Turtle embryos move to optimal thermal environments within the egg

Li, Teng; Shine, Richard; Du, Wei‐Guo

doi:10.1098/rsbl.2013.0337

Cited by 32 publications

(52 citation statements)

References 11 publications

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“…The ability of sea turtles to cope with contemporary climate change will depend on their adaptability to increasing temperatures, which could include changes in phenology (Weishampel et al 2004, Pike et al 2006, Telemeco et al 2013b, changes in nesting beach or nest-site choice (Weber et al 2012), latitudinal advantages (Hawkes et al 2007, Pike 2014, and, potentially, the thermoregulation of individual embryos inside of the egg (as has been documented in Chinese pond turtles Chinemys reevesii; Zhao et al 2013). The pace at which contemporary climate change is occurring could be more rapid than the adaptation of sea turtles to such change (Hamann et al 2013).…”

Section: Potential Of Turtles To Adapt To Increasing Nest Temperaturesmentioning

confidence: 99%

Thermal tolerances of sea turtle embryos: current understanding and future directions

Howard¹,

Bell²,

Pike³

2014

Endang. Species. Res.

126

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Developing sea turtle embryos only successfully hatch within a relatively narrow temperature range, rendering this immobile life stage vulnerable to the vagaries of climate change. To accurately predict the potential impact of climate change on sea turtle egg mortality, we need to fully understand the thermal tolerance of developing embryos. We reviewed the literature on this topic, and found that published studies interpret the primary literature and subsequent reviews very differently. Based on early literature reviews, the maximum thermal tolerance of sea turtle embryos is frequently cited as either 33 or 35°C. In many sea turtle populations, however, nest temperatures often exceed 35°C by up to several degrees (usually just prior to hatchling emergence) and eggs still hatch successfully. Mean incubation temperatures up to 35°C generally produce hatchlings, although leatherback and olive ridley turtle embryos may be less tolerant of high incubation temperatures than green and loggerhead turtle embryos. Sea turtle embryos are likely to be more sensitive to the duration of time spent at potentially stressful temperatures than to the temperature alone. To complicate matters, developing embryos may change their thermal tolerance as they grow. Overall, we are only beginning to understand how exposure to high temperatures experienced in the field influences embryonic development and hatchling production. This knowledge gap is hampering our ability to predict the impacts of climate change on sea turtle populations, and future work should focus on understanding how temperature and other climatic variables influence embryonic development and, thus, crucial population attributes such as hatchling production.

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Section: Potential Of Turtles To Adapt To Increasing Nest Temperaturesmentioning

confidence: 99%

Thermal tolerances of sea turtle embryos: current understanding and future directions

Howard¹,

Bell²,

Pike³

2014

Endang. Species. Res.

126

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“…Box width is scaled to sample size. Dashed lines represent quadratic least squares regressions fitted to these data and are presented to illustrate the shape of each estimated reaction though see Du et al 2011;Zhao et al 2013). If embryos are exposed to high environmental thermal variance, they should be under selection for broad thermal tolerance (Huey and Kingsolver 1989;Angilletta et al 2002¿, 2013Kingsolver and Gomulkiewicz 2003).…”

Section: Thermal Sensitivity Of Immobile and Mobile Life-history Stagesmentioning

confidence: 99%

“…In contrast, developing embryos are confined to immobile eggs and largely at the mercy of the nest environment (Ackerman and Lott 2004;Refsnider and Janzen 2010), although limited behavioral thermorégulation within the egg has been suggested (Du et al 2011;Zhao et al 2013). Thus, the free-living and embryonic stages of oviparous reptiles likely differ greatly in their ability to maintain body temperatures near a thermal optimum.…”

Section: Introductionmentioning

confidence: 99%

Immobile and Mobile Life-History Stages Have Different Thermal Physiologies in a Lizard

Telemeco

2014

Physiological and Biochemical Zoology

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Temperature affects multiple aspects of an organism's biology and thus defines a major axis of the fundamental niche. For ectotherms, variation in the thermal environment is particularly important because most of these taxa have a limited capacity to thermoregulate via metabolic heat production. While temperature affects all life-history stages, stages can differ in their ability to respond to the thermal environment. For example, in oviparous organisms, free-living adults can behaviorally thermoregulate, whereas developing embryos are at the mercy of the nest environment. These differences in the realized thermal environment should select for life-history stages to have different thermal tolerances, although this has been rarely examined. I tested the hypothesis that stage-specific thermal reaction norms can evolve independently by using southern alligator lizards (Elgaria multicarinata, Anguidae). Using incubation experiments (five temperatures: 24°, 26°, 28°, 30°, and 32°C), I described the thermal reaction norm for embryonic development and compared these results to previous studies on the thermal ecology of adults. Offspring survivorship and morphology were similarly affected by incubation temperature. While developing embryos had the same optimum temperature as adults (approximately 28°C), the breadth of their thermal reaction norms differed. My results suggest that developing embryos of E. multicarinata are more sensitive to variation in the average thermal environment than are adults. Variation in the thermal sensitivity of life-history stages might be common and has implications for how organisms respond to variation in the thermal environment. Identifying those life-history stages that are most sensitive/limiting will be important for developing models that best predict species' responses to impending environmental change.

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“…That assumption was falsified by recent studies that documented thermoregulatory behavior in turtle embryos. Embryos of the Chinese soft-shelled turtle (Pelodiscus sinensis) moved within the egg to find a warmer area (Du et al 2011), and embryos of an emydid turtle (Chinemys reevesii) moved toward warmer areas and away from dangerously high temperatures (Zhao et al 2013).…”

Section: Introductionmentioning

confidence: 99%

“…Thermoregulatory behavior of embryos thus appears to be genuinely analogous to that of posthatching ectotherms (Zhao et al 2013), but the generality of this behavior remains unknown. Although many posthatching ectotherms regulate their body temperatures by exploiting thermal heterogeneity in the environment, this behavior is not universal: some species conform to ambient temperatures (Huey 1982;Hertz et al 1993).…”

Section: Introductionmentioning

confidence: 99%

Thermoregulatory Behavior Is Widespread in the Embryos of Reptiles and Birds

Zhou

et al. 2014

The American Naturalist

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Recent studies have demonstrated that thermoregulatory behavior occurs not only in posthatching turtles but also in turtles prior to hatching. Does thermoregulatory behavior also occur in the embryos of other reptile and bird species? Our experiments show that such behavior is widespread but not universal in reptile and bird embryos. We recorded repositioning within the egg, in response to thermal gradients, in the embryos of three species of snakes (Xenochrophis piscator, Elaphe bimaculata, and Zaocys dhumnades), two turtles (Chelydra serpentina and Ocadia sinensis), one crocodile (Alligator sinensis), and four birds (Coturnix coturnix, Gallus gallus domesticus, Columba livia domestica, and Anas platyrhynchos domestica). However, we detected no significant thermoregulation by the embryos of two lizard species (Takydromus septentrionalis and Phrynocephalus frontalis). Overall, embryonic thermoregulatory behavior is widespread in reptile as well as bird species but may be unimportant in the small eggs laid by most lizards.

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Turtle embryos move to optimal thermal environments within the egg

Cited by 32 publications

References 11 publications

Thermal tolerances of sea turtle embryos: current understanding and future directions

Thermal tolerances of sea turtle embryos: current understanding and future directions

Immobile and Mobile Life-History Stages Have Different Thermal Physiologies in a Lizard

Thermoregulatory Behavior Is Widespread in the Embryos of Reptiles and Birds

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