In nature, ultraviolet radiation from sunlight is not the amphibian killer scientists once suspected.
Naturally occurring murky water and females who choose to lay their eggs in the shade keep embryos of one of the nation's most UV-sensitive amphibian species out of harm's way most of the time, new research shows. Less than 2 percent of the embryos of the long-toed salamander received lethal doses of UV across 22 breeding sites across nearly 8 square miles (20 square kilometers) in Washington state's Olympic National Park.
For a second amphibian, the Cascades frog known to be among the least UV-sensitive Pacific Northwest species the researchers found no instances where eggs received lethal doses.
Declines in amphibian populations around the globe remain a real concern, but the cause is not increasing UV radiation, according to Wendy Palen, lead author and a Simon Fraser University ecologist who conducted the research while earning her doctorate from the UW, and Daniel Schindler, UW professor of aquatic and fishery sciences. The work is being published in the Proceedings of the National Academy of Sciences May 25, and is now available online.
"These findings don't contest hundreds of studies demonstrating the harmful effects of UV radiation for many organisms, including humans," Palen says. "Rather, it points out the need to understand where and when it is harmful."
Papers published in the late 1990s and early 2000s raised the alarm that UV exposure was triggering amphibian declines, with many of the findings based on Pacific Northwest amphibians. Previous research wasn't wrong: some species proved extremely sensitive to UV radiation with especially high mortality for eggs and larvae as shown in physiological studies done mostly in highly controlled laboratory experiments or at just one or two natural ponds or sites, Palen says.
But conditions in labs or a few isolated sites are not what the animals t
|Contact: Sandra Hines|
University of Washington