PETERSON, C.C.*; LIGON, D.B.: Acute and acclimational effects of temperature on metabolic rates of hatchling slider turtles: embryonic metabolic compensation?

Reptile embryos may blunt the acute physiological effects of incubation temperature through chronic acclimation (compensation) of anabolic and developmental processes, and an integrated consequence of such adjustments is temperature compensation of metabolic rates. We gauged the capacity for temperature compensation in embryos of the red-eared slider turtle (Trachemys scripta) by incubating eggs from nine fertile clutches at 26°C, 29°C, and 32°C, and then measuring resting metabolic rates (RMR; oxygen consumption) of resultant hatchlings (3-6 d old) at the same three temperatures. Individual RMR was repeatable over two consecutive days and across temperatures, scaled to body mass (6-11 g), and showed a strong acute response to temperature (mean Q₁₀ = 3.1). RMR acclimated to incubation temperature such that turtles incubated at 26°C had the highest rates, and those incubated at 32°C the lowest, at all three measurement temperatures. Metabolic compensation was “perfect” between incubation temperatures of 26°C and 29°C, but partial between 29°C and 32°C. Incubation temperature strongly affected average embryonic growth rate and incubation period, yet had no effect on hatchling size or mass-conversion efficiency. Observed patterns of compensation in whole-animal metabolic rate presumably integrate biochemical adjustments that level the thermal playing field and conserve the energetics of embryonic development.