Frog Transformations: The Sex Reversal Without Permission

More than one third of species of frogs are estimated to be reaching alarming levels of extinction.

Understanding that frogs belong to the taxonomic order Anura, may leave one wondering just how does extinction happen to the order that contains over 5,000 species.

While simplified, one viewpoint suggests that various pollutants in the environment predispose frogs to detrimental ecological effects.

According to the latest laboratory findings at the Uppsala University in Sweden, male tadpoles transform into female forms as a result of various estrogen-containing pollutants found in natural fresh water ecosystems.

To conduct the study, two species of frogs were exposed to varying levels of estrogen-containing compounds, mimicking the estrogen levels found in nature.

The findings portrayed that the tadpoles receiving highest levels of estrogen transformed from male to female form 95 to 100 percent of the time. One of the groups exposed to the tiniest amounts of estrogen was also twice as likely to experience sex reversal.

Since the frog skin is permeable to water, oxygen and carbon dioxide, the frogs seem to be exceptionally sensitive to environmental toxins. The blood vessels near the skin surface serve as a direct pathway for pollutants to reach bloodstream, permanently altering their reproductive system.

A researcher at the Uppsala University, Cecilia Berg, confirmed that "Pesticides and other industrial chemicals have the ability to act like estrogen in the body."

The direful levels of estrogen-containing pollutants found in natural water systems seem to be a direct result of several contraceptive methods used by human populations world wide. One of the common pollutants is the oestrogen ethynylestradiol contraceptive pill.

Additionally, Burg affirmed, "We see these dramatic changes by exposing the frogs to a single substance. In nature there could be lots of other compounds acting together."

Consequently, disregarding the harmful effects of pollutants and their naturally occurring interactions could substantially accelerate the issue of extinction in frogs.

SOURCES:

1.

http://en.wikipedia.org/wiki/Frogs

2. Scenta, "Pollution Causes Sex Change in Frogs." Netscape. URL:

(http://www.netscape.com/viewstory/2007/02/25/pollution-causes-sex-change-in-frogs/?url=http%3A%2F%2Fwww.scenta.co.uk%2Fnature%2Fnews.cfm%3Fcit_id%3D1552195%26FAArea1%3Dwidgets.content_view_1&frame=true)
3.

Marlowe Hood, "Pollutants Change 'He' Frogs Into 'She' Frogs." AFP. URL:(http://news.yahoo.com/s/afp/20070227/sc_afp/scienceenvironmentanimalssexfrogs;_ylt=Al987VQRc9UBJeyD1R.pirkPLBIF)