Electron Microscope Studies of Insect Muscle. I. Flight and Coxal Muscle of Hydrophilus Piceus

Abstract

The structure of isolated fibrils of the flight and coxal muscles of H. piceus was observed by the electron microscope in the stretched, partically contracted and fully contracted states. Differences were encountered between 2 types of muscles at both the fibrous and fibrillar levels; differences in tracheation, sarcolemma, presence and absence of lines and in sarcomere lengths. During contraction, in both muscles, the A substance migrates into the I region, and both regions participate in contraction; the A more than the I, however. The insect muscle differs from the vertebrate in that the M line is weak and the N line usually absent. The Z line does not appear to be part of the sarcomere. A discussion is presented relating the color and functions of the 2 muscles to their fibrillar structure. || ABSTRACT AUTHORS: G. A. Edwards