Lungs are necessary for almost all of the land animals to survive. But there is still a rare exception - the largest group of salamanders in the world. Recently, researchers finally know how these animals conduct breathing through their skin but not lungs.
The researchers reported on the meeting of the Society for Integrative and Comparative Biology that a copy of a key lung gene shift where it is active, rendering skin capable of efficient gas exchange. This way of breathing without lungs stand for great evolutionary change, one expected to limit the size, lifestyle, and whereabouts of any specie. However, about 448 species of plethodontids family of salamanders might have not gotten the information, for they roam across the Western Hemisphere, South Korea, and Italy, ranging from 25 millimeters to 27 centimeters long, and calling burrows to tree tops home. To figure out the problem, evolutionary developmental biologists did research on one of these species, the dusky salamander (Desmognathus fuscus) by tracking them. Then they found that the lungs actually begin to form, but never develop. On the contrary, this species make more blood vessels to the skin. Other gene studies on gene activity on this species and other vertebrates showed that a key gene is found in the vertebrate lung and the lung exists in 2 copies in salamanders. This gene is active only in the lungs of salamanders which have lungs, but it is also active in the skin, mouth, and throat in the species without lungs. It codes for a protein that helps membranes become more receptive to gas exchange. Thus, the gene's existence in the skin and mouth can just help figure out why some salamanders can breathe without lungs.
By the way, the protein referred above is a surfactant protein. This protein, which is new-found, may be helpful for the treatment of breathing problems.
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