Endocrine disruption in fish : Effects of 17α-ethinylestradiol exposure on non-reproductive behavior, fertility and brain and testis transcriptome

Sammanfattning: Aquatic environments are the end recipient for most anthropogenic chemical pollutants. One common chemical pollutant found in the aquatic environment is 17α-ethinylestradiol (EE2), a synthetic estrogen used in contraceptive pills. EE2 is found in sewage treatment plant effluents and surface waters in concentrations from non-detectable up to 300 ng/L. EE2 has the ability to bioaccumulate and is more than 10 fold more potent in fish than the natural counterpart estradiol. Exposure has led to skewed sex ratios, decreased egg and sperm production, and altered reproductive behavior.  The aim of this thesis was to investigate the effects of EE2 exposure on non-reproductive behavior and fertility in fish. We found that zebra fish exposed to low concentrations of EE2 during development showed increased anxiety-like behavior and decreased fertility that were persistent in adulthood, even after a long remediation period in clean water. The altered behavior and lowered fertility were accompanied by alterations in the testis and brain transcriptome of possible significance for the behavior and fertility effects. The zebrafish was also used in adult exposures of EE2 and citalopram, alone and in combination to investigate if behavioral effects can be detected at very low concentrations, and if so, if the two compounds would interact and affect the behavioral outcome. Anxiety-like behavior was altered by EE2 and the two compounds in combination affected the outcome of each other. Further, when developmental exposure of progeny to wild caught three spined stickleback was used as a link between laboratory fish and natural fish populations, EE2 was found to decrease the anxiety-like behavior in the adult stickleback as well as cause ovotestis and intersex, feminization and sex reversal of genetic males. In conclusion, fertility and non-reproductive behaviors in the zebrafish and three spined stickleback are sensitive to EE2 exposure and effects from developmental exposures seem to be persistent.  Fertility and behavior are of high ecological significance for fish and alterations due to EE2 exposure might have negative effects on population fitness. The persistent alterations in the transcriptome of the zebrafish testis and brain lead to generation of hypotheses of mechanisms involved in the behavior and reproductive phenotypes caused by developmental exposure to EE2.