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Dinoflagellata(dī″nō-flaj″ĕ-lā′tă) [Gr. deinos, fearsome, awesome + flagellate]
A phylum of the kingdom Protista comprising photosynthetic unicellular organisms that are part of the phytoplankton in fresh and ocean water. Some marine species bloom explosively in red tides. Shellfish that feed on the dinoflagellates are toxic to humans (causing paralytic shellfish poisoning). Another species produces ciguatera toxin, which is poisonous to fish and to humans who consume such fish.