Meeting Abstract
Immune function can vary based on resource availability, and most studies of such influences have focused on the co-investment of energy into immune and other physiological functions. When energy resources are limited, trade-offs exits, which can compromise immunity for other functions. As with energy, water limitations can also alter various physiological processes, yet water has received little consideration for its role in possibly modulating immune functions. We examined the relationship between immunocompetence and hydration state using the western diamond-backed rattlesnake (Crotalus atrox). This species is known to undergo substantial seasonal fluctuations in water availability, experiencing periods of considerable dehydration during the seasonal drought. To measure changes in plasma osmolality and immune function over time, we withheld food and water from individually housed adult C. atrox held in an environmental chamber for 16 weeks. We collected blood from each animal as they dehydrated and collected a final sample after animals were given ad lib water at the end of the experiment. We examined the relationship between immunocompetence and hydration state using several plasma assays to assess innate immune function– lysis, agglutination, bacterial killing. To ground-truth our laboratory work, we collected blood samples from free-ranging C. atrox during the milder and relatively moister early spring season, during the hot-dry season, and during the hot-wet season. We determined the osmolality of these samples and performed the same immune function assays used for the laboratory study. Results from both the lab and field experiments produced consistent but counter-intuitive results demonstrating that dehydration enhanced innate immune mechanisms.
