Expression of Oikopleura dioica Pax2/5/8 paralogs during organogenesis. Whole mount in situ hybridization of Pax2/5/8a (A, C) and Pax2/5/8b (B, D) in late hatchling stages during the initial (A, B) and advanced state (C, D) of the expansion of internal organ cavities during organogenesis. Lateral aspect (A, B, C and D) and integrated ventral view (A', B', C' and D') for each stage are shown. Anterior is to the left and dorsal to the top. Details of the Pax2/5/8 expression domains in the gills (dashed squares and lines in C and D) are shown in lateral (C" and D") and frontal (C"', D"') views. The position of the ciliary rings (cr) is labeled with an arrow. Colored arrowheads label some of the domains (black, stomodeum, st; yellow, anterior pharynx, ph; blue, posterior pharynx; white, endostyle, en; purple, gills, g; orange, medial wall of the heart, h; green, anus and rectum, r; red, base of the Langerhans receptors, LR, and posterior part of the trunk). Scale bar = 10 μm.