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Walden MA, Loope KJ, Hunter EA, Divers SJ, Comolli JR, Esque TC, Shoemaker KT. Testosterone identifies hatchling sex for Mojave desert tortoises (Gopherus agassizii). Sci Rep 2023; 13:14818. [PMID: 37684318 PMCID: PMC10491821 DOI: 10.1038/s41598-023-41677-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Accepted: 08/30/2023] [Indexed: 09/10/2023] Open
Abstract
The threatened Mojave desert tortoise (Gopherus agassizii) exhibits temperature-dependent sex determination, and individuals appear externally sexually monomorphic until sexual maturity. A non-surgical sex identification method that is suitable for a single in situ encounter with hatchlings is essential for minimizing handling of wild animals. We tested (1) whether plasma testosterone quantified by enzyme-linked immunosorbent assay differentiated males from females in 0-3 month old captive hatchlings, and (2) whether an injection of follicle-stimulating hormone (FSH) differentially elevates testosterone in male hatchlings to aid in identifying sex. We validated sex by ceolioscopic (laparoscopic) surgery. We then fit the testosterone concentrations to lognormal distributions and identified the concentration below which individuals are more likely female, and above which individuals are more likely male. Using a parametric bootstrapping procedure, we estimated a 0.01-0.04% misidentification rate for naïve testosterone samples, and a 1.26-1.39% misidentification rate for challenged (post-FSH injection) testosterone samples. Quantification of plasma testosterone concentration from small volume (0.1 mL) blood samples appears to be a viable, highly accurate method to identify sex of 0-3 month old hatchlings and could be a valuable tool for conservation measures and investigation of trends and variation in sex ratios for in situ wild nests.
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Affiliation(s)
- M A Walden
- Department of Natural Resources and Environmental Science, University of Nevada, Reno, Reno, NV, USA.
- Department of Fisheries Biology, California State Polytechnic University, Humboldt, Arcata, CA, USA.
| | - Kevin J Loope
- Department of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, VA, USA
- Department of Biology, Georgia Southern University, Statesboro, GA, USA
| | - Elizabeth A Hunter
- U.S. Geological Survey, Virginia Cooperative Fish and Wildlife Research Unit, Department of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, VA, USA
| | - Stephen J Divers
- Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, GA, USA
| | - Jessica R Comolli
- Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, GA, USA
- Department of Veterinary Services, Miami Seaquarium, Key Biscayne, FL, USA
| | - Todd C Esque
- U.S. Geological Survey, Western Ecological Research Center, Boulder City, NV, USA
| | - Kevin T Shoemaker
- Department of Natural Resources and Environmental Science, University of Nevada, Reno, Reno, NV, USA
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Corniuk RN, Lynch JM, Arendt MD, Braun-McNeill J, Owens DW, Valverde RA, Kucklick JR, McClellan-Green PD. Using Plasma Vitellogenin in Loggerhead Sea Turtles to Assess Reproductive Maturation and Estrogen-Like Contaminant Exposure. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2023; 42:1309-1325. [PMID: 36942377 DOI: 10.1002/etc.5612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Revised: 03/09/2023] [Accepted: 03/16/2023] [Indexed: 05/09/2023]
Abstract
Vitellogenin (VTG), an egg yolk precursor, is abnormally produced by male and juvenile oviparous species after exposure to estrogens. Plasma VTG in loggerhead sea turtles (Caretta caretta) helped us understand their reproductive maturation and investigate it as a biomarker of contaminant exposure. The presence of VTG was screened in plasma from 404 loggerheads from the northwestern Atlantic Ocean using a freshwater turtle antibody in western blots. The concentrations of VTG were semiquantified using band intensities calibrated to results from a loggerhead antibody enzyme-linked immunoassay. The detection and concentrations of VTG were in (from highest to lowest): nesting females, in-water adult females, subadult females, smaller females, unknown sex, and males. Loggerheads from this region begin vitellogenesis at ≅77 cm straight carapace length. We classified VTG expression as abnormal in nine male or juvenile turtles. Organochlorine contaminant (OC) concentrations were measured in blood and/or fat biopsies of some turtles. One abnormal VTG female had the second highest fat polychlorinated biphenyl (PCB) and 4,4'-dichlorodiphenyldichloroethylene concentrations compared among 43 VTG-negative juveniles. The nine VTG-abnormal turtles had average blood PCB concentrations 8.5% higher, but not significantly different, than 46 VTG-negative juveniles (p = 0.453). In turtles less than 77 cm, blood PCB concentrations were significantly, but weakly, correlated with semiquantified VTG concentrations (tau = 0.1, p = 0.004). Greater blood OC concentrations were found in adult females than in males, which motivated the creation of a conceptual model of OC, VTG, and hormone concentrations across a reproductive cycle. A decision tree is also provided incorporating VTG as a sexing tool. Abnormal VTG expression cannot conclusively be linked to endocrine disruption caused by these OC concentrations. Studies should further investigate causes of abnormal VTG expression in wild sea turtles. Environ Toxicol Chem 2023;00:1-18. © 2023 SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.
