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Kohno S, Vang D, Ang E, Brunell AM, Lowers RH, Schoenfuss HL. Estrogen-induced ovarian development is time-limited during the temperature-dependent sex determination of the American alligator. Gen Comp Endocrinol 2020; 291:113397. [PMID: 31991099 DOI: 10.1016/j.ygcen.2020.113397] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 12/14/2019] [Accepted: 01/20/2020] [Indexed: 11/16/2022]
Abstract
Many reptiles, including the American alligator, exhibit temperature-dependent sex determination (TSD), whose thermo-sensitive period for the female alligator begins at stages-15 and ends at stage-24. Estrogen signaling plays a central role in TSD, which can be overridden by an estrogen-exposure during the thermo-sensitive period. As some environmental contaminants are estrogenic, there is growing concern about their effects on the sex ratio and reproductive health of TSD-species. It is crucial to identify the timing of gonadal commitment to either ovary or testis for a better understanding of TSD and estrogen-signals. In the current study, eggs were exposed to 5 µg/g egg of 17β-estradiol (E2) or vehicle ethanol alone at three developmental stages-22, 24, and 26 at a male-promoting temperature, which produced 81% testis in all controls. E2-exposure at stages-22 and 24 induced more ovaries than the control group, whereas the exposure at stage-26 did not induce the same outcome. These results indicated that there is a critical commitment in the testicular development between the developmental stage 24 (100% ovary in E2 Exposure) and 26 (39% ovary with E2). Based on these results, we estimated a pivotal stage as stage-25.28. Thus, a gonadal commitment to testis could be later than a known temperature-sensitive period for promoting male in TSD.
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Affiliation(s)
- Satomi Kohno
- Aquatic Toxicology Lab, St. Cloud State University, St. Cloud, MN, USA.
| | - Donna Vang
- Aquatic Toxicology Lab, St. Cloud State University, St. Cloud, MN, USA; School of Health Science, Mayo Clinic, Rochester, MN, USA
| | - Edric Ang
- Aquatic Toxicology Lab, St. Cloud State University, St. Cloud, MN, USA
| | - Arnold M Brunell
- Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, Eustis, FL, USA
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Nilsen FM, Rainwater TR, Wilkinson PM, Brunell AM, Lowers RH, Bowden JA, Guillette LJ, Long SE, Schock TB. Examining maternal and environmental transfer of mercury into American alligator eggs. Ecotoxicol Environ Saf 2020; 189:110057. [PMID: 31835046 PMCID: PMC11005113 DOI: 10.1016/j.ecoenv.2019.110057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 12/02/2019] [Accepted: 12/05/2019] [Indexed: 06/10/2023]
Abstract
American alligators are exposed to mercury (Hg) throughout their natural range and may maternally transfer Hg into their eggs. Wildlife species are highly sensitive to Hg toxicity during embryonic development and neonatal life, and information on Hg transfer into eggs is critical when attempting to understand the effects of Hg exposure on developing oviparous organisms. To examine Hg transfer in alligators, the objectives of the present study were to 1) determine Hg concentrations in yolk (embryonic and neonatal food source) from wild alligator eggs collected from three locations - Yawkey Wildlife Center SC (YWC), Lake Apopka FL (LA), and Lake Woodruff FL (LW); 2) examine the relationship between THg concentrations in wild alligator nest material and egg yolk at Merritt Island National Wildlife Refuge, FL; 3) examine the Hg concentrations in wild maternal female alligators (blood) and the THg in corresponding egg yolks and embryos across three nesting seasons at a single location (YWC), and evaluate the relationship between nesting female THg concentrations (blood) and their estimated age and number of nesting years (YWC); and 4) assess the transfer of biologically-relevant Hg concentrations (based on Hg measured in maternal female blood) into embryos using an egg-dosing experiment. Mean total Hg (THg) concentrations observed at each site were 26.3 ng/g ± 11.0 ng/g (YWC), 8.8 ng/g ± 5.1 ng/g (LA), and 22.6 ng/g ± 6.3 ng/g (LW). No relationship was observed between THg in alligator nest material and corresponding yolk samples, nor between THg in maternal alligator blood and estimated age and number of nesting years of these animals. However, significant positive relationships were observed between THg in blood of nesting female alligators and THg in their corresponding egg yolk. We observed that 12.8% of the maternal blood THg is found in the corresponding egg yolk, and a highly significant correlation was observed between the two sample types (r = 0.66; p < 0.0001). The egg dosing experiment revealed that Hg did not transfer through the eggshell at developmental stage 19. Overall, this study provides new information regarding Hg transfer in American alligators which can improve biomonitoring efforts and may inform ecotoxicological investigations and population management programs in areas of high Hg contamination.
