Ann. Zool. Fennici 37: 51–58 ISSN 0003-455X Helsinki 14 April 2000 © Finnish Zoological and Botanical Publishing Board 2000 Effects of ambient UV-B radiation on early development of the common frog ( Rana temporaria) embryos in the subarctic Juha Merilä, Anssi Laurila & Maarit Pahkala Merilä, J. & Pahkala, M., Department of Population Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 d, SE-752 36 Uppsala, Sweden Laurila, A., Department of Population Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 d, SE-752 36 Uppsala, Sweden; and Integrative Ecology Unit, Divison of Population Biology, Department of Ecology and Systematics, University of Helsinki, P.O. Box 17, FIN-00014 University of Helsinki, Finland Received 15 September 1999, accepted 12 November 1999 Merilä, J., Laurila, A. & Pahkala, M. 2000: Effects of ambient UV-B radiation on early development of the common frog (Rana temporaria) embryos in the subarctic. — Ann. Zool. Fennici 37: 51–58. Several recent field experiments have demonstrated that ambient ultraviolet-B radia- tion (UV-B; 280–315 nm) may cause severe mortality of amphibian embryos. We in- vestigated the effects of ambient UV-B on early embryonic performance of the com- mon frog (Rana temporaria) in subarctic Finland (ca. 69°03´N, 20°50´E), where levels of UV-B radiation during the egg laying period are roughly twice as high as those in southern Fennoscandia. We found no evidence for decreased embryonic mortality, de- creased frequency of developmental anomalies or improved growth performance of embryos shielded from UV-B as compared with embryos exposed to ambient levels of UV-B. Our results concur with the results of earlier studies with this species conducted in more southern populations, and suggest that current UV-B levels alone are not likely to pose significant threat for the well being of subarctic common frog populations. 1. Introduction In recent years, many amphibian populations have undergone declines and range reductions (e.g. Semb-Johansson 1989, Wake 1991, Pounds & Crump 1994, Drost & Fellers 1996, Fisher & Shaf- fer 1996, Laurance et al. 1996, Lips 1998). Hy- pothesised causes for these declines include habi- tat destruction, introduced exotic species, pollu- tion, acidification and increased ultraviolet-B ra- diation (Wake 1991, Blaustein & Wake 1995, Licht 1996). The fact that the declines have taken place in diverse locations, including undisturbed habitats, has prompted a concern (e.g. Blaustein