How fish breathe

Fish, like mammals and other animals that populate the earth need oxygen to survive and carry out all their activities. To swim, reproduce, eat, etc., they need large inputs of energy and oxygen that they can not get through the air.

Just as we can not breathe in the water without drowning, the fish, if they are long enough out of the water, also die. So, how do the fish breathe?, Where do they get the oxygen ?, in .com we will solve it, explaining how fish and other aquatic animals have developed a complex system that allows them to obtain the necessary oxygen contributions to live, even if they are under water.

How fish breathe

Fish breathe through complex organs called gills, which in most species is located on both sides of the head, under a mobile membrane that protects them and is called operculum.

Since oxygen dissolves in water 30 to 40 times worse than in the air, fish and other aquatic animals have been forced to evolve so that they can live in the water and get the oxygen they need.

In most fish this system is the gills, which through the so-called countercurrent exchange, they manage to transfer the oxygen of the water to their blood, for this they swallow water through the mouth, forcing it out through the gills and there, they have a dense framework of blood vessels and blood flow that flows in the opposite direction of water. In this way it can be assured that this exchange will be optimized to the maximum, in fact, the fish are left with up to 85% of the oxygen contained in the water they filter.

The gills of the fish

How do they get oxygen out of the water? Although we have already explained a little the operation of the gills, perhaps it is a little complicated to understand the whole process.

In modern bone fish, scientifically called teleosts and which are the majority today, the mouth and its cavity communicate with openings in the side of the pharynx, which are called gill slits, from which the gills develop. These are protected by the opercula, the solid structures located on each side of the head, the typical slits on the sides so characteristic of fish.

Between the gill slits pass curved structures called branchial arches, are two rows of filaments that meet forming a V. From these filaments arise folds or secondary sheets, between 10 and 40 each mm, formed by tissue and large number of vessels blood

In this way, when the fish opens its mouth, the oxygen-filled water enters through it, it passes through this structure and exits through the operculum, but in between, it circulates in the opposite direction through the sheets, which trap everything the oxygen that they can.

Other methods of breathing in fish

By lungs

There are at least 400 species of teleosts that use the air to breathe, the great majority freshwater fish, although almost all also conserve the gills and use each system at will.

Breathing through lungs is used when the oxygen level of the water falls, such as when the temperature rises, because the higher the temperature, the greater the need for oxygen.

However there are also fish that only breathe through lungs, an example of this is Lepidosiren, a South American species that has lungs with two lobes and very simple gills, so they need to breathe air if they do not want to die.

Through the skin

Most fish, when they are born and have not yet developed the respiratory organs, take oxygen through the skin, although as the animal grows and develops the gills breathing through the skin becomes more residual. However, in some adult fish breathing through the skin can account for up to 20% of total oxygen production.