Multigenerational effects of nanoplastics on life-history traits and physiological responses in Drosophila melanogaster

The ubiquitous presence of nanoplastics (NP) in the environment has emerged as a global concern. Their impacts have been mostly studied in aquatic ecosystems and species, and more recently, in terrestrial species. In addition, the toxicity of NP on organisms exposed continuously to this pollutant and over multiple generations remains poorly considered. Our study focused on the effects of chronic exposure of a polydisperse mix of polystyrene NP (20, 80, and 200 nm) on the fruit fly Drosophila melanogaster to four NP concentrations (0, 1, 100, and 500 μg NP.g^-1 of food) over 10 generations. Their toxicity was assessed at the first (F1) and tenth (F10) generations by evaluating phenotypic (viability, development time, body size and body weight) and physiological responses, through enzyme activities related to oxidative stress and the expression of specific target genes (e.g. apoptosis, immunity). Our results showed a decrease in organisms' key traits in the first and tenth generations, with a reduced viability and body size. Additionally, superoxide dismutase (SOD) activity was altered, with a decrease observed in the F1 generation, followed by an increase in F10, in flies exposed to 500 μg NP.g^-1. Finally, the expressions of target genes involved in apoptosis and immune responses were either up- or down-regulated, depending on the generation. These results highlighted the effects NP can have on life-history or physiological traits without higher effect across generations. In addition, the study reveals the complex response across generation and highlights the importance to study long-term exposure.