We investigated the effects of different nanoplastic (NP, size = 100 nm) concentrations on red crayfish (Cherax quadricarinatus) and examined toxicity mechanisms. We established four concentration groups (control (CK): 0 μg/L; Low: 100 μg/L; Medium: 500 μg/L; and High: 1000 μg/L) and analyzed toxicity effects in C. quadricarinatus hepatopancreas using histopathological, transcriptomic, metabolomic, and fluorescence methods. NP exposure caused histological lesions and oxidative stress in hepatopancreas, and also significantly decreased glutathione (GSH) (P