Fish and aquatic environment. Adaptations to living conditions, adaptation of shape and movement
The amazing variety of shapes and sizes of fish is explained by the long history of their development and high adaptability to living conditions.
The first fish appeared several hundred million years ago. Today's 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 the highly developed pectoral fins resembled wings.
The oldest fish became extinct, leaving their traces only in the form of fossils. From these fossils we make guesses and 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, scales, or shells. Similar fish still exist today. These are lampreys. They are called fish, although they, in the words of the famous scientist L. S. Berg, differ from fish as lizards from birds. Lampreys have no bones, they have one nasal opening, the intestines look like a simple straight tube, and the mouth is like a round suction cup. In 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 ancient origin. Their ancestors lived more than 360 million years ago. Internal skeleton sharks are cartilaginous, but on the body there are hard formations in the form of spines (teeth). Sturgeons have a more perfect body structure - there are five rows of bony bugs on the body, and there are bones in the head section.
From numerous fossils of ancient fish, one can trace how their body structure developed and changed. However, it cannot be assumed that one group of fish directly converted into another. It would be a gross mistake to claim that sturgeons evolved from sharks, and bony fishes came from sturgeons. We must not forget that, in addition to the named fish, there were a huge number of others that, unable to adapt to the conditions of the nature that surrounded them, became extinct.
Modern fish also adapt to natural conditions, and in the process, their lifestyle and body structure slowly, sometimes imperceptibly, change.
An amazing example of high adaptability to environmental conditions is provided by lungfish. Common fish breathe through gills consisting of gill arches with gill rakers and gill filaments attached to them. Lungfish, on the other hand, can breathe with both gills and “lungs” - uniquely designed swimming bodies and hibernate. In such a dry nest it was possible to transport Protopterus from Africa to Europe.
Lepidosiren inhabits the wetlands of South America. When reservoirs are left without water during the drought, which lasts from August to September, lepidosirenus, like Protopterus, buries itself in the silt, falls into torpor, and its life is supported by bubbles. The bladder-lung of lungfish is replete with folds and septa with many blood vessels. It resembles the lung of amphibians.
How can we explain this structure of the respiratory apparatus in lungfishes? These fish live in shallow bodies of water, which dry out for quite a long time and become so depleted of oxygen that breathing through their gills becomes impossible. Then the inhabitants of these reservoirs - lungfish - switch to breathing with their lungs, swallowing outside air. When the reservoir dries out completely, they bury themselves in the silt and survive the drought there.
There are very few lungfishes left: one genus in Africa (Protopterus), another in America (Lepidosiren) and a third in Australia (Neoceratod, or Lepidopterus).
Protopterus inhabits fresh water bodies Central Africa and have 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 the insignificant amount of air that penetrates here. Lepidosiren is a large fish, reaching 1 meter in length.
The Australian lepidoptera is somewhat larger than lepidosiren and lives in quiet rivers, heavily overgrown with aquatic vegetation. When the water level is low (dry climates) 
Time) the grass in the river begins to rot, the oxygen in the water almost disappears, then the lepidoptera switches to breathing atmospheric air.
All of the listed lungfish are consumed by the local population as food.
Each biological feature has some significance in the life of a fish. What kind of appendages and devices do fish have for protection, intimidation, and attack! The small bitterling fish has a remarkable adaptation. By the time of reproduction, the female bitterling grows a long tube through which she lays eggs into the cavity of a bivalve shell, where the eggs will develop. This is similar to the habits of a cuckoo that throws its eggs into other people's nests. It is not so easy to get bitterling caviar from the hard and sharp shells. And the bitterling, having shifted the care onto others, hurries to put away his cunning device and again walks in the open air.
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 fin-wings and rush over the sea. But the air ride can end very sadly: the flying birds are often attacked by birds of prey.
The flies are found in temperate and tropical parts of the Atlantic Ocean and the Mediterranean Sea. Their size is up to 50 centimeters 
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Longfins living in tropical seas are even more adapted to flight; one species is also found in the Mediterranean Sea. Longfins are similar to herrings: 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 flap, but act as a parachute. The flight of the fish is similar to the flight of a paper dove, which is often flown by children.
The jumping fish are also wonderful. If the pectoral fins of flying fish are adapted for flight, then in jumpers they are adapted for jumping. Small jumping fish (their length is no more than 15 centimeters), living in coastal waters ah, mainly in the Indian Ocean, they can leave the water for quite a long time and get food (mainly insects) by jumping on land and even climbing trees.
The pectoral fins of jumpers are like strong paws. In addition, jumpers have another feature: the eyes, located on the head projections, are mobile and can see in water and in the air. During a land journey, the fish's gill covers are tightly covered and this protects the gills from drying out.
No less interesting is the creeper, or persimmon. This is a small (up to 20 centimeters) fish that lives in the fresh waters of India. Its main feature is that it can crawl on land to a long distance from water.
Crawlers have a special epibranchial apparatus, which the fish uses when breathing air in cases where there is not enough oxygen in the water or when it moves over land from one body of water to another.
Aquarium fish, macropods, fighting fish and others also have a similar epibranchial 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 emit light with their entire body.
In the tropical seas, and occasionally in the waters of the Far Eastern Primorye, you can find the interesting fish stuck. Why this name? Because this fish is capable of sucking and sticking to other objects. There is a large suction cup on the head, with the help of which it sticks to the fish.
Not only does the stick enjoy free transport, the fish also receives a “free” lunch, eating the leftovers from the table of their drivers. The driver, of course, is not very pleased to travel with such a “rider” (the length of the stick reaches 60 centimeters), but it is not so easy to free himself from it: the fish is attached tightly.
Coastal residents use this sticking ability to catch turtles. A cord is attached to the fish's tail and the fish is released onto the turtle. The stick quickly attaches itself to the turtle, and the fisherman lifts the stick along with the prey into the boat.
Small splashing fish live in the fresh waters of the tropical Indian and Pacific oceans. The Germans call it even better - “Schützenfisch”, which means fish shooter. The splasher, swimming near the shore, notices an insect sitting on the coastal or aquatic grass, takes water into its mouth and releases a stream at its “game” animal. How can one not call a splasher a shooter?
Some fish have electrical organs. The American electric catfish is famous. The electric stingray lives in tropical parts of the oceans. Electrical shocks can knock down an adult; small aquatic animals often die from the blows of this stingray. The electric stingray is a fairly large animal: up to 1.5 meters long and up to 1 meters wide.
The electric eel, which reaches 2 meters in length, can also deliver strong electric shocks. One German book depicts enraged horses being attacked by electric eels in the water, although there is a fair amount 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 adaptation to life in the aquatic environment.
It is not always so easy to explain why this or that device is needed. For example, why does carp need a strong serrated fin ray if it helps entangle the fish in a net! Why do the broadmouth and the whistler need such long tails? There is no doubt that 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 interesting examples, but they all convince us of the feasibility of various animal adaptations.
In flounder, both eyes are located on one side of the flat body - on the one opposite the bottom of the reservoir. But flounders are born and emerge from the eggs with a different arrangement of eyes - one on each side. In flounder larvae and fry, 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 moves to the upper side, on which both eyes eventually end up. Surprising, but understandable.
The development and transformation of the eel is also amazing, but less understood. The eel, before acquiring its characteristic snake-like shape, undergoes several transformations. At first it looks like a worm, then it takes on the shape of a tree leaf and, finally, the usual shape of a cylinder.
In an adult eel, the gill slits are very small and tightly closed. The usefulness of this device is that it is tightly covered. the gills dry out much more slowly, and with moistened gills the eel can remain alive for a long time even without water. There is even a fairly plausible belief among people that the eel crawls through the fields.
Many fish are changing before our eyes. The offspring of large crucian carp (weighing up to 3-4 kilograms), transplanted from a lake into a small pond with little food, grows poorly, and adult fish have the appearance of “dwarfs”. This means that the adaptability of fish is closely related to high variability.
I, Pravdin "The Story of the Life of Fishes"
Open biology lesson in 7th grade
Topic: “Pisces superclass. Adaptations of fish to aquatic habitats"
Goal: To reveal the features of the internal and external structure of fish in connection with their habitat, to show the diversity of fish, to determine the importance of fish in nature and human economic activity, to indicate the necessary measures to protect fish resources.
Methodological goal: the use of ICT as one of the ways to form creative thinking and develop the interest of students, expand the experience of research activities based on previously acquired knowledge, develop information and communication competencies.
Lesson type: combined.
Type of lesson: lesson in the formation and systematization of knowledge.
Lesson objectives:
Educational: to generate knowledge about the general characteristics of fish, the features of the external structure of fish in connection with the aquatic habitat.
Educational: develop the ability to observe, establish cause-and-effect relationships, continue to develop the ability to work with a textbook: find answers to questions in the text, use the text and pictures to perform independent work.
Educational: fostering hard work, independence and respect when working in pairs and groups.
Objectives: 1) To familiarize students with the structural features of fish.
2) Continue developing the skills to observe the living
Organisms, work with the textbook text, perceive
Educational information through multimedia presentation and video.
Equipment: computer, multimedia projector,
Lesson plan:
Organizational moment
Arousing interest
Setting goals.
Learning a new topic
Operational-cognitive
Reflection
Lesson progress
Lesson stepsTeacher activities
Student activities
1. Organizational.
2 min
Greets students, checks that the workplace is ready for class, and creates a favorable, relaxed environment.
Divides into groups
Greet the teachers, check the availability of teaching materials
to work for class.
Divided into groups
2. Arouse interest
3 min
Game “Black Box”
1. There is information that these animals were bred in ancient Egypt more than four thousand years ago. In Mesopotamia they were kept in ponds.
Kept in Ancient Rome and Greece.
They first appeared in Europe only in the 17th century.
They first came to Russia from China as a gift to Tsar Alexei Mikhailovich. The king ordered them to be planted in crystal thickets.
In good conditions, it can live up to 50 years.
Fairy-tale character who makes wishes come true.
2. There is such a zodiac sign
Teacher: -So who will we meet in class today?
Students offer answers after each question.
Students: - goldfish.
And they set the topic of the lesson.
3.Setting goals
Goal: to activate cognitive interest in the topic being studied.
1) Let's get acquainted with the structural features of fish.
2) We will continue to develop the skills to observe living organisms, work with textbook text, perceive
1) Study the structural features of fish.
2) They will work with the text of the textbook, perceive
educational information through multimedia presentation.
4. Studying a new topic.
Operational-cognitive.
Goal: using various forms and working techniques to develop knowledge about the external and internal structure of fish
15 min
Guys, today we will get to know the most ancient vertebrates. Superclass of fish. This is the most numerous class of Chordates. There are about 20 thousand species. The branch of Zoology that studies fish is called ICHTHYOLOGY.
Stage I – Challenge (motivation).
Teacher: Sometimes they say about a person: “He feels like a fish in water.” How do you understand this expression?
Teacher: Why do fish feel good in water?
Teacher: How is the adaptation of fish to the aquatic environment expressed? We will learn this during today's lesson.
Stage II – maintenance.
What Features of the Aquatic Habitat can we name:
1 task. Watch the video fragment.
Using the textbook and additional text, using the Fishbone technique, describe the adaptation of fish to living in an aquatic environment.
Listening
Expected answers from students (it means he feels good, comfortable, everything works out for him).
(It is adapted to life in water).
The children write down the topic of the lesson in their notebook.
The high density of water makes active movement difficult.
Light penetrates water only to a shallow depth.
Limited amount of oxygen.
Water is a solvent (salts, gases).
Thermal water (temperature conditions are milder than on land).
Transparency. Fluidity.
Conclusion : the fish’s adaptability to life in water is manifested in the streamlined shape of the body, smoothly transitioning body organs, protective coloring, features of the integument (scales, mucus), sensory organs (lateral line), and locomotor organs (fins).
- What is the body shape of a fish and how is it adapted to its environment?
