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Synechocystis didemni spec. nov. is described. It has only been found growing epizoically on calcified colonial ascidians (Didemnum spp.) in subtropical coastal waters. The apparent absence of phycobilin pigments and the presence of two chlorophylls (separable by chromatography) are unusual features for a photosynthetic prokaryont. So far, all attempts to culture this alga have been unsuccessful.
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Ralph A. Lewin (1975) studied this question.
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