Date Thesis Awarded
Honors Thesis -- Open Access
Bachelors of Science (BS)
Paul D. Heideman
Julian T. Pittman
During the short photoperiod of winter, some short-lived rodents repress reproduction and other non-essential functions, while others continue to reproduce. The capacity to reproduce during short photoperiod or to repress reproduction is genetically variable, signaling a potential microevolutionary life history tradeoff. Previous results linked this variation to the location and abundance of immunoreactive (IR) gonadotropin releasing hormone (GnRH) neurons in male white-footed mice (Peromyscus leucopus). Independently, previous results also found differences in food intake in males linked to genetic variation in the same population. In this study we tested for the relationship between food intake and the number of IR-GnRH neurons in females. The experiment used three selected lines of P. leucopus derived from a wild population. The three lines were, respectively, reproductively inhibited in short photoperiod (R line), reproductive in short photoperiod and therefore non-responsive to photoperiod (NR), and a control line not deliberately under selection. We performed immunostaining and counted the number of IR-GnRH neurons in one anterior and three preoptic brain sections. We tested for variation in the number of GnRH neurons in female P. leucopus and compared food intake, reproductive development and the interaction of all three. We found a significant difference in food intake among lines, with the NR mice eating 20 percent more than the R mice. The difference in food intake is consistent with a microevolutionary life history tradeoff, similar to previous findings in males, but smaller in magnitude. There was no significant difference in the number of IR-GnRH neurons among lines. There was no correlation between the number of IR-GnRH neurons and the other measures. This suggests either a need for additional testing for females or that there is an actual difference in the number of IR-GnRH neurons between males and females.
Mahoney, Tara Penny Florina, "Genetic Variation in Food Intake and GnRH Neurons in Female White-footed Mice (Peromyscus leucopus)" (2009). Undergraduate Honors Theses. Paper 238.
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