Fig. 3.

Myoanatomy of early juveniles of Wirenia argentea (Neomeniomorpha). Anterior faces up in (a)-(d), (g), (h). a-c and e-g are maximum intensity projections of confocal stacks or confocal stack subsets, respectively. For better visualization of individual muscular elements, the heliocoidal muscle layer and the outer dorsoventral muscles are omitted and only the ventral or dorsal half of the larva, with section plane in the region of the enrolling muscle, is shown in (d) and (h), respectively. Major muscle units in schematic representations are indicated by color code. a Dorsolateral aspect. The red arrow indicates the anteriorly shifted point of bifurcation of the rectus muscle. b Ventral aspect. c Right lateral aspect. d Dorsal muscle system seen from ventral. e Lateral view of the anterior region (left) showing the anterior-most arrangement of longitudinal muscle fibers. f Sagittal section of the anterior region (left) showing the vestibular retractor (arrowhead) and fibers of the terminally furcated pharyngeal retractor (double arrowhead). g Horizontal section of the anterior region shows the enrolling muscles (em) and the associated paired pharyngeal retractor (double arrowheads). h Ventral muscle system seen from dorsal. i Schematic representation of muscular elements of the anterior region (left). Scheme refers to panel (e). (i) without and (ii) with a schematic representation of the juvenile body wall musculature. j Sagittal section of the anterior region (left) with view on inner muscular elements. Scheme refers to (f). Dashed lines indicate the confocal image stack subset that was used in (g). Abbreviations: cerebral commissure (cc); enrolling muscle (em); helicoidal musculature (hm); mouth (m); pedal pit (pp); muscular pharynx (ph); rectus muscle (rem); ring musculature (rm); ventrolateral muscle (vlm); ventromedian muscle (vmm). Scale bars: 50 μm