Meeting Abstract
125.2 Tuesday, Jan. 7 14:15 Functional significance of hormonal plasticity in house sparrows LENDVAI, AZ*; OUYANG, JQ; SCHOENLE, LA; FASANELLO, VJ; HAUSSMANN, MF; MOORE, IT; BONIER, F; Virginia Tech; Virginia Tech; Virginia Tech; Bucknell Univ; Bucknell Univ; Virginia Tech; Queen’s Univ lendvai@vt.edu
Hormone concentrations are among the most labile of phenotypic traits. Plasticity in levels of corticosterone (cort), the main avian stress hormone, provides a mechanism for individuals to rapidly respond to environmental change. However, the functional effects of such plasticity are unknown. We studied individual differences in cort levels under varying conditions to test whether there are consistent individual differences in (1) baseline cort levels; (2) responsiveness (plasticity) to an ecologically relevant stressor (food restriction); and (3) whether individual differences in plasticity are related to immune function and the overall oxidative damage experienced by individuals. We took 25 wild-caught house sparrows, Passer domesticus, into captivity and randomly assigned them to a food restricted or control treatment (60% and 110% of their daily food consumption, respectively) for one week. We controlled for order effects by alternating the treatments for four consecutive weeks, such that each individual experienced food restricted and control diets twice. At the end of each week, we recorded the body mass of the birds and took blood samples within 3 minutes for hormone and oxidative stress analysis. We found that during food restriction, birds lost mass and had higher cort levels compared to control treatments. Birds showed significant individual variation in baseline cort levels and stress responsiveness, even after controlling for changes in body mass. However, these individual differences in hormonal plasticity were not related to wound-healing capacity (a measure of immune function) or plasma oxidative damage. Therefore, despite individual differences in stress responsiveness, the adaptive significance of this variation is unclear.
