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First published online April 17, 2009
Journal of Experimental Biology 212, 1302-1306 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.027425
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Determinants of incubation period: do reptilian embryos hatch after a fixed total number of heart beats?

Wei-Guo Du1,2,*, Rajkumar S. Radder1,{dagger}, Bo Sun2 and Richard Shine1

1 School of Biological Sciences A08, University of Sydney, NSW, 2006 Australia
2 Hangzhou Key Laboratory for Animal Science and Technology, College of Biological and Environmental Sciences, Hangzhou Normal University, 310036, Hangzhou, People's Republic of China

* Author for correspondence (e-mail: dwghz{at}126.com)

Accepted 9 February 2009

The eggs of birds typically hatch after a fixed (but lineage-specific) cumulative number of heart beats since the initiation of incubation. Is the same true for non-avian reptiles, despite wide intraspecific variation in incubation period generated by variable nest temperatures? Non-invasive monitoring of embryo heart beat rates in one turtle species (Pelodiscus sinensis) and two lizards (Bassiana duperreyi and Takydromus septentrionalis) show that the total number of heart beats during embryogenesis is relatively constant over a wide range of warm incubation conditions. However, incubation at low temperatures increases the total number of heart beats required to complete embryogenesis, because the embryo spends much of its time at temperatures that require maintenance functions but that do not allow embryonic growth or differentiation. Thus, cool-incubated embryos allocate additional metabolic effort to maintenance costs. Under warm conditions, total number of heart beats thus predicts incubation period in non-avian reptiles as well as in birds (the total number of heart beats are also similar); however, under the colder nest conditions often experienced by non-avian reptiles, maintenance costs add significantly to total embryonic metabolic expenditure.

Key words: embryonic development, heart rate, metabolic rate, thermal dependence, reptile, thermal time


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JEB 2009 212: i. [Full Text]  



This article has been cited by other articles:


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