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Affiliation(s)
- Frances M Nilsen
- National Institute of Standards and Technology, Chemical Sciences Division, Hollings Marine Laboratory, Charleston, SC, USA; Medical University of South Carolina, Marine Bio-Medicine and Environmental Science Program, Charleston, SC, USA.
| | - Thomas R Rainwater
- Baruch Institute of Coastal Ecology and Forest Science, Clemson University, P.O. Box 596, Georgetown, SC, USA; Tom Yawkey Wildlife Center, South Carolina Department of Natural Resources, 1 Yawkey Way South, Georgetown, SC, USA.
| | - Phil M Wilkinson
- Tom Yawkey Wildlife Center, South Carolina Department of Natural Resources, 1 Yawkey Way South, Georgetown, SC, USA
| | - Arnold M Brunell
- Florida Fish & Wildlife Conservation Commission, 601 W. Woodward Ave., Eustis, FL, USA.
| | | | - John A Bowden
- National Institute of Standards and Technology, Chemical Sciences Division, Hollings Marine Laboratory, Charleston, SC, USA; Current Address- Center for Environmental and Human Toxicology, Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA.
| | - Louis J Guillette
- Medical University of South Carolina, Marine Bio-Medicine and Environmental Science Program, Charleston, SC, USA
| | - Stephen E Long
- National Institute of Standards and Technology, Chemical Sciences Division, Hollings Marine Laboratory, Charleston, SC, USA.
| | - Tracey B Schock
- National Institute of Standards and Technology, Chemical Sciences Division, Hollings Marine Laboratory, Charleston, SC, USA.
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Nilsen FM, Bowden JA, Rainwater TR, Brunell AM, Kassim BL, Wilkinson PM, Guillette LJ, Long SE, Schock TB. Examining toxic trace element exposure in American alligators. Environ Int 2019; 128:324-334. [PMID: 31078001 PMCID: PMC6857802 DOI: 10.1016/j.envint.2019.04.035] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 04/12/2019] [Accepted: 04/15/2019] [Indexed: 06/09/2023]
Abstract
Toxic trace element exposure occurs through release of the ubiquitous and naturally occurring elements arsenic (As), cadmium (Cd), lead (Pb), and mercury (Hg). The unique environmental conditions of the wetland ecosystems along the southeastern Atlantic coast of the United States lead to the accumulation of Hg which is greater than in most other ecosystems in the country. There are also point sources of As, Cd, and Pb in this region. To effectively monitor trace element concentrations, and consequently the potential human exposure, accessible local sentinel species are needed. In this study, concentrations of As, Cd, Pb, Hg and six other trace elements (Al, Ni, Cu, Zn, Se, Mo) were examined in American alligators (Alligator mississippiensis) from seven wetland sites in South Carolina and Florida and assessed for their utility as a sentinel species for human trace element exposure. Alligators were chosen as a potential sentinel as they share a common exposure with the local human population through their aquatic diet, and they are directly consumed commercially and through recreation hunting in this region. Sex was significantly related to the concentration of Zn, Mo, and Al, but not As, Pb, Hg, Cd, Se, or Cu. Site specific differences in element concentrations were observed for As, Pb, Hg, Cd, Se, Zn, and Mo. Size/age was significantly related to the element Hg and Pb concentrations observed. The observed concentration ranges for the four toxic elements, As (6-156 ng/g), Cd (0.3-1.3 ng/g), Pb (3-4872 ng/g), and Hg (39-2765 ng/g), were comparable to those previously reported in diverse human populations. In this region alligators are hunted recreationally and consumed by the local community, making them a vehicle of direct human toxic element exposure. We propose that the similarity in As, Cd, Pb, and Hg concentrations between alligators observed in this study and humans underscores how alligators can serve as a useful sentinel species for toxic element exposure.
