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Food levels were adjusted as the animals grew to maximize growth. 1, we exposed larvae to atrazine at nominal concentrations of 0.01, 0.1, 1.0, 10.0, and 25 parts per billion (ppb), whereas the second experiment used 0.1, 0.4, 0.8, 1.0, 25, and 200 ppb atrazine.Concentrations were confirmed by two independent laboratories (PTRL West, Richmond, CA, and the Iowa Hygienic Laboratory, Univ. All stock solutions were made in ethanol (10 ml), mixed in 15-gallon containers, and dispensed into treatment tanks.Each animal was weighed to the nearest 0.002 g on a Mettler AT 261 Delta Range balance and its total length was measured to the nearest 0.5 mm.Animals were anesthetized in 0.2% benzocaine (Sigma), assigned a unique identification number, fixed in Bouins' fixative, and preserved in 70% ethanol until further analysis.
The effective levels reported in the current study are realistic exposures that suggest that other amphibian species exposed to atrazine in the wild could be at risk of impaired sexual development.
This widespread compound and other environmental endocrine disruptors may be a factor in global amphibian declines. Atrazine has been used for over 40 years and currently it is used in more than 80 countries.
In the last 10 years, a great deal of attention has focused on the global presence of endocrine-disrupting contaminants in the environment (1, 2). Department of Agriculture reports that more than 30,000 tons (60 million pounds) are used annually in the U. Despite its widespread intensive use, atrazine is considered safe because of its short half-life and negligible bioaccumulation and biomagnification (13).
In all experiments, all treatments and analyses were conducted blindly with color-coded tanks and treatments and number-coded specimens.
At metamorphosis (complete tail reabsorption—Niewkwoop–Faber Stage 66), the date was recorded for each animal.