Mutant animals exhibit defects in the sensory cilium. Mutants have normal inner segments, an intact rootlet, basal bodies and connecting cilia, However, dramatic defects are seen in the outer segment morphology, in both mechano- and chemosensory chaetae. Mutant animals exhibit reduced mechanoreceptor currents and strongly attenuated chemosensory responses to sucrose. Their transepithelial potentials are normal.