1
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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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2
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Gárriz A, Williamson SA, Shah AD, Evans RG, Deveson Lucas DS, Powell DR, Walton SL, Marques FZ, Reina RD. Transcriptomic analysis of pre-ovipositional embryonic arrest in a non-squamate reptile (Chelonia mydas). Mol Ecol 2022; 31:4319-4331. [PMID: 35762848 PMCID: PMC9540450 DOI: 10.1111/mec.16583] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 06/20/2022] [Accepted: 06/22/2022] [Indexed: 11/29/2022]
Abstract
After gastrulation, oviductal hypoxia maintains turtle embryos in an arrested state prior to oviposition. Subsequent exposure to atmospheric oxygen upon oviposition initiates recommencement of embryonic development. Arrest can be artificially extended for several days after oviposition by incubation of the egg under hypoxic conditions, with development recommencing in an apparently normal fashion after subsequent exposure to normoxia. To examine the transcriptomic events associated with embryonic arrest in green sea turtles (Chelonia mydas), RNA‐sequencing analysis was performed on embryos from freshly laid eggs and eggs incubated in either normoxia (oxygen tension ~159 mmHg) or hypoxia (<8 mmHg) for 36 h after oviposition (n = 5 per group). The patterns of gene expression differed markedly among the three experimental groups. Normal embryonic development in normoxia was associated with upregulation of genes involved in DNA replication, the cell cycle, and mitosis, but these genes were commonly downregulated after incubation in hypoxia. Many target genes of hypoxia inducible factors, including the gene encoding insulin‐like growth factor binding protein 1 (igfbp1), were downregulated by normoxic incubation but upregulated by incubation in hypoxia. Notably, some of the transcriptomic effects of hypoxia in green turtle embryos resembled those reported to be associated with hypoxia‐induced embryonic arrest in diverse taxa, including the nematode Caenorhabditis elegans and zebrafish (Danio rerio). Hypoxia‐induced preovipositional embryonic arrest appears to be a unique adaptation of turtles. However, our findings accord with the proposition that the mechanisms underlying hypoxia‐induced embryonic arrest per se are highly conserved across diverse taxa.
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Affiliation(s)
- Angela Gárriz
- School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia
| | - Sean A Williamson
- School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia
| | - Anup D Shah
- Monash Bioinformatics Platform, Biomedicine Discovery Institute, Monash University, Clayton, Victoria 3800, Australia.,Monash Proteomics & Metabolomics Facility, Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton, Victoria 3800, Australia
| | - 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, Melbourne, Victoria, Australia
| | - Deanna S Deveson Lucas
- Monash Bioinformatics Platform, Biomedicine Discovery Institute, Monash University, Clayton, Victoria 3800, Australia
| | - David R Powell
- Monash Bioinformatics Platform, Biomedicine Discovery Institute, Monash University, Clayton, Victoria 3800, Australia
| | - Sarah L Walton
- Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Clayton, Victoria 3800, Australia
| | - Francine Z Marques
- School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia
| | - Richard D Reina
- School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia
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Gatto CR, Reina RD. A review of the effects of incubation conditions on hatchling phenotypes in non-squamate reptiles. J Comp Physiol B 2022; 192:207-233. [PMID: 35142902 PMCID: PMC8894305 DOI: 10.1007/s00360-021-01415-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 09/15/2021] [Accepted: 10/03/2021] [Indexed: 11/28/2022]
Abstract
Developing embryos of oviparous reptiles show substantial plasticity in their responses to environmental conditions during incubation, which can include altered sex ratios, morphology, locomotor performance and hatching success. While recent research and reviews have focused on temperature during incubation, emerging evidence suggests other environmental variables are also important in determining hatchling phenotypes. Understanding how the external environment influences development is important for species management and requires identifying how environmental variables exert their effects individually, and how they interact to affect developing embryos. To address this knowledge gap, we review the literature on phenotypic responses in oviparous non-squamate (i.e., turtles, crocodilians and tuataras) reptile hatchlings to temperature, moisture, oxygen concentration and salinity. We examine how these variables influence one another and consider how changes in each variable alters incubation conditions and thus, hatchling phenotypes. We explore how incubation conditions drive variation in hatchling phenotypes and influence adult populations. Finally, we highlight knowledge gaps and suggest future research directions.