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Affiliation(s)
- Frances M Nilsen
- National Institute of Standards and Technology, Chemical Sciences Division, Hollings Marine Laboratory, Charleston, SC, USA; Medical University of South Carolina, Marine Bio-medicine and Environmental Science Program, Charleston, SC, USA.
| | - John A Bowden
- National Institute of Standards and Technology, Chemical Sciences Division, Hollings Marine Laboratory, Charleston, SC, USA; Center for Environmental and Human Toxicology, Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA.
| | - Thomas R Rainwater
- Baruch Institute of Coastal Ecology and Forest Science, Clemson University, P.O. Box 596, Georgetown, SC, USA; Tom Yawkey Wildlife Center, South Carolina Department of Natural Resources, 1 Yawkey Way South, Georgetown, SC, USA
| | - Arnold M Brunell
- Florida Fish & Wildlife Conservation Commission, Eustis, FL, USA.
| | - Brittany L Kassim
- National Institute of Standards and Technology, Chemical Sciences Division, Hollings Marine Laboratory, Charleston, SC, USA
| | - Phil M Wilkinson
- Baruch Institute of Coastal Ecology and Forest Science, Clemson University, P.O. Box 596, Georgetown, SC, USA
| | - Louis J Guillette
- Medical University of South Carolina, Marine Bio-medicine and Environmental Science Program, Charleston, SC, USA
| | - Stephen E Long
- National Institute of Standards and Technology, Chemical Sciences Division, Hollings Marine Laboratory, Charleston, SC, USA.
| | - Tracey B Schock
- National Institute of Standards and Technology, Chemical Sciences Division, Hollings Marine Laboratory, Charleston, SC, USA.
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Nilsen FM, Kassim BL, Delaney JP, Lange TR, Brunell AM, Guillette LJ, Long SE, Schock TB. Trace element biodistribution in the American alligator (Alligator mississippiensis). Chemosphere 2017; 181:343-351. [PMID: 28456036 DOI: 10.1016/j.chemosphere.2017.04.102] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 04/17/2017] [Accepted: 04/21/2017] [Indexed: 06/07/2023]
Abstract
Routine monitoring of contaminant levels in wildlife is important for understanding chemical exposure and ultimately the link to ecosystem and human health. This is particularly important when the monitored species is recreationally hunted for human consumption. In the southeastern United States, recreational alligator harvesting takes place annually and in locations that are known to be contaminated with environmental pollutants. In this study, we investigated the biodistribution of trace elements in the American alligator (Alligator mississippiensis) from five sites in Florida, USA. These sites are locations where annual recreational alligator harvesting is permitted and two of the sites are identified as having high mercury contamination with human consumption advisories in effect. We utilized routinely collected monitoring samples (blood and scute), a commonly consumed tissue (muscle), and a classically analyzed tissue for environmental contaminants (liver) to demonstrate how the trace elements were distributed within the American alligator. We describe elemental tissue compartmentalization in an apex predator and investigate if noninvasive samples (blood and scute) can be used to estimate muscle tissue concentrations for a subset of elements measured. We found significant correlations for Hg, Rb, Se, Zn and Pb between noninvasive samples and consumed tissue and also found that Hg was the only trace metal of concern for this population of alligators. This study fills a gap in trace elemental analysis for reptilian apex predators in contaminated environments. Additionally, comprehensive elemental analysis of routinely collected samples can inform biomonitoring efforts and consumption advisories.
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Affiliation(s)
- Frances M Nilsen
- National Institute of Standards and Technology (NIST), Hollings Marine Laboratory, Charleston, SC 29412, USA; Department of Obstetrics and Gynecology and Marine Biomedicine and Environmental Sciences, Medical University of South Carolina (MUSC), Charleston, SC 29425-6190, USA.
| | - Brittany L Kassim
- National Institute of Standards and Technology (NIST), Hollings Marine Laboratory, Charleston, SC 29412, USA.
| | - J Patrick Delaney
- Florida Fish and Wildlife Conservation Commission, 601 W. Woodward Ave, Eustis, FL 32726, USA.
| | - Ted R Lange
- Florida Fish and Wildlife Conservation Commission, 601 W. Woodward Ave, Eustis, FL 32726, USA.
| | - Arnold M Brunell
- Florida Fish and Wildlife Conservation Commission, 601 W. Woodward Ave, Eustis, FL 32726, USA.
| | - Louis J Guillette
- Department of Obstetrics and Gynecology and Marine Biomedicine and Environmental Sciences, Medical University of South Carolina (MUSC), Charleston, SC 29425-6190, USA
| | - Stephen E Long
- National Institute of Standards and Technology (NIST), Hollings Marine Laboratory, Charleston, SC 29412, USA.
| | - Tracey B Schock
- National Institute of Standards and Technology (NIST), Hollings Marine Laboratory, Charleston, SC 29412, USA.
