This genus is representative of an order in which cells have no walls. The cells have a transverse furrow and a short longitudinal sulcus. Chloroplasts are numerous and usually golden-brown oval discs. There are both salt and fresh water species. Several species are known to produce a letal toxin and are responsible for the death of fish (Red Tide) which occurs periodically along continental shelves.
The diagram to the left is a Gymnodinium species that contains many chloroplasts.
This species well illustrates the flagella of Gymnodinium. One flagellum is elongate, usually extending posteriorly with reference to the direction of motion. The second flagellum, which emerges from the same point as the first, is ribbonlike and lies in a transverse groove in which it undergoes undulating movement.
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