More Clouds Means Fewer Frogs?

Increased cloud cover brought about by climate change might be killing off many species of tropical tree frogs that depend on "sunbathing" to kill off a potentially lethal fungus, according to new research from the University of Manchester in the U.K.

Working with scientists from The Manchester Museum, which has a large collection of colorful Costa Rican tree frogs, university researchers used a non-invasive technique to study the amphibians' unique skin properties. Their findings indicate the frogs' skin properties change to adjust how much sunlight and warmth is absorbed or reflected. That ability enables the frogs to regulate their body temperatures and avoid overheating, even when they bask in the strong tropical sunlight.

Most frogs avoid too much exposure to sunlight, which can cause them to overheat or dehydrate. But Costa Rican tree frogs prefer to live on high branches and leaves exposed to the sun. The Manchester researchers believe this habit of "sunbathing" might benefit Costa Rican tree frogs by killing off the Chytrid fungus, an infection blamed for many frog species extinctions.

The reflecting ability of tree frogs' skin is associated with pterorhodin, a pigment that enables the amphibians to better camouflage themselves from predators by matching their infrared reflection levels to that of the leaves they sit on.

"With a third of the world's amphibians currently under threat it's vitally important we do our utmost to investigate the reasons why they are dying out at such an alarming rate," said Andrew Gray, curator of herpetology at The Manchester Museum.

The researchers hope to test their hypothesis about the tree frogs' unique skin by traveling to Costa Rica next year to study the frogs in their natural environment. They plan to use the same technique used in the laboratory: optical coherence tomography (OCT), a non-invasive scanning method that can provide images from inside living tissue. The technique is more commonly used to examine the human retina.

"The imaging technique we use is completely non-invasive and does not harm the frogs in any way," Gray said. "As an animal conservationist, I simply would not allow any research that distressed these amazing creatures."

The University of Manchester, "Sunbathing Tree Frogs' Future Under a Cloud." URL: (http://www.manchester.ac.uk/aboutus/news/display/index.htm?id=127843)