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(18-49) Effects of Gonadal Inter-sex on Fish Reproduction. Metcalfe, Chris1, Kavanagh, Richard1, Balch, Gordon1, Kiparissis, Yiannis*,1,2, 1 Environmental and Resource Studies, Trent University, Peterborough, Ontario2 School of Environmental Studies, Queen's University, Kingston, Ontario ABSTRACT- A variety of natural and synthetic compounds are able to mimic the effects of female estrogen hormones in vertebrates and have the potential to interfere with sexual development and reproduction. Many studies have focused on identifying endocrine disruptor substances (EDS) that are capable of inducing biological responses in fish, including alterations to gonadal development. In field surveys of immature (YOY and 2+) white perch (Morone americana) conducted in the lower Great Lakes in 1998-2000, gonadal intersex was noted in male white perch from various regions in Lake Ontario, Lake Erie and Lake St. Clair. The highest prevalence of 80% occurred in white perch captured in 2000 in the Coote's Paradise region of Hamilton Harbour, Ontario. It is difficult to determine from field studies whether intersex has an effect on the reproductive performance of fish. Therefore, Japanese medaka (Oryzias latipes) were used as a laboratory model to evaluate the effects of intersex on reproductive performance. Medaka were exposed to 17 Key words: Endocrine-disruption, Field survey, intersex, reproductive performance |
-ethinylestradiol (EE2) from 2 days post-hatch to 5 months of age and fish were then assessed for reproductive success using behavioural and reproductive endpoints. Reproductive trials were conducted between: i) Exposed males and unexposed females, ii) Unexposed males and exposed females. In trials with exposed males and unexposed females, exposure to EE2 at concentrations of 0.2 and 2 ng/L did not alter reproductive success relative to the control treatment. However, reproductive success was reduced significantly in treatments with 10 ng/L of EE2. A histological survey of gonadal development in exposed males indicated that there were a small number of males with intersex (i.e. testis-ova) in the 2 ng/L treatment and 57% intersex males in the 10 ng/L treatment. However, when normal and intersex males were evaluated for reproductive success, several intersex fish reproduced successfully and there were no significant differences between the reproductive success of intersex and normal males in the 2 ng/L and 10 ng/L treatments. Overall, these studies indicate that fish exposed to estrogens have a reduced capability for reproduction, no matter if they do or do not have gonadal inter-sex.