Effects of Ultraviolet Radiation on Amphibian Embryonic and Larval Development

Effects of ultraviolet radiation on hatching success, larval survival, and induced abnormalities were tested in three threatened (Hyla arborea, Bufo calamita, and Triturus cristatus) and two common (Rana temporaria and Bufo bufo) amphibians of Sweden. In the laboratory, all species were exposed to artificial UV-radiation (intensities corresponding to midsummer conditions in Sweden) or visible light (controls) for ten days, during which hatching occurred. The effects of ambient levels of UV-radiation on hatching success and survival of B. bufo, R. temporaria, and B. calamita were also determined during outdoor conditions when exposed to three different light regimes: Full solar radiation, UV-filtered sunlight (exposed to photo- synthetically active radiation only) or darkness. In the laboratory experiment, neither eggs nor larvae of R. temporaria, B. bufo, B. calamita, and H. arborea were negatively affected by UV-radiation. However, UV-radiation induced darker pigmentation in tadpoles of H. arborea. Only one species, T cristatus, showed reduced hatching frequencies and lower larval survival when exposed to UV-radiation in comparison to visible light. However, since female T cristatus wrap their eggs in macrophyte leaves, embryos are effectively protected against solar radiation. In the outdoor exper- iments, there were no differences between the light treatments for any of the species. Thus, none of these species are likely to be threatened by moderately increased levels of ultraviolet radiation.