Meeting Abstract

53.4  Monday, Jan. 5  Interactive effects of testosterone and immune challenge on aerobic performance in House Sparrows BUTTEMER, W.A.*; O’DWYER, T.W.; HOYE, B.J.; KLASING, K.C.; ASTHEIMER, L.B.; University of Wollongong, Australia; Univesity of California, Davis; Netherlands Institute for Ecology, The Netherlands; University of California, Davis; Univesity of Wollongong, Australia buttemer@uow.edu.au

There is a common perception that rises in circulating testosterone result in immunosuppression in breeding male vertebrates. Because immune responses are believed to come at a cost, immune challenge is more likely to result in reduced peak aerobic performance in pre-breeding than in breeding males. We examined this question by measuring basal and peak metabolic rates in male and female sparrows under four different treatments: 1) testosterone treated/immune challenged, 2) testosterone treated/sham injected, 3) empty implants/immune challenged, and 4) empty implants/sham injected. The immune challenges consisted of three consecutive intraperitoneal injections of sheep red blood cells along with an intramuscular injection of keyhole limpet haemocyanin (KLH). Peak metabolic rate (during repeated takeoff and short flight) and basal metabolic rate were measured before and after each of these treatments. Testosterone significantly reduced specific immunity in males, but had no significant effect on antibody formation to KLH in females or on constitutive immunity in either gender. Neither peak metabolic rate nor basal metabolic rate were affected by testosterone or by immune challenge. We therefore conclude that testosterone-induced immunosuppression is very limited in male sparrows and has little consequence on energetically costly activities.