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Jörg Oehlmann,¹ Ulrike Schulte-Oehlmann,¹ Jean Bachmann,¹ Matthias Oetken,¹ Ilka Lutz,² Werner Kloas,² and Thomas A. Ternes³

¹Johann Wolfgang Goethe University Frankfurt am Main, Department of Ecology and Evolution, Frankfurt am Main, Germany; ²Leibniz Institute of Freshwater Ecology and Inland Fisheries, Department of Inland Fisheries, Berlin, Germany; ³Federal Institute of Hydrology, Koblenz, Germany

Abstract
Previous investigations have shown that bisphenol A (BPA) induces a superfeminization syndrome in the freshwater snail Marisa cornuarietis at concentrations as low as 1 µg/L. Superfemales are characterized by the formation of additional female organs, enlarged accessory sex glands, gross malformations of the pallial oviduct, and a stimulation of egg and clutch production, resulting in increased female mortality. However, these studies were challenged on the basis of incomplete experimentation. Therefore, the objective of the current approach was to bridge several gaps in knowledge by conducting additional experiments. In an initial series of experiments, study results from the reproductive phase of the snails were evaluated in the sub-micrograms per liter range. Before and after the spawning season, superfemale responses were observed [NOEC (no observed effect concentration) 7.9 ng/L, EC₁₀ (effective concentration at 10%) 13.9 ng/L], which were absent during the spawning season. A further experiment investigated the temperature dependence of BPA responses by exposing snails at two temperatures in parallel. The adverse effect of BPA was at least partially masked at 27°C (EC₁₀ 998 ng/L) when compared with 20°C (EC₁₀ 14.8 ng/L) . In M. cornuarietis, BPA acts as an estrogen receptor (ER) agonist, because effects were completely antagonized by a co-exposure to tamoxifen and Faslodex. Antiandrogenic effects of BPA, such as a significant decrease in penis length at 20°C, were also observed. Competitive receptor displacement experiments indicate the presence of androgen- and estrogen-specific binding sites. The affinity for BPA of the estrogen binding sites in M. cornuarietis is higher than that of the ER in aquatic vertebrates. The results emphasize that prosobranchs are affected by BPA at lower concentrations than are other wildlife groups, and the findings also highlight the importance of exposure conditions. Key words: bisphenol A, endocrine disruptor, hazard assessment, low-dose effects, Marisa cornuarietis, prosobranchia, reproductive toxicity, superfemale, temperature, xenoestrogen. Environ Health Perspect 114(suppl 1) :127-133 (2006) . doi:10.1289/ehp.8065 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 J. Oehlmann, Johann Wolfgang Goethe University Frankfurt am Main, Department of Ecology and Evolution, Siesmayerstr. 70, D-60054 Frankfurt, Germany. Telephone: 49 69 798 24738. Fax: 49 69 798 24748. E-mail: oehlmann@zoology.uni-frankfurt.de

We are grateful to M. Duft, G. Elter, C. Stark, M. Tillmann, L. Weltje, and S. Ziebart for assistance, and also to two anonymous reviewers for their valuable comments.

Financial support was provided by the European Union (COMPRENDO project, contract EVK1-CT-2002-00129) and the Federal Environmental Agency Berlin (project code 297 65001/04) .

The authors declare they have no competing financial interests.

Received 31 January 2005 ; accepted 27 June 2005.