| Water Quality Influences Reproduction in Female Mosquitofish (Gambusia holbrooki) from Eight Florida Springs Thea M. Edwards, Hilary D. Miller, and Louis J. Guillette Jr. Department of Zoology, University of Florida, Gainesville, Florida, USA Abstract
Contamination of freshwater ecosystems with nitrate is a growing global concern. Although nitrate pollution is recognized as a cause of aquatic eutrophication, few studies have examined the possible physiological impacts of nitrate exposure. In this study, we surveyed several reproductive variables of viviparous female Gambusia holbrooki (Poeciliidae) captured from eight springs in Florida. The eight springs represent a gradient of nitrate contamination (1-5 mg/L nitrate-nitrogen) . We had two objectives in this study: to describe reproductive biology of female mosquitofish in the springs and to understand reproductive variation in the context of water quality, particularly the nitrate concentration. Our data show a significant negative association between nitrate and both dry weight of developing embryos and rate of reproductive activity among mature females. In addition, variation in Gambusia condition index and embryo number and dry weight was related to temperature variation, and hepatic weight was negatively related to dissolved oxygen concentration. Finally, we observed that many of the measured reproductive variables were interrelated and changeable, depending on gestational stage. Specifically, we provide evidence that maternal support of the embryo occurs at least during the first two thirds of gestation and that female fecundity is affected by an apparent tradeoff between embryo size and embryo number. Key words: endocrine disruption, fish, Gambusia, growth, larvae, matrotrophy, mosquitofish, nitrate, offspring, oxygen, reproduction, trade-off. Environ Health Perspect 114(suppl 1) :69-75 (2006) . doi:10.1289/ehp.8056 available via http://dx.doi.org/ [Online 21 October 2005]
This article is part of the monograph "The Ecological Relevance of Chemically Induced Endocrine Disruption in Wildlife." Address correspondence to T.M. Edwards, Department of Zoology, 223 Bartram Hall, PO Box 118525, University of Florida, Gainesville, FL 32611 USA. Telephone: (352) 392-1098. Fax: (352) 392-3704. E-mail: tedwards@zoo.ufl.edu. We are grateful for the superb help of R. Emrich and J.M. Thro. We also thank S. Keller, L. Chapman, B. Moore, and the many undergraduates in our laboratory. Funding was provided by the Florida Department of Environmental Protection (agreement no. S0028) . The views expressed herein are those of the authors and do not necessarily reflect the views of the Florida Department of Environmental Protection. The authors declare they have no competing financial interests. Received 31 January 2005 ; accepted 1 September 2005.
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