Environmental Genomics
Environmental health
Chemical pollution and the sex of fish
Chemicals contained within effluents from sewage treatment works are known to be oestrogenic. When discharged into UK rivers, they can cause feminising effects in wild male fish. Similar effects on other wildlife throughout the world, and links with altered reproductive health in humans, have caused international concern and led to comprehensive screening and testing programmes for these endocrine disrupting chemicals (EDCs).
Scientists in the Environmental Genomics programme have explored the impacts
of EDCs focussing on two species of fish:
- roach - found to be sexually disrupted in UK rivers
- zebrafish - a species used extensively for the regulatory assessment of chemicals
The team identified a suite of genes that are key to the process of sexual differentiation. Long-term exposures (greater than two years) to treated sewage effluent and the human contraceptive ethinyloestradiol altered the normal pattern of expression of these genes, inducing all the feminised responses previously seen in wild fish.
This is the first study to demonstrate:
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that chemical pollutants found in domestic sewage effluents induce true intersex (both male and female characteristics) in exposed Indigenous fish.
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that exposure to levels of ethinyloestradiol found in the environment induces complete gender re-assignment in roach. The 'males' that have undergone gender re-assignment have slightly different gonads from normal females raising concerns about their reproductive capability.
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young roach are especially sensitive to the feminising effects of ethinyloestradiol and such exposures appear to pre-sensitise females to oestrogen in later life.
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an extensive suite of potential molecular biomarkers that could be used to assess whether chemicals can adversely affect sexual development of fish.