Fig. 4From: Activin/Nodal signaling mediates dorsal–ventral axis formation before third quartet formation in embryos of the annelid Chaetopterus pergamentaceusLarval phenotypes resulting from early embryonic exposure to U0126. Each column contains merged confocal-stacked images from a single L2 larva. Each row depicts labeling for nuclei with Hoechst, actin filaments with phalloidin, or neurons with anti-FMRFamide. Stacks of confocal micrographs of actin labeling are displayed at two different depths in the body to show both muscles and gut cavity organization. a–d are of a control larva exposed to 0.2% DMSO during the interval between the 4 cell stage and the early gastrula. e–l are larvae resulting from exposure to 20 μM U0126. e–h depict a larva resulting from exposure during the interval between the 4 cell to late cleavage stage. i–l depict a larva resulting from exposure during the interval between late cleavage stage and early gastrula. All panels are dorsal views with anterior to the left. agc: abnormal gut cavity; at: apical tuft attachment point; cc: circumesophageal connective; cbr: cerebral commissure; dor: dorsal; hg: hindgut; mc: main connective; mg: midgut; sc: subesophageal commissure; st: stomodeum; white arrowhead: dorsal longitudinal muscle fibers; white arrows: disorganized muscle fibersBack to article page