The Effect of Prolonged Anoxia on Enzyme Activities in Oysters (Crassostrea virginica) at Different Seasons
The effect of prolonged anoxia (96 h under a N2 atmosphere) during either winter (November) or summer (July) was investigated by measuring the maximal activities of 20 metabolic enzymes in gill, mantle, hepatopancreas, and phasic and catch adductor muscles of the oyster, Crassostrea virginica. The enzymes analyzed are involved in carbohydrate and amino acid metabolism, the pentose phosphate shunt, anaplerotic reactions of the TCA cycle, and phosphagen/adenylate metabolism. The data demonstrate that oyster metabolism is influenced by both long-term seasonal change and by shorter-term environmental insult (anoxia). Seasonal changes were concentrated among enzymes involved in glycogen metabolism whereas the prominent response to anoxia was suppression of PK activity. Anoxia exposure induced tissue-specific changes in enzyme activities suggesting a substantial metabolic reorganization involving both coarse controls on enzyme amount and reversible covalent modification. In addition, the effects of anoxia on enzymes of intermediary metabolism were seasonally dependent and more widespread in the winter. These results demonstrate the interaction of two environmental variables (season, anoxia) and suggest the importance of season as a modifying factor in the anoxic response.