Identification of xenoestrogenic effects by vitellogenin transcription up-regulation in commercial fish species of the Bay of Biscay
Supervisor:
Endocrine disrupting chemicals (EDCs) have been recognized as a serious environmental concern due to their deleterious effects on living organisms and their ubiquitous distribution in the environment. Xenoestrogens are a class of EDCs capable of mimicking natural oestrogens, a key reproductive hormone in female vertebrates. As such, exposure to xenoestrogens can cause a host of adverse effects in teleost fish, including reproductive and developmental impairments. An efficient and sensitive biomarker of xenoestrogen exposure in fish is the upregulation of vitellogenin expression in male individuals, resulting in an increase in hepatic vtg mRNA levels. Xenoestrogens often originate from anthropogenic sources and enter the marine environment via industrial, agricultural and waste water treatment effluents. Therefore, xenoestrogenic pollution and its effects on aquatic organisms are significant in coastal and estuarine areas. However, xenoestrogens are highly persistent and can be transported to more remote parts of the hydrosphere such as off shore and deep sea ecosystems. The aim of this study was to quantify and assess xenoestrogen exposure in six teleost species of commercial and biological interest from both coastal/estuarine environments and offshore marine environments in the Bay of Biscay: the thicklip grey mullet, Chelon labrosus, the common sole, Solea solea, the Atlantic mackerel, Scomber scombrus, the Atlantic horse mackerel, Trachurus trachurus, the European pilchard, Sardina pilchardus, and the European anchovy, Engraulis encrasicolus. Fragments of the vitellogenin were successfully amplified and sequenced in the Atlantic mackerel, the Atlantic horse mackerel, the European pilchard and the common sole, providing valuable transcriptomic resources for further studies investigating these species’ reproductive physiology and toxicological risks. Hepatic vtg transcription levels were quantified in male fish by qPCR. vtg up-regulation in males was detected in the common sole, and to a lesser extent in the thicklip grey mullet and the European pilchard. Hepatic vtg up-regulation was not reported in the Atlantic mackerel, the Atlantic horse mackerel and the European anchovy. In summary, vtg up-regulation in males, a biomarker of xenoestrogen exposure, was more prevalent in estuarine and coastal species, suggesting that xenoestreogens, being more abundant in these areas, present a greater threat to these species.