Paclobutrazol (PBZ), a trazole-containing fungicide, is widely used on food crops. Frequent usage of PBZ may contaminate water, but its toxicity to aquatic organisms is understudied. Although the chronic effects of PBZ exposure on reproductive, antioxidant defense, and liver metabolism systems in rockfish have been reported, the toxic effects of PBZ on aquatic embryos are unknown. Here, we report that PBZ disrupts the development of heart and craniofacial cartilage in zebrafish embryos, and decreases their survival and hatching rates. PBZ affects the normal process of cardiac looping, which may lead to a slower heart beat accompanied by pericardia edema and apoptotic myocytes. PBZ also decreases the population of migratory neural crest cells, which give rise to craniofacial cartilage. Our results reveal high embryonic toxicity of PBZ on aquatic organisms, and thus hold significance for the impact of fungicides on public health and ecology.
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