Developmental effects of zebrafish embryos upon PREL exposure. (A) Determined end points in the experiments at different developmental stages. Significantly affected end points were marked red on the left diagram. (B) Yolk extension formation of 16 hpf embryos under PREL exposure (n = 4 replicates, each replicate contains 30 embryos). (C) Contraction rate of 20 hpf embryos under PREL exposure (n = 4 replicates, each replicate contains 30 embryos). (D–F) Ocular melanin density, heart rate, and pigmentation of the body of 36 hpf embryos under PREL exposure (n = 4 replicates, each replicate contains 8 embryos, respectively). The key for bpm: beats per minute. (G) Swimming activity of 72 hpf embryos under PREL exposure (n = 4 replicates, each replicate contains 12 embryos). Each bar represents mean value ± SD (standard deviation). The asterisk indicates a significant difference compared to solvent control (*p < 0.05, **p < 0.01, ***p < 0.001).

PREL accelerates zebrafish embryogenesis as presented by the number of somites, head-trunk angle, and yolk sac size of embryos. Measured end points are depicted graphically above the data in red color for clarity. (A) Number of somites of 18 hpf embryos under PREL exposure (n = 4 replicates, each replicate contains 5 embryos). (B) Head-trunk angle of 20 hpf embryos under PREL exposure (n = 4 replicates, each replicate contains 5 embryos). (C) Area of the yolk sac of 20 hpf embryos under PREL exposure (n = 4 replicates, each replicate contains 5 embryos). Each bar represents mean value ± SD (standard deviation). The asterisk indicates a significant difference compared to solvent control (*p < 0.05, **p < 0.01, ***p < 0.001).