906 Environmental Toxicology and Chemistry, Vol. 21, No. 5, pp. 906–913, 2002  2002 SETAC Printed in the USA 0730-7268/02 $9.00 + .00 EFFECTS OF CHRONIC DIETARY EXPOSURE TO TRACE ELEMENTS ON BANDED WATER SNAKES (NERODIA FASCIATA) WILLIAM A. HOPKINS,*²‡ J OHN H. ROE,§ JOEL W. SNODGRASS, BRANDON P. STAUB,² BRIAN P. JACKSON,² and J USTIN D. CONGDON² ²Savannah River Ecology Laboratory, University of Georgia, Aiken, South Carolina 29801, USA ‡Department of Biological Sciences, University of South Carolina, Columbia, South Carolina 29208, USA §Department of Biological Sciences, Purdue University, Indiana 46805, USA Department of Biology, Towson University, Towson, Maryland 21252, USA ( Received 27 February 2001; Accepted 8 November 2001) Abstract—Little currently is known about the accumulation or effects of contaminants on reptiles. To date, most studies examining reptile exposure to trace elements report tissue burdens of field-captured animals, but seldom provide insight into the dose, duration, or mode of exposure involved. For two years, we fed juvenile banded water snakes (Nerodia fasciata) prey items collected from a coal ash–contaminated site that contained elevated levels of As, Cd, Cu, Se, Sr, and V. With the exception of Cu, snakes accumulated significant concentrations of elements, usually in a dose-dependent manner. Accumulation varied significantly among liver,kidney, and gonads, and in most cases between sexes. Selenium accumulation was most notable, greatly exceeding established toxicity thresholds for other vertebrates. Despite the high concentrations of pollutants accumulated, snakes exposed to the contaminated diet survived through the study and exhibited normal food consumption, growth, condition factor, overwinter survival and mass loss, metabolic rate, and gonadosomatic index. The results of this study confirm that diet can be a significant route of exposure to trace elements in snakes and indicate that further studies on snakes are warranted to better understand their responses to contaminants. Keywords—Reptiles Snakes Trophic transfer Coal combustion Selenium INTRODUCTION Currently, much less is known about the accumulation and effects of contaminants in reptiles than in any other vertebrate class, making prediction of contaminant impacts on reptiles extremely difficult [1,2]. Risk predictions based on toxicity thresholds established for other vertebrates (e.g., birds and fish) may be inappropriate for many reptiles because of their unique combinations of physiological and life history characteristics (e.g., long life span, relatively small home ranges, high trophic position, and ecotothermic physiology) [1,2]. Thus, it is im- perative that basic toxicological information be collected for reptiles so that adequate risk assessments and conservation efforts can be initiated in the future. Recent recognition that reptiles are grossly underrepre- sented in ecotoxicology, in addition to the fact that many rep- tile populations are declining [3], has prompted several reviews that identify immediate research needs in reptile ecotoxicology [1,2,4–7]. From these reviews, a clear consensus exists that among reptiles, turtles have received far greater attention than crocodilians and squamates (lizards and snakes). Of the few studies that have been performed on squamates, most have focused on organic contaminants [4,5]. The majority of studies on inorganic contaminants only report tissue residues in field- captured squamates, providing little information pertaining to biological effects or routes of exposure [6,8]. To date, only five studies have examined lethal or sublethal effects of in- organic contaminants on lizards and snakes [4,5,8–10]. The current study was initiated to study the accumulation * To whom correspondence may be addressed (hopkins@srel.edu). Presented at the 21st Annual Meeting, Society of Environmental Toxicology and Chemistry, Nashville, Tennessee, USA, November 12–16, 2000. and effects of inorganic contaminants on squamate reptiles under captive conditions that enabled us to control dose, du- ration, and mode of contaminant exposure. Specifically, we sought to expand upon two recent studies that examined ac- cumulation and effects of trace elements on the banded water snake (Nerodia fasciata) [8,10]. The first of our previous stud- ies indicated that water snakes inhabiting a coal ash disposal site had extremely high tissue burdens of Se, As, and Cd. Moreover, snakes with high tissue burdens exhibited increased standard metabolic rates (SMRs), possibly indicating that a significant physiological cost was associated with contaminant exposure [8]. In a follow-up laboratory study, we found that contaminated prey items were an important route of trace el- ement exposure for water snakes. Snakes fed contaminated prey for one year accumulated significant quantities of As, Cd, Se, Sr, and V in their kidneys, liver, and gonads [10]. However, neither of our previous studies was designed to rigorously examine the physiological effects of chronic dietary exposure to trace elements. Therefore, in the current study we fed con- taminated prey to juvenile water snakes for two years and measured trace element accumulation as well as survival, food consumption, growth, metabolic rate, condition factor, over- winter survival and mass loss, and gonadosomatic index. MATERIALS AND METHODS Snake collection and preexposure husbandry To minimize genetic variation in accumulation rates and responses to contaminant exposure, we utilized a full-sibling study design. A single gravid female banded water snake (post- parturition mass = 593 g) was collected from a reference site on August 13, 1997, on the Savannah River Site (SC, USA). The collection site was the same site where our previous field-