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Evidence of endocrine disruption in amphibians due to agricultural chemical exposure
Descriptive
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Title
Evidence of endocrine disruption in amphibians due to agricultural chemical exposure
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Gutierrez
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Marisol M.
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Marisol M. Gutierrez
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author
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Robson
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Mark
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Advisory Committee
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Mark G. Robson
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chair
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Cooper
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Keith
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Advisory Committee
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Keith R. Cooper
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Reuhl
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Kenneth
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Advisory Committee
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Kenneth R. Reuhl
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White
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Lori
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Advisory Committee
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Lori A. White
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internal member
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Ledoux
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Thomas
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Advisory Committee
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Thomas A. Ledoux
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outside member
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Rutgers University
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degree grantor
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Graduate School - New Brunswick
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theses
OriginInfo
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2007
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2007
Language
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English
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electronic
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application/pdf
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text/xml
Extent
xxii, 356 pages
Abstract
It 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.
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.
Note
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Ph.D.
Note
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Includes bibliographical references (p. 313-354).
Subject
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Topic
Toxicology
Subject
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Topic
Frogs--Reproduction--Environmental aspects
Subject
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Topic
Frogs--Effect of chemicals on
Subject
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Topic
Endocrine toxicology
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Graduate School - New Brunswick Electronic Theses and Dissertations
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rucore19991600001
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http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.16088
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ETD_488
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doi:10.7282/T36T0N20
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ETD doctoral
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Rights
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The author owns the copyright to this work.
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Copyright protected
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Open
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Marisol Gutierrez
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Rutgers University. Graduate School - New Brunswick
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Non-exclusive ETD license
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Author Agreement License
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I hereby grant to the Rutgers University Libraries and to my school the non-exclusive right to archive, reproduce and distribute my thesis or dissertation, in whole or in part, and/or my abstract, in whole or in part, in and from an electronic format, subject to the release date subsequently stipulated in this submittal form and approved by my school. I represent and stipulate that the thesis or dissertation and its abstract are my original work, that they do not infringe or violate any rights of others, and that I make these grants as the sole owner of the rights to my thesis or dissertation and its abstract. I represent that I have obtained written permissions, when necessary, from the owner(s) of each third party copyrighted matter to be included in my thesis or dissertation and will supply copies of such upon request by my school. I acknowledge that RU ETD and my school will not distribute my thesis or dissertation or its abstract if, in their reasonable judgment, they believe all such rights have not been secured. I acknowledge that I retain ownership rights to the copyright of my work. I also retain the right to use all or part of this thesis or dissertation in future works, such as articles or books.
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