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Affiliation(s)
- Christopher R Gatto
- School of Biological Sciences, Monash University, 25 Rainforest Walk, Clayton, VIC, 3800, Australia.
| | - Richard D Reina
- School of Biological Sciences, Monash University, 25 Rainforest Walk, Clayton, VIC, 3800, Australia
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4
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Gomes LG, Stocco MB, Sousa NPD, Martini AC, Morgado TO, Spiller PR, Moreira LFB, de Souza RL. Influence of incubation temperature and embryonic motility on the growth of members of Caiman yacare (Daudin, 1802). BRAZ J BIOL 2021; 84:e252845. [PMID: 34932637 DOI: 10.1590/1519-6984.252845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 10/20/2021] [Indexed: 11/21/2022] Open
Abstract
This study aimed to evaluate whether skeletal development of the Pantanal Caiman (Caiman yacare) is similarly influenced by temperature variation and controlled increases in embryo motility. All eggs were incubated at 90% humidity and 29 °C for the first 45 days. Thereafter, the incubation temperature was either maintained at 29 °C and embryos were treated with 4-aminopyridine (4-AP) on days 46, 47, 48, and 49 (Group I, 29 °C 4-AP, n = 15); maintained at 29 °C (n = 14; Group II); or at 33 °C (n = 14, Group III). Embryonic movement was measured using an Egg Buddy® digital monitor on days 30, 35, 42, 49, 56, and 60, at which point embryos were euthanized and samples were collected for analysis. No differences were observed between groups with varying incubation temperatures. In contrast, embryonic motility was greater in embryos treated with 4-AP (P < 0.001) on day 49, and this was associated with higher proportions of snout-vent and hand lengths. This study demonstrates for the first time that pharmacologically induced increases in embryo motility result in phenotypic changes to the proportion of elements during prenatal ontogeny, thereby effectively altering the adaptation of the species to specific environments.
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Affiliation(s)
- L G Gomes
- Universidade Federal de Mato Grosso - UFMT, Faculdade de Medicina Veterinária - FAVET, Cuiabá, MT, Brasil
| | - M B Stocco
- Universidade Federal de Mato Grosso - UFMT, Faculdade de Medicina Veterinária - FAVET, Cuiabá, MT, Brasil
| | - N P de Sousa
- Universidade Federal de Mato Grosso - UFMT, Faculdade de Medicina Veterinária - FAVET, Cuiabá, MT, Brasil
| | - A C Martini
- Universidade de Mineiros - UNIFIMES, Departamento de Ciências Agrárias, Mineiros, GO, Brasil
| | - T O Morgado
- Universidade Federal de Mato Grosso - UFMT, Faculdade de Medicina Veterinária - FAVET, Cuiabá, MT, Brasil
| | - P R Spiller
- Universidade de Cuiabá - UNIC, Programa de Pós-Graduação em Biociência Animal, Cuiabá, MT, Brasil
| | - L F B Moreira
- Universidade Federal de Mato Grosso - UFMT, Instituto Nacional de Pesquisas do Pantanal - INPP, Museu Paraense Emílio Goeldi - MPEG, Cuiabá, MT, Brasil
| | - R L de Souza
- Universidade Federal de Mato Grosso - UFMT, Faculdade de Medicina Veterinária - FAVET, Cuiabá, MT, Brasil
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Gárriz A, Williamson SA, Evans RG, Reina RD. A method for the collection of early-stage sea turtle embryos. ENDANGER SPECIES RES 2020. [DOI: 10.3354/esr01039] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Early-stage turtle embryos, immediately after oviposition, are very small (<5 mm diameter), hindering research on the initial period of embryonic development. For example, assessing whether turtle eggs had been fertilized and contained a viable embryo at oviposition, especially under field conditions, is complicated by the microscopic size of embryos that may have died at an early stage of development. Further, little is known about the molecular pathways that promote and regulate early developmental processes in turtles, such as pre-ovipositional embryonic arrest. To enable further investigation of the processes critical to early embryonic development in turtle species, a reliable method is required for extraction of early-stage embryos from the egg. Therefore, our aim was to develop a novel and reproducible method for extracting early-stage sea turtle embryos. Herein, we describe the technique for extracting Chelonia mydas embryos before and after white spot formation. Once the embryos were collected, the total RNA of 10 embryos was extracted to validate the method. The total RNA concentration was above 5 ng µl-1 and the RNA integrity number varied between 7.0 and 10.0, which is considered acceptable for further RNA-sequencing analyses. This extraction technique could be employed when investigating fertilization rates of turtle nests and for further investigation of the molecular biology of embryonic development in turtles. Furthermore, the technique should be adaptable to other turtle species or any oviparous species with similar eggs.
