In some, cellulose is deposited between these membranes and forms rigid plates called thecae. When no thecae are present, the dinoflagellates are termed as naked. Chromosomes are always condensed in dinoflagellates. When the chromosomes of a cell are condensed, the cell is classified as dinokaryotic. The DNA is not associated with the histones as it is in other eukaryotic cells.
Dinoflagellates have a relatively large amount of DNA and a large nucleus.
The metabolic requirements to support a large amount of DNA probably account for the relatively low growth rates of these protists. Many dinoflagellates are photosynthetic and play a key role as producers in the food chains of the ocean. The luminescence of photosynthetic dinoflagelletes is very much influenced by the intensity of the previous days sunlight. The brighter the sunlight, the brighter the luminescence will be. Not all are photosynthetic, some are symbiotic- living in the cells of their hosts.