Hydric environmental effects on turtle development and sex ratio
TL;DR: How moisture may change the incubation conditions inside nests by changing the temperature experienced by eggs, which affects development, growth and sex ratios is shown.
About: This article is published in Zoology.The article was published on 2017-11-01. It has received 27 citations till now. The article focuses on the topics: Sex ratio.
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TL;DR: A review of the most recent literature on this topic can be found in this article, highlighting knowledge gains and research gaps since a similar previous review in 2009, and suggesting a number of research priorities for an improved understanding of how climate change may impact marine turtles, including: improved estimates of primary sex ratios, assessments of the implications of femalebiased sex ratios and reduced male production, assessment of the variability in upper thermal limits of clutches, models of beach sediment movement under sea level rise, and assessments of impacts on foraging grounds.
Abstract: Climate change is a threat to marine turtles that is expected to affect all of their life stages. To guide future research, we conducted a review of the most recent literature on this topic, highlighting knowledge gains and research gaps since a similar previous review in 2009. Most research has been focussed on the terrestrial life history phase, where expected impacts will range from habitat loss and decreased reproductive success to feminization of populations, but changes in reproductive periodicity, shifts in latitudinal ranges, and changes in foraging success are all expected in the marine life history phase. Models have been proposed to improve estimates of primary sex ratios, while technological advances promise a better understanding of how climate can influence different life stages and habitats. We suggest a number of research priorities for an improved understanding of how climate change may impact marine turtles, including: improved estimates of primary sex ratios, assessments of the implications of female-biased sex ratios and reduced male production, assessments of the variability in upper thermal limits of clutches, models of beach sediment movement under sea level rise, and assessments of impacts on foraging grounds. Lastly, we suggest that it is not yet possible to recommend manipulating aspects of turtle nesting ecology, as the evidence base with which to understand the results of such interventions is not robust enough, but that strategies for mitigation of stressors should be helpful, providing they consider the synergistic effects of climate change and other anthropogenic-induced threats to marine turtles, and focus on increasing resilience.
54 citations
Cites background from "Hydric environmental effects on tur..."
...This is likely due to evaporative cooling (Lolavar & Wyneken 2017, 2020); further studies will allow us to clarify the mechanism behind these observations, as this is a major avenue for future research (Sifuentes-Romero et al. 2018)....
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TL;DR: The current state of the‐art in TSD research on sea turtles is reviewed here and it is proposed that TSD provides an advantage under warming climates, by means of coadaptation between early survival and sex ratios, sea turtles are able to maintain populations.
Abstract: The adaptive significance of temperature-dependent sex determination (TSD) in reptiles remains unknown decades after TSD was first identified in this group. Concurrently, there is growing concern about the effect that rising temperatures may have on species with TSD, potentially producing extremely biased sex ratios or offspring of only one sex. The current state-of the-art in TSD research on sea turtles is reviewed here and, against current paradigm, it is proposed that TSD provides an advantage under warming climates. By means of coadaptation between early survival and sex ratios, sea turtles are able to maintain populations. When offspring survival declines at high temperatures, the sex that increases future fecundity (females) is produced, increasing resilience to climate warming. TSD could have helped reptiles to survive mass extinctions in the past via this model. Flaws in research on sex determination in sea turtles are also identified and it is suggested that the development of new techniques will revolutionize the field.
21 citations
TL;DR: In this paper, the effects of five different climate variables at different temporal scales on loggerhead sea turtle (Caretta caretta) hatchling production from North Florida, USA were investigated.
Abstract: The environment and climate in which sea turtle eggs incubate affects how successful and viable hatchlings are. Therefore, it is crucial to understand how local climate impacts sea turtle hatchling production as well as how potential changes in climate may impact future hatchling production. In this study, we investigated the effects of five different climate variables at different temporal scales on loggerhead sea turtle (Caretta caretta) hatchling production from North Florida, USA. Humidity, air temperature, and accumulated precipitation were the main climatic drivers of hatchling production, while sea surface temperature and wind speed did not demonstrate to have strong effects. Climate projections show air temperatures increasing at the nesting beaches throughout the 21st century, while precipitation and humidity projections vary between sites and projection scenarios. Due to the temperate nature of these nesting beaches, increases in hatching success for nests that incubate undisturbed (not affected by depredation and storm-related impacts) are projected for this region by 2100. This study demonstrates how different climate variables and their interactions can have a determining effect on an important marine species.
