A new genus of athecate interstitial dinoflagellates,Togulagen. nov., previously encompassed withinAmphidinium sensulato: Inferred from light and electron microscopy and phylogenetic analyses of partial large subunit ribosomal DNA sequences.

The recent emendation ofAmphidinium(Dinophyceae), which now only consists of species with minute left-deflected epicone, has left more than 100 species without a clear generic affiliation. In the present study, a strain identified as one of the species with a divergent epicone type,Amphidinium britannicum(Herdman) Lebour, and six strains resemblingA. britannicumbut smaller in size were examined by light, scanning and transmission electron microscopy and by sequence analyses of nuclear-encoded partial large subunit ribosomal DNA to establish their phylogeny.Amphidinium britannicumwas not closely related to other genera included in the molecular phylogenetic analyses, but formed a highly supported clade in Bayesian analysis together with the six small-sized strains. The six strains also formed a highly supported clade, consisting of two closely related, albeit distinct, clades. Light and scanning electron microscopy did not reveal significant differences between the vegetative motile cells; however, cells about to undergo mitosis developed longitudinal grooves on the hypocone in one of the clades but not in the other. Both clades differed substantially fromA. britannicumin partial large subunit ribosomal DNA as well as in size and shape. Based on morphological similarity and partial large subunit ribosomal DNA evidence, we erect the new genus,Togulagen. nov. with the emended type speciesTogula britannica(Herdman) comb. nov. Based on differences in division pattern and partial large subunit ribosomal DNA gene divergence we further describe the speciesTogula compacta(Herdman) comb. nov. andTogula jollasp. nov. [ABSTRACT FROM AUTHOR]