Meeting Abstract
Reproductive success requires that individuals acquire sufficient energy resources. Altering energy homeostasis through restricting food availability or increasing energy expenditure (e.g., locomotion, thermoregulation) inhibits reproductive development in multiple avian species, but the nature of the energy-related signal mediating this effect is unclear. To investigate this question, we examined reproductive and metabolic physiology in male House finches under 1) moderate food restriction (FR), and 2) heat stress (HS), in which birds were we exposed to a high ambient temperature cycle (85-100°F) compared to a control group (70-85°F). We hypothesized that either FR or HS inhibits reproductive development through lowering available metabolic fuel, specifically plasma glucose (GLU) and free fatty acids (FFA). Following FR for 4 weeks, finches lost body mass and experienced a 90% reduction in testis mass compared to ad libitum-fed birds. Plasma GLU was unaffected by food availability. Plasma FFA, however, were higher after 3 days of FR, potentially indicating increased FFA utilization. In a separate group of finches, 4 weeks of exposure to HS resulted in reduced body mass and voluntary food consumption, as compared to control birds. Testis mass decreased by 70% in HS birds, but this treatment did not influence plasma GLU or FFA. These studies are among the first to highlight the potential role of metabolic fuel in mediating inhibitory effects of FR on the reproductive system and to demonstrate a negative effect of HS on reproductive development in a wild bird. Further studies are needed to clarify the role of metabolic mediators and their involvement under different conditions of energy availability and demand.