Teacher's addition.Man arranges for his movement in water by sharpening the bows of his boats and ships, and when building submarines he gives them a spindle-shaped, streamlined shape of a fish body). The body shape can be different: spherical (hedgehog fish), flat (stingray, flounder), serpentine (eels, moray eels).
What are the features of the body cover of a fish?
What is the significance of the slimy film on the surface of fish?
Teacher's addition. This mucous film helps reduce friction when swimming, and due to its bactericidal properties, prevents bacteria from penetrating the skin, because fish skin is permeable to water and some substances dissolved in it (fear hormone)
WHAT IS “THE STUFF OF FEAR”
In 1941, Nobel laureate Karl von Frisch, studying the behavior of fish, discovered that when a pike grabs a minnow, some substance gets into the water from wounds on its skin, which causes a fear reaction in other minnows: they first They scatter in all directions, and then form a dense flock and stop feeding for a while.
In modern scientific literature, instead of the phrase “fear substance,” you can often find the term “anxiety pheromone.” In general, pheromones are substances that, when released into the external environment by one individual, cause some specific behavioral reaction in other individuals.
In fish, the alarm pheromone is stored in special cells located in the uppermost layer of the skin. They are very numerous and in some fish they can occupy more than 25% of the total skin volume. These cells have no connections with the external environment, so their contents can get into the water only in one case - if the skin of the fish receives some kind of damage.
The largest number of alarm pheromone cells are concentrated on the front part of the fish’s body, including the head. The further back, towards the tail part of the body, the fewer cells with pheromone.
What are the coloring features of fish?
Bottom fish and fish of grassy and coral thickets often have a bright spotted or striped color (the so-called “dismembering” coloring masking the contours of the head). Fish can change their color depending on the color of the substrate.
What is a lateral line and what is its significance?
Drawing up a general Fishbone at the board .
The fish swims in the water quickly and nimbly; it easily cuts through water due to the fact that its body has a streamlined shape (in the form of a spindle), more or less compressed from the sides.
Reduced water friction
The body of fish is mostly covered with hard and dense scales, which sit in folds of the skin (how are our nails? , and their free ends overlap each other, like tiles on a roof. The scales grow along with the growth of the fish, and in the light we can see concentric lines reminiscent of growth rings on sections of wood. By the growths of concentric stripes, one can determine the age of the scales, and at the same time the age of the fish itself. Additionally, the scales are covered with mucus.
Body coloring. The fish has a dark back and a light belly. The dark coloring of the back makes them hardly noticeable against the background of the bottom when viewed from above; the shiny silver coloring of the sides and belly makes the fish invisible against the background of a light sky or sun glare when viewed from below.
The coloring makes the fish inconspicuous against the background of its habitat.
Side line. With its help, fish navigate water flows, perceive the approach and departure of prey, predators or school partners, and avoid collisions with underwater obstacles.
PHYS. JUST A MINUTE
Goal: maintaining health.
3 min
Doing exercises.
12 min
What other adaptations do fish have for living in water?
To do this, you will work in small groups. Do you have it on your tables? additional material. You must read the text material, answer the questions and indicate the structural features of the fish in the picture.
Gives assignments to each group:
"1. Read the text.
2. Look at the drawing.
3. Answer the questions.
4. Indicate the structural features of the fish in the drawing.”
Group 1. Organs of locomotion of fish.
2. How do they work?
Group 2. Respiratory system of fish.
Group 3. Sense organs of fish.
1. What sense organs do fish have?
2. Why are sense organs needed?
Students organize the search and exchange of ideas through dialogue.Work is being organized to fill out the drawing.
4. Reflective-evaluative.
Purpose: determining the level of knowledge acquired in the lesson.
7 min
Quest "Fishing"
1. What parts does the body of a fish consist of?
2. With the help of what organ does a fish perceive the flow of water?
3. What structural features of a fish help it overcome water resistance?
4. Does the fish have a passport?
5. Where is the fear substance found in fish?
6. Why do many fish have a light belly and a dark back?
7. What is the name of the branch of zoology that studies fish?
8. Why do flounder and stingray have a flat body shape?
9. Why can't fish breathe on land?
10. What sense organs do fish have?
11. Which fish fins are paired? Which fish fins are not paired?
12. What fins do fish use as oars?
Each team chooses a fish and answers questions.
3 min
A drawing of a fish is hung on the board. The teacher offers to evaluate today’s lesson, what new things you learned, etc.
1. Today I found out...
2. It was interesting...
3. It was difficult...
4. I learned...
5. I was surprised...
6. I wanted...
On multi-colored stickers, children write what they liked most in the lesson, what new things they learned and stick them on the fish in the form of scales.
5. Homework.
Describe the internal structure of a fish.
Make a crossword puzzle.
Write down homework in a diary.
Group 1. Musculoskeletal system fish.
1. What organs are the organs of movement of fish?
2. How do they work?
3. What groups can they be divided into?
Fin - this is a special organ necessary to coordinate and control the process of fish movement in water. Each fin consists of a thin leathery membrane, whichWhen the fin straightens, it stretches between the bony fin rays and thereby increases the surface of the fin itself.
The number of fins may vary between species, and the fins themselves may be paired or unpaired.
In river perch, unpaired fins are located on the back (there are 2 of them - large and small), on the tail (large two-lobed caudal fin) and on the underside of the body (the so-called anal fin).
The pectoral fins (the front pair of limbs) and the ventral fins (the rear pair of limbs) are paired.
The caudal fin plays an important role in the process of moving forward, the paired fins are necessary for turning, stopping and maintaining balance, the dorsal and anal fins help the perch maintain balance while moving and during sharp turns.
Group 2.Respiratory system of fish.
Read the text. Look at the drawing. Answer the questions.
Indicate the structural features of the fish in the picture.
1. What organs make up the respiratory system of fish?
2. What structure do gills have?
3. How does fish breathe? Why can't fish breathe on land?
The main respiratory organ of fish is the gills. The inert base of the gill is the gill arch.
Gas exchange occurs in the gill filaments, which have many capillaries.
The gill rakers “strain” the incoming water.
The gills have 3-4 gill arches. Each arch has bright red stripes on one side.gill filaments , and on the other - gill rakers . The gills are covered on the outsidegill covers . Visible between the arcsgill slits, which lead to the pharynx. From the pharynx, captured by the mouth, water washes the gills. When a fish presses its gill covers, water flows through the mouth to the gill slits. Oxygen dissolved in water enters the blood. When a fish lifts its gill covers, water is pushed out through the gill slits. Carbon dioxide leaves the blood into the water.
Fish cannot stay on land because the gill plates stick together and air does not enter the gill slits.
Group 3.Sense organs of fish.
Read the text. Look at the drawing. Answer the questions.
Indicate the structural features of the fish in the picture.
1. What organs make up the nervous system of a fish?
2. What sense organs do fish have?
3. Why are sense organs needed?
The fish have sense organs that allow fish to navigate their environment well.
1. Vision - eyes - distinguishes the shape and color of objects
2. Hearing - the inner ear - hears the steps of a person walking along the shore, the ringing of a bell, a shot.
3. Smell - nostrils
4. Touch - antennae.
5. Taste – sensitive cells – throughout the entire surface of the body.
6. The lateral line - a line along the entire body - perceives the direction and strength of the water flow. Thanks to the lateral line, even blinded fish do not bump into obstacles and are able to catch moving prey.
On the sides of the body, a lateral line is visible in the scales - a kind of organfeelings in fish. It is a channel that lies in the skin and has many receptors that perceive the pressure and force of water flow, electromagnetic fields of living organisms, as well as stationary objects due to wavesdeparting from them. Therefore, in muddy water and even in complete darkness, fish are perfectly oriented and do not stumble upon underwater objects. In addition to the lateral line organ, fish have sensory organs located on the head. In front of the head there is a mouth, with which the fish captures food and draws in water necessary for breathing. Located above the mouthnostrils are the olfactory organ through which fish perceive the odors of substances dissolved in water. On the sides of the head there are eyes, quite large with a flat surface - the cornea. The lens is hidden behind it. Pisces seeat close range and distinguish colors well. Ears are not visible on the surface of the fish's head, but this does not mean thatfish don't hear. They have an inner ear in their skull that allows them to hear sounds. Nearby is a balance organ, thanks to which the fish senses the position of its body and does not roll over.
Deep sea fish are considered some of the most amazing creatures on the planet. Their uniqueness is explained primarily by the harsh living conditions. 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 living conditions
As already mentioned, the depths of the oceans are not as densely populated as, say, the upper layers of 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.
- Life in the dark. With depth, the amount of light decreases sharply. It is believed that the maximum distance a sunbeam travels in water is 1000 meters. Below this level, no traces of light were detected. Therefore, deep-sea fish are adapted to life in complete darkness. Some species of fish do not have functioning eyes at all. The eyes of other representatives, on the contrary, are very developed, which makes it possible to capture even the weakest light waves. Another interesting adaptation is luminescent organs that can glow using the energy of chemical reactions. Such light not only facilitates movement, but also lures potential prey.
- High blood pressure. Another feature of deep-sea existence. That is why the internal pressure of such fish is much higher than that of their shallow-water relatives.
- Low temperature. With depth, the water temperature decreases significantly, so fish are adapted to life in such an environment.
- 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 over long distances, which in some cases can be measured in kilometers. By the way, such a device makes it possible to quickly hide from a larger predator.
You can see that fish living in the depths of the ocean are truly unique organisms. In fact, a huge area of the world's oceans still remains unexplored. That is why the exact number of deep-sea fish species is unknown.
Diversity of fish living in the depths of the water
Although modern scientists know only a small part of the population of the deep, there is information about some very exotic inhabitants of the ocean.
Bathysaurus- the deepest-sea predator fish, living at depths from 600 to 3500 m. They live in tropical and subtropical waters. This fish has almost transparent skin, large, well-developed sensory organs, and its oral cavity is lined with sharp teeth (even the tissues of the roof of the mouth 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 populate the depths. 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 existence without constant food - the fish’s stomachs are so stretched that they can wholeheartedly swallow a living creature much larger than themselves. And on the tail, fish have a specific luminous organ, with the help of which they lure out prey.
Monkfish- a rather unpleasant-looking creature with huge jaws, a small body and poorly developed muscles. 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 lifestyle. The fact is that most of them can only exist under certain conditions, in particular, at high pressure. Therefore, it is not possible to extract and study them - when they rise to the upper layers of water, they simply die.
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.Water temperature largely determines the intensity of the metabolic process in fish. Temperature changes in many; in cases, they are a natural irritant that determines the onset of spawning, migration, etc. Other physical and chemical properties of water, such as salinity, saturation; oxygen, viscosity are also of great importance.
DENSITY, VISCOSITY, PRESSURE AND MOVEMENT OF WATER.
WAYS OF FISH MOVEMENT
Fish live in an environment much more dense and viscous than air; This is associated with a number of features in their structure, functions, organs and behavior.
Fish are adapted to move in both still and flowing water. Water movements, both translational and oscillatory, play a very significant role in the life of fish. Fish are adapted to move through water in different ways and at different speeds. This is related to the shape of the body, the structure of the fins and some other features in the structure of fish.
Based on body shape, fish can be divided into several types (Fig. 2): ¦
- Torpedo-shaped - the best swimmers, inhabitants of the water column. This group includes mackerel, mullet, herring shark, salmon, etc.
- Arrow-shaped - close to the previous one, but the body is more elongated and the unpaired fins are moved back. Good swimmers, inhabitants of the water column, are garfish and itsuka.
- Laterally flattened, this type varies the most. It is usually classified into: a) bream type, b) sunfish type and c) flounder type. According to the habitat conditions, fish belonging to this type are also very diverse - from inhabitants of the water column (sunfish) to bottom-dwellers (bream) or bottom-dwellers (flounder):
- ;L e i t o vi d i y - body. , strongly elongated and flattened on the sides. Poor swimmer herring king - kegalecus. Trachypterus and others. . . , ’ (
- Spherical and - the body is almost spherical, the caudal fin is usually poorly developed - boxfish, some lumpfish, etc.
