A histochemical and ultrastructural profile of a primary locomotor muscle in the common blue crab

Abstract

Crustacean muscle fibers are diverse in physiological and morphological characteristics such as contraction speed, sarcomere length, actin to myosin filament ratio, and dependence on oxidative or glycolytic metabolism. The goal of this laboratory is to examine the fiber populations in similar muscles of several species of crab to determine if varying degrees of locomotor capabilities (i.e., walking versus running, fatigue resistance, etc.) are related to fiber type diversity. The common blue crab, Callinectes sapidus, which is able to move rapidly over land and in water and migrate over long distances, is among the first crabs included in our study. The fiber heterogeneity of the depressor muscle, a primary locomotor muscle of the third pereopod of the blue crab, was examined. Fiber typing was based on histochemical studies of myofibrillar actomyosin ATPase activity, an enzyme correlated with maximum shortening velocity. Histochemical detection of the mitochondrial enzyme succinic dehydrogenase (SDH) was used to differentiate oxidative from non-oxidative fibers.