Abstract
Eastern red‐spotted newts are ectotherms, aquatic as adults, and active year‐round, breeding even during winter under ice. Earlier research, with field‐captured newts, showed a correlation between seasonal changes in the activity of some muscle metabolic enzymes and in the behavior of the newts in a thermal gradient. This study was undertaken to further characterize acclimatory responses in the newts in a more controlled laboratory environment. Newts were obtained during fall, and maintained at 15°C with 12:12 LD for 4 weeks for SMR (at 8 and 26°C) and temperature preference experiments. Subsequently, half the newts were exposed to summer conditions (26°C, 14:10 LD) and half to winter conditions (8°C, 10:14 LD). After 12 weeks, SMR and temperature preference experiments were repeated, and enzyme assays for cytochrome c oxidase (CCO), citrate synthase (CS), and lactate dehydrogenase (LDH) were performed on muscle tissue homogenates, also at 8 and 26°C. Newts changed all three parameters in the laboratory. SMRs were highest in winter‐acclimated newts and lowest in summer‐acclimated newts, whereas temperature preference was lowest in winter‐acclimated newts and highest in summer‐acclimated newts. Finally, CCO activity was completely compensated in winter‐acclimated newts, CS activity was partially compensated, and LDH activity was not seasonally sensitive. These results indicate a connection or relationship between changes in seasonal environmental conditions, and some aspects of the muscle biochemistry, SMR, and thermoregulatory behavior of these ectotherms. J. Exp. Zool. 313A:231–239, 2010. © 2010 Wiley‐Liss, Inc.