The downward movement is ensured
9
Rice. 2. Different types of fish body shape:
/ - arrow-shaped (garfish); 2 - torpedo-shaped (mackerel); 3 - laterally flattened, bream-like (common bream); 4 - type of fish-moon (moon-fish);
5 - type of flounder (river flounder); 6 - serpentine (eel); 7 - ribbon-shaped (herring king); 8 - spherical (body) 9 - flat (ramp)
- Flat - the body is flattened dorsoventrally, various slopes, monkfish.
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Rice. 3. Methods of movement: at the top - eel; below - cod. You can see how a wave goes through the body of the fish (from Gray, 1933)
Atnia calva L. Flounders swim by making oscillating movements with both their dorsal and anal fins. In the stingray, swimming is ensured by the oscillatory movements of the greatly enlarged pectoral fins (Fig. 4).
Rice. 4. Movement of fish using fins: anal (electric eel) or pectoral (stingray) (from Norman, 195 8)
The caudal fin mainly paralyzes the braking movement of the end of the body and weakens the reverse currents. According to the nature of their action, fish tails are usually divided into: 1) isobathic and chesny, where the upper and lower blades are equal in size; a similar type of tail is found in mackerel, tuna and many others; 2) e and ibatic, in which the upper lobe is better developed than the lower; this tail facilitates upward movement; this kind of tail is characteristic of sharks and sturgeons; 3) hypobatic, when the lower lobe of the tail is more developed than the upper and promotes downward movement; a hypobatic tail is found in flying fish, bream and some others (Fig. 5).
Rice. 5. Different types of fish tails (from left to right): epibatic, isobatic, hypobatic
The main function of the depth rudders in fish is performed by the pectoral, as well as the abdominal, muscles. With their help, the fish is partially rotated in a horizontal plane. The role of unpaired fins (dorsal and anal), if they do not carry the function of translational movement, is reduced to assisting the fish in turning up and down and only partly to the role of stabilizer keels (Vasnetsov, 1941).
The ability to bend the body more or less is naturally related to. its structure. Fish with a large number of vertebrae can bend their body more than fish with a small number of vertebrae. The number of vertebrae in fish ranges from 16 in the moon fish, to 400 in the belt fish. Also, fish with small scales can bend their bodies to a greater extent than fish with large scales.
To overcome the resistance of water, it is extremely important to minimize the friction of the body on the water. This is achieved by smoothing the surface as much as possible and lubricating it with appropriate friction-reducing substances. In all fish, as a rule, the skin has a large number of goblet glands, which secrete mucus that lubricates the surface of the body. The best swimmer among fish has a torpedo-shaped body.
The speed of fish movement is also related to the biological state of the fish, in particular, the maturity of the gonads. They also depend on the water temperature. Finally, the speed at which the fish moves can vary depending on whether the fish is moving in a school or alone. Highest speeds can reach some sharks, swordfish,
tunas. Blue shark - Carcharinus gtaucus L. - moves at a speed of about 10 m/sec, tuna - Thunnus tynnus L. - at a speed of 20 m/sec, salmon - Salmo salar L. - 5 m/sec. The absolute speed of movement of a fish depends on its size.’ Therefore, to compare the speed of movement of fish of different sizes, a speed coefficient is usually used, which is the quotient of the absolute speed of movement
fish by the square root of its length
Very fast moving fish (sharks, tuna) have a speed coefficient of about 70. Fast moving fish (salmon,
Rice. 6. Diagram of the movement of a flying fish during takeoff. Side and top view (from Shuleikin, 1953),
mackerel) have a coefficient of 30-60; moderately fast (herring, cod, mullet) - from 20 to 30; slow (for example, bream) - QX 10 to 20; slow (sculpins, scoriens) - from 5 to 10 and very slow (moon-fish, ba ) - less than 5.
/Good swimmers in flowing water are somewhat different in /body shape from good swimmers in still water, in particular/in the caudal peduncle the caudal peduncle is usually/ significantly higher, and “shorter than in the latter. As an example, we can compare the shape of the caudal peduncle of the trout, adapted to live in water with fast currents, and mackerel - an inhabitant of slow-moving and stagnant sea waters.
Swimming quickly, overcoming rapids and rifts, the fish get tired. They cannot swim for a long time without rest. With great stress, lactic acid accumulates in the blood of fish, which then disappears during rest. Sometimes fish, for example, when passing fish ladders, become so tired that after passing them they even die (Viask, 1958, etc.). In connection with. Therefore, when designing fish passages, it is necessary to provide them with appropriate places for fish to rest. -:
Among the fish there are representatives that have adapted to a kind of flight through the air. The best thing is
the property is developed in flying fish - Exocoetidae; Actually, this is not real flight, but soaring like a glider. In these fish, the pectoral fins are extremely developed and perform the same function as the wings of an airplane or glider (Fig. 6). The main engine that gives the initial speed during flight is the tail and, first of all, its lower blade. Having jumped to the surface of the water, the flying fish glides along the water surface for some time, leaving ring waves behind it, diverging to the sides. While the body of a flying fish is in the air, and only its tail remains in the water, it still continues to increase its speed of movement, the increase of which stops only after the fish’s body is completely separated from the surface of the water. A flying fish can stay in the air for about 10 seconds and fly a distance of over 100 miles.
Flying fish developed flight as a protective device that allows the fish to elude predators pursuing it - tuna, coryphen, swordfish, etc. Among the characin fish there are representatives (genus Gasteropelecus, Carnegiella, Thoracocharax) that have adapted to active flapping flight (Fig. 7). These are small fish up to 9-10 cm in length, inhabiting the fresh waters of South America. They can jump out of the water and fly with the help of strokes of their elongated pectoral fins up to 3-5 m. Although the flying haradinids have smaller pectoral fins than those of flying fish of the Exocoetidae family, the pectoral muscles that move the pectoral fins are much more developed. These muscles in characin fish, which have adapted to flapping flight, are attached to the very strongly developed bones of the shoulder girdle, which form some semblance of the pectoral keel of birds. The weight of the muscles of the pectoral fins reaches up to 25% of body weight in flying characinids, while in flightless representatives of the close genus Tetragonopterus - only 0.7%,
The density and viscosity of water, as is known, depends, first of all, on the content of salts in the water and its temperature. As the amount of salts dissolved in water increases, its density increases. On the contrary, with increasing temperature (above + 4 ° C), density and viscosity decrease, and viscosity is much more pronounced than density.
Living matter is usually heavier than water. Its specific gravity is 1.02-1.06. The specific gravity of fish of different species varies, according to A.P. Andriyashev (1944), for fish of the Black Sea from 1.01 to 1.09. Consequently, in order to stay in the water column, a fish “must have some special adaptations, which, as we will see below, can be quite diverse.
The main organ with which fish can regulate
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.
Rice. 7. Characin fish Gasteropelecus, adapted to flapping flight:
1 - general view; 2 - diagram of the structure of the shoulder girdle and the location of the fin:
a - cleithrum; b -,hupercoracoideum; c - hypocoracoibeum; g - pte* rigiophores; d - fin rays (from Sterba, 1959 and Grasse, 1958)
In fish with a swim bladder, such as, for example, horse mackerel - Trachurus, wrasses - Crenilabrus and Ctenolabrus, southern haddock - Odontogadus merlangus euxinus (Nordm.), etc., the specific gravity is somewhat less than in fish that do not have a swim bladder , namely; 1.012-1.021. In fish without a swim bladder [sea ruffe-Scorpaena porcus L., stargazer-Uranoscopus scaber L., gobies-Neogobius melanostomus (Pall.) and N. "fluviatilis (Pall.), etc.] the specific gravity ranges from 1. 06 to 1.09.
It is interesting to note the relationship between the specific gravity of a fish and its mobility. Of the fish that do not have a swim bladder, more mobile fish, such as the mullet - Mullus barbatus (L.) - have the lowest specific gravity (average 1.061), and the largest are bottom-dwelling, burrowing fish, such as the stargazer, specific gravity which averages 1.085. A similar pattern is observed in fish with a swim bladder. Naturally, the specific gravity of a fish depends not only on the presence or absence of a swim bladder, but also on the fat content of the fish, the development of bone formations (the presence of a shell) and IT. d.
The specific gravity of fish changes as it grows, and also throughout the year due to changes in its fatness and fat content. Thus, in the Pacific herring - Clupea harengus pallasi Val. - the specific gravity varies from 1.045 in November to 1.053 in February (Tester, 1940).
In most older groups of fish (among bony fish - almost all herrings and carp-like fish, as well as lungfishes, polyfins, bony and cartilaginous ganoids), the swim bladder is connected to the intestine using a special duct - the ductus pneumaticus. In other fish - perciformes, codfishes and other* teleosts, the connection between the swim bladder and the intestine is not preserved in adulthood.
In some herrings and anchovies, for example, oceanic herring - Clupea harengus L., sprat - Sprattus sprattus (L.), anchovies - Engraulis encrasicholus (L.), the swim bladder has two openings. In addition to the ductus pneumaticus, in the back of the bladder there is also an external opening that opens directly behind the anal opening (Svetovidov, 1950). This hole allows the fish, when quickly diving or rising from depth to the surface, to remove excess gas from the swim bladder in a short time. At the same time, in a fish descending to depth, excess gas appears in the bladder under the influence of water pressure on its body, which increases as the fish dives. If it rises with a sharp decrease in external pressure, the gas in the bubble tends to occupy as much volume as possible, and therefore the fish is often forced to remove it.
A school of herring rising to the surface can often be detected by numerous air bubbles rising from the depths. In the Adriatic Sea off the coast of Albania (Gulf of Vlora, etc.), when fishing for sardines, Albanian fishermen unmistakably predict the imminent appearance of this fish from the depths by the appearance of gas bubbles released by it. The fishermen say: “The foam has appeared, now the sardine will appear” (report by G. D. Polyakov).
Filling of the swim bladder with gas occurs in open-bladder fish and, apparently, in most fish with a closed bladder, not immediately after exiting the egg. While hatched free embryos go through a resting stage, suspended from plant stems or lying on the bottom, they have no gas in their swim bladder. Filling of the swim bladder occurs due to the ingestion of gas from the outside. In many fish, the duct connecting the intestine to the bladder is absent in the adult state, but in their larvae it is present, and it is through it that their swim bladder is filled with gas. This observation is confirmed by the following experiment. Larvae were hatched from the eggs of perch fish in a vessel in which the surface of the water was separated from the bottom by a thin mesh, impenetrable to the larvae. Under natural conditions, the filling of the bladder with gas occurs in perch fish on the second or third day after emerging from the eggs. In the experimental vessel, the fish were kept until five to eight days of age, after which the barrier separating them from the surface of the water was removed. However, by this time the connection between the swim bladder and the intestines was interrupted, and the bladder remained empty of gas. Thus, the initial filling of the swim bladder with gas occurs in the same way in both open-vesical and most fish with a closed swim-bladder.
In pike perch, gas appears in the swim bladder when the fish reaches approximately 7.5 mm in length. If by this time the swim bladder remains unfilled with gas, then the larvae with an already closed bladder, even having the opportunity to swallow gas bubbles, fill the intestines with them, but the gas no longer enters the bladder and exits through their anus (Kryzhanovsky, Disler and Smirnova, 1953).
From vascular system(for unknown reasons) the release of gas into the swim bladder cannot begin until at least a little gas enters it from the outside.
Further regulation of the amount and composition of gas in the swim bladder in different fish is carried out in different ways. In fish that have a connection between the swim bladder and the intestine, the entry and release of gas from the swim bladder occurs largely through the ductus pneumaticus. In fish with a closed swim bladder, after the initial filling with gas from the outside, further changes in the quantity and composition of the gas occur through its release and absorption by the blood. Such fish have a bladder on the inner wall. The red body is an extremely dense formation permeated with blood capillaries. Thus, in the two red bodies located in the swim bladder of the eel, there are 88,000 venous and 116,000 arterial capillaries with a total length of 352 and 464 m. 3 at the same time, the volume of all capillaries in the red bodies of the eel is only 64 mm3, i.e. i.e. no more than a drop average size. The red body varies in different fish from a small spot to a powerful gas-secreting gland consisting of columnar glandular epithelium. Sometimes the red body is also found in fish with a ductus pneumaticus, but in such cases it is usually less developed than in fish with a closed bladder.
