A series of stages in the embryonic development of <i>Chelydra serpentina</i>

Yntema, C. L.

doi:10.1002/jmor.1051250207

Cited by 425 publications

(421 citation statements)

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“…Unfortunately, these early stages are when development is most thermally sensitive (Yntema 1968;Shine and Elphick 2001;Birchard 2004), and embryos could most affect their fitness by thermoregulating. Still, thermoregulation in the latter two-thirds of development could provide some benefit, such as increasing the rate of development, allowing heat-stress avoidance, and potentially adjusting offspring sex (Georges et al 2005;Janzen 2008;Du and Shine 2015).…”

Section: E22 the American Naturalistmentioning

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: E22 the American Naturalistmentioning

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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“…At this temperature the average incubation time was 60 days. The embryonic ages were determined accordi ng to speci fic stages of turtle development (Yntema 1968). All embryos and hatched animals were treated according to the European Un ion and the Spanish government regulations and standards.…”

Section: Methodsmentioning

confidence: 99%

Ultrastructural study of retinal development in the turtle Trachemys scripta elegans

et al. 2016

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The present study was conducted by using light and transmission electron microscopy to examine the morphologic development of turtle retina from embryonic stage 18 (S 18) to S26 (hatchin g). Particular attention was paid to the formation of functional structures such as neurites, synapses, photorecep tors, among others, and the moment that chemical synapses appear in the outer and inner plex iform layers. The results show that retinal differentiation in the turtle fo llows the vitreal to scleral morphological differentiation of retinal cells. Moreover, the central region of the optic cup is most advanced compared to the peripheral parts. Early functi onal plexiform layers, based on appearance of sy napses, precede the complete di ffe rentiation of photoreceptors. The first synaptic structures occur in the inner plexiform layer before the outer plex iform layer. Receptor outer segments and first synaptic ribbon in receptor sy napti c terminal s initiate the differentiation at the same time, but final maturation includes dendriti c invagi nations of bipolar and hori zonta l cells in the receptor termi nals. We assume that at birt h, the turtle retina has achieved the ability to see.

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“…McKernan et al [8] reported the presence of several PBDE congeners in the egg contents of several species of birds that had been injected with DE-71 but were not detected in the dosing solution or control eggs. Although early embryonic development of red-eared sliders and snapping turtles is similar [42,43], species-specific differences are likely in enzymatic systems potentially responsible for differential capacities for debromination, as has been shown in fish exposed to BDE-99 [7,10]. Several studies of fish have shown debromination of BDE-99 to BDE-47 in carp, but other species such as Chinook salmon and rainbow trout demonstrate different reductive metabolite products and slower formation rates [6,7,9,10].…”

Section: Discussionmentioning

confidence: 97%

“…Study timeline indicating the timing of dosing, exposures, incubations, study termination, and approximate stages of development at each step. The stages are based on Yntema [42], which is based on snapping turtle embryonic development in eggs incubated at 208C. Ã The date for the start of hatching is based on the date that the eggs from the control treatment of a concurrent study began hatching.…”

Section: Methodsmentioning

confidence: 99%

Experimental exposure of eggs to polybrominated diphenyl ethers BDE‐47 and BDE‐99 in red‐eared sliders (Trachemys scripta elegans) and snapping turtles (Chelydra serpentina) and possible species‐specific differences in debromination

Eisenreich¹,

Rowe²

2012

Enviro Toxic and Chemistry

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Abstract-Polybrominated diphenyl ethers (PBDEs) are a bioaccumulative, persistent, and toxic class of flame retardants that can potentially impact turtles in natural habitats via exposure through maternal transfer. To simulate maternal transfer in the present study, PBDE congeners BDE-47 and BDE-99 were topically applied to the eggshell and were allowed to diffuse into the egg contents of the redeared slider (Trachemys scripta elegans) and snapping turtle (Chelydra serpentina). Eggs were topically dosed over 8 d to achieve a target concentration of 40 ng/g in the egg contents. Transfer efficiency was higher for BDE-47 than for BDE-99 in the red-eared sliders (25.8 AE 1.9% vs 9.9 AE 1.1%) and snapping turtles (31.3 AE 1.6% vs 12.5 AE 1.4%), resulting in greater BDE-47 and lower BDE-99 egg content concentrations relative to the 40 ng/g target. However, only 25.8 and 31.3% of the total BDE-47 and 9.9 and 12.5% of the total BDE-99 dose applied could be accounted for in the red-eared slider and snapping turtle egg contents, respectively. Additionally, increased BDE-47 in red-eared slider egg contents dosed with only BDE-99 indicate that BDE-99 might have been debrominated to BDE-47. The efficacy of topical dosing for administering desired embryonic exposures is clearly affected by the chemical properties of the applied compounds and was more successful for BDE-47 in both species. Environ. Toxicol. Chem.

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A series of stages in the embryonic development of Chelydra serpentina

Cited by 425 publications

References 12 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

Ultrastructural study of retinal development in the turtle Trachemys scripta elegans

Experimental exposure of eggs to polybrominated diphenyl ethers BDE‐47 and BDE‐99 in red‐eared sliders (Trachemys scripta elegans) and snapping turtles (Chelydra serpentina) and possible species‐specific differences in debromination

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