The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Michael E. Fraker - One of the best experts on this subject based on the ideXlab platform.
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Risk Assessment and Anti-Predator Behavior of Wood Frog (Rana sylvatica) Tadpoles: A Comparison with Green Frog (Rana clamitans) Tadpoles
Journal of Herpetology, 2010Co-Authors: Michael E. FrakerAbstract:This study combines three experiments that identify how Wood Frog (Rana sylvatica) tadpoles assess risk from chemical cues produced by larval dragonflies (Anax junius) preying on conspecifics. I also compare the results to previous studies using Green Frog (Rana clamitans) tadpoles. The results suggest that Wood Frog tadpoles largely assess predation risk through Anax chemical cues similarly to Green Frog tadpoles. This is to be expected because the tadpoles are congeneric and both face predation from Anax in the field. However, their behavioral response to a particular level of perceived risk differs. Wood Frog tadpoles reduced their total activity (swimming and feeding) for a shorter time than Green Frog tadpoles. Wood Frog tadpoles also reduced their feeding activity more strongly than their swimming activity during cue exposure. I relate the differences between the behavioral responses of Wood Frog and Green Frog tadpoles to differences in their life-history strategies.
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Predation risk assessment by green frog (Rana clamitans) tadpoles through chemical cues produced by multiple prey
Behavioral Ecology and Sociobiology, 2009Co-Authors: Michael E. FrakerAbstract:Many prey assess predation risk through predator chemical cues. Numerous studies have shown that (1) prey sometimes respond to chemical cues produced by heterospecifics and (2) that many species are capable of associative learning. This study extends this research by focusing on predation risk assessment and antipredator behavior in environments containing chemical cues produced by multiple prey species. The results show that green frog ( Rana clamitans ) tadpoles (1) assess risk from the chemical cue produced during predation by a heterospecific (gray tree frog, Hyla versicolor , tadpoles) and (2) can exhibit similarly strong behavioral responses to a mix of conspecific and heterospecific cues compared to conspecific cue alone, depending on their conditioning environment. I then discuss how the prey choice of the predators and the relative abundances of the prey species should influence the informational value of heterospecific cues.
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perceptual limits to predation risk assessment in green frog Rana clamitans tadpoles
Behaviour, 2009Co-Authors: Michael E. FrakerAbstract:Summary Many prey assess predation risk through information sources that decline in reliability over time (i.e., the information sources indicate a wider range of potential predation risk levels over time until they provide no information about the current predation risk). However, prey may lack the perceptual ability to accurately assess the reliability of ageing information sources. Here, evidence is provided that suggests that green frog {Rana clamitans) tadpoles are unable to assess the age of the chemical cue of predatory larval dragonflies (Anax junius) upon exposure to cue up to 48 h old (but can at 72 h). As a result, tadpoles may overestimate the level of risk when they encounter aged Anax chemical cue, resulting in a disproportionately strong behavioural response. In general, the results suggest that the predation risk assessment of prey depends not only on the objective characteristics of the information source, but also on the perceptual limitations of the prey. Prey may lack the context to accurately assess information sources and may consequently misestimate the actual level of predation risk.
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the influence of the circadian rhythm of green frog Rana clamitans tadpoles on their antipredator behavior and the strength of the nonlethal effects of predators
The American Naturalist, 2008Co-Authors: Michael E. FrakerAbstract:Prey trade off predation risk and foraging gain in their activity level. Their response to this trade-off mediates direct and indirect interactions between predators and the community (i.e., nonlethal effects). A prey's activity level may also vary independently because of circadian rhythms. I tested how the antipredator behavior of green frog (Rana clamitans) tadpoles can be influenced by their circadian rhythm (primarily nocturnal feeding) and how the strengths of nonlethal effects vary in turn. Tadpoles exhibited stronger activity reductions when under predation risk during the day (which may result in stronger resource depression). However, when predation risk was high and persistent, tadpoles remained inactive during both day and night. Consequently, the nonlethal effect on tadpoles (growth rate reduction) was more negative at night. Predicting prey behavior and its effects requires identifying how their perceived risk interacts with and is limited by all factors that can influence their response.
