The Prairie Pothole Region (PPR) of the United States supports a high density of
wetlands interspersed in an agricultural matrix. Row-crops, primarily corn and soybeans,
dominate the southern PPR, while small grains and grasslands typify the north. Recent
laboratory and field studies report that the corn herbicide atrazine disrupts normal sexual
development in amphibians. In 2005, we measured atrazine concentrations during three
surveys in 10 wetlands distributed from the southern (intensive corn production) to the
northern (sparse or no corn production) PPR and collected Rana pipiens (northern
leopard frog) metamorphs. Atrazine was detected in at least one water sample from
every wetland, with concentrations ranging from < 0.011 (i.e. < method nominal
detection limit) to 0.805 μg/L. The overall sex ratio did not diverge from 1:1; however
there was a strong negative correlation between average atrazine concentrations at each
site where more than 25 total specimens were collected and the female to male sex ratio.
Gross gonadal abnormalities were noted in 3% of all metamorphic R. pipiens. The
gonads of 55 % of all fully metamorphosed (Gosner stage 46) males contained testicular
oocytes (TO’s). Atrazine concentrations were not significantly correlated with gross
gonadal anomalies or TO’s. The lack of consistent, significant correlations between
atrazine concentrations and gonadal anomalies in R. pipiens does not support the
hypothesis linking atrazine with endocrine disruption in developing amphibians.
University of Minnesota Master of Science thesis. December 2009. Major: Biology. Advisor: Dr. Patrick K. Schoff. 1 computer file (PDF); vi, 28 pages.
Rohweder, Angela Kay.
Wetland Atrazine Concentrations and Occurrence of Testicular Oocytes in Rana pipiens from Randomly-Selected Sites in the Prairie Pothole Region.
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