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Cabra is a genus of marine heterotrophic thecate dinoflagellates with a peculiar cell shape and thecal plate tabulation. Previous studies suggested it was related to the benthic genus Roscoffia based on morphological features. A previous molecular phylogenetic study using 18S rDNA showed that Roscoffia capitata and members of the family Podolampadaceae formed a well-supported monophyletic group; however, the classification of Cabra remains uncertain. In this study, the first molecular phylogenetic analysis based on 18S rDNA sequence for the genus was performed using specimens of Cabra matta collected in Okinawa, Japan. Molecular phylogeny showed that C. matta formed a clade with R. capitata and the planktonic oceanic members of Podolampadaceae including Podolampas spp. and Blepharocysta sp. This result supported previous studies that inferred the close affinity between Cabra, podolampadaceans and R. capitata based on a very narrow and long 1′ plate, and the diminutive 2′ and 3′ plates, the larger precingular plates, smaller apical plates, the presence of three cingular plates, the hypothecal plate pattern of five postcingular plates and one antapical plate. In contrast, there are clear morphological differences between the planktonic podolampadaceans and the benthic genera Roscoffia and Cabra: the planktonic members have a cryptic cingulum and lack an apparent sulcus, while the benthic members have an apparent cingulum and sulcus. Molecular phylogeny in the present study did not resolve the evolutionary branching order for Cabra, Roscoffia, Podolampas and Blepharocysta. [ABSTRACT FROM AUTHOR]

We isolated Plagiodinium belizeanum into clonal culture from the Pacific island of Okinawa (Japan) and characterized it using a combination of light microscopy, scanning electron microscopy, transmission electron microscopy and 18S/28S ribosomal (r) gene sequences. Although molecular phylogenetic analyses of 18S rDNA and 28S rDNA sequences were unable to resolve the phylogenetic position of P. belizeanum within dinoflagellates, the ultrastructural data provided some new traits for the species. For instance, double-membrane-bound vesicles, distinct from the mitochondria, were interpreted as autolysosomes containing electron-dense virus particles. The thecal plate pattern was Po 1' 0a 5''5(6)C 4S 5'p 1', which is slightly different from the original description in having an additional epithecal plate and four sulcal plates. The laterally flattened cells were 22-34 μm long, 11-13 μm deep, and 15-18 μm wide and contained a peridinin-type plastid with lobes radiating from a central pyrenoid that lacked starch sheaths and was traversed by stacks of thylakoids. This isolate represents the first record of the species in Japan, and the new ultrastructural and DNA sequence data were used to emend the species description. [ABSTRACT FROM AUTHOR]