is why the internal pressure of such fish is much higher than that of their shallow relatives.
3. Low temperature. With depth, the temperature of the water decreases significantly, so the fish are adapted to life in such an environment.
4. Lack of food. Since the diversity of species and the number of organisms decreases with depth, there is, accordingly, very little food left. Therefore, deep-sea fish have supersensitive organs of hearing and touch. This gives them the ability to detect potential prey at a great distance, which in some cases is measured in kilometers. By the way, such a device makes it possible to quickly hide from a larger predator.

You can see that the fish living in the depths of the ocean are truly unique organisms. In fact, a huge area of ​​the world's oceans is still unexplored. That is why the exact number of deep-sea fish species is unknown.

Diversity of fish living in the water depths

Although modern scientists know only a small part of the population of the depths, there is information about some very exotic inhabitants of the ocean.

Bathysaurus- the deepest predatory fish that live at a depth of 600 to 3500 m. They live in tropical and subtropical water spaces. This fish has almost transparent skin, large, well-developed sensory organs, and its oral cavity littered with sharp teeth (even the tissues of the palate and tongue). Representatives of this species are hermaphrodites.

viper fish- Another unique representative of the underwater depths. It lives at a depth of 2800 meters. It is these species that inhabit the depth. The main feature of the animal is its huge fangs, which are somewhat reminiscent of the poisonous teeth of snakes. This species is adapted to exist without constant food - the stomachs of fish are so stretched that they can swallow whole creature much larger than themselves. And on the tail of the fish there is a specific luminous organ, with the help of which they lure prey.

Angler - a rather unpleasant-looking creature with huge jaws, a small body and poorly developed muscles. It lives on Since this fish cannot actively hunt, it has developed special adaptations. has a special luminous organ that releases certain chemicals. Potential prey reacts to light, swims up, after which the predator swallows it completely.

In fact, there are much more depths, but not much is known about their way of life. The fact is that most of them can exist only under certain conditions, in particular, when high pressure. Therefore, it is not possible to extract and study them - when they rise to the upper layers of the water, they simply die.

The amazing variety of shapes and sizes of fish is explained by long history their development and high adaptability to the conditions of existence.

The first fish appeared several hundred million years ago. Now existing fish bear little resemblance to their ancestors, but there is a certain similarity in the shape of the body and fins, although the body of many primitive fish was covered with a strong bony shell, and highly developed pectoral fins resembled wings.

The oldest fish died out, leaving their traces only in the form of fossils. From these fossils, we make guesses, assumptions about the ancestors of our fish.

It is even more difficult to talk about the ancestors of fish that left no traces. There were also fish that had no bones, no scales, no shells. Similar fish still exist. These are lampreys. They are called fish, although, in the words of the famous scientist L. S. Berg, they differ from fish, like lizards from birds. Lampreys do not have bones, they have one nasal opening, the intestines look like a simple straight tube, the mouth is in the form of a round sucker. In the past millennia, there were many lampreys and related fish, but they are gradually dying out, giving way to more adapted ones.

Sharks are also fish of the most ancient origin. Their ancestors lived more than 360 million years ago. The internal skeleton of sharks is cartilaginous, but there are solid formations in the form of spikes (teeth) on the body. In sturgeons, the body structure is more perfect - there are five rows of bone bugs on the body, there are bones in the head section.

According to the numerous fossils of ancient fish, one can trace how the structure of their body developed and changed. However, it cannot be assumed that one group of fish directly converted to another. It would be a gross mistake to assert that sturgeons originated from sharks, and teleosts from sturgeons. We must not forget that, in addition to the named fish, there were a huge number of others, which, unable to adapt to the conditions of the nature surrounding them, died out.

Modern fish also adapt to natural conditions, and in the process, slowly, sometimes imperceptibly, their lifestyle and body structure change.

An amazing example of high adaptability to environmental conditions is represented by lungfish. Ordinary fish breathe with gills, which consist of gill arches with gill rakers and gill filaments attached to them. Lungfish, on the other hand, can breathe with both gills and “lungs” - peculiarly arranged swimming ones and hibernates. In such a dry nest, it was possible to transport protopterus from Africa to Europe.

Lepidosiren inhabits swampy water bodies South America. When reservoirs are left without water during a drought lasting from August to September, lepidosiren, like protopterus, buries itself in silt, falls into a stupor, and its life is supported by bubbles. The bladder-lung of lungfish is replete with folds and partitions with many blood vessels. It resembles an amphibian lung.

How to explain this structure of the respiratory apparatus in lungfish? These fish live in shallow waters, which are quite long time dry out and become so poor in oxygen that breathing with gills becomes impossible. Then the inhabitants of these reservoirs - lungfish - switch to breathing with the lungs, swallowing the outside air. When the reservoir completely dries up, they burrow into the silt and experience drought there.

There are very few lungfish left: one genus in Africa (protopterus), another in America (lepidosiren) and a third in Australia (neoceratod, or scaly).

