Glyphosate-based herbicides are among the most widely used pesticides in the world. We compared the acute toxicity of the glyphosate end-use formulation Roundup Original to four North American amphibian species (Rana clamitans, R. pipiens, R. sylvatica, and Bufo americanus) and the toxicity of glyphosate technical, the polyethoxylated tallowamine surfactant (POEA) commonly used in glyphosate-based herbicides, and five newer glyphosate formulations to R. clamitans. For R. clamitans, acute toxicity values in order of decreasing toxicity were POEA > Roundup Original > Roundup Transorb > Glyfos AU; no significant acute toxicity was observed with glyphosate technical material or the glyphosate formulations Roundup Biactive, Touchdown, or Glyfos BIO. Comparisons between the four amphibian species showed that the toxicity of Roundup Original varied with species and developmental stage. Rana pipiens tadpoles chronically exposed to environmentally relevant concentrations of POEA or glyphosate formulations containing POEA showed decreased snout-vent length at metamorphosis and increased time to metamorphosis, tail damage, and gonadal abnormalities. These effects may be caused, in some part, by disruption of hormone signaling, because thyroid hormone receptor beta mRNA transcript levels were elevated by exposure to formulations containing glyphosate and POEA. Taken together, the data suggest that surfactant composition must be considered in the evaluation of toxicity of glyphosate-based herbicides.

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Using field, molecular and histological methods, an epizootic, systemic disease causing death within wood frog Rana sylvatica tadpoles and leopard frog Rana pipiens metamorphs at 3 different locations within Southern Ontario, Canada, has been investigated. Our results demonstrated that the probable cause of this disease was a ranavirus. Affected amphibians were found to exhibit necrosis within the hematopoietic cells. Liver tissue samples were found positive for the virus by PCR amplification of the ranavirus (Family: Iridoviridae) major capsid protein (MCP). Positive samples were confirmed by sequence analysis. Clinically normal, laboratory-raised wood frog egg broods were also found to test weakly positive for ranavirus. The population effects of disease on these amphibian communities have not yet been conclusively associated with population declines, but warrant more focused consideration.KEY WORDS: Frog · Rana sylvatica · Rana pipiens · Ranavirus · Amphibian · Polymerase chain reaction · Canada Resale or republication not permitted without written consent of the publisherDis Aquat Org 67: [9][10][11][12][13][14] 2005 apparent that the infection and death of diverse groups of amphibians testing positive for ranavirus is a serious and potentially devastating occurrence.We report here on the recurring presence of a ranavirus in 3 amphibian populations in Southern Ontario, Canada. The objectives for this work were to determine whether a ranavirus was associated with 5 amphibian mortality events investigated in south central Ontario, Canada. We also examined potential transmission routes for the virus within these populations. MATERIALS AND METHODSField sites. Tadpoles and recent metamorphs were collected from 5 different sites within Southern Ontario. Field sites can be classified into 2 categories, namely (1) sites where disease was observed and subsequently investigated, and (2) sites where no disease was observed. Disease sites included the James Oliver Ecological Research Station ('Oliver Pond'; 44°31' N, 78°32' W), The Kortright Centre for Conservation ('Kortright Pond'; 43°57' N, 79°42' W) and Gannon's Narrows (44°38' N, 78°41' W). Sites that showed no signs of disease and were used as control sites included the Poplar Pond (44°31' N, 78°32' W) and the Trent University Archeology Pond (44°21' N, 78°17' W). To be considered a diseased site, ≥10 ind. had to meet the case definition. This meant that sick and/or dead individuals had to exhibit 4 of 7 clinical signs. Clinical signs included redness in the vent, abdomen, or legs, swollen vent, edema of the body cavity, cutaneous lesions, anorexia and loss of escape behaviour. The Oliver Pond location is unique because there have been 3 consecutive years of similar mass mortality events here. In May 2002, Rana sylvatica egg masses were collected from the Oliver Pond within 12 h of being laid and reared in the laboratory in 5 gallon (19 l) aquaria containing aged river water.Collection of animals. Live animals were transported back to the laboratory. ...

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Exposure of amphibians to endocrine disrupting compounds (EDCs) may alter differentiation of gonads, especially when exposures begin during early life stages. Gonadal differentiation was observed in leopard frogs (Rana pipiens) and wood frogs (Rana sylvatica) exposed as tadpoles to estrogenic (estradiol, ethinylestradiol, nonylphenol) and antiestrogenic compounds (an aromatase inhibitor, flavone, and an antiestrogen, ICI 182780). Exposure to all compounds at micrograms/L concentrations altered gonadal differentiation in some animals by inducing either complete feminization or an intersex condition, and altered testicular tubule morphology, increased germ cell maturation (vitellogenesis), and oocyte atresia. Comparisons between the two species indicate that R. pipiens are more susceptible to sex reversal and development of intersex gonads. However, R. sylvatica also showed alterations to testicular morphology, germ cell maturation, and ooctye atresia. These laboratory results indicate that amphibians could be susceptible to altered gonadal differentiation and development when exposed to estrogenic and antiestrogenic compounds in aquatic environments, such as those impacted by agricultural, industrial, and municipal runoff.