How do animals breathe underwater?

How do animals breathe in water?

Every living being needs oxygen to live. It is quite easy for the animals on land, as there is enough oxygen in the air that can be absorbed through the lungs. Water contains less oxygen. Animals that live in water have adapted to it in several ways:


What are the names of the animals in this picture?
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Animals that use this technique have to come to the surface of the water again and again to take oxygen from the air. Insects that have realized this type of breathing form breathing tubes. So they hang on the surface membrane of the water. In this way they can absorb oxygen from the air and release carbon dioxide again. The breathing tube works like a snorkel. When snorkeling you are also under water and inhale air through the snorkel. For example, stick bugs, yellow beetle larvae, rat tail larvae and mosquito larvae breathe.


Some animals can dive, but have to return to the surface regularly to breathe. Adult yellow beetles and water spiders use this method, but have developed different techniques. Both breathe in through their abdomen! The beetle pushes the end of its abdomen through the surface membrane of the water. It takes in the air under the wing covers. There it gets into small tubes, which then transport the oxygen through the body. These tubes are called trachea. Water spiders also stretch their abdomen out of the water. But then you take air in reserve with you into the water. This air gets stuck between the fine hair on the abdomen and forms an air-filled "diving bell". This air bubble is then attached to a water plant.


Fish and many other animals that live in the water breathe through gills. The protective gill covers can be seen on the side of the head of a fish. Below that are four gill arches on each side, with many, very thin gill leaves. These are red, which indicates that they are well supplied with blood. The gill cover is closed when water flows in through the mouth. It only opens when the mouth is closed so that the water can flow out through the gills again. The dissolved oxygen is removed from the water and carbon dioxide is released into the outflowing water. This mechanism only works in water, as the wafer-thin gill leaves stick together in the air. You can illustrate this by dipping a few threads of wool in the water. They float back and forth in the water. But as soon as you pull them out of the water, they stick together. Your hair also floats in the water and sticks together when it is pulled out of the water while dripping wet. It is the same with the gill leaves. A fish has to suffocate on land.

Skin breathing

This type of breathing is common in amphibians. Worms and other small animals also breathe through the skin. The skin of these animals is particularly thin and moist. It must not dry out under any circumstances, because then the skin breathers feel like fish on land: they suffocate.