for National Geographic News
The creature, found in Guyana, is part of the wormlike group of amphibians known as caecilians. Only one other caecilian species is known to live without lungs.
In general, the presence of lungs is among the key characteristics that make amphibians different from fish.
Until recently, scientists thought salamanders were the only amphibians that lack lungs. But in 1995 researchers found the first known lungless caecilian, and in 2008 another team reported a tiny, lungless frog.
The new species is even more of a surprise, because the animal—named Caecilita iwokramae—is strikingly different from the other known lungless caecilian, the study authors note.
Caecilita lives on land and is just 4.4 inches (11 centimeters) long, while its lungless relative is fully aquatic and reaches 27.5 inches (70 centimeters) in length.
More Lunglessness to Come?
Together with the small lungless frog, the diminutive new caecilian suggests that lunglessness is most likely to appear in amphibians that are relatively small, the study authors say.
That's because the lungless animals breathe through their skin. Small body size increases the area of porous skin in relation to body mass, making it easier for the animal to absorb oxygen from the air.
But why are the animals lungless?
"This is conjectured about, but there are no real answers," said Marvalee Wake, an evolutionary biologist at the University of California, Berkeley, who co-authored the study with Maureen Donnelly of Florida International University.
"I speculate that losing lungs might decrease body diameter and help [Caecilita] to burrow better," she said. "But quite frankly, they may [have lost] them simply because they no longer need them."
Wake admits that this explanation does not really resolve how the aquatic caecilian or the frog might have lost their lungs.
But given the diversity among lungless creatures, she added, "we are going to see a lot more lunglessness as we look closer at the amphibians."
Findings appear online today in the Proceedings of the Royal Society B.
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