Water balance responses of the hylid frog Litoria aurea

Cutaneous and antidiuretic water balance responses of the hylid frog Litoria aurea to dehydration and exogenous arginine vasotocin (AVT) were examined. Both dehydration and AVT caused an increase in the rate of water uptake through ventral skin. Dehydration (in one of two experiments) and AVT also caused a reduction in the rate of bladder urine accumulation. During rehydration, rates of water uptake through ventral skin were seven times higher than through the average body surface of immersed frogs. Treatment of normally hydrated frogs with AVT in vivo caused increased cutaneous water uptake and a reduction in glomerular filtration rate; together these produced water retention equivalent to 27% above original body weight. Pelvic skin had a higher resting rate of osmotic water flow (OWF) in vitro than did pectoral or dorsal skin and was the only region to show increased OWF in response to AVT. The cutaneous hydroosmotic response of L. aurea to AVT is unusually large for a semiaquatic frog, and this may reflect the basking habits of this species or its position within the Hylidae.