Sublethal fipronil exposure impairs development and behavior in Drosophila melanogaster

The use of pesticides, particularly insecticides, is integral to modern agriculture. Fipronil, a widely used phenylpyrazole insecticide, is classified as a class II toxicant, indicating high toxicity by ingestion and contact. This study evaluated the morphometric and toxicological effects of fipronil on D. melanogaster development. Embryos were exposed orally from the embryonic stage to adulthood at 16, 40, 81, 163, 327, and 490 nM. The highest concentration reduced adult emergence from pupae, while survival decline at the three highest concentrations. Locomotor behavior was impaired at 81 nM in both sexes. Fipronil induced 24-h mortality in adult flies at concentrations ≥ 327 nM, with a median lethal concentration (LC₅₀) of 442 nM. Canonical variate analysis (CVA) revealed sex-dependent differences and shape changes at 16 and 40 nM compared with controls. Overall, these findings indicate fipronil toxicity in D. melanogaster and suggest that this model can help anticipate effects in other invertebrates.