Fig. 10

In situ hybridization of posterior/hindgut, mesoderm, and endoderm markers in the development of M. membranacea. Orientation of the embryos is indicated below each column and exceptions are labeled on individual panels. In vegetal views, the B quadrant is top and D quadrant is bottom. In left views, the B quadrant (anterior region) is to the left. In all views, except for vegetal views, the animal pole is top. Arrowheads indicate expression and dashed areas mark unspecific staining attached to the shell valves of some embryos. Arrowhead outlines indicate expression at a different focus plane. Asterisks indicate the position of the blastopore. 16-cell = 5.2 hpa, 28- to 32-cell = 6.7–7.5 hpa, early gastrula = 11 hpa, mid gastrula = 16 hpa and late gastrula = 24 hpa. Scale bar = 10 μm