Respiration, the basis of all living things. We may survive without water for a day but without the next breath, we are gone immediately. Respiration for humans and animals is basically a process where oxygen is inhaled by the lungs which are provided to tissues and cells of the body, finally, after absorption of oxygen, carbon dioxide is released from our body. But what would happen if you had no lungs? or you needed to hibernate which switches your lungs off? Nature has already created unique species which have a unique mechanism of breathing. It is known as Skin Breathing.
What is skin breathing?
Skin breathing or Cutaneous respiration, as the name suggests is a process of absorbing oxygen by the skin. It should be noted that there are certain criteria if one wishes to breathe from the skin, as the animal must have moist skin. An animal’s skin absorbs the oxygen and transports it to the entire body by the blood vessel just under their skin, this process of absorption is known as Diffusion. Also, carbon dioxide is released similarly.
But why would animals’ opt for such sticky breathing? It is because this type of breathing enables the organism to breathe both underwater and out of the water. Additionally, this process allows them to absorb even the tiniest amount of oxygen from the air which is essential for survivability in areas where water is scarce.
Animals that breathe through the skin
- Frogs: These little amphibians have been around for over 100 million years and you’d be surprised to know that not much has changed in the way that these creatures look. Although frogs possess lungs it is used when they are unable to absorb oxygen via their skin. While submerged underwater, they can easily breathe with their body as it is permeable to water. Once a frog jumps out of the water, their bodies secrete mucus around its skin to keep them moist. This mucus allows them to breathe outside easily. Though toads are capable of breathing through their skin as well their skin is usually drier and they rely more on their lungs.
- Fishes: While in schools we learned that fishes, other than whales and dolphins strictly breathe through their gills, which is absolutely true, however, there are some species of fishes such as the Asian mudskipper that use cutaneous breathing. Criteria are similar, as the fish must be moist to breathe this way, then they simply diffuse the oxygen via their skin and can breathe. In addition to that, they have a special lining in their mouths, which enables them to absorb oxygen. Also, their gills are made in a way so that they can retain water bubbles in them so when needed, they breathe through those as well.
- Sea snakes: Unlike their terrestrial counterparts, sea snakes are quite comfortable breathing in the water. While some species of land snakes such as the anaconda can hold their breath for up to 15 minutes underwater but this isn’t the same as compared to Hydrophis species. These snakes do have a special system of nerves that allows the air to be circulated in their head where a similar organ to the lung is located. Also, like other animals these are capable of absorbing oxygen from the water molecules, the concentration of oxygen within their body is fairly low compared to the seawater which allows the diffusion to occur.
- Salamanders: These moist creatures are often mistaken for lizards, however, unlike lizards they are amphibians. They are existing on this planet alongside the frogs for over 100 million years as well. Though some species of them like the giant Chinese salamander switches half of the breathing to lungs while on the surface, all of them strictly use cutaneous breathing while underwater. Also, their larvas breathe solely through their skin and they start preying on smaller insects and other small marine animals as soon as they are hatched. Similar to frogs, salamanders have drier counterparts known as newts. They are able to absorb oxygen through their skin as well but not always.
- Earthworms: Unlike other organisms on this list, earthworms are strictly cutaneous breathers as they do not possess lungs. Although earthworms are able to live for several days underwater they usually prefer living within the earth as their name suggests. The way they breathe is by absorbing the oxygen which is present in the soil. You may have noticed worms usually crawl out to the surface whenever it rains, contrary to the belief that they are drowning, they come out to breathe as the soil becomes too wet to allow the absorption of oxygen. Though slugs and snails are able to breathe with their skins as well they primarily use gills on their skin.
As you can see life on our planet is quite fascinating. The way we breathe is quite different but it is ultimately oxygen that is our primary source of life. Primarily, this skin breathing form is used by amphibians.