Anaerobic metabolism of the ribbed mussel, Geukensia demissa
Abstract
The anaerobic metabolism of the intertidal ribbed mussel, Geukensia demissa (= Modiolus demissus), is reported in this dissertation. This mollusc was selected because anaerobic metabolism is believed to be of vital significance to its survival during the air exposure period of the tidal cycle.;Ribbed mussels, Geukensia demissa, were maintained in either aerated or hypoxic water for up to four days. Major metabolites and polysaccharide of each mussel were then analyzed and compared. Succinate, propionate and alanine were found to accumulate hypoxically, but not malate, (alpha)-keto-glutarate and pyruvate. The polysaccharide content of each mussel was quite different and did not show a clear indication of decrease under the hypoxic condition.;Propionate production followed succinate accumulation, which corroborates an earlier report for Mytilus edulis. The linear increase of alanine concentration with hypoxic period observed in this study, has not been reported previously.;The results of this study are consistent with those of Mytilus edulis, Cardium edule, and Anodonta cygnea, bivalves which have recently been studied in Europe. This agreement that bivalves have a similar anaerobic metabolic scheme.;A hypothetical scheme of anaerobic metabolism of bivalves is proposed in which redox balance is achieved in both cytosol mitochondria. This scheme incorporates parts of the Embden-Meyerhof-Parnas glycolytic pathways, carbon dioxide fixation, the Krebs cycle, transamination, and pathways for propionate formation. To date, this is the only bivalve anaerobic scheme which contains all these essential considerations.
