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

Abstract

We measured temperature-induced differences in metabolic rates and growth by embryos of three turtle species,Macrochelys temminckii, Trachemys scripta, andApalone spinifera, at different, constant, temperatures. Oxygen consumption rate (VO2) was measured during development and used to characterize changes in metabolism and calculate total O2consumption. Results from eggs incubated at different temperatures were used to calculate Q10s at different stages of development and to look for evidence of metabolic compensation. Total O2consumption over the course of incubation was lowest at high incubation temperatures, and late-term metabolic rate Q10s 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 spiniferahatchling mass was unaffected by temperature, whereasT. scriptamass was greatest at high temperatures andM. temminckiimass 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 VO2patterns, 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.