Eye Movements of the Dogfish Squalus Acanthi As L

Abstract

A method for recording the positions of the eyes of a free-swimming dogfish is described. The eyes of the dogfish do not compensate completely for the lateral swinging of the head which occurs during swimming. The labyrinthine apparatus and the extraocular musculature are capable of providing complete compensation, but this compensation is opposed by influences from the spinal cord. Full compensation during swimming would stabilize only objects at infinity. Partial compensation serves to stabilize a plane of reference close to the fish. Eye movements, allied with the normal zig-zag progression of the fish, serve to eliminate the blind area behind the fish. Other movements of the dogfish’s eyes are discussed, and arranged in five categories. Spontaneous movements of the eyes of resting dogfish are described, and related to the eye movements of swimming dogfish. The spontaneous movements are suggested to be manifestations of an otherwise subliminal central excitatory state affecting turning and swimming.