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ABSTRACTMarine benthic dinoflagellates within the genus Amphidiniumwere isolated from Guam and Okinawa. Isolated strains were identified to species-level using phylogenetic analyses of 28S rRNA and ITS-5.8S rRNA genes as well as microscopy. Of the six isolated strains, two were new species: A. pagoense sp. nov. and A. uduigamense sp. nov. Other isolates included strains of A. massartiiand A. operculatumfrom Guam, and two strains of A. operculatumfrom Okinawa. Both new species were described using light and electron microscopy (SEM and TEM). The combination of characteristics that make A. pagoense sp. nov. unique includes a pair of centrally-located pyrenoids, variable cell shape, absence of scales and a long, curved ventral ridge. For A. uduigamense sp. nov., a combination of several morphological features distinguishes it from other species. These include a constriction near the anterior of the hypocone, two centrally located pyrenoids, a longitudinal flagellum inserted in the posterior one-third of the cell, cell size, cell division in the motile stage and the absence of scales. Toxicity was confirmed in these two novel species by testing methanol extracts in an Artemiabioassay. Previously unrecorded ITS rRNA gene sequences from A. operculatumwere also sequenced from both locations. Species identified and newly described in this study expand the taxonomic knowledge of Amphidiniumin the Pacific.

ABSTRACTThis study describes two novel parasitic dinoflagellates: Haplozoon gracile sp. nov. isolated from a bamboo worm (Maldanidae), ‘cf. Petaloclymenesp.’ sensuKobayashi et al. 2018; and, H. pugnus sp. nov. isolated from Nicomachesp. and Nicomache personata(Maldanidae). Trophonts (feeding stages) were observed with light, scanning, and transmission electron microscopy. Molecular phylogenetic analyses were performed based on 18S rDNA. COI sequences were obtained for host organisms. Trophonts of H. gracilewere linear (single longitudinal row) and relatively slender with a mean length of 190 μm, and consisted of a long and narrow trophocyte, rectangular gonocytes (mean width = 10 μm), and slightly rounded sporocytes. Trophonts of H. pugnuswere pectinate (1–8 rows of sporocytes in one plane), with a mean length of 179 μm, consisting of a bulbous trophocyte, rectangular gonocytes (mean width = 25 μm), and rounded sporocytes. The body of both species was covered with many depressions that overlaid the amphiesmal vesicles. TEM observations of trophocytes in H. gracilerevealed a stylet with a central dense core and rich mitochondria subtending the amphiesma. Furthermore, amphiesmal vesicles appeared to contain thecal plates in both species. Phylogenetic analyses generally resolved a Haplozoonclade, and H. gracileand H. pugnuswere clearly distinguished from other species for which molecular data are available. Based on the morphological and host comparisons with all described species and their molecular phylogeny, we conclude that these two isolates are new species of Haplozoon, H. gracile sp. nov. and H. pugnus sp. nov.

Abstract:We isolated Plagiodinium belizeanuminto 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. belizeanumwithin 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′′′ 0p 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.