Body wall muscles atrophy during sedentary stages.

Fluorescent micrographs of phalloidin-stained H. glycines. The J2 body wall muscles (image from head region) contain actin-enriched striated filaments obliquely oriented to the longitudinal axis. In J3, the diameter of muscle filaments is smaller than in J2 and lacks a well-defined organization. The phalloidin-stained body wall muscle filaments are thicker in J4 males compared with J3. In the adult male, the body wall muscles contain additional filaments, but are otherwise similar to J2 body wall muscles. In J4 females, the size of the actin-enriched muscle filaments is further reduced compared to J3s. Also see S1 Fig. Scale bars, 5 μm.