A fingernail-size frog that can morph its skin texture from spiny to smooth in just minutes is the first shape-shifting amphibian ever found, according to a new report.
The tiny "mutable rain frog" (Pristimantis mutabilis) was discovered on the western slopes of Ecuador's Andes Mountains, in a protected cloud forest reserve. A new glass frog species, the Las Gralarias glass frog, was reported there in 2012.
Scientists found the shape shifter during their annual survey of the reserve's amphibian population. They first spotted the frog in 2006 and only snapped a photo, but later realized it could be a newfound species when they enlarged the image. They started calling the frog a "punk rocker" for its spiny-textured skin.
A female mutable rain frog is just 0.8 to 0.9 inches (20 to 23 millimeters) long, and males are even smaller, the new study reports. The rain frogs are a species-rich group that skips the tadpole stage and develops into frogs directly within their eggs.
Lead study author Juan Guayasamín first suggested the little frog could be a new species, said one of the scientists. In 2009, the scientists finally saw another punk rocker frog and grabbed it for a detailed photo session, putting it in a small plastic cup overnight.
But when they opened the cup the next morning, the frog's spines were gone. Thinking they had nabbed the wrong frog, they added moss to the cup to make the frog more comfortable until they could return it to the forest that night.
But they couldn't believe their eyes the next time they checked on the frog. Its spiny skin texture had returned.
The scientists documented the transition with a series of photos on a smooth white board, showing the frog transform from prickly to smooth in about five minutes (photo below).
The scientists think the shape-shifting spines may provide camouflage in the mossy forests, but the idea still needs to be tested. Researchers also don't yet know how the frog morphs its skin from smooth to spiny, and then back again.
However, Guayasamín has confirmed that P. mutabilis is a new and unique species through genetic tests and a description of the frog's body size, shape and color. Study co-author Carl Hutter, of the University of Kansas, also documented the frog's calls, identifying three songs that are different from other species.
During the study, Hutter also discovered a relative of the punk rocker rain frog that can also change its skin texture. This previously known species, called Primates sobetes, has similar markings but is twice as large as the newly found rain frog.
The shape-changing abilities of both frogs are reported on March 24 in the Zoological Journal of the Linnean Society.
The two shape-shifting frogs are in different groups, which suggests that the trait evolved independently or is present in more species than has been previously recognized.
PHOTO: The newly found shape-shifting rain frog rests on a leaf.
CREDIT: Katherine Krynak.