The eects of solar UV-B radiation on embryonic mortality and development in three boreal anurans Rana temporaria, Rana arvalis and Bufo bufo) Jani H akkinen, Seppo Pasanen * , Jussi V.K. Kukkonen Department of Biology, University of Joensuu, P.O. Box 111, Joensuu 80101, Finland Received 21 December 1999; accepted 21 May 2000 Abstract Many species of amphibians have experienced population and range reductions. It has been hypothesized that sensitivity to UV-B may contribute to the population declines of some amphibian species. We performed ®eld exper- iments to measure the eects of solar UV-B on the hatching success of three Finnish anuran species, the common frog Rana temporaria), moor frog Rana arvalis) and common toad Bufo bufo). Further, the eects of natural UV-B ra- diation on survival of the tadpoles of the same three species of anurans were tested. A signi®cant percentage of R. temporaria and B. bufo embryos survived when exposed to and protected from solar UV-B and hatching success was not aected by solar radiation. Elimination of solar UV-B signi®cantly increased the hatching success of R. arvalis, but embryonic mortality was high in both treatments. The data indicates that under natural conditions, solar UV-B ra- diation in¯uences embryo survival in R. arvalis, but has no eect on R. temporaria and B. bufo. Solar UV-B radiation had no eect on R. temporaria and R. arvalis tadpoles, but elimination of UV-B signi®cantly increased survival of B. bufo tadpoles. It seems that ambient UV-radiation levels have no eect on R. temporaria but may aect R. arvalis and B. bufo at dierent developmental stages. Ó 2001 Elsevier Science Ltd. All rights reserved. Keywords: UV-radiation; Amphibian; Survival; Embryos; Tadpoles 1. Introduction Populations of many amphibian species have under- gonedeclinesandrangereductionsinthelastdecadewith some species apparently becoming extinct Barinaga, 1990;BlausteinandWake,1990;Wake,1991;Blausteinet al., 1994). The cause and eect factors of this global phenomenon may be many including destruction and al- teration of habitats Baard, 1989), chemical pollution Vardia et al., 1984; Licht, 1985; Carey and Bryant, 1995; Jung and Jagoe, 1995), introduction of exotic predators Hayes and Jennings, 1986; Fellers and Drost, 1993), pathogens Kiesecker and Blaustein, 1997), climate changes Pounds and Crump, 1994), acid precipitation Freda and Dunson, 1985; Freda, 1986; Sadinski and Dunson, 1992), and natural population ¯uctuation Pechmann et al., 1991; Pechmann and Wilpur, 1994). Recent studies have suggested that solar UV-B radiation UV-B; 290±320 nm) increases embryonic mortality in some species of amphibians at higher altitudes and lati- tudesBlausteinetal.,1994,1997;GrantandLicht,1995; LichtandGrant,1997;NaglandHofer,1997;Lizanaand Pedraza, 1998). Since 1974, the Zoological Museum of Helsinki University has monitored amphibian populations at certain research sites and according to these studies, populations of all ®ve Finnish amphibian species Rana Chemosphere 44 2001) 441±446 * Corresponding author. Tel.: +358-13-251-3575; fax: +358- 13-251-3590. E-mail address: seppo.pasanen@joensuu.® S. Pasanen). www.elsevier.com/locate/chemosphere 0045-6535/01/$ - see front matter Ó 2001 Elsevier Science Ltd. All rights reserved. PII:S0045-653500)00295-2