Immunotoxicity analysis of Pardosa pseudoannulata under cadmium-alone and co-existence of nanoplastic exposures

The widespread presence of heavy metals, particularly cadmium (Cd), in agroecosystems has long raised environmental concerns, while emerging contaminants such as microplastics further complicate risk assessment and management. In this study, we investigated the combined effects of Cd and polystyrene nanoplastics (PS-NPs) on the physiological and immune responses of the wolf spider Pardosa pseudoannulata . Our results revealed progressive accumulation of PS-NPs in spider tissues, while Cd concentrations increased over time and varied with PS-NPs levels. Histological analysis showed that Cd exposure alone caused elongation and disorganization of midgut epithelial cells with leakage of intracellular contents, whereas co-exposure induced cell swelling, blurred boundaries, and intracellular particle retention. In addition, an increase in wall thickness of the gut was observed in all exposed spiders. Consistently, cellular damage was more pronounced under combined exposure, as evidenced by significantly increased hemolymph apoptosis, which exhibited a non-monotonic dose-response pattern. Transcriptomic analysis revealed extensive gene expression changes, especially in the high-concentration group. A set of shared differentially expressed genes was primarily associated with energy metabolism, immune response, and protein synthesis pathways, with oxidative phosphorylation and ribosome functions identified as key modules. Moreover, immune-related genes in “Apoptosis” and “Necroptosis” pathways displayed consistent expression patterns with apoptosis rates. Overall, these results demonstrate that NPs modulate Cd accumulation and toxicity in a non-monotonic dose-response manner, leading to distinct physiological and transcriptional responses in P. pseudoannulata . This study provides new insights into the ecological risks of combined pollutants and highlights the importance of considering their interactions in agroecosystem management.