Impacts of nanopolystyrene and/or phoxim exposure at environmentally relevant concentrations on the intestinal histopathology, intestinal microbiota, and metabolome in Eriocheir sinensis

Nanopolystyrene (NP) pollution in aquatic environments has become an increasing concern. Phoxim (PHO), one of the major organophosphorus pesticides, has also been detected in aquatic environments, posing serious health risks to crustaceans. This study aimed to assess the detrimental effects of NP and/or PHO exposure at environmentally relevant concentrations on the intestinal histopathology, intestinal microbiota, and metabolome of adult crabs ( Eriocheir sinensis ) for 21 days. Our study revealed significant histopathological abnormalities in the intestines. In all the exposure groups, there was a discovery of vacuolar degeneration occurring in epithelial cells. Additionally, the peritrophic membrane exhibited thinning after NP or PHO single exposure, while thickening was observed after co-exposure. Exposure to NP and/or PHO disrupted the intestinal microbiota homeostasis, as evidenced by the proliferation of pathogenic bacteria and suppression of beneficial bacteria. Notably, PHO exposure resulted in increased abundance of pathogenic bacteria ( Spiroplasma and Arcobacter ) and decreased abundance of beneficial bacteria ( Bacteroides ). Analysis of the metabolome revealed that exposure to NP and/or PHO led to alterations in the metabolic profile as well as several critical pathways. Among these, the upregulation of arachidonic acid metabolism, ABC transporters, and biosynthesis of amino acids was observed in both NP single exposure and co-exposure, while PHO single exposure downregulated these pathways. Additionally, NP and/or PHO exposure downregulated neuroactive ligand-receptor interaction. Spearman correlation analysis revealed that the significant reduction of some differentially expressed metabolites (DEMs) was potentially regulated by the low-abundance bacterial genera following exposure to NP and/or PHO. And these DEMs have a role in anti-inflammatory or antioxidant properties. Collectively, our results offer novel perspectives on the intestinal toxicity of crustaceans by NP and/or PHO at environmentally relevant concentrations.