The composition of the gas in the swim bladder differs between different species of fish and different individuals of the same species. Thus, tench usually contains about 8% oxygen, perch - 19-25%, pike* - about 19%, roach - 5-6%. Since mainly oxygen and carbon dioxide can penetrate from the circulatory system into the swim bladder, these gases usually predominate in a filled bladder; nitrogen makes up a very small percentage. On the contrary, when gas is removed from the swim bladder through circulatory system, the percentage of nitrogen in the bubble increases sharply. As a rule, marine fish have more oxygen in their swim bladder than freshwater fish. Apparently, this is mainly due to the predominance of forms with a closed swim bladder among marine fish. The oxygen content in the swim bladder of secondary deep-sea fish is especially high.
І
Gas pressure in the swim bladder of fish is usually transmitted in one way or another to the auditory labyrinth (Fig. 8).
Rice. 8. Diagram of the connection between the swim bladder and the hearing organ in fish (from Kyle and Ehrenbaum, 1926; Wunder, 1936 and Svetovidova, 1937):
1 - in the oceanic herring Clupea harengus L. (herring-like); 2 carp Cyprinus carpio L. (cyprinids); 3* - in Physiculus japonicus Hilgu (codfish)
Thus, in herrings, cods and some other fish, the anterior part of the swim bladder has paired outgrowths that reach the membrane-covered openings of the auditory capsules (in cods), or even go inside them (in herrings). In cyprinids, the pressure of the swim bladder is transmitted to the labyrinth using the so-called Weber's apparatus - a series of bones connecting the swim bladder to the labyrinth.
The swim bladder serves not only to change the specific gravity of the fish, but it also plays the role of an organ that determines the amount of external pressure. In a number of fish, for example,
in most loaches - Cobitidae, leading a bottom lifestyle, the swim bladder is greatly reduced, and its function as an organ that perceives changes in pressure is the main one. Fish can perceive even slight changes in pressure; their behavior changes when atmospheric pressure changes, for example, before a thunderstorm. In Japan, some fish are specially kept in aquariums for this purpose and the upcoming change in weather is judged by changes in their behavior.
With the exception of some herrings, fish with a swim bladder cannot quickly move from the surface layers to the depths and back. In this regard, in most species that make rapid vertical movements (tuna, common mackerel, sharks), the swim bladder is either completely absent or reduced, and retention in the water column is carried out due to muscular movements.
The swim bladder is also reduced in many bottom fish, for example, in many gobies - Gobiidae, blennies - Blenniidae, loaches - Cobitidae and some others. The reduction of the bladder in bottom fish is naturally associated with the need to provide a greater specific body weight. In some closely related species of fish, the swim bladder is often developed to varying degrees. For example, among gobies, some leading a pelagic lifestyle (Aphya) it is present; in others, such as Gobius niger Nordm., it is preserved only in pelagic larvae, the larvae of which also lead a bottom lifestyle, for example, in Neogobius melanostomus (Pall.), the swim bladder is also reduced in larvae and adults.
In deep-sea fish, due to life at great depths, the swim bladder often loses connection with the intestines, since under enormous pressure the gas would be squeezed out of the bladder. This is characteristic even of those groups, for example, Opistoproctus and Argentina from the herring order, in which species living near the surface have a ductus pneumaticus. In other deep-sea fish, the swim bladder may be completely reduced, as, for example, in some Stomiatoidei.
Adaptation to life at great depths causes other serious changes in fish that are not directly caused by water pressure. These peculiar adaptations are associated with the lack of natural light at depths^ (see p. 48), feeding habits (see p. 279), reproduction (see p. 103), etc.
By their origin, deep-sea fish are heterogeneous; they come from different orders, often far apart from each other. At the same time, the time of transition to deep
. Rice. 9. Deep Sea Fish:
1 - Cryptopsarus couesii (Q111.); (leg-feathered); 2-Nemichthys avocetta Jord et Gilb (eel-borne); .3 - Ckauliodus sloani Bloch et Schn, (herrings): 4 - Jpnops murrayi Gunth. (glowing anchovies); 5 - Gasrostomus batrdl Gill Reder. (eels); 6 -x4rgyropelecus ol/ersil (Cuv.) (glowing anchovies); 7 - Pseudoliparis amblystomopsis Andr. (perciformes); 8 - Caelorhynchus carminatus (Good) (long-tailed); 9 - Ceratoscopelus maderensis (Lowe) (glowing anchovies)
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 the 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. Adaptations of this kind in the form of various spines and outgrowths, which increase the surface of the body and help keep it in the water column, are found in many pelagic animals, including
Rice. 10. Pelagic fish eggs (not to scale):
1 - anchovy Engraulus encrasichlus L.; 2 - Black Sea herring Caspialosa kessleri pontica (Eich); 3 - glider Erythroculter erythrop"erus (Bas.) (cyprinids); 4 - mullet Mullus barbatus ponticus Essipov (perciformes); 5 - Chinese perch Siniperca chuatsi Bas. (perciformes); 6 - flounder Bothus (Rhombus) maeoticus (Pall.) ; 7 snakehead Ophicephalus argus warpachowskii Berg (snakeheads) (according to Kryzhanovsky, Smirnov and Soin, 1951 and Smirnov, 1953) *
in fish larvae (Fig. 11). For example, the pelagic larva of the bottom fish monkfish - Lophius piscatorius L. - has long outgrowths of the dorsal and pelvic fins, which help it soar in the water column; similar changes in the fins are also observed in the Trachypterus larva. Moonfish larvae - . Mota mola L. - have huge spines on their body and somewhat resemble an enlarged planktonic algae, Ceratium.
In some pelagic fish larvae, the increase in their surface occurs through strong flattening of the body, as, for example, in the larvae of the river eel, whose body is much higher and flatter than that of adult individuals.
In the larvae of some fish, for example, red mullet, even after the embryo has emerged from the shell, a powerfully developed fat drop retains the role of a hydrostatic organ for a long time.
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, 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,
Rice. 12. Suckers for attaching river fish to the ground: Mika - Glyptothorax (left) and Garra from Cyprinidae (right) (from Noga, 1933 and Annandab, 1919)
^ some Asian (Barbus brachycephalus Kpssl., Barbus "tor, Ham.) and African (Barbus radcliffi Blgr.) species of longhorned beetles and many others.
^.3. Small bottom-dwelling fish that usually live between rocks at the bottom of a stream and swim from rock to rock. These fish, as a rule, have a spindle-shaped, slightly elongated shape.
This includes many loaches - Nemachil"us, gudgeon" - Gobio, etc.
4. Forms that have special attachment organs (suction cups; spikes), with the help of which they are attached to bottom objects (Fig. 12). Typically, fish belonging to this group have a dorsoventrally flattened body shape. The sucker is formed either on the lip (Garra, etc.) or between
Rice. 13. Cross-section of various fish of fast-moving waters (top row) and slow-moving or stagnant waters (bottom row). On the left is nappavo vveohu - y-.o-
pectoral fins (Glyptothorax), or by fusion of the ventral fins. This group includes Discognathichthys, many species of the family Sisoridae, and the peculiar tropical family Homalopteridae, etc.
As the current slows down when moving from the upper reaches to the lower reaches of the river, fish that are unadapted to overcome high current speeds, such as rail, minnow, char, and sculpin, begin to appear in the riverbed; in- In fish that live in the waters
zu -bream, crucian carp, carp, roach, red- with Slow current, body
noperka. Fish taken at the same height are more flattened, AND THEY usually
’ not so good swimmers,
as inhabitants of fast rivers (Fig. 13). The gradual change in the body shape of a fish from the upper to the lower reaches of the river, associated with a gradual change in the flow speed, is natural. In those places of the river where the flow slows down, fish that are not adapted to life in a fast flow are kept, while in places with extremely fast water movement, only forms adapted to overcoming the current are preserved; typical inhabitants of a fast stream are rheophiles, Van dem Borne, using the distribution of fish along the stream, divides the rivers Western Europe to separate areas;
- trout section - the mountainous part of the stream with a fast current and rocky soil is characterized by fish with a ridged body (trout, char, minnow, sculpin);
- barbel section - flat current, where the flow speed is still significant; fish with a taller body appear, such as barbel, dace, etc.;?,
- bream area - the current is slow, the soil is partly silt, partly sand, underwater vegetation appears in the channel, fish with a laterally flattened body predominate, such as bream, roach, rudd, etc.
usually happens very gradually, but in general the areas outlined by Borne are distinguished quite clearly in most rivers with mountain feeding, and the patterns he established for the rivers of Europe are preserved both in the rivers of America, Asia and Africa.
(^(^4gt; forms of the same species living in flowing and stagnant water differ in their adaptability to the flow. For example, grayling - Thymallus arcticus (Pall.) - from Baikal has a higher body and a longer tail stem, while representatives of the same species from the Angara are shorter-bodied and have short tails, which is characteristic of good swimmers. Weaker young specimens of river fish (barbel, loaches), as a rule, have a lower ridged body and a shortened tail compared to adults. stem. In addition, usually in mountain rivers, adult, larger and stronger individuals stay higher upstream than young ones. If you move upstream of the river, then the average sizes of individuals of the same species, for example, comb-tailed and Tibetan loaches. increase, and the largest individuals are observed near the upper limit of the species’ distribution (Turdakov, 1939).
UB River currents affect the fish’s body not only mechanically, but also indirectly, through other factors. As a rule, bodies of water with fast currents are characterized by * oversaturation with oxygen. Therefore, rheophilic fish are at the same time oxyphilic, that is, oxygen-loving; and, conversely, fish inhabiting slowly flowing or stagnant waters are usually adapted to different oxygen regimes and better tolerate oxygen deficiency. . -
The current, influencing the nature of the stream's soil, and thereby the nature of bottom life, naturally affects the feeding of fish. So, in the upper reaches of rivers, where the soil forms motionless blocks. Usually a rich periphyton can develop,* serving as the main food for many fish in this section of the river. Because of this, upper-water fish are characterized, as a rule, by a very long intestinal tract adapted for digesting plant foods, as well as the development of a horny sheath on the lower lip. As you move down the river, the soils become shallower and, under the influence of the current, become mobile. Naturally, rich bottom fauna cannot develop on moving soils, and fish switch to feeding on fish or food falling from land. As the flow slows down, the soil gradually begins to silt, the development of bottom fauna begins, and herbivorous fish species with a long intestinal tract again appear in the riverbed.
33
The flow in rivers affects not only the structure of the fish’s body. First of all, the reproduction pattern of river fish changes. Many inhabitants of fast-flowing rivers
3 G. V. Nikolsky
have sticky eggs. Some species lay their eggs by burying them in the sand. American catfish from the genus Plecostomus lay eggs in special caves; other genera (see reproduction) carry eggs on their ventral side. The structure of the external genital organs also changes. In some species, sperm motility develops for a shorter period of time, etc.
Thus, we see that the forms of adaptation of fish to the flow in rivers are very diverse. In some cases, sudden movements of large masses of water, for example, forceful or silt-breaks of dams in mountain lakes, can lead to mass death of ichthyofauna, as, for example, happened in Chitral (India) in 1929. The speed of the current sometimes serves as an isolating factor, leading to the separation of the fauna of individual reservoirs and promoting its isolation. Thus, for example, the rapids and waterfalls between the large lakes of East Africa are not an obstacle for strong large fish, but are impassable for small ones and lead to the isolation of faunas thus separated sections of reservoirs:
“It is natural that the most complex and unique adaptations” to life in fast currents are developed in fish that live in mountain rivers, where the speed of water movement reaches its greatest value.
