The marine diatom Pseudo-nitzschia galaxiae sp nov (Bacillariophyceae):: morphology and phylogenetic relationships

A new marine planktonic diatom, Pseudo-nitzschia galaxiae Lundholm & Moestrup sp. nov., isolated from Mexican and Australian waters, is described using light and transmission electron microscopy, including thin-sectioning. The diatom is very small and delicate and resembles species in the section Nitzschiella of Nitzschia, as well as some Pseudo-nitzschia species. In phylogenetic analyses based on sequences of partial large subunit ribosomal DNA, P. galaxiae clusters firmly within a clade of Pseudo-nitzschia and Fragilariopsis species. The branching within the clade is not fully resolved, but closely related taxa comprise P. delicatissima, P. inflatula, P. micropora, P. pseudodelicatissima and P. cf. subpacifica. Analyses for domoic acid, the neurotoxin known from several other Pseudo-nitzschia species, were negative.