Time Course of Temperature Acclimation of Locomotory Performance in the Toad, Bufo woodhousii woodhousii

Abstract

to either 20 C or 30 C for 7 wk, then exposed them to the alternate temperature to determine the rate of acclimation to the new temperature. Acclimation was considered complete for a given index when there was no difference in performance between experimental and control groups. To determine rate of cold acclimation, performance of toads acclimated to 30 C for 7 wk was tested at both 20 C and 30 C after 1-11 d exposure to 20 C. The half-acclimation time ('/2 AT) for cold acclimation of all three locomotory indices was between 3-5.7 h when performance was measured at 20 C, but was approx. 4 d when performance was measured at 30 C. To measure rate of warm acclimation, we tested toads at 30 C after 7 wk at 20 C. The /2 AT for warm acclimation of mean jump length and mean jump frequency was approx. 20 h. Therefore, for a given locomotory index, the rate of change in the index differed at different test temperatures; the attainment of a new steady state during cold acclimation occurred more rapidly when toads were tested at 20 C than at 30 C. Also, the apparent rate of cold acclimation was slower than was the rate of warm acclimation when performance was measured at the same temperature 30 C. Therefore, different whole animal physiological processes (e.g., locomotion, metabolic rate) may respond to acclimation at different rates and thus preclude simple generalizations on the adaptive significance among processes.