Introduction
1 Introduction
Pyrethroid pesticides, such as deltamethrin (DM), are widely used in agriculture and aquaculture due to their high insecticidal activity and relatively low toxicity compared to older pesticides. DM is effective against a broad spectrum of pests, making it a popular choice for pest and disease control in aquatic environments (Guardiola et al. (2014)). However, DM frequently enters rivers and lakes through surface runoff and wastewater discharge, posing risks to aquatic organisms. Fish are particularly vulnerable because they lack efficient mechanisms to metabolize and degrade DM, leading to toxic effects even at environmentally relevant concentrations (Wu et al. (2020)).
Goldfish (Carassius auratus) are a common freshwater species widely distributed in many water bodies and are often used as a model organism in toxicology research (Blanco et al. (2018)). Their ecological relevance, manageable size, and ease of maintenance make them suitable for laboratory experiments, while their physiology provides insight into potential impacts of environmental contaminants on aquatic species. Prior studies have shown that DM exposure can induce oxidative stress, apoptosis, and immune dysfunction in various fish species, but the molecular mechanisms underlying these effects are not fully understood (Zhou et al. (2021)).
The aim of this study was to investigate the effects of acute, environmentally relevant concentrations of DM on goldfish kidney transcriptomes and intestinal microbiota. Nine healthy goldfish were randomly assigned to three treatment groups: 0 µg/L control, 0.2 µg/L DM, and 2 µg/L DM, with three fish per group. Fish were exposed for 96 hours under controlled laboratory conditions. Kidney tissues were collected and RNA extracted for high-throughput RNA-sequencing to identify differentially expressed genes and characterize affected biological pathways, including apoptosis, immune response, and drug metabolism. Additionally, intestinal contents were collected to assess changes in microbial composition using 16S rRNA sequencing.
By combining transcriptomic and microbiota analyses, this study provides an integrative understanding of how DM affects fish at both the molecular and microbial levels. The results are expected to reveal key pathways disrupted by DM exposure and highlight the broader impacts of environmental contaminants on fish physiology and gut microbial communities (Zhou et al. (2021)). This work contributes to the growing field of aquatic toxicology by providing detailed molecular insights into DM-induced toxicity in a widely studied model species.