Effects of ultraviolet radiation on toad early life stages.
BACKGROUND
Exposure to harmful levels of ultraviolet-B radiation (UVB), a component of solar radiation, has been suggested as a potential cause of amphibian declines.


METHODS
We measured solar radiation (UVB, ultraviolet-A, and visible) wavebands in breeding ponds of Bufo boreas (boreal toad, a montane species that has undergone severe population declines) and Bufo woodhousii (Woodhouse's toad, a plains toad that has not experienced declines)and examined tolerances of these species to simulated solar UVB exposures in the laboratory.


RESULTS
We found larvae of both species to be tolerant of simulated solar UVB in excess of solar UVB levels observed in their breeding ponds. B. boreas tadpoles were more tolerant of simulated solar UVB exposure than B. woodhousii tadpoles, possibly because of greater amounts of photoprotective melanin in B. boreas skin.


CONCLUSIONS
UVB levels observed in B. boreas habitats do not currently appear to constitute a threat to the survival of these animals; however, long-term (> 1 month) exposure to UVB levels comparable to levels associated with the water interface appears to reduce survival in B. woodhousii tadpoles. Therefore, future increases in surface and water column UVB radiation in bufonid habitats might pose significant survival risks to B. boreas or B. woodhousii populations.
Little
Edward E
EE
U.S. Geological Survey/Columbia Environmental Research Center, 4200 New Haven Road, Columbia, MO 65201, USA. edward little@usgs.gov
Calfee
Robin D
RD
Fabacher
David L
DL
Carey
Cynthia
C
Blazer
Vicki S
VS
Middleton
Elizabeth M
EM
D000818:Animals; D002025:Bufonidae / Q000196:embryology / Q000254:growth & development*; D004777:Environment; D007814:Larva / Q000254:growth & development / Q000528:radiation effects; D011836:Radiation Tolerance; D013472:Sunlight / Q000009:adverse effects; D014466:Ultraviolet Rays / Q000009:adverse effects*