Jun Bo

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 physiological responses and potential mechanisms associated with PS-MP exposure. Intestinal retention, oxidative stress, innate immune responses, and gut microbiota were comprehensively evaluated. PS-MP exposure induced concentration-dependent and time-dependent alterations in superoxide dismutase, catalase, malondialdehyde, and lysozyme, suggesting oxidative imbalance and modulation of innate immune responses. Fifth-instar juveniles displayed more pronounced oxidative-stress alterations and divergent innate-immune profiles relative to sixth-instar conspecifics, pointing to greater physiological susceptibility at earlier developmental stages. Gut microbiota analysis revealed pronounced dysbiosis, characterized by a reduced relative abundance of Bacillota, enrichment of Pseudomonadota, 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 highlight the importance of considering developmental stages in ecological risk assessment for benthic arthropods.

Microplastic pollution has become an emerging threat to marine biodiversity, yet the developmental-stage-specific responses of endangered marine species remain poorly characterized. Tri-spine horseshoe crab Tachypleus tridentatus, a threatened marine arthropod of high ecological and conservation value, is exposed to microplastics in coastal habitats. In this study, fifth-instar and sixth-instar juvenile T. tridentatus were exposed to polystyrene microplastics (PS-MPs) with a diameter of 6 μm at environmentally relevant concentrations (0, 10², 10⁴ particles/L) for 7 and 21 days. Fluorescence imaging revealed the accumulation of PS-MPs within the intestinal tract, with stage - dependent retention patterns across developmental stages. Transcriptomic analysis revealed significant differential gene expression upon PS-MP exposure, with affected pathways related to energy metabolism, immune regulation, stress response, signal transduction, and development. Younger juveniles exhibited stronger transcriptional disturbances in metabolic and stress-related pathways, whereas older juveniles showed more coordinated regulation of homeostatic and adaptive genes. These findings suggest that juvenile T. tridentatus employs instar-dependent molecular response strategies when confronted with microplastic exposure, reflecting developmental differences in stress sensitivity and adaptive capacity. Our study provides new insights into the molecular mechanisms underlying responses to microplastic exposure in an endangered marine species and highlights the importance of incorporating developmental-stage variation into ecological risk assessments and conservation strategies for T. tridentatus in polluted coastal ecosystems.

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.

Riverine ecosystems represent critical nodes in the global carbon cycle, where the mechanistic role of viruses in modulating eukaryotic carbon cycling remains underexplored, particularly across heterogeneous landscapes. Here, we applied metatranscriptomics to dissect how multi-scale environmental factors and viral gene activity jointly regulate the spatial transcription of carbon cycling genes in riverine eukaryotic communities along the Yongding River, China. Our analyses reveal pronounced spatial heterogeneity in both viral gene expression—notably major capsid proteins of large eukaryotic DNA viruses—and carbon fixation, conversion, and metabolism pathways, peaking in agriculturally impacted plain regions. Multivariate statistics and network analyses demonstrate that land use enhances viral gene activity, serving as biological amplifiers that modulate host carbon metabolism and transformation. Structural equation modeling further identifies a cascade in which cropland coverage elevates viral gene expression, ultimately driving a 1.8-fold increase in TCA cycle gene transcription in plain regions, whereas nitrogen loading at the site scale suppresses viral activity and carbon fixation. Phylogenetic analysis corroborates that virus–host specificity underpins these spatial patterns. Collectively, these findings advance a new model in which viruses act as key intermediaries, transmitting multiscale environmental signals to shape riverine carbon cycling. Our study highlights the urgency of incorporating viral ecology into predictive frameworks of riverine biogeochemical cycling under accelerating environmental change.