Meeting Abstract
Susceptibility to stressors and disease varies with ontogeny. The prevalence and virulence of pathogens tends to be highest in larvae, neonates, and juveniles, but decline through adulthood. While immature immune systems often contribute to high susceptibility in developing animals, emerging evidence suggests organ physiology and nutrient allocation may play a central, but still poorly understood, role. We examined the effects of stress and ranavirus infection on larval amphibians, a model system to test these interactions. Metamorphosis requires a substantial amount of energy and concurrent reorganization of the digestive tract exacerbates this strain, as larvae must complete metamorphosis with stored energy. Stress-induced, accelerated metamorphosis may increase this cost. Similarly, ranavirus accelerates metamorphosis and the additional cost of infection has unknown effects on larval energy budgets. We measured oxygen consumption and energetics of wood frog (Lithobates sylvaticus) larvae exposed to exogenous stress hormones or ranavirus. To determine if stressed or infected larvae oxidize different macronutrients to fuel metamorphosis, we labeled diets with 13C-tracers. Preliminary results show stressed larvae are smaller (p > 0.01) and consume less oxygen (p >0.01). Infected larvae consume much less oxygen (p > 0.01) and pre-infection oxygen consumption predicts day of death following ranavirus exposure. (R2 = 0.53, p = 0.02). These results indicate a metabolic cost for accelerated metamorphosis, as the oxygen consumption of stressed larvae did not decrease congruent to their mass. Furthermore, severe hepatitis and liver failure, caused by ranavirus, may deprive larvae of energy and nutrients, leading to earlier deaths of individuals with higher metabolisms.
