Incubation conditions of the loggerhead sea turtle Caretta caretta in kyparissia Bay, western Peloponnesus, Greece
The primary aims of this three year study were to investigate the incubation environment of Caretta caretta embryos, and how this related to clutch survival and hatchling phenotype. Incubation temperature (mean 30.4 °C, n=33 nests) was significantly related to laying date and female choice of nest site. Nests laid early or late in the season, or further down the beach were more likely to attain temperatures below the pivotal for sex determination. Overall, a female biased sex ration was estimated. Low temperatures at the start of incubation and deeper nests were associated with higher early embryonic mortality. Older embryonic death increased due to seawater inundation and shallower nest depth. Post-hatching mortality increased with higher temperatures in the egg chamber at the end of incubation. Hatchling body sizes were not significantly influenced by any of the variables considered. Rates of oxygen consumption and carbon dioxide production in eggs artificially incubated at 27.5, 29.9, and 31.8 °C, increased during the second half of incubation, reaching greater maxima at higher incubation temperatures, then declining towards hatching. Respirometry quotients indicated temporal changes in substrate utilisation, with a shift from carbohydrate, to protein, and finally fat oxidation. Carbon dioxide concentrations increased then reached asymptote in natural nests. Analysis of the ratio of carbon-13 to carbon-12 (determined by mass spectrometry) revealed that the increase in nest CO2 concentration was attributable to embryonic metabolism. Nest CO2 concentration increased with the number of developing embryos to a maximum of 1.8 %, but did not have a negative effect on hatchling success, suggesting substrate diffusion capacity does not constrain clutch mass.