Nervous control of walking in the crab,Cardisoma guanhumi

Abstract

1. During lateral walking in the land crab,Cardisoma guanhumi, the leading legs can step at a higher frequency than the trailing legs. 2. The land crab can compensate for applied load by increasing the duration of motor bursts to the powerstroke muscles whereas returnstroke bursts remain fairly constant in duration. Neither the average frequency nor the instantaneous frequency of the motoneuron discharge varies in predictable manner following application of the load. 3. Binding a leg in maximal levation with the distal joints free to move results in a cessation of normal rhythmic motor output to that leg. The rhythmic motor output resumes in the bound leg if the animal is forced to walk against a load. 4. Binding of a leg also causes changes in the relative phase of stepping among the other ipsilateral legs. 5. It is concluded that the walking output to a single leg can be influenced by proprioceptive inputs from that leg as well as by modifications due to proprioceptive inputs from the other walking legs.