Meeting Abstract
Developmental stressors have been classically seen as maladaptive. However, at a certain magnitude and duration, such stressors can result in adaptive phenotypic adjustments, allowing the organism to maintain fitness in an otherwise unfavorable future environment. Without such adjustments, animals face a trade-off between self-maintenance and reproduction. This resource trade-off may come at the expense of sexually selected traits, which can serve as an honest indicator of condition. These traits are common in birds, with red ornaments getting their pigment through carotenoids, which are also thought by some to play a part in oxidative physiology. In zebra finches (Taeniopygia guttata), females prefer males with redder beaks; and redder beaks are also positively correlated with immune function, survival, and reproductive success. We tested the hypothesis that male zebra finches exposed to a prolonged mild heat stressor early in life will be better able to cope with a high heat stressor as adults, allowing them to maintain a sexually selected trait and oxidative status. To do this, we exposed juvenile male zebra finches to a prolonged mild heat stress (38° C) or control (22° C) temperature over a period of 28 days. As adults, the birds were then exposed to either a high heat stressor (42° C) or control temperature for 3 consecutive days. Bill color was measured before and after the adult treatment using digital photographs, from which values for hue, saturation, and brightness were quantified. Following the final treatment bout, birds were euthanized and organs removed. Using Western blots we quantified antioxidant enzyme levels [superoxide dismutase (SOD-1 and SOD-2)] and oxidative damage (4-hydroxynonenal). The results will be discussed in relation to mechanisms of adaptive plasticity and resource trade-offs.
