| Summary: | International audience The European eel (Anguilla anguilla) population has received considerable attention in recent decades due to its significant decline. This catadromous species presents a facultative diadromy and glass eels display a large panel of estuarine migratory tactics, ranging from residency in marine water, to various degrees of upstream colonization through estuarine and freshwater ecosystems. These different patterns of migration can have a strong impact on the fate of the population because individuals remaining downstream mostly develop into males, whereas individuals colonizing upstream develop mainly into females. Recent results suggest that glass eels presenting a low probability to migrate in experimental facilities may be more stressed or more sensitive to stress than migrant individuals. Estuaries are considered stressful environments and represent a major sink for variouscontaminants usually considered as powerful stressors depending on their concentrations. Among these chemicals, benzodiazepines, found in relatively high concentrations in effluents of wastewater treatment plants, can induce a number of neuroendocrine alterations in exposed fish. However, paradoxically, they also may counteract the stress responses in fish due to their anxiolytic effect.The aim of this work was to investigate the effect of the stress and diazepam at environmental doses on the European glass eel by developing stress markers. Stress hormones analysis were developed by LC-MS-MS to determine cortisol, cortisone, 11- deoxycortisol, and 11-deoxycorticosterone production in glass eel individuals. In addition, transcriptomic markers were detected using a non-targeted approach, by RNAseq. These molecular and endocrine markers were analyzed on glass eels contaminated or not with diazepam, and exposed or not to a 2 minutes mechanical stress. Both stress markers were monitored with time (after 15, 30, 60 and 120 min) to evaluate the combined effect of stress and diazepam in glass eel. The developed stress markers ...
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