IMpacts of Metallic and ORganic contaminations of the systems Gironde and St Laurent on two Threatened species, the European and American EELs. – IMMORTEEL

Recent tools of molecular biology (RNa-seq Illumina HiSeq 2000) were used to identify in wild eels the level of transcription of genes which is potentially affected by a chronic exposure to contaminants. The acquired information is used to develop a DNA microarray. These data are completed by morphometric, biochemical and histopathological analyses so as to rely the precoce responses to the health of the individuals.

The dominant contaminants in France in the Gironde are represented by Cd, As, Ag, PCB and OCP. Quebec is particularly marked by Hg and PBDE in the Lake St Pierre. The realized broadband sequencing allowed the comparison of 54000 contigs and the identification of 11300 unique genes. A statistical study of correlation by an original method FAMT was developed. The first results allowed to show the major effect of Cd, Ag and lindane on the genes expression.

The studies developed in controlled conditions in the laboratory in a parallel to the analysis of the samples in the field by means of the DNA microarray should allow to characterize and to rank the major factors of the environment or contaminants impacting on the health of eels and their reproductive potentialities in France and in Quebec. Strategies of protection of these endangered species can so be envisaged in both countries.

The project led to scientific presentations during colloques organized between France and Quebec allowing to confront the first results obtained from the field sampling in both countries. Later, the whole project should lead to the production of original results which will be valued in the form of publications in high-level journals of the domain.

The European and American eels are two economically, ecologically and culturally important fish species currently considered in decline and, in the case of the European eel, threatened of extinction. These fish exhibit a complex life cycle. They are born and breed in the Sargasso Sea. Larvae then drift towards the European and American continents, where they metamorphose and invade freshwater systems to grow (yellow eel phase), before departing for a long migration back to where they were born to breed and die (silver eel phase). Among the causes mentioned to explain their decline, global climate change, overfishing, physical obstacles to freshwater migration such as hydroelectric dams and turbines, parasitism and exploitation of the Sargasso Sea have been mentioned. The role of pollution in the decline of these fish is still largely unknown. This research project is a joint initiative of researchers from Québec and France. Its main objective is to examine the relationships between pollution, both inorganic and organic, and the health of Atlantic eels. Indeed, contaminants released in water by urban, industrial, mining and agricultural activities accumulate in yellow eels during their long phase of somatic growth and could affect their growth rate as well as cause tumors and lesions. Furthermore, during their reproductive migration, silver eels mobilize their energy reserves to fuel migration and for gonad maturation. Accumulated contaminants could then be released massively and cause toxicity in the adult or be transferred to embryos. For eels from both continents, this project will examine the relationships between accumulation of contaminants and genetic diversity, health and reproductive potential.