According to modern views, the fauna of mountain rivers at moderate low latitudes of the northern hemisphere are relics of the Ice Age. (By the term “relict” we mean those animals and plants, the area of distribution of which is separated in time or space from the main area of distribution of a given faunal or floristic complex.) “The fauna of mountain streams of tropical and, partially, temperate latitudes of non-glacial origin, but developed as a result of the gradual migration of “organisms to high mountain reservoirs from the plains - ¦¦: \
: For a number of groups, the ways of adaptation: to: life. in mountain streams can be traced quite clearly and can be restored (Fig. 14). --.That;
Both in rivers and in standing reservoirs, currents have a very strong influence on fish. But while in rivers the main adaptations are developed to the direct mechanical effect of moving molasses, the influence of currents in seas and lakes affects more indirectly - through changes caused by the current - in the distribution of other environmental factors (temperature, salinity, etc. It is natural, of course, that adaptations to the direct mechanical effects of water movement are also developed in fish in stagnant bodies of water. The mechanical influence of currents is primarily expressed in the transfer of fish, their larvae and eggs, sometimes over vast distances. For example, the larvae of
di - Clupea harengus L., hatched off the coast of northern Norway, are carried by the current far to the northeast. The distance from Lofoten, the herring spawning place, to the Kola meridian takes about three months for the herring fry to travel. Pelagic eggs of many fish also re-
Єіуртернім, івіятимер.) /
/n - Vi-
/ SshshShyim 9IURT0TI0YAYAL (RYAUIIII RDR)
will show
Let's pull it out
(myasmgg?ggt;im)
are carried by currents sometimes over very long distances. For example, flounder eggs laid off the coast of France belong to the shores of Denmark, where the hatching of juveniles occurs. The movement of eel larvae from spawning grounds to the mouths of European rivers is largely
its part is timed |
GlWOStlPHUH-
(sTouczm etc.)
spos^-
1І1IM from South to North. line of catfish of the family "YiShІЇ"pV
Minimum speeds in relation to two main factors
the meanings of which are inspired by mountain streams.; The diagram shows
tions to which the species reacts has become less rheophilic
the fish is apparently of the order of 2- (iz Noga, G930).
10 cm/sec. Hamsa - - Engraulis "¦¦¦
encrasichalus L. - begins to re- 1
react to the current at a speed of 5 cm/sec, but for many species these threshold reactions have not been established. -
The organ that perceives the movement of water are the cells of the lateral line. In their simplest form, this is the case in sharks. a number of sensory cells located in the epidermis. In the process of evolution (for example, in a chimera), these cells are immersed in a canal, which gradually (in bony fishes) closes and is connected to the environment only through 1 tubes that pierce the scales and form a lateral line, which is developed in different fish in different ways. The lateral line organs innervate the nervus facialis and n. vagus. In herrings, the lateral line canals are only in the head; in some other fish, the lateral line is incomplete (for example, in the crown and some minnows). With the help of the lateral line organs, the fish perceives movement and vibrations of water. Moreover, in many marine fish, the lateral line serves mainly to sense the oscillatory movements of water, and in river fish it also allows one to navigate the current (Disler, 1955, 1960).
The indirect influence of currents on fish is much greater than the direct one, mainly through changes in the water regime. Cold currents running from north to south allow arctic forms to penetrate far into the temperate region. For example, the cold Labrador Current pushes far to the south the spread of a number of warm-water forms, which move far to the north along the coast of Europe, where the warm Gulf Stream has a strong effect. In the Barents Sea, the distribution of individual high Arctic species of the family Zoarciaae is confined to areas of cold water located between the jets of warm currents. Warm-water fish, such as mackerel and others, stay in the branches of this current.
GT changes can radically change the chemical regime of a reservoir and, in particular, influence its salinity, introducing more salty or fresh water. Thus, the Gulf Stream introduces more salty water into the Barents Sea, and more salt-water organisms are associated with its streams. The currents formed by fresh waters carried by Siberian rivers, the distribution of whitefish and Siberian sturgeon is largely confined to the distribution of whitefish and Siberian sturgeon. At the junction of cold and warm currents, a zone of very high productivity, since in such areas there is a massive die-off of invertebrates and plankton plants, which provide enormous production of organic matter, which allows a few eurythermal forms to develop in mass quantities. Examples of this kind of junctions of cold and warm waters are quite common, for example, near the western coast of South America near Chile, on the Newfoundland banks, etc.
Vertical water currents play a significant role in the life of fish. The direct mechanical effect of this factor is rarely observed. Typically, the influence of vertical circulation causes mixing of the lower and upper layers of water, and thereby equalizing the distribution of temperature, salinity and other factors, which, in turn, creates favorable conditions for vertical migrations of fish. So, for example, in the Aral Sea, far from the shores in spring and autumn, the roach rises at night behind the beggar into the surface layers and during the day descends into the bottom layers. In the summer, when a pronounced stratification is established, the roach stays in the bottom layers all the time -
The oscillatory movements of water also play a large role in the life of fish. The main form of oscillatory movements of water, which is of greatest importance in the life of fish, is disturbances. Disturbances have various effects on fish, both direct, mechanical, and indirect, and are associated with the development of various adaptations. During strong unrest In the sea, pelagic fish usually descend into deeper layers of water, where they do not feel waves. Waves in coastal areas have a particularly strong effect on fish, where the force of the wave reaches up to one and a half tons.
Those living in the coastal zone are characterized by special devices that protect them, as well as their eggs, from the influence of the surf. Most coastal fish are capable of *
per 1 m2. For fish/living/
hold in place during
surf time V against- Fig- 15- Abdominals modified into sucker. . l l "fins of sea fish:
BUT THEY would be on the left - the goby Neogobius; on the right - the prickly ones are broken on the stones. Thus, the lumpfish Eumicrotremus (from Berg, 1949 and, for example, typical obi- Perminova, 1936)
tatels of coastal waters - various Gobiidae gobies, have pelvic fins modified into a suction cup, with the help of which the fish are held on the stones; Lumpfish have suckers of a slightly different nature - Cyclopteridae (Fig. 15).
The Unrest not only directly mechanically affects the fish, but also has a great indirect effect on them, promoting mixing of the water and immersion to the depth of the temperature jump layer. For example, in the last pre-war years, due to a decrease in the level of the Caspian Sea, as a result of an increase in the mixing zone, the upper boundary of the bottom layer, where the accumulation of nutrients occurs, also decreased. Thus, part of the nutrients entered the cycle of organic matter in the reservoir, causing an increase in the amount of plankton, and thereby, consequently, the food supply for the Caspian planktivorous fish. Another type of oscillatory movements of sea waters that are of great importance in the life of fish are tidal movements, which in some areas of the sea are quite significant. Thus, off the coast of North America and in the northern part of the Okhotsk region, the difference in tidal levels reaches more than 15 m. Naturally, fish living in the tidal zone periodically dry out, or in coastal areas of the sea, above which there are four. Huge masses of water rush through every day; they have special adaptations for living in small puddles remaining after low tide. All inhabitants of the intertidal zone (littoral) have a dorsoventrally flattened, serpentine or valval body shape. Tall-bodied fish, except flounders lying on their sides, are not found in the littoral zone. Thus, on Murman, the eelpout - Zoarces viuiparus L. and the butterfish - Pholis gunnelus L. - species with an elongated body shape, as well as large-headed sculpins, mainly Myoxocephalus scorpius L., usually remain in the littoral zone.
Peculiar changes occur in the biology of reproduction in fish of the intertidal zone. Many of the fish in particular; Sculpins move away from the littoral zone during spawning. Some species acquire the ability to give birth viviparously, such as the eelpout, whose eggs undergo an incubation period in the mother's body. The lumpfish usually lays its eggs below the low tide level, and in those cases when its eggs dry out, it pours water on it from its mouth and splashes it with its tail. The most curious adaptation to reproduction in the intertidal zone is observed in American fish? ki Leuresthes tenuis (Ayres), which lays eggs at spring tides in that part of the intertidal zone that is not covered by quadrature tides, so that the eggs develop outside the water in a humid atmosphere. The incubation period lasts until the next syzygy, when the juveniles emerge from the eggs and go into the water. Similar adaptations to reproduction in the littoral zone are also observed in some Galaxiiformes. Tidal currents, as well as vertical circulation, also have an indirect effect on fish, mixing bottom sediments and thus causing better development of their organic matter, and thereby increasing the productivity of the reservoir.
The influence of this form of water movement, such as tornadoes, stands somewhat apart. Capturing huge masses of water from the sea or inland reservoirs, tornadoes transport it along with all animals, including fish, over considerable distances. In India, during the monsoons, fish rains quite often occur, when usually, along with the rain, fish falls to the ground. live fish. Sometimes these rains cover quite large areas. Similar fish rains occur in various parts of the world; they are described for Norway, Spain, India and a number of other places. The biological significance of fish rains is undoubtedly primarily expressed in facilitating the dispersal of fish, and with the help of fish rains obstacles can be overcome under normal conditions. fish are irresistible.
Thus/as can be seen from the above, the forms of influence of water movement on fish are extremely diverse and leave an indelible imprint on the fish’s body in the form of specific adaptations that ensure the fish’s existence in different conditions. ¦
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, part of the fish is 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 assigned 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 species of fish burrow into the ground only in times of danger or when the reservoir dries out.
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. Of 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 buries itself in 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 bury 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.
Rice. 16. Pectoral fins resting on the ground of fish:
I - polypteri; 2 - gurnard (trigles) (Perclformes); 3- Ogcocephaliis (Lophiiformes)
pamy, and not a solid mass, thereby allowing pronation and supination. The same is observed in Lophius. However, the musculature of Lophius is homologous to the musculature of other bony fishes, and all changes towards the limbs of tetrapods are the result of adaptation to a similar function. Using its limbs as legs, Lophius moves very well along the bottom. Lophius and the polypterus have many common features in the structure of the pectoral fins, but in the latter there is a shift of muscles from the surface of the fin to the edges to an even lesser extent than in Lophius. We observe the same or similar direction of changes and the transformation of the forelimb from a swimming organ into a support organ in the jumper - Periophthalmus. The jumper lives in mangroves and spends much of its time on land. On the shore, it chases terrestrial insects, which it feeds on. “This fish moves on land by jumping, which it makes with the help of its tail and pectoral fins.
The trigla has a unique adaptation for crawling on the ground. The first three rays of its pectoral fin are separated and have acquired mobility. With the help of these rays, the trigla crawls along the ground. They also serve as an organ of touch for fish. Due to the special function of the first three rays, some anatomical changes also occur; in particular, the muscles that move the free rays are much more developed than all the others (Fig. 17).
Rice. 17. Musculature of the rays of the pectoral fin of the sea cock (triggles). Enlarged muscles of the free rays are visible (from Belling, 1912).
The representative of the labyrinths - the slider - Anabas, moving but drier, uses pectoral fins and sometimes gill covers for movement.
In the life of fish, not only soil plays an important role, but also solid particles suspended in water.
Water transparency is very important in the life of fish (see page 45). In small inland reservoirs and coastal areas of the seas, water transparency is largely determined by the admixture of suspended mineral particles.
Particles suspended in water affect fish in a variety of ways. Suspensions of flowing water, where the content of solid particles often reaches up to 4% by volume, have the strongest effect on fish. Here, first of all, the direct mechanical influence of mineral particles of various sizes carried in the water is felt - from several microns to 2-3 cm in diameter. In this regard, fish from muddy rivers develop a number of adaptations, such as a sharp decrease in eye size. Small-eyedness is characteristic of shovelnose, loach - Nemachilus and various catfish living in turbid waters. The reduction in the size of the eyes is explained by the need to reduce the unprotected surface, which can be damaged by the suspension carried by the flow. The small-eyed nature of loaches is also due to the fact that these and bottom-dwelling fish are guided by food mainly using the organs of touch. In the process of individual development, their eyes become relatively smaller as the fish grows and the appearance of antennae and the associated transition to bottom feeding (Lange, 1950).
