SREL Reprint #2815
Interaction of an insecticide with larval density in pond-breeding salamanders (Ambystoma)
Brian S. Metts, William A. Hopkins and John P. Nestor
University of Georgia, Savannah River Ecology Laboratory, Aiken, South Carolina, USA
Summary:
1.
Amphibian populations residing in or near agricultural areas are often
susceptible to pesticide contamination. Recent evidence suggests that
the effects of pesticides on amphibians often exceed those estimated in
laboratory toxicity tests because other environmental factors (e.g. predators,
resource abundance) can influence pesticide toxicity.
2. To examine the effects of an insecticide (carbaryl) on two species
of Ambystoma salamanders experiencing the natural stress of competition,
we manipulated chemical concentration (control, 3.5 and 7.0 mg L-1)
and larval density (low and high). We determined the effect of treatments
on snout-vent length (SVL), growth rate, lipid reserves, time to metamorphosis,
percent survival and percent metamorphosis.
3. Carbaryl negatively affected all response variables of Ambystoma
maculatum significantly, and significantly reduced survival and
metamorphosis of A. opacum. Increased density significantly influenced
SVL, lipid reserves, growth rate and metamorphosis of A. maculatum.
4. The effects of carbaryl and increased density on percent metamorphosis
were nearly additive, but were generally less than additive on other variables.
5. The negative effects of chemical contamination on salamanders
were likely because of pesticide-induced reductions of food resources,
as zooplankton abundance decreased by as much as 97% following carbaryl
application.
6. Our study demonstrates the importance of the interactive effects
that chemical contamination and natural environmental factors have on
salamanders.
Keywords: Ambystoma maculatum, Ambystoma opacum, carbaryl, density, insecticide
SREL Reprint #2815
Metts, B. S., W. A. Hopkins, and J. P. Nestor. 2005. Interaction of an insecticide with larval density in pond-breeding salamanders (Ambystoma). Freshwater Biology 50:685-696.