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Biologists show the only 'lungless' frog species does indeed have lungs

A trio of marine biologists at the University of Florida's Florida Museum of Natural History has found that the frog species Barbourula kalimantanensis, previously thought to be the only species of frog without lungs, does indeed have them.

In their published in Current Biology, David Blackburn, Jaimi Gray and Edward Stanley used high-resolution micro-scanning techniques to study the frogs.

In 2008, a different team of researchers captured and dissected 11 B. kalimantanensis, known more commonly as the Bornean flat-headed frog, but failed to find any evidence of lungs. The finding suggested the species was the only frog that did not have lungs—to survive, it would have to pull oxygen through its skin from the water in which it lived.

The lack of lungs has been observed in one caecilian and some salamanders, which means that it could also be the case with frogs. The research team noted at the time that the frogs lived in Bornean rivers with strong currents where large lungs with strong buoyancy would make survival difficult. The research team was not able to confirm that this was the case, however.

For this current study, the new research team repeated the work done in 2008, but this time, also used a high-res micro-CT scanner to get a closer look at a particular part of the frog, a hole in the bottom of the frog's mouth; the feature appeared in all the specimens they studied. They also found what looked like a tiny glottis connecting the hole to the rest of the mouth. A closer look revealed that it was a pair of small, thin lungs.

The research team is not ruling out the possibility that the frog does get some of its oxygen through its skin and the rest via its lungs. They note that more work is required to find out if that is the case.