Restructuring of the Optokinetic Reflex during Metamorphosis in Pelobates fuscus Laur.

The restructuring of the gaze stabilization system in Pelobates fuscus was investigated by quantitative analysis of the optomotor response using video imaging. Gaze stabilization is an important component in the system of neural mechanisms of visual depth perception. It was shown that the optomotor response in aquatic tadpoles of P. fuscus is similar to that of fish (movement of the animal in the direction of the visual background movement and eye nystagmus consisting of a fast and a slow phase). During metamorphosis (transition from the aquatic to the terrestrial lifestyle), froglets of P. fuscus responded to the movement of the visual background by eyes and head movements. One year after metamorphosis, P. fuscus responded to movement of the visual background as adult Anura: only by head movements (a slow and a fast phase), while eye movements were absent. Possible causes of the loss of active eye movements by Anura amphibians in the process of evolution are discussed.