113 | Ecotoxicological effects of bromuconazole in Oryzias latipes from embryos to adult endpoints

Tania Russo^1|2, Ilaria Olivito¹, Iolanda Carratù², Chiara Barone², Ivan Conte², Anna Di Cosmo², Gianluca Polese², Elvira Brunelli¹ | ¹Dipartimento di Biologia, Ecologia e Scienze della Terra, Università della Calabria, Rende [CS], Italy; ²Dipartimento di Biologia, Università di Napoli Federico II, Napoli, Italy.

Bromuconazole (BRO) is a triazole fungicide widely used in agriculture and approved in the European Union until 2027. However, it is classified as a Candidate for Substitution due to its persistence, bioaccumulative potential, and toxicity (PBT). Its occurrence in surface waters raises concerns for aquatic organisms. BRO has recently been included in the 5th Watch List of the EU Water Framework Directive (2000/60/EC), with a very low predicted no-effect concentration (PNEC) for aquatic systems of 0.015 µg/L. Although cardiotoxicity and metabolic alterations have been reported in Danio rerio [1,2], information about how this compound influences embryonic development or affects organs such as the liver, brain, and eye remains limited. In this study, for the first time, we used the widely adopted teleost model in ecotoxicology, Oryzias latipes (medaka), to explore BRO‑induced effects by integrating both embryonic and adult exposure scenarios. Embryos were exposed to increasing concentrations of BRO (5-20 µg/mL) for 10 days and monitored for survival and developmental endpoints. BRO induced a clear dose- and time-dependent increase in mortality, and dose-response modelling allowed estimation of LC50 values. In parallel, embryos showed marked dose-dependent developmental impairment, including growth delay and abnormal morphogenesis, suggesting disruption of key developmental pathways, and highlighting the high sensitivity of early-life stages to triazole fungicides. To complement early-life stage data, adult medaka are included in the experimental design under a sub-chronic exposure framework at environmentally relevant concentrations, coupled with behavioral observations and multi-organ analyses. Target tissues include gills, liver, brain, and eye, allowing the integration of organism-level effects with histological, ultrastructural, and molecular responses related to oxidative stress, inflammation, development, and neurotoxicity. Overall, the combined evaluation of embryonic toxicity with adult-level responses provides a more comprehensive characterization of BRO ecotoxicity. This indicates the potential risk posed by triazole fungicides to aquatic vertebrates and ecosystem health, supporting environmental risk assessment and regulatory monitoring.