Transcriptomic Analysis Reveals Developmental Toxicity Induced by Environmentally Relevant Concentrations of Fenvalerate and Sulfamethoxazole in Embryo and Juvenile Marine Medaka (Oryzias melastigma, McClelland, 1839)

The abuse of pesticides and antibiotics has increased the potential risks for coastal marine organisms. Thus, the evaluation of the toxic effects on and mechanisms of both marine organisms is very important. This study investigated the developmental toxicity and mechanisms of FEN and SMX in embryo and juvenile marine medaka. The results showed that when embryos were exposed to FEN (0.3, 30 μg·L^-1) or SMX (1, 10 μg·L^-1) for 12 days, there were no significant effects on hatching, malformation, or mortality rates. However, the combined exposure to F-S (F-0.3 + S-10) significantly reduced the hatching rate and increased the malformation rate and mortality rate. Histological analysis revealed that there were no pathological changes in the tissues of juvenile marine medaka, indicating no sensitivity at low doses. A transcriptome analysis of tissues exposed to F-S identified 1135 differentially expressed genes (DEGs), which was significantly more than that for single exposure groups (FEN: 499 DEGs; SMX: 138 DEGs). KEGG enrichment analysis highlighted that growth-related pathways were disturbed, such as steroid biosynthesis, the cell cycle, fatty acid metabolism, etc. Our findings suggest that the combined exposure to FEN and SMX induces developmental toxicity by regulating the dysregulation of metabolic and proliferative pathways, highlighting the ecological risks posed to marine organisms in polluted estuaries.