Single unit sensory activity in free walking crabs: force sensitive mechanoreceptors of the dactyl.

Activities of individual, force-sensitive mechanoreceptors (funnel canal organs) of the terminal segment (dactyl) of the crab leg have been recorded in freely moving animals. During the stance phase of walking receptors discharge in regular bursts that are closely correlated with activity of the opener muscle of the propodite when the leg is used on the trailing side in lateral locomotion. Individual funnel canal organs also show sustained discharges to imposed cuticular strains and strains resulting from resisted muscle contractions. These receptors thus can monitor both internal and external forces that are applied to the leg in locomotion.