Influence of single neuromasts on prey localizing behavior of the surface feeding fish,Aplocheilus lineatus

Abstract

The orienting behavior ofAplocheilus lineatus with intact, partially and totally ablated neuromasts to single surface wave trains was investigated. 1. Blinded fish with intact lateral line system localize the direction and the distance of a wave source within the tested range of 18 cm. 2. With only one neuromast left intact the fish remain sensitive to surface waves from all directions although their ability to locate the stimulus direction is now absent. The observed turning responses depend solely on the topographic position of the neuromast: A rostral position results in a small turn, a caudal one in a large turn. 3. Distance localization of such fish as indicated by the magnitude of forward movement during an evoked response still exists and is only somewhat reduced. It is independent of target angle. 4. Complete unilateral ablation of neuromasts results in at least a partially misinterpretation of target angles. Stimuli approaching the intact body side cause well differentiated responses, whereas those impinging first upon the side depleted from neuromasts cause turns directed away from the wave source. 5. Fish without any neuromasts react to surface waves roughly directed. Their reaction time is extraordinarily prolonged, the responsiveness extremely reduced; no distance localization at all can be observed. We therefore conclude, that this type of reaction is mediated by receptors different from neuromasts and not intermingled with the neuromast mediated ones. 6. The functional significance of a “place effect” of individual neuromasts on the mechanism of orienting behavior is discussed.