Whole mount in situ hybridization analysis for oclna and oclnb (purple) and smyhc1 (red) at the 16–28 somite stage (ss), 36 and 48 hours post fertilization (hpf) in wild-type embryos. Embryos are shown in lateral views with anterior to the left. Black lines (indicating strong expression) and black dotted lines (indicating weak/low-level expression) demarcate transcript domains within the pronephros (PCT, PST, DE, DL, and PD), while blue dotted lines indicate the intense pronephros PD expression noted at particular time points.