Relationship between calling behavior, immunity and plasmatic levels of corticosterone and testosterone in bufonids from Caatinga

Abstract

According to the model of parasite-mediated sexual selection, females of different species tend to select males that exhibit exaggerated secondary sex traits, which might indicate male's heritable quality on parasite resistance. Gonadal and interrenal steroid hormones might mediate the relationship between signal intensity and parasite intensity, since they are responsible for the development of secondary sexual characters, sexual behavior and energy stores mobilization during the reproductive activity, and are also involved on immunomodulation. In anuran amphibians, intra and interspecific positive correlations can be observed between the calling rate and plasma levels of steroid hormones (testosterone and corticosterone), and recent data for some species show a negative relationship of calling rate with parasite burden and induced immune response. Nevertheless, species characterized by different reproductive patterns may show distinct plasma levels of steroid hormones during the reproductive period, and consequently, differences in immunocompetence. Therefore, the proposal of this study is to investigate the relationship between reproductive behavior (calling behavior and chorus density); immunocompetence (plasma antimicrobial capacity and subcutaneous inflammatory response to phytohemagglutinin challenge) and plasma levels of testosterone and corticosterone of two toad species from Brazilian semi-arid (Caatinga) that present different reproductive patterns (Rhinella granulosa e R. jimi).