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The effect of hunger on the strength and duration of the antipredator behavioral response of green frog (Rana clamitans) tadpoles
Behavioral Ecology and Sociobiology, 2008Co-Authors: Michael E. FrakerAbstract:The activity level of prey reflects a trade-off between predation risk and foraging gain. A number of theoretical and empirical studies have shown that a prey's energetic state or the level of its resource should influence this trade-off (i.e., what the optimal activity level at a level of predation risk is). Here, I show that the energetic state of prey may also influence the duration of their antipredator behavioral response. Green frog tadpoles (Rana clamitans) reduced their activity level for a shorter time during exposure to the chemical cue of predatory larval dragonflies (Anax spp.) as their time since last feeding increased (i.e., as their energetic state decreased). Interestingly, the tadpoles strongly reduced their activity level upon cue exposure in all treatments. Thus, the relative activity level of tadpoles at different energetic states varied over time.
Michelle D. Boone - One of the best experts on this subject based on the ideXlab platform.
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characterization of gene expression endpoints during postembryonic development of the northern green frog Rana clamitans melanota
Zoological Science, 2013Co-Authors: Austin S Hammond, Michelle D. Boone, Nik Veldhoen, Marek J Kobylarz, Nicholas R Webber, Jameson Jordan, Vicki Rehaume, Caren C HelbingAbstract:Postembryonic development of a larval tadpole into a juvenile frog involves the coordinated action of thyroid hormone (TH) across a diversity of tissues. Changes in the frog transcriptome represent a highly sensitive endpoint in the detection of developmental progression, and for the identification of environmental chemical contaminants that possess endocrine disruptive properties. Unfortunately, in contrast with their vital role as sentinels of environmental change, few gene expression tools currently exist for the majority of native North American frog species. We have isolated seven expressed gene sequences from the Northern green frog (Rana clamitans melanota) that encode proteins associated with TH-mediated postembryonic development and global stress response, and established a quantitative real-time polymerase chain reaction (qPCR) assay. We also obtained three additional species-specific gene sequences that functioned in the normalization of the expression data. Alterations in mRNA abundance profiles were identified in up to eight tissues during R. clamitans postembryonic development, and following exogenous administration of TH to premetamorphic tadpoles. Our results characterize tissue distribution and sensitivity to TH of select mRNA of a common North American frog species and support the potential use of this qPCR assay in identification of the presence of chemical agents in aquatic environments that modulate TH action.
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Juvenile green frog (Rana clamitans) predatory ability not affected by exposure to carbaryl at different times during larval development
Environmental toxicology and chemistry, 2011Co-Authors: Melanie J. Davis, Peter Kleinhenz, Michelle D. BooneAbstract:Larval exposure to pesticides can occur at different times during development and can negatively impact amphibian fitness. We examined the effects of larval green frog (Rana clamitans) exposure to carbaryl at 2, 4, 8, or 16 weeks of development on juvenile predatory ability. We did not find evidence that predatory ability was affected by exposure to carbaryl, which suggests that carbaryl does not have latent effects on the predatory performance of green frogs in subsequent life stages. Environ. Toxicol. Chem. 2011; 30:1618–1620. © 2011 SETAC
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multiple sublethal chemicals negatively affect tadpoles of the green frog Rana clamitans
Environmental Toxicology and Chemistry, 2005Co-Authors: Michelle D. Boone, Christine M Bridges, James F Fairchild, Edward E LittleAbstract: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.
