Meeting Abstract
P3.211 Sunday, Jan. 6 Environmental cues of seasonal acclimation in the Eastern red spotted newt (Notophthalmus viridescens viridescens) WALDRUP, C.L.; BERNER, N.J.*; Sewanee: University of the South; Sewanee: University of the South nberner@sewanee.edu
Eastern red spotted newts are active in the winter. Our previous work shows that they acclimate enzyme activity, metabolic rate, behavioral thermoregulation, and membrane phospholipid fatty acid (FA) composition in skeletal muscle seasonally, in the field and in the laboratory. Here, we studied the relative influence of temperature and photoperiod on these seasonally plastic characteristics. While most studies of seasonal acclimation in ectothermic vertebrates have used fixed photoperiods, photoperiod influences physiology in our model species. The activity rhythm of N. viridescens is shifted by modified light cycles, and part of the seasonal variation in their critical thermal maximum is responsive to photoperiod (Hutchison, 1961; Demain and Taylor, 1977). We maintained newts (fed bloodworms ad libitum) in the laboratory in four acclimation groups: summer light/summer temperature (SL/ST); SL/winter temperature (WT); winter light (WL)/ST; and WL/WT. Photoperiods (WL = L:D 10:14 and SL = L:D 14:10) and acclimation temperatures (WT = 8°C and ST = 26°C) were based on local conditions. After maintaining the newts at these conditions for 12 weeks we determined their standard metabolic rates (SMR, measured as oxygen consumption after one week of food deprivation) at 26 and 8°C. We also measured enzyme activity (cytochrome c oxidase, CCO, and citrate synthase, CS) in liver and skeletal muscle tissue at 26 and 8°C and determined membrane FA composition of these tissues. The SL/WT acclimation group had the highest SMR (p < 0.001) at both 26 and 8°C, and the highest skeletal muscle membrane polyunsaturated FA content (p < 0.001) while SL/ST was lowest in both of these characteristics. While temperature was sufficient for acclimation of SMR, the interaction with photoperiod was significant.
