Though most animals sense light in structures specialized for vision, many opsins exist outside the eye. In translucent zebrafish, activation of vertebrate ancient long opsin a (VALopA) within the spinal central pattern generator profoundly inhibits spontaneous neural activity and motor behavior. However, it is not known which specific cells are photosensitive or how the inhibition propagates through the circuit. Here, I propose recording from active pacemakers, interneurons, motor neurons, and precursors in order to better understand the mechanism of action of VALopA. Investigating acute responses to light and changes effected by sustained illumination will be informative for understanding zebrafish behavior and for establishing a new role for a nonvisual opsin in regulating development.