Disruption of male reproductive behavior in threespine stickleback Gasterosteus aculeatus exposed to 17 beta-estradiol.

In past years we have witnessed decreased reproductive capacity in many wildlife species due to exposure to chemicals with endocrine-disrupting properties. In this laboratory experiment male threespine sticklebacks Gasterosteus aculeatus exposed to 17 beta-estradiol (2.0 micrograms/g) dispersed in peanut oil, on days 1, 7, 14, and 21, showed impaired paternal care compared to control fish that were exposed to peanut oil only. There were no differences between the two groups in number of males that built nests or in courtship displays. However, exposed males started nest building significantly later than control males. This study suggests that some but not all essential traits of male reproductive behavior may be altered as a result of exposure to 17 beta-estradiol. To reveal harmful effects of chemicals with suggested reproductive-disrupting properties it is thus important to take a wide variety of variables related to reproductive behavior into consideration.