Document Detail

Limited oxygen availability in utero may constrain the evolution of live birth in reptiles.
MedLine Citation:
PMID:  23348778     Owner:  NLM     Status:  In-Data-Review    
Abstract Although viviparity (live birth) has evolved from oviparity (egg laying) at least 140 times in vertebrates, nearly 120 of these independent events occurred within a single reptile taxon. Surprisingly, only squamate reptiles (lizards and snakes) are capable of facilitating embryonic development to increasingly advanced stages inside the mother during extended periods of oviducal egg retention. Viviparity has never evolved in turtle lineages, presumably because embryos enter and remain in an arrested state until after eggs are laid, regardless of the duration of egg retention. Until now, the limiting factor that initiates and maintains developmental arrest has remained elusive. Here, we show that oviducal hypoxia arrests embryonic development. We demonstrate that hypoxia can maintain developmental arrest after oviposition and that subsequent exposure of arrested embryos to normoxia triggers resumption of their development. We discovered remarkably low oxygen partial pressure in the oviducts of gravid turtles and found that secretions produced by the oviduct retard oxygen diffusion. Our results suggest that an extremely hypoxic environment in the oviduct arrests embryonic development and may constrain the evolution of viviparity in turtles, with the reduced diffusive capacity of oviducal secretions possibly creating or contributing to this hypoxia. We anticipate that these findings will allow us to better understand the mechanisms underlying the evolutionary transition between reproductive modes.
Anthony R Rafferty; Roger G Evans; T Franciscus Scheelings; Richard D Reina
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Publication Detail:
Type:  Journal Article     Date:  2013-01-04
Journal Detail:
Title:  The American naturalist     Volume:  181     ISSN:  1537-5323     ISO Abbreviation:  Am. Nat.     Publication Date:  2013 Feb 
Date Detail:
Created Date:  2013-01-25     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  2984688R     Medline TA:  Am Nat     Country:  United States    
Other Details:
Languages:  eng     Pagination:  245-53     Citation Subset:  IM    
Australian Centre for Biodiversity, School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia.
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