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Affiliation(s)
| | - Jennifer M Lynch
- National Institute of Standards and Technology, Waimanalo, Hawaii, USA
- Duke University Marine Laboratory, Beaufort, North Carolina, USA
| | - Michael D Arendt
- Marine Resources Division, South Carolina Department of Natural Resources, Charleston, South Carolina, USA
| | | | - David W Owens
- College of Charleston, Charleston, South Carolina, USA
| | - Roldán A Valverde
- Southeastern Louisiana University, Hammond, Louisiana, USA
- Sea Turtle Conservancy, Gainesville, Florida, USA
| | - John R Kucklick
- National Institute of Standards and Technology, Charleston, South Carolina, USA
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Gatto CR, Williamson SA, Reina RD. Mitigating the effects of climate change on the nests of sea turtles with artificial irrigation. CONSERVATION BIOLOGY : THE JOURNAL OF THE SOCIETY FOR CONSERVATION BIOLOGY 2023; 37:e14044. [PMID: 36661082 PMCID: PMC10108123 DOI: 10.1111/cobi.14044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 09/28/2022] [Accepted: 10/06/2022] [Indexed: 06/17/2023]
Abstract
For sea turtles, like many oviparous species, increasing temperatures during development threaten to increase embryonic mortality, alter offspring quality, and potentially create suboptimal primary sex ratios. Various methods are being implemented to mitigate the effects of climate change on reproductive success, but these methods, such as breeding programs, translocations, and shading, are often invasive and expensive. Irrigation is an alternative strategy for cooling nests that, depending on location, can be implemented relatively quickly and cheaply. However, multiple factors, including ambient conditions, nest substrate, and species characteristics, can influence irrigation success. Additionally, irrigation can vary in duration, frequency, and the volume of water applied to nests, which influences the cooling achieved and embryonic survival. Thus, it is critical to understand how to maximize cooling and manage risks before implementing irrigation as a nest-cooling strategy. We reviewed the literature on nest irrigation to examine whether artificial irrigation is feasible as a population management tool. Key factors that affected cooling were the volume of water applied and the frequency of applications. Embryonic responses varied with species, ambient conditions, and the timing of irrigation during development. Nest inundation was the key risk to a successful irrigation regime. Future irrigation regimes must identify clear targets, either primary or adult sex ratios, that maximize population viability. Monitoring population responses and adjusting the irrigation regime in response to population characteristics will be critical. Most studies reported on the manipulation of only one or two variables, further research is required to understand how altering multiple factors in an irrigation regime influences the cooling achieved and embryonic responses.
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Affiliation(s)
| | - Sean A. Williamson
- School of Biological SciencesFlorida Atlantic UniversityBoca RatonFloridaUSA
| | - Richard D. Reina
- School of Biological SciencesMonash UniversityClaytonVictoriaAustralia
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A Cautionary Tale of Sexing by Methylation: Hybrid Bisulfite-Conversion Sequencing of Immunoprecipitated Methylated DNA in Chrysemys picta Turtles with Temperature-Dependent Sex Determination Reveals Contrasting Patterns of Somatic and Gonadal Methylation, but No Unobtrusive Sex Diagnostic. Animals (Basel) 2022; 13:ani13010117. [PMID: 36611726 PMCID: PMC9817949 DOI: 10.3390/ani13010117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Revised: 12/22/2022] [Accepted: 12/23/2022] [Indexed: 12/29/2022] Open
Abstract
Background: The gonads of Chrysemys picta, a turtle with temperature-dependent sex determination (TSD), exhibit differential DNA methylation between males and females, but whether the same is true in somatic tissues remains unknown. Such differential DNA methylation in the soma would provide a non-lethal sex diagnostic for TSD turtle hatchings who lack visually detectable sexual dimorphism when young. Methods: Here, we tested multiple approaches to study DNA methylation in tail clips of Chrysemys picta hatchlings, to identify differentially methylated candidate regions/sites that could serve as molecular sex markers To detect global differential methylation in the tails we used methylation-sensitive ELISA, and to test for differential local methylation we developed a novel hybrid method by sequencing immunoprecipitated and bisulfite converted DNA (MeDIP-BS-seq) followed by PCR validation of candidate regions/sites after digestion with a methylation-sensitive restriction enzyme. Results: We detected no global differences in methylation between males and females via ELISA. While we detected inter-individual variation in DNA methylation in the tails, this variation was not sexually dimorphic, in contrast with hatchling gonads. Conclusions: Results highlight that differential DNA methylation is tissue-specific and plays a key role in gonadal formation (primary sexual development) and maintenance post-hatching, but not in the somatic tail tissue.
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Monsinjon JR, Guillon JM, Wyneken J, Girondot M. Thermal reaction norm for sexualization: The missing link between temperature and sex ratio for temperature-dependent sex determination. Ecol Modell 2022. [DOI: 10.1016/j.ecolmodel.2022.110119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Bock SL, Smaga CR, McCoy JA, Parrott BB. Genome-wide DNA methylation patterns harbour signatures of hatchling sex and past incubation temperature in a species with environmental sex determination. Mol Ecol 2022; 31:5487-5505. [PMID: 35997618 PMCID: PMC9826120 DOI: 10.1111/mec.16670] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 08/15/2022] [Accepted: 08/18/2022] [Indexed: 01/11/2023]
Abstract
Conservation of thermally sensitive species depends on monitoring organismal and population-level responses to environmental change in real time. Epigenetic processes are increasingly recognized as key integrators of environmental conditions into developmentally plastic responses, and attendant epigenomic data sets hold potential for revealing cryptic phenotypes relevant to conservation efforts. Here, we demonstrate the utility of genome-wide DNA methylation (DNAm) patterns in the face of climate change for a group of especially vulnerable species, those with temperature-dependent sex determination (TSD). Due to their reliance on thermal cues during development to determine sexual fate, contemporary shifts in temperature are predicted to skew offspring sex ratios and ultimately destabilize sensitive populations. Using reduced-representation bisulphite sequencing, we profiled the DNA methylome in blood cells of hatchling American alligators (Alligator mississippiensis), a TSD species lacking reliable markers of sexual dimorphism in early life stages. We identified 120 sex-associated differentially methylated cytosines (DMCs; FDR < 0.1) in hatchlings incubated under a range of temperatures, as well as 707 unique temperature-associated DMCs. We further developed DNAm-based models capable of predicting hatchling sex with 100% accuracy (in 20 training samples and four test samples) and past incubation temperature with a mean absolute error of 1.2°C (in four test samples) based on the methylation status of 20 and 24 loci, respectively. Though largely independent of epigenomic patterning occurring in the embryonic gonad during TSD, DNAm patterns in blood cells may serve as nonlethal markers of hatchling sex and past incubation conditions in conservation applications. These findings also raise intriguing questions regarding tissue-specific epigenomic patterning in the context of developmental plasticity.