21 citations
TL;DR: The results of this study are crucial for understanding how sea turtle embryos respond to temperature directly or indirectly under different moisture conditions and may inaccurately estimate sex ratios especially during periods of heavy rainfall or drought.
19 citations
TL;DR: The results consistently showed that incubation temperature exerts the greatest influence on swimming performance and that maternal origin (clutch) has a significant effect on individual hatchling morphology, highlighting the need for careful temperature management to produce hatchlings with optimal swimming capacities and, hence, highest survival probabilities.
18 citations
References
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TL;DR: The 2-Delta Delta C(T) method as mentioned in this paper was proposed to analyze the relative changes in gene expression from real-time quantitative PCR experiments, and it has been shown to be useful in the analysis of realtime, quantitative PCR data.
139,407 citations
TL;DR: The normalization strategy presented here is a prerequisite for accurate RT-PCR expression profiling, which opens up the possibility of studying the biological relevance of small expression differences.
Abstract: Gene-expression analysis is increasingly important in biological research, with real-time reverse transcription PCR (RT-PCR) becoming the method of choice for high-throughput and accurate expression profiling of selected genes. Given the increased sensitivity, reproducibility and large dynamic range of this methodology, the requirements for a proper internal control gene for normalization have become increasingly stringent. Although housekeeping gene expression has been reported to vary considerably, no systematic survey has properly determined the errors related to the common practice of using only one control gene, nor presented an adequate way of working around this problem. We outline a robust and innovative strategy to identify the most stably expressed control genes in a given set of tissues, and to determine the minimum number of genes required to calculate a reliable normalization factor. We have evaluated ten housekeeping genes from different abundance and functional classes in various human tissues, and demonstrated that the conventional use of a single gene for normalization leads to relatively large errors in a significant proportion of samples tested. The geometric mean of multiple carefully selected housekeeping genes was validated as an accurate normalization factor by analyzing publicly available microarray data. The normalization strategy presented here is a prerequisite for accurate RT-PCR expression profiling, which, among other things, opens up the possibility of studying the biological relevance of small expression differences.
18,261 citations
"Hydric environmental effects on tur..." refers methods in this paper
...scripta β-actin was used as an internal control (Forward: 5′-CAC CCA CAC TGT GCC CAT CT-3′; Reverse: 5′-CAC GAT TTC CCT TTC GGC TGT-3′) in order to normalize raw Sox9 CT data (ΔCT) (Vandesompele et al., 2002)....
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...T. scripta β-actin was used as an internal control (Forward: 5′-CAC CCA CAC TGT GCC CAT CT-3′; Reverse: 5′-CAC GAT TTC CCT TTC GGC TGT-3′) in order to normalize raw Sox9 CT data (ΔCT) (Vandesompele et al., 2002)....
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TL;DR: A general model is derived, based on first principles of allometry and biochemical kinetics, that predicts the time of ontogenetic development as a function of body mass and temperature, and suggests a general definition of biological time that is approximately invariant and common to all organisms.
Abstract: Body size and temperature are the two most important variables affecting nearly all biological rates and times. The relationship of size and temperature to development is of particular interest, because during ontogeny size changes and temperature often varies. Here we derive a general model, based on first principles of allometry and biochemical kinetics, that predicts the time of ontogenetic development as a function of body mass and temperature. The model fits embryonic development times spanning a wide range of egg sizes and incubation temperatures for birds and aquatic ectotherms (fish, amphibians, aquatic insects and zooplankton). The model also describes nearly 75% of the variation in post-embryonic development among a diverse sample of zooplankton. The remaining variation is partially explained by stoichiometry, specifically the whole-body carbon to phosphorus ratio. Development in other animals at other life stages is also described by this model. These results suggest a general definition of biological time that is approximately invariant and common to all organisms.
841 citations
"Hydric environmental effects on tur..." refers background in this paper
...The effect of temperature on the developmental rate of embryos has been widely studied in a variety of taxa (Gillooly and Dodson, 2000; Gillooly et al., 2002)....
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TL;DR: Eggs of Crocodilia and Chelonia have a pair of egg membranes separating a thick layer of albumen from the calcareous shell, while eggs of oviparous Lepidosauria have only a single shell membrane, upon which relatively small amounts of calcium carbonate are deposited.
