Growth, survival and behaviour of larval long-toed salamanders (Ambystoma macrodactylum) exposed to ambient levels of UV-B radiation

Mortality is the most extreme effect of ultraviolet-B radiation (UV-B; 280- 315 nm) on living organisms, but sublethal effects of UV-B may also be impo rtant. Moreover, there may be population differences in response to UV-B, b ut this aspect has not been well explored for animal populations. Amphibian s have been a model system for studying the detrimental effects of UV-B. Ho wever, previous research on the effects of UV-B on amphibians has mainly fo cused on embryos. Few studies have investigated how UV-B affects larvae. We examined potential sublethal effects of UV-B on the long-toed salamander A mbystoma macrodactylum from two different populations. Observational data F rom field transects indicated that larvae are potentially exposed to UV-B i n their natural habitat. Choice tests indicated that larvae select shaded r egions more often than those in the sun, but do not directly distinguish be tween regions with high and low UV-B. Laboratory experiments indicated a su rvivorship difference between individuals from low- and high-elevation site s. When exposed to relatively low levels of UV-B individuals from low-eleva tion sites experienced higher mortality than controls (no UV-B). There were no differences in mortality between UV-exposed and non-exposed larvae from the high-elevation population. Although mortality of UV-B exposed larvae w as not significantly different from controls in the high-elevation populati on: sublethal effects on growth were observed. Individuals from the high-el evation site grew significantly less when exposed to UV-B than individuals shielded from UV-B. Our study demonstrates that larval A. macrodactylum are exposed to UV-B in nature, that UV-B exposure can cause mortality as well as having sublethal effects on growth and that there are potential populati on differences in sensitivity to UV-B radiation.