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Affiliation(s)
- Samantha L. Bock
- Eugene P. Odum School of EcologyUniversity of GeorgiaAthensGeorgiaUSA
- Savannah River Ecology LaboratoryAikenSouth CarolinaUSA
| | - Christopher R. Smaga
- Eugene P. Odum School of EcologyUniversity of GeorgiaAthensGeorgiaUSA
- Savannah River Ecology LaboratoryAikenSouth CarolinaUSA
| | - Jessica A. McCoy
- Department of BiologyCollege of CharlestonCharlestonSouth CarolinaUSA
| | - Benjamin B. Parrott
- Eugene P. Odum School of EcologyUniversity of GeorgiaAthensGeorgiaUSA
- Savannah River Ecology LaboratoryAikenSouth CarolinaUSA
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Hussan MT, Sakai A, Matsui H. Glutamatergic pathways in the brains of turtles: A comparative perspective among reptiles, birds, and mammals. Front Neuroanat 2022; 16:937504. [PMID: 36059432 PMCID: PMC9428285 DOI: 10.3389/fnana.2022.937504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Accepted: 07/22/2022] [Indexed: 11/13/2022] Open
Abstract
Glutamate acts as the main excitatory neurotransmitter in the brain and plays a vital role in physiological and pathological neuronal functions. In mammals, glutamate can cause detrimental excitotoxic effects under anoxic conditions. In contrast, Trachemys scripta, a freshwater turtle, is one of the most anoxia-tolerant animals, being able to survive up to months without oxygen. Therefore, turtles have been investigated to assess the molecular mechanisms of neuroprotective strategies used by them in anoxic conditions, such as maintaining low levels of glutamate, increasing adenosine and GABA, upregulating heat shock proteins, and downregulating KATP channels. These mechanisms of anoxia tolerance of the turtle brain may be applied to finding therapeutics for human glutamatergic neurological disorders such as brain injury or cerebral stroke due to ischemia. Despite the importance of glutamate as a neurotransmitter and of the turtle as an ideal research model, the glutamatergic circuits in the turtle brain remain less described whereas they have been well studied in mammalian and avian brains. In reptiles, particularly in the turtle brain, glutamatergic neurons have been identified by examining the expression of vesicular glutamate transporters (VGLUTs). In certain areas of the brain, some ionotropic glutamate receptors (GluRs) have been immunohistochemically studied, implying that there are glutamatergic target areas. Based on the expression patterns of these glutamate-related molecules and fiber connection data of the turtle brain that is available in the literature, many candidate glutamatergic circuits could be clarified, such as the olfactory circuit, hippocampal–septal pathway, corticostriatal pathway, visual pathway, auditory pathway, and granule cell–Purkinje cell pathway. This review summarizes the probable glutamatergic pathways and the distribution of glutamatergic neurons in the pallium of the turtle brain and compares them with those of avian and mammalian brains. The integrated knowledge of glutamatergic pathways serves as the fundamental basis for further functional studies in the turtle brain, which would provide insights on physiological and pathological mechanisms of glutamate regulation as well as neural circuits in different species.
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Affiliation(s)
- Mohammad Tufazzal Hussan
- Department of Neuroscience of Disease, Brain Research Institute, Niigata University, Niigata, Japan
- Department of Anatomy and Histology, Patuakhali Science and Technology University, Barishal, Bangladesh
- *Correspondence: Mohammad Tufazzal Hussan,
| | - Akiko Sakai
- Department of Neuroscience of Disease, Brain Research Institute, Niigata University, Niigata, Japan
| | - Hideaki Matsui
- Department of Neuroscience of Disease, Brain Research Institute, Niigata University, Niigata, Japan
- Hideaki Matsui,
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8
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Divers SJ, Barbosa A, Ellis LE, Innis C, Gibbons P. Endoscopic sexing in turtles and tortoises: 467 cases (2007-2017). Vet Rec 2022; 191:e1795. [PMID: 35789491 DOI: 10.1002/vetr.1795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 03/24/2022] [Accepted: 05/04/2022] [Indexed: 11/08/2022]
Abstract
BACKGROUND This multi-institutional retrospective study evaluated the feasibility and safety of endoscopic sex identification in 467 turtles and tortoises, representing 10 species. METHODS Medical records of turtles and tortoises that underwent endoscopic sex identification at the University of Georgia, New England Aquarium and Turtle Conservancy were reviewed for presurgical management, anaesthesia, endoscopic equipment and surgical techniques, endoscopic results and complications. RESULTS The majority of animals weighed less than 200 g, were fasted and anaesthetised using an injectable combination of ketamine, dexmedetomidine and morphine or hydromorphone, supplemented by local lidocaine at the prefemoral site. Anaesthetic reversal using atipamezole alone or in combination with naloxone was routine. For uncomplicated procedures, mean total anaesthesia, surgery and recovery times were 22, 4 and 18 minutes, respectively. All animals were placed in lateral recumbency for a prefemoral endoscopic approach to the coelom using a rigid telescope and sterile fluid infusion to visualise the gonads. Sex identification was definitive in 99.4% (n = 464) of the animals. Iatrogenic bladder perforation was the most common complication (n = 5), which necessitated extended anaesthesia and surgical time for repair. Only a single anaesthetic-related death was reported, which was associated with human error and drug overdose. CONCLUSIONS This is the first large-scale study to retrospectively evaluate endoscopic sex identification in multiple chelonian species. Results suggest that endoscopic sexing is a safe, accurate and practical means for sex identification in turtles and tortoises, and represents a valuable tool in their reproductive management.
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Affiliation(s)
- Stephen J Divers
- Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
| | - Amanda Barbosa
- Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA.,Island Veterinary Care, Melbourne Beach, Florida, USA
| | - Lauren E Ellis
- Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA.,Dockery, Mobley and Associates Animal Hospital, Albany, Georgia, USA
| | - Charles Innis
- Animal Health Department, New England Aquarium, Boston, Massachusetts, USA
| | - Paul Gibbons
- The Turtle Conservancy, Ojai, California, USA.,Avian & Exotic Veterinary Care, Portland, Oregon, USA
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LACTIC ACIDOSIS INDUCED BY MANUAL RESTRAINT FOR HEALTH EVALUATION AND COMPARISON OF TWO POINT-OF-CARE ANALYZERS IN HEALTHY LOGGERHEAD SEA TURTLES ( CARETTA CARETTA). J Zoo Wildl Med 2022; 52:1195-1204. [PMID: 34998289 DOI: 10.1638/2021-0029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/07/2021] [Indexed: 11/21/2022] Open
Abstract
Sea turtles are often restrained manually for brief periods during veterinary evaluation and care in rescue, rehabilitation, research, and aquarium settings. Blood gas values and lactate are routinely evaluated during triage of sea turtles, and lactate clearance is of prognostic significance in cold-stunned individuals. Although increases in blood lactate have been associated with muscle exertion, experimental forced submergence, trawl and pound net capture, and general anesthesia, changes in blood lactate associated with short periods of manual restraint have not been evaluated. Venous blood gas and lactate values were tested in 16 juvenile loggerhead sea turtles (Caretta caretta) before and after manual restraint for a 15-min routine veterinary examination. The agreement of blood lactate values between two point-of care analyzers (i-STAT and Lactate Plus) was also compared. Blood pH and bicarbonate (HCO3-) decreased significantly (P < 0.001), and partial pressure of carbon dioxide (pCO2) increased significantly (P < 0.0001) after 15 min. Lactate increased significantly between time points for both analyzers (P < 0.0001). Linear regression analysis showed excellent correlation for lactate measurements obtained on both analyzers (r = 0.998). The mean difference in lactate concentrations between the analyzers was statistically significant, indicating that the methods cannot be used interchangeably (P < 0.0001). Deming regression and Bland-Altman plots identified a slight negative proportional bias for lactate measurement by the Lactate Plus compared with the i-STAT. These results suggest that clinicians should evaluate blood gas values and lactate at the beginning of health evaluations and interpret serial lactate values in sea turtles with caution, because even short periods of manual restraint can induce lactic acidosis and considerably influence these values.
