Gymnodinium

Genus of marine dinoflagellates that includes the unicellular organism that causes red tide.

- G. breve a species of microscopic algae that causes red tide; it produces a toxin that affects the central nervous system of fish, paralyzing and killing them.

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Gym·no·din·i·um .jim-nə-'din-ē-əm n a large genus (the type of the family Gymnodiniidae) of marine and freshwater naked dinoflagellates that includes forms which are colorless or tinted yellowish to reddish brown, blue, or green by chromatophores and a few forms which cause red tide

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Gym·no·din·i·um (jim″no-dinґe-əm) [gymno- + Gr. dinein to whirl] a genus of plantlike marine and freshwater protozoa of the phylum Dinoflagellata; most species have many colored (yellow, brown, green, or blue) chromatophores. Like other dinoflagellates, they produce red tide when present in vast numbers. G. breve has been renamed Karenia brevis.