Meeting Abstract
Theoretical models predict that elevated androgen and glucocorticoid plasma levels in vertebrate males during reproductive season should promote immunosuppression. Additionally, some studies also report decreased stress response during this season. Therefore, this study investigated annual variation in plasma corticosterone (CORT) and testosterone (T) levels, as well as plasma bacterial killing ability (BKA), in males of toads (Rhinella icterica) from a natural population, including response to a movement restraint stress on these variables. The predictions were that all traits should vary over the year showing higher hormonal levels during reproductive season and lower BKA, whereas, intensity of response to a stressor should be lower at this season. As predicted, baseline CORT, TESTO and BKA showed higher values during reproductive season. Moreover, baseline CORT was positively correlated with both TESTO and BKA. Therefore, higher androgen and glucocorticoid levels during reproductive season are associated with enhanced immune properties. Despite fluctuation of CORT baseline, post-stress levels remained uniform over the year, indicating that toads reached similar maximum values despite annual scope variations. Otherwise, T decreased in response to restraint before reproductive season but increased in response to this stimulus during and after reproductive season. Meanwhile, BKA decreased due to stressor after reproductive period, which might indicate a relation with large energy investment during reproductive season.
