Sex and species differences in spinal motor neuron androgen receptor expression in frogs

This study examines the evolution of multimodal signaling behavior through a comparative investigation between sex differences (male and female Staurois parvus) and species differences within three frogs (Staurois parvus, Rana pipiens, and Xenopus laevis). S. parvus is one of the most unique anuran species in the world, since it exhibits a communication signaling behavior known as foot flagging. This visual signal allows the outstretched hindlimb of the frog to attract female mates in the noisy environment in which they live. It is predicted that evolution might have co-opted an existing physiological mechanism in S. parvus, thus regulating the production of this unique foot-flagging behavior. Moreover, foot flagging in S. parvus may have evolved with androgen sensitivity of spinal cord circuits controlling the hindlimb, resulting in S. parvus possessing an increased amount of androgen receptor (AR) expression in lumbar cord motor nuclei populations compared to that of R. pipiens and X. laevis, two species that do not foot-flag. Results from this study indicate that there may be sex differences between male and female S. parvus in AR expression. It is hypothesized that male S. parvus foot-flag to achieve reproductive success through this mating signal, and female S. parvus foot-flag to avoid males in response to environmental pressures. Additionally, qualitative results from this study may show species differences in AR expression between S. parvus, R. pipiens, and X. laevis, specifically in spinal motor nucleus populations nine and ten. Future research should involve developing an image data analysis protocol to accurately quantify AR expression for the sexes and three species being studied