Sex-specific toxicity of PMMA Microplastics: Behavioral and metabolic dysregulation in adult Drosophila melanogaster

This study used Drosophila melanogaster as a model organism to systematically investigate the sex-dependent effects of polymethyl methacrylate (PMMA) microplastics (5 μm) on adult behavior, metabolism, and lifespan across concentrations ranging from 0.1 to 20 g/L. After 20 days of chronic exposure, male flies exhibited continuously enhanced motor activity with increasing dose, characterized by significant increases in limb waving frequency and stride length, as well as gait transitions from non-standard to quadrupedal patterns, indicating decreased motor coordination. Female flies showed significantly increased activity and reduced sleep at low concentrations (0.1-1 g/L), but weakened effects at high concentrations, exhibiting an inverted U-shaped dose response. At the metabolic level, 1 g/L PMMA-MPs significantly disrupted energy homeostasis in female flies, with increased blood glucose and decreased lipid and protein content, suggesting that low doses activate catabolic metabolism, while high concentrations may induce lipid reaccumulation and protein synthesis compensation through oxidative stress. Male metabolic indicators showed minor changes. The sex differences in behavior and metabolism may be related to neurotransmitter systems (dopamine, serotonin) and reproductive energy allocation strategies. This study reveals the sex-specific toxicity pathways of PMMA-MPs in terrestrial model organisms, providing key experimental evidence for assessing microplastic ecological risks and developing pollution prevention and control strategies.