Short-term effects of the strobilurin fungicide dimoxystrobin on zebrafish gills: A morpho-functional study

Strobilurins represent the most widely used class of fungicides nowadays andare considered relatively non-toxic to mammals and birds but highly toxic to aquatic biota. Dimoxystrobin is one of the novel strobilurins, recently included in the 3rd Watch List of the European Commission as available data indicate that it could pose a sig-nificant risk to aquatic species. As yet, the number of studies explicitly assessing the impact of this fungicide on terrestrial and aquatic species is extremely low, and the toxic effects of dimoxystrobin on fish have not been reported. Here we investigate for the first time the alterations induced by two environmentally relevant and very low concentrations of dimoxystrobin (6.56 and 13.13 mu g/L) in the fish gills. morphological, morphometric, ul-trastructural, and functional alterations have been evaluated using zebrafish as a model species. We demon-strated that even short-term exposure (96 h) to dimoxystrobin alters fish gills reducing the surface available for gas exchange and inducing severe alterations encompassing three reaction patterns: circulatory disturbance and both regressive and progressive changes. Furthermore, we revealed that this fungicide impairs the expression of key enzymes involved in osmotic and acid-base regulation (Na+/K+-ATPase and AQP3) and the defensive response against oxidative stress (SOD and CAT). The information presented here highlights the importance of combining data from different analytical methods for evaluating the toxic potential of currently used and new agrochemical compounds. Our results will also contribute to the discussion on the suitability of mandatory ecotoxicological tests on vertebrates before the introduction on the market of new compounds.

Automated summary

Strobilurins, including dimoxystrobin, are widely used fungicides that are relatively non-toxic to mammals and birds but highly toxic to aquatic biota. However, there is limited research on the impact of dimoxystrobin on terrestrial and aquatic species, especially fish. This study investigated the effects of environmentally relevant concentrations of dimoxystrobin on fish gills, revealing structural and functional alterations, as well as impairment of key enzymes involved in osmotic regulation and oxidative stress defense. The findings emphasize the importance of comprehensive evaluation of the toxic potential of agrochemical compounds and highlight the need for ecotoxicological tests before the introduction of new compounds to the market.