Interspecific Variation in Temperature Effects on Embryonic Metabolism and Development in Turtles

We measured temperature-induced differences in metabolic rates and growth by embryos of three turtle species, Macrochelys temminckii, Trachemys scripta , and Apalone spinifera , at different, constant, temperatures. Oxygen consumption rate (VO 2 ) was measured during development and used to characterize changes in metabolism and calculate total O 2 consumption. Results from eggs incubated at different temperatures were used to calculate Q 10 s at different stages of development and to look for evidence of metabolic compensation. Total O 2 consumption over the course of incubation was lowest at high incubation temperatures, and late-term metabolic rate Q 10 s were <2 in all three species. Both results were consistent with positive metabolic compensation. However, incubation temperature effects on egg mass-corrected hatchling size varied among species. Apalone spinifera hatchling mass was unaffected by temperature, whereas T. scripta mass was greatest at high temperatures and M. temminckii mass was lowest at high temperatures. Hatchling mass : length relationships tended to correlate negatively with temperature in all three species. Although we cannot reject positive metabolic compensation as a contributor to the observed VO 2 patterns, there is precedence for drawing the more parsimonious conclusion that differences in yolk-free size alone produced the observed incubation temperature differences without energetic canalization by temperature acclimation during incubation.