The Alexandrium tamarense species complex in Kuwait’s waters (Arabian/Persian Gulf, northern Indian Ocean) with the description of Alexandrium arabiense sp. nov

Morphological observations of the Alexandrium tamarense (Dinophyceae) species complex in Kuwait’s waters (Arabian/Persian Gulf, northern Indian Ocean) discerned four morphotypes, of which three corresponded to A. catenella, A. pacificum, and A. tamarense. One Alexandrium morphotype differed in morphology from all previously reported species belonging to the A. tamarense complex and was genetically distinct. Morphologically, it was characterized by a 1ʹ plate without a ventral pore, a lack of anterior and posterior attachment pores in apical pore plate and posterior sulcal plate, and a lack of long chain formation. The thecal surface was perforated by pores of two size classes. Phylogenetic analyses inferred from 18S, ITS/5.8S, and partial 28S nuclear rDNA gene sequences revealed strains of the new morphotype from Kuwait’s waters to appear as sisters to A. pacificum with high support. Based on a unique combination of morphological and molecular features, a new member of the A. tamarense complex, Alexandrium arabiense sp. nov., is described. The holotype strain of A. arabiense was tested for paralytic shellfish poisoning activity and found to be positive by ELISA assay, but negative by ion pair chromatography coupled to post-column derivatization and fluorescence detection. The strain was also tested for other toxins known to be produced by the genus Alexandrium, such as gymnodimines, spirolides, and goniodomins, but none of them were detected. The observed morphological diversity within the A. tamarense complex in Kuwait’s waters thus requires a further close examination of this potentially PSP-causing species group, primarily molecular and toxicological analyses.