Fig 4

Adult myoanatomy of Wirenia argentea (Neomeniomorpha). Anterior is to the left in (a), (b), (d), (e), (h) and up in (c), (f). (a), (b), (g), (i) are maximum intensity projections of confocal stacks or confocal stack subsets, respectively. For better visualization of individual muscular elements, the helicoidal muscle layer and the set of outer dorsoventral musculature are omitted and only the ventral or dorsal half of the animal with section plane in the region of the enrolling muscle is shown in (c) and (f), respectively. Major muscle units in schematic representations are indicated by color code. Cross section in (g) was generated by vibratome sectioning. a Lateral view of the anterior region with identical arrangement of longitudinal muscle fibers as in juveniles. The diverging pharyngeal retractor is indicated by the black arrowhead. b Inner muscular organization of the anterior region with vestibular retractor (white arrowhead). c Dorsal muscle system seen from ventral. d Schematic view of muscular elements of the anterior region. Scheme refers to (a) and indicates the anterior-most arrangement of longitudinal muscle fibers and their correlation to the larval longitudinal muscles in (i) and the three-layered body wall musculature in (ii). e Sagittal section of the anterior region and view on inner muscular elements. Scheme refers to (a) and (b). f Ventral muscle system seen from dorsal. (g) Cross section through the ventral body. h Schematic representation of the arrangement of the intermediate helicoidal muscle layer; lateral view. i Detail of a ventral view. j Schematic cross section in the mid-body region. Abbreviations: atrial sense organ (aso); cerebral ganglion (cg); fibers of outer or inner dorsoventral musculature (dvm); helicoidal musculature (hm); longitudinal musculature (lm); mouth (m); pedal groove (pg); pedal pit (pp); muscular pharynx (ph); ring musculature (rm). Scale bars: 50 μm