Toxicity assessment of zinc oxide nanoparticles in the early development of an autochthonous amphibian (Rhinella arenarum)

The growing use of nanomaterials raises concerns about their environmental release and effects on aquatic ecosystems; however, knowledge about their impacts on amphibians remains scarce. This study evaluated the toxicity of zinc oxide nanoparticles (ZnO-NPs) in early stages of the native amphibian Rhinella arenarum using a multi-biomarker approach. Lethal and sublethal effects, including morphological and behavioral alterations, neurotoxicity, genotoxicity, and disruption of lipid metabolism, were assessed. Larvae were more sensitive in acute exposure (NOEC 96 h: embryos >200 mg/L; larvae 5 mg/L), while embryos showed increased sensitivity in chronic exposure (LC50–504h: embryos 6.66 mg/L; larvae 0.45 mg/L), with gill and movement impairments. Micronucleus tests indicated genotoxicity, and increased butyryl and acetylcholinesterase activity showed neurotoxic effects, both at 5 mg/L. Lipid analysis revealed reduced triglycerides and phospholipids at 0.05 and 0.1 mg/L, suggesting metabolic disruption. These results stress the need to consider multiple endpoints to assess metal-based nanoparticle toxicity in amphibians.