Protopterus inhabits fresh water bodies of Central Africa and has a length of up to 2 meters. During the dry period, it burrows into the silt, forming a chamber (“cocoon”) of clay around itself, content with an insignificant amount of air penetrating here. Lepidosiren is a large fish, reaching 1 meter in length.

The Australian flake is somewhat larger than the lepidosiren, lives in quiet rivers, heavily overgrown with aquatic vegetation. When the water level is low (dry weather) time) the grass begins to rot in the river, the oxygen in the water almost disappears, then the flake plant switches to breathing atmospheric air.

All listed lungfish are consumed by the local population for food.

Each biological feature has some significance in the life of a fish. What kind of appendages and adaptations do fish have for protection, intimidation, attack! A wonderful device has a small bitter fish. By the time of reproduction, a long tube grows in the female bitterling, through which she lays eggs in the cavity of a bivalve shell, where the eggs will develop. This is similar to the habits of a cuckoo, throwing its eggs into other people's nests. It is not so easy to get mustard caviar from hard and sharp shells. And the bitter man, having dumped his care on others, hurries to put away his cunning device and again walks in the free space.

In flying fish, capable of rising above the water and flying over fairly long distances, sometimes up to 100 meters, the pectoral fins have become like wings. Frightened fish jump out of the water, spread their fins-wings and rush over the sea. But an air walk can end very sadly: birds of prey often attack the little birds.

Flies in temperate and tropical parts Atlantic Ocean and in the Mediterranean. Their size is up to 50 centimeters in.

Longfins living in tropical seas are even more adapted to flying; one species is also found in the Mediterranean Sea. Longfins are similar to herring: the head is sharp, the body is oblong, the size is 25-30 centimeters. The pectoral fins are very long. Longfins have huge swim bladders (the length of the bladder is more than half the length of the body). This device helps the fish stay in the air. Longfins can fly over distances exceeding 250 meters. When flying, the fins of longfins, apparently, do not wave, but act as a parachute. The flight of a fish is similar to the flight of a paper dove, which is often launched by children.

Jumping fish are also wonderful. If in flying fish the pectoral fins are adapted for flying, then in jumpers they are adapted for jumping. Small jumping fish (their length is not more than 15 centimeters) that live in coastal waters mainly Indian Ocean, can leave water for quite a long time and get their own food (mainly insects), jumping on land and even climbing trees.

The pectoral fins of jumpers are like strong paws. In addition, the jumpers have another feature: the eyes placed on the head outgrowths are mobile and can see in the water and in the air. During a land journey, the fish tightly covers the gill covers and thus protects the gills from drying out.

No less interesting is the creeper, or climbing perch. This is a small (up to 20 centimeters) fish that lives in fresh waters India. main feature its consists in the fact that it can crawl away on land to a long distance from water.

Creepers have a special supra-gill apparatus, which the fish uses when breathing air in cases where there is not enough oxygen in the water or when it moves overland from one reservoir to another.

Aquarium fish macropods, fighting fish and others also have a similar supragillary apparatus.

Some fish have luminous organs that allow them to quickly find food in the dark depths of the seas. Luminous organs, a kind of headlights, in some fish are located near the eyes, in others - at the tips of the long processes of the head, and in others, the eyes themselves emit light. An amazing property - the eyes both illuminate and see! There are fish that radiate light with their whole body.

In tropical seas, and occasionally in the waters of the Far Eastern Primorye, one can find interesting sticky fish. Why such a name? Because this fish is able to stick, stick to other objects. There is a large suction cup on the head, with the help of which the stick sticks to the fish.

Not only does the sticky use free transport, the fish also receive a “free” lunch, eating the remnants of the table of their drivers. The driver, of course, is not very pleasant to travel with such a “rider” (the length of the stick reaches 60 centimeters), but it is not so easy to get rid of it either: the fish sticks tightly.

Shore dwellers use this ability to trap turtles. A cord is tied to the tail and the fish is put on the turtle. The sticky quickly sticks to the turtle, and the fisherman lifts the sticky together with the prey into the boat.

In the fresh waters of the basins of the tropical Indian and Pacific Oceans, small archer fish live. The Germans call it even more successful - "Schützenfish", which means a shooter-fish. The archer, swimming near the shore, notices an insect sitting on the coastal or water grass, draws water into his mouth and lets a stream into his "fishing" animal. How not to call a archer a shooter?

Some fish have electrical organs. Known American electric catfish. The electric stingray lives in the tropical parts of the oceans. Its electric shocks can knock a grown man off his feet; small aquatic animals often die from the blows of this stingray. The electric stingray is a rather large animal: up to 1.5 meters in length and up to 1 meter wide.

Strong electric shocks are also capable of inflicting an electric eel, reaching 2 meters in length. A German book depicts frenzied horses attacking electric eels in the water, although there is no small part of the artist's imagination here.

