Influence of Temperature on the Thyroidogenic Effects of Diuron and Its Metabolite 3,4-DCA in Tadpoles of the American Bullfrog (Lithobates catesbeianus)

Abstract

Temperature is a key variable affecting the timing of amphibian metamorphosis from tadpoles to tetrapods, through the production and subsequent function of thyroid hormones (TH). Thyroid function can be impaired by environmental contaminants as well as temperature. Tadpoles can experience large temperature fluctuations in their habitats and many species are distributed in areas that may be impacted by agriculture. Diuron is a widely used herbicide detected in freshwater ecosystems and may impact endocrine function in aquatic organisms. We evaluated the influence of temperature (28 and 34 °C) on the action of diuron and its metabolite 3,4-dichloroaniline (3,4-DCA) on thyroid function and metamorphosis in tadpoles of Lithobates catesbeianus. Exposure to both compounds induced more pronounced changes in gene expression and plasma 3,3',5-triiodothyronine (T) concentrations in tadpoles treated at higher temperature. T concentrations were increased in tadpoles exposed to 200 ng/L of diuron at 34 °C and an acceleration of metamorphosis was observed for the same group. Transcriptomic responses included alteration of thyroid hormone induced bZip protein (thibz), deiodinases (dio2, dio3), thyroid receptors (trα, trβ) and Krüppel-like factor 9 (klf9), suggesting regulation by temperature on TH-gene expression. These results suggest that environmental temperature should be considered in risk assessments of environmental contaminants for amphibian species.

Influence of temperature on the antioxidant responses and lipid peroxidation of two species of tadpoles (Rhinella schneideri and Physalaemus nattereri) exposed to the herbicide sulfentrazone (Boral 500SC®)

“…The temperature of the tanks and individual aquariums had their values recorded daily to observe possible variations during the experimental period. Temperature values used in this study were based on Freitas et al (2016), which recorded the water temperature in 5 natural ponds in which tadpoles of R. schneideri and P. nattereri are frequently found. These data were recorded during the summer, which coincides with the rainy season and reproduction for most neotropical frogs.…”

“…Due to the small volume of water in ephemeral ponds, the water temperature is easily elevated, increasing the average temperatures and the daily thermal fluctuations. Previous studies have shown that the water temperature can exceed 40°C during the summer in ponds where several species of tadpoles have been found in Brazil (Freitas et al, 2016). The deforestation in nearby areas of amphibian habitats and the loss of vegetation has also favored the increase of solar incidence in these small ponds, thus contributing to the water heating.…”

“…Thus, changes in environmental temperature can interfere with many natural biological responses in different species, making the organisms more susceptible to the action of xenobiotics (Blaustein et al, 2010;Blaustein and Kiesecker, 2002;Moe et al, 2013). Previous studies have shown that temperature plays an important role in the toxicity of several pesticides for amphibians (Boone and Bridges, 1999;Freitas et al, 2016;Hammond et al, 2015). For example, the mortality of tadpoles of Rana clamitans exposed to the insecticide carbaryl was increased at lower concentrations when animals were exposed to higher temperatures (Boone and Bridges, 1999).…”

“…For example, the mortality of tadpoles of Rana clamitans exposed to the insecticide carbaryl was increased at lower concentrations when animals were exposed to higher temperatures (Boone and Bridges, 1999). Exposure of tadpoles of the American bullfrog (Lithobates catesbeianus) to the herbicide diuron and its metabolite 3,4-DCA also showed that thyroidogenic effects of both compounds were more pronounced in animals exposed at higher temperatures (Freitas et al, 2016).…”

Changes in thyroid status of Menidia beryllina exposed to the antifouling booster irgarol: Impacts of temperature and salinity

“…Regarding endocrine responses, the anti-estrogenic activity of irgarol was reported using a yeastbased in vitro assay (Westlund and Yargeau, 2017). Recent studies demonstrate that the antifouling booster diuron, which also acts in PSII, affect the thyroid system, growth, and development of aquatic organisms, including tadpoles American bullfrog Lithobates catesbeianus and the estuarine fish Menidia beryllina (Freitas et al, 2016;Moreira et al, 2018).…”