Temporal and spatial expression of the Udu gene during early zebrafish development. (A-I) Lateral views of WISH of udu expression in 1-cell (A), 2.5-hpf (B), 4-hpf (C), 6-hpf (D), 10-hpf (E), 12-hpf (F), 14-hpf (G), 18-hpf (H), and 24-hpf (I) embryos. White and black arrows indicate the ICM and the anterior region of kidney duct, respectively. Embryos in panels A-D are orientated with animal pole on top, whereas embryos in panels E-I are orientated with anterior to the left.