An electron microscope study of sarcotubules and related structures in the leech muscle

Abstract

Longitudinal body muscles from five leech species have been examined in the electron microscope. The contractile cortex contains many sectors of myofilaments, separated by sarcotubules, and encloses the sarcoplasmic core that lodges the nucleus, the mitochondria, and several membranous formations. A single row of vesicles are lined up under the sarcolemma. The sarcotubules are fairly straight elements with an extension mainly in the radial direction. There are two types of sarcotubules that alternate in a regular fashion; they have been called compact and hollow sarcotubules, respectively. The total number of sarcotubules in a cell may be in the order of 500,000. The hollow sarcotubules show similarities to the transverse sarcotubules of striated muscles with respect to their reactions toward some impregnating substances, their location, and their fine morphology. It is proposed that these sarcotubules are responsible for the conduction of the contraction stimulus. The sarcotubular systems of the leech muscle apparently lacks of longitudinal portion.