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Bangma JT, Bowden JA, Brunell AM, Christie I, Finnell B, Guillette MP, Jones M, Lowers RH, Rainwater TR, Reiner JL, Wilkinson PM, Guillette LJ. Perfluorinated alkyl acids in plasma of American alligators (Alligator mississippiensis) from Florida and South Carolina. Environ Toxicol Chem 2017; 36:917-925. [PMID: 27543836 PMCID: PMC5494598 DOI: 10.1002/etc.3600] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Revised: 06/09/2016] [Accepted: 08/18/2016] [Indexed: 05/21/2023]
Abstract
The present study aimed to quantitate 15 perfluoroalkyl acids (PFAAs) in 125 adult American alligators at 12 sites across the southeastern United States. Of those 15 PFAAs, 9 were detected in 65% to 100% of samples: perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnA), perfluorododecanoic acid, perfluorotridecanoic acid (PFTriA), perfluorotetradecanoic acid, perfluorohexanesulfonic acid (PFHxS), and perfluorooctane sulfonate (PFOS). Males (across all sites) showed significantly higher concentrations of 4 PFAAs: PFOS (p = 0.01), PFDA (p = 0.0003), PFUnA (p = 0.021), and PFTriA (p = 0.021). Concentrations of PFOS, PFHxS, and PFDA in plasma were significantly different among the sites in each sex. Alligators at both Merritt Island National Wildlife Refuge (FL, USA) and Kiawah Nature Conservancy (SC, USA) exhibited some of the highest PFOS concentrations (medians of 99.5 ng/g and 55.8 ng/g, respectively) in plasma measured to date in a crocodilian species. A number of positive correlations between PFAAs and snout-vent length were observed in both sexes, suggesting that PFAA body burdens increase with increasing size. In addition, several significant correlations among PFAAs in alligator plasma may suggest conserved sources of PFAAs at each site throughout the greater study area. The present study is the first to report PFAAs in American alligators, to reveal potential PFAA hot spots in Florida and South Carolina, and to provide a contaminant of concern when assessing anthropogenic impacts on ecosystem health. Environ Toxicol Chem 2017;36:917-925. Published 2016 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.
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Affiliation(s)
- Jacqueline T. Bangma
- Department of Obstetrics and Gynecology, Medical University of South Carolina, Charleston, South Carolina, USA
| | - John A. Bowden
- Hollings Marine Laboratory, Chemical Sciences Division, National Institute of Standards and Technology, Charleston, South Carolina, USA
| | - Arnold M. Brunell
- Florida Fish and Wildlife Conservation Commission, Eustis, Florida, USA
| | - Ian Christie
- Grice Marine Laboratory, College of Charleston, Charleston, South Carolina, USA
| | | | - Matthew P. Guillette
- Department of Obstetrics and Gynecology, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Martin Jones
- Department of Mathematics, College of Charleston, Charleston, South Carolina, USA
| | - Russell H. Lowers
- Integrated Mission Support Service, Kennedy Space Center, Titusville, Florida, USA
| | - Thomas R. Rainwater
- Baruch Institute of Coastal Ecology and Forest Science, Clemson University, Georgetown, South Carolina, USA
| | - Jessica L. Reiner
- Hollings Marine Laboratory, Chemical Sciences Division, National Institute of Standards and Technology, Charleston, South Carolina, USA
- Address correspondence to
| | | | - Louis J. Guillette
- Department of Obstetrics and Gynecology, Medical University of South Carolina, Charleston, South Carolina, USA
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Nilsen FM, Parrott BB, Bowden JA, Kassim BL, Somerville SE, Bryan TA, Bryan CE, Lange TR, Delaney JP, Brunell AM, Long SE, Guillette LJ. Global DNA methylation loss associated with mercury contamination and aging in the American alligator (Alligator mississippiensis). Sci Total Environ 2016; 545-546:389-97. [PMID: 26748003 PMCID: PMC4972023 DOI: 10.1016/j.scitotenv.2015.12.059] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Revised: 12/10/2015] [Accepted: 12/13/2015] [Indexed: 04/13/2023]
Abstract
