Meeting Abstract
Plainfin midshipman fish (Porichthys notatus) are a marine teleost species that relies on the production and reception of acoustic communication signals for mating, and therefore development of the auditory system is important for survival and reproduction. Previously, free swimming juvenile and nest attached larval midshipman were found to behaviorally startle in response to acoustic pure tones, indicating functional auditory and/or lateral line systems at these stages. Also, inner ear physiology studies show that juveniles and sexually mature adult midshipman have similar peripheral auditory sensitivity to frequencies contained in midshipman acoustic signals, with adult hair cells being more sensitive at higher frequencies than juveniles. However, it is unclear whether inner ear hair cell density changes during ontogeny from larvae to sexually mature adults and whether changes in inner ear hair cell density play a role in ontogenetic changes in midshipman hearing sensitivity. We quantified hair cell density by staining hair cell stereocilia bundles with fluorescently labeled phalloidin in larval, juvenile, and adult midshipman saccules, the primary auditory end organ in most fishes. We found that saccular hair cell density decreases from larvae to adults but the estimated total number of hair cells increase as a function of fish size and saccule macula area. The adaptive significance of early development of the auditory system is discussed.
