Expression of Pax2/5/8 paralogs at tailbud stages in Oikopleura dioica. Whole mount in situ hybridization of Pax2/5/8a (A, C, E) and Pax2/5/8b (B, D, F) at incipient-tailbud stage (A, B), early-tailbud stage (C, D), and mid-tailbud stage (E, F) in lateral views (anterior to the left and dorsal to the top). Specific aspects of the expression domains are shown in ventral (A', C' and E') and frontal views (E") in optical sections in the plane of the dashed white lines. Colored arrowheads label expression domains (black, stomodeum, st; yellow, anterior pharynx, ph; red, placodal precursor of the Langerhans receptors, LR). Scale bar = 10 μm.