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Data from: How well do embryo development rate models derived from laboratory data predict embryo development in sea turtle nests?

Citation

Booth, David (2022), Data from: How well do embryo development rate models derived from laboratory data predict embryo development in sea turtle nests?, Dryad, Dataset, https://doi.org/10.5061/dryad.wh70rxwqc

Abstract

Development rate of ectothermic animals varies with temperature. Here we use data derived from laboratory constant temperature incubation experiments to formulate development rate models that can be used to model embryonic development rate in sea turtle nests. We then use a novel method for detecting the time of hatching to measure the in situ incubation period of sea turtle clutches to test the accuracy of our models in predicting the incubation period from nest temperature traces. We found that all our models overestimated the incubation period. We hypothesize three possible explanations which are not mutually exclusive for the mismatch between our modeling and empirically measured in situ incubation period: (1) a difference in the way the incubation period is calculated in laboratory data and in our field nests, (2) inaccuracies in the assumptions made by our models at high incubation temperatures where there is no empirical laboratory data, and (3) a tendency for development rate in laboratory experiments to be progressively slower as temperature decreases compared with in situ incubation.

Methods

Field measurements of nest temperature, incubation period, and the hatch‐to‐emerge time The field procedures were similar for loggerhead and green turtle clutches, but the field locations and times were different. Experiments with loggerhead turtle clutches were conducted at Mon Repos Beach between December 6, 2019 and February 15, 2020, and experiments with green turtle clutches were conducted at Heron Island between December 13, 2020 and February 9, 2021. A nesting female was located, and immediately after oviposition had finished, her eggs were collected into a bucket and carried by hand to an area of the nesting beach which was corralled to prevent subsequent nesting turtles from disturbing monitored nests. An artificial nest hole was dug by hand to a depth of 60 cm (loggerhead turtles) or 70 cm (green turtles) and the collected eggs placed into this hole. When approximately 50 eggs had been placed in the hole, an iButton temperature data logger (iButton™ Maxim, Model DS1922L, resolution of 0.06°C, accuracy ± 0.2°C) programmed to log temperature every hour was placed in the nest and then the remainder of the eggs were placed on top of the logger in the nest. The hole was then backfilled with sand and the nest site marked with a wooden stake. The clutch collection and relocation procedures were completed within 1 h of the end of oviposition. The clutch was then left to incubate naturally on the beach. Two weeks before the clutch was expected to hatch, the nest was excavated by hand until the top layer of eggs was exposed, and a “hatching detector” was installed. The hatching detector consisted of a ~2‐mm‐wide strip of aluminum foil 15 cm long that was placed either beneath the top layer of eggs (loggerhead turtles) or on top of the incubating eggs (green turtles), and the ends of the foil were connected via alligator clips to wires that lead to the surface. The nest was then back‐filled with sand and left to continue incubation. Thereafter, between six and eight times per day the ends of the wires at the surface were connected to a 9‐ volt transistor battery in a series circuit with a 1000 ohm resistor. A voltmeter was then used to measure the electrical potential (emf) (V) across the resistor. When the aluminum foil strip was intact, the emf was always ~9 V, but when it was broken (by hatchlings as they emerged from their eggs) the emf fell dramatically to between 2 and 5 V. The emf did not fall to zero when the aluminum strip was broken because electricity continued to be conducted via ions dissolved in water within the sand in the nest between the broken ends of the aluminum strip. The time when the emf fell from 9 V was recorded as the hatch date and time.

Usage Notes

See readme.txt file.

Funding

World Wildlife Fund, Award: 1