What do fish breathe? What breathing devices do they have? How do fish breathe underwater? How do fish use their mouths to breathe?

All living things, including fish, need oxygen. This gas is absorbed by the body during respiration. The habitat of fish - water - contains real oxygen, and not the air we are used to. Oxygen, entering the body through the gills or additional respiratory organs, penetrates the blood, which distributes it throughout the fish’s body and supports its vital functions. The same process in humans involves lungs instead of gills.

In water, fish respiration occurs mainly through gills. Oxygenated water passes through the mouth directly into the pharynx. The gills of a fish consist of an operculum and a soft skin layer. During the so-called inhalation, the gill cover opens, and the skin detachment, on the contrary, is pressed against the body. Due to this, the gill cavity increases, and the pressure inside it decreases, and water is drawn in from the pharynx. During exhalation, the gill cover closes and is pressed tightly against the body, preventing water from returning back into the pharynx. At the same time, the gill cavity is greatly reduced, and the pressure in it increases, and water seeps through the skin detachment and goes back into the habitat of this fish.

This method of breathing allows you to absorb oxygen to a greater extent. In fish, oxygen absorption is almost thirty percent. For example, in mammals it makes up less than a quarter of all inhaled oxygen. If the reservoir is heavily polluted, then many fish float to the surface for air, but, unfortunately, it is impossible to absorb oxygen from the air with the help of gills. Therefore, by polluting water bodies, we destroy many species of fish. But there is one unusual Far Eastern fish, its name is climbing perch. Its moving scales, clinging to the ground, facilitate the fish to come ashore. She can breathe air for a while because her gills have been able to adapt to absorb oxygen from the air.

But some individual species of fish, in addition to gills, have additional organs for breathing. For example, they can absorb oxygen through their skin. These include carp, crucian carp, eels and others. When there is not enough oxygen in the water, they use their skin to breathe. If you put such a fish in wet grass, it can live there for more than half a day.

Those who have an aquarium at home have probably noticed that fish often swim to the surface of the water and slightly stick their heads out. Many varieties of aquarium fish have a special organ called the gill labyrinth. With its help, fish can absorb oxygen directly from the air. In cases where the fish does not have the opportunity to rise to the surface of the water at least once in a few hours, it may die.

You might be surprised, but there is one fish that uses its intestines to breathe. This is an American catfish. Swallowing air, they send it to the intestines, the walls of which have many blood vessels. It is here that the blood is enriched with additional oxygen.

There are also lungfishes. They have the semblance of real lungs, which were able to form from an ordinary swim bladder.

This is exactly how fish breathe!

Primitive gills are found in. In most higher animals, these are located on the lateral walls of the body and the upper parts of the thoracic legs. Aquatic insect larvae have tracheal gills, which are thin-walled outgrowths on different parts of the body in which there is a network of tracheae.

Of the echinoderms, starfish and sea urchins have gills. All proto-aquatic chordates (fish) have rows of paired openings (gill slits) located in the pharynx. In enterophores (mobile bottom-dwelling animals), tunicates (small marine animals with a sac-like body covered with a membrane) and anuranids (a special group of invertebrate animals), gas exchange occurs during the passage of water through the gill slits.

How animals breathe with gills

The gills consist of leaflets (threads), inside them there is a network of blood vessels. The blood in them is separated from the external environment by a very thin skin, and the necessary conditions are created for the exchange between gases dissolved in water and the blood. The gill slits in fish are divided by arches, from which branchial septa extend. In some bony and cartilaginous species, the petals of the gills are located on the outer side of the arches in two rows. Actively swimming fish have gills with a much larger surface area than sedentary aquatic animals.

In many invertebrates and young tadpoles, these respiratory organs are located on the outside of the body. In fish and higher crustaceans they are hidden under protective devices. Often the gills are located in special body cavities; they can be covered with special folds of skin or leathery covers (gill operculum) to protect them from damage.

The gills also function as a circulatory system.

