Abstract
To examine the presence of metabolic cold adaptation in Antarctic isopods, whole animal rates of oxygen uptake (MVo2) and protein synthesis were measured in Glyptonotus antarcticus at 0 degree C and compared with the temperature isopod Idotea rescata at 4 and 14 degrees C. The specific relationship between rates of metabolism and protein synthesis was investigated by injecting animals with cycloheximide, a protein synthesis inhibitor. In G. antarcticus, routine MVo2 was 11.10 +/- 0.89 mumol.kg-1.min-1 (n = 19 animals), and ks was 0.24 +/- 0.04% protein synthesized/day (n = 8 animals). Comparison with I. rescata showed that standardized whole animal MVo2 decreased with temperature (temperature quotient = 1.99), but whole animal ks was considerably lower in the Antarctic isopod; 66 and 22% of total MVo2 was attributable to protein synthesis in G. antarcticus at 0 degree C and I. rescata at 4 degrees C, respectively. The energetic cost of protein synthesis was four times higher in G. antarcticus at 885 +/- 141 mmol ATP/g protein (n = 5 animals) compared with 237 +/- 76 mmol ATP/g protein (n = 6) in I. rescata. G. antarcticus does not show metabolic rate compensation and maintains extremely low ks levels because of the relatively high energetic cost of protein synthesis.
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