ROLE OF THE FLUID-FILLED BALANCE ORGANS IN THE INDUCTION OF PHASE AND GAIN IN THE COMPENSATORY EYE REFLEX OF THE CRAB SCYLLA-SERRATA

1. Blinded crabs were oscillated about their vertical axis and the eye reflex induced by the fluid-filled statocysts was studied. 2. The phase and gain of the eye movements induced by the eye reflex are affected by the frequency (Fig. 2) and amplitude (Fig. 3) of oscillation and by the pitch position (Figs. 4 and 5) in which the animal is oscillated. Phase lock (eye position in phase to angular acceleration of the body) and a maximal gain (×1) occur when the animal is oscillated in its natural position (20-40‡ head up) at an amplitude of 12.5‡ and a frequency of 0.7 Hz. 3. The movements of the thread hairs relevant for the eye reflex were measured in the isolated but intact statocyst. At oscillations which produce phase lock in the intact animal the position of the hairs is in phase to angular acceleration of the body (Fig. 6). 4. The changes in phase and gain of the eye reflex in the crab which are induced by changes in the frequency and amplitude of oscillation are essentially similar to those obtained in vertebrates. Therefore, it is concluded that the hydrodynamics of the statocyst of the crab resemble that of the vertebrate labyrinth. 5. The changes in phase and gain of the eye reflex induced by positional changes of the crab during the oscillation are explained by gravity affecting the position of the sensory hairs and thereby the properties of their receptors. © 1979 Springer-Verlag.