The movement of the gill cover during breathing occurs simultaneously with the movement (opening and closing) of the mouth. When breathing, the fish opens its mouth, draws water in, and closes its mouth. Water affects the respiratory organs, passes through them and comes out. Oxygen is absorbed by the capillaries of the blood vessels located in the gills, and the used carbon dioxide is released through them into the water.

• Read: Fish breathe through their intestines!

Animals can live for a very long time without food, but only a few minutes without oxygen.

But what about the fish? After all, it is difficult, seemingly impossible, to breathe in water. It contains twenty times less oxygen than air. But it turns out that this is not so significant. Oxygen also does not enter the lungs of terrestrial animals directly from the atmosphere. First, it dissolves in the fluid that washes the walls of the lungs, and only then enters the blood. It turns out that land animals also breathe oxygen dissolved in water.

But why, then, cannot they live in water like fish? Yes, because as soon as their lungs are filled with water, the oxygen dissolved in it is instantly absorbed, but no new one comes in - and the animal suffocates. Now, if the water in the lungs were continuously replaced with fresh water, then, say, a dog or horse could breathe in water no worse than in air.

In order to breathe normally in water, you need gills. The gills consist of gill arches with many lobes. Waste blood flows to the gill arches; here it releases carbon dioxide into the water and is enriched with oxygen.

For normal breathing, fresh water must also flow to the gills all the time. When a fish swims, water enters the mouth, washes over the gills, and exits through the gill slits. When a fish stands, it constantly opens and closes its mouth, raises and lowers its gill covers, sucking in fresh water and pushing out old water.

The gills, which have a huge surface, help to better use the oxygen contained in the water. For example, a perch has a gill surface that is almost 30 times larger than the surface of its body.

The shape and size of the surface of the gills, as well as the structure of the gill slits, depend on the lifestyle of the fish. Pelagic fish, that is, fish that live in the water column, have a large mouth and wide gill slits, this facilitates better penetration of fresh water into the gills.

Fish that live on the bottom have small gill slits, otherwise the gills would become clogged with sand and silt. With this structure of the slits, the water in the gills is poorly renewed, so bottom-dwelling fish have devices for forced water exchange.

For example, when an eel inhales, it inflates its cheeks and sucks in water through its mouth; when it exhales, it closes its mouth and, squeezing its cheeks, pushes water out through the gill slits. Flounders have a special gill membrane that pushes water out like a piston. Stingrays breathe even more uniquely. They have a hole at the top of their head equipped with a valve. When you “inhale,” the valve opens and water freely passes through the hole, flowing to the gills; When you exhale, the valve closes and water exits through the gill slits.

The small Asian fish Gyrinochelus has the habit of attaching its mouth to bottom objects. And so that the flow of water to the gills does not stop, this fish has two pairs of gill openings. When the mouth is closed, water enters through the upper holes and exits through the lower ones.

However, no matter how amazingly the gills are adapted to environmental conditions, they do not always provide the fish with normal breathing. Some bodies of water are constantly lacking oxygen, while in others its content drops sharply at certain times of the year. In summer, oxygen starvation occurs during drought, when stagnant bodies of water begin to dry up, and at night, when aquatic plants intensively absorb oxygen. In winter, the access of oxygen from the atmosphere to water is sharply reduced, as reservoirs are covered with a thick layer of ice and snow.

Fish react differently to the amount of dissolved oxygen in the water. Some need a very high content of it (salmon, whitefish, trout, pike perch), others are less demanding (roach, perch, pike), while others are satisfied with a completely insignificant amount (crucian carp, tench). For each type of fish, there is a certain threshold of oxygen content in the water, below which they become lethargic, hardly move, feed poorly and ultimately die.

Some fish do not tolerate even the slightest “oxygen starvation” and inhabit reservoirs only with clear, cold, oxygen-rich water. Others even live in swamps.

Probably, many have noticed that when there is a lack of oxygen in the aquarium, fish rise to the surface and begin to capture atmospheric air.

But fish cannot breathe atmospheric air like this for a long time, so some of them have adapted to breathe with other organs.

Carp, crucian carp, and tench often live in ponds with musty water; They lack only gills, and they also breathe through the surface of their skin. Crucian carp and eel in a basket with damp grass, in cold weather, can live more than twelve hours.

