A comparative study between Prorocentrum shikokuense and P. donghaiense (Prorocentrales, Dinophyceae) based on morphology and DNA sequences

The taxonomic position of an armored dinoflagellate Prorocentrum donghaiense Lu, 2001, which is one of the causative species of large red tides occurring off Changjiang River mouth was examined and compared to a similar species P. shikokuense. In both species, the following morphological features were shared; a weakly concave cell with a tiny apical spine around the periflagellar area, one side of the cell being slightly extended on the anterior end, a rounded posterior end, a rounded nucleus located in the posterior region and similar size of cells. DNA sequences of small subunit rDNA and internal transcribed spacer 1 (ITS1)-5.8S rDNA-ITS2 regions of these two species were largely the same. Morphological and molecular data suggest that P. donghaiense and P. shikokuense are synonymous and P. shikokuense has priority over P. donghaiense