Meeting Abstract
23.2 Friday, Jan. 4 Acclimation in the Eastern red spotted newt (Notophthalmus viridescens viridescens) BERNER, N.J.; Sewanee:University of the South, Sewanee, TN nberner@sewanee.edu
Eastern red spotted newts are ectotherms, aquatic as adults, and active year-round, breeding even during winter under ice. Field-captured newts seasonally acclimatize the activity of some muscle metabolic enzymes, as well as their behavior in a thermal gradient. Cytochrome c oxidase (CCO) and citrate synthase (CS) completely or partially (respectively) compensate during winter, while lactate dehydrogenase (LDH) activity is not affected seasonally. In addition, winter-captured newts have a colder temperature preference than summer-captured newts. The present study had two goals: 1) to investigate the ability of these newts to acclimate in the laboratory when exposed to summer versus winter light and temperature conditions, and 2) to add standard metabolic rate (SMR) as an acclimation parameter. Newts were obtained during fall, and maintained at 15�C with 12:12 light/dark for 4 weeks for SMR and temperature preference experiments. Subsequently, half the newts were exposed to summer conditions (26�C, 14:10 light/dark) and half to winter conditions (8�C, 10:14 light/dark). After 12 weeks, SMR and temperature preference experiments were repeated, and enzyme assays for CCO, CS and LDH were performed on muscle tissue homogenates. Newts acclimated all three parameters in the laboratory. SMRs were highest in winter-acclimated newts and lowest in summer-acclimated newts, while 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 direct cause/effect between changes in seasonal environmental conditions and some aspects of the muscle biochemistry, SMR and thermoregulatory behavior of these ectotherms.
