As a result of the action of the two flagella the cell spirals as it moves. Many are covered by cellulose plates. The cell is surrounding by a series of membranes called the amphiesma. Their chromosomes are always condensed. In addition, the DNA is not associated with histones as in other eukaryotic cells.
Dinoflagellates contain a lot of DNA, which explains the large size of the nucleus.
The metabolic requirements of supporting the large amount of DNA may explain the low growth rates of dinoflagellates compared to other unicellular protists. Not all dinoflagellates are photosynthetic. Many dinoflagellates are photosynthetic, manufacturing their own food using the energy from sunlight, and providing a food source for other organisms. The photosynthetic dinoflagellates are important primary producers in coastal waters. Some photosynthetic dinoflagellates are symbiotic, living in the cells of their hosts, such as corals.