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Heydenrych MJ, Saunders BJ, Bunce M, Jarman SN. Epigenetic Measurement of Key Vertebrate Population Biology Parameters. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.617376] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The age, sex, and sexual maturity of individual animals are key parameters in assessing wild populations and informing conservation management strategies. These parameters represent the reproductive potential of a population and can indicate recovery rates or vulnerabilities. Natural populations of wild animals are difficult to study; logistically, economically, and due to the impacts of invasive biomonitoring. Genetic and epigenetic analyses offer a low impact, low cost, and information-rich alternative. As epigenetic mechanisms are intrinsically linked with both biological aging and reproductive processes, DNA methylation can be used as a suitable biomarker for population biology study. This review assesses published research utilizing DNA methylation analysis in relation to three key population parameters: age, sex, and sexual maturity. We review studies on wild vertebrates that investigate epigenetic age relationships, with successful age estimation assays designed for mammals, birds, and fish. For both determination of sex and identification of sexual maturity, very little has been explored regarding DNA methylation-based assays. Related research, however, confirms the links between DNA methylation and these processes. Future development of age estimation assays for underrepresented and key conservation taxa is suggested, as is the experimental development and design of DNA methylation-based assays for both sex and sexual maturity identification, further expanding the genomics toolkit for population biology studies.
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Tissue and Temperature-Specific RNA-Seq Analysis Reveals Genomic Versatility and Adaptive Potential in Wild Sea Turtle Hatchlings ( Caretta caretta). Animals (Basel) 2021; 11:ani11113013. [PMID: 34827746 PMCID: PMC8614379 DOI: 10.3390/ani11113013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 09/24/2021] [Accepted: 10/18/2021] [Indexed: 01/05/2023] Open
Abstract
Simple Summary Digital transcriptomics is rapidly emerging as a powerful new technology for modelling the environmental dynamics of the adaptive landscape in diverse lineages. This is particularly valuable in taxa such as turtles and tortoises (order Testudines) which contain a large fraction of endangered species at risk due to anthropogenic impacts on the environment, including pollution, overharvest, habitat degradation, and climate change. Sea turtles (family Cheloniidae) in particular invite a genomics-enabled approach to investigating their remarkable portfolio of adaptive evolution. Our de novo transcriptome assemblies and measurements of tissue- and temperature- specific global gene expression in the loggerhead sea turtle (Caretta caretta) reveal the genomic basis for potential resiliency in this endangered flagship species, and are crucial to future management and conservation strategies with attention to changing climates. We summarize the interactions among differentially expressed genes by producing network visualizations, and highlight the shared biological pathways related to development, migration, immunity, and longevity reported in the avian and reptilian literature. Our original results for loggerhead sea turtles provide a large, new comparative genomic resource for the investigation of genotype–phenotype relationships in amniotes. Abstract Background: Digital transcriptomics is rapidly emerging as a powerful new technology for modelling the environmental dynamics of the adaptive landscape in diverse lineages. This is particularly valuable in taxa such as turtles and tortoises (order Testudines) which contain a large fraction of endangered species at risk due to anthropogenic impacts on the environment, including pollution, overharvest, habitat degradation, and climate change. Sea turtles (family Cheloniidae) in particular invite a genomics-enabled approach to investigating their remarkable portfolio of adaptive evolution. The sex of the endangered loggerhead sea turtle (Caretta caretta) is subject to temperature-dependent sex determination (TSD), a mechanism by which exposure to temperatures during embryonic development irreversibly determines sex. Higher temperatures produce mainly female turtles and lower temperatures produce mainly male turtles. Incubation temperature can have long term effects on the immunity, migratory ability, and ultimately longevity of hatchlings. We perform RNA-seq differential expression analysis to investigate tissue- and temperature-specific gene expression within brain (n = 7) and gonadal (n = 4) tissue of male and female loggerhead hatchlings. Results: We assemble tissue- and temperature-specific transcriptomes and identify differentially expressed genes relevant to sexual development and life history traits of broad adaptive interest to turtles and other amniotic species. We summarize interactions among differentially expressed genes by producing network visualizations, and highlight shared biological pathways related to migration, immunity, and longevity reported in the avian and reptile literature. Conclusions: The measurement of tissue- and temperature-specific global gene expression of an endangered, flagship species such as the loggerhead sea turtle (Caretta caretta) reveals the genomic basis for potential resiliency and is crucial to future management and conservation strategies with attention to changing climates. Brain and gonadal tissue collected from experimentally reared loggerhead male and female hatchlings comprise an exceedingly rare dataset that permits the identification of genes enriched in functions related to sexual development, immunity, longevity, and migratory behavior and will serve as a large, new genomic resource for the investigation of genotype–phenotype relationships in amniotes.
