Meeting Abstract

31.3  Thursday, Jan. 5  Variation in assimilation rate among populations of Sceloporus lizards at constant and fluctuating temperatures BORCHERT, JD*; RUSCH, T; ANGILLETTA, M; Arizona State University jdborche@asu.edu

We examined the assimilation rates of Sceloporus tristichus from Utah and Arizona and Sceloporus consobrinus from Nebraska and Texas. Two separate experiments were conducted: one in which lizards were held at constant temperatures (30, 33, or 36°C) and a second in which lizards were exposed to different diel cycles of temperature (either 6, 10, or 14 h at 33°C and the remainder at 20°C). During each experiment, we measured food intake and waste production. At constant temperatures, feeding rate increased as temperatures increased. At fluctuating temperatures, feeding rates at 10 and 14 h of high temperature were nearly double that at 6 h of high temperature. However, feeding at 10 and 14 h of high temperature were similar. This result contradicts recent mechanistic models, which assume that energy intake increases linearly with the time available for thermoregulation.