Androgen-induced changes in the response dynamics of ampullary electrosensory primary afferent neurons

Male stingrays use their ampullary electroreceptors to locate mates, but th e effect of gonadal androgens on electrosensory encoding during the reprodu ctive season is unknown. We tested the hypothesis that gonadal androgens in duce neurophysiological changes in the electrosense of male Atlantic stingr ays. During the primary androgen increase in wild males, the electrosensory primary afferent neurons show an increase in discharge regularity, a downs hift in best frequency (BF) and bandpass, and a greater sensitivity to low- frequency stimuli from 0.01 to 4 Hz. Experimental implants of dihydrotestos terone in male stingrays induced a similar lowered BF and bandpass and incr eased average neural sensitivity to low-frequency stimuli (0.5-2 Hz) by a f actor of 1.5. Primary afferents from long ampullary canals (>3 cm) were mor e sensitive and had a lower bandpass and BF than did afferents from short c anals (<2 cm). We propose that these androgen-induced changes in the freque ncy response properties of electrosensory afferents enhance mate detection by male stingrays and may ultimately increase the number of male reproducti ve encounters with females. Furthermore, differences in primary afferent se nsitivity among short and long canals may facilitate detection, orientation , and localization of conspecifics during social interactions.