Prorocentrum shikokuense Hada and P. donghaiense Lu are the synonym of P. obtusidens Schiller (Prorocentrales, Dinophyceae)

Abstract

In Japanese, Chinese and Korean coastal waters, a small thecate Prorocentrium species has been recognized as the bloom forming species . However, the species has been called as Prorocentrum shikokuense, P. donghaiense and P . dentatum, respectively, despite their morphological similarity and identical rDNA sequences . To resolve the confusion, we examined the morphological features including architectural details of the periflagellar area and molecular phylogeny of the isolates collected from East China Sea and Korean coast, and reviewed the taxonomic descriptions of the confused spec ies and the related species and its historical records. Morphology and phylogeny based on SSU, ITS region and LSU rDNA sequences revealed that the confused species and our isolates are conspecific and morphological features of P. dentatum recorded in the phylogenetic trees does not coincide with those of the originally described P. dentatum. Dodge (1975) included P. velo1~ P. monacens and P. obtusidens to P. dentatum as sy nonyms, however the literature review revealed that the morphological features of his specimens were closer to those of P. obtusidens in the original description, rather than thoseof originally descri bed P. dentatum and that P. obtusidens is distinguished from P. dentatum by relati vely small size, the parallel sides toward the anterior, blunt anterior extension on one side and probably location of nucleus. This ind