A. burtoni dlx expression patterns in the pharyngeal arches. Whole-mount in situ hybridization at 5 dpf. Gene names are shown on the left. (A, C, E, G, I, K, M, O) Ventral view. The boundary between the PA1 and PA2, delineated by the anterior end of hoxa2a expression (A), is indicated with dotted lines. (B, D, F, H, J, L, N, P) Lateral view of the anterior pharyngeal arches. Anterior is to the right. The outline of the eye is indicated by a dotted line. In the PA1, along the DV axis, dlx2a expression extended more broadly than the other dlx genes (F), while dlx3b expression was more restricted (J). dlx5a and dlx6a expression extends more towards the ventral midline (M, O), while dlx4a is downregulated in ventral parts of the anterior PAs (G). Relatively weak expression of dlx1a and dlx2a was detected in PA3 and PA4 (C, E). Abbreviations: e = eye; PA1 = first pharyngeal arch; PA2 = second pharyngeal arch. Scale bar: 100 μm.