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Williamson SA, Hoover AL, Evans RG, Shillinger GL, Bailey H, Bruno RS, Bandimere A, Reina RD. Effects of postovipositional hypoxia and hyperoxia on leatherback turtle reproductive success and hatchling performance. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART A, ECOLOGICAL AND INTEGRATIVE PHYSIOLOGY 2023; 339:939-950. [PMID: 37545193 DOI: 10.1002/jez.2743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 07/27/2023] [Accepted: 07/28/2023] [Indexed: 08/08/2023]
Abstract
Leatherback egg clutches typically experience lower hatching success (~50%) than those of other sea turtle species (>70%). The majority of embryonic death (>50%) occurs at early stages of development, possibly because embryos fail to break preovipositional embryonic arrest after oviposition. The embryonic arrest is maintained by hypoxia in the oviduct and following oviposition increased availability of oxygen is the trigger that breaks arrest in all turtle species studied to date. We conducted an ex situ incubator experiment and an in situ hatchery experiment to examine the influence of oxygen availability on hatching success and hatchling traits in leatherbacks. After oviposition, eggs (n = 1005) were incubated in either normoxia (21% O2 ), hyperoxia (32%-42% O2 ) for 5 days, or hypoxia (1% O2 ) for 3 or 5 days. As with other turtles, hypoxic incubation maintained embryos in arrest, equivalent to the time spent in hypoxia. However, extending arrest for 5 days resulted in greater early-stage death and a significant decrease in hatching success (4% 5-day hypoxia vs. 72% normoxia). Eggs placed in incubators had greater hatching success than those placed into hatchery nests (67% vs. 47%, respectively). We found no impact of hyperoxia on the stage of embryonic death, hatching success, hatchling phenotype, exercise performance, or early dispersal. Our findings indicate that delayed nesting and the subsequent extension of embryonic arrest may negatively impact embryonic development and therefore the reproductive success of leatherbacks. They also indicate that incubation under hyperoxic conditions is unlikely to be a useful method to improve hatching success in this species.
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Affiliation(s)
- Sean A Williamson
- School of Biological Sciences, Monash University, Clayton, Victoria, Australia
| | - Aimee L Hoover
- Upwell, Monterey, California, USA
- Chesapeake Biological Laboratory, University of Maryland Centre for Environmental Science, Solomons, Maryland, USA
| | - Roger G Evans
- Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Clayton, Victoria, Australia
- Preclinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria, Australia
| | | | - Helen Bailey
- Chesapeake Biological Laboratory, University of Maryland Centre for Environmental Science, Solomons, Maryland, USA
| | - Renato Saragoça Bruno
- Turtle Love, Barra de Parismina, Limon, Costa Rica
- Pacuare Reserve, Ecology Project International, Limon, Costa Rica
| | | | - Richard D Reina
- School of Biological Sciences, Monash University, Clayton, Victoria, Australia
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Adams DM, Williamson SA, Evans RG, Reina RD. Increasing hypoxia progressively slows early embryonic development in an oviparous reptile, the green turtle, Chelonia mydas. ROYAL SOCIETY OPEN SCIENCE 2022; 9:220709. [PMID: 36061518 PMCID: PMC9428527 DOI: 10.1098/rsos.220709] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 08/12/2022] [Indexed: 06/15/2023]
Abstract
Green turtle (Chelonia mydas) embryos are in an arrested state of development when the eggs are laid, but in the presence of oxygen, arrest is broken and development resumes within 12-16 h. However, the precise oxygen level at which embryos break arrest and continue development is not known. To better understand the impact of oxygen concentration on breaking of arrest and early embryonic development, we incubated freshly laid eggs of the green sea turtle for three days at each of six different oxygen concentrations (less than or equal to 1%, 3%, 5%, 7%, 9% and 21%) and monitored the appearance and growth of white spots on the shell, indicative of embryonic development. As reported previously, white spots did not develop on eggs incubated in anoxia (less than or equal to 1% oxygen). For all other treatments, mean time to white spot detection and white spot growth rate varied inversely with oxygen concentration. In nearly all cases the difference between eggs at different oxygen levels was statistically significant (p ≤ 0.05). This suggests that sea turtle embryonic development may respond to oxygen in a dose-dependent manner. Our results indicate that the development of green turtle embryos may be slowed if they are exposed to the most hypoxic conditions reported in mature natural nests.
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Affiliation(s)
| | | | - Roger G. Evans
- Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Clayton, Victoria 3800, Australia
- Pre-clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria 3010, Australia
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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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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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Booth DT, Dunstan A, Robertson K, Tedeschi J. Egg viability of green turtles nesting on Raine Island, the world’s largest nesting aggregation of green turtles. AUST J ZOOL 2021. [DOI: 10.1071/zo21024] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Egg inviability at oviposition is a possible explanation for the high rate of early-stage embryo death of eggs laid by green turtles at Raine Island, the largest green turtle nesting aggregation in the world. We tested this possibility by assessing egg viability of freshly laid eggs. We found that green turtle eggs laid at Raine Island have high viability at their time of laying, and that there was no relationship between egg viability and early-stage embryo death or hatching success within a clutch. Hence, the inviable egg at oviposition hypothesis cannot explain the high death rate of early-stage embryos that is characteristic of green turtle clutches laid at Raine Island.
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