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12
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Lockley EC, Eizaguirre C. Effects of global warming on species with temperature-dependent sex determination: Bridging the gap between empirical research and management. Evol Appl 2021; 14:2361-2377. [PMID: 34745331 PMCID: PMC8549623 DOI: 10.1111/eva.13226] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 03/05/2021] [Accepted: 03/11/2021] [Indexed: 12/31/2022] Open
Abstract
Global warming could threaten over 400 species with temperature-dependent sex determination (TSD) worldwide, including all species of sea turtle. During embryonic development, rising temperatures might lead to the overproduction of one sex and, in turn, could bias populations' sex ratios to an extent that threatens their persistence. If climate change predictions are correct, and biased sex ratios reduce population viability, species with TSD may go rapidly extinct unless adaptive mechanisms, whether behavioural, physiological or molecular, exist to buffer these temperature-driven effects. Here, we summarize the discovery of the TSD phenomenon and its still elusive evolutionary significance. We then review the molecular pathways underpinning TSD in model species, along with the hormonal mechanisms that interact with temperatures to determine an individual's sex. To illustrate evolutionary mechanisms that can affect sex determination, we focus on sea turtle biology, discussing both the adaptive potential of this threatened TSD taxon, and the risks associated with conservation mismanagement.
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Affiliation(s)
- Emma C. Lockley
- School of Biological and Chemical SciencesQueen Mary University LondonLondonUK
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13
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Hematological and Biochemical Reference Intervals for Euphrates Softshell Turtle (Rafetus euphraticus). IRANIAN JOURNAL OF SCIENCE AND TECHNOLOGY, TRANSACTIONS A: SCIENCE 2021. [DOI: 10.1007/s40995-021-01193-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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14
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Porter E, Booth DT, Limpus CJ, Staines MN, Smith CE. Influence of short-term temperature drops on sex-determination in sea turtles. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2021; 335:649-658. [PMID: 34313387 DOI: 10.1002/jez.2509] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2021] [Revised: 06/30/2021] [Accepted: 07/09/2021] [Indexed: 11/08/2022]
Abstract
All sea turtles exhibit temperature-dependent sex-determination, where warmer temperatures produce mostly females and cooler temperatures produce mostly males. As global temperatures continue to rise, sea turtle sex-ratios are expected to become increasingly female-biased, threatening the long-term viability of many populations. Nest temperatures are dependent on sand temperature, and heavy rainfall events reduce sand temperatures for a brief period. However, it is unknown whether these short-term temperature drops are large and long enough to produce male hatchlings. To discover if short-term temperature drops within the sex-determining period can lead to male hatchling production, we exposed green and loggerhead turtle eggs to short-term temperature drops conducted in constant temperature rooms. We dropped incubation temperature at four different times during the sex-determining period for a duration of either 3 or 7 days to mimic short-term drops in temperature caused by heavy rainfall in nature. Some male hatchlings were produced when exposed to temperature drops for as little as 3 days, but the majority of male production occurred when eggs were exposed to 7 days of lowered temperature. More male hatchlings were produced when the temperature drop occurred during the middle of the sex-determining period in green turtles, and the beginning and end of the sex-determining period in loggerhead turtles. Inter-clutch variation was evident in the proportion of male hatchlings produced, indicating that maternal and or genetic factors influence male hatchling production. Our findings have management implications for the long-term preservation of sea turtles on beaches that exhibit strongly female-biased hatchling sex-ratios.
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Affiliation(s)
- Ellen Porter
- School of Biological Sciences, Faculty of Science, The University of Queensland, Brisbane, Queensland, Australia
| | - David T Booth
- School of Biological Sciences, Faculty of Science, The University of Queensland, Brisbane, Queensland, Australia
| | - Colin J Limpus
- Queensland Government Department of Science and Environment, Aquatic Threatened Species Unit, Brisbane, Queensland, Australia
| | - Melissa N Staines
- School of Biological Sciences, Faculty of Science, The University of Queensland, Brisbane, Queensland, Australia
| | - Caitlin E Smith
- Brisbane Office, World Wildlife Fund Australia, Brisbane, Australia
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15
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Banerjee SM, Stoll JA, Allen CD, Lynch JM, Harris HS, Kenyon L, Connon RE, Sterling EJ, Naro-Maciel E, McFadden K, Lamont MM, Benge J, Fernandez NB, Seminoff JA, Benson SR, Lewison RL, Eguchi T, Summers TM, Hapdei JR, Rice MR, Martin S, Jones TT, Dutton PH, Balazs GH, Komoroske LM. Species and population specific gene expression in blood transcriptomes of marine turtles. BMC Genomics 2021; 22:346. [PMID: 33985425 PMCID: PMC8117300 DOI: 10.1186/s12864-021-07656-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 04/23/2021] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Transcriptomic data has demonstrated utility to advance the study of physiological diversity and organisms' responses to environmental stressors. However, a lack of genomic resources and challenges associated with collecting high-quality RNA can limit its application for many wild populations. Minimally invasive blood sampling combined with de novo transcriptomic approaches has great potential to alleviate these barriers. Here, we advance these goals for marine turtles by generating high quality de novo blood transcriptome assemblies to characterize functional diversity and compare global transcriptional profiles between tissues, species, and foraging aggregations. RESULTS We generated high quality blood transcriptome assemblies for hawksbill (Eretmochelys imbricata), loggerhead (Caretta caretta), green (Chelonia mydas), and leatherback (Dermochelys coriacea) turtles. The functional diversity in assembled blood transcriptomes was comparable to those from more traditionally sampled tissues. A total of 31.3% of orthogroups identified were present in all four species, representing a core set of conserved genes expressed in blood and shared across marine turtle species. We observed strong species-specific expression of these genes, as well as distinct transcriptomic profiles between green turtle foraging aggregations that inhabit areas of greater or lesser anthropogenic disturbance. CONCLUSIONS Obtaining global gene expression data through non-lethal, minimally invasive sampling can greatly expand the applications of RNA-sequencing in protected long-lived species such as marine turtles. The distinct differences in gene expression signatures between species and foraging aggregations provide insight into the functional genomics underlying the diversity in this ancient vertebrate lineage. The transcriptomic resources generated here can be used in further studies examining the evolutionary ecology and anthropogenic impacts on marine turtles.
