Three-dimensional reconstruction of the F-actin musculature of Dorvillea kastjani (Dorvilleidae, Polychaeta) by means of phalloidin-labelling and cLSM

Abstract

This paper is part of a series investigating the muscular architecture of various “Polychaeta”, aiming to ascertain the presence of circular muscles in the body wall, which have recently been thought to be lacking more often than hitherto known. The F-actin muscular subset of Dorvillea kastjani was labelled with phalloidin and the architecture three-dimensionally reconstructed by means of confocal laser scanning microscopy. Three pairs of longitudinal, two transverse and numerous radial muscles ensure shape and flexibility of the prostomium. Mobility of the sub-biramous parapodia and their chaetae is achieved by seven different muscle types. The body wall contains transverse and bracing muscles and in total five longitudinal muscle strands: two dorsolateral, two ventral and one ventromedial. Numerous transverse fibres extend from the dorsal side peripherally and ventrally and become concentrated into six or seven pairs of bundles per segment on the ventral side. They terminate before reaching the midline, leaving a gap of only a few micrometres between them. Within the intersegmental furrows these fibres form complete rings in a supralongitudinal postion. Thus, true circular fibres exist in D. kastjani but are weakly developed.

Keywords

• annelida
• body wall
• muscle system
• evolution