Seasonal plasticity of saccular sensitivity in the type II sneaker-male plainfin midshipman fish (Porichthys notatus).

Abstract

Acoustic communication is essential to the reproductive success of the nocturnally breeding plainfin midshipman fish (Porichthys notatus). During the summer breeding season, type I singing-males excavate nests in the Pacific intertidal zone and vocalize a multiharmonic “advertisement hum” to attract potential mates. Summer reproductive females are more sensitive to the dominant frequencies that comprise the hum than winter nonreproductive females. Type II or “sneaker” males employ alternative mating strategies that do not require nest construction or hum production but instead involve satellite and/or sneak spawning strategies. These strategies require nocturnal nest selection and localization. Because sneaker-males must rely on their auditory system to find the nests of singing males just as females must, we hypothesized that the saccular sensitivity of the reproductive sneaker-males would be most like that of reproductive females. Here we measured the evoked saccular potentials of reproductive and nonreproductive sneaker-males to tones of various sound pressure levels, and determined saccular thresholds for frequencies from 65 to 505 Hz. As predicted, thresholds measured in reproductive sneaker-males very closely matched those reported for reproductive females. Future studies will investigate the effects of gonadal steroids on hearing in sneaker-male midshipman fish. [Work supported by NIH NIDCD Grant No. 2T32DC005361-06.]