Do crocodiles breathe in atmospheric oxygen or dissolved oxygen?
All reptiles, including crocodiles, have 3-4 chambered hearts and well developed lungs. They breathe atmospheric oxygen mainly. Some of them, like turtles and crocodilians, may breathe in a small amount of oxygen through cutaneous respiration (oxygen being taken in through the skin, usually the lining of the mouth). During hibernation, cutaneous respiration may allow turtles to get enough oxygen to remain submerged for long periods of time without surfacing for air. Alligators can remain submerged under ice for 8 hours, no doubt because its bodily functions are slowed down by the cold temperature, but probably because they get enough oxygen from cutaneous respiration to stay alive.