The presence of a large amount of suspended matter in the water should naturally make it difficult for fish to breathe. Apparently, in this regard, in fish living in turbid waters, the mucus secreted by the skin has the ability to very quickly precipitate particles suspended in the water. This phenomenon has been studied in most detail for the American lepidoptera - Lepidosiren, the coagulating properties of whose mucus help it live in the thin silt of Chaco reservoirs. For Phisoodonophis boro Ham. It has also been established that its mucus has a strong ability to precipitate suspension. Adding one or two drops of mucus secreted by the skin of the fish to 500 cc. cm of turbid water causes sedimentation of suspension in 20-30 seconds. Such rapid sedimentation leads to the fact that even in very muddy water, the fish live as if surrounded by a case of clean water. The chemical reaction of the mucus itself, secreted by the skin, upon contact with muddy water, is changing. Thus, it has been established that the pH of mucus sharply decreases upon contact with water, falling from 7.5 to 5.0. Naturally, the coagulating property of mucus is important as a way to protect the gills from clogging with suspended particles. But despite the fact that fish living in turbid waters have a number of adaptations to protect themselves from the effects of suspended particles, if the amount of turbidity exceeds a certain value, the death of the fish may occur. In this case, death apparently occurs from suffocation as a result of clogging of the gills with sediment. Thus, there are known cases when, during heavy rains, when the turbidity of the streams increased tens of times, there was a massive death of fish. A similar phenomenon has been recorded in the mountainous regions of Afghanistan and India. At the same time, even fish so adapted to life in turbid water, such as the Turkestan catfish, Glyptosternum reticulatum Me Clel, died. - and some others.
LIGHT, SOUND, OTHER VIBRATIONAL MOTIONS AND FORMS OF RADIANT ENERGY
Light and, to a lesser extent, other forms of radiant energy play a very important role in the life of fish. Other oscillatory movements with a lower oscillation frequency, such as sounds, infra- and, apparently, ultrasounds, are also important in the life of fish. Electric currents, both natural and emitted by fish, are also of known importance for fish. With its senses, fish are adapted to perceive all these influences.
j Light /
Lighting is very important, both direct and indirect, in the life of fish. In most fish, the organ of vision plays a significant role in orienting during movement to prey, a predator, other individuals of the same species in the school, to stationary objects, etc.
Only a few fish have adapted to live in complete darkness in caves and artesian waters or in very weak artificial light produced by animals at great depths. "
The structure of the fish - its organ of vision, the presence or absence of luminescent organs, the development of other sensory organs, coloring, etc. - is associated with the characteristics of lighting. The behavior of the fish is also largely related to illumination, in particular, the daily rhythm of its activity and many other aspects of life. Light also has a certain effect on the course of fish metabolism and the maturation of reproductive products. Thus, for most fish, light is a necessary element of their environment.
Lighting conditions in water can be very different and depend, in addition to the strength of illumination, on the reflection, absorption and scattering of light and many other reasons. A significant factor determining the illumination of water is its transparency. The transparency of water in different bodies of water is extremely diverse, ranging from the muddy, coffee-colored rivers of India, China and Central Asia, where an object immersed in water becomes invisible as soon as it is covered with water, and ending with the clear waters of the Sargasso Sea (transparency 66.5 m), the central part of the Pacific Ocean (59 m) and a number of other places where the white circle - the so-called Secchi disk, becomes invisible to the eye only after diving to a depth of more than 50 m. Naturally, the lighting conditions in different bodies of water, located even at the same latitudes at the same depth are very different, not to mention different depths, because, as is known, with depth the degree of illumination quickly decreases. Thus, in the sea off the coast of England, 90% of light is absorbed already at a depth of 8-9 M.
Fish perceive light using the eye and light-sensitive kidneys. The specificity of lighting in water determines the specific structure and function of the fish's eye. As Beebe's experiments (1936) showed, the human eye can still discern traces of light under water at a depth of about 500 m. At a depth of 1,000 m, a photographic plate turns black after exposure for 1 hour 10 minutes, and at a depth of 1,700 m, a photographic plate turns black after exposure for 1 hour 10 minutes. even after a 2-hour exposure does not detect any changes. Thus, animals living from a depth of about 1,500 m to the maximum depths of the world's oceans over 10,000 m are completely unaffected by daylight and live in complete darkness, disturbed only by the light emanating from the luminescent organs of various deep-sea animals.
-Compared to Humans and other terrestrial vertebrates, fish are more myopic; her eye has a significantly shorter focal length. Most fish clearly distinguish objects within a range of about one meter, and the maximum range of vision of fish apparently does not exceed fifteen meters. Morphologically, this is determined by the presence in fish of a more convex lens compared to terrestrial vertebrates. In bony fish: accommodation of vision is achieved using the so-called falciform process, and in sharks - the ciliated body. "
The horizontal field of vision of each eye in an adult fish reaches 160-170° (data for trout), i.e., greater than that of a human (154°), and the vertical field of vision in a fish reaches 150° (in a human - 134°). However, this vision is monocular. The binocular field of vision in trout is only 20-30°, while in humans it is 120° (Baburina, 1955). Maximum visual acuity in fish (minnow) is achieved at 35 lux (in humans - at 300 lux), which is associated with the fish’s adaptation to less illumination in water compared to air. The quality of a fish's vision is related to the size of its eye.
Fish, whose eyes are adapted to vision in the air, have a flatter lens. In the American four-eyed fish1 - Anableps tetraphthalmus (L.) upper part The eyes (lens, iris, cornea) are separated from the lower horizontal partition. In this case, the upper part of the lens has a flatter shape than the lower part, adapted for vision in water. This fish, swimming near the surface, can simultaneously observe what is happening both in the air and in the water.
One of the tropical species In the blenny - Dialotnus fuscus Clark, the eye is divided transversely by a vertical partition, and the fish can see the front part of the eye outside the water, and the back part in the water. Living in the recesses of the drainage zone, it often sits with the front part of its head out of the water (Fig. 18). However, fish that do not expose their eyes to the air can also see outside the water.
While underwater, the fish can see only those objects that are at an angle of no more than 48.8° to the vertical of the eye. As can be seen from the above diagram (Fig. 19), the fish sees air objects as if through a round window. This window expands as it dives and narrows as it rises to the surface, but the fish always sees at the same angle of 97.6° (Baburina, 1955).
Fish have special adaptations for vision in different light conditions. The retinal rods are adapted to
Rice. 18. Fish, whose eyes are adapted to vision both in water and in air. Above - four-eyed fish Anableps tetraphthalmus L.;
on the right is a section of her eye. ’
Below - four-eyed blenny Dialommus fuscus Clark; "
a - aerial vision axis; b - dark partition; c - axis of underwater vision;
g - lens (according to Schultz, 1948), ?
They perceive weaker light and, in daylight, sink deeper between the pigment cells of the retina, which shield them from light rays. The cones, adapted to perceive brighter light, move closer to the surface in strong light.
Since the upper and lower parts of the eye are illuminated differently in fish, the upper part of the eye perceives more rarefied light than the lower part. In this regard, the lower part of the retina of most fish contains more cones and fewer rods per unit area. -
Significant changes occur in the structures of the organ of vision during ontogenesis.
In juvenile fish that consume food from the upper layers of water, an area of increased sensitivity to light is formed in the lower part of the eye, but when switching to feeding on benthos, sensitivity increases in the upper part of the eye, which perceives objects located below.
The intensity of light perceived by the fish's organ of vision appears to be different in different species. The American
Horizon\ Tserek Stones\ to
* Window Y
.Coastline/ "M"
Rice. 19. Visual field of a fish looking up through a calm water surface. Above is the surface of the water and the air space visible from below. Below is the same diagram from the side. Rays falling from above onto the surface of the water are refracted inside the “window” and enter the eye of the fish. Inside the angle of 97.6°, the fish sees the surface space; outside this angle, it sees the image of objects located at the bottom, reflected from the surface of the water (from Baburina, 1955)
Lepomis fish from the family Centrarchidae still detect light with an intensity of 10~5 lux. A similar intensity of illumination is observed in the most transparent water of the Sargasso Sea at a depth of 430 m from the surface. Lepomis is a freshwater fish, inhabitant of relatively shallow water bodies. Therefore, it is very likely that deep-sea fish, especially those with telescopic... Chinese organs of vision are able to respond to significantly weaker lighting (Fig. 20).
Deep-sea fish develop a number of adaptations due to low light levels at depths. Many deep-sea fish have eyes that reach enormous sizes. For example, in Bathymacrops macrolepis Gelchrist from the family Microstomidae, the diameter of the eye is about 40% of the length of the head. In Polyipnus from the family Sternoptychidae, the eye diameter is 25-32% of the length of the head, and in Myctophium rissoi (Sosso) from the family
Rice. 20. Visual organs of some deep-sea fish, Left - Argyropelecus affinis Garm.; right - Myctophium rissoi (Sosso) (from Fowler, 1936)
family Myctophidae - even up to 50%. Very often, in deep-sea fish, the shape of the pupil also changes - it becomes oblong, and its ends extend beyond the lens, due to which, as well as by a general increase in the size of the eye, its light-absorbing ability increases. Argyropelecus from the family Sternoptychidae has a special light in the eye
Rice. 21. Larva of deep-sea fish I diacanthus (order Stomiatoidei) (from Fowler, 1936)
a continuous organ that maintains the retina in a state of constant irritation and thereby increases its sensitivity to light rays entering from the outside. Many deep-sea fish have telescopic eyes, which increases their sensitivity and expands their field of vision. The most interesting changes in the organ of vision occur in the larva of the deep-sea fish Idiacanthus (Fig. 21). Her eyes are located on long stalks, which allows her to greatly increase her field of vision. In adult fish, the eyestalk is lost.
Along with the strong development of the organ of vision in some deep-sea fish, in others, as already noted, the organ of vision either significantly decreases (Benthosaurus and others) or disappears completely (Ipnops). Along with the reduction of the organ of vision, these fish usually develop various outgrowths on the body: the rays of paired and unpaired fins or antennae are greatly lengthened. All these outgrowths serve as organs of touch and to a certain extent compensate for the reduction of the organs of vision.
The development of visual organs in deep-sea fish living at depths where daylight does not penetrate is due to the fact that many animals of the deep have the ability to glow.
49
Glow in animals that live in the deep sea is a very common phenomenon. About 45% of fish inhabiting depths greater than 300 m have luminescent organs. In their simplest form, luminescent organs are present in deep-sea fish from the family Macruridae. Their skin mucous glands contain a phosphorescent substance that emits a weak light, creating
4 G. V. Nikolsky
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
Rice. 22. Luminous organ of Argyropelecus.
¦ a - reflector; b - luminous cells; c - lens; g - underlying layer (from Braieg, 1906-1908)
The functioning of organs in different species of fish is very different, so that in many cases it can serve as a systematic sign (Fig. 23).
Usually the glow occurs as a result of contact
Rice. 23. Diagram of the arrangement of luminous organs in the schooling deep-sea fish Lampanyctes (from Andriyashev, 1939)
the secret of luminous cells with water, but in the fish of Asgoroth. japonicum Giinth. reduction is caused by microorganisms located in the gland. "The intensity of the glow depends on a number of factors and varies even in the same fish. Many fish glow especially intensely during the breeding season.
What is the biological significance of the glow of deep-sea fish,
has not yet been fully elucidated, but there is no doubt that the role of luminous organs is different for different fish: In Ceratiidae, the luminous organ located at the end of the first ray of the dorsal fin apparently serves to lure prey. Perhaps the luminous organ at the end of the tail of Saccopharynx performs the same function. The luminous organs of Argyropelecus, Lampanyctes, Myctophium, Vinciguerria and many other fish located on the sides of the body allow them to find individuals of the same species in the dark at great depths. Apparently, this is especially important for fish that live in schools.
