Effects of solar UV-B radiation on embryonic development in Hyla cadaverina, Hyla regilla, and Taricha torosa

Exposure to solar ultraviolet-B (UV-B) radiation leads to increased embryonic mortality in some amphibians. It has been hypothesized that sensitivity to UV-B may contribute to the population declines of some species. To better understand the effects of ambient UV-B on embryo development and survival, embryos from three lower latitude (34 degrees N), lower altitude (290 m) amphibian species were studied at natural breeding sites in the Santa Monica Mountains near Los Angeles, California. We compared embryonic development and hatching success in Hyla regilla, Hyla cadaverina, and Taricha torosa embryos exposed to ambient solar UV-B radiation with those shielded from solar UV-B. A large percentage of H. regilla embryos survived when exposed to and protected from UV-B. Neither hatching success nor rates of development were affected by solar UV-B. conversely, H. cadaverina and T. torosa embryos displayed high rates of embryonic mortality when exposed to solar UV-B Elimination of solar UV-B significantly increased hatching success in both of these species, but had no effect on rates of embryonic development. These data suggest that under natural conditions, solar UV-B radiation influences embryo survival in both Hyla cadaverina and Taricha torosa. Additional studies are required to determine whether susceptibility to UV-B affects these species at the population level.