Vitellogenin-like gene expression in freshwater amphipod Gammarus fossarum (Koch, 1835): functional characterization in females and potential for use as an endocrine disruption biomarker in males
Résumé
The induction of vitellogenin (Vtg) synthesis is widely accepted as a biomarker of estrogenic exposure in male and juvenile fish. The quantification of Vtg synthesis has emerged as interesting endpoint to assess endocrine disruptor effects in crustaceans. However, studies reporting induction of Vtg in male crustaceans are lacking. In this study, we studied the expression of the Vtg gene in a freshwater amphipod, Gammarus fossarum, using calibrated real-time reverse transcription polymerase chain reaction (real-time RT PCR). In first, we described the basal pattern of expression in healthy organisms, males and females, at different reproductive moult stages. Females expressed from 200 to 700 times more Vtg transcripts than males. Females displayed a significant elevation of Vtg mRNA level at the end of inter-moult phase and at the beginning of pre-moult phase. Second, male gammarids were exposed to nonylphenol (0.05, 0.5, 5 and 50 μg.L−1) and to the anti-androgen cyproterone (1, 10, 100 and 1 000 μg.L−1) for 2, 4, 8 and 16 days. Both chemicals altered the pattern of inter-individual variability of Vtg gene expression in males with strong induction in some individuals. To the end, the impact of urban wastewater treatment plants (WWTP) on male Vtg gene expression was assessed in organisms transplanted in the field during in situ bioassay campaigns within three different watersheds. Induction of Vtg mRNA level was observed in males transplanted downstream of WWTP effluent discharge in two of the three studied sites.