Relation of habitat to glycogen concentration and glycogen synthetase in polychaetes

The glycogen content of whole body or muscle of 14 species of polychaetes was determined, and the activity, co-factor requirements, and substrate affinity of glycogen synthetase from muscles of 4 of the species were measured. Species average glycogen concentrations were positively correlated with the risk of anoxia each species faced in the field. Total activity of glycogen synthetase was not correlated with glycogen concentration in muscle, but polychaetes most likely to experience anoxia had the highest proportion of the enzyme in the active (co-factor independent = I) form; moreover, in such species, the glycogen synthetase had the highest affinity for substrate. It was concluded that evolutionary adaptation to oxygen-poor habitats occurs through qualitative changes in enzyme properties rather than through quantitative changes in enzyme production.