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Affiliation(s)
- A Gárriz
- School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia
| | - SA Williamson
- School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia
| | - RG Evans
- Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Clayton, Victoria 3800, Australia
| | - RD Reina
- School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia
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Yang TR, Engler T, Lallensack JN, Samathi A, Makowska M, Schillinger B. Hatching Asynchrony in Oviraptorid Dinosaurs Sheds Light on Their Unique Nesting Biology. Integr Org Biol 2019; 1:obz030. [PMID: 33791544 PMCID: PMC7671163 DOI: 10.1093/iob/obz030] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Dinosaur nesting biology has been an intriguing research topic, though dinosaur behaviors were relatively less illuminated because of the constraints of the fossil record. For instance, hatching asynchrony, where eggs in a single clutch hatch at different times, is unique to modern neoavian birds but was also suggested to be present in oviraptorid dinosaurs based on a possible partial clutch of four embryo-containing eggs from Mongolia. Unfortunately, unequivocal evidence for the origination of these eggs from a single clutch is lacking. Here we report a new, better preserved partial oviraptorid clutch with three embryo-containing eggs—a single egg (Egg I) and a pair (Egg II/III)—from the Late Cretaceous Nanxiong Group of Jiangxi Province, China. Geopetal features indicate that the pair of eggs was laid prior to the single egg. Neutron tomographic images in combination with osteological features indicate that the embryo of the single egg is less developed than those of the paired eggs. Eggshell histology suggests that the embryo-induced erosion in the paired eggs is markedly more pronounced than in the single egg, providing a new line of evidence for hatching asynchrony. The inferred hatching asynchrony in combination with previously surmised thermoregulatory incubation and communal nesting behaviors very likely suggests that oviraptorid dinosaurs presented a unique reproductive biology lacking modern analogs, which is contrary to the predominant view that their reproductive biology was intermediate between that of modern crocodiles and birds.
