Optomotor response of Anableps anableps depends on the field of view

Anableps anableps (Cyprinodontiformes) inhabits the niche at the water surface such that its cornea is bisected by the water surface. Consequently, its visual field encompasses simultaneous views into air and water by ventral and dorsal retina, respectively. The optomotor response (OPM) of Anableps was elicited by a moving stimulus pattern in either one or the other environment. Using four related visual displays, we found that this fish exhibits a classical OPM response when presented with suprathreshold flow-fields in its aerial visual field. It lacks an OPM response to the same flow-field when presented in its aquatic visual field, although it may respond by exhibiting optokinetic nystagmus (OKN) and non-OPM motor activity. We conclude that the neurological circuit for the teleost OPM in Anableps operates only for the aerial view and is probably connected to only the ventral retina.