Single unit analysis of mechano- and chemosensitive neurones in the crayfish claw

Discharges from single sensory neurones originating in two different hair structures on the chelae of the crayfish Orconectes limosus were recorded. Mechanosensitive units responded to flow alteration or the deflection of single large setae. Chemosensitive units were activated by fish extract in linear dependence on the logarithm of concentration of the chemoexcitant. Mechano- and chemosensitive units differed with regard to the amplitudes of their action potentials and the time distribution of the impulses in a response. Mechanosensitive units were located in the large setae combined in hair clusters, whereas chemosensitive units were found to be situated in the stout setae lining each biting edge.