Dataset Information

The effect of respiratory gases and incubation temperature on early stage embryonic development in sea turtles.

ABSTRACT: Sea turtle embryos at high-density nesting beaches experience relative high rates of early stage embryo death. One hypothesis to explain this high mortality rate is that there is an increased probability that newly constructed nests are located close to maturing clutches whose metabolising embryos cause low oxygen levels, high carbon dioxide levels, and high temperatures. Although these altered environmental conditions are well tolerated by mature embryos, early stage embryos, i.e. embryos in eggs that have only been incubating for less than a week, may not be as tolerant leading to an increase in their mortality. To test this hypothesis, we incubated newly laid sea turtle eggs over a range of temperatures in different combinations of oxygen and carbon dioxide concentrations and assessed embryo development and death rates. We found that gas mixtures of decreased oxygen and increased carbon dioxide, similar to those found in natural sea turtle nests containing mature embryos, slowed embryonic development but did not influence the mortality rate of early stage embryos. We found incubation temperature had no effect on early embryo mortality but growth rate at 27°C and 34°C was slower than at 30°C and 33°C. Our findings indicate that low oxygen and high carbon dioxide partial pressures are not the cause of the high early stage embryo mortality observed at high-density sea turtle nesting beaches, but there is evidence suggesting high incubation temperatures, particularly above 34°C are harmful. Any management strategies that can increase the spacing between nests or other strategies such as shading or irrigation that reduce sand temperature are likely to increase hatching success at high-density nesting beaches.

SUBMITTER: Booth DT

PROVIDER: S-EPMC7710074 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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The effect of respiratory gases and incubation temperature on early stage embryonic development in sea turtles.

Booth David Terrington DT Archibald-Binge Alexander A Limpus Colin James CJ

PloS one 20201202 12

Sea turtle embryos at high-density nesting beaches experience relative high rates of early stage embryo death. One hypothesis to explain this high mortality rate is that there is an increased probability that newly constructed nests are located close to maturing clutches whose metabolising embryos cause low oxygen levels, high carbon dioxide levels, and high temperatures. Although these altered environmental conditions are well tolerated by mature embryos, early stage embryos, i.e. embryos in eg ...[more]

PMID: 33264278

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Project description:BackgroundReeves' Turtles (Mauremys reevesii) are economically important in aquaculture in China. Understanding the effects of incubation temperature and substrate moisture on embryos and hatchlings is of great significance for improving the artificial culture of M. reevesii. However, available studies have not yet determined the thermal and hydric optima for M. reevesii eggs, and the potential interaction between the two factors.MethodsIn this study, eggs of M. reevesii were incubated at five temperature levels (23, 26, 29, 32 and 35 °C, fluctuation range ± 0.5 °C). In each temperature level, there were three substrate moisture levels (1:0.5, 1:0.9 and 1:1.2, weight ratio of vermiculite to water). Thus, a total of 15 combinations of temperature and moisture were used to examine the effects of incubation temperature and substrate moisture on incubation duration, hatching success, hatchling phenotypes, post-hatching growth and hatchling survival.ResultsSubstrate moisture did not significantly affect most development parameters (except incubation duration and carapace width of hatchlings). Eggs incubated at low moisture level (1:0.5) had a longer incubation duration and produced hatchlings with smaller carapace widths than those incubated at medium (1:0.9) or high (1:1.2) moisture levels. Incubation temperature had a significant effect on incubation duration, hatching success, hatchling phenotypes and hatchling survival. Incubation duration decreased as incubation temperature increased. Eggs incubated at 23, 26 and 29 °C showed higher hatching success than those incubated at 32 and 35 °C. Hatchlings incubated at 32 °C were smaller in body size and mass than those incubated at 23, 26 and 29 °C. At 12 months of age, incubation temperature had no long-lasting effect on body mass, but hatchlings incubated at 23 and 35 °C had lower survival rates than those incubated at 26, 29 and 32 °C. For the development of embryos and hatchlings, the interaction between incubation temperature and substrate moisture was not significant.ConclusionsOur results indicate that incubation temperature has a significant influence on the development of embryos and hatchlings of M. reevesii, while substrate moisture only significantly affects the incubation duration and carapace width of hatchlings. The combination of an incubation temperature of 29 ± 0.5 °C and a substrate moisture level of 1:1.2 represented optimal incubation conditions in this experiment. Such incubation conditions are helpful in obtaining higher hatching success, shorter incubation duration and higher survival rates for this aquaculture species.

Dataset Information

The effect of respiratory gases and incubation temperature on early stage embryonic development in sea turtles.

Publications

The effect of respiratory gases and incubation temperature on early stage embryonic development in sea turtles.

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