Chemical determine fish sex

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'Toxic stew' of chemicals causing male fish to carry eggs in testes

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Genetic secrets of sex-changing fish discovered - BBC Science Focus Magazine

Jump to navigation. In the early s, British researchers at Brunel University in Uxbridge noticed that male fish living downstream from a sewage treatment plant near London had testes laden with eggs. The male fish had become hermaphrodites also known as intersex — having the sexual characteristics of both males and females. Subsequently, when caged trout were placed downstream from sewage treatment plants in several British rivers, the males were discovered to have elevated levels of a protein called vitellogenin in their blood. Vitellogenin is the protein responsible for making egg yolks in female fish. Ordinarily, little, if any, vitellogenin is found in male fish. Male fish have a gene which, if triggered by oestrogen female sex hormone can produce vitellogenin, but male fish ordinarily lack sufficient oestrogen to trigger that gene.
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Sex-determination system

All rights reserved. About 85 percent of male smallmouth bass collected in national wildlife refuges in the Northeastern U. Pollutants that mimic sex hormones are the suspected culprit. Fish in wildlife refuges are feminized, probably by hormone-skewing pollution.
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A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most organisms that create their offspring using sexual reproduction have two sexes. Occasionally, there are hermaphrodites in place of one or both sexes.
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