Researchers have found new evidence that ultraviolet radiation from the sun can cause death and deformities among some salamanders, providing a possible clue to why amphibians may be declining.

A team led by zoologist Andrew Blaustein of Oregon State University conducted experiments this past summer in which long-toed salamanders were reared in enclosures in their normal breeding ponds in Oregon's Cascade mountains. One group was shielded under ultraviolet-B (UV-B) filters, the other received the full spectrum of ambient sunlight.

Virtually all of the eggs shielded from UV-B hatched successfully. But in the group exposed to full sunlight, 85 percent of the eggs died, according to a report in the Dec. 9 issue of the Proceedings of the National Academy of Sciences. Of those that hatched, more than 90 percent were deformed or suffered arrested growth.

UV-B may act alone in causing developmental abnormalities or it may work in conjunction with contaminants such as pesticides, according to Blaustein, who has been studying the impact of increased ultraviolet radiation on frogs, toads and salamanders for several years. The study also suggests that UV-B weakens the immune response and can make animals more susceptible to pathogens and parasites.

The concern, says Blaustein, is that Earth's thinning ozone layer is amplifying all of these effects.

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