Thesis (M.S.) in Zoology--University of Maine, 2002. / Includes vita. Includes bibliographical references (leaves 39-43).

Declining amphibian populations in association with an incidence of deformities have been observed globally. These observations have alarmed the scientific community as well as the general public. Potential causes include exposure to pesticides; therefore two experiments were performed to test the sublethal effects of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) on tadpoles of the wood frog (<i>Rana sylvatica</i>). Wood frog tadpoles in the first experiment were exposed to 2,4-D amine at 0.1, 1.0 and 100 ug/L in outdoor microcosms. Morphometric measures (total length, snout-vent length (SVL) and wet weight) were taken at metamorphic climax. Deformities and circulating hormone concentrations (corticosterone - CORT) were also assessed. Results showed that though tadpoles were exposed to various concentrations of 2,4-D throughout their aquatic life, there were no treatment differences associated with any of the endpoints except for total length (p = 0.023). Total length during metamorphosis was highly variable. Although statistically significant, biological significance was questionable. The second experiment was conducted in the field using natural ponds. The experimental groups included forested ponds (removed from pesticide exposure), agricultural ponds (potentially exposed) and treated agricultural ponds (intentionally treated with 2,4-D to achieve a concentration of 10 ug/L). Relatively rapid degradation of 2,4-D occurred in all treated ponds. The mean half-life was 8.0 + 5.5 days. In spite of the degradation, 2,4-D was present in the ponds until tadpoles metamorphosed. Similar endpoints including morphometric measures, as well as deformities and plasma CORT hormone were determined. In addition, total lipid and total protein (of the carcass) were also measured. Unlike the microcosm study, statistically significant differences were observed in SVL, wet weight and total protein although the differences may have been unrelated to 2,4-D exposure. The metamorphs sampled from the forested ponds were smaller in SVL (23% shorter) and wet weight (58% lighter) (p < 0.029) relative to the other two groups. Total protein in the metamorphs from the forested ponds was 22% lower than that of the agricultural ponds (p = 0.020). Reduced hormonal response to acute stress (p = 0.001) was found in metamorphs of the forested ponds compared to those of the other two groups (66% lower response). Herbicide exposure may have induced low level stimulation of growth (a positive impact on the exposed animals), as well as a possible elevation of baseline corticosterone, in the agricultural and treated metamorphs or there may have been a negative stressor present in the forested pond environment. It is not possible to identify the specific factors that were involved. It is unclear if 2,4-D affected the growth and development of wood frog tadpoles.

Declining amphibian populations in association with an incidence of deformities have been observed globally. These observations have alarmed the scientific community as well as the general public. Potential causes include exposure to pesticides; therefore two experiments were performed to test the sublethal effects of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) on tadpoles of the wood frog (<i>Rana sylvatica</i>). Wood frog tadpoles in the first experiment were exposed to 2,4-D amine at 0.1, 1.0 and 100 ug/L in outdoor microcosms. Morphometric measures (total length, snout-vent length (SVL) and wet weight) were taken at metamorphic climax. Deformities and circulating hormone concentrations (corticosterone - CORT) were also assessed. Results showed that though tadpoles were exposed to various concentrations of 2,4-D throughout their aquatic life, there were no treatment differences associated with any of the endpoints except for total length (p = 0.023). Total length during metamorphosis was highly variable. Although statistically significant, biological significance was questionable. The second experiment was conducted in the field using natural ponds. The experimental groups included forested ponds (removed from pesticide exposure), agricultural ponds (potentially exposed) and treated agricultural ponds (intentionally treated with 2,4-D to achieve a concentration of 10 ug/L). Relatively rapid degradation of 2,4-D occurred in all treated ponds. The mean half-life was 8.0 + 5.5 days. In spite of the degradation, 2,4-D was present in the ponds until tadpoles metamorphosed. Similar endpoints including morphometric measures, as well as deformities and plasma CORT hormone were determined. In addition, total lipid and total protein (of the carcass) were also measured. Unlike the microcosm study, statistically significant differences were observed in SVL, wet weight and total protein although the differences may have been unrelated to 2,4-D exposure. The metamorphs sampled from the forested ponds were smaller in SVL (23% shorter) and wet weight (58% lighter) (p < 0.029) relative to the other two groups. Total protein in the metamorphs from the forested ponds was 22% lower than that of the agricultural ponds (p = 0.020). Reduced hormonal response to acute stress (p = 0.001) was found in metamorphs of the forested ponds compared to those of the other two groups (66% lower response). Herbicide exposure may have induced low level stimulation of growth (a positive impact on the exposed animals), as well as a possible elevation of baseline corticosterone, in the agricultural and treated metamorphs or there may have been a negative stressor present in the forested pond environment. It is not possible to identify the specific factors that were involved. It is unclear if 2,4-D affected the growth and development of wood frog tadpoles.

