Reaction to surface waves by Xenopus laevis Daudin. Are sensory systems other than the lateral line involved?

The turning response to surface waves of clawed toads (Xenopus laevis) with an inactivated lateral line was reinvestigated to examine whether sensory systems other than the lateral line ("second systems") are involved. Two methods were used to block the lateral line input: selective and reversible inactivation of the lateral line periphery using CoCl2 or chronic destruction with thermocautery. The time-course of the response recovery (response frequency, turning accuracy and reaction time) was recorded. Following CoCl2 inactivation 10 out of 13 animals did not respond to surface waves for at least 2 days. The remaining 3 animals gave sporadic turning responses. It is assumed that in these individuals a "second system" is permanently involved in the detection of surface waves parallel to the lateral line. Five days after the chronic destruction of the lateral line all animals again turned to the centre of surface waves. It is suggested that by this time the "second system" had become capable of substituting for the missing lateral line input. The response frequency and the accuracy of the turning response of lesioned animals varied considerably among individuals but was always lower than in untreated animals (tested up to 120 days).