title: Methyltestosterone alters sex determination in the American alligator (Alligator mississippiensis).
abstract: Effects of xenobiotics can be organizational, permanently affecting anatomy during embryonic development, and/or activational, influencing transitory actions during adulthood. The organizational influence of endocrine-disrupting contaminants (EDC's) produces a wide variety of reproductive abnormalities among vertebrates that exhibit temperature-dependent sex determination (TSD). Typically, such influences result in subsequent activational malfunction, some of which are beneficial in aquaculture. For example, 17-αmethyltestosterone (MT), a synthetic androgen, is utilized in tilapia farming to bias sex ratio towards males because they are more profitable. A heavily male-biased hatchling sex ratio is reported from a crocodile population near one such tilapia operation in Guanacaste, Costa Rica. In this study we test the effects of MT on sexual differentiation in American alligators, which we used as a surrogate for all crocodilians. Experimentally, alligators were exposed to MT in ovo at standard ecotoxicological concentrations. Sexual differentiation was determined by examination of primary and secondary sex organs post hatching. We find that MT is capable of producing male embryos at temperatures known to produce females and demonstrate a dose-dependent gradient of masculinization. Embryonic exposure to MT results in hermaphroditic primary sex organs, delayed renal development and masculinization of the clitero-penis (CTP).
authors.affiliation: Department of Biological Sciences, Auburn University, 331 Funchess Hall, Auburn, AL 36849, USA. Electronic address: christopher.murray-2@selu.edu.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Murray
authors.affiliation: Everglades Holiday Park, Fort Lauderdale, FL 33332, USA. Electronic address: M.Easter05@gmail.com.
authors.forename: Michael
authors.initials: M
authors.lastname: Easter
authors.affiliation: Department of Chemistry, McNeese State University, Lake Charles, LA, USA. Electronic address: mmerchant@mcneese.edu.
authors.forename: Mark
authors.initials: M
authors.lastname: Merchant
authors.affiliation: Department of Natural Sciences, The University of Findlay, Findlay, OH 45840, USA. Electronic address: rheubert@findlay.edu.
authors.forename: Justin L
authors.initials: JL
authors.lastname: Rheubert
authors.affiliation: Department of Natural Sciences, The University of Findlay, Findlay, OH 45840, USA.
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Wilson
authors.affiliation: J. D. Murphree Wildlife Management Area, Texas Parks and Wildlife Department, Port Arthur, TX 77640, USA. Electronic address: amos.cooper@tpwd.state.tx.us.
authors.forename: Amos
authors.initials: A
authors.lastname: Cooper
authors.affiliation: Department of Biological Sciences, Auburn University, 331 Funchess Hall, Auburn, AL 36849, USA. Electronic address: mendomt@auburn.edu.
authors.forename: Mary
authors.initials: M
authors.lastname: Mendonça
authors.affiliation: Department of Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA. Electronic address: twibblels@uab.edu.
authors.forename: Thane
authors.initials: T
authors.lastname: Wibbels
authors.affiliation: Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica. Electronic address: msasamarin@gmail.com.
authors.forename: Mahmood Sasa
authors.initials: MS
authors.lastname: Marin
authors.affiliation: Department of Biological Sciences, Auburn University, 331 Funchess Hall, Auburn, AL 36849, USA. Electronic address: guyercr@auburn.edu.
authors.forename: Craig
authors.initials: C
authors.lastname: Guyer
mesh_terms: D000489:Alligators and Crocodiles; D000818:Animals; D005260:Female; D008297:Male; D008777:Methyltestosterone / Q000378:metabolism*; D012732:Sex Determination Analysis; D012733:Sex Differentiation
chemical_list: D008777:Methyltestosterone
keywords: Androgen; Crocodilian; Methyltestosterone; Temperature-dependent sex determination