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Effects of carbaryl on green frog (Rana clamitans) tadpoles: Timing of exposure versus multiple exposures
Environmental toxicology and chemistry, 2003Co-Authors: Michelle D. Boone, Christine M BridgesAbstract:The majority of studies on pesticide impacts have evaluated the effects of single exposures. However, multiple exposures to a pesticide may be more prevalent. The objective of our study was to determine how multiple exposures versus single exposure at different times during development affected survival to metamorphosis, tadpole survival, tadpole mass, and tadpole developmental stage of green frog (Rana clamitans) tadpoles reared at low and high density in outdoor cattle tank ponds. Tadpoles were exposed to carbaryl zero, one, two, or three times at 14-d intervals. We applied single doses of carbaryl at one of three times, specifically during early, mid, or late development. Overall, we found that multiple exposures had a greater impact than single exposures during development. More individuals reached metamorphosis in ponds exposed to multiple doses of carbaryl compared with controls, indicating that the presence of carbaryl stimulated metamorphosis. The presence of carbaryl in the aquatic environment also resulted in more developed tadpoles compared with controls. Tadpoles in control ponds did not reach metamorphosis and were less developed than individuals exposed to carbaryl; this effect indicates that, under ideal conditions, green frogs could overwinter in ponds so that greater size could be attained before metamorphosis in the following spring or summer. Our study demonstrated the importance of including realistic application procedures when evaluating the effects of a pesticide and that multiple exposures to a short-lived pesticide are more likely to affect an amphibian population.
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Growth and development of larval green frogs (Rana clamitans) exposed to multiple doses of an insecticide
Oecologia, 2001Co-Authors: Michelle D. Boone, Christine M Bridges, Betsie B. RothermelAbstract:Our objective was to determine how green frogs (Rana clamitans) are affected by multiple exposures to a sublethal level of the carbamate insecticide, carbaryl, in outdoor ponds. Tadpoles were added to 1,000-l ponds at a low or high density which were exposed to carbaryl 0, 1, 2, or 3 times. Length of the larval period, mass, developmental stage, tadpole survival, and proportion metamorphosed were used to determine treatment effects. The frequency of dosing affected the proportion of green frogs that reached metamorphosis and the developmental stage of tadpoles. Generally, exposure to carbaryl increased rates of metamorphosis and development. The effect of the frequency of carbaryl exposure on development varied with the density treatment; the majority of metamorphs and the most developed tadpoles came from high-density ponds exposed to carbaryl 3 times. This interaction suggests that exposure to carbaryl later in the larval period stimulated metamorphosis, directly or indirectly, under high-density conditions. Our study indicates that exposure to a contaminant can lead to early initiation of metamorphosis and that natural biotic factors can mediate the effects of a contaminant in the environment.
James P Bogart - One of the best experts on this subject based on the ideXlab platform.
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the functional integrity of northern leopard frog Rana pipiens and green frog Rana clamitans populations in orchard wetlands i genetics physiology and biochemistry of breeding adults and young of the year
Environmental Toxicology and Chemistry, 1998Co-Authors: M L Harris, Christine A Bishop, John Struger, Michael R Van Den Heuvel, Glen Van Der Kraak, George D Dixon, Brian D Ripley, James P BogartAbstract:Northern leopard frogs (Rana pipiens) and green frogs (Rana clamitans) were evaluated at eight wetland sites, four of which were within apple orchards, to determine if environmental changes associated with orchard management affected measured biological parameters. Size, age, genetic variation, condition indices, levels of circulating steroid hormones, 7-ethoxyresorufin-O-deethylase activity (EROD), and organochlorine and organophosphorus residues in breeding males sampled at pond sites in orchards were compared to the same parameters measured in breeding males from reference sites. Also, the size and physiological condition of young-of-the-year captured in orchard and reference ponds were compared. No evidence of a reduction in genetic variation was found in populations of either species at any sites, but unexpectedly high average heterozygosity values (0.191–0.282) in concert with low overall fixation indices (0.012–0.059) in adults of both species did suggest that pond populations were interacting with neighboring populations in nonorchard habitats. Few significant differences in levels of circulating steroid hormones or condition indices of breeding males were found among sites. Significant EROD induction in male green frogs collected from one orchard site during one sampling event was the only indication that a metabolic challenge due to presence of cytochrome P450-inducing toxicants may have existed, whereas elevated concentrations of organochlorines (dichlorodiphenyltrichloroethane [DDT]- or endosulfan-related) in green frog tissues suggested that frogs at three orchard sites were taking up pesticides. Significant differences in size of equivalent-age male and juvenile leopard frogs and green frogs occupying different study sites suggested that suboptimal habitat characteristics existed at one or two of the four orchard sites. However, site-specific habitat deficiencies could not be related to orchard study sites in general, and, thus, wetlands in apple orchards appeared to provide viable breeding habitat for both northern leopard frogs and green frogs.
