# Effects of Nano-Silver Exposure on Oxidative Stress, Transcriptome, and Intestinal Microbiota of Procambarus clarkii

## TL;DR

This study shows that nano-silver exposure harms crayfish tissues, disrupts gut bacteria, and alters gene activity, raising concerns about its use in aquaculture.

## Contribution

The study is the first to comprehensively analyze nano-silver's effects on crayfish through histopathology, oxidative stress, transcriptomics, and gut microbiota.

## Key findings

- Nano-silver exposure caused muscle, hepatopancreas, and gill tissue damage in crayfish.
- Intestinal microbiota diversity changed, with increased harmful bacteria and decreased beneficial ones.
- Transcriptome analysis revealed 1549 and 1305 differentially expressed genes in muscles and hepatopancreas, impacting pathways like PPAR signaling.

## Abstract

In this study, we evaluated the histopathological alterations, oxidative stress, transcriptomics, and intestinal microbiota changes in different tissue of red swamp crayfish (Procambarus clarkii) following exposure to nano-silver, which has been demonstrated to be an effective antibacterial agent widely used in water disinfection, including the improvement of water quality in aquaculture pond systems. The results indicate that nano-silver exposure adversely affects multiple biological processes in crayfish, suggesting a potential threat to its aquaculture.

There is limited understanding regarding the potential toxicity of nano-silver to crayfish. This study aims to evaluate the histopathological changes, oxidative stress, transcriptomics, and intestinal microbiota changes in different tissues of crayfish after exposure to nano-silver. The results showed that exposure to nano-silver caused pathological changes in the muscles, hepatopancreas, and gills of crayfish. Damage to muscular tissue progressively worsened with increasing concentrations of nano-silver, leading to a gradual widening of the gaps between muscle fibers. Nano-silver enlarged hepatopancreatic lumen and epithelial vacuolation, while the structure of the gills became disorganized, with severe damage to the gill membranes. The activities of peroxidase (CAT), superoxide dismutase (SOD), and glutathione reductase (GSH), as well as the content of malondialdehyde (MDA) in the muscles, hepatopancreas, and gills, were altered due to nano-silver exposure. Furthermore, along with the alteration of intestinal flora, there were alterations in the diversity of intestinal microbiota, an increase in the abundance of Bacteroides and Ca_Bacilloplasma, and a decrease in the abundance of Citrobacter. The abundance of harmful bacteria increased, causing intestinal inflammatory damage. Totals of 1549 and 1305 differently expressed genes (DEG) were found in the muscles and hepatopancreas, according to transcriptome analysis. Significantly affected pathways included the PPAR signaling pathway. These findings provide valuable insights into the use of nano-silver in the aquaculture of crayfish.