Meeting Abstract
The plainfin midshipman fish (Porichthys notatus) is an established neuroethological model for investigating mechanisms of acoustic communication because the reproductive success of this species is dependent on the production and reception of social acoustic signals. Midshipman possess three otolithic end organs capable of sound detection. The largest of these is the saccule and the sensitivity of this hearing end organ is well established, but the sensitivity and function of the putative auditory lagena is less understood. Previously, we showed that the midshipman lagena had a similar low-frequency sensitivity to that of the saccule but the lagenar thresholds were much higher. Furthermore, work from our lab demonstrated that midshipman possess sexually dimorphic swim bladders that effectively enhance sound pressure detection. The swim bladders of females have rostral horn-like extensions that project close to the inner ear end organs, especially the lagena, while nesting males lack such extensions. The aim of this study was to determine whether these swim bladder extensions enhance auditory lagenar sensitivity to sound pressure and higher frequencies. We characterized the lagenar sensitivity of reproductive females with intact (control) and removed swim bladders. Our results show that control females with intact swim bladders displayed auditory evoked lagenar potentials up to 1005 Hz while females with removed swim bladders displayed evoked potentials only up to 505 Hz. Furthermore, the control females had the lowest thresholds (highest sound pressure sensitivity), with average thresholds at the characteristic frequency (85 Hz) that were 6 dB lower than those without swim bladders. These findings suggest that the midshipman lagena is sensitive to sound pressure indirectly and maybe important for the detection of social acoustic signals.
