The thermal environment of arboreal pools and its effects on the metabolism of the arboreal, oophagous tadpoles of a Taiwanese tree frog, Chirixalus eiffingeri (Anura: Rhacophoridae)

Abstract

We have studied seasonal and diurnal fluctuations of water temperature in bamboo stumps and the effect of temperature on the energy metabolism of arboreal, oophagous tadpoles of Chirixalus eiffingeri. We collected tadpoles (Gosner stage 28–29) in February and August from Chitou, Taiwan and acclimated them to 12 and 22°C. Using a closed system, we measured tadpole oxygen consumption ( V ̇ o 2 ) at 12, 17 and 22°C. The water temperature was lowest in February (11–13°C), increased rapidly during March and April and was highest from May to August (20–24°C). Diel fluctuations in the temperature of the pools of water in bamboo stumps mirrored fluctuations in air temperature. Tadpoles collected in February and August exhibited metabolic compensation in that tadpoles acclimated at 12°C had significantly higher V ̇ o 2 than those acclimated at 22°C. There are at least two possible explanations for the presence of metabolic compensation in C. eiffingeri tadpoles. Firstly, the larval period of C. eiffingeri ranges from 40 to 78 days, a tadpole could experience relatively large fluctuations in body temperature (up to 10°C) during the development. As a result, C. eiffingeri tadpoles most likely evolved metabolic compensation to maintain activity levels under different thermal environments. Secondly, because arboreal pools are small, thermally unstratified and, aquatic microhabitats, tadpoles are unable to behaviorally select preferred temperatures. As a result, metabolic compensation allows tadpoles to regulate their physiological functions.