Mercury is a widespread environmental contaminant with exposures eliciting a well-documented catalog of adverse effects. Yet, knowledge regarding the underlying mechanisms by which mercury exposures are translated into biological effects remains incomplete. DNA methylation is an epigenetic modification that is sensitive to environmental cues, and alterations in DNA methylation at the global level are associated with a variety of diseases. Using a liquid chromatography tandem mass spectrometry-based (LC-MS/MS) approach, global DNA methylation levels were measured in red blood cells of 144 wild American alligators (Alligator mississippiensis) from 6 sites with variable levels of mercury contamination across Florida's north-south axis. Variation in mercury concentrations measured in whole blood was highly associated with location, allowing the comparison of global DNA methylation levels across different "treatments" of mercury. Global DNA methylation in alligators across all locations was weakly associated with increased mercury exposure. However, a much more robust relationship was observed in those animals sampled from locations more highly contaminated with mercury. Also, similar to other vertebrates, global DNA methylation appears to decline with age in alligators. The relationship between age-associated loss of global DNA methylation and varying mercury exposures was examined to reveal a potential interaction. These findings demonstrate that global DNA methylation levels are associated with mercury exposure, and give insights into interactions between contaminants, aging, and epigenetics.
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Affiliation(s)
- Frances M Nilsen
- National Institute of Standards and Technology, Chemical Sciences Division, Environmental Chemical Sciences Group, Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, SC 29412, United States; Medical University of South Carolina, Marine Biomedicine and Environmental Sciences, 221 Fort Johnson Road, Charleston, SC 29412, United States; Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, SC 29412, United States.
| | - Benjamin B Parrott
- Medical University of South Carolina, Marine Biomedicine and Environmental Sciences, 221 Fort Johnson Road, Charleston, SC 29412, United States; Department of Obstetrics and Gynecology, Medical University of South Carolina, Charleston, SC 29403, United States; Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, SC 29412, United States
| | - John A Bowden
- National Institute of Standards and Technology, Chemical Sciences Division, Environmental Chemical Sciences Group, Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, SC 29412, United States; Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, SC 29412, United States
| | - Brittany L Kassim
- National Institute of Standards and Technology, Chemical Sciences Division, Environmental Chemical Sciences Group, Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, SC 29412, United States; Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, SC 29412, United States
| | - Stephen E Somerville
- Medical University of South Carolina, Marine Biomedicine and Environmental Sciences, 221 Fort Johnson Road, Charleston, SC 29412, United States; Department of Obstetrics and Gynecology, Medical University of South Carolina, Charleston, SC 29403, United States; Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, SC 29412, United States
| | - Teresa A Bryan
- Medical University of South Carolina, Marine Biomedicine and Environmental Sciences, 221 Fort Johnson Road, Charleston, SC 29412, United States; Department of Obstetrics and Gynecology, Medical University of South Carolina, Charleston, SC 29403, United States; Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, SC 29412, United States
| | - Colleen E Bryan
- National Institute of Standards and Technology, Chemical Sciences Division, Environmental Chemical Sciences Group, Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, SC 29412, United States; Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, SC 29412, United States
| | - Ted R Lange
- Florida Fish and Wildlife Conservation Commission, 601 W. Woodward Ave, Eustis, FL 32726, United States
| | - J Patrick Delaney
- Deseret Ranches- 13754 Deseret Lane, St. Cloud, Florida 34773-9381, United States
| | - Arnold M Brunell
- Florida Fish and Wildlife Conservation Commission, 601 W. Woodward Ave, Eustis, FL 32726, United States
| | - Stephen E Long
- National Institute of Standards and Technology, Chemical Sciences Division, Environmental Chemical Sciences Group, Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, SC 29412, United States; Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, SC 29412, United States
| | - Louis J Guillette
- Medical University of South Carolina, Marine Biomedicine and Environmental Sciences, 221 Fort Johnson Road, Charleston, SC 29412, United States; Department of Obstetrics and Gynecology, Medical University of South Carolina, Charleston, SC 29403, United States; Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, SC 29412, United States
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