Figure 12From: Development of somites and their derivatives in amphioxus, and implications for the evolution of vertebrate somitesDevelopment of the perineural sheath. In all panels, the neural tube is to the right. In panels (A-E), myotome is adjacent to (left of) the perineural sheath, and in panels (F-G), sclerotome-derived mesothelium is present between the myotome and perineural sheath (see text). The perineural sheath develops at the interface between them. A basal lamina is first apparent in 2 GS larvae (C). The black arrowhead in (E) indicates striated collagen fibers, first apparent at the 9 GS stage, and the white asterisk in (F) marks the nucleus of a sclerotome-derived mesothelial cell. All panels are to the scale shown. Stage abbreviations: neur, neurula; GS, gill slit; met, early metamorphosis; adult, subadult.Back to article page