Ontogeny of auditory saccular tuning in the plainfin midshipman fish, Porichthys notatus.

Abstract

Sensory systems are important throughout an animal’s life history, allowing it to detect and respond to biologically relevant stimuli important for survival and reproduction. The auditory system of the plainfin midshipman fish (Porichthys notatus) plays an important sensory receiving role for encoding vocal‐acoustic communication signals produced by adults, but the response properties and function of this receiver system during ontogeny are less understood. Here, we examine the response properties of evoked saccular potentials in two size classes of juveniles [small = 1.9–3.0 cm standard length (SL) and large = 5.0–8.0 cm SL] and in nonreproductive adults (> 9.0 cm SL) to determine the auditory sensitivity of saccular hair cells during ontogeny. Saccular potentials, maximally evoked at twice the stimulus frequency, were recorded in vivo using a lock‐in amplifier while playing pure tone stimuli via an underwater speaker. Results indicate an ontogenetic retention of saccular tuning sensitivity with size/age with peak sensitivity ranging from 75 Hz (lowest frequency tested) to 185 Hz. In addition, maximum detectable frequency of the saccule also increased with size/age. These results suggest that the midshipman saccule is best suited to detect low frequency components (< 105 Hz) of conspecific vocalizations throughout ontogeny.