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Worldwide, animal and plant diversity is decreasing, and amphibians are among the animals disappearing most rapidly. It is estimated that nearly 40 per cent of all known amphibian species are endangered. The main cause is changes in their habitat, but pollution, diseases and climate change are also contributing to the extinction.
In agriculture, a huge variety of pesticides are used, for example against weeds and insects. These chemicals then leach into nearby ponds where frogs lay their eggs. Some of these substances have hormone-disrupting effects and are known as 'endocrine-disrupting chemicals' or EDCs. Known EDCs include Bisphenol A, DDT and PCBs (polychlorinated biphenyls).
Scientists - Scotland - England - Umeå - Researchers
With scientists from Scotland, England and Umeå, researchers at Uppsala University's Department of Environmental Toxicology have studied how one of these endocrine-disrupting pesticides, linuron, affects the life cycle of the West African clawed frog, Xenopus tropicalis. After exposing tadpoles to a concentration similar to that measured in the natural environment, and through comparison with control groups and a control substance, researchers found that the tadpoles developed ovaries to a greater extent than testicles. The researchers were also able to show the shift in the male-female sex ratio towards an increased proportion of females by analysing gene expression in tadpoles.
Once the frogs reached adulthood, the researchers showed that the males' fertility had been impaired and that certain gender-specific features had become more like females'. The researchers believe that the likely explanation for these observations is that...
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