| Abstract | Several studies have shown that males and females differ with regard to their ability to survive pathogen infections. However, fewer studies have compared male and female immune responses following pathogen exposure. The purpose of this study was to examine sex-based differences in pathogen resistance and immune responses following exposure to a pathogen in adult fathead minnows (Pimephales promelas). To accomplish this, male and female fathead minnows were injected with Yersinia ruckeri, a pathogen known to cause enteric red mouth disease, and their responses were measured at multiple levels of biological organization. Results showed that at the whole organism level, male fish were less able to survive pathogen infection relative to female fish. At the tissue level, pathogen-injected fish experienced significant decreases in hematocrit relative to sham-injected fish; however, males and females did not differ from one another. At the molecular level, several genes were found to be significantly upregulated in response to pathogen-injection. Of these upregulated genes, significant differences in expression due to sex were noted in interleukin 1-beta and complement components 3 and 4. Taken together, this evidence confirms differences in male and female immune function and provides molecular level data that may help explain sex-specific differences in pathogen resistance. |
