Meeting Abstract

P3.200  Monday, Jan. 6 15:30  Changes in androgen receptor expression in a brain region controlling communication behavior across populations of black ghost knifefish (Apteronotus albifrons) HO, WH*; SMTIH, GT; Indiana University, Bloomington; Indiana University, Bloomington wwho@indiana.edu

Rapid evolutionary shifts in the magnitude and direction of sexual dimorphism of behavior can result from changes in responsiveness of behavior to gonadal steroids. In the South American ghost knifefish (Apteronotidae), evolutionary shifts in the sexual dimorphism of electrocommunication behavior are accompanied by changes in androgen sensitivity across species and populations. In this study, we tested the hypothesis that variation in sexual dimorphism and androgen sensitivity in the black ghost knifefish (Apteronotus albifrons) is mediated by changes in the expression of androgen receptors (AR) in the brain. Black ghosts communicate using weak electric signals (electric organ discharges, EODs) fired at a characteristic frequency (EODf). The magnitude of sexual dimorphism in EODf varies across populations and is correlated with changes in the sensitivity of EODf to the main fish androgen, 11-ketotestosterone (Ho et al. 2013). We compared fish from populations that were either strongly or weakly sexually dimorphic in EODf and used qPCR to quantify the relative expression of AR mRNA transcript in a region of the brain responsible for setting EODf, the pacemaker nucleus (Pn). AR mRNA expression was also quantified in the gonads. We found that AR abundance in the Pn was significantly higher in fish from the strongly sexually dimorphic populations than in the less sexually dimorphic population. Our data show that changes in AR abundance within specific brain regions can underlie population-level variation in sexually dimorphic behavior.