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Michelle D. Boone

Publications and source records attributed to Michelle D. Boone.

5 recordsLinked to original sources
USGS2012

Effects of the amphibian chytrid fungus and four insecticides on Pacific treefrogs ( Pseudacris regilla )

Chemical contamination may influence host-pathogen interactions, which has implications for amphibian population declines. We examined the effects of four insecticides alone or as a mixture on development and metamorphosis of Pacific Treefrogs ( Pseudacris regilla ) in the presence or absence of the amphibian chytrid fungus ( Batrachochytrium dendrobatidis [Bd]). Bd exposure had a negative impact on tadpole activity, survival to metamorphosis, time to metamorphosis, and time of tail absorption (with a marginally negative effect on mass at metamorphosis); however, no individuals tested positive for Bd at metamorphosis. The presence of sublethal concentrations of insecticides alone or in a mixture did not impact Pacific Treefrog activity as tadpoles, survival to metamorphosis, or time and size to metamorphosis. Insecticide exposure did not influence the effect of Bd exposure. Our study did not support our prediction that effects of Bd would be greater in the presence of expected environmental concentrations of insecticide(s), but it did show that Bd had negative effects on responses at metamorphosis that could reduce the quality of juveniles recruited into the population.

Journal of Herpetology↗
USGS2005

Multiple sublethal chemicals negatively affect tadpoles of the green frog, Rana clamitans

Many habitats may be exposed to multiple chemical contaminants, particularly in agricultural areas where fertilizer and pesticide use are common; however, the singular and interactive effects of contaminants are not well understood. The objective of our study was to examine how realistic, sublethal environmental levels of ammonium nitrate fertilizer (0, 10, 20 mg/L and ammonium chloride control) and the common insecticide carbaryl (0 or 2.5 mg/L) individually and interactively affect the development, size, and survival of green frog ( Rana clamitans ) tadpoles. We reared tadpoles for 95 d in outdoor 1,000-L polyethylene ponds. We found that the combination of carbaryl and nitrate had a negative effect on development and mass of tadpoles compared to the positive effect that either contaminant had alone. Presence of carbaryl was generally associated with short-term increases in algal resources, including ponds exposed to both carbaryl and nitrate. However, with exposure to nitrate and carbaryl, tadpole mass and development were not positively affected as with one chemical stressor alone. The combination of these sublethal contaminants may reduce the ability of amphibians to benefit from food-rich environments or have metabolic costs. Our study demonstrates the importance of considering multiple stressors when evaluating population-level responses.

Environmental Toxicology↗
USGS2005

Juvenile frogs compensate for small metamorph size with terrestrial growth: Overcoming the effects of larval density and insecticide exposure

I reared four species of anurans ( Rana sphenocephala [Southern Leopard Frog], Rana blairi [Plains Leopard Frog], Rana clamitans [Green Frog], and Bufo woodhousii [Woodhouse's Toad]) for seven to 12 months in small, outdoor terrestrial enclosures (1 × 2 m) to examine the consequences of larval competition (via density) and contaminant exposure (via the insecticide carbaryl). I added six Rana clamitans , eight R ana sphenocephala , eight Rana blairi , and 10 Bufo woodhousii to terrestrial enclosures shortly after metamorphosis and recaptured them during the following spring. All anurans from low-density ponds were significantly larger than those from high-density ponds, but these size differences did not significantly affect survival to or size at spring emergence. However, R. sphenocephala , R. blairi , and R. clamitans that survived to spring had been larger at metamorphosis on average than those that did not survive; in contrast, B. woodhousii that survived the winter were smaller at metamorphosis on average than those that did not survive. Carbaryl exposure affected mass at metamorphosis of R. clamitans and B. woodhousii that were added to enclosures, but this difference disappeared or did not increase by spring emergence. Overall, exposure to carbaryl during the larval period did not have any apparent effects on survival or growth during the terrestrial phase. In my study, anurans were able to offset small size at metamorphosis with terrestrial growth, although there was a trend of reduced overwinter survival for ranid species that metamorphosed at a smaller size.

Journal of Herpetology↗
USGS2003

The interactive effects of UV-B and insecticide exposure on tadpole survival, growth and development

Because declines within amphibian populations can seldom be attributed to a single cause, it is important to focus on multiple stressors, both natural and anthropogenic. Variables such as UV-B radiation and chemical contamination can interact with one another in ways that might not be predicted from single-factor studies. We exposed southern leopard frog (Rana sphenocephala) tadpoles to the insecticide carbaryl and varying intensities of UV-B radiation in artificial ponds and examined their effects on survival, size at metamorphosis, and the duration of the larval period. Tadpole survival to metamorphosis was positively influenced by UV-B intensity. Tadpoles in ponds exposed to carbaryl contained over three times more algae and yielded larger metamorphs than control ponds. Although previous laboratory studies have indicated carbaryl becomes more toxic in the presence of UV-B, we did not find such an effect, perhaps because of the protection afforded by dissolved organic carbon within the ponds. Our research emphasizes the importance of conducting field studies to more accurately predict what occurs under a natural setting. Published by Elsevier Science Ltd.

Biological Conservation↗