A test of the effect of supplemental UV-B radiation on the common frog, Rana temporaria L., during embryonic development

The release of certain man-made chemicals has led to recurrent, seasonal de struction of ozone in the upper atmosphere, allowing more solar radiation i n the UV-B waveband to reach the Earth. Consequently, many amphibians may s uffer increased exposure to UV-B at various stages in their lives. Embryoni c stages of species which spawn in the spring, in shallow, open water, are at high risk of increased exposure. We exposed newly fertilized eggs of one such species, Rana temporaria L., to sunlight with and without supplementa l UV-B. We used outdoor arrays of lamps to simulate the increase in UV-B wh ich might result from previously documented ozone depletion. From immediate ly after fertilization to when hatchlings began feeding, ambient solar UV-B , weighted for DNA-damaging potential, was supplemented by approximate to 8 1% in 1995 and 113% in 1996. These levels of supplementation approximated t he increase in solar UV-B expected to result from losses of 21% and 25%, re spectively, of the total amount of ozone in the atmospheric column, relativ e to pre-ozone-depletion values. We found no evidence that these additions of UV-B radiation increased the incidence of mortality or overt development al abnormality among embryos. We stress the need for appropriate dosimetry in studies of effects of UV-B on organisms.