All of the above and many other features of fish have been developed over thousands of years as necessary means of adapting to life in aquatic environment.

It is not always so easy to explain why one or another device is needed. Why, for example, does a carp need a strong serrated fin ray, if it helps to entangle the fish in the net! Why do we need such long tails for a wide-mouthed and a whistle? Undoubtedly, this has its own biological meaning, but not all the mysteries of nature have been solved by us. We have given a very small number of curious examples, but they all convince of the expediency of various adaptations of animals.

In flounder, both eyes are on one side of a flat body - on the one that is opposite to the bottom of the reservoir. But they will be born, come out of eggs, flounders with a different arrangement of eyes - one on each side. In larvae and fry of flounder, the body is still cylindrical, and not flat, like in adult fish. The fish lies on the bottom, grows there, and its eye from the bottom side gradually passes to the upper side, on which both eyes eventually end up. Surprising but understandable.

The development and transformation of the eel is also surprising, but less understood. The eel, before acquiring its characteristic serpentine form, undergoes several transformations. At first it looks like a worm, then it takes the form of a tree leaf and, finally, the usual shape of a cylinder.

In an adult eel, the gill slits are very small and tightly covered. The feasibility of this device is that it is tightly covered. the gills dry much more slowly, and with moistened gills, the eel can remain alive for a long time without water. There is even a rather plausible belief among the people that the eel crawls through the fields.

Many fish are changing before our eyes. The offspring of large crucians (weighing up to 3-4 kilograms), transplanted from the lake into a small low-feeding pond, does not grow well, and adult fish look like “dwarfs”. This means that the adaptability of fish is closely related to high variability.

I, Pravdin "The story of the life of fish"

Fish are the oldest vertebrate chordates that inhabit exclusively aquatic habitats, both salt and fresh water. Compared to air, water is a denser habitat.

In the external and internal structure, fish have adaptations for life in water:

1. Body shape is streamlined. The wedge-shaped head smoothly passes into the body, and the body into the tail.

2. The body is covered with scales. Each scale with its anterior end is immersed in the skin, and with its posterior end it rests on the scale of the next row, like a tile. Thus, the scales are a protective cover that does not interfere with the movement of the fish. Outside, the scales are covered with mucus, which reduces friction during movement and protects against fungal and bacterial diseases.

3. Fish have fins. Paired fins (pectoral and ventral) and unpaired fins (dorsal, anal, caudal) provide stability and movement in the water.

4. A special outgrowth of the esophagus helps fish to stay in the water column - swimming bladder. It is filled with air. By changing the volume of the swim bladder, fish change their specific gravity (buoyancy), i.e. become lighter or heavier than water. As a result, they can stay at different depths for a long time.

5. The respiratory organs of fish are gills, which absorb oxygen from the water.

6. The sense organs are adapted to life in water. The eyes have a flat cornea and a spherical lens - this allows the fish to see only close objects. The olfactory organs open outward through the nostrils. The sense of smell in fish is well developed, especially in predators. The organ of hearing consists only of the inner ear. Fish have a specific sense organ - the lateral line.

It has the appearance of tubules stretching along the entire body of the fish. Sensory cells are located at the bottom of the tubules. The lateral line of the fish perceive all movements of the water. Due to this, they react to the movement of objects around them, to various obstacles, to the speed and direction of currents.

Thus, due to the peculiarities of the external and internal structure fish are perfectly adapted to life in the water.

What factors contribute to the onset of diabetes? Explain preventive measures for this disease.

Diseases do not develop on their own. For their appearance, a combination of predisposing factors, the so-called risk factors, is required. Knowledge about the factors in the development of diabetes helps to recognize the disease in a timely manner, and in some cases even prevent it.

Risk factors for diabetes are divided into two groups: absolute and relative.

The group of absolute risk of diabetes mellitus includes factors associated with heredity. This is a genetic predisposition to diabetes, but it does not give a 100% prognosis and a guaranteed undesirable outcome. For the development of the disease, a certain influence of circumstances is necessary, environment, manifested in relative risk factors.

Relative factors in the development of diabetes include obesity, metabolic disorders, and a number of concomitant diseases and conditions: atherosclerosis, coronary heart disease, hypertension, chronic pancreatitis, stress, neuropathy, strokes, heart attacks, varicose veins veins, vascular damage, edema, tumors, endocrine diseases, long-term use of glucocorticosteroids, elderly age, pregnancy with a fetus weighing more than 4 kg and many, many other diseases.

Diabetes - This is a condition characterized by an increase in blood sugar levels. Modern classification diabetes mellitus, accepted World Organization health care (WHO), distinguishes several of its types: 1st, in which the production of insulin by pancreatic b-cells is reduced; and the 2nd type is the most common, in which the sensitivity of body tissues to insulin decreases, even with its normal production.

Symptoms: thirst, frequent urination, weakness, complaints of itchy skin, weight change.