Table 1.

Citrate synthase (CS) and cytochrome c oxidase (COX) enzyme activity (units mg–1 protein) and mRNA levels (relative to total RNA) in northern (N) and southern (S) killifish subspecies acclimated to 5, 15 or 25°C

Population5°C15°C25°C
Liver
   CS enzyme activityN0.06±0.004a,*0.04±0.002b0.04±0.003b
S0.05±0.003x0.04±0.004x,y0.04±0.002y
   CS mRNAN1.89±0.352a,*1.09±0.148b,*1.25±0.086b,*
S0.85±0.136x0.43±0.112x0.35±0.060x
Muscle
   CS enzyme activityN0.06±0.005a,*0.04±0.003b0.04±0.005b
S0.04±0.002x0.03±0.001x0.04±0.005x
   CS mRNAN0.84±0.071a,*0.39±0.064b0.52±0.093b,*
S0.26±0.053x0.21±0.061x0.16±0.023x
Liver
   COX enzyme activityN0.25±0.012a,*0.22±0.020a0.21±0.010a
S0.17±0.017x0.17±0.025x0.18±0.026x
   COX mRNAN0.80±0.063a0.61±0.048b0.57±0.054b
S0.9±0.091x0.56±0.053y0.66±0.062y
Muscle
   COX enzyme activityN0.04±0.006a0.05±0.005a0.05±0.004a
S0.05±0.008x0.05±0.006x0.05±0.009x
   COX mRNAN1.19±0.222a,*0.70±0.108b1.00±0.151a,b
S0.65±0.090x0.51±0.072x0.71±0.078x
  • Significant differences within a population between acclimation temperatures are indicated with different letters. An asterisk (*) indicates a significant difference between populations at a given acclimation temperature (indicated on northern values). Data are expressed as means± s.e.m. (N=8), and P≤0.05 for all significant comparisons