Lungs. Both humans and the majority of animals that have internal skeletons cannot survive without them. Some exceptional amphibians, however, no longer bother with their delicate, mucus-filled organs.
Scientists have found that some creatures without lungs first begin to produce these breathing organs before their developing process changes its mind.
These species, the plethodontid salamanders, have survived without lungs for at least 25 million years by breathing via their slimy skin and mouth tissues. They must cover themselves in goo to do this because dry skin cannot absorb oxygen; it must remain moist, like they are wearing their lung mucous on the outside.
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The largest group of salamanders, the lungless plethodontids, has roughly 478 species and is primarily found in the Americas, with a small number also occurring in Europe and South Korea.
Zachary Lewis and colleagues from Harvard University’s Department of Evolutionary Biology examined these cold-blooded water enthusiasts more closely because little is known about how these frogs lose their lungs.
Science Advances reported the results of this study.