Iridophore development in the posterior trunk of xanthophore, melanophore and double mutants. pfe (A-D), nac (E-H), nac;pfe (I-L) and shd;pfe (M-P) mutants. In pfe, as well as in nac and nac;pfe mutants, X0 is more prominent than in wild type; it expands to cover the entire flank in nac;pfe mutants. In shd;pfe mutants, melanophores distribute evenly also in the territory normally occupied by X0. Stages: PB, pelvic fin bud; PR, pelvic fin ray. SP, squamation onset posterior; J+, juvenile+. Scale bars: 250 μm.