Proprioceptive Control of Posture in the Crayfish Abdomen*

Sense organs responsive to the changes produced by an animal’s own musculature are common in complex, flexible motor systems, and it is probably safe to assume that proprioceptive feedback is required for these systems to operate with precision. The crustacean muscle receptor organ (MRO) first described by Alexandrowicz (1951) has, because of its accessibility, ease of isolation and hardiness, proven particularly amenable to electrophysiological study. However, the study of this receptor has until recently been confined to mechanisms of transduction and to the excitatory and inhibitory control of its output.