Ultrastructural observations and pH-measurements on red and white muscle from Antarctic fish

Abstract

Red and white muscle in the two Antarctic notothenioid fishes Dissostichus mawsoni and Pagothenia borchgrevinki show a rate of postmortem fall of 0.2 pH units per hour, which is close to the rate reported for mammalian muscle at 30°C, but the plateau value is reached several hours earlier in the Antarctic fish, indicating significantly lower stores of initial glycogen. A few particles, most likely representing glycogen, were seen in P. borchgrevinki white muscle and D. mawsoni red muscle, whereas predictably fewer glycogen still was evident in D. mawsoni white muscle. When large numbers of mitochondria and lipid stores were encountered in combination with a small amount of glycogen, we concluded that aerobic metabolism is dominant and that the two species examined would not use white trunk muscle for sustained or slow swimming. Rapid contractions of white trunk muscle as in prey capture or predator evasion are more likely.