DNA Methylation and Counterdirectional Pigmentation Change following Immune Challenge in a Small Ectotherm

By allowing for increased absorption or reflectance of solar radiation, changes in pigmentation may assist ectotherms in responding to immune challenges by enabling a more precise regulation of behavioral fever or hypothermia. Variation in epi-genetic characteristics may also assist in regulating immune-induced pigmentation changes and managing the body’s en-ergetic reserves following infection. Here, we explore how dorsal pigmentation, metabolic rate, and DNA methylation in the Flor-ida scrub lizard (Sceloporus woodi) respond to two levels of im-mune challenge across two habitat types. We found changes in pigmentation that are suggestive of efforts to assist in be-havioral fever and hypothermia depending on the intensity of immune challenge. We also found correlations between DNA methylation in liver tissue and pigmentation change along the dorsum, indicating that color transitions may be part of a mul-tifaceted immune response across tissue types. The relationship between immune response and metabolic rate supports the idea that energetic reserves may be conserved for the costs asso-ciated with behavioral fever when immune challenge is low and the immune functions when immune challenge is high. While immune response appeared to be unaffected by habitat type, we found differences in metabolic activity between habitats, suggesting differences in the energetic costs associated with each. To our knowledge, these results present the first potential evidence of pigmentation change in ectotherms in association with immune response. The relationship between immune re-sponse, DNA methylation, and pigmentation change also high-lights the importance of epigenetic mechanisms in organism physiology.