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Affiliation(s)
- Shreya M Banerjee
- Department of Environmental Conservation, University of Massachusetts, Amherst, MA, USA
| | - Jamie Adkins Stoll
- Department of Environmental Conservation, University of Massachusetts, Amherst, MA, USA
| | - Camryn D Allen
- Marine Turtle Biology and Assessment Program, Protected Species Division, Pacific Islands Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Honolulu, HI, USA.,Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA, USA
| | - Jennifer M Lynch
- Chemical Sciences Division, National Institute of Standards and Technology, Hawai'i Pacific University, Waimanalo, HI, USA
| | - Heather S Harris
- Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA, USA
| | - Lauren Kenyon
- Department of Environmental Conservation, University of Massachusetts, Amherst, MA, USA
| | - Richard E Connon
- Department of Anatomy, Physiology and Cell Biology, University of California, Davis, Davis, CA, USA
| | - Eleanor J Sterling
- Center for Biodiversity and Conservation, American Museum of Natural History, New York, NY, USA
| | | | - Kathryn McFadden
- School of Agricultural, Forest, and Environmental Sciences, Clemson University, Clemson, SC, USA
| | - Margaret M Lamont
- United States Geological Survey, Wetland and Aquatic Research Center, Gainesville, FL, USA
| | - James Benge
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA, USA
| | - Nadia B Fernandez
- Department of Environmental Conservation, University of Massachusetts, Amherst, MA, USA
| | - Jeffrey A Seminoff
- Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA, USA
| | - Scott R Benson
- Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Moss Landing, CA, 95039, USA.,Moss Landing Marine Laboratories, San Jose State University, Moss Landing, CA, 95039, USA
| | - Rebecca L Lewison
- Department of Biology, San Diego State University, San Diego, CA, USA
| | - Tomoharu Eguchi
- Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA, USA
| | | | - Jessy R Hapdei
- Jessy's Tag Services, Saipan, Commonwealth of the Northern Mariana Islands, USA
| | - Marc R Rice
- Hawai'i Preparatory Academy, Kamuela, HI, USA
| | - Summer Martin
- Marine Turtle Biology and Assessment Program, Protected Species Division, Pacific Islands Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Honolulu, HI, USA
| | - T Todd Jones
- Marine Turtle Biology and Assessment Program, Protected Species Division, Pacific Islands Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Honolulu, HI, USA
| | - Peter H Dutton
- Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA, USA
| | | | - Lisa M Komoroske
- Department of Environmental Conservation, University of Massachusetts, Amherst, MA, USA. .,Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA, USA.
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16
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Patrício AR, Hawkes LA, Monsinjon JR, Godley BJ, Fuentes MMPB. Climate change and marine turtles: recent advances and future directions. ENDANGER SPECIES RES 2021. [DOI: 10.3354/esr01110] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Climate change is a threat to marine turtles that is expected to affect all of their life stages. To guide future research, we conducted a review of the most recent literature on this topic, highlighting knowledge gains and research gaps since a similar previous review in 2009. Most research has been focussed on the terrestrial life history phase, where expected impacts will range from habitat loss and decreased reproductive success to feminization of populations, but changes in reproductive periodicity, shifts in latitudinal ranges, and changes in foraging success are all expected in the marine life history phase. Models have been proposed to improve estimates of primary sex ratios, while technological advances promise a better understanding of how climate can influence different life stages and habitats. We suggest a number of research priorities for an improved understanding of how climate change may impact marine turtles, including: improved estimates of primary sex ratios, assessments of the implications of female-biased sex ratios and reduced male production, assessments of the variability in upper thermal limits of clutches, models of beach sediment movement under sea level rise, and assessments of impacts on foraging grounds. Lastly, we suggest that it is not yet possible to recommend manipulating aspects of turtle nesting ecology, as the evidence base with which to understand the results of such interventions is not robust enough, but that strategies for mitigation of stressors should be helpful, providing they consider the synergistic effects of climate change and other anthropogenic-induced threats to marine turtles, and focus on increasing resilience.
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Affiliation(s)
- AR Patrício
- MARE - Marine and Environmental Sciences Centre, ISPA - Instituto Universitário, 1149-041 Lisbon, Portugal
- Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn TR10 9FE, UK
| | - LA Hawkes
- Hatherley Laboratories, College of Life and Environmental Sciences, University of Exeter, Streatham Campus, Exeter EX4 4PS, UK
| | - JR Monsinjon
- Department of Zoology and Entomology, Rhodes University, Grahamstown 6139, South Africa
| | - BJ Godley
- Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn TR10 9FE, UK
| | - MMPB Fuentes
- Marine Turtle Research, Ecology and Conservation Group, Department of Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, FL 32306, USA
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17
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Maurer AS, Seminoff JA, Layman CA, Stapleton SP, Godfrey MH, Reiskind MOB. Population Viability of Sea Turtles in the Context of Global Warming. Bioscience 2021. [DOI: 10.1093/biosci/biab028] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Abstract
Sea turtles present a model for the potential impacts of climate change on imperiled species, with projected warming generating concern about their persistence. Various sea turtle life-history traits are affected by temperature; most strikingly, warmer egg incubation temperatures cause female-biased sex ratios and higher embryo mortality. Predictions of sea turtle resilience to climate change are often focused on how resulting male limitation or reduced offspring production may affect populations. In the present article, by reviewing research on sea turtles, we provide an overview of how temperature impacts on incubating eggs may cascade through life history to ultimately affect population viability. We explore how sex-specific patterns in survival and breeding periodicity determine the differences among offspring, adult, and operational sex ratios. We then discuss the implications of skewed sex ratios for male-limited reproduction, consider the negative correlation between sex ratio skew and genetic diversity, and examine consequences for adaptive potential. Our synthesis underscores the importance of considering the effects of climate throughout the life history of any species. Lethal effects (e.g., embryo mortality) are relatively direct impacts, but sublethal effects at immature life-history stages may not alter population growth rates until cohorts reach reproductive maturity. This leaves a lag during which some species transition through several stages subject to distinct biological circumstances and climate impacts. These perspectives will help managers conceptualize the drivers of emergent population dynamics and identify existing knowledge gaps under different scenarios of predicted environmental change.