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the functional integrity of northern leopard frog Rana pipiens and green frog Rana clamitans populations in orchard wetlands ii effects of pesticides and eutrophic conditions on early life stage development
Environmental Toxicology and Chemistry, 1998Co-Authors: M L Harris, Christine A Bishop, John Struger, Brian D Ripley, James P BogartAbstract:Premetamorphic northern leopard frogs (Rana pipiens) and green frogs (Rana clamitans) were evaluated at seven wetland sites, four of which were within apple orchards, to determine if environmental conditions associated with orchard management in southern Ontario, Canada, affected frog early development. Synchronous with breeding events (May–July), embryos and tadpoles were exposed, in situ and in the laboratory, to study site pond water for 2 to 3 weeks. Six pesticides commonly applied in apple orchards (Guthion® 50WP, Imidan® 50WP, Thiodan® 50WP, Dithane® DG, Nova® 40W, and Basudin® 500EC) and technical grade diazinon were also evaluated for direct toxicity to green frogs using continuous and discontinuous toxicity tests. Embryos and larvae exhibited poor hatching success and survival at some orchard sites during in situ assays, but no specific water source produced consistently poor developmental success. Reduced tadpole growth occurred at several study sites, showing no clear distinction between reference and orchard sites. Despite the collection of substantial environmental data, only surface water temperature appeared to be correlated with growth rates. Basudin 500EC, technical grade diazinon, and Dithane DG caused mortality, deformities, or growth inhibition during early development at environmentally relevant concentrations (<0.01 mg/L), whereas Imidan 50WP, Guthion 50WP, and Nova 40W produced survival or growth effects at much higher levels (5–10 mg/L). Dithane DG (mancozeb) was acutely toxic during prolonged exposures, and sublethal growth and deformity responses occurred at nominal concentrations greater than 0.01 mg/L. Diazinon was the most toxic to green frogs, with median lethal concentrations of 2.8 to 5 μg/L and median effective concentrations of 6 to 14 μg/L for formulation and technical grades, respectively. The combined results of in situ and laboratory tests of green frog and leopard frog developmental success suggested that embryo—larval development of these two species could be accomplished at all study sites, independent of the association with apple orchards.
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Printed in the USA 0730-7268/98 $6.00 �.00 THE FUNCTIONAL INTEGRITY OF NORTHERN LEOPARD FROG (Rana PIPIENS) AND GREEN FROG (Rana clamitans) POPULATIONS IN ORCHARD WETLANDS. II. EFFECTS OF PESTICIDES AND EUTROPHIC CONDITIONS ON EARLY LIFE STAGE DEVELO
1997Co-Authors: Megan L. Harris, Christine A Bishop, John Struger, Brian Ripley, James P BogartAbstract:Abstract—Premetamorphic northern leopard frogs (Rana pipiens) and green frogs (Rana clamitans) were evaluated at seven wetland sites, four of which were within apple orchards, to determine if environmental conditions associated with orchard management in southern Ontario, Canada, affected frog early development. Synchronous with breeding events (May–July), embryos and tadpoles were exposed, in situ and in the laboratory, to study site pond water for 2 to 3 weeks. Six pesticides commonly applied in apple orchards (Guthion � 50WP, Imidan � 50WP, Thiodan � 50WP, Dithane � DG, Nova � 40W, and Basudin � 500EC) and technical grade diazinon were also evaluated for direct toxicity to green frogs using continuous and discontinuous toxicity tests. Embryos and larvae exhibited poor hatching success and survival at some orchard sites during in situ assays, but no specific water source produced consistently poor developmental success. Reduced tadpole growth occurred at several study sites, showing no clear distinction between reference and orchard sites. Despite the collection of substantial environmental data, only surface water temperature appeared to be correlated with growth rates. Basudin 500EC, technical grade diazinon, and Dithane DG caused mortality, deformities, or growth inhibition during early development at environmentally relevant concentrations (�0.01 mg/L), whereas Imidan 50WP, Guthion 50WP, and Nova 40W produced survival or growth effects at much higher levels (5–10 mg/L). Dithan
Christine M Bridges - One of the best experts on this subject based on the ideXlab platform.
