Frog Wax

Many amphibians, like this tree frog (Phyllomedusa hypochondrialis), have skin that offers little resistance to evaporative water loss. To compensate, this frog secrets a waxy substance and then uses a series of wiping motions to rub the secretions over its entire body.

"This self-wiping is a complex behavior involving the use of all four limbs to stroke or rub all dorsal and ventral body surfaces, including the limbs," said Nadia A. Gomez of the University of Florida and her co-authors. "Thus, the animal is protected from dehydration, provided the external film of lipids is not physically disrupted by movements or other disturbance."

Tree frogs characteristically go into a resting posture after wiping themselves, tucking their limbs tightly against or beneath their body and closing their eyes.

They found this posture after "waxing" allows tree frogs to limit rates of surface evaporation to as little as 4 percent of that from a free water surface in the same environment.

Scientists had wondered if this resting posture also served as a quasi-hibernation in which the waxed frogs lowered their metabolic rates to conserve energy and lower evaporation. They found that waxed, inactive frogs had about the same metabolic rate as unwaxed, dehydrating frogs. The findings are detailed in the November/December 2006 issue of the journal Physiological and Biochemical Zoology.

--LiveScience Staff

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Credit: Jason Ortega