Biochemical and morphological alterations in Rhinella arenarum larvae exposed to the prometryn-based formulation Prometrex FW®.

Increasing agricultural intensification in the Argentine Pampas has heightened native amphibians' exposure to herbicides. We evaluated the acute sublethal effects of Prometrex FW®, a commercial prometryn-based herbicide formulation containing 50% active ingredient (a.i.), on premetamorphic larvae of Rhinella arenarum under laboratory conditions, focusing on genotoxicity, oxidative stress, growth, and morphological alterations. Larvae were exposed for 48 and 96 h to 0.0015, 0.015, and 15 mg a.i./L, including an environmentally relevant concentration and a level far below the manufacturer's recommended application rate. Genotoxicity was assessed using the alkaline comet assay, whereas antioxidant responses were evaluated by measuring catalase (CAT) and glutathione S-transferase (GST) activities, as well as glutathione (GSH) content. The herbicide significantly increased the genetic damage index in all concentrations tested. Antioxidant biomarkers (CAT, GST, and GSH) were significantly elevated, indicating oxidative stress. Moreover, larval growth was significantly inhibited across treatments. This study provides the first evidence of acute sublethal effects of the prometryn-based formulation Prometrex FW® in this Neotropical anuran, underscoring the potential ecological risk of this herbicide to non-target species even at low concentrations.