Electrophysiology of the Cephalic Lateral Line of the Surface-Feeding Fish Aplocheilus lineatus

Abstract

We investigated the responses of primary afferents innervating the cephalic lateral line of the surface-feeding fish Aplocheilus lineatus to sinusoidal surface wave stimuli. All afferents showed ongoing activity. The degree of spike synchronization with the excitatory phase of a wave cycle and/or the firing rate encoded stimulus amplitude. Modulation of the fiber's discharge rate usually reflected the waves' frequency and thus may be used by the fish to determine stimulus frequency. Different primary afferents may show differences in vibration threshold, frequency sensitivity, phase coupling and dynamic amplitude range. Fibers innervating different head neuromasts were, however, not consistently different in their average response properties. Therefore, we conclude that the arrangement of the cephalic lateral line of A. lineatus separates the relevant stimulus parameters into distinct channels to only a limited extent, leaving most of the stimulus analysis for central processing, and that surface feeding does not involve obvious specializations of the peripheral lateral line, compared with midwater fish and surface-feeding amphibians.