Metabolic effects of dietary exposure to polystyrene microplastic and nanoplastic in fruit flies

Understanding how anthropogenic change impacts metabolic physiology is crucial for predicting species survival and ecosystem dynamics. Microplastics are ubiquitous in both aquatic and terrestrial environments and can disrupt organismal physiology. We used Drosophila melanogaster as a model species to identify the metabolic effects of dietary exposure to 1 µm polystyrene microplastic (MP) and 50 nm nanoplastic (NP) particles. We exposed flies to ecologically relevant and equivalent doses (1.4×1011 particles day-1 kg-1 larvae for MPs; 1.2×1018 particles day-1 kg-1 larvae for NPs) from egg to adult eclosion and used flow-through respirometry to investigate changes in the volume of carbon dioxide production and evaporative water loss rate. We observed that MP exposure disrupted the relationship between carbon dioxide production and water loss rate - suggesting the use of alternative metabolic pathways - while NP exposure did not. Such responses could have implications for physiological function, ecological interactions and evolutionary trajectories amid ongoing environmental change.