Overlapping sensory fields ofNereis, and their possible role in locomotion

Abstract

The sensory field of the bipolar cells in the dorsal epithelium of each segment ofNereis virenshas been found to overlap the two segments on either side. Dorsally its boundary is indicated by the dorsal blood vessel and the ventral limit coincides with the division between the notopodium and neuropodium. The bipolar cells along the posterior intersegmental groove on the ventral side of the segment enter the cord in the 4th segmental nerve. Electrophysiological recordings from this nerve reveal a slowly adapting unit which responds to stretching of the longitudinal muscle. This may represent Hamakers ‘C’ fibre. The significance of the overlapping sensory fields is examined in relation to peripheral and central control of the locomotory movements. Hypothetical models based on anatomical data are used to illustrate the possible role of the sensory input in the locomotion of normal worms.