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Cyst–theca relationships of the common armored dinoflagellate Protoperidinium oblongum were re-investigated by incubation experiments and molecular phylogenetic analysis. Living cysts provided for incubation experiments were collected from several places in Japan, including Omura Bay, West Japan and Lake Saroma in Hokkaido, North Japan. One hundred and four cysts were incubated and 18 motile cells were germinated from these cysts. To clarify their morphological characteristics both cysts and germinated thecate cells were observed, especially the archeopyle type, the number and shape of anterior intercalary plates, and the shape and development of apical and antapical horns. In order to provide molecular phylogenetic analysis, germinated cells from incubated cysts were examined for their LSU rDNA sequences. Results reveal that three morphologically different cysts produced three morphologically different thecate cells, which were previously known as Protoperidinium oblongum var. latidorsale, Protoperidinium oblongum var. inaequale, and Protoperidinium oblongum var. symmetricum. The molecular phylogenetic analysis demonstrated that the Oceania group in the genus Protoperidinium includes these three varieties as well as Protoperidinium divergens, Protoperidinium claudicans, and Protoperidinium steigingerae. This group is separated from Protoperidinium sensu stricto, and the three plankton forms are phylogenetically separate and independent species. Based on these facts, two new species, Protoperidinium quadrioblongum Sarai, Kawami et Matsuoka, the new name for Protoperidinium oblongum var. symmetricum and Protoperidinium paraoblongum Sarai, Kawami et Matsuoka for Protoperidinium oblongum var. inaequale are described.

In this paper we describe a new species, Archaeperidinium saanichi sp. nov. within the Archaeperidinium minutum Jörgensen 1912 species complex. We examined the morphological variation of the cyst and motile stage by incubation experiments from sediment samples collected in coastal British Columbia (Canada), and compared it to closely related species. The theca of A. saanichi is differentiated from related species by overall size, the asymmetry of the intercalary plates and the right-sulcal plate (S.d.) not touching the cingulum. We provide a key to differentiate all closely related species. A. saanichi can be readily distinguished from A. minutum by a distinctively large cyst with a broad 2a type archeopyle and regularly spaced processes with relatively broad bases and aculeate process tips. Molecular phylogenetic analyses of large and small subunit (LSU and SSU) rDNA sequences demonstrated a close affinity of this species to A. minutum; however, the relatively high level of sequence conservation in dinoflagellate rDNA sequences made these particular markers inadequate for distinguishing one species from the other. Sediment-trap data suggest that A. saanichi has a preference for cooler temperatures and lowered salinities.

Organic-walled resting cysts of Protoperidinium parthenopes Zingone & Montresor 1988 were collected from a sediment trap in Omura Bay, western Japan. The cysts are spherical and pale brown in color. The cyst wall has two layers: a thick endophragm with granulate surface, and a thin periphragm. Three complete and incomplete parasutures appear on the surface of the endocyst. The archeopyle formed on the endocyst is basically saphopylic and compound with some combination of complete and incomplete parasutures. The cyst of Protoperidinium parthenopes closely resembles the cyst of Protoperidinium americanum (Gran & Braarud 1935) Balech 1974, but differs in the shape of the periphragm, the cyst diameter, and in the archeopyle.

In Gamak Bay, Paralytic Shellfish Poisoning (PSP) was first detected from seafoods in 2003, however the toxin source is unknown yet. In this study, we report potential PSP producers of toxic dinoflagellates, describing morphology and abundance of cysts isolated from surface sediment of Gamak Bay. The most abundant type in these cysts was characterized with ellipsoidal and transparent wall identical to Alexandrium catenella and/or A. tamarense. Germination experiment of the cysts revealed that all motile cells germinated were morphologically identified as A. tamarense. This result suggests that A. tamarense may relate to PSP contaminations in Gamak Bay. Moreover, bottom water temperature in Gamak Bay is favorable for germination of A. tamarense cysts. Further studies are required to carry out the PSP monitoring for preventing the risk of PSP events that may outbreak in future at Gamak Bay.

The morphology of an unarmored chain-forming harmful dinoflagellate Cochlodinium polykrikoides and its similar species such as Cochlodinium catenatum, Cochlodinium fulvescens, and Cochlodinium convolutum was carefully observed, emphasizing the single cell stage for clarifying taxonomically important morphological features. To differentiate C. polykrikoides from C. convolutum, the shape and the position of the nucleus are useful characters. C. polykrikoides also differs from C. fulvescens in being smaller in size, possessing many rod-shaped chloroplasts and having the sulcus running just below the cingulum on the dorsal surface. Careful observation of the ichnotype of C. catenatum suggests that C. catenatum sensu Kofoid and Swezy collected from off La Jolla, CA, USA, is not identical to C. catenatum sensu Okamura and is probably a different species, in having no chloroplasts and a nucleus positioned at the center of the cell. In addition, C. polykrikoides has many morphological features in common with C. catenatum sensu Okamura except for slightly elongate cells and is probably a junior synonym of this species., Harmful Algae, 7(3), pp.261-270; 2008

SUMMARY Cellular morphology and the phylogenetic position of a new unarmored photosynthetic dinoflagellate Cochlodinium fulvescens Iwataki, Kawami et Matsuoka sp. nov. were examined by light microscopy and molecular phylogenetic analyses based on partial large subunit ribosomal DNA (LSU rDNA) and small subunit ribosomal DNA (SSU rDNA) sequences. The cells of C. fulvescens closely resemble C. polykrikoides, one of the most harmful red tide forming dinoflagellates, due to it possessing a cingulum encircling the cell approximately twice, a spherical nucleus positioned in the anterior part of the cell and an eyespot-like orange pigmented body located in the dorsal side of the epicone, as well as formation of cell-chains. However, this species is clearly distinguished from C. polykrikoides based on several morphological characteristics, namely, cell size, shape of chloroplasts and the position of narrow sulcus situated in the cell surface. The sulcus of C. fulvescens is located at the intermediate position of the cingulum in the dorsal side, whereas that of C. polykrikoides is situated immediately beneath the cingulum. LSU rDNA phylogenies indicated that C. fulvescens is clearly distinct from, but closely related to C. polykrikoides among dinoflagellates.

Oblea acanthocysta of the diplopsalid group is described as a new species from Omura Bay, West Japan. The motile cells are subspherical, have a large sulcal list at the left margin, and are characterized by the plate formula, Po, X, 3′, 1a, 6″, 3c+t, 6s?, 5?, 2″″. The species resembles Oblea torta in shape and plate distribution, but is smaller and differs in the shape of plate 1′ and position of plate 1a. Resting cysts of O. acanthocysta are spherical and pale brown in color, possess many hollow acuminate spines, and have a theropylic archeopyle. In the SSU rRNA gene sequences of three cells of O. acanthocysta and two cells of O. torta, no intraspecific base substitutions were detected within either species. Based on phylogenetic analyses, the O. acanthocysta clade is included in the diplopsalids clade together with other diplopsalid species such as O. torta, Diplopsalis lebourae, Diplopsalopsis bomba and Gotoius excentricus. The sequences of O. acanthocysta are different from those of O. torta in 154 base pair substitutions, but O. acanthocysta and O. torta have a very close phylogenetic relationship., Plankton and Benthos Research, 1(4), pp.183-190; 2006