FTP, name this division of occasionally toxic protists which are the cause of red tides.
The largest known example in this division, Noctiluca, can reach 2 millimeters across. Their nuclear structure is unusual, as they can have up to 400 chromosomes, which are attached to the nuclear membrane and remain condensed except for DNA replication.  Some types of corals engage in symbiosis with the Zooxanthella type, and the light-producing species are responsible for much of the phosphorescence seen in ocean water at night.  Each has two of the feature that they are named for, one of which wraps around the cell and the other of which beats back and forth to propel it. FTP, name this division of occasionally toxic protists which are the cause of red tides.
The largest known example in this division, Noctiluca, can reach 2 millimeters across.
dinoflagellates or pyrrophyta or pyrrophytes