ULRICH, Paul N.*; MARSH, Adam G.; University of Delaware; University of Delaware: Tissue-specific differences and interindividual variation of malate dehydrogenase activity and protein content in the oyster Crassostrea virginica

Malate dehydrogenases (MDH, mitochondrial and cytosolic) are integral to bivalve metabolism with particular importance during anaerobiosis. We found that the specific activities of heart and phasic adductor in the oyster Crassostrea virginica are significantly different (p < .0005), with heart having 2.5-fold higher specific activity than the adductor. In addition, we observed substantial levels of interindividual variation in both tissues. From a sampling of 100+ individuals, there was a wide range of MDH activities and protein content. But activity and protein content in the phasic adductor were 30-35% less variable than that of the heart. The tissue-specific patterns and range of MDH and protein titers define a continuum of biochemical phenotypes important for understanding the contribution of metabolism to functional variations in higher levels of physiological performance. We are further investigating the degree of interindividual variation in temperate vs. polar bivalve metabolism using a high-throughput, microtiter-plate methodology for simultaneous measurements of mitochondrial respiration rate, reactive oxygen species production, and membrane potential.