In complete darkness, not disturbed even by luminous organisms, cave fish live. Based on how closely animals are related to life in caves, they are usually divided into the following groups: 1) troglobionts - permanent inhabitants of caves; 2) troglophiles - predominantly inhabitants of caves, but are also found in other places,
- trogloxenes are widespread forms that also enter caves.
As compensation for the degenerating organ of vision in cave fish, they usually have very strongly developed lateral line organs, especially on the head, and organs of touch, such as the long whiskers of the Brazilian cave catfish from the family Pimelodidae.
The fish that inhabit the caves are very diverse. Currently, representatives of a number of groups of the order Cypriniformes (Aulopyge, Paraphoxinus, Chondrostoma, American catfish, etc.), Cyprinodontiformes (Chologaster, Troglichthys, Amblyopsis), a number of species of gobies, etc. are known in caves.
Lighting conditions in water differ from those in air not only in intensity, but also in the degree of penetration of individual rays of the spectrum into the depths of water. As is known, the coefficient of absorption of rays with different wavelengths by water is far from the same. Red rays are absorbed most strongly by water. When passing through a 1 m layer of water, 25% red is absorbed*
rays and only 3% violet. However, even violet rays at a depth of over 100 m become almost indistinguishable. Consequently, at depths, fish have little ability to distinguish colors.
The visible spectrum that fish perceive is somewhat different from the spectrum perceived by terrestrial vertebrates. Different fish have differences related to the nature of their habitat. Species of fish living in the coastal zone and in
Rice. 24. Cave fish (from top to bottom) - Chologaster, Typhlichthys: Amblyopsis (Cvprinodontiformes) (from Jordan, 1925)
surface layers of water have a wider visible spectrum than fish living at great depths. The sculpin sculpin - Myoxocephalus scorpius (L.) - inhabits shallow depths, perceives colors with a wavelength from 485 to 720 mmk, and the star ray, which lives at great depths - Raja radiata Donov. - from 460 to 620 mmk, haddock Melanogrammus aeglefinus L. - from 480 to 620 mmk (Protasov and Golubtsov, 1960). It should be noted that the reduction in visibility occurs primarily due to the long-wave part of the spectrum (Protasov, 1961).
The fact that most fish species distinguish colors is proven by a number of observations. Apparently, only some cartilaginous fish (Chondrichthyes) and cartilaginous ganoids (Chondrostei) do not distinguish colors. Other fish distinguish colors well, which has been proven, in particular, by many experiments using the conditioned reflex technique. For example, it was possible to train the gudgeon - Gobio gobio (L.) - to take food from a cup of a certain color.
It is known that fish can change color and skin pattern depending on the color of the soil on which they are located. Moreover, if a fish, accustomed to black soil and changing color accordingly, was given a choice of a number of soils of different colors, then the fish usually chose the soil to which it was accustomed and the color of which corresponded to the color of its skin.
Particularly dramatic changes in body color on various substrates are observed in flounders.
In this case, not only the tone changes, but also the pattern, depending on the nature of the soil on which the fish is located. What is the mechanism of this phenomenon has not yet been precisely clarified. It is only known that a change in color occurs as a result of corresponding irritation of the eye. Sumner (1933), by placing transparent colored caps over the eyes of fish, caused them to change color to match the color of the caps. A flounder, whose body is on the ground of one color, and the head on the ground of a different color, changes the color of the body according to the background on which the head is located (Fig. 25). "
Naturally, the color of a fish’s body is closely related to lighting conditions.
It is usually customary to distinguish the following main types of fish coloration, which are an adaptation to certain habitat conditions.
Pelagic coloring: bluish or greenish back and silvery sides and belly. This type of coloring is characteristic of fish living in the water column (herring, anchovies, bleak, etc.). The bluish back makes the fish hardly noticeable from above, and the silvery sides and belly are poorly visible from below against the background of the mirror surface.
Overgrown color - brownish, greenish or yellowish back and usually transverse stripes or streaks on the sides. This coloring is characteristic of fish from thickets or coral reefs. Sometimes these fish, especially in the tropical zone, can be quite brightly colored.
Examples of fish with thicket coloration include: common perch and pike - from freshwater forms; scorpionfish, many wrasses and coral fish are from the sea.
The bottom color is a dark back and sides, sometimes with darker streaks and a light belly (in flounders the side facing the ground is light). In bottom fish living above the pebbly soil of rivers with clear water, usually there are black spots on the sides of the body, sometimes slightly elongated in the dorsal direction, sometimes located in the form of a longitudinal stripe (the so-called channel coloration). This coloration is characteristic, for example, of juvenile salmon during the river life period, juvenile grayling, common minnow and other fish. This coloring makes the fish less noticeable against the background of pebbly soil in clear flowing water. In bottom fish of stagnant waters, there are usually no bright dark spots on the sides of the body, or they have blurred outlines.
The schooling coloration of fish is especially noticeable. This coloring makes it easier for individuals in a flock to orient themselves towards each other (see below, p. 98). It appears as either one or more spots on the sides of the body or on the dorsal fin, or as a dark stripe along the body. An example is the color of the Amur minnow - Phoxinus lagovskii Dyb., juveniles of the spiny bitterling - Acanthorhodeus asmussi Dyb., some herring, haddock, etc. (Fig. 26).
The coloring of deep-sea fish is very specific. Usually these fish are colored either dark, sometimes almost black or red. This is explained by the fact that even at relatively shallow depths, the red color under water appears black and is poorly visible to predators.
A slightly different color pattern is observed in deep-sea fish that have luminescent organs on their bodies. These fish have a lot of guanine in their skin, which gives the body a silvery sheen (Argyropelecus, etc.).
As is well known, the color of fish does not remain unchanged during individual development. It changes when the fish moves, in the process of development, from one habitat to another. So, for example, the color of juvenile salmon in the river has a channel-type character; when they migrate to the sea, it is replaced by a pelagic coloration, and when the fish return back to the river to reproduce, it again acquires a channel-type character. Color may change during the day; Thus, some representatives of Characinoidei, (Nannostomus) have a gregarious color during the day - a black stripe along the body, and at night transverse striping appears, i.e. the color becomes thicket.
Rice. 26, Types of schooling colors in fish (from top to bottom): Amur minnow - Phoxinus lagowsku Dyb.; spiny mustard (juvenile) - Acanthorhodeus asmussi Dyb.; haddock - Melanogrammus aeglefinus (L.) /
The so-called nuptial coloration in fish is often
protective device. Nuptial coloration is absent in fish that spawn at depths, and is usually poorly expressed in fish that spawn at night.
Different species of fish react to light differently. Some are attracted to light: sprat Clupeonella delicatula (Norm.), saury Cololabis saifa (Brev.), etc. Some fish, such as carp, avoid light. Fish are usually attracted to the light; they feed by orienting themselves using the organ of vision (mainly the so-called “visual planktivores”). The reaction to light also changes in fish in different biological states. Thus, female anchovy sprat with flowing eggs are not attracted to the light, but those that have spawned or are in a pre-spawning state go to the light (Shubnikov, 1959). The nature of the reaction to light in many fish also changes during the process of individual development. Juvenile salmon, minnows and some other fish hide from the light under stones, which ensures their safety from enemies. In sandworts - lamprey larvae (cyclostomes) whose tail carries light-sensitive cells - this feature is associated with life in the ground. Sandworms react to the illumination of the tail area with swimming movements, burrowing deeper into the ground.
. What are the reasons for fish reaction to light? There are several hypotheses on this issue (for a review, see Protasov, 1961). J. Loeb (1910) considers the attraction of fish to light as a forced, non-adaptive movement - as phototaxis. Most researchers view fish's response to light as an adaptation. Franz (cited by Protasov) believes that light has a signaling value, in many cases serving as a signal of danger. S.G. Zusser (1953) believes that the reaction of fish to light is a food reflex.
There is no doubt that in all cases the fish reacts to light adaptively. In some cases, this may be a defensive reaction when the fish avoids the light, in other cases the approach to the light is associated with the extraction of food. Currently, the positive or negative reaction of fish to light is used in fishing (Borisov, 1955). Fish, attracted by the light to form aggregations around the light source, are then caught either with nets or pumped onto the deck. Fish that react negatively to light, such as carp, are driven out of places that are inconvenient for fishing, for example, from snagged areas of a pond, using light.
The importance of light in the life of fish is not limited to its connection with vision. Illumination is also of great importance for the development of fish. In many species, the normal course of metabolism is disrupted if they are forced to develop in light conditions that are not typical for them (those adapted to development in the light are placed in the dark, and vice versa). This is clearly shown by N.N. Disler (1953) using the example of the development of chum salmon in the light (see below, p. 193).
Light also affects the maturation of fish reproductive products. Experiments on the American palia S*alvelinus foritinalis (Mitchill) showed that in experimental fish exposed to enhanced lighting, maturation occurs earlier than in control fish exposed to normal light. However, in fish in high-altitude conditions, apparently, just like in some mammals in conditions of artificial lighting, light, after stimulating the enhanced development of the gonads, can cause a sharp drop in their activity. In this regard, ancient high-mountain forms developed intense coloration of the peritoneum, protecting the gonads from excessive exposure to light.
The dynamics of light intensity throughout the year largely determines the course of the sexual cycle in fish. The fact that in tropical fish reproduction occurs throughout the year, and in fish from temperate latitudes only at certain times, is largely due to the intensity of insolation.
A peculiar protective device from light is observed in the larvae of many pelagic fish. Thus, in the larvae of herring of the genera Sprattus and Sardina, a black pigment develops above the neural tube, protecting the nervous system and underlying organs from excessive exposure to light. With the resorption of the yolk sac, the pigment above the neural tube in fry disappears. It is interesting that related species that have bottom eggs and larvae that stay in the bottom layers do not have such a pigment.
The sun's rays have a very significant effect on the course of metabolism in fish. Experiments carried out on mosquitofish (Gambusia affitiis Baird, et Gir.). showed that in mosquito fish deprived of light, vitamin deficiency develops quite quickly, causing, first of all, a loss of ability to reproduce.
Sound and other vibrations
As is known, the speed of sound propagation in water is greater than in air. Otherwise, sound absorption in water occurs.
Fish perceive both mechanical and infrasonic, sound and, apparently, ultrasonic vibrations. Fish perceive water currents, mechanical and infrasonic vibrations with a frequency of 5 to 25 hertz [I] by the lateral line organs, and vibrations from 16 to 13,000 hertz by the auditory labyrinth, more precisely its lower part - Sacculus and Lagena (the upper part serves as an organ of balance). In some species of fish, vibrations with a wavelength of 18 to 30 hertz, i.e. located on the border of infrasound and sound waves, are perceived as organs of the lateral line. and the labyrinth. Differences in the nature of vibration perception in different fish species are shown in Table 1.
The swim bladder also plays a significant role in the perception of sound, apparently acting as a resonator. Since sounds travel faster and further in water, their perception in water turns out to be easier. Sounds do not penetrate well from air1 into water. From water to air - several1
Table 1
The nature of sound vibrations perceived by different fish
| | Frequency in hertz |
|
| Types of fish | | |
| | from | TO |
| 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 |
better, since the sound pressure in water is much stronger than in air.
Fish can not only hear, many species of fish can make sounds themselves. The organs through which fish make sounds are different. In many fish, such an organ is the swim bladder, which is sometimes equipped with special muscles. With the help of the swim bladder, croakers (Sciaenidae), wrasses (Labridae), etc. make sounds. In catfish (Siluroidei), the organs that produce sound are the rays of the pectoral fins in combination with the bones of the shoulder girdle. In some fish, sounds are made using the pharyngeal and jaw teeth (Tetrodontidae).
The nature of the sounds made by fish is very different: they resemble drum beats, croaking, grunting, whistling, and grumbling. The sounds made by fish are usually divided into “biological”, i.e., specially made by fish and having adaptive significance, and “mechanical”, made by fish when moving, feeding, digging up soil, etc. The latter usually do not have adaptive significance and On the contrary, they often unmask the situation (Malyukina and Protasov, I960).
