Suppression and recovery of reproductive behavior induced by early life exposure to mercury in zebrafish

While mercury (Hg)-induced reproductive impairments have been demonstrated in fishes, the effects of exposure to Hg 2+ during early life stages on the reproductive behavior in adulthood and the persistency of these effects in the next generation remain largely unknown. In this study, zebrafish embryos were exposed to 0.6, 3, or 15 μg·L −1 Hg 2+ for 5 days and then reared for an additional 115 days in clean water, from which embryos were obtained and cultured in clean water for 120 days as the F 1 generation. Increased Hg levels in brains and decreased survival and growth were observed in individuals exposed to Hg 2+ during early life stages. Early life exposure to Hg 2+ reduced the frequency of touching in males as well as the frequency and duration of visits to the spawning area by females, males, or both sexes simultaneously, and resulted in lesser spawning and fertilization. Moreover, early life exposure to Hg 2+ interfered with the transcription of genes encoding neuropeptides and hormones related to reproduction, which could be responsible for diminished sexual behavior and reduced reproductive outcomes. In the F 1 generation, such alterations were not observed in either females or males, indicating that the disruption of normal patterns of reproductive behavior caused by early life exposure to Hg 2+ did not persist and was recovered. Overall, this study demonstrated that exposure to Hg 2+ during early life stages suppressed the reproductive behavior of adult fish but this disruption could be recovered in the F 1 generation.