Humans and most animals cannot survive without lungs.. But some creatures can do without them. Scientists have found that in some amphibians, known as pletodontid salamanders, lungs begin to develop, but disappear at a certain stage of development, according to Science alert.

Researchers note that these creatures have successfully managed without lungs for 25 million years by breathing through the mucous membranes of the skin and mouth tissues.. In order to do this, they must be covered in slime..

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Pletodontid salamanders are the largest group of salamanders, with 478 species found mainly in South and North America, but also in Europe and South Korea.. Little is known about their ability to lose lungs, so scientists from Harvard University decided to closely observe these creatures..

Researchers have found that embryos of several species of salamanders do develop lungs. They successfully develop for about three weeks, and then something interrupts this development.. By the time a baby is born, the lungs are programmed for apoptosis - spontaneous cell death..

Scientists believe lung formation stops because cells don't receive the regulatory signals they need to reproduce, which, in other vertebrates, come from tissues that surround the developing lungs, called mesenchyme..

Although these animals do not have traces of lungs as adults, they still have the genes that are necessary for their growth.. However, some of the mechanisms needed to complete this process are missing..

It is likely that the lungs begin to develop, since this process is necessary for the formation of other organs, such as the heart..