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multiple sublethal chemicals negatively affect tadpoles of the green frog Rana clamitans
Environmental Toxicology and Chemistry, 2005Co-Authors: Michelle D. Boone, Christine M Bridges, James F Fairchild, Edward E LittleAbstract: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.
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Effects of carbaryl on green frog (Rana clamitans) tadpoles: Timing of exposure versus multiple exposures
Environmental toxicology and chemistry, 2003Co-Authors: Michelle D. Boone, Christine M BridgesAbstract:The majority of studies on pesticide impacts have evaluated the effects of single exposures. However, multiple exposures to a pesticide may be more prevalent. The objective of our study was to determine how multiple exposures versus single exposure at different times during development affected survival to metamorphosis, tadpole survival, tadpole mass, and tadpole developmental stage of green frog (Rana clamitans) tadpoles reared at low and high density in outdoor cattle tank ponds. Tadpoles were exposed to carbaryl zero, one, two, or three times at 14-d intervals. We applied single doses of carbaryl at one of three times, specifically during early, mid, or late development. Overall, we found that multiple exposures had a greater impact than single exposures during development. More individuals reached metamorphosis in ponds exposed to multiple doses of carbaryl compared with controls, indicating that the presence of carbaryl stimulated metamorphosis. The presence of carbaryl in the aquatic environment also resulted in more developed tadpoles compared with controls. Tadpoles in control ponds did not reach metamorphosis and were less developed than individuals exposed to carbaryl; this effect indicates that, under ideal conditions, green frogs could overwinter in ponds so that greater size could be attained before metamorphosis in the following spring or summer. Our study demonstrated the importance of including realistic application procedures when evaluating the effects of a pesticide and that multiple exposures to a short-lived pesticide are more likely to affect an amphibian population.
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Growth and development of larval green frogs (Rana clamitans) exposed to multiple doses of an insecticide
Oecologia, 2001Co-Authors: Michelle D. Boone, Christine M Bridges, Betsie B. RothermelAbstract:Our objective was to determine how green frogs (Rana clamitans) are affected by multiple exposures to a sublethal level of the carbamate insecticide, carbaryl, in outdoor ponds. Tadpoles were added to 1,000-l ponds at a low or high density which were exposed to carbaryl 0, 1, 2, or 3 times. Length of the larval period, mass, developmental stage, tadpole survival, and proportion metamorphosed were used to determine treatment effects. The frequency of dosing affected the proportion of green frogs that reached metamorphosis and the developmental stage of tadpoles. Generally, exposure to carbaryl increased rates of metamorphosis and development. The effect of the frequency of carbaryl exposure on development varied with the density treatment; the majority of metamorphs and the most developed tadpoles came from high-density ponds exposed to carbaryl 3 times. This interaction suggests that exposure to carbaryl later in the larval period stimulated metamorphosis, directly or indirectly, under high-density conditions. Our study indicates that exposure to a contaminant can lead to early initiation of metamorphosis and that natural biotic factors can mediate the effects of a contaminant in the environment.
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the effect of temperature on the potency of carbaryl for survival of tadpoles of the green frog Rana clamitans
Environmental Toxicology and Chemistry, 1999Co-Authors: Michelle D. Boone, Christine M BridgesAbstract:This study assessed the effect of temperature on the potency of carbaryl using tadpoles of Rana clamitans. Temperature, chemical concentration, and the interaction of temperature and chemical significantly affected survival. Generally, increased temperature resulted in lower survival. This study suggests a range of temperatures realistic for a species should be used in toxicity tests.
John Struger - One of the best experts on this subject based on the ideXlab platform.
