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Reptile embryos lack the opportunity to thermoregulate by moving within the egg

Telemeco, Rory S.; Gangloff, Eric J.; Cordero, Gerardo A.; Mitchell, Timothy S.; Bodensteiner, Brooke L.; Holden, Kaitlyn G.; Mitchell, Sarah M.; Polich, Rebecca L. and Janzen, Fredric J. (2016) In American Naturalist 188(1). p.13-27
Abstract

Historically, egg-bound reptile embryos were thought to passively thermoconform to the nest environment. However, recent observations of thermal taxis by embryos of multiple reptile species have led to the widely discussed hypothesis that embryos behaviorally thermoregulate. Because temperature affects development, such thermoregulation could allow embryos to control their fate far more than historically assumed. We assessed the opportunity for embryos to behaviorally thermoregulate in nature by examining thermal gradients within natural nests and eggs of the common snapping turtle (Chelydra serpentina; which displays embryonic thermal taxis) and by simulating thermal gradients within nests across a range of nest depths, egg sizes, and... (More)

Historically, egg-bound reptile embryos were thought to passively thermoconform to the nest environment. However, recent observations of thermal taxis by embryos of multiple reptile species have led to the widely discussed hypothesis that embryos behaviorally thermoregulate. Because temperature affects development, such thermoregulation could allow embryos to control their fate far more than historically assumed. We assessed the opportunity for embryos to behaviorally thermoregulate in nature by examining thermal gradients within natural nests and eggs of the common snapping turtle (Chelydra serpentina; which displays embryonic thermal taxis) and by simulating thermal gradients within nests across a range of nest depths, egg sizes, and soil types. We observed little spatial thermal variation within nests, and thermal gradients were poorly transferred to eggs. Furthermore, thermal gradients sufficiently large and constant for behavioral thermoregulation were not predicted to occur in our simulations. Gradients of biologically relevant magnitude have limited global occurrence and reverse direction twice daily when they do exist, which is substantially faster than embryos can shift position within the egg. Our results imply that reptile embryos will rarely, if ever, have the opportunity to behaviorally thermoregulate by moving within the egg. We suggest that embryonic thermal taxis instead represents a play behavior, which may be adaptive or selectively neutral, and results from the mechanisms for behavioral thermoregulation in free-living stages coming online prior to hatching.

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author
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Chelydra serpentina, Microclim, Nest, Play, Snapping turtle, Soil, Temperature
in
American Naturalist
volume
188
issue
1
pages
13 - 27
publisher
University of Chicago Press
external identifiers
  • scopus:84975141209
ISSN
0003-0147
DOI
10.1086/686628
language
English
LU publication?
no
id
fdc7f092-6e11-4664-8ae6-f92e9426a72e
date added to LUP
2017-01-17 16:04:42
date last changed
2017-09-24 05:05:57
@article{fdc7f092-6e11-4664-8ae6-f92e9426a72e,
  abstract     = {<p>Historically, egg-bound reptile embryos were thought to passively thermoconform to the nest environment. However, recent observations of thermal taxis by embryos of multiple reptile species have led to the widely discussed hypothesis that embryos behaviorally thermoregulate. Because temperature affects development, such thermoregulation could allow embryos to control their fate far more than historically assumed. We assessed the opportunity for embryos to behaviorally thermoregulate in nature by examining thermal gradients within natural nests and eggs of the common snapping turtle (Chelydra serpentina; which displays embryonic thermal taxis) and by simulating thermal gradients within nests across a range of nest depths, egg sizes, and soil types. We observed little spatial thermal variation within nests, and thermal gradients were poorly transferred to eggs. Furthermore, thermal gradients sufficiently large and constant for behavioral thermoregulation were not predicted to occur in our simulations. Gradients of biologically relevant magnitude have limited global occurrence and reverse direction twice daily when they do exist, which is substantially faster than embryos can shift position within the egg. Our results imply that reptile embryos will rarely, if ever, have the opportunity to behaviorally thermoregulate by moving within the egg. We suggest that embryonic thermal taxis instead represents a play behavior, which may be adaptive or selectively neutral, and results from the mechanisms for behavioral thermoregulation in free-living stages coming online prior to hatching.</p>},
  author       = {Telemeco, Rory S. and Gangloff, Eric J. and Cordero, Gerardo A. and Mitchell, Timothy S. and Bodensteiner, Brooke L. and Holden, Kaitlyn G. and Mitchell, Sarah M. and Polich, Rebecca L. and Janzen, Fredric J.},
  issn         = {0003-0147},
  keyword      = {Chelydra serpentina,Microclim,Nest,Play,Snapping turtle,Soil,Temperature},
  language     = {eng},
  month        = {07},
  number       = {1},
  pages        = {13--27},
  publisher    = {University of Chicago Press},
  series       = {American Naturalist},
  title        = {Reptile embryos lack the opportunity to thermoregulate by moving within the egg},
  url          = {http://dx.doi.org/10.1086/686628},
  volume       = {188},
  year         = {2016},
}