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

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Abstract
Associations of larger Foraminifera with photoautotrophic partners, including representatives of the Bacillariophyceae, Dinophyceae and Rhodophyceae, were investigated for their photoassimilatory compounds using 14C-tracer techniques. Assimilate patterns are compared with appropriate features of free-living relatives. In the foraminifer-rhodophyte-association 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; relatively little 14C is found in soluble carbohydrates. In the foraminifer-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 C by release of algal assimilates rather than by digestion of their algal symbionts. The endosymbionts of Spirolina arietina were rhodophytes.