P3.164 Friday, Jan. 6 The effects of shifting population dynamics on behavior and the expression of secondary sex characteristics in Pimephales promelas SCHROER, M.L.*; PETERS, M.; HEALY, F.L.; PETERSEN, J.N.; PROPPER, C.R.; Northern Arizona University; Northern Arizona University; Northern Arizona University; Northern Arizona University; Northern Arizona University MelanieSchroer@nau.edu
Population dynamics and sex ratios can be strong parameters dictating behavioral interactions among individuals. In order to determine how shifting sex ratios impacts behavior of both sexes, we observed the common fish species, the fathead minnow (Pimephales promelas), in three male:female sex ratios (one:two, two:two, and five:two). In tanks with more males, we observed a significant increase in time males spent under nest substrates (p=0.005) and displaying nest-tending behaviors (p=0.027). Furthermore, males displayed more aggressive behavior towards other males when there were more males in the tank (p=0.017, 0.004), but behavior towards females did not change in response to population dynamics (p=0.39, 0.49). Finally, in tanks with higher male sex ratios, nest-holding males displayed more pronounced secondary sex characteristics such as the number and size of tubercles (p=0.0002, 0.001 respectively), darker vertical banding (p<0.0001), and darker dorsal and pectoral fin coloration (p<0.0001 and p=0.008 respectively) than non-nest holding males. Our findings increase our understanding of the complex interactions that arise from shifting sex ratios. Furthermore, as fathead minnows are a model species for environmental pollution exposure, our results may be important in the development of behavioral bioassays for environmental disruption including the effects of pollution and climate change on population dynamic- mediated processes.