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Fig. 5 RA is required during morphogenesis of the posterior endodermal pouches. Anterior endodermal pouches develop earlier than more posterior ones and inhibition of RA at different time points only affects newly forming pouches. A-D: ZN8 immunostaining of endodermal pouches, schematic drawing of pouches in 30-hpf control embryos, as well as cartilage staining of 96-hpf embryos. A: 30-hpf control embryos possess five endodermal pouches. At 96 hpf, 7 pharyngeal cartilages have formed. B: Embryos treated with DEAB between 16-30 hpf possess three pouches, pouches 4-5 are absent. At 96 hpf, 3 pharyngeal cartilages have formed. C: Embryos that were treated with DEAB between 20-30 hpf possess three fully formed pouches, the fourth one is only half formed and pouch 5 is missing. At 96 hpf, four pharyngeal cartilages have formed. D: Embryos that were treated between 24-30 hpf have four endodermal pouches and the fifth one is missing. At 96 hpf, five pharyngeal cartilages have formed. Abbreviations are the same as in Figure 3.