Meeting Abstract

P1.65  Saturday, Jan. 4 15:30  Dose and context dependency of the costs of immunity in an introduced ectotherm BRACE, AJ*; SHEIKALI, S; MARTIN, LB; University of South Florida abrace@mail.usf.edu

When exposed to parasites, a vertebrate’s first mechanism of resistance is activation of the innate immune system. However, differences in environmental (e.g., temperature), host (e.g., infection history, reproductive status), and parasite (e.g., virulence) characteristics drive defense strategies (e.g., resistance or tolerance) to vary among or within populations. The main reason for this diversity may be that no single defense strategy is optimal in all contexts as immunity in various forms is costly and tradeoffs among physiological processes must occur to support it. Host investments in defenses should differ contingent on exposure level to a pathogen. Additionally, environmental conditions can alter efficacy of the immune response, especially in ectotherms, whose immune defenses are impacted greatly by temperature. Here, we compared the effect of ambient temperature and multiple doses of a simulated pathogen (LPS), which incurs a protein-intensive response, on allocation of a critical amino acid (leucine) to the liver and gonads of brown anoles (Anolis sagrei), an introduced species in Florida. We hypothesized that leucine allocation to the liver would increase with LPS dose, although the shape of the function for the cost of defense was unpredictable. We expected that low temperature might reduce the slope of the dose-allocation function, change the dose at which resource costs are incurred, or slow overall assimilation rates. We also expected that gonad effects would be opposite the patterns in the liver due to tradeoffs between the immune and reproductive system. Our results will provide a better understanding of the shape of defense cost functions, which will inform when and why resistance, tolerance and subsequently virulence, should evolve in this and related ectotherms.