The Effects of Temperature on the Immune Performance of the Northern Red-Bellied Cooter (Pseudemys rubriventris)

With the continued emergence of new wildlife diseases, understanding the immune system of wildlife has become an increasingly important task. Unfortunately, most modern immune research focuses on birds and mammals, leaving the immune function of ectotherms a field that demands more attention. Because of this bias towards endotherms that regulate their own body temperature, we specifically lack information about how body temperature affects immune performance. Climate change and the reliance of ectotherms on temperature for biochemical reactions make studying this relationship between thermal performance and immune function a worthwhile contribution to the existing literature. The goal of this experiment was to add to this collective knowledge of reptile immune function by analyzing how temperature affects in vitro innate immune performance in the Northern Red-Bellied Cooter (Pseudemys rubriventris). We hypothesized that turtles would perform better at moderate temperatures between 30°C and 40°C and would not respond as well at more extreme temperatures. To accomplish this, turtles at Lake Fred were hand-captured and had a blood sample taken. An immune assay was performed on the isolated plasma samples to assess the ability of the turtles’ plasma to kill a gram-negative bacterium, E. coli, at a range of temperatures (15-45°C). A thermal performance curve was generated for each turtle, and a repeated measures ANOVA test was performed to identify differences in bactericidal ability at different temperatures. The results showed a significant effect of temperature on immune performance, with a mean optimal performance temperature of 32.8°C and an 80% performance breadth ranging from 25.2-40.4°C.