Functional significance of intermediate filament meshwork in annelid helical muscles.

A desmin-like protein of mol wt 54 kDa was identified in the body wall muscles of some Polychaeta, Oligochaeta, and Hirudinea utilizing SDS-PAGE followed by blot and screening with a vertebrate anti-desmin antibody. The pattern in immunofluorescence is compared to electron micrographs where several bundles of filamentous structures are clearly identifiable. These bundles are unevenly arranged in round or flattened circomyarian fibers and sometimes clearly connect Z elements with hemidesmosomes. The mechanism of intermediate filaments as a functional integration in muscle fibers is analyzed and a possible role as a block to superelongation typical of helical muscles is discussed.