SREL Reprint #3809

Impact of developmental methylmercury exposure on avian embryonic development, hatchling growth, and survival

James C. Leaphart1,2, Sarah M. Chinn1,3, and James C. Beasley1

1Savannah River Ecology Laboratory, Warnell School of Forestry and Natural Resources,
University of Georgia, Aiken, SC, United States
2Department of Biology, University of North Georgia, Dahlonega, GA, United States
3Marine Mammal Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service,
National Oceanic and Atmospheric Administration, Seattle, WA, United States

Abstract: Methylmercury (MeHg) is a globally ubiquitous and persistent environmental toxicant that negatively affects animal behavior, health, and reproduction. In birds, MeHg is transferred from female to egg, contaminating embryos during sensitive stages of early embryonic development and growth. This toxic exposure in the prenatal environment not only induces mortality but also possible lasting impacts on physiology, health, and survival, even once hatched. The purpose of our study was to further elucidate the negative effects of MeHg exposure during avian embryonic development and explore how such exposure can impact offspring development, growth, and survival, both in ovo and posthatch. To assess this, we experimentally dosed fertile mallard and wood duck eggs with MeHg II chloride and reared developing embryos and ducklings to various endpoints. We found that embryos not only readily accumulated MeHg throughout incubation, but they also displayed varying dose-dependent disparities in body mass and morphometrics, with control individuals being larger during early and late embryonic stages of development (p<0.05). Furthermore, hatched offspring exposed to MeHg exhibited increasingly slower growth rates between 7 to 10 and 10 to 15 days posthatch (p<0.05), and were found to have lower survival probabilities both under controlled laboratory conditions (p<0.005), and in the natural environment (p<0.05). Our findings on the detrimental effects of MeHg on avian embryos and hatchlings emphasize the need for more proactive means of environmental protection and remediation to protect vulnerable avian populations and the ecosystems they inhabit.

Keywords: avian toxicity, embryotoxicity, heavy metals, mallards, wood ducks

SREL Reprint #3809

Leaphart, J. C., S. M. Chinn, and J. C. Beasley. 2025. Impact of developmental methylmercury exposure on avian embryonic development, hatchling growth, and survival. Environmental Toxicology and Chemistry 44(2): 432-443.

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