Swedish frogs confused ...

Those sex changing frogs are back!

Former State opposition leader Lawrence Springborg will be relieved to know that there is a study in Sweden that bears out his comments that pollutants can turn males into females. Obviously this study did not involve a comparison of potable vs. recycled water and the scientists will have to debate whether the RO processes currently available can remove all pollutants from recycled water.

From Agence France-Presse

Pollutants changing male frogs into female frogs

1 March 2007

Frogs that started life as male tadpoles were changed in an experiment into females by oestrogen-like pollutants similar to those found in the environment, according to a new study.

The results may shed light on at least one reason that up to a third of frog species around the world are threatened by extinction, suggests the study, set to appear in the journal Environmental Toxicology and Chemistry in May.

In a laboratory at Uppsala University in Sweden, two species of frogs were exposed to levels of oestrogen similar to those detected in natural bodies of water in Europe, the United States and Canada.

The results were startling: whereas the percentage of females in two control groups was under 50 per cent - not unusual among frogs - the sex ratio in three pairs of groups maturing in water dosed with different levels of oestrogen were significantly skewed.

Even tadpoles exposed to the weakest concentration of the hormone were, in one of the two groups, twice as likely to become females.

The population of the two groups receiving the heaviest does of oestrogen became 95% female in one case, and 100 per cent in the other.

"The results are quite alarming," said co-author Cecilia Berg, a researcher in environmental toxicology. "We see these dramatic changes by exposing the frogs to a single substance. In nature there could be lots of other compounds acting together."

Earlier studies in the United States, Berg explained, linked a similar sex-reversal of Rana pipiens male frogs - one of the two species used in the experiment - in the wild to a pesticide that produced oestrogen-like compounds.

"Pesticides and other industrial chemicals have the ability to act like oestrogen in the body," Berg said.

The study does not measure the potential impact of pollutant-driven sex change for frog species, but the implications, said Berg, are disquieting.

"Obviously if all the frogs become female it could have a detrimental effect on the [frog] population,"she said.