Synchronised nesting aggregations are associated with enhanced capacity for extended embryonic arrest in olive ridley sea turtles

Williamson, Sean A.; Evans, Roger G.; Robinson, Nathan J.; Reina, Richard D.

doi:10.1038/s41598-019-46162-3

Cited by 15 publications

(26 citation statements)

References 22 publications

(27 reference statements)

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“…Failed eggs may be incorrectly categorized as 'infertile' if mortality occurs before the embryo is visible upon inspection by eye. Intra-oviducal embryonic mortality can occur during gastrulation or developmental arrest, and potentially at higher rates if eggs are retained in the oviduct during a long inter-clutch interval (Rafferty et al 2011, Booth & Dunstan 2018 but also see Rings et al 2015, Williamson et al 2019. Embryos at this time are developed to Stages 1−6 (Miller 1985) and < 2 mm in length (Miller 1985, Miller et al 2017.…”

Section: Fertilization and Early Embryonic Development And Mortalitymentioning

confidence: 99%

Assessing the evidence of ‘infertile’ sea turtle eggs

Phillott

Godfrey

2020

Endang. Species. Res.

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There is increasing concern about feminization of sea turtle populations resulting from female-biased production of hatchlings due to climate change and selective loss of males from other anthropogenic drivers. Extreme female-biased breeding populations would reduce the likelihood of successful mating and potentially result in high rates of infertile eggs. Infertile eggs are those in which none of the events between sperm penetration of the ovum and syngamy have occurred. Distinguishing between fertile and infertile eggs is challenging, especially in field conditions, and researchers often have relied on physical evidence gathered from unhatched eggs at the end of the incubation period, which likely have experienced tissue decomposition. We argue that infertility in sea turtle eggs can be demonstrated only by the absence of holes caused by sperm penetration of the inner perivitelline membrane; sperm bound between the inner and outer perivitelline membranes; nuclei in the blastodisc; embryonic tissue or membranes in egg contents; and/or the characteristic white spot on the egg exterior. Unhatched eggs can be examined at the end of the incubation period, but we recommend that studies specifically investigating infertility examine at least 20 oviposited eggs each from clutches laid by at least 20 different turtles at the peak of the nesting season.

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Section: Fertilization and Early Embryonic Development And Mortalitymentioning

confidence: 99%

Assessing the evidence of ‘infertile’ sea turtle eggs

Phillott

Godfrey

2020

Endang. Species. Res.

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“…The copyright holder for this preprint this version posted June 21, 2021. ; https://doi.org/10.1101/2021.06.21.449061 doi: bioRxiv preprint 6 [6]. Increased concentrations of gonadosteroids might also influence whether an individual joins the arribada.…”

Section: Potential Endocrine Drivers Of Arribada Nestingmentioning

confidence: 99%

“…Olive ridley turtles nesting in arribadas can extend their inter-nesting intervals up to 63 days by inducing hypoxia-driven pre-ovipositional embryonic arrest so they can synchronize to nest [5,6]. Environmental cues that might trigger arribadas include the moon phase, weather patterns, and rainfall [2,7].…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, nesting in arribada increases early hatchling dispersal by overwhelming or satiating predators [11]; however, arribada nesting does not necessarily promote hatchling success as increased organic matter from egg saturation and high nesting density in arribada beaches result in lower hatchling success compared to solitary nesting [3,12,13]. In contrast, solitary nesters produce bigger hatchlings, which have higher male-to-female ratio than hatchlings produced by arribada nesters [1,6]. Thus, while both nesting modes are likely important for the population, it is unknown if the potential fitness benefits associated with arribada nesting come with a physiological cost.…”

Section: Introductionmentioning

confidence: 99%

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Oxidative stress is a potential cost of synchronous nesting in olive ridley sea turtles

Harfush-Melendez

Ensminger

et al. 2021

Preprint

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Olive ridley sea turtles, Lepidochelys olivacea, exhibit a polymorphic reproductive behaviour nesting in solitary or in mass aggregations termed "arribadas", where thousands of turtles nest at once. Arribadas may provide fitness benefits including mate finding during nearshore aggregations and predator satiation at the time of hatching, but the potential costs of arribada nesting remain understudied. To explore the potential trade-offs of the fitness benefits associated with arribada nesting, we collected blood from olive ridley turtles nesting in arribada and solitary. We measured reproductive and metabolic hormones (progesterone, estradiol, testosterone, thyroxine, and triiodothyronine), triglycerides (TG), non-esterified fatty acids (NEFA) and markers of oxidative damage (4-hydroxynonenal, malondialdehyde, protein carbonyls, and nitrotyrosine). Arribada nesters were bigger and had higher levels of progesterone than solitary nesters. Similarly, thyroid hormones were higher in individuals nesting in arribada than in solitary nesters, while TG and NEFA were positively correlated in arribada but not in solitary nesters. Nesting in arribada was associated with increased lipid peroxidation and protein carbonyls compared to solitary nesting. These results suggest that nesting in arribada is potentially more energetically expensive than nesting solitarily, and that oxidative stress may be a trade-off of the fitness benefits associated with arribada nesting.

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“…We collected the eggs for our experiments from low density nesting populations in which we knew by checking flipper tag numbers that the females laid their clutch on their first laying attempt. Previous reports [26][27][28] indicate that retention of eggs for several days within the female reproductive tract due to multiple failed nesting attempts that frequently occurs at high nest-density beaches, causes a decrease in egg viability. Hence, it is possible that at high nestdensity beaches a combination of prolonged egg retention and exposure of eggs to low oxygen, high carbon dioxide partial pressures and high nest temperatures result in a higher frequency of early stage embryo mortality.…”

Section: Plos Onementioning

confidence: 99%

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

2020

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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.

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Synchronised nesting aggregations are associated with enhanced capacity for extended embryonic arrest in olive ridley sea turtles

Cited by 15 publications

References 22 publications

Assessing the evidence of ‘infertile’ sea turtle eggs

Assessing the evidence of ‘infertile’ sea turtle eggs

Oxidative stress is a potential cost of synchronous nesting in olive ridley sea turtles

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

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