1
|
Haskins DL, Brown MK, Meichner K, Tuberville TD, Gogal RM. Mercury immunotoxicity in the brown watersnake (Nerodia taxispilota): An in vitro study. J Appl Toxicol 2021; 42:180-189. [PMID: 34013568 DOI: 10.1002/jat.4200] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 04/30/2021] [Accepted: 05/03/2021] [Indexed: 11/08/2022]
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.
Collapse
Affiliation(s)
- David L Haskins
- Interdisciplinary Toxicology Program, University of Georgia, Athens, Georgia, USA.,D. B.Warnell School of Forestry and Natural Resources, University of Georgia, Athens, Georgia, USA.,University of Georgia's Savannah River Ecology Laboratory, Aiken, South Carolina, USA
| | - M Kyle Brown
- D. B.Warnell School of Forestry and Natural Resources, University of Georgia, Athens, Georgia, USA.,University of Georgia's Savannah River Ecology Laboratory, Aiken, South Carolina, USA
| | - Kristina Meichner
- Department of Pathology, University of Georgia's College of Veterinary Medicine, Athens, Georgia, USA
| | - Tracey D Tuberville
- University of Georgia's Savannah River Ecology Laboratory, Aiken, South Carolina, USA
| | - Robert M Gogal
- Department of Biosciences and Diagnostic Imaging, University of Georgia's College of Veterinary Medicine, Athens, Georgia, USA
| |
Collapse
|
2
|
Haskins DL, Brown MK, Qin C, Xu X, Pilgrim MA, Tuberville TD. Multi-decadal trends in mercury and methylmercury concentrations in the brown watersnake (Nerodia taxispilota). ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 276:116722. [PMID: 33640654 DOI: 10.1016/j.envpol.2021.116722] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 01/19/2021] [Accepted: 02/08/2021] [Indexed: 06/12/2023]
Abstract
Mercury (Hg) is an environmental contaminant that poses a threat to aquatic systems globally. Temporal evaluations of Hg contamination have increased in recent years, with studies focusing on how anthropogenic activities impact Hg bioavailability in a variety of aquatic systems. While it is common for these studies and ecological risk assessments to evaluate Hg bioaccumulation and effects in wildlife, there is a paucity of information regarding Hg dynamics in reptiles. The goal of this study was to investigate temporal patterns in total mercury (THg) and methylmercury (MeHg) concentrations across a 36-year period, as well as evaluate relationships among and between destructive (kidney, liver, muscle) and non-destructive (blood, tail) tissue types in a common watersnake species. To accomplish this, we measured THg and MeHg concentrations in multiple tissues from brown watersnakes (Nerodia taxispilota) collected from Steel Creek on the Savannah River Site (SRS; Aiken, SC, USA) from two time periods (1983-1986 and 2019). We found significant and positive relationships between tail tips and destructive tissues. In both time periods, THg concentrations varied significantly by tissue type, and destructive tissues exhibited higher but predictable THg values relative to tail tissue. Methylmercury concentrations did not differ among tissues from the 1980s but was significantly higher in muscle compared to other tissues from snakes collected in 2019. Percent MeHg of THg in N. taxispilota tissues mirrored patterns reported in other reptiles, although the range of % MeHg in liver and kidney differed between time periods. Both THg and MeHg concentrations in N. taxispilota declined significantly from the 1980s to 2019, with average values 1.6 to 4-fold lower in contemporary samples. Overall, our data add further evidence to the utility of watersnakes to monitor Hg pollution in aquatic environments and suggest attenuation of this contaminant in watersnakes in our study system.
