Pollutants turn male frogs into female frogs

According to this study, the research results can explain at least one reason why one-third of frog species in the world are in danger of extinction.

In the lab at Sweden's Uppsala University, two species of frogs are exposed to estrogen at doses equal to the amount of estrogen found in natural water sources in Europe, the United States and Canada.

The results were startling : while the percentage of females in the two experimental groups was less than 50% - not unusual in frogs - the sex ratio in 3 pairs of 2 groups living in water containing the dose. Different estrogens have been significantly changed.

Photograph of Philautus Femoralis , a rare tree frog, in Horton Plains National Park (Sri Lanka).These frogs began life as male tadpoles, which were turned into females in experiments by estrogen-like contaminants, substances similar to those found in external environments.

Even tadpoles exposed to this hormone in the lowest doses, in one of the two groups, are also twice as likely to become females as normal.

The populations of two frog groups exposed to the highest estrogen levels have become almost identical at 95% in a group, and are 100% female in the other group.

'These results are alarming,' said co-author Cecilia Berg, an environmental toxicologist. 'We see these very big changes when frogs are exposed to a single substance. In nature, there may be many other compounds that work together. '

Ms Berg explained that previous studies in the United States indicate the cause of similar sex reversal in Rana pipien male frogs - one of the two species used for experiment - live in the wild. because of pesticides, drugs that produce estrogen-like compounds.

"Pesticides and other industrial chemicals are capable of acting like the hormone estrogen in the body," said Ms Berg . "That's what prompted us to do this experiment,"

The other frog species was tested as a popular frog species in Europe named Rana temporaria. Some sexually changed males become females with complete functions, while other sexually modified females have ovaries but do not have egg tubes, making them infertile, Ms. Berg explain.

She said the study did not measure the potential effects of frog sex change caused by pollutants, but the implications of this study make people worry.'Of course if all the frogs became children, it would have a negative effect on this population,'

She added that the only remedy now is to improve the disposal of waste in areas where frogs and other amphibians may be affected, to remove the amount of estrogen from preventive drugs. pregnancy and other industrial pollutants.

Thanh Van