Intermediary Energy Metabolism during Dormancy and Anoxia in the Land Snail Otala lactea

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Abstract
Metabolic responses to dormancy and anoxia were assessed in foot muscle and he-patopancreas of the land snail Otala lactea (Pulmonata, Helicidae). In both states cellular energetics (arginine phosphate content, adenylate energy charge) were maintained at a high level, fueled during estivation by aerobic metabolism and during anoxia by carbohydrate fermentation. D-lactate was the major product of anaerobiosis in hepatopancreas, but in foot muscle D-lactate, L-alanine, and succi-nate accumulated (in net amounts of 13.5, 3.5, and 1.8 μmolg⁻¹ wet weight, respec-tively). Changes in the concentrations of glycolytic intermediates were compared for both short-and long-term stress: 2 and 14 h of exposure to N₂ gas atmosphere, 3 and 22 d of dormancy at 22° C. Both stresses appeared to include glycolytic activation in the short term in foot muscle, with crossover analyses indicating regulatory control at the phosphofructokinase, aldolase, and pyruvate kinase loci. Over the long term, however, this was reversed and a glycolytic rate depression was observed aspart of the overall metabolic rate depression of these states. In foot muscle, inhibition at phosphofructokinase and pyruvate kinase was apparent during anoxia, whereas aldolase and pyruvate kinase were the key sites of inhibitory control during estivation. In hepatopancreas, phosphofructokinase was the primary locus for inhibitory control during both prolonged anoxia and estivation. These data suggest that common molecular mechanisms underlie glycolytic rate depression during dormancy and anaerobiosis.

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