Collapse
Affiliation(s)
- David L Haskins
- Interdisciplinary Toxicology Program, University of Georgia, Athens, GA, 30605, USA; Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, 30605, USA; Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, 29802, USA.
| | - M Kyle Brown
- Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, 30605, USA; Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, 29802, USA
| | - Chongyang Qin
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, 29802, USA
| | - Xiaoyu Xu
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, 29802, USA
| | - Melissa A Pilgrim
- Division of Natural Sciences and Engineering, University of South Carolina Upstate, Spartanburg, SC, 29303, USA
| | - Tracey D Tuberville
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, 29802, USA
| |
Collapse
|
3
|
Haskins DL, Gogal RM, Tuberville TD. Snakes as Novel Biomarkers of Mercury Contamination: A Review. REVIEWS OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2020; 249:133-152. [PMID: 30879139 DOI: 10.1007/398_2019_26] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Mercury (Hg) is an environmental contaminant that has been reported in many wildlife species worldwide. The organic form of Hg bioaccumulates in higher trophic levels, and thus, long-lived predators are at risk for higher Hg exposure. Although ecological risk assessments for contaminants such as Hg include pertinent receptor species, snakes are rarely considered, despite their high trophic status and potential to accumulate high levels of Hg. Our current knowledge of these reptiles suggests that snakes may be useful novel biomarkers to monitor contaminated environments. The few available studies show that snakes can bioaccumulate significant amounts of Hg. However, little is known about the role of snakes in Hg transport in the environment or the individual-level effects of Hg exposure in this group of reptiles. This is a major concern, as snakes often serve as important prey for a variety of taxa within ecosystems (including humans). In this review, we compiled and analyzed the results of over 30 studies to discuss the impact of Hg on snakes, specifically sources of exposure, bioaccumulation, health consequences, and specific scientific knowledge gaps regarding these moderate to high trophic predators.
Collapse
Affiliation(s)
- David L Haskins
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, USA.
- Interdisciplinary Toxicology Program, University of Georgia, Athens, GA, USA.
- Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, USA.
| | - Robert M Gogal
- Department of Biosciences and Diagnostic Imaging, College of Veterinary Medicine, University of Georgia, Athens, GA, USA
| | | |
Collapse
|
4
|
Beck ML, Thompson M, Hopkins WA. Repeatability and sources of variation of the bacteria-killing assay in the common snapping turtle. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2017; 327:293-301. [PMID: 29356460 DOI: 10.1002/jez.2089] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 06/16/2017] [Accepted: 07/10/2017] [Indexed: 01/13/2023]
Abstract
Research on reptile ecoimmunology lags behind that on other vertebrates, despite the importance of such studies for conservation and evolution. Because the innate immune system is highly conserved across vertebrate lineages, assessments of its performance may be particularly useful in reptiles. The bacteria-killing assay requires a single, small blood sample and quantifies an individual's ability to kill microorganisms. The assay's construct validity and interpretability make it an attractive measure of innate immunity, but it requires proper optimization and sample storage. We optimized this assay for the common snapping turtle (Chelydra serpentina) to assess the repeatability of the assay and the effects of freezing and thawing on bactericidal capacity. We determined whether age (adult female and hatchlings) or incubation temperature influenced bactericidal capacity. We found that the assay was repeatable and that freezing plasma samples for 6 weeks at -80°C did not decrease bactericidal capacity nor did a single 30-min thaw and subsequent refreezing. However, we detected subtle interassay variation and results from one assay were 5-6% greater than those from the other two. Adult females had significantly greater bactericidal ability than hatchlings and we found no relationship between incubation temperature and bactericidal capacity. This assay is a useful tool in snapping turtles and may have applicability in other reptiles. However, species-specific optimization is required to ensure that variation among individuals exceeds interassay variation. Consideration should be given to optimization conditions that facilitate comparisons between or within groups, particularly groups that differ considerably in bactericidal capacity.
Collapse
Affiliation(s)
- Michelle L Beck
- Department of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, Virginia
| | - Molly Thompson
- Department of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, Virginia
| | - William A Hopkins
- Department of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, Virginia
| |
Collapse
|
5
|
Korfel CA, Chamberlain JD, Gifford ME. A test of energetic trade-offs between growth and immune function in watersnakes. Oecologia 2015; 179:343-51. [DOI: 10.1007/s00442-015-3365-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 06/02/2015] [Indexed: 01/02/2023]
|