Estrogens, Endocrine Disruption, and Approaches to Assessing Gametogenesis and Reproductive Condition in Freshwater Mussels (Bivalvia: Unionidae)

Organisms belonging to the family Unionidae, commonly referred to as freshwater mussels, unionids, or pearly mussels, have, over the last several decades, experienced drastic declines in range and number.These declines have not been localized to a particular region and have not been specific to any particular environment or habitat, but have been experienced by a great number of the species belonging to this diverse group.While a variety of potentially causative factors have been implicated in the decline of Unionids worldwide, the possibility that environmental contaminants, including those identified or suspected as endocrine disrupting chemicals (EDCs), might contribute to observed unionid declines is central to this work.Unionid bivalves are long-lived, sessile creatures that, by actively filter feeding, are at risk of a high degree of exposure to water-borne xenobiotics.Ecotoxicological research on potential endocrine disruptive effects on bivalves, and in particular many unionids, however, presents a unique challenge due to the highly endangered, and thus protected, nature of many of these species and a, generally, limited ability to secure and maintain organisms for testing.The ability to assess effects of toxicant exposure in both laboratory and field studies on unionid reproductive condition and gametogenic development using minimally invasive and nonlethal methods is paramount to the ability to gain information for such species.Typical methods used to assess reproductive development and gametogenesis in bivalves focus on histological analyses, which have most always required organism sacrifice.Recent advances in nonlethal assessment and methodological developments focused on the utilization of nonlethal procedures has, however, provided a new avenue by which evaluation of potential exposure effects might be evaluated.Therefore, this I would also like to say thanks to all of the professionals and friends who have aided me in the successful completion of this work.In particular, thanks to my committee members, Dr. Susan Fisher, Dr. G. Thomas Watters, and Dr. Linda Weavers, for their efforts, advice, and time invested in this project.I also want to say a very special thank you to my wife, Megan Sovic.Her patience, love, and support over the course of this research effort have been immense and I very honestly could not have done this without her.From long hikes carrying heavy field equipment to spending days sitting in a cold river recording data and looking for mussels, she never failed to support me and my work, and for that I am eternally grateful.I also have the pleasure of recognizing