Polystyrene Microplastic Beads Caused Cellular Alterations in midgut cells and Sex-Specific Toxic Effects on Survival, Starvation Resistance, and Excretion of the Model Insect Drosophila melanogaster

<title>Abstract</title> Although the toxicity of microplastics in aquatic creatures has been extensively studied, there have been far fewer studies in terrestrial organisms. Here, we conducted a series of experiments to understand whether exposure to different concentrations (0.005, 0.05, 0.5 µg/ml) of polystyrene microplastics beads PS-MPs (2 µm in size) can impact feeding activity and modulate digestion and excretion, using the fruit fly <italic>D. melanogaster</italic> as a model of terrestrial organisms. The ability of adult male and female flies to distinguish between food treated with PS-MPs and food not treated with PS-MPs was tested first, and then we evaluated the effects of a 7-day short-term exposure to PS-MPs on food intake, mortality, starvation resistance, fecal pellet count, and the cellular structure of mid gut cells. The results revealed that flies can really differentiate and ignore MPs-treated food. We discovered sex-specific effects, with male flies being more sensitive to PS-MPs, with all males dying after 14 days when exposed to 0.5 µg/ml of PS-MPs, whereas 20% of female flies survived to day 20. Furthermore, regardless of concentration, nearly all male flies exposed to PS-MPs died after 24 hours of starvation. Only female flies fed media containing 0.05 or 0.5 µg/ml PS-MPs had significantly fewer fecal pellets. PS-MPs also showed concentration-dependent effects on the cellular structure of midgut cells in both male and female flies, that are indicative of cell necrosis and apoptosis. Our findings provide new insights into MP toxicity and will be useful in assessing the environmental risks associated with MPs as newly emerging pollutants.