Toxicity of dietary mercury to cultured fish: implications for fish health, seafood safety and the influence of dietary selenium (200934)

Toxic effects of methylmercury (MeHg) are of major concern for aquatic food chains, aquaculture and for consumers of farmed and wild caught fish. The proposed project is a bilateral cooperation between NIFES, Norway and NRIFS, Japan focussing on seafood s afety and aims to assess the dietary toxicity of MeHg to cultured fish. In particular, we focus on molecular mechanisms that determine the assimilation and elimination of dietary MeHg, including the influence of the MeHg antagonist selenium (Se) and toxic ological effects in early life stage fish arising from MeHg exposure. In many cases, early life stages exhibit a higher degree of toxicological sensitivity to contaminants than the adult life stages, and detrimental effects from MeHg exposure to the devel oping central nervous system (CNS) have been well documented. Zebrafish (Danio rerio) will be used as a model system to assess the significance of maternal transfer of MeHg to the neurological development of embryos. Sensitive developmental pathways will be identified using gene expression profiling techniques and anchored to zebrafish phenotype using neurobehavioural assays. Furthermore, a combined genomic and kinetic approach will be used to assess the transfer of MeHg from fishmeal based feed to zebraf ish, determine molecular mechanisms involved in MeHg uptake, elimination and toxicity and identify candidate molecular markers of exposure and effect. Markers identified in zebrafish will be validated in commercially important Atlantic cod (Gadus morhua L .). The project will generate knowledge of relevance for future risk assessments of mercury in both feed and food which form the basis of risk management in terms of international legislation, including maximum permitted levels of mercury in feed and food .