Some Observations on the Forces Acting on Neuromasts in Fish Lateral Line Canals

Abstract

There are good reasons for measuring stimuli to lateral-line systems as pressure gradients (Denton and Gray 1988), the most likely useful natural stimuli to lateral line sense organs being local pressure gradients produced by a fish’s own swimming movements and local pressure gradients produced by external sources. In what follows we shall assume that (1) the effective stimulus for a canal neuromast will be one that produces a movement of the cupula relative to the wall of the canal, (2) the force moving the cupula must be transmitted to the cupula through the liquid that the canal contains, and (3) displacements of such liquid and the cupula of the neuromast will arise from net pressure gradients along the short stretch of canal carrying the neuromast. This net gradient can be measured in terms of the local accelerations of the medium adjacent to the canal relative to the surface of the fish (Denton and Gray 1983). It follows that if the medium adjacent to the lateral line moves in exactly the same way as the surface of the fish that carries a particular “section” of lateral line, the neuromast in this section will not be stimulated. When considering an external source, the stimuli to lateral lines will often be proportional to the accelerations of the sonic surface (Gray 1984; Kalmijn 1988, Chapter 9)