Laboratory Studies of the Ecological Significance of Host-Algal Nutritional Associations in Solitary and Colonial Radiolaria

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Abstract
Symbiont-bearing solitary and colonial radiolaria occur abundantly in diverse water masses throughout the major oceans of the world, including oligotrophic surface water (e.g. Strelkov & Reshetnyak, 1971; Casey, 1971, 1977; Anderson, 1983; Swanberg, 1979, 1983). Studies of their nutrition (Anderson, 1978, 1983; Swanberg, 1983) suggest that the algal symbionts may serve a substantial role in sustaining host nutrition. Our studies on the role of symbiotic algae in radiolaria have shown that Amphidinium-type, dinoflagellate symbionts (Anderson, 1983, p. 118) associated with the solitary species, Thalassicolla nucleata, and a colonial form Collosphaera sp. contribute photosynthetically-derived carbon to the host. The amount assimilated by T. nucleata is proportional to the primary productivity of the symbionts (Anderson, Swanberg & Bennett, 1983 b). Little is known, however, about the effects of environmental variables such as light intensity and quality on the primary productivity of the symbionts and the kinds of photosynthetic products accumulated within the host cytoplasm.