SREL Reprint #3850

Maternal deposition of hormones and contaminants shape the gonadal transcriptome in American alligators

Christopher R. Smaga1,2, Samantha L. Bock3, Josiah M. Johnson1,2, Ryan T. Paitz4, Andrew Letter5, Vincent Deem5, Arnold Brunell5, and Benjamin B. Parrott1,2

1Eugene P. Odum School of Ecology, University of Georgia, Athens, GA, USA
2Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, USA
3Kellogg Biological Station, Michigan State University, East Lansing, MI, USA
4School of Biological Sciences, Illinois State University, Normal, IL, USA
5Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, Gainesville, FL, USA

Abstract: Environmental conditions influence the maternal deposition of hormones into eggs, which is hypothesized to adaptively modify developmental outcomes in offspring. However, most ecosystems harbour environmental contaminants capable of disrupting endocrine signaling, and maternal exposure to these compounds has the potential to further alter offspring traits. Studies rarely examine maternally derived hormones and contaminants along with offspring phenotypes, and we know little about their interrelationships and potential interactions. Here, we measure yolk concentrations of 24 endocrine-disrupting compounds (EDCs) and 28 steroid hormones along with gonadal transcriptomes from two populations of the American alligator (Alligator mississippiensis) that differ in reproductive development and exposure to EDCs. Using a network-based approach, we identify gene expression modules associated with hormones and contaminants independently, in combination, or by potential indirect influences of EDCs on maternal hormone deposition. We find that yolk concentrations of both 17β-oestradiol and etiocholanolone differ across populations and explain substantial variation in gene expression. We further provide evidence for the indirect effect of the pesticide, methoxychlor, on gonadal gene expression through its relationship with 17β-oestradiol. Our results reveal novel pathways by which maternal exposure to environmental contaminants interacts with hormone provisioning to affect offspring sexual development.

Keywords: endocrine disruption, sexual development, developmental plasticity, estradiol, reproduction

SREL Reprint #3850

Smaga, C. R., S. L. Bock, J. M. Johnson, R. T. Paitz, A. Letter, V. Deem, A. Brunell, and B. B. Parrott. 2025. Maternal deposition of hormones and contaminants shape the gonadal transcriptome in American alligators. Proceedings of the Royal Society B 292(2039).

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).