Fig. 7

Muscle fibers are extensively generated during metamorphosis. Morphological changes during the P. flava transition from the Spengel (a-c) to the Agassiz (d-e) and then to the juvenile stage (f-g). Fully developed protocoel, mesocoel and metacoel are outlined by white dashed lines in panel a. Phalloidin staining (green) revealed the distribution of muscle fibers in the protocoel of the Spengel larva (b and c, viewed from the lateral and the apical side, respectively), and in the proboscis and trunk regions at the Agassiz (e) and the juvenile (g) stages. The asterisks in (b) and (c) indicate the position of the mouth. Nuclei were counterstained with Hoechst 33,342 (blue). Scale bar: 1 mm. Abbreviations: pc, protocoel; mesoc, mesocoel; metac, metacoel; prob., proboscis; col., collar