© 1987 by The Society for Integrative and Comparative Biology
Muscle Fiber Types in Crabs: Studies on Single Identified Muscle Fibers1
Fakultät für Biologie, Universität Konstanz Postfach 5560, D-7750 Konstanz, Federal Republic of Germany Stazione Zoologica Naples, Italy
SYNOPSIS. Based on electrophysiological and histochemical data, four types of muscle fibers (types I, II, III and IV) can be identified in the closer of the crab Eriphia. Although characteristics used for typing vary among the fibers of a particular type, the combination of several parameters permits an assignment. Of particular significance for typing is the myosin ATPase activity and its stability after preincubation at different pH levels. The fiber types defined for the closer muscle can also be found in the other leg muscles of riphia.
Single, electrophysiologically identified fibers of each type were quantitatively analyzed for several key enzymes of oxidative and glycolytic energy metabolism (GAPDH, LDH, CS, IDH, HAD). Despite the variations found, different metabolic types can be defined. The typing derived from biochemical studies correlates well with that obtained electrophysiologically and histochemically. The variability of the biochemical properties, however, seems to be considerably larger.
The type I fibers can be regarded as slow oxidative, the type II and III fibers as fast oxidative glycolytic, and the type IV fibers as fast glycolytic.