Confocal sections of wild-type (A-F) and mutant (glw-b/glw-c, G-L) Nematostella vectensis, labeled with an antibody against acetylated ∂-tubulin (acTub). Filamentous actin is labeled with phalloidin (Pha), and nuclei are labeled with DAPI. All panels show side views of animals with the blastpore/mouth facing up. (A-C, G-I): mid-planula. Similar to the wild-type, glw-b/glw-c mutant planulae develop apical tufts (at) at the aboral pole; in addition, the basal translocation of nuclei in the aboral-most ectoderm (arrowheads in A, G, M), as well as the development of myofilaments in the endoderm (arrowheads in C, I), are evident. (D-F, J-L) primary polyp. glw-b/glw-c mutants develop into morphologically normal primary polyps, forming a set of four oral tentacles (D, J) with longitudinally oriented muscle fibers in the endoderm (arrowheads in F, L) and hair cells in the ectoderm--a polyp-specific cell type in N. vectensis (Nakanishi et al., 2012; Watson et al., 2009)-- characterized by a single cilium (ci) surrounded at the base by stereocilia (st) (insets in F, L). Note also the development of eight sets of longitudinally oriented parietal (pm) and retractor (rm) muscles in the endoderm of the body column (D, J), and the loss of apical tufts (arrowheads in E, K), in wild-type as well as glw-b/glw-c mutant animals. Abbreviations: ph pharynx; ec ectoderm; en endoderm. Scale bar: 50 µm; 5 µm (inset in F, L).