SREL Reprint #2859

 

 

 

Influence of larval period on responses of overwintering green frog (Rana Clamitans) larvae exposed to contaminated sediments

Joel W. Snodgrass1, William A. Hopkins2, Brian P. Jackson2, Jennifer A. Baionno2, and
Jeffroy Broughton1

1Department of Biological Sciences, Towson University, Towson, Maryland 21252, USA
2University of Georgia, Savannah River Ecology Laboratory, Aiken, South Carolina 29802, USA

Abstract: Pond-breeding amphibians exhibit large intra- and interspecific differences in the duration of the aquatic larval phase. In contaminated aquatic environments, a prolonged larval phase means prolonged exposure to pollutants and, potentially, more severe toxic effects. In the laboratory, we tested this hypothesis by exposing green frog larvae (Rana clamitans) to commercial clean sand (control), sediment from an abandoned surface mine (mine), or sediment contaminated with coal combustion waste (CCW). By collecting eggs late in the breeding season, we obligated larvae to overwinter and spend a protracted amount of time exposed to contaminated sediments. The experiment was continued until all larvae either successfully completed metamorphosis or died (30l d). Larvae exposed to mine sediments accumulated significant levels of Pb and Zn, whereas larvae exposed to CCW-contaminated sediment accumulated significant levels of As, Se, Sr, and V. Larvae exposed to mine sediments suffered sublethal effects in the form of reduced growth and size at metamorphosis, but the proportion of larvae successfully completing metamorphosis (93%) was the same for both control and mine treatments. In contrast, larvae exposed to CCW-contaminated sediment suffered greatly reduced survival (13%) compared to both control and mine treatments. Moreover, among larvae in the CCW treatment, the majority of mortality occurred during the latter part the overwintering period (after day 205), corresponding to the onset of metamorphosis in the controls. Our results suggest that the length of the larval period may be one of many life-history or ecological characteristics that influence the sensitivity of aquatic breeding amphibians to environmental pollutants.

Keywords: Amphibians, Frogs, Metals, Metalloids, Larval development

SREL Reprint #2859

Snodgrass, J. W., W. A. Hopkins, B. P. Jackson, J. A. Baionno, and J. Broughton. 2005. Influence of larval period on responses of overwintering green frog (Rana Clamitans) larvae exposed to contaminated sediments. Environmental Toxicology and Chemistry 24:1508-1514.

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