When we breathe, we take in oxygen and release carbon dioxide. This allows the body to use chemical energy. Just as a candle flame or a fire needs oxygen to burn, so all our cells need oxygen. Without it they will die in just a few minutes. This may well be true for advanced carbon life forms everywhere. Our lungs are wonderful organs.
Fishes use gills to breathe, and frogs and other amphibians get some of their oxygen through their damp skins. You can use these methods on your life forms, or try to invent something else. Here is something that Dr Viau thought up. Would it really work? I don't know. The snorvep is a small, cold-blooded, rather slow-moving animal. Something like this *might* work. A large, fast animal, like a race horse, could not get enough oxygen this way.
Sample Description: The snorvep breathes through tubes in the dark bumps on its back. Snorveps lived in water for a long time, and probably came onto land as the shallow water that was their habitat became silted in and bog-like. They are still water breathers, which works partly because their atmosphere is so humid and frequently rainy.
The picture shows details of their breathing apparatus. The skin on the back is rather tough and rubbery. The little black cone-shaped bumps are hard, and the skin between them is tough but flexible, and dotted with many small pores. These small pores have little valves of skin that allow water to come in but not go out.
The blue channels are lined with cells that handle the gas exchange, absorbing oxygen from the water and releasing carbon dioxide to the water. A thick mat of blood vessels and water-holding channels lies under the skin. You can see a large red blood vessel that lies a little way under the skin. Muscles (yellow in the diagram) run on both sides of it. When the muscles contract, the water-holding channels are squeezed, and water shoots out of the dark bumps. This aerates the water, some of which falls back onto the skin between the bumps. The muscles relax, water flows in through the openings on the skin between the bumps, and the channels are filled again.
The snorvep is cold-blooded, so when it is cold the chemistry works slowly, and breathing can be slow, too. When conditions are warmer and chemical reactions take place more quickly, breathing can be speeded up.
If the snorvep starts to feel dry and needs more water, it can always slide into a nearby puddle or pool. With all the rain and fog on this planet, keeping moist is no problem.