How the fish breathe in the water. Than fish breathe in water

Absolutely all living beings need oxygen. They can take it from atmospheric air or water. But how do the fish breathe? They do not have such complicated organs as the lungs. But the fish have gills. They help absorb this gas when breathing. At the same time, they function much more efficiently than our lungs, because they are able to take up to 30% of the oxygen dissolved in it from the water. But in reality, the methods of breathing in fish are much greater. All of them developed as a result of a long evolution and are inherent only in certain species.

How do fish breathe with gills?

Of course, all fish have gills without exception. Their form is diverse. Some species have sacs, others have plates or petals. But all these adaptations are aimed at one thing - the creation of a larger surface, permeated with a dense network of capillaries, with a relatively small volume of space.

Water with oxygen dissolved in it enters through the pharynx at the moment when the fish opens its mouth wide. The gills themselves are rather tender organs, so a dense gill cover covers them from above. It also takes a direct part in breathing. At the moment when water enters the pharyngeal cavity, the gill cover fits tightly to the head. So they prevent the outflow of liquid. When the gill covers open, the pressure changes, and water enters a special cavity. It is permeated with a dense network of blood vessels. The gill arches straighten out, and the gas exchange process takes place. In the blood comes oxygen, and from it are derived not only carbon dioxide, but also metabolic products. The water comes out of the gill cavity through special cracks. This is how the breathing of fish.

Fish that breathe through the skin

Of course, the fish breathe with gills. This is known to all. But then how to explain the fact that some species that are out of the water, in wet grass or land, are able to live there for several hours? How do fish breathe in such conditions? Certainly not through the gills.

A number of species, such as crucian carp, eel, carp, carp, in the process of evolution there was an additional opportunity. They can absorb oxygen through the entire surface of the skin. This is especially true when the level of this vital gas in the water drops to a critical level. Then the gills become ineffective, and dermal respiration comes to the fore.

How do labyrinth fish breathe?

Many owners of aquariums noticed how the fish breathe. They often swim to the surface of the water and slightly protrude outward. What are they doing this for?

Very many varieties of aquarium fish have a specific respiratory organ - a labyrinth. With its help, they can actually absorb oxygen not from water, but from atmospheric air. At the same time, the fish should rise at least once every few hours to the surface and inhale. Otherwise, she will die.

There is a gill labyrinth on either side of the head of the fish. It is above the gills. When the fish swallows an air bubble, it enters the spongy chambers of the labyrinth. Their walls are densely covered with capillaries. They penetrate oxygen, which then spreads to all organs and tissues of the body. Gill labyrinth helps fish not only to survive in an oxygen-depleted body of water, but also to move to another.

Fish breathing through the intestine

Perhaps, many will be surprised, but there is one kind of fish that uses the intestines for breathing. This is the catfish of the genus Coridoras. They breathe atmospheric air. Although this is not entirely true. Unlike the same labyrinthine fishes, they do not have any special organs. The speckled catfish is able to absorb oxygen by its stomach. It's a fish that breathes air. She simply swallows it and pumps it into a swim bladder. Here, oxygen is assimilated.

Fish that can climb trees

So, what fish breathe in the water, it is understandable. But what about those that can stay out of the water for a few days? Do you think these do not exist? Not at all. A bright representative of these fishes is a perch. He lives in the Far East.

The gills of this unique fish are arranged so that it is able to absorb oxygen from the air. In addition, she has a special structure of scales, which allows her not only to move on the ground, but also to climb trees. Actually, for this feature, it got its name.

By the way, this species is far from being the only one. There is another fish that can breathe air - it's a muddy skipper. He dwells in those parts of Africa, where severe droughts are often observed. This fish has developed an interesting way to survive these unfavorable periods for itself. When the reservoir dries up, the skipper buries into the silt. There he is able to be without water for several months. Only when the water comes back, he comes out of his improvised refuge. This is how the majority of lungfish enter. This group deserves special attention.

Lungfish

Litterfish belong to a very ancient group. Paleontologists find the remains of these creatures in the layers and sediments of the Paleozoic era. For a long time they were considered completely extinct. And only after studying the nature of Australia and Africa in the 19th century was a stunning discovery. Modern forms of lungfish were found. This not only influenced the views of scientists on the systematics of vertebrates, but also made its own corrections to the evolutionary doctrine.

In all of the lungfish, in addition to the characteristic gills, one or a pair of lungs are also found. This is a modified swim bladder. With mammalian lungs these organs have nothing in common. Their walls are permeated with numerous capillaries, through which gas exchange takes place. Do fish breathe with oxygen dissolved in water? Of course. But only when there is enough water in the water. The lungs need them only to wait a long period of drought, walled in mud, or to move from one reservoir to another. As a rule, they have developed fins, which can play the role of limbs. Thus, lungfish can perform transitions lasting even a few days.