Fig. 6. Muscles appear to develop normally in Sply⁰⁵⁰⁹¹ homozygous embryos and larvae. Immunofluorescent staining with -Mef2 (A) and -myosin heavy chain (B) suggests that myoblasts differentiate, migrate, and fuse normally to produce a well-patterned array of embryonic muscles. Larval somatic musculature appears normal (C), most notably with respect to the dorsal oblique muscles (white arrows), which serve as templates for the adult dorsal longitudinal muscles. (Note that dorsal acute muscle 1 was ablated to facilitate visualization of DOMs.) Furthermore, transmission electron microscopy (D) reveals that persistent adult DLMs have intact myofibrils (myo) and structurally normal mitochondria (mit) and nuclei (nuc).