Meeting Abstract

P1.14  Sunday, Jan. 4  Experimentally elevated testosterone suppresses immunity in food-limited sagebrush lizards RUIZ, M.*; DEMAS, G.E.; MARTINS, E.P.; Indiana University, Bloomington mayruiz@indiana.edu

Testosterone (T) has been shown to increase reproduction and decrease immunity in many cases. Yet, although reproductive investment decreases immune function, supplemental feedings can eliminate this effect. In this study, we considered the effect of food availability and T on immune function and reproductive behavior in sagebrush lizards to assess how T and energy availability act to affect these trade-offs. We experimentally manipulated diet and T of males in a natural population. We determined immune response by calculating the bacterial killing capability of collected plasma exposed to E. coli ex vivo. We measured reproductive behavior by counting the number of courtship displays produced in a 20-min sampling period. Immune function increased with supplemental feedings, a finding that was most pronounced in lizards with increased T. Furthermore, T increased immunity in lizards with additional food resources but not in lizards that were not supplemented. Thus, we observe an interactive effect of food availability and T on immune function. Although not significant, T exhibited a trend towards increasing courtship displays. Thus, a trade-off between T and immunity was suggested, but only when lizards were on a restricted diet. Food availability diminished this effect; lizards with supplemental food were able to increase both courtship rates and immunity in the presence of high T. Yet, in non T-treated animals, this trade-off was not as pronounced. Collectively, this study shows that the energetic state of the animal plays a critical role in modulating the interactions among T, behavior and immunity in sagebrush lizards and likely other species.