Water and Heat Exchange between Parchment-Shelled Reptile Eggs and Their Surroundings

Ackerman, Ralph A.; Seagrave, Richard C.; Dmi'el, Razi; Ar, Amos

doi:10.2307/1444764

Cited by 84 publications

(78 citation statements)

References 15 publications

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“…For example, in species that produce exceptionally large nests (e.g., sea turtles and crocodilians), metabolic heat production by the embryos can produce a thermal gradient from the center to the periphery of the nest (Godfrey et al 1997;Booth and Astill 2001;Ewert and Nelson 2003;DeGregorio and Williard 2011). However, such gradients occur late in development, when embryos have grown to fill the majority of the egg's space (Ackerman et al 1985;Godfrey et al 1997;Ewert and Nelson 2003;Zbinden et al 2006). Moreover, these thermal gradients are small, with gradients from the center to periphery of the nest generally ranging from 0.57C to 37C (Godfrey et al 1997;Booth and Astill 2001;Broderick 2001;DeGregorio and Williard 2011), and gradients at the egg scale substantially smaller.…”

Section: Function Of Embryo Movement In Reptiles E23mentioning

confidence: 99%

Reptile Embryos Lack the Opportunity to Thermoregulate by Moving within the Egg

Telemeco

Gangloff

Cordero

et al. 2016

The American Naturalist

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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. KeywordsChelydra serpentina, microclim, nest, play, soil, snapping turtle, temperature Disciplines Ecology and Evolutionary Biology | Evolution | Population Biology CommentsThis article is from The American Naturalist 188 (2016) 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 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...

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Section: Function Of Embryo Movement In Reptiles E23mentioning

confidence: 99%

Reptile Embryos Lack the Opportunity to Thermoregulate by Moving within the Egg

Telemeco

Gangloff

Cordero

et al. 2016

The American Naturalist

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“…This increase in egg temperature would result in a water potential between the egg and the saturated atmosphere at 12°C of -0.0347 kPa; a very small driving force. Debate concerning the effects of temperature on liquid and vapour exchange of water in reptilian eggs has shown the importance of temperature differences on vapour pressure (see Ackerman et al, 1985;Thompson, 1987). Alternatively, the swelling of the egg in liquid water is related to the gel-like properties of the capsule.…”

Section: Incubation In Aqueous Versus Vapour Phasesmentioning

confidence: 99%

Phenotypic differences in terrestrial frog embryos: effect of water potential and phase

Andrewartha

Mitchell

Frappell

2008

Journal of Experimental Biology

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SUMMARYThe terrestrial embryos of many amphibians obtain water in two ways; in a liquid phase from the substrate on which eggs are deposited, and in a vapour phase from the surrounding atmosphere. We tested whether the mode of water flux (liquid or vapour) affected the morphology and metabolic traits of the terrestrial Victorian smooth froglet (Geocrinia victoriana) embryos by incubating eggs both with a liquid water source and at a range of vapour water potentials. We found that embryos incubated with a liquid water source (ψ π =0 kPa) were better hydrated than embryos incubated with a vapour water source (ψ v =0 kPa), and grew to a larger size. Eggs incubated in atmospheres with lower ψ v values showed significant declines in mass and in the thickness of the jelly capsule, while embryos primarily showed reductions in dry mass, total length, tail length and fin height. The most significant deviations from control (ψ v =0 kPa) values were observed when the ψ v of the incubation media was less than the osmotic water potential (ψ π ) of the embryonic interstitial fluid (approximately -425 kPa). Despite the caveat that a ψ v of 0 kPa is probably difficult to achieve under our experimental conditions, the findings indicate the importance for eggs under natural conditions of contacting liquid water in the nesting substrate to allow swelling of the capsule.

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“…Especially in oviparous species, where offspring develop outside the mother's body, incubation environments can have long-lasting effects [4,5]. Thermal, hydric and gasexchange conditions all vary within [6] as well as among nests [7], generating variation among hatchlings in phenotypic traits such as sex, body size, shape and locomotor ability [5,8].…”

Section: Introductionmentioning

confidence: 99%

Hotter nests produce smarter young lizards

Amiel

Shine

2012

Biol. Lett.

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A hatchling reptile's sex, body size and shape, and locomotor performance can be influenced not only by its genes, but also by the temperature that it experiences during incubation. Can incubation temperature also affect a hatchling's cognitive skills? In the scincid lizard Bassiana duperreyi, higher incubation temperatures enhanced the resultant hatchling's learning performance. Hence, factors such as maternal nest-site selection and climate change affect not only the size, shape and athletic abilities of hatchling reptiles, but also their ability to learn novel tasks.

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Water and Heat Exchange between Parchment-Shelled Reptile Eggs and Their Surroundings

Cited by 84 publications

References 15 publications

Reptile Embryos Lack the Opportunity to Thermoregulate by Moving within the Egg

Reptile Embryos Lack the Opportunity to Thermoregulate by Moving within the Egg

Phenotypic differences in terrestrial frog embryos: effect of water potential and phase

Hotter nests produce smarter young lizards

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