Meeting Abstract
The insular population of introduced brown tree snakes (Boiga irregularis) on Guam have largely depleted the native vertebrate fauna, yet continue to exist at relatively high densities. Under such conditions of stress, secretion of the glucocorticoid hormones may be altered, which can subsequently affect fitness. This well-studied population of snakes provides an avenue for long-term evaluation of glucocorticoid responses, and an opportunity to examine functional aspects of changes in corticosterone ( CORT ), such as innate immunity. In April 2018 we captured 37 brown tree snakes and collected baseline blood samples in under 7 minutes. Snakes were placed in cloth bags for one hour to induce an acute stress response and resampled. All blood was immediately centrifuged, serum separated, and flash-frozen in liquid nitrogen vapor phase, then transferred to a freezer at -80 C on return to the mainland. Bacterial-killing ability was assessed within 1 month of collection. We assessed percent killing ability of plasma incubated with E. coli and compared it to growth of E. coli in a positive control via spectophotometry. CORT concentration was assessed via enzyme immunoassay with a commercially-available kit. We evaluate the hypothesis that glucocorticoid hormone levels are altered over time in populations with depleted resources and overpopulation by comparing our data to data collected 15 and 25 years prior. Additionally, we examine the functional response of the complement pathway of the innate immune system via bacterial-killing ability of plasma as it relates to baseline and acutely-stressed CORT levels.
