Meeting Abstract
Immune defense against pathogens is energetically costly and, as a result, immune activation is expected to give rise to trade-offs with other costly fitness-related functions, such as performance. Evidence for a trade-off between immunity and performance is accumulating, with infection or immune challenge reducing locomotor performance in a variety of taxa. However, we still lack a full understanding of the physiological processes mediating such trade-off, including the precise energetic requirements of competing traits and how energetic resources are allocated between them. First, we use whole-transcriptome sequencing (RNA-Seq) of muscle fibers to identify the genes and pathways associated with differences in endurance in wild Xenopus tropicalis frogs. Our results indicate that the majority of the genes and processes associated with endurance heterogeneity are involved in lipid metabolic processes and associated with muscle contraction and catabolism. Second, we investigate whether trade-offs between immunity and performance are shaped by limits on the rate of conversion of energy ingested in food into chemical energy (ATP) by oxidative metabolism rather than by the amount of food ingested in the first place. Conducting immune challenges of mosquitofish, Gambusia holbrooki, we show that immune-associated trade-offs are not likely to be shaped by limited oxidative metabolic capacities, but may instead result from limitations in the acquisition, assimilation or efficient use of resources. We discuss how studies of the molecular and physiological processes underlying immunity and performance will further our understanding of life history trade-offs.
