SREL Reprint #3650

Mercury immunotoxicity in the brown watersnake (Nerodia taxispilota): An in vitro study

David L. Haskins1,2,3, M. Kyle Brown2,3, Kristina Meichner4, Tracey D. Tuberville3, and Robert M. Gogal Jr5

1Interdisciplinary Toxicology Program, University of Georgia, Athens, Georgia, USA
2D. B.Warnell School of Forestry and Natural Resources, University of Georgia, Athens, Georgia, USA
3University of Georgia's Savannah River Ecology Laboratory, Aiken, South Carolina, USA
4Department of Pathology, University of Georgia's College of Veterinary Medicine, Athens, Georgia, USA
5Department of Biosciences and Diagnostic Imaging, University of Georgia's College of Veterinary Medicine,
Athens, Georgia, USA

Abstract: Mercury (Hg) is a heavy metal that enters the environment through natural and anthropogenic means. Once in the environment, Hg can biomagnify in food webs and is known to cause immunotoxic effects to wildlife. Compared with other vertebrates, knowledge of the reptilian immune system is lacking, especially in snakes. Further, even less is known about the impact of environmental contaminants on snake immunity. This gap in knowledge is largely due to an absence of established immune-based assays or specific reagents for these species. In this study, brown watersnakes (Nerodia taxispilota; n = 23) were captured on the Savannah River (Augusta, Georgia, USA), weighed, measured, bled, and released. Peripheral blood leukocytes (24 h old) were enriched and evaluated with an established mammalian in vitro lymphocyte proliferation assay. Enriched leukocytes were then exposed to mercury chloride (HgCl2) at 3.75, 37.5, and 75 µM. Total mercury (THg) in whole blood was also quantified. Snake peripheral blood leukocyte enrichment yielded >90% lymphocytes with viabilities averaging >70%. Exposure to HgCl2 resulted in significant dose-dependent suppression of proliferative responses relative to spontaneous proliferation at 37.5 and 75 µM (both p ≤ 0.01) but not 3.75 µM (p = 0.99). Mean ± 1 SE concentration of THg in whole blood was 0.127 ± 0.027 mg/kg (wet weight). Based on the in vitro findings with HgCl2, snakes in systems with heavy Hg pollution may be at risk of immunosuppression, but N. taxispilota at the site in this study appear to be at low risk.

Keywords: immunotoxicity, in vitro, mercury, peripheral blood collection, snake

SREL Reprint #3650

Haskins, D. L., M. K. Brown, K. Meichner, T. D. Tuberville, and R. M. Gogal Jr. 2021. Mercury immunotoxicity in the brown watersnake (Nerodia taxispilota): An in vitro study. Journal of Applied Toxicology 42(2): 180-189.

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