Eyestalk movements in the crayfish, Procambarus clarkii

Abstract 1. 1. Eyestalk movements of the crayfish ( Procambarus clarkii ) were recorded with a capacitative sensing device under various visual conditions. 2. 2. The eyestalk movements were conveniently classified into four types of visually evoked movement (tracking movement, optokinetic nystagmus movement, “on” movement, apparent movement) and four types of spontaneous movement (tremor, drift, saccade, flipback). 3. 3. The amplitude gain of tracking movement evoked by a moving light is primarily related to the velocity and position of light in the eye surface, and it is strongly under the facilitatory influence of animal's excited state. 4. 4. The direction and amplitude of “on” movement evoked by illumination with a stationary light depend on the position of light.