Developmental exposures to an azole fungicide triadimenol at environmentally relevant concentrations cause reproductive dysfunction in females of medaka fish.

Triadimenol is an effective meatabolite derived from the triazole fungicide triadimenfon. It is an agriculturally important reagent of environmentally emerging concern because of its broad use, persistent occurrence in the environment and greater fungicidal or toxic potency than the parent compound. However, the ecotoxicological impact of triadimenol on fish populations remains unclear. In this study, we investigated developmental toxicity and endocrine disruption effects in medaka fish (Oryzias latipes) exposed at an early life stage to triadimenol. First, mortality, gross development and oxidative stress responses were assessed with triadimenol exposure (3-3000 μg/L) during the embryonic stage. Then, medaka at a sensitive stage of early sexual development underwent 35-day continuous chronic exposure to triadimenol, and the endocrine disruption effects were assessed in adulthood and the next generation. Embryonic exposure to triadimenol did not induce significant teratogenic effects or oxidative stress in embryos or hatchlings. However, early-life exposure to triadimenol under environmentally relevant concentrations (3-30 μg/L) and 300 μg/L persistently altered ovary development and reproduction in female adults and skewed the sex ratio in progeny. As well, triadimenol exposure interrupted the hormone balance, as seen by the expression of genes responsible for estrogen metabolism and egg reproduction. Environmentally relevant triadimenol exposure in medaka fish at early life stages may have ecotoxicological impact in aquatic environments. Along with previous studies, we suggest that conazoles share similar modes of action in disrupting hormone homeostasis and reproduction in fish and mammals.