Physiology of lateral-line mechanoreceptors in a teleost with highly branched, multiple lateral lines.

The physiological aspects of the lateral line of Xiphister atropurpureus--a teleost with multiple, highly branched lateral-line canals on each body side--were investigated. In terms of sensitivity and frequency response, the lateral line of Xiphister is similar to simple, unbranched lateral-line canals. For both the dorsal and the medial trunk canal the lowest displacement threshold is in the frequency range of 100-150 Hz. Within this range, a peak-to-peak displacement of 0.2-1.0 microns is sufficient to evoke a neural response. For the stimuli applied, both the dorsal and the medial lateral-line canals had well-defined, but largely overlapping, receptive fields. A comparison of the experimental results with theoretical calculations showed that the trunk lateral line of Xiphister responds in proportion to the sum of the radial and angular water displacement components caused by a vibrating sphere. Our calculations further predict that multiple lateral lines cause a substantial increase in receptive-field size if nearby objects create water displacements that are barely above threshold and/or if a stimulus is masked by background noise.