RESPIRATION, ELECTRON-TRANSPORT ENZYMES, AND KREBS-CYCLE ENZYMES IN EARLY DEVELOPMENTAL STAGES OF THE OYSTER CRASSOSTREA VIRGINICA

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Abstract
1. Measurements of respiration, cytochrome o.xidase, and the DPNH oxidase system, as well as five enzymes of the citric acid cycle, aconitase, isocitric dehydrogenase, alpha-ketoglutaric dehydrogenase, succinic dehydrogenase, and malic dehydrogenase, have been made in oyster embryos between the first cleavage and the early veliger stage. The rate of respiration increases 9-fold to the trochophore stage and levels off until the veliger stage is reached. Succinic dehydrogenase, DPNH oxidase, malic dehydrogenase and aconitase were not found to change appreciably during development to the veliger. Cytochrome oxidase showed no significant change prior to the trochophore stage, but decreases were found in this enzyme after this stage. Isocitric dehydrogenase and alpha-ketoglutaric dehydrogenase were found to increase, paralleling the increase in respiration, between the blastula and trochophore stages. Following this stage, these enzymes remain constant in activity up to the veliger stage. 2. The results are shown to be in contrast to those obtained for the sea urchin by other workers. The possible relationships between changes in enzyme activities and increases in respiratory rate are considered.