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Ecological and evolutionary significance of a lack of capacity for extended developmental arrest in crocodilian eggs

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 cr...

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Autores principales: Williamson, Sean A., Evans, Roger G., Manolis, S. Charlie, Webb, Grahame J., Reina, Richard D.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The Royal Society Publishing 2017
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5750033/
https://www.ncbi.nlm.nih.gov/pubmed/29308266
http://dx.doi.org/10.1098/rsos.171439
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author Williamson, Sean A.
Evans, Roger G.
Manolis, S. Charlie
Webb, Grahame J.
Reina, Richard D.
author_facet Williamson, Sean A.
Evans, Roger G.
Manolis, S. Charlie
Webb, Grahame J.
Reina, Richard D.
author_sort Williamson, Sean A.
collection PubMed
description 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% O(2)), 3-day and 6-day hypoxia (1% O(2)), or 3-day and 6-day hyperoxia (42% O(2)). 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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spelling pubmed-57500332018-01-07 Ecological and evolutionary significance of a lack of capacity for extended developmental arrest in crocodilian eggs Williamson, Sean A. Evans, Roger G. Manolis, S. Charlie Webb, Grahame J. Reina, Richard D. R Soc Open Sci Biology (Whole Organism) 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% O(2)), 3-day and 6-day hypoxia (1% O(2)), or 3-day and 6-day hyperoxia (42% O(2)). 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. The Royal Society Publishing 2017-12-20 /pmc/articles/PMC5750033/ /pubmed/29308266 http://dx.doi.org/10.1098/rsos.171439 Text en © 2017 The Authors. http://creativecommons.org/licenses/by/4.0/ Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited.
spellingShingle Biology (Whole Organism)
Williamson, Sean A.
Evans, Roger G.
Manolis, S. Charlie
Webb, Grahame J.
Reina, Richard D.
Ecological and evolutionary significance of a lack of capacity for extended developmental arrest in crocodilian eggs
title Ecological and evolutionary significance of a lack of capacity for extended developmental arrest in crocodilian eggs
title_full Ecological and evolutionary significance of a lack of capacity for extended developmental arrest in crocodilian eggs
title_fullStr Ecological and evolutionary significance of a lack of capacity for extended developmental arrest in crocodilian eggs
title_full_unstemmed Ecological and evolutionary significance of a lack of capacity for extended developmental arrest in crocodilian eggs
title_short Ecological and evolutionary significance of a lack of capacity for extended developmental arrest in crocodilian eggs
title_sort ecological and evolutionary significance of a lack of capacity for extended developmental arrest in crocodilian eggs
topic Biology (Whole Organism)
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5750033/
https://www.ncbi.nlm.nih.gov/pubmed/29308266
http://dx.doi.org/10.1098/rsos.171439
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