Meeting Abstract

117.5  Monday, Jan. 7  Are extreme temperatures physiologically stressful? An experimental examination of thermal variation on corticosterone levels in two species of alligator lizard TELEMECO, R.S.*; ADDIS, E.A.; Iowa State Univ., Ames; Gonzaga Univ., Spokane, WA telemeco@iastate.edu

Temperature profoundly affects organisms and extreme temperatures can compromise vital functions. Exposure to such extremes might be highly stressful, particularly for ectotherms. A common indicator of stress is elevated levels of glucocorticoid hormones (GCs). At high levels, these hormones induce responses that promote survival; however, continued GC elevation (chronic stress) may negatively affect fitness. If extreme temperatures induce elevated GC levels, chronic stress may be important near the thermal limits of species’ geographic ranges and as climate changes. Surprisingly little work has been done to measure the effects of thermal conditions on GCs in ectotherms. To help bridge this gap, we experimentally tested the effects of variation in body temperature on plasma GC levels in two congeneric lizards adapted to different thermal environments, southern and northern alligator lizards (Elgaria multicarinata and E. coerulea). Using a randomized repeated measures design, we quantified circulating plasma GC levels in 15 adults of each species after 5 hrs exposure to four ecologically relevant thermal treatments (10, 20, 28, and 35 C). For comparison, we also quantified baseline GC levels for each individual. Thermal treatment had no effect on GC levels in E. multicarinata but E. coerulea exposed to warm temperatures had slightly increased GC levels compared with those exposed to cold temperatures. Even so, GC levels after thermal treatments were never significantly different from baseline GC levels. These results suggest that while exact GC response to thermal conditions may be species dependent, extreme temperatures may not induce GC levels indicative of physiological stress.