EVAPORATIVE WATER LOSS AND COLOUR CHANGE IN THE AUSTRALIAN DESERT TREE FROG LITORIA RUBELLA (AMPHIBIA HYLIDAE)

WA Museum Records and Supplements | Updated 1 decade ago

Abstract - The desert tree frog, Litoria rubella, is a small (2-4 g) frog found in northern Australia. These tree frogs typically rest in a water-conserving posture, and are moderately water-proof. Their evaporative water loss when in the water-conserving posture is reduced to 1.8 mg min^-1 (39 mg g^-1 h^-1) and resistance increased to 7.3 sec cm^-1, compared with tree frogs not in the water-conserving posture (7.6 mg min^-1, 173 mg g^-1 h^-1, 1.1 sec cm^-1). When in the water-conserving posture and exposed to dry air, the tree frogs dramatically change colour from the typical gray, brown or fawn, to a bright white. The toe-web melanophore index decreases from 3.8 for moist frogs, to 2.3 for desiccated frogs. The high skin resistance to evaporation and white colour of tree frogs when exposed to desiccating conditions appear to be important adaptations to reduce evaporative water loss and prevent overheating when basking in direct sunlight.