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Affiliation(s)
- T-R Yang
- Section of Paleontology, Institute of Geosciences, Rheinische Friedrich-Wilhelms-Universität Bonn, Nussallee 8, 53115 Bonn, Germany.,Division of Geology, National Museum of Natural Science, Guancian Road 1, 40453 Taichung, Taiwan
| | - T Engler
- Section of Paleontology, Institute of Geosciences, Rheinische Friedrich-Wilhelms-Universität Bonn, Nussallee 8, 53115 Bonn, Germany
| | - J N Lallensack
- Section of Paleontology, Institute of Geosciences, Rheinische Friedrich-Wilhelms-Universität Bonn, Nussallee 8, 53115 Bonn, Germany
| | - A Samathi
- Section of Paleontology, Institute of Geosciences, Rheinische Friedrich-Wilhelms-Universität Bonn, Nussallee 8, 53115 Bonn, Germany.,Biodiversity and Conservation Research Unit. Walai Rukhavej Botanical Research Institute, Mahasarakham University, 44150 Maha Sarakham, Thailand
| | - M Makowska
- Photons for Engineering and Manufacturing Group, Paul Scherrer Institute, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - B Schillinger
- Heinz Maier-Leibnitz Zentrum (MLZ), Lichtenbergstraße 1, 85748 Garching, Germany
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7
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Manipulation of Developmental Function in Turtles with Notes on Alligators. Methods Mol Biol 2019. [PMID: 30737695 DOI: 10.1007/978-1-4939-9009-2_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Reptiles have great taxonomic diversity that is reflected in their morphology, ecology, physiology, modes of reproduction, and development. Interest in comparative and evolutionary developmental biology makes protocols for the study of reptile embryos invaluable resources. The relatively large size, seasonal breeding, and long gestation times of turtles epitomize the challenges faced by the developmental biologist. We describe protocols for the preparation of turtle embryos for ex ovo culture, electroporation, in situ hybridization, and microcomputed tomography. Because these protocols have been adapted and optimized from methods used for frog, chick, and mouse embryos, it is likely that they could be used for other reptilian species. Notes are included for alligator embryos where appropriate.
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Williamson SA, Evans RG, Manolis SC, Webb GJ, Reina RD. Ecological and evolutionary significance of a lack of capacity for extended developmental arrest in crocodilian eggs. ROYAL SOCIETY OPEN SCIENCE 2017; 4:171439. [PMID: 29308266 PMCID: PMC5750033 DOI: 10.1098/rsos.171439] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 11/15/2017] [Indexed: 05/14/2023]
Abstract
Hypoxia within the oviducts maintains embryonic arrest in turtles at the pre-ovipositional stage, which expands the timeframe over which nesting can occur without compromising embryo survival. The arrest can be extended post-oviposition through incubation of eggs in hypoxia. We determined whether crocodilian embryos have this same capacity. We also tested whether increased oxygen availability during incubation alters hatching success. We incubated freshly laid saltwater crocodile (Crocodylus porosus) eggs (N = 83) at 32°C in one of five treatments; control (normoxia; 21% O2), 3-day and 6-day hypoxia (1% O2), or 3-day and 6-day hyperoxia (42% O2). Incubation (approx. 82 days) was then completed in normoxia. There was a significant effect of treatment on survival of embryos through to hatching (p < 0.001). The hypoxic treatments resulted in almost no hatching (6.7% and 0% survival for the 3- and 6-day treatments, respectively), while the hyperoxic and control treatments resulted in normal to high hatching success (86.6%, 100% and 64.2% for the control, 3- and 6-day hyperoxic treatments, respectively). Unlike turtles, hypoxic incubation of crocodile eggs failed to delay development. Our results provide the first experimental evidence that, unlike turtles, crocodiles do not exhibit embryonic arrest when incubated under hypoxic conditions immediately following oviposition. An absence of embryonic arrest is of ecological and evolutionary significance, as it implies that crocodilians lack an ability to avoid adverse environmental conditions through delayed nesting and that, unlike turtles, embryonic arrest may not be a potential explanation for the lack of viviparity in the order Crocodylia.
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Affiliation(s)
- Sean A. Williamson
- School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia
- Author for correspondence: Sean A. Williamson e-mail:
| | - Roger G. Evans
- Cardiovascular Disease Program, Biosciences Discovery Institute and Department of Physiology, Monash University, Clayton, Victoria 3800, Australia
| | - S. Charlie Manolis
- Wildlife Management International Pty Limited, PO Box 530, Karama, Northern Territory 0813, Australia
| | - Grahame J. Webb
- Wildlife Management International Pty Limited, PO Box 530, Karama, Northern Territory 0813, Australia
- Research Institute for the Environment and Livelihoods, Charles Darwin University, Darwin, Northern Territory 0909, Australia
| | - Richard D. Reina
- School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia
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