The Effect of Load on Locomotion in Crayfish

Leg movements and leg muscle activity were monitored in unrestrained crayfish walking freely under several different load conditions. A variety of changes in the character of locomotion was found to vary with load including: (1) the timing and frequency of the step cycle and in particular the power stroke duration; (2) significant leg-positional changes which result in increased mechanical advantage under load; and (3) the (load-induced) recruitment of the depressor muscle. In restrained, immobile animals, isometric loading of depression resulted in inhibition of motor activity in the depressor-remotor nerve, an effect similar to the vertebrate tendon reflex.