The mudskipper goes even longer without water. Hunting for insects, he spends many hours on land. The captured jumpers were kept for six days on wet sand, and they felt quite normal. Jumpers breathe, in addition to gills, through the skin and oral cavity. In addition, their gill covers are pressed tightly against the body, and the gills remain moist for a long time. Some naturalists believe that jumpers can breathe with their tails. It is not for nothing that this fish often lies on the coastal sand, dipping its tail into the water.

V. Sabunaev, "Entertaining ichthyology"

Like all living creatures, fish need oxygen. Most fish receive it using special sieve-like organs called gills.

The gills are located just behind the oral cavity on either side of the head and are usually protected by a translucent plate called the operculum, or operculum. Below the operculum are four rows of partially overlapping blood-red gills. The gills are composed of bony arches that support numerous gill filaments - pairs of thin, soft processes that resemble the tightly set teeth of a comb. Each petal contains tiny membranes, or lamellae, made up of billions of blood capillaries. The walls of the membranes are so thin that the blood flowing through them extracts oxygen directly from the water flow washing the gills. The lamellae then remove carbon dioxide from the blood into the water. Water, like air, is 1/30 oxygen, and this gas exchange - oxygen and carbon dioxide - is a key component of underwater life.

Hard gill rakers located on the gill arch, filter the incoming water. Blood vessels in the gill filaments supply blood and drain the capillaries in the lamella.

Water passing over gill filaments, enriches arterial blood with oxygen. After this, the blood flows through the venous vessels into the membrane, where it is freed from carbon dioxide.

Water entering the gills

The normal functioning of fish is ensured by the continuous flow of oxygenated water into the gills. In most bony fishes, the mouth and gills work in interaction according to the pump principle: first, the gills close tightly, the mouth opens, and its walls expand, drawing water inside. The oral cavity then contracts, the mouth closes, and the gills open, pushing water out of the mouth. This method of breathing, which allows water to penetrate the gills even if the fish is at rest, is characteristic of sedentary fish such as carp, flounder and halibut.

Breathing begins, when the fish's mouth opens and the oral cavity expands, sucking in water.

Then the fish's mouth closes and the operculum opens, pushing water out of the gill cavity through the gills.

It's better to breathe through your mouth

Active fish - mackerel, tuna and some types of sharks - need more oxygen than their slow-moving counterparts, such as flounder, eel, electric ray and seahorses. This is why underwater fish often swim with their mouths open: this allows them to pass a significantly larger volume of water, and therefore oxygen, through their gills. In addition, the gills of these fish species are larger and thicker, with closely spaced membranes, which significantly increases their respiratory capacity. These fish are forced to swim even while sleeping, otherwise they will die from lack of oxygen (from suffocation).

Breath of fish. Fish breathe oxygen dissolved in water. The respiratory organs of fish are gills, consisting of many petals with blood vessels. The number of gill filaments varies for each fish species. For example, in perch it is 30 times greater than in others.

Observing the behavior of fish in water, you can notice that the fish opens and closes its mouth, the same thing happens with the gills, if the gills open, the fish’s mouth closes, and vice versa.

Thus, when a fish swallows water, it closes its mouth, the water passes into the gill cavity and flows out through the gill slit. It is the blood vessels of the gill filaments that serve the fish to enrich the blood with oxygen.

Each type of fish has its own “minimum” oxygen content in water. If this threshold is lower than it should be, the fish become lethargic, inactive and die altogether (these are so-called kills).

Ways to increase your catch!

Having 13 years of fishing experience, I have learned many ways to return home with a rich catch. Here are the most effective:

1. Bite activator. This additive with pheromones causes a wild appetite even in well-fed and passive fish, attracting them to the fishing spot from long distances. The Fish Hungry bite activator has proven itself to be excellent -
2. Gear with increased sensitivity. You should first familiarize yourself with the features of using a particular type.
3. Pheromone lures. They attract the attention of fish, stimulate hunger and cause a schooling reflex, which allows you to collect a lot of fish in one place.

You can get the rest of the secrets of successful fishing for free by reading my other materials on the site.