Chronic exposure to chlorpyrifos disturbs the locomotor behavior, vocal traits, and brain transcriptional profile of Japanese medaka (Oryzias latipes)

Pollution of chlorpyrifos (CPF), a widely utilized organophosphorus pesticide, presents potential risks to aquatic organisms. However, there is still a lack of information regarding the impacts of chronic CPF exposure on the vocal communication of sonic fish. In this study, we examined the effects of CPF (at 0, 0.3, and 3.0 μg/L for 21 days) on the locomotor behavior, vocal traits, and brain transcriptional profile of Japanese medaka ( Oryzias latipes ). The results indicated that exposure to CPF led to a significant reduction in exploratory behavior and social interaction, as well as alterations in the vocal traits of the Japanese medaka. In addition, CPF exposure significantly inhibited acetylcholinesterase activity in the eyes of Japanese medaka. Transcriptome analysis identified 68 and 1014 differentially expressed genes (DEGs) in medaka exposed to CPF at 0.3 μg/L (with 38 genes upregulated and 30 downregulated) and 3.0 μg/L (with 455 genes upregulated and 559 downregulated), respectively. The DEGs in both exposure groups were enriched in pathways associated with cardiac muscle contraction and adrenergic signaling in cardiomyocytes, suggesting that CPF may affect fish muscle function and thus modify their vocal traits. Furthermore, exposure to CPF at 3.0 μg/L also disrupted several critical biological pathways associated with the nervous and endocrine systems, providing insight into the underlying mechanisms responsible for the behavioral and vocal impairments induced by CPF. Given the crucial role that vocal signals play in survival and reproductive success, it is essential to examine further the ecological implications of CPF-induced alterations in the acoustic signals of sonic fish.