Thesis (Ph. D.) in Ecology and Environmental Science--University of Maine, 2003. / Includes vita. Includes bibliographical references (leaves 88-96).

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: wood frog; vernal pool conservation; fragmented habitat; Rana sylvatica; DNA fingerprinting. Includes bibliographical references (p. 38-40).

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on February 28, 2008) Vita. Includes bibliographical references.

No description available.

Roundup is a commonly used pesticide applied to agriculture and forest habitats. In Canada and parts of the North Eastern United States, these areas are generally optimal for amphibians due to the presence of small, ephemeral water bodies. While Roundup has been shown to have no adverse effects on a number of species, amphibians are one of the few groups who show high sensitivity to Roundup. My research aims to determine how an acute sub-lethal dose of Roundup affects several different facets of larvae development in wood frogs (Lithobates sylvaticus). In Chapter 2 I examined the effect of Roundup on amphibian development. Groups of tadpoles were treated with Roundup (0.5 mg a.e./L) for four days at three different times in their development (Gosner stage 26, 31-32 and 37-38), while a control group was maintained in similar conditions without Roundup. Pictures were taken every four days until tadpoles reached metamorphosis. Changes in development, body area or length were assessed, along with metamorphic endpoints, such as timing of metamorphosis and weight. Although there was no differential effect of Roundup on tadpole growth or weight, there was a slight, non-ecologically relevant, delay in development in tadpoles treated with Roundup at stage 26. The delay was not detectable in the second half of the experiment, indicating that compensatory mechanisms allowed those individuals to recover. Neither time to metamorphosis or weight at metamorphosis were affected by an environmentally relevant exposure to Roundup. In Chapter 3 I focused on the effect of Roundup on crucial behaviours related to the ability of larval amphibians to detect and avoid predation threats. I demonstrated that being exposed to Roundup for one hour eliminated the response of larval wood frogs to cues from injured conspecifics (i.e. cues known to elicit dramatic anti-predator responses in a wide variety of aquatic species). Tadpoles that were maintained in clean water and exposed to a combination of injured conspecific cues and Roundup, did not exhibit a decrease in movement, when compared to control tadpoles. This result indicates that Roundup deactivates the alarm function of the injured conspecific cues. However, it is possible that both the cues and the animal would be affected by Roundup. In Chapter 3 I also demonstrated that tadpoles that were exposed to Roundup as embryos had reduced basal movement rates. The results of this thesis illustrate that an environmentally relevant concentration of Roundup (0.5 mg a.e./L), does not negatively affect the development of tadpoles. The studies outlined in this thesis suggest that at this exposure concentration, behaviour acts as a more sensitive endpoint, than more traditional morphologic endpoints.

No description available.

Although the range dynamics of North American amphibians during the last glacial cycle are increasingly better understood, the recolonization history of the most northern regions and the impact of southern refugia on patterns of genetic diversity in these regions are not well reconstructed. In this study I present the phylogeographic history of a widespread and primarily northern frog, Rana sylvatica. For this study, 45 individuals from 34 localities were surveyed for a 700 b p. fragment of cytochrome b and 551 individuals from 116 localities were surveyed for 650 b.p. of the NADH dehydrogenase subunit 2 and tRNATRP mitochondrial genes. Phylogenetic analyses revealed two distinct clades corresponding to eastern and western populations. Phylogeographic patterns within each of these clades revealed similarities as well as differences from patterns found in other species. Specifically, the results corroborate eastern refugia located in the southern Appalachians near present-day North and South Carolina and in the interior plains in the lower Ohio River Valley. Current Maritime populations form a subclade amongst eastern populations and appear to have been colonized from the southern refugium. However, a more northern refugium located in the Appalachian highlands seems to have been source for most other northeastern wood frog populations. Rana sylvatica populations in the Great Lakes region appear to have been colonized from a western refugium located in present-day Wisconsin. This refugium was also a likely source for populations in the species' expansive northwestern range since there is no evidence to support additional, more western refugia.