Evolution and origin of the chemical composition of radiolarian test during geologic time scale

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Reproductive swarmers of the polycystine radiolarians were examined using light, scanning and transmission electron microscopy. The swarmer cells were about 8um in length with a pear-like shape and a conical end with two flagella. Lipid droplets and characteristically a vacuole-bound SrSO4 crystal were present in the cytoplasm. The morphological features and molecular phylogeny of the reproductive swarmers show evidence of ancestral traits of radiolarians; acantharians and polycystines have a common ancestry. Symbiotic dinoflagellate isolated from polycystine radiolarians was described using both natural and cultured materials. Motile cells were obtained in culture showed unarmored nature and the characteristics suggested it as Gymnodinium. Our results suggest that at least two dinoflagellate symbiont species existed in the radiolarians and they have been possibly reported as "Zooxanthella nutricula" since the 19th century.