Although many amphibian populations around the world are declining at alarming rates, the cause of most declines remains unknown. Environmental contamination is one of several factors implicated in declines and may have particularly important effects on sensitive developmental stages. Despite the severe effects of maternal transfer of contaminants on early development in other vertebrate lineages, no studies have examined the effects of maternal transfer of contaminants on reproduction or development in amphibians. We examined maternal transfer of contaminants in eastern narrow-mouth toads (Gastrophryne carolinensis) collected from a reference site and near a coal-burning power plant. Adult toads inhabiting the industrial area transferred significant quantities of selenium and strontium to their eggs, but Se concentrations were most notable (up to 100 μg/g dry mass). Compared with the reference site, hatching success was reduced by 11% in clutches from the contaminated site. In surviving larvae, the frequency of developmental abnormalities and abnormal swimming was 55–58% higher in the contaminated site relative to the reference site. Craniofacial abnormalities were nearly an order of magnitude more prevalent in hatchlings from the contaminated site. When all developmental criteria were considered collectively, offspring from the contaminated site experienced 19% lower viability. Although there was no statistical relationship between the concentration of Se or Sr transferred to eggs and any measure of offspring viability, our study demonstrates that maternal transfer may be an important route of contaminant exposure in amphibians that has been overlooked.

We investigated the relationship between maintenance costs (standard metabolic rates, measured as O2 consumption at rest) in tadpoles of the bullfrog, Rana catesbeiana, and exposure to contaminants in a coal ash-polluted habitat (characterized by a variety of trace elements). We compared metabolic rates of tadpoles collected from the polluted site with those from an unpolluted reference pond. Tadpoles collected in the polluted site had 40%-97% higher standard metabolic rates than those collected from the reference pond. We also reciprocally transplanted eggs of the bullfrog between the polluted site and another reference pond and compared standard metabolic rates of tadpoles at 25 and 80 d posthatching. Metabolic rates of tadpoles raised in the polluted site were from 39% to 175% higher than those raised in a reference pond, depending on tadpole age and temperature at which metabolic rates were measured. There were no effects of site of origin of the eggs (polluted or unpolluted) on metabolic rates. Survival to hatching did not differ between sites, although survival to the end of the experiment (80 d posthatching) was lower in the polluted area than in the reference site. Surviving tadpoles were larger in wet body mass in the polluted site than in the reference pond, possibly due to lower survival in the former, but there was no relationship between survival and metabolic rate. It is clear that some feature of the polluted habitat was responsible for causing substantial elevation of standard metabolic rates of tadpoles. We hypothesize that the mixture of trace elements present in sediment and water in the polluted site was responsible for the observed physiological differences.

Abstract-Trace element concentrations in banded water snakes, Nerodia fasciata, and representative prey items from a site polluted by coal combustion wastes were compared with concentrations in conspecifics from a nearby reference site. Water snakes accumulated high concentrations of trace elements, especially arsenic (As) and selenium (Se), in the polluted habitat. In addition to being exposed to contaminants in water and sediments, snakes in the polluted site are exposed to contaminants by ingesting prey items that have elevated whole-body concentrations of trace elements, including As, cadmium (Cd), and Se. Snakes from the polluted site exhibited mean standard metabolic rates (SMR) 32% higher than snakes from the reference site. As a result, snakes from the polluted site appear to have elevated allocation of energy to maintenance and theoretically should have less energy available for growth, reproduction, and storage. Our findings are consistent with physiological responses recently documented in other organisms from the polluted site. We hypothesize that long-term exposure to coal ash-derived trace elements and the resultant accumulation of some elements are responsible for observed increases in SMR.

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