Size-dependent toxicological effects of polystyrene microplastics in the shrimp Litopenaeus vannamei using a histomorphology, microbiome, and metabolic approach

Due to the wide application of plastic products in human life, microplastic pollution in water has recently attracted more attention. Many studies have revealed the size-dependent toxicity of microplastics. Here, we investigated the toxicological effects of polystyrene microplastics (PS-MPs) on the white leg shrimp, Litopenaeus vannamei, a profitable aquaculture species, using a comprehensive histomorphological, microbiome, and metabolomic approach to verify whether smaller particles are more toxic than larger particles. L. vannamei were experimentally exposed to water containing PS-MPs of four sizes (0.1, 1.0, 5.0, and 20.0 mu m) for 24 h at 10 mg/L (acute experiment) and 12 d at 1 mg/L (subchronic experiment). After 24 h of acute exposure, PS-MP accu-mulation in shrimp indicated that the ingestion and egestion of PS-MPs had a size-dependent effect, and smaller particles were more bioavailable. The tissue morphological results of subchronic experiments showed that, for the guts and gills, the smaller sizes of the PS-MPs exhibited greater damage. In addition, 16 S rRNA gene amplicon sequencing showed that the alpha diversity was higher under larger PS-MP exposure. Correlated with changes in intestinal bacteria, we found a greater enrichment of metabolic pathways in hemolymph proteins and metabolites in larger PS-MP groups, such as arginine and proline metabolism, protein digestion and ab-sorption, lysine degradation. Interestingly, the activity or content of biomarkers of oxidative stress showed a peak at 1 mu m and 5 mu m. Under specific sizes of PS-MPs, the abundance of the pathogen Vibrio and probiotic bacteria Rhodobacter (5-mu m) and Bacillus and Halomonas (1-mu m) were simultaneously enriched. Our results indicated that PS-MP exposure can cause size-dependent damage to shrimp, yet specific particle size can be influential differently in regard to some research indicators. Therefore, it can enhance our comprehensive un-derstanding of the impacts of microplastics on shrimp health and suggests that specific particle size should be considered when assessing the size-dependent toxicity of microplastics.

Automated summary

Due to the wide application of plastic products, microplastic pollution in water has become a concern. This study investigated the toxicological effects of different sized polystyrene microplastics (PS-MPs) on shrimp. It was found that smaller particles of PS-MPs had a higher ingestion and egestion effect, causing more damage to the guts and gills. The exposure to larger PS-MPs resulted in higher diversity of intestinal bacteria and enrichment of specific metabolic pathways. The study suggests that the particle size of microplastics should be considered when assessing their toxicity.