High‐Energy Phosphate Metabolism during Exercise and Recovery in Temperate and Antarctic Scallops: An In Vivo31P‐NMR Study

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Abstract
In vivo 31P-nuclear magnetic resonance (NMR) spectroscopy was used to measure the levels of ATP, phospho-l-arginine (PLA), and inorganic phosphate in the adductor muscle of the Antarctic scallop Adamussium colbecki and two temperate spe- cies, Aequipecten opercularis and Pecten maximus. Graded ex- ercise regimes from light (one to two contractions) to ex- hausting (failing to respond to further stimulation) were imposed on animals of each species at its habitat temperature (0 vs. 12C, respectively). NMR spectroscopy allowed nonin- vasive measurement of metabolite levels and intracellular pH at high time resolution (30-120-s intervals) during exercise and throughout the recovery period. Significant differences were shown between the magnitude and form of the metabolic re- sponse with increasing levels of exercise in each species. After exhaustion, short-term (first 15 min) muscle alkalosis was fol- lowed by acidosis of up to 0.2 pH units during the recovery process. Aequipecten opercularis had similar resting muscle PLA levels compared with either P. maximus or A. colbecki but used a fivefold greater proportion of this store per contraction and was able to perform only half as many claps (maximum of 24) as the other species before exhaustion. All species regenerated their PLA store at a similar rate despite different environmental temperatures. These findings argue for some cold compensation of muscular performance and recovery capacities in the Ant-