Mitsunori Iwataki

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

The armored dinoflagellate genus Heterocapsa is composed of relatively small species, including a species responsible for harmful red tides, H. circularisquama. Some Heterocapsa species such as H. rotundata and H. triquetra have been well documented as red tide-forming species, but are not recognized as causing harmful effects. Following sequential shellfish mass mortalities in the coastal waters of western Japan due to H. circularisquama red tides, this species has attracted considerable intere

Harmful algal blooms responsible for mass mortalities of marine organisms have been rare in Hokkaido, northern Japan, although fish-killing blooms have been frequently reported from western Japanese coasts. In September-November 2021, a huge and prolonged cold-water bloom occurred along the Pacific coast of eastern Hokkaido, and was associated with intensive mortalities of sea urchin, fish, octopus, shellfish, etc. In this study, morphology and phylogeny of the dominant and co-occurring unarmore

The external and internal ultrastructure of the harmful unarmored dinoflagellate Cochlodinium polykrikoides Margalef has been examined with special reference to the apical groove and three-dimensional structure of the flagellar apparatus. The apical groove is U-shaped and connected to the anterior sulcal extension on the dorsal side of the epicone. The eyespot is located dorsally and composed of two layers of globules situated within the chloroplast. A narrow invagination of the plasma membrane

:The morphology of two marine woloszynskioid dinoflagellates from the Japanese coast was examined by light, scanning and transmission electron microscopy, and phylogenetic positions were inferred on the basis of partial nuclear-encoded large-subunit ribosomal (r)DNA (D1–D3) sequences. Both species had a single elongate apical vesicle (EAV) on the anterior end, a diagnostic feature of the Suessiaceae, and were identified as Biecheleriopsis adriatica and an undescribed species of Biecheleria. Cell

The body scales of 12 Heterocapsa species including a new species, H. pseudotriquetra Iwataki, Gert Hansen & Fukuyo, sp. nov. were investigated by transmission electron microscopy to clarify ultrastructural differences. All species had scales with a body-scale structure consisting of a triradiate basal plate and a three-dimensional construction composed of vertically standing uprights or spines and horizontal bars. This basic scale structure is considered to be a generic characteristic. Finer sc

In all, 26 cultures of the harmful marine dinoflagellate Karlodinium , isolated from Japanese and Philippine coastal waters, were examined using LM, SEM, and molecular phylogeny inferred from ITS and LSU rDNA. Seven Karlodinium species (six from Japan and four from Philippines), K. australe , K. ballantinum , K. decipiens , K. gentienii , K. veneficum , K. zhouanum , and a novel species Karlodinium azanzae sp. nov., were identified based on their morphology and phylogenetic positions. Karlodiniu

Two new armoured dinoflagellate species, Heterocapsa ovata Iwataki & Fukuyo sp. nov. and Heterocapsa orientalis Iwataki, Botes & Fukuyo sp. nov., are described, and their body scale and cell morphology are illustrated using light, fluorescence, scanning electron and transmission electron microscopy. These species possess a thecal plate arrangement that is typical of the genus Heterocapsa: Po, cp, 5′, 3a, 7″, 6c, 5s, 5″′, 2″″; and they have triradiate three-dimensional body scales consisting of a

Heterocapsa lanceolata Iwataki & Fukuyo sp. nov. and H. horiguchii Iwataki, Takayama & Matsuoka sp. nov. are described from the coastal waters of Japan using light, fluorescence and electron microscopies. The thecal plate formula of the two species is: Po, cp, 5′, 3a, 7″, 6c, 5s, 5″′, 2″″. Both species possess three-dimensional body scales. These morphological features are characteristic of the genus Heterocapsa. Heterocapsa lanceolata does not resemble any other described Heterocapsa species, o