Chronic Exposure of Rana pipiens Tadpoles to UVB Radiation and the Estrogenic Chemical 4-tert-octylphenol

Abstract

While adverse effects of exposure to ultraviolet B radiation (UVBR) and environmental pollutants on amphibians have been documented, few studies examined the effects of interactions between environmental stressors on amphibian health. Here the impacts of chronic exposure to UVBR and the estrogenic chemical 4-tert-octylphenol (OP), alone and in combination, on the survival, development, growth, and metamorphosis of Rana pipiens (northern leopard frog) tadpoles are evaluated. Tadpoles were exposed to environmentally relevant levels of OP (0.01 or 10 nM), with and without exposure to UVBR (∼0.22 W/m²). After 8 mo of exposure, animals were transferred to a clean-water grow-out system for 3 additional mo. There was no effect of treatments on the weights of animals at wk 42 or on the age, snout–vent length (SVL), and weights of tadpoles at forelimb emergence (FLE). However, tadpoles exposed to UVBR had markedly delayed development and significantly fewer reached metamorphosis compared to control animals. Although exposure to UVBR and OP together produced the highest incidence of mortality and developmental anomalies, UVBR alone was sufficient to produce significant mortality of tadpoles, and exposure to UVBR or OP alone induced a significant increase in malformations and abnormalities. The malformations observed consisted mainly of spinal curvature. Our results show that chronic exposure to environmental levels of UVBR or OP alone exerts lethal and/or sublethal effects on R. pipiens tadpoles.

Acknowledgements

This research was supported by Ontario Graduate Scholarships (M.C. and C.M.), University of Ottawa Excellence Scholarships (M.C. and C.M.), Canadian Network of Toxicology Centres grants (V.T. and D.L.), Natural Sciences and Engineering Research Council of Canada (NSERC) grants (V.T. and D.L.), and the University of Ottawa (V.T. and D.L.). We thank Dr. Carol Meteyer for discussions and advice regarding the developmental malformations and abnormalities data presented in this article. We are grateful for the assistance of Bill Fletcher, Nicholas Potvin, Barbara Perez, and Jennifer Gibson with amphibian care. The help of Dr. Mark Forbes and Dr. Antoine Morin with the statistical analyses is greatly appreciated. Thank you to Bruce Pauli, Paula Duarte, and Valérie Langlois for providing helpful comments and to Kevin Desjardins for help in editing the article.

Notes

Meteyer, C. U. 2000. Field guide to malformations of frogs and toads with radiographic interpretations. Biological Science Report USGS/BRD/BSR-2000-0005. USGS National Wildlife Health Center, Madison, WI.