Unarmoured and thin-walled dinoflagellates from the Gulf of Naples, with the description of Woloszynskia cincta sp. nov. (Dinophyceae, Suessiales).

The unarmoured dinoflagellate assemblage of the Gulf of Naples has been investigated in the frame of a 1-year sampling of natural surface samples collected weekly at a coastal station c. 2 miles offshore. Twenty-six strains of unarmoured dinoflagellates were brought into culture by means of serial dilution. Observations at both light and scanning electron microscopy (SEM) together with molecular phylogenetic analyses allowed identification of eight dinoflagellate species. Gymodinium aureolum, Karlodinium veneficum, Protodinium simplex and Takayama acrotrocha were previously reported in the Mediterranean; whereas, Karlodinium ballantinum and Lepidodinium viride together with a taxon identified as Karenia cf. longicanalis are recorded in the basin for the first time. A new thin-walled dinoflagellate is described as Woloszynskia cincta sp. nov. on the basis of morphological results. Molecular analysis showed that Woloszynskia cincta is closely related to W. halophila and W. pseudopalustris and only distantly related to W. pascheri. In Protodinium simplex, a straight acrobase and an arrangement of the amphiesmal vesicles in latitudinal series were revealed by SEM observations, demonstrating the relatedness of this species with woloszynskioid dinoflagellates. Based on new morphological information on Karlodinium species, Gyrodinium corsicum is transferred to Karlodinium corsicum. New morphological features are identified for the recognition of Takayama acrotrocha, such as the arrangement of the acrobase and the presence of a pore on the ventral side of the cell. The latter species was found to be genetically distinct from other species in the genus Takayama, which is monophyletic. [ABSTRACT FROM AUTHOR]