The rigidity of fish and patterns of lateral line stimulation

Abstract

Various functions have been attributed to the lateral line organs of fish (and amphibia), including those of detecting touch and sound (both near- and far-field) and flow past a swimming fish^1–4. As the lives of fish and the structures of their lateral lines vary greatly, lateral line function almost certainly varies between species and is probably not simple even for one animal. It is, however, generally agreed that lateral line neuromasts are excited by liquid within the canal moving relative to the canal walls^4–6. For the sprat, such movements are proportional to local differences in motion between the fish and the surrounding seawater⁷ and a similar situation must exist for other fish. Here we describe the motions of fish and seawater at various positions around vibrating sources. We show that fish are rigid longitudinally, and thus local differential movements between fish and seawater occur. Predictions based on these results suggest that when a fish is close to a source of vibration, for example, to a neighbouring fish, the amplitudes, signs and patterns of stimulation along the lateral line system change in a striking way with the position of the fish relative to the source.