Features and Nutritional Significance of Photosynthates Produced by Unicellular Algae Symbiotic with Larger Foraminifera

Associations of larger Foraminifera with photoautotrophic partners -including representatives of the Bacillariophyceae, Dinophyceae, and Rhodophyceaehave been investigated for their photoassimilatory compounds using 14C-tracer techniques. Assimilate patterns are compared with appropriate features of free-living relatives. In the foraminifer-rhodophyteassociation free galactose and glycerol are found which are usually not present in non-symbiotic Rhodophyceae. In the foraminifer-dinoflagellate-association most of the radiocarbon is recovered from lipid compounds, whereas relatively little I4C is found in the soluble carbohydrates. In the foram~nifer-diatom-associations the amount of glucose and glycerol is relatively higher than in free-living diatoms. These differences may be interpreted as effects of the symbiotic condition. From the pattern of photoassimilatory products it is concluded that the animal cells receive organic carbon by release of algal assimilates rather than by digestion of their algal symbionts. The endosymbionts of Spiroljna arietina were shown to be Rhodophytes.