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Affiliation(s)
- Andrew S Maurer
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, in the United States; he is also a research associate with the Jumby Bay Hawksbill Project in Antigua, West Indies
| | - Jeffrey A Seminoff
- Marine Turtle Ecology and Assessment Program, National Oceanic and Atmospheric Administration's Southwest Fisheries Science Center, La Jolla, California, United States
| | - Craig A Layman
- Center for Energy, Environment, and Sustainability, Wake Forest University, in Winston-Salem, North Carolina, in the United States
| | - Seth P Stapleton
- Conservation and animal health sciences, Minnesota Zoo, Apple Valley, Minnesota; he is also an adjunct faculty member in the Department of Fisheries, Wildlife, and Conservation Biology, University of Minnesota, in Minneapolis, Minnesota, in the United States
| | - Matthew H Godfrey
- North Carolina Wildlife Resources Commission, Raleigh, North Carolina, United States
| | - Martha O Burford Reiskind
- Martha Burford Reiskind is an assistant professor in the Department of Biological Sciences and the director of the Genetics and Genomics Scholars program, North Carolina State University, Raleigh, North Carolina, United States
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18
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Chatting M, Hamza S, Al-Khayat J, Smyth D, Husrevoglu S, Marshall CD. Feminization of hawksbill turtle hatchlings in the twenty-first century at an important regional nesting aggregation. ENDANGER SPECIES RES 2021. [DOI: 10.3354/esr01104] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Projected climate change is forecasted to have significant effects on biological systems worldwide. Marine turtles in particular may be vulnerable, as the sex of their offspring is determined by their incubating temperature, termed temperature-dependent sex determination. This study aimed to estimate historical, and forecast future, primary sex ratios of hawksbill turtle Eretmochelys imbricata hatchlings at an important nesting ground in northeastern Qatar. Incubation temperatures from the Arabian/Persian Gulf were measured over 2 nesting seasons. Climate data from same period were regressed with nest temperatures to estimate incubation temperatures and hatchling sex ratios for the site from 1993 to 2100. Future hatchling sex ratios were estimated for 2 climate forecasts, one mid-range (SSP245) and one extreme (SSP585). Historical climate data showed female-biased sex ratios of 73.2 ± 12.1% from 1993 to 2017. Female biases from 2018 to 2100 averaged 85.7% ± 6.7% under the mid-range scenario and 87.9% ± 5.4% under the high-range scenario. In addition, predicted female hatchling production was >90% from 2054 and 2052 for SSP245 and SSP585, respectively. These results show that hawksbill primary sex ratios in Qatar are at risk of significant feminization by the year 2100 and that hawksbill turtle incubation temperatures in an extreme, understudied environment are already comparable to those predicted in tropical rookeries during the latter half of the 21st century. These results can help conservationists predict primary sex ratios for hawksbill turtles in the region in the face of 21st-century climate change.
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Affiliation(s)
- M Chatting
- Environmental Science Center, Qatar University, Doha 2713, Qatar
| | - S Hamza
- Environmental Science Center, Qatar University, Doha 2713, Qatar
| | - J Al-Khayat
- Environmental Science Center, Qatar University, Doha 2713, Qatar
| | - D Smyth
- School of Ocean Sciences, Bangor University, Menai Bridge, Anglesey LL59 5EY, UK
| | - S Husrevoglu
- Institute of Marine Sciences, Middle East Technical University, Erdemli, Mersin 33731, Turkey
| | - CD Marshall
- Department of Marine Biology, Department of Wildlife and Fisheries Sciences, Gulf Center for Sea Turtle Research, Texas A&M University, Galveston, Texas 77553, USA
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19
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Carter AL, Janzen FJ. Predicting the effects of climate change on incubation in reptiles: methodological advances and new directions. J Exp Biol 2021; 224:224/Suppl_1/jeb236018. [PMID: 33627463 DOI: 10.1242/jeb.236018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The unprecedented advancement of global climate change is affecting thermal conditions across spatial and temporal scales. Reptiles with temperature-dependent sex determination (TSD) are uniquely vulnerable to even fine-scale variation in incubation conditions and are a model system for investigating the impacts of shifting temperatures on key physiological and life-history traits. The ways in which current and predicted future climatic conditions translate from macro- to ultra-fine scale temperature traces in subterranean nests is insufficiently understood. Reliably predicting the ways in which fine-scale, daily and seasonally fluctuating nest temperatures influence embryonic development and offspring phenotypes is a goal that remains constrained by many of the same logistical challenges that have persisted throughout more than four decades of research on TSD. However, recent advances in microclimate and developmental modeling should allow us to move farther away from relatively coarse metrics with limited predictive capacity and towards a fully mechanistic model of TSD that can predict incubation conditions and phenotypic outcomes for a variety of reptile species across space and time and for any climate scenario.
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Affiliation(s)
- A L Carter
- Michigan State University, Kellogg Biological Station, 3700 E Gull Lake Drive, Hickory Corners, MI 49060, USA.,Iowa State University, Department of Ecology, Evolution and Organismal Biology, 2200 Osborn Drive, 251 Bessey Hall, Ames, IA 50011, USA
| | - Fredric J Janzen
- Michigan State University, Kellogg Biological Station, 3700 E Gull Lake Drive, Hickory Corners, MI 49060, USA .,Iowa State University, Department of Ecology, Evolution and Organismal Biology, 2200 Osborn Drive, 251 Bessey Hall, Ames, IA 50011, USA
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20
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FIELD ANESTHESIA AND GONADAL MORPHOLOGY OF IMMATURE WESTERN SANTA CRUZ TORTOISES ( CHELONOIDIS PORTERI). J Zoo Wildl Med 2021; 51:848-855. [PMID: 33480565 DOI: 10.1638/2019-0240] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/08/2020] [Indexed: 11/21/2022] Open
Abstract
Evaluation of sex ratios is a critical component of chelonian captive breeding programs and may become increasingly useful to assess the demographics of free-living populations. In many reptile species, the sex of immature animals cannot be determined based on external features. Endoscopic sex identification is an accurate and safe method to identify the sex of immature individuals of some chelonian species. A number of studies describe this technique in controlled, hospital settings and report significant interspecies variations in gonad morphology; however, there are few reports describing this technique in field conditions. In the current study, the gonadal morphology of 40 immature Western Santa Cruz tortoises (Chelonoidis porteri) on Santa Cruz Island in Galapagos, Ecuador, was assessed. A previously described endoscopic protocol was used to perform sex identification under field conditions. Tortoises were anesthetized using an intramuscular injection of ketamine (10 mg/kg) and medetomidine (0.1 mg/kg), which provided an adequate plane of anesthesia. The medetomidine was reversed with atipamezole (0.5 mg/kg). Field conditions presented challenges such as limited control over lighting, suboptimal patient positioning, and restricted power supply for endoscopy equipment. The immature testicle in Western Santa Cruz tortoises was oval, reddish pink, and tightly adhered to the coelomic membrane ventral to the kidney. The surface of the gonads resembled other species with the notable exception that the ovaries lacked a significant number of primordial follicles. These gonadal characteristics were consistent, with only one individual identified as undetermined sex of the 40 samples. This field-based endoscopic gonadal evaluation was a safe and sensitive technique for determining the sex of free-living immature Western Santa Cruz Galapagos tortoises.