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potential endocrine disruption of sexual development in free ranging male northern leopard frogs Rana pipiens and green frogs Rana clamitans from areas of intensive row crop agriculture
Aquatic Toxicology, 2008Co-Authors: Tana V Mcdaniel, John Struger, Pamela A Martin, J P Sherry, Chris H Marvin, Mark E Mcmaster, Stacey Clarence, Gerald R TetreaultAbstract:Abstract Intensive row crop agriculture (IRCA) for corn and soybean production is predominant in eastern and central North America. IRCA relies heavily on pesticide and nutrient inputs to maximize production under conventional systems. In 2003–2005, we assessed the occurrence of a suite of potential endocrine effects in amphibians inhabiting farm ponds and agricultural drains in IRCA areas of southwestern Ontario. Effects were compared to amphibians from two agricultural reference sites as well as four non-agricultural reference sites. Pesticide and nutrient concentrations were also determined in water samples from those sites. Atrazine and metolachlor were detected in most samples, exceeding 1 μg L −1 at some sites. Blood samples were taken from northern leopard frogs ( Rana pipiens ) and green frogs ( Rana clamitans ) for analysis of circulating sex steroids and vitellogenin-like protein (Vtg-lp), a biomarker of exposure to environmental estrogens. Gonads were histologically examined for evidence of abnormalities. Some evidence of exposure to endocrine disrupting compounds was apparent from the data. The occurrence of testicular ovarian follicles (TOFS) in male R. pipiens was significantly higher (42%; p p > 0.05). Plasma Vtg-lp was detected in only one male R. pipiens from an agricultural site. Neither gonad size, gonad maturity nor sex steroid levels differed between normal males and those with testicular oocytes. Although the proportion of testicular oocytes did not correlate directly with atrazine concentrations, it did correlate with a mixture of pesticides and nutrients, particularly atrazine and nitrate, while the number of pesticides detected at each site was also important.
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the functional integrity of northern leopard frog Rana pipiens and green frog Rana clamitans populations in orchard wetlands i genetics physiology and biochemistry of breeding adults and young of the year
Environmental Toxicology and Chemistry, 1998Co-Authors: M L Harris, Christine A Bishop, John Struger, Michael R Van Den Heuvel, Glen Van Der Kraak, George D Dixon, Brian D Ripley, James P BogartAbstract:Northern leopard frogs (Rana pipiens) and green frogs (Rana clamitans) were evaluated at eight wetland sites, four of which were within apple orchards, to determine if environmental changes associated with orchard management affected measured biological parameters. Size, age, genetic variation, condition indices, levels of circulating steroid hormones, 7-ethoxyresorufin-O-deethylase activity (EROD), and organochlorine and organophosphorus residues in breeding males sampled at pond sites in orchards were compared to the same parameters measured in breeding males from reference sites. Also, the size and physiological condition of young-of-the-year captured in orchard and reference ponds were compared. No evidence of a reduction in genetic variation was found in populations of either species at any sites, but unexpectedly high average heterozygosity values (0.191–0.282) in concert with low overall fixation indices (0.012–0.059) in adults of both species did suggest that pond populations were interacting with neighboring populations in nonorchard habitats. Few significant differences in levels of circulating steroid hormones or condition indices of breeding males were found among sites. Significant EROD induction in male green frogs collected from one orchard site during one sampling event was the only indication that a metabolic challenge due to presence of cytochrome P450-inducing toxicants may have existed, whereas elevated concentrations of organochlorines (dichlorodiphenyltrichloroethane [DDT]- or endosulfan-related) in green frog tissues suggested that frogs at three orchard sites were taking up pesticides. Significant differences in size of equivalent-age male and juvenile leopard frogs and green frogs occupying different study sites suggested that suboptimal habitat characteristics existed at one or two of the four orchard sites. However, site-specific habitat deficiencies could not be related to orchard study sites in general, and, thus, wetlands in apple orchards appeared to provide viable breeding habitat for both northern leopard frogs and green frogs.
