Musculature within the segmented trunk region of Echinoderes horni . Confocal z-stack projections of phalloidin staining (muscle) and autofluorescence (cuticle) in a single specimen. Lateral views with anterior to the top and ventral to the right side. (A-B) maximum z-stack projections of muscle in grayscale (A) and red (B). (C) z-stack of optical slices on the right side of the medial plane. (D) z-stack of optical slices through the medial plane at the level of the pharynx. Ventral, dorsal, dorsoventral and diagonal muscles are segmented. Continuous fibers span multiple segments on dorsal and ventrolateral sides of the trunk, and within the trunk as pharynx retractors. Abbreviations: dim, diagonal muscles; dm, dorsal muscles; dvm, dorsoventral muscles; ir, introvert retractors; lcf, longitudinal continuous fibers; ncm, neck circular muscle; prm, pharynx retractor muscle; vm, ventral muscles. Scale bar, μm.