Uniform TitleEvidence of endocrine disruption in amphibians due to agricultural chemical exposure
NameGutierrez, Marisol M. (author), Robson, Mark (chair), Cooper, Keith (internal member), Reuhl, Kenneth (internal member), White, Lori (internal member), Ledoux, Thomas (outside member), Rutgers University, Graduate School - New Brunswick,
Frogs--Effect of chemicals on,
DescriptionIt is hypothesized that atrazine acts as an endocrine disruptor in amphibians, targeting male reproduction. To determine the impact of environmental atrazine on amphibians, we undertook a comprehensive study utilizing field and laboratory experimentation. In field studies utilizing Rana catesbeiana and R. clamitans melanota, we found evidence that secondary sexual traits are altered by environmental contamination. We also found that testes weights in both bullfrogs and green frogs were reduced at sites with chemical contamination compared to reference sites. At the histological level, renal and testicular dysgenesis were more prevalent at medium-contaminated sites than low or high. Ovotestes occurred most frequently (16.7%) at a site containing atrazine. The frequencies of renal parasites increased, while metacercarial cysts decreased with site contamination. Prevalence of hepatic and renal inflammation was higher in captures from medium and high contaminated sites compared to low. Bullfrog females from high contamination sites had reduced hematocrit than low and medium sites. In our field locations, there was evidence of endocrine disruption in frog populations. However, atrazine did not correlate well with observed effects; methoxychlor and metolachlor were associated with various endpoints.
To further identify the role of atrazine in developmental effects, we exposed Xenopus laevis tadpoles to environmental atrazine concentrations (0, 1, 5, 20, 60, 120 ppb) during their larval period. Many endpoints examined presented with non-monotonic responses. Tadpole survival was reduced only at 5 ppb atrazine. At 5 and 60 ppb atrazine, tadpoles reached metamorphosis earlier than controls. Atrazine concentrations 5, 20 and 60 ppb yielded smaller metamorphs than controls, and metamorphs from 5 ppb atrazine also had shorter body lengths, limbs and abdominal girth. Malformations of the spine and limbs were highest at 5 and 20 ppb atrazine. We also observed a lowest observable adverse effect level (LOAEL) of 1 ppb atrazine for testicular dysgenesis, which is within environmental levels and supports concerns regarding the herbicide's ability to hinder amphibian reproductive output. Overall, our research suggests that low environmentally relevant doses of atrazine have the ability to impact wild amphibians by altering endocrine processes.
NoteIncludes bibliographical references (p. 313-354).
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.