Carbon dioxide fixation in marine invertebrates: a survey of major phyla

Fourteen species of marine invertebrates representing 12 phyla were kept in sea water containing NaHC(14)O(2) for 1 hour. All of them fixed CO(2) into acids of the Krebs citric acid cycle. In most species the major portion of the radioactivity recovered after chromatography was in succinic, fumaric, and malic acids. The findings favor the hypothesis that both CO(2) fixation and the citric acid cycle are virtually universal among marine invertebrates.