Meeting Abstract
Following a meal, animals can exhibit dramatic shifts in physiology, including rapid growth of the gut and heart, as well as a massive (>40-fold) increase in metabolic rate associated with the energetic costs of processing a meal (i.e., specific dynamic action, SDA: defined as the accumulated energy expended from the ingestion, digestion, absorption, and assimilation of a meal). However, little is known about the effects of digestion on an important physiological and energetically costly trait: immune function. Thus, we tested two competing hypotheses. First, digesting animals up-regulate their immune systems due to increased microbial exposure associated with ingested food. Second, digesting animals down-regulate their immune systems to devote energy to the breakdown of food. We assayed innate immunity (the chief mechanism of host defence across animal taxa) in corn snakes (Pantherophis guttatus) during and after meal digestion. We specifically measured hemoagglutination (antibody-mediated agglutination of foreign red blood cells) and hemolysis (complement-mediated lysis of foreign red blood cells) at two time points (1 and 7 day[s] post-feeding during absorptive and non-absorptive states, respectively). Agglutination was higher during absorption in support of our first hypothesis. Because immune up-regulation likely contributes to SDA, the definition of SDA may need to be expanded to include this costly physiological process.
