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Polystyrene Microplastics Impair Intestinal Homeostasis in Juvenile Tachypleus tridentatus Through Oxidative Imbalance and Gut Microbiota Dysregulation
Summary
Scientists found that microplastic pollution damages the gut health of juvenile horseshoe crabs, causing oxidative stress, weaker immune defenses, and an imbalance of gut bacteria (fewer good bacteria, more harmful ones), similar to gut dysbiosis linked to inflammation in humans. While this study was done in horseshoe crabs, not people, it adds to growing evidence that microplastics can disrupt gut health across species, raising concerns about what similar exposure might mean for human digestive and immune health.
Microplastics (MPs) are ubiquitous marine pollutants that pose increasing ecological risks, yet their effects on intestinal physiology and gut microbial homeostasis during the juvenile developmental stages of Tachypleus tridentatus remain unclear. In this study, fifth- and sixth-instar juveniles of T. tridentatus were exposed to environmentally relevant concentrations of 6.0 μm polystyrene microplastics (PS-MPs; 0, 10², and 10⁴ particles/L) for 7 and 21 days to investigate intestinal toxicity and its underlying mechanisms. Intestinal accumulation, oxidative stress, innate immune responses, and gut microbiota were comprehensively evaluated. PS-MPs exposure induced dose- and time-dependent alterations in superoxide dismutase, catalase, malondialdehyde, and lysozyme, indicating excessive oxidative stress, impaired antioxidant defense, and compromised innate immunity. Fifth-instar juveniles exhibited stronger oxidative stress and immune responses than sixth-instar individuals, suggesting higher susceptibility during earlier developmental stages. Gut microbiota analysis revealed pronounced dysbiosis, characterized by a reduced relative abundance of Firmicutes, enrichment of Proteobacteria, depletion of beneficial taxa (e.g., Lactococcus), and increased abundance of opportunistic bacteria, including Pseudomonas and members of Enterobacteriaceae. These physiological and microbial alterations collectively suggest that environmentally relevant PS-MPs impair intestinal homeostasis in juvenile T. tridentatus by inducing oxidative imbalance, modifying innate immune responses, and reshaping gut microbial communities, with clear instar- and exposure time-dependent effects. These findings highlighting the importance of developmental stages in ecological risk assessment for benthic arthropods.