Sedentary behavior as a factor in determining lateral line contributions to rheotaxis

Abstract

Abstract Rheotaxis is a robust, multisensory behavior with many potential benefits for fish and other aquatic animals. Visual (optic flow) cues appear to be sufficient for rheotaxis, but other sensory cues can clearly compensate for the loss of vision. The role of various non-visual sensory systems, in particularly the flow-sensing lateral line, is poorly understood-largely due to widely varying methods and sensory conditions for studying rheotaxis. Here, we examine how sedentary behavior under visually deprived conditions affects the relative importance of lateral line cues in two species: one that is normally sedentary (the three-lined corydoras, Corydoras trilineatus) and one that normally swims continuously along the substrate (the blind cavefish, Astyanax mexicanus). No effect of lateral line disruption on rheotactic performance was found in blind cavefish, which were significantly more mobile than three-lined corydoras. By contrast, rheotaxis was significantly impaired at low, but not high, flow speeds in lateral-line deprived corydoras. In addition, lateral line enabled corydoras were characterized by decreased mobility and increased rheotactic performance relative to lateral line deprived fish. Taken together, these results suggest that sedentary behavior is an important factor in promoting reliance on lateral line cues.