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the functional integrity of northern leopard frog Rana pipiens and green frog Rana clamitans populations in orchard wetlands ii effects of pesticides and eutrophic conditions on early life stage development
Environmental Toxicology and Chemistry, 1998Co-Authors: M L Harris, Christine A Bishop, John Struger, Brian D Ripley, James P BogartAbstract:Premetamorphic northern leopard frogs (Rana pipiens) and green frogs (Rana clamitans) were evaluated at seven wetland sites, four of which were within apple orchards, to determine if environmental conditions associated with orchard management in southern Ontario, Canada, affected frog early development. Synchronous with breeding events (May–July), embryos and tadpoles were exposed, in situ and in the laboratory, to study site pond water for 2 to 3 weeks. Six pesticides commonly applied in apple orchards (Guthion® 50WP, Imidan® 50WP, Thiodan® 50WP, Dithane® DG, Nova® 40W, and Basudin® 500EC) and technical grade diazinon were also evaluated for direct toxicity to green frogs using continuous and discontinuous toxicity tests. Embryos and larvae exhibited poor hatching success and survival at some orchard sites during in situ assays, but no specific water source produced consistently poor developmental success. Reduced tadpole growth occurred at several study sites, showing no clear distinction between reference and orchard sites. Despite the collection of substantial environmental data, only surface water temperature appeared to be correlated with growth rates. Basudin 500EC, technical grade diazinon, and Dithane DG caused mortality, deformities, or growth inhibition during early development at environmentally relevant concentrations (<0.01 mg/L), whereas Imidan 50WP, Guthion 50WP, and Nova 40W produced survival or growth effects at much higher levels (5–10 mg/L). Dithane DG (mancozeb) was acutely toxic during prolonged exposures, and sublethal growth and deformity responses occurred at nominal concentrations greater than 0.01 mg/L. Diazinon was the most toxic to green frogs, with median lethal concentrations of 2.8 to 5 μg/L and median effective concentrations of 6 to 14 μg/L for formulation and technical grades, respectively. The combined results of in situ and laboratory tests of green frog and leopard frog developmental success suggested that embryo—larval development of these two species could be accomplished at all study sites, independent of the association with apple orchards.
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Printed in the USA 0730-7268/98 $6.00 �.00 THE FUNCTIONAL INTEGRITY OF NORTHERN LEOPARD FROG (Rana PIPIENS) AND GREEN FROG (Rana clamitans) POPULATIONS IN ORCHARD WETLANDS. II. EFFECTS OF PESTICIDES AND EUTROPHIC CONDITIONS ON EARLY LIFE STAGE DEVELO
1997Co-Authors: Megan L. Harris, Christine A Bishop, John Struger, Brian Ripley, James P BogartAbstract:Abstract—Premetamorphic northern leopard frogs (Rana pipiens) and green frogs (Rana clamitans) were evaluated at seven wetland sites, four of which were within apple orchards, to determine if environmental conditions associated with orchard management in southern Ontario, Canada, affected frog early development. Synchronous with breeding events (May–July), embryos and tadpoles were exposed, in situ and in the laboratory, to study site pond water for 2 to 3 weeks. Six pesticides commonly applied in apple orchards (Guthion � 50WP, Imidan � 50WP, Thiodan � 50WP, Dithane � DG, Nova � 40W, and Basudin � 500EC) and technical grade diazinon were also evaluated for direct toxicity to green frogs using continuous and discontinuous toxicity tests. Embryos and larvae exhibited poor hatching success and survival at some orchard sites during in situ assays, but no specific water source produced consistently poor developmental success. Reduced tadpole growth occurred at several study sites, showing no clear distinction between reference and orchard sites. Despite the collection of substantial environmental data, only surface water temperature appeared to be correlated with growth rates. Basudin 500EC, technical grade diazinon, and Dithane DG caused mortality, deformities, or growth inhibition during early development at environmentally relevant concentrations (�0.01 mg/L), whereas Imidan 50WP, Guthion 50WP, and Nova 40W produced survival or growth effects at much higher levels (5–10 mg/L). Dithan
