Taxonomic and ecological study of PSP causative small Alexandrium

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Morphology of species belonging to the genus Alexandrium were observed in details, including several toxic ones that cause paralytic shellfish poisoning (PSP). Plankton samples collected from many areas in the world were used for the study as well as cultures maintained in several culture collections. Efforts were made to collect samples at the type locality of each species, in order to increase taxonomic accuracy.These results obtained were ;1. Totally 22 species, which were previously described in taxonomic articles, were observed. They are : A.acatenella, A.affine, A.andersonii, A.catenella, A.compressum, A.concavum, A.fraterculus, A.fundyense, A.hiranoi, A.insuetum, A.leei, A.lusitanicum, A.margalefii, A.minutum, A.monilatum, A.ostenfeldii, A.peruvianum, A.pseudogonyaulax, A.satoanum, A.tamarense, A.tamiyavanichii, A.taylorii, and A.tropicale. These species were carefully observed and described again in the report with photographs. Several species were compared with specimens collected at the type locality for taxonomic discussion.2. Several taxonomically undescribed morphotypes were also collected and observed.3., Sixteen described species among the 22 species, and two undescribed morphotypes were occurred in Japanese coastal waters, .4. Three species, A.andersonii, A.minutum and A.ostenfeldii, which are known to cause PSP in some countries outside Japan, were found in Japanese waters for the first time in this study. Monitoring on the occurrence of the three species is inevitable as well as three species that already recognized as PSP causative species in Japan A.catenella, A.tamarense and A.tamiyavanichii.5. Though the toxicity of culture strains established in the present study were analyzed, any new toxic species has not been found.