Chronic exposure to environmentally realistic levels of diuron impacts the behaviour of adult marine medaka (Oryzias melastigma)

Yixi Zhou; Xue Han; Yuanyuan Bao; Zihan Zhu; Jiali Huang; Chunyan Yang; Chengyong He; Zhenghong Zuo

doi:10.1016/j.aquatox.2021.105917

Chronic exposure to environmentally realistic levels of diuron impacts the behaviour of adult marine medaka (Oryzias melastigma)

Aquat Toxicol. 2021 Jul 18:238:105917. doi: 10.1016/j.aquatox.2021.105917. Online ahead of print.

Authors

Yixi Zhou¹, Xue Han¹, Yuanyuan Bao¹, Zihan Zhu¹, Jiali Huang¹, Chunyan Yang¹, Chengyong He², Zhenghong Zuo³

Affiliations

¹ Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102, China.
² Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102, China. Electronic address: hecy@xmu.edu.cn.
³ Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102, China; State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, Fujian 361102, China. Electronic address: zuozhenghong@xmu.edu.cn.

PMID: 34333370
DOI: 10.1016/j.aquatox.2021.105917

Abstract

Diuron, a commonly used herbicide and antifouling biocide, has been frequently detected in seawater. The effects of diuron on fish behaviour are currently poorly understood. Herein, the marine medaka (Oryzias melastigma) was continuously exposed to environmentally realistic levels of diuron from the fertilised egg stage to the adult stage. Behavioural evaluation of adult marine medaka indicated that exposure to diuron increased anxiety in the light-dark test and increased predator avoidance. In addition, diuron exposure significantly reduced aggression, social interaction, shoaling, and learning and memory ability. However, only negligible variations in foraging behaviour and in behaviour in the novel tank test were observed. Marine medaka chronically exposed to diuron also showed decreased levels of dopamine in the brain, and changes were observed in the transcription of genes related to dopamine synthesis, degradation and receptors. Exposure to 5000 ng/L diuron caused significant downregulation of the expression of the genes of tyrosine hydroxylase and monoamine oxidase and significantly upregulated the expression of the genes of the D₅ dopaminergic receptor. The relative expression of the D₄ dopaminergic receptor was significantly upregulated in the 50, 500 and 5000 ng/L diuron-treated groups. These findings highlight the significant neurotoxic effects of diuron and the extent to which this may involve the dopaminergic system of the brain. More broadly, this study reveals the ecological risk associated with environmentally realistic levels of diuron in marine animals.

Keywords: Dopamine; Ecotoxicity; Long-term exposure; Neurotoxicity; Pesticide.