SREL Reprint #2777

Adverse effects of environmentally relevant dietary mercury exposure in larvae of the southern leopard frog, Rana sphenocephala

Jason Unrine, Charles Jagoe, William Hopkins, and Heather Brant

Savannah River Ecology Laboratory, University of Georgia, P.O. Drawer E. Aiken, South Carolina 29803, USA

Abstract: We exposed larvae of the southern leopard frog (Rana sphenocephala) to diets supplemented with aufwuchs (periphyton and associate organisms) from control and mercury (Hg) enriched mesocosms combined in proportions intended to mimic mercury concentrations and speciation in aujwuchs observed from aquatic systems contaminated by atmospheric deposition. Actual total mercury (THg) concentrations in the diets were 54, 423, 1409, and 3298 ng Hg/g DW 22%, 3.4%, 1.9% and 1.5% present as methylmercury (MMHg) for control, low, medium and high treatments, respectively. Rates of mortality, malformation, larval growth and development were observed over the entire larval period (60-254 d). Increased incidence of mortality, malformation, and changes in growth and development were observed at concentrations that reflect the highest concentrations expected in the amphibian diet from atmospheric deposition. The results of this study are probably more ecologically realistic than results obtained from previous studies of aqueous Hg toxicity and suggest that dietary Hg exposure in habitats primarily contaminated by atmospheric deposition has the potential to cause adverse effects in amphibian larvae. This is the first study to demonstrate the potential for adverse effects due environmentally realistic Hg exposure in amphibians.

Keywords: Amphibian, Diet, Growth, Development, Malformation

SREL Reprint #2777

Unrine, J. M., C. H. Jagoe, W. A. Hopkins, and H. A. Brant. 2004. Adverse effects of environmentally relevant dietary mercury exposure in larvae of the southern leopard frog, Rana sphenocephala. Paper 84 In: M. Horvat, N. Ogrinc, and J. Kotnik (Eds.). 7th International Conference on Mercury as a Global Pollutant. Jožef Stefan Institute, Ljubljana, Slovenia.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).