Non-oblique myofilament arrangement in the dorsal muscle of Sabellastarte magnifica.

Abstract

As described in other invertebrate muscles, most thick myofilaments of the dorsal longitudinal muscle of Sabellastarte magnifica appear to be obliquely arranged with respect to the longitudinal axis of the myofibrils. Some sections, however, show long bundles of myofilaments parallel to the longitudinal axis of the myofibrils. Since the oblique striation concept cannot account for such images, a different (longitudinal) arrangement is proposed for Sabellastarte which can account for all observed images. A wax and threads model built according to this arrangement has been used to demonstrate that by oblique sectioning the longitudinal model can generate a false appearance of filament obliquity.