Abstract
Anthropogenic environmental changes have led to disease emergence, often threatening biodiversity. To better assess the risk that emergent diseases pose for natural populations we need to understand the dynamics of immunity in the wild. Immune function variations can affect ecologically important process.3 It has been proposed that these variations arise due to trade-offs, that is, the allocation of limited energetic resources among competing, costly physiological functions. Nevertheless it is not entirely clear which factors determine the allocation of resources among physiological functions.2,3 It is well known that adult immune traits may be influenced by the pathogenic environment experienced during ontogeny.1 However, there is as yet little information regarding the development of the immune system from an ecological context, nor is it known whether ontogeny affects the way resources are allocated towards immune functions. Using ecoimmunological tools, we investigate the inflammatory response and its relation to body condition during the early development stage of California sea lion pups (Zalophus californianus). We examined immune activity and body condition of California sea lion pups from shortly after birth (2–3 weeks) and at 5 months of age, using a linear model framework. The magnitude of the inflammatory response elicited by the neonatal California sea lions was significantly explained by the pup's body condition (LM, n = 12, adjusted R-squared = 0.5912, F-test: p = 0.0037). In contrast, the inflammatory response elicited by older pups was explained not only by their body condition but also by their overall health status, assessed by total and differential leukocyte counts (GLM, n = 18, body condition as an interactive explanatory variable: p = 5.018e-05, neutrophils as an explanatory variable: p = 0.01426). Our results highlight the relevance of studying the development of the immune system within an ecological framework in order to identify the existence of true trade-offs, and call for a better understanding of the dynamics of immunity in wild populations. Perhaps more importantly, our study can help identify periods of immune vulnerability associated with growth and development which could lead to increased disease susceptibility during early and often critical life stages of a large mammal. This information may be useful to include in management and conservation plans of this and related species.
* Presenting author
+ Student presenter
Literature Cited
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2. Graham AL, Shuker DM, Pollitt LC, Auld SKJR, Alastair J, Little W, Little TJ. 2011. Fitness consequences of immune responses: strengthening the empirical framework for ecoimmunology. Funct Ecol 25:5–17.
3. Martin LB., Hawley DM, Ardia DR. 2011. An introduction to ecological immunology. Funct Ecol 25:1–4.