CONTRERAS, H*; TALBOT, C; Calif. State Univ. San Bernardino: Osmoregulatory Behaviors in Pacific and California Tree Frogs: Differences in ability to find water and species� salt concentration preferences.
Amphibians are frequently faced with excessive dehydration through evaporative water loss across the skin. To counteract the effects of quick dehydration, many species have developed behavioral adaptations for proper water balance such as the water absorption response (WR). Before inducing WR, amphibians must be able to detect a water source and its solute concentration in order to ensure rehydration. This study aimed to examine the proficiency of Pseudacris cadaverina and Pseudacris regilla in detecting available water sources and also in determining the species� preference in salt concentration before inducing WR. Frogs were dehydrated to 15% (P. regilla) and 22% (P. cadaverina) of their initial hydrated mass before being placed in the observation tank. In the �detection of water source� experiment, the tank was divided into four equal quadrants; one quadrant containing a wet tissue, the other a dry tissue, and two empty. We measured time to find wet tissue, time in each quadrant, and direction of movements. In the �salt preference experiment� the observation tank was divided into six sections, each containing a specific NaCl concentration: 1, 50, 100, 150, 200, 250mM. We then measured time in each section, time in each dish and time in WR. There was no difference in the proficiency of Pacific or California Tree Frogs in finding a water source and movement occurred randomly. There was also no difference in salt preference between the two species. Dehydrated P. regilla found a source of water less frequently and showed WR less than when fully hydrated. The opposite trend was shown for P. cadaverina. These results continue to support the idea presented in previous studies (Contreras and Talbot, 2004) suggesting that Pacific Tree Frogs drink opportunistically unlike California Tree Frogs which drink only when “thirsty”.
