Meeting Abstract

56.1  Jan. 6  Swimming posture switches from visual to vestibular control in developing larval southern flounder SCHREIBER, A.M.; Carnegie Institution, Embryology schreiber@ciwemb.edu

Flatfish transform from symmetric, upright-swimming larvae into asymmetric juveniles that swim on one side. Lateralized posture develops independent of eye position during metamorphosis, suggesting strong vestibular, as opposed to visual, involvement. This study used infrared videography to address visual and vestibular roles in larval swimming by measuring posture in light versus dark. Pre-metamorphic larvae (5-15 dph) in the dark swam to the surface and descended passively, head first with the body perpendicular to the bottom. Laterality was first observed during passive descent at 20 dph by inclination of the left side upwards. Left side bias continued with development, and by late pre-metamorphosis (23 dph) larvae were parallel to the ground during passive descent, like juveniles. By contrast, in the light pre-metamorphic through early-climax larvae switched from the passive descent posture to upright when feeding or actively swimming. After severing either left or right optic nerves larvae starting eye migration still swam upright in the light, suggesting each eye is capable of controlling posture. After early-climax, fish swam only on one side in both light and dark. These findings suggest alteration in larval swim posture is a continuous integration of visual and vestibular signaling, ultimately ending with vestibular control in juveniles.