Among tropical fish there are more species that produce “biological” sounds than among fish inhabiting water bodies at high latitudes. The adaptive significance of the sounds made by fish varies. Often sounds are made by fish especially
intensively during reproduction and serve, apparently, to attract one sex to the other. This has been noted in croakers, catfish and a number of other fish. These sounds can be so strong that fishermen use them to find concentrations of spawning fish. Sometimes you don't even need to immerse your head in water to detect these sounds.
In some croakers, sound is also important when fish come into contact in a feeding school. Thus, in the Beaufort area (Atlantic coast of the USA), the most intense sound of croakers falls in the dark from 21:00 to 02:00 and occurs during the period of the most intense feeding (Fish, 1954).
In some cases, the sound has a terrifying meaning. Nest-building killer whale catfish (Bagridae) apparently scare away enemies with the creaking sounds they make using their fins. The fish Opsanus tau, (L.) from the family Batrachoididae also makes special sounds when it guards its eggs.
The same type of fish can make different sounds, differing not only in strength, but also in frequency. Thus, Caranx crysos (Mitchrll) makes two types of sounds - croaking and rattling. These sounds differ in wavelength." The sounds produced by males and females are also different in Strength and frequency. This has been noted, for example, for sea bass - Morone saxatilis Walb. from Serranidae, in which males produce stronger sounds and with greater frequency amplitude (Fish, 1954). Young fish also differ from old ones in the nature of the sounds they make. The difference in the nature of sounds produced by males and females of the same species is often associated with corresponding differences in the structure of the sound-producing apparatus. Thus, in male haddock - Melanogrammus aeglefinus (L.) - the “drum muscles” of the swim bladder are much more developed than in females. Particularly significant development of this muscle is achieved during spawning (Tempelman and Hoder, 1958).
Some fish react very strongly to sounds. At the same time, some sounds of fish scare away, while others attract. At the sound of the engine or the blow of an oar on the side of the boat, salmon standing in holes in rivers during the pre-spawning period often jumps out of the water. The noise is caused by the Amur silver carp - Hypophthalmichthys molitrix (Val.) jumping out of the water. The use of sound when fishing is based on the reaction of fish to Sound. So, when fishing for mullet with “matting”, the fish, frightened by the sound, jumps out. water and falls on special mats laid out on the surface, usually in the form of a semicircle, with the edges raised up.. Once on such a “matting”, the fish cannot jump back into the water. When catching pelagic fish with a purse seine, sometimes a special bell is lowered into the gate of the seine, including
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 accumulations. 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
IN natural waters there are weak natural electric 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 water bodies 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. Thus, the American catfish - Amiurus nebulosus Le Sueur - reacts to current more strongly than the goldfish - 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 to 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 have 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 the 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. Moreover, 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
L
th
II"*J
O
zo zi
1-5" 5-Y 10-15" 15-20" 20-26"
Temperature
5§.
I
S"S-
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.
Rice. 28., Change in oxygen concentration lethal for carp with temperature change (from Ivlev, 1938)
The digestibility of feed also changes with temperature changes. Thus, in roach at 16°C the digestibility of dry matter is 73.9%, and at 22°C -
81.8%. It is interesting that at the same time, the digestibility of nitrogen compounds in roach within these temperatures remains almost unchanged (Karzinkin, J952); in carp, i.e., in fish that are more carnivorous than roach, the digestibility of feed increases with increasing temperature, both overall and in relation to nitrogen compounds.
Naturally, the temperature change is very
The gas exchange of fish also changes greatly. At the same time, the minimum concentration of oxygen at which fish can live often changes. So for carp, at a temperature of 1° C the minimum oxygen concentration is 0.8 mg/l, and at 30° C it is already 1.3 mg/l (Fig. 28). Naturally, the quantity
65
5th century NIKOLSKY
the food consumed by fish at different temperatures is also associated with the state of the fish itself." G lt; "1.
A change in temperature, affecting: a change in the metabolic rate of fish, is also associated with a change in the toxic effects of various substances on its body. Thus, at 1°C the lethal concentration of CO2 for carp is 120 mg/l, and at 30°C this amount drops to 55-60 mg/l (Fig. 29).
504*
Rice. 29. Change in carbon dioxide concentration lethal for carp due to temperature change (from Ivlev, 1938)
With a significant decrease in temperature, fish can fall into a state close to suspended animation; I can remain for a more or less long time in a supercooled state, even freezing into the ice, such as crucian carp and black fish. ¦
Kai - experiments have shown that when the body of a fish freezes into ice, its internal juices remain unfrozen and have a temperature of about - 0.2, - 0.3 ° C. Further cooling, provided that the fish is frozen in water, leads to a gradual decrease in temperature fish body, freezing of abdominal fluids and death. If fish freezes out of water, then its freezing is usually associated with preliminary hypothermia and a drop in body temperature for a short time, even to -4.8°, after which freezing of body fluids occurs and a slight increase in temperature as a result of the release of latent heat of Freezing. If the internal organs and gills freeze, then the death of the fish is inevitable.
The adaptation of fish to life at certain, often very narrow, temperature amplitudes is associated with the development in them of a rather subtle reaction to the temperature gradient.
. Minimum temperature gradient by which? fish react
; "Ch. (after Bull, 1936). :
Pholis gunnelus (L.) "J . . . . . . 0.03°
Zoarces viviparus (L.) . .. . . . , / .... . , 0.03°
Myoxocepfiqlus scorpius (L.) , . . . . . . . . . . . 0.05°
Gadus morhua L. . . . :. . . . i¦. . . ..gt; . . . 0.05°
Odontogadus merlangus (L.) . ... . .4. . . ...0.03"
Pollachius virens (L.) 0.06°
Pleuronectes flesus L. . . . 0.05°
Pteuroriectes platessa (L.) . Y , . . . . . . . . . . . 0.06°
Spinachia spinachia (L!) 0.05°
Nerophis lumbriciformes Penn. , . . . . . . . . . , 0.07°
Since fish are adapted to life at a certain
Three-day temperature in
Rice. ZO. Distribution:
1 - Ulcina olriki (Lutken) (Agonidae); 2 - Eumesogrammus praecisus (Kroyer) (Stichaeidae) in connection with the distribution of bottom temperatures (from Andriyashev, 1939)
temperature, naturally, its distribution in a reservoir is usually related to the temperature distribution. Both seasonal and long-term temperature changes are associated with changes in the distribution of fish.
"The affinity of individual fish species to certain temperatures can be clearly judged from the given curve of the frequency of occurrence of individual fish species in connection with the temperature distribution (Fig. 30). As an example, we took representatives of the family -
Agonidae - Ulcina olriki (Lfltken) and Stichaeidae -
Eumesogrammus praecisus (Kroyer). As can be seen from Fig. 30, both of these species are confined in their distribution to very specific different temperatures: Ulcina is found at its maximum at a temperature of -1.0-1.5° C, a* Eumesogrammus - at +1, = 2° C.
, Knowing the affinity of fish to a certain temperature, when searching for their commercial concentrations, it is often possible to navigate by the temperature distribution in the reservoir, f Long-term changes in water temperature (as, for example, in the North Atlantic due to the dynamics Atlantic current) strongly influence the distribution of fish (Helland-Hansen and Nansen, 1909). During the years of warming in the White Sea, there were cases of catching such relatively warm-water fish as mackerel - Scomber scombrus L., and in Kanin's nose - garfish * - Belone belone (L .). Cod penetrates into the Kara Sea during periods of drying, and its commercial concentrations appear even off the coast of Greenland. .
On the contrary, during periods of cold weather, Arctic species descend to lower latitudes. For example, the Arctic cod - Boreogadus saida (Lepechin) - enters the White Sea in large numbers.
Sudden changes in water temperature sometimes cause mass fish deaths. An example of this kind is the case of the chameleon-headed lopholatilas chamaeleonticeps Goode et Bean (Fig. 31). Until 1879, this species was not known off the southern coast of New England.
In subsequent years, due to warming, it appeared
Rice. 31. Lopholatilus hamaeleonticeps Goode et Bean (chameleon-headed)
here in large quantities and has become an object of fishing. As a result of a sharp cold snap that occurred in March 1882, many individuals of this species died. They covered the surface of the sea with their corpses for many miles. After this incident, chameleon-heads completely disappeared from the indicated area for a long time and only in recent years have reappeared in fairly significant numbers. .
The death of cold-water fish - trout, white fish - can be caused by an increase in temperature, but usually the temperature affects death not directly, but through a change in the oxygen regime, disrupting breathing conditions.
Changes in the distribution of fish due to changes in temperature also occurred in previous geological eras. It has been established, for example, that in the reservoirs located on the site of the modern Irtysh basin, in the Miocene there were fish that were much warmer water than those that inhabit the Ob basin now. Thus, the Neogene Irtysh fauna included representatives of the genera Chondrostoma, Alburnoides, Blicca, which are now not found in the Arctic Ocean basin in Siberia, but are distributed mainly in the Ponto-Aral-Kayopian province and, apparently, were. forced out of the Arctic Ocean basin as a result of climate change towards cooling (V. Lebedev, 1959). “. %
And at a later time we find examples of changes in the distribution area and number of species under the influence
changes in ambient temperature. Thus, the cooling caused by the onset of glaciers at the end of the Tertiary and the beginning of the Quaternary periods led to the fact that representatives of the salmon family, confined to cold waters, were able to significantly move south all the way to the Mediterranean basin, including the rivers of Asia Minor and North Africa. At this time, salmon were much more abundant in the Black Sea, as evidenced by the large number of bones of this fish in the food remains of Paleolithic man.
In post-glacial times, climate fluctuations also led to changes in the composition of the ichthyofauna. For example, during the climatic optimum about 5,000 years ago, when the climate was somewhat warmer, the fish fauna of the White Sea basin contained up to 40% of warmer-water species such as asp - Aspius aspius (L.), rudd - Scardinius eryth- rophthalmus (L.) and blue bream - Abramis ballerus (L.) Now these species are not found in the White Sea basin; they were undoubtedly driven out from here by the cooling that occurred even before the beginning of our era (Nikolsky, 1943).
Thus, the relationship between the distribution of individual species and temperature is very strong. The attachment of representatives of each faunal complex to certain thermal conditions determines the frequent coincidence of the boundaries between individual zoogeographic regions in the sea and certain isotherms. For example, the Chukotka temperate Arctic province is characterized by very low temperatures and, accordingly, the predominance of Arctic fauna. Most boreal elements penetrate only into the eastern part of the Chukchi Sea along with warm currents. The fauna of the White Sea, designated as a special zoogeographical area, is significantly colder in composition than the fauna of the southern part of the Barents Sea located to the north.
The nature of distribution, migration, spawning and feeding grounds of the same species in different parts of its distribution area may be different due to the distribution of temperature and other environmental factors. For example, in the Pacific cod Gadus morhua macrocephalus Til. - off the coast of the Korean Peninsula, breeding sites are located in the coastal zone, and in the Bering Sea at depths; feeding areas are the opposite (Fig. 32).
Adaptive changes that occur in fish during temperature changes are also associated with some morphological restructuring. For example, in many fish, an adaptive response to changes in temperature, and thereby water density, is a change in the number of vertebrae in the caudal region (with closed hemal arches), i.e., a change in hydrodynamic properties due to adaptation to movement in other waters. density.
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
№
Depth 6 m Bering hole
Western
Kamchatka
Tatar Strait ~1
Southern part 3“ Japanese muzzle,
b"°
Dgust 100 200
Southern part of the Sea of Japan
Rice. 32. Distribution of Pacific cod Gadus morhua macro-cephalus Til. in different parts of its distribution area in connection with temperature distribution; oblique shading - breeding sites (from Moiseev, 1960)
Sh
Depth 6 m
BeringoVo
sea
Western
Kamchatka
Tatar
spill
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 effects: There are known cases when, in the coastal strip, fish and eggs that were kept near the shore were crushed by ice washed ashore. Ice also plays a certain 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 ‘
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