Meeting Abstract
29.6 Jan. 5 Corticosterone modulation of reproductive and immune systems trade-offs in female tree lizards: Long-term corticosterone manipulations via injectable gelling material FRENCH, S. S.*; MCLEMORE, R.; VERNON, B.; JOHNSTON, G.I.H.; MOORE, M.C.; Arizona State University; Arizona State University; Arizona State University; Arizona State University; Arizona State University ssfrench@asu.edu
Physiological trade-offs may arise because multiple costly processes compete for the same limiting resources. While direct competition for resources has been demonstrated between reproduction and immune function, the regulation of this competition remains unclear. Corticosterone (CORT) is a likely mediator due to both its role in mobilizing energy stores throughout the body and regulating physiological responses to stressors. We therefore manipulated CORT concentrations and resource availability in pre-reproductive and reproductive female tree lizards (Urosaurus ornatus) to test the hypothesis that CORT regulates the distribution of limiting resources between the reproductive and immune systems. To manipulate circulating concentrations of CORT we utilized a novel method of hormone implantation. The polymeric compound was injected in liquid form and was allowed to gel in situ providing a slow release delivery device where the hormone-treated animals had plasma CORT concentrations comparable to high physiological concentrations. This method of hormone delivery eliminated the application of additional wounds to the animal or repeated handling required by other methods. We found that CORT treatment suppressed immune function, but only when animals were energetically compromised. Specifically, wound healing was suppressed in all CORT-treated reproductive animals and in all CORT-treated animals (pre-reproductive and reproductive) undergoing food restriction. The context-dependent action of CORT renders it adjustable to changing environmental conditions and may allow for the strategic suppression of specific functions depending on resource availability.
