Is the zebrafish reproductive system sensitive to environmental toxicants? An opinion

Abstract Growing contamination of aquatic environments by diverse chemical pollutants raises urgent questions about their reproductive consequences for aquatic vertebrates and, by extension, for human health. Zebrafish (Danio rerio) have proven particularly well-suited to address such questions, owing to their close genetic homology with humans (~70%), optically transparent embryos, and compatibility with high-throughput exposure protocols. In this opinion article, we review and critically appraise published studies on the reproductive toxicity of pesticides, fungicides, antibiotics, heavy metals, microplastics, nanoparticles, synthetic dyes, and plant- or bacterial-derived metabolites, as evaluated in zebrafish. Across this breadth of chemical classes, a consistent picture emerges: contaminated exposures impair gametogenesis, alter hormonal profiles, reduce fertilization success, and perturb embryonic development. The predominant mechanisms identified include endocrine disruption, particularly interference with the hypothalamic–pituitary-gonadal axis, oxidative stress, and genotoxicity. More troublingly, reproductive harm occurs at concentrations routinely detected in natural water bodies, and some substances transmit adverse effects across generations. On the basis of this evidence, we suggest that zebrafish reproductive assays merit further validation and consideration as a complementary component of chemical safety evaluation, and that mechanistic assessment of reproductive hazard warrants greater attention within a weight-of-evidence approach to risk assessment, alongside established mammalian and aquatic test systems.