Fig. 3

Actin assembly and organization in multinucleated primordial IFMs. a–d IFM primordia of early and late phases from L3 and L4 instars were stained with Rhodamine-Phalloidin (red) to highlight actin filaments and nuclei with DAPI to visualize nuclei (blue). a In early L3 primordium, disperse Phalloidin-labelled short actin filaments widely distributed were observed. b In late L3 instar, the muscle primordia showed abundant actin. At this stage primordia showed stripes forming sections-like along the primordium (dotted lines). c The early L4 primordium, actin polymerization led to the formation of immature myofibrils organized in bundles within myotubes. d The late L4 primordium showed a larger size and abundant immature myofibrils forming muscle fibers. At this stage, the nuclei were observed forming rows along the muscle fibers and, some of them showed a larger size than the others (dotted circles). Insets show enlargement of dashed boxes. Scale bar: 100 μm