Hydrodynamic stimuli and the fish lateral line

Sensory systems need to distinguish biologically relevant stimuli from background noise. Here we investigate how the lateral-line mechanosensory system of the fish senses minute water motions in the vicinity while exposed to running water. We find that one class of receptor in the lateral line, the canal neuromasts, can respond to hydrodynamic stimuli even in the presence of unidirectional water flow, whereas superficial neuromasts, which predominate in still-water fish, cannot.