Expression of Pax2/5/8 paralogs in Oikopleura dioica hatchlings. Whole mount in situ hybridization of Pax2/5/8a (A, C) and Pax2/5/8b (B, D) in early-hatchling stage (A, B) and mid-hatchling stage (C, D). Lateral (A, B, C, D) and ventral (A', B', C' and D') views for each stage. Anterior is to the left and dorsal to the top. Insets (A", B", and C") show details of the regions on the surface of the embryo where the Langerhans receptors eventually form. Colored arrowheads label expression domains (black, stomodeum, st; yellow, anterior pharynx, ph; blue, posterior pharynx, ph; white, endostyle, en; purple, presumptive cell precursors of the gills, g; red, placodal precursor of the Langerhans receptors). The position of the anterior tip of notochord (n) is demarcated (white line). Scale bar = 10 μm.