Free hook hair and thread hair input to fibre 5 in the mud crab,Scylla serrata, during antennule rotation

Abstract

The statocyst input to a large semicircular canal interneuron (fibre 5) in the crabScylla serrata has been investigated by selective ablation and electrical stimulation of the separate branches of the antennulary nerve, and selective destruction of groups of receptors. By oscillating the antennules sinusoidally in the range 0.1 Hz–100 Hz it has been possible to demonstrate an input to fibre 5 from the lower group of contralateral thread hairs, the contralateral free hook hairs and to a lesser extent, the ipsilateral free hook hairs. Free hook hair input is effective only at high frequencies of oscillation (20 Hz–100 Hz) whereas thread hair input is effective over a greater range (0.1 Hz–100 Hz). Fibre 5 exhibits two peaks of sensitivity (1) to oscillations around 7 Hz mediated through contralateral thread hairs and (2) to oscillations around 60 Hz mediated through thread hairs and free hook hairs (Fig. 7).