A network of smooth and striated muscles operates the pilidial body. All panels show brightest-point projections of confocal Z-series of M. alaskensis larvae fixed and stained with phalloidin. (A) Lateral view of ~4-week-old pilidium. Prominent muscle fibers run along the margins of anterior and posterior lobes (al, pl) and lappets (la), and also span the bases of lappets; radial muscle fibers running along the inner surface of the outer epithelium make connections to the lappet and lobe margins every 10-20 μm. Also apparent is the regular row of collar cells (cc) along the primary ciliated band. This panel was re-rendered from the same dataset as Ref. 21, Figure 5A. (B) View from underneath the posterior lobe of a 17-day-old pilidium, showing a similar musculature as in (A), but sparser. The radial muscles of the lappet are striated. Note the bifurcation of radial muscles near the margin. Also note that the inner ciliated band in the lappets is also populated by collar cells (inset, arrows, cc). (C) Close-up of the lappet musculature in a 17-day-old pilidium. Most of the radial fibers are clearly striated; the marginal band is not. (D) Close-up of the musculature of the posterior lobe in a 17-day-old pilidium, illustrating that some of the radial fibers are striated, some are not (yet). Note also the posterior cirrus (pc) and the single row of collar cells (arrows, cc) in the primary ciliated band.