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21
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Laloë J, Tedeschi JN, Booth DT, Bell I, Dunstan A, Reina RD, Hays GC. Extreme rainfall events and cooling of sea turtle clutches: Implications in the face of climate warming. Ecol Evol 2021; 11:560-565. [PMID: 33437451 PMCID: PMC7790631 DOI: 10.1002/ece3.7076] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 10/12/2020] [Accepted: 10/29/2020] [Indexed: 11/08/2022] Open
Abstract
Understanding how climate change impacts species and ecosystems is integral to conservation. When studying impacts of climate change, warming temperatures are a research focus, with much less attention given to extreme weather events and their impacts. Here, we show how localized, extreme rainfall events can have a major impact on a species that is endangered in many parts of its range. We report incubation temperatures from the world's largest green sea turtle rookery, during a breeding season when two extreme rainfall events occurred. Rainfall caused nest temperatures to drop suddenly and the maximum drop in temperature for each rain-induced cooling averaged 3.6°C (n = 79 nests, min = 1.0°C, max = 7.4°C). Since green sea turtles have temperature-dependent sex determination, with low incubation temperatures producing males, such major rainfall events may have a masculinization effect on primary sex ratios. Therefore, in some cases, extreme rainfall events may provide a "get-out-of-jail-free card" to avoid complete feminization of turtle populations as climate warming continues.
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Affiliation(s)
| | - Jamie N. Tedeschi
- School of Biological SciencesThe University of QueenslandBrisbaneQldAustralia
| | - David T. Booth
- School of Biological SciencesThe University of QueenslandBrisbaneQldAustralia
| | - Ian Bell
- Queensland Department of Environment and ScienceTownsvilleQldAustralia
| | - Andy Dunstan
- Queensland Department of Environment and ScienceQueensland Parks and Wildlife Service and PartnershipsBrisbaneQldAustralia
| | - Richard D. Reina
- School of Biological SciencesMonash UniversityClaytonVic.Australia
| | - Graeme C. Hays
- School of Life and Environmental SciencesDeakin UniversityGeelongVic.Australia
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22
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Santidrián Tomillo P, Spotila JR. Temperature-Dependent Sex Determination in Sea Turtles in the Context of Climate Change: Uncovering the Adaptive Significance. Bioessays 2020; 42:e2000146. [PMID: 32896903 DOI: 10.1002/bies.202000146] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 07/22/2020] [Indexed: 11/11/2022]
Abstract
The adaptive significance of temperature-dependent sex determination (TSD) in reptiles remains unknown decades after TSD was first identified in this group. Concurrently, there is growing concern about the effect that rising temperatures may have on species with TSD, potentially producing extremely biased sex ratios or offspring of only one sex. The current state-of the-art in TSD research on sea turtles is reviewed here and, against current paradigm, it is proposed that TSD provides an advantage under warming climates. By means of coadaptation between early survival and sex ratios, sea turtles are able to maintain populations. When offspring survival declines at high temperatures, the sex that increases future fecundity (females) is produced, increasing resilience to climate warming. TSD could have helped reptiles to survive mass extinctions in the past via this model. Flaws in research on sex determination in sea turtles are also identified and it is suggested that the development of new techniques will revolutionize the field.
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Affiliation(s)
| | - James R Spotila
- Department of Biodiversity, Earth and Environmental Science, Drexel University, Philadelphia, Pennsylvania, 19104, USA
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23
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Tanabe LK, Ellis J, Elsadek I, Berumen ML. Potential feminization of Red Sea turtle hatchlings as indicated by in situ sand temperature profiles. CONSERVATION SCIENCE AND PRACTICE 2020. [DOI: 10.1111/csp2.266] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Affiliation(s)
- Lyndsey K. Tanabe
- Red Sea Research Center, Division of Biological and Environmental Science and Engineering King Abdullah University of Science and Technology Thuwal Saudi Arabia
| | - Joanne Ellis
- Red Sea Research Center, Division of Biological and Environmental Science and Engineering King Abdullah University of Science and Technology Thuwal Saudi Arabia
- School of Biological Sciences Waikato University Tauranga New Zealand
| | - Islam Elsadek
- Egyptian Environmental Affairs Agency, Ministry of Environment Hurghada Egypt
| | - Michael L. Berumen
- Red Sea Research Center, Division of Biological and Environmental Science and Engineering King Abdullah University of Science and Technology Thuwal Saudi Arabia
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24
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Wyneken J, Salmon M. Linking Ecology, Morphology, and Behavior to Conservation: Lessons Learned from Studies of Sea Turtles. Integr Comp Biol 2020; 60:440-455. [PMID: 32617553 DOI: 10.1093/icb/icaa044] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Here we describe examples of studies that have contributed both to a basic understanding of the biology of imperiled marine turtles, and to their management and conservation. Key elements include, first and foremost, correctly identifying species that differ strikingly in their morphology at different life stages because with growth, they change size by several orders of magnitude and have accompanying shape changes. We also review comprehensive field studies documenting the need for management actions to correct abnormal shifts in sex ratios caused by climate change. We highlight the need to describe those perturbations in terms that are clear to regulators and personnel responsible for management and conservation policies. Finally, we review several basic studies that enhance our understanding of how selection has shaped morphological, functional, and performance attributes, and describe how that knowledge can be applied to the tasks required for enhancing species recovery.
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Affiliation(s)
- Jeanette Wyneken
- Department of Biological Sciences, Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431-0991, USA
| | - Michael Salmon
- Department of Biological Sciences, Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431-0991, USA
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