Morphological and physiological measures of trophic dependence in a crustacean muscle

Abstract

Tenotomy of crayfish opener muscles, or severing of the opener motor innervation while motor terminals may remain intact (decentralization), produces no change in fiber resting potential or input resistance within 75 to 245 days. Immobilization or “decentralization” of the same muscle mass produces no significant change in fiber diameter within 237 or 172 days, respectively, although some atrophy was noted after “denervation” for 267 days, at which time most severed nerve terminals have probably degenerated. Tenotomization produces a 15–35% shortening of the muscle resting length and leads to a significant decrease in fiber diameter within 15 days. Progressive atrophy following tenotomy is associated with a progressive decrease in fiber resting length. These results suggest that fiber diameter is heavily dependent upon the maintenance of a minimum resting length rather than upon muscle fiber activity (“use”) or upon a neurotrophic substance. Conversely, the maintenance of membrane resting potential and input resistance do not necessarily depend upon neurotrophic substances, muscle activity, or muscle resting length.