Abstract: SUMMARY
1. Eggs of Crocodilia and Chelonia, like those of birds, have a pair of egg membranes separating a thick layer of albumen from the calcareous shell. In contrast, eggs of oviparous Lepidosauria have only a single shell membrane, upon which relatively small amounts of calcium carbonate are deposited; and the volume of albumen in eggs is extraordinarily small at the time of oviposition.
2. With the possible exception of certain geckos and some chelonians, eggs of oviparous reptiles seem always to absorb water from the substrate during the course of normal incubation. In so far as the rate of water absorption exceeds the rate of water loss by transpiration from exposed surfaces, the eggs swell during incubation. The term ‘cleidoic’ cannot be used to describe eggs of this type.
3. Embryos of lizards and snakes influence the water potential of extra-embryonic fluids contained within their eggs, thereby maintaining or increasing the gradient in water potential that drives water absorption.
4. Embryos of Crocodilia and Chelonia obtain a substantial portion of the calcium used in ossification of skeletal elements from the inner surfaces of the eggshell. In contrast, embryonic lizards and snakes draw upon extensive reserves of calcium present in the yolk, and obtain little (if any) calcium from the eggshell.
5. All reptilian embryos seem to produce substantial quantities of urea as a detoxification product of protein catabolism. Contrary to expectation, uricotelism may not be common among reptilian embryos, even in those few instances where development takes place within a hard, calcareous egg.
6. In eggs of Crocodilia and Chelonia, respiratory gases seem to pass by diffusion through pores in the calcareous eggshell and through spaces between the fibres of the pair of egg membranes. No pores have been observed in the shell of lepidosaurian eggs, and so gases presumably diffuse between the fibres of the single (multilayered) shell membrane.
7. Metabolism of reptilian embryos is temperature-dependent, as is true for most ectothermic organisms. For each species, there appears to be a particular temperature at which embryonic development proceeds optimally, and departures from this optimum elicit increases in developmental anomalies and/or embryonic mortality.
8. Viviparity has evolved on numerous occasions among species of the Squamata, but seemingly never among Crocodilia or Chelonia. Since the evolution of viviparity entails a progressive reduction in the eggshell, only those organisms whose embryos do not depend upon the eggshell as a source of calcium may have the evolutionary potential to become viviparous.
9. Evolutionary transitions from oviparity to viviparity could have been driven by selection related to (i) thermal benefits to embryos consequent upon retention of eggs within the body of a parent capable of behavioural thermoregulation; (ii) protection of the eggs from nest predators and/or soil microbes; and (iii) more effective exploitation of a seasonal food resource by early emerging young.
536 citations
"Hydric environmental effects on tur..." refers background in this paper
...In reptiles, the thermal environment can influence embryonic growth rate (Packard et al., 1977; Deeming and Ferguson, 1989; Georges et al., 2005; Ligon and Lovern, 2012) and therefore, incubation duration (Yntema, 1978; Lolavar and Wyneken, 2015)....
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TL;DR: Eggs of the common snapping turtle, Chelydra serpentina serpentina, were incubated at 30°C and at 20°C to determine the incubation period and a series of 26 stages of development is described.
Abstract: Eggs of the common snapping turtle, Chelydra serpentina serpentina were incubated at 30°C and at 20°C. The incubation period at the higher temperature was about 63 days. At the lower temperature, the period was estimated to be 140 days. Lengths of the embryos at various times of development were recorded. A series of 26 stages is described. The staging is based on timed intervals at a constant temperature, 20°C.
422 citations
"Hydric environmental effects on tur..." refers background in this paper
...…a narrow range of temperatures with a lower and upper lethal limit (Ackerman, 1997; Du and Ji, 2003) and they are especially sensitive to temperature changes at early stages, when crucial developmental processes including histogenesis and organogenesis take place (Yntema, 1968; Birchard, 2004)....
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...Turtle embryos develop successfully over a narrow range of temperatures with a lower and upper lethal limit (Ackerman, 1997; Du and Ji, 2003) and they are especially sensitive to temperature changes at early stages, when crucial developmental processes including histogenesis and organogenesis take place (Yntema, 1968; Birchard, 2004)....
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