Journal ArticleDOI
Effects of sublethal concentrations of atrazine and nitrate on metamorphosis of the African clawed frog
TLDR
The results indicate that environmentally realistic concentrations of atrazine exert a negative impact on amphibian metamorphosis and suggests that mixtures of agricultural chemicals, even if sublethal, may exert negative and not necessarily consistent mixture effects.Abstract:
Tadpoles of the African clawed frog (Xenopus laevis) were exposed to sublethal concentrations of atrazine (0, 40, and 320 microg/L) and nitrate (0, 37, and 292 mg/L) from feeding stage to metamorphosis. A 3 x 3 factorial design was used to identify both single and interactive effects. At metamorphosis, tadpole weight, snout-vent length (SVL), and hematocrit were determined. Mean mortality was greater in tanks receiving 320 microg/L atrazine; nitrate had no effect on mortality. Significant differences for all mean traits at metamorphosis occurred among atrazine treatments; higher atrazine exposure increased time to metamorphosis and decreased weight, SVL, and hematocrit. Nitrate treatments were not significantly different. Significant interaction tests between atrazine and nitrate occurred for weight and SVL at metamorphosis; the specific type of interaction varied among treatments. Assuming an additive mixture model, at low atrazine (40 microg/L), the addition of 37 mg/L nitrate produced SVL values less than expected (a synergistic effect) while the addition of 292 mg/L nitrate yielded SVL values greater than expected (an antagonistic effect). A similar response was noted for tadpoles in the 320-microg/L atrazine treatments. These results indicate that environmentally realistic concentrations of atrazine exert a negative impact on amphibian metamorphosis. Also, this study suggests that mixtures of agricultural chemicals, even if sublethal, may exert negative and not necessarily consistent mixture effects.read more
Citations
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Journal ArticleDOI
Nitrate toxicity to aquatic animals: a review with new data for freshwater invertebrates.
TL;DR: Nitrate toxicity to aquatic animals increases with increasing nitrate concentrations and exposure times, and may decrease with increasing body size, water salinity, and environmental adaptation; however, early developmental stages of some marine invertebrates may be so susceptible to nitrate as sensitive freshwater invertebrate.
Journal ArticleDOI
Pesticide mixtures, endocrine disruption, and amphibian declines: are we underestimating the impact?
Tyrone B. Hayes,Paola Case,Sarah Chui,Duc Chung,Cathryn Haeffele,Kelly Haston,Melissa Lee,Vien Phoung Mai,Youssra Marjuoa,John E. Parker,Mable Tsui +10 more
TL;DR: Estimating ecological risk and the impact of pesticides on amphibians using studies that examine only single pesticides at high concentrations may lead to gross underestimations of the role of pesticides in amphibian declines.
Journal ArticleDOI
Amphibians and agricultural chemicals: Review of the risks in a complex environment
TL;DR: This review examines some of the issues relating to exposure of amphibian populations to these chemicals and places emphasis on mechanisms of toxicity, including those that may disrupt thyroid activity, retinoid pathways, and sexual differentiation.
Journal ArticleDOI
The cause of global amphibian declines: a developmental endocrinologist's perspective
TL;DR: There is probably not a single cause for global amphibian declines and the role of pathogens in inducing diseases that cause death is profoundly affected by four other ultimate factors: atmospheric change, environmental pollutants, habitat modification and invasive species.
Journal ArticleDOI
A qualitative meta-analysis reveals consistent effects of atrazine on freshwater fish and amphibians.
Jason R. Rohr,Krista A. McCoy +1 more
TL;DR: A qualitative meta-analysis on the effects of ecologically relevant atrazine concentrations on amphibian and fish survival, behavior, metamorphic traits, infections, and immune, endocrine, and reproductive systems identified several consistent effects that must be weighed against any of its benefits and the costs and benefits of alternatives toAtrazine use.
References
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Journal Article
A simplified table for staging anuran embryos and larvae with notes on identification
TL;DR: A simplified table adequate for staging "generalized" developmental series will be presented, which is original only to the extent that it is a simplification of those already in existence.
Journal ArticleDOI
Ecological Aspects of Amphibian Metamorphosis: Nonnormal distributions of competitive ability reflect selection for facultative metamorphosis.
Henry M. Wilbur,James P. Collins +1 more
TL;DR: It is proposed that as development proceeds, variation in exponential growth coefficients causes a trend from a normal distribution to a skewed distribution of body sizes, and the relation between the ecological model and the physiological mechanisms that initiate metamorphosis can only be suggested.
Journal ArticleDOI
Hermaphroditic, demasculinized frogs after exposure to the herbicide atrazine at low ecologically relevant doses.
Tyrone B. Hayes,Atif Collins,Melissa Lee,Magdelena Mendoza,Nigel C. Noriega,A Ali Stuart,Aaron Vonk +6 more
TL;DR: It is hypothesize that atrazine induces aromatase and promotes the conversion of testosterone to estrogen and likely explains the demasculinization of the male larynx and the production of hermaphrodites.
Journal ArticleDOI
Ecological risk assessment of atrazine in North American surface waters.
Keith R. Solomon,David B. Baker,R. Peter Richards,Kenneth R. Dixon,Stephen J. Klaine,Thomas W. La Point,Ronald J. Kendall,Carol P. Weisskopf,Jeffrey M. Giddings,John P. Giesy,Lenwood W. Hall,W. Marty Williams +11 more
TL;DR: In this paper, an expert panel was convened to conduct a comprehensive aquatic ecological risk assessment based on several newly suggested procedures and included exposure and hazard subcomponents as well as the overall risk assessment.
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Time and size at metamorphosis related to adult fitness in Ambystoma talpoideum
TL;DR: Results demonstrate a direct relationship between phenotypic variation generated in the larval stage and adult traits closely associated with an individual's fitness.