INFLUENCE OF LARVAL PERIOD ON RESPONSES OF OVERWINTERING GREEN FROG (RANA CLAMITANS) LARVAE EXPOSED TO CONTAMINATED SEDIMENTS
JOEL W. SNODGRASS,1 WILLIAM A. HOPKINS,2 BRIAN P.
JACKSON,2 JENNIFER A. BAIONNO,2 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
(Received 7 July 2004; Accepted 14 December 2004)
Abstract--Pond-breeding amphibians exhibit large intra-
and interspecific differences in the duration of the aquatic larval phase.
In contaminated aquattc 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 dled.(30l d)
larvae exposed to mi:ne 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.
