wes_von_papineäu
Our Roving Correspondent
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GLOBE AND MAIL (Toronto, Ontario) 08 March 08 Tad too much sun for tadpoles (Anne McIlroy)
The frogs of the world are in trouble: A third of 6,000 amphibian species are threatened with extinction and some have already disappeared.
The destruction of habitat is considered the main factor, but scientists are still puzzling over what else is hastening the global decline. A number of studies have suggested that higher levels of ultraviolet radiation - due to ozone depletion - can damage frog DNA. Some of those studies have been criticized, however, because the researchers used such high levels of radiation in their experiments.
Now, a team at the University of Ottawa's Centre for Advanced Research in Environmental Genomics has found that even a slight increase in ultraviolet B radiation - similar to what would hit frog eggs on a spring day in Ottawa - can be disastrous. Many of the tadpoles exposed to low levels had physical abnormalities that would be deadly in the wild, such as kinked tails that forced them to swim in circles or bloated abdomens. It appeared as if they could eat, but not defecate, biologist Vance Trudeau says. Unlike those in the control group, very few of the tadpoles exposed to UVB developed into frogs.
The researchers were trying to simulate a mild increase in UVB radiation, using levels that would be too low to give a person a sunburn. But the tadpoles were exposed 12 hours a day for eight months and couldn't escape as they might have done in the wild by moving to a shady part of the pond. In combination with a well-known pollutant, the UVB was even deadlier.
The work shows that chronic low levels of UVB can have a dramatic impact, says Dr. Trudeau, who conducted the experiment with colleagues Maxine Croteau, David Lean and Christopher Martyniuk.
http://www.theglobeandmail.com/servlet/story/LAC.20080308.SPECTRUM08/TPStory/Environment
The frogs of the world are in trouble: A third of 6,000 amphibian species are threatened with extinction and some have already disappeared.
The destruction of habitat is considered the main factor, but scientists are still puzzling over what else is hastening the global decline. A number of studies have suggested that higher levels of ultraviolet radiation - due to ozone depletion - can damage frog DNA. Some of those studies have been criticized, however, because the researchers used such high levels of radiation in their experiments.
Now, a team at the University of Ottawa's Centre for Advanced Research in Environmental Genomics has found that even a slight increase in ultraviolet B radiation - similar to what would hit frog eggs on a spring day in Ottawa - can be disastrous. Many of the tadpoles exposed to low levels had physical abnormalities that would be deadly in the wild, such as kinked tails that forced them to swim in circles or bloated abdomens. It appeared as if they could eat, but not defecate, biologist Vance Trudeau says. Unlike those in the control group, very few of the tadpoles exposed to UVB developed into frogs.
The researchers were trying to simulate a mild increase in UVB radiation, using levels that would be too low to give a person a sunburn. But the tadpoles were exposed 12 hours a day for eight months and couldn't escape as they might have done in the wild by moving to a shady part of the pond. In combination with a well-known pollutant, the UVB was even deadlier.
The work shows that chronic low levels of UVB can have a dramatic impact, says Dr. Trudeau, who conducted the experiment with colleagues Maxine Croteau, David Lean and Christopher Martyniuk.
http://www.theglobeandmail.com/servlet/story/LAC.20080308.SPECTRUM08/TPStory/Environment