An edited transcript is presented for discussions on more than 24 taxa of Neogene and Quaternary ... more An edited transcript is presented for discussions on more than 24 taxa of Neogene and Quaternary dinoflagellates, chosen either as being in some way taxonomically problematical or because they hold unusual interest concerning their morphology, (paleo)ecology, or biostratigraphy. These discussions took place at the Third Workshop on Neogene and Quaternary Dinoflagellates and are based on observations of numerous holotypes and
In situ emergence of the centric diatoms from the surface sediment, along with the occurrence of ... more In situ emergence of the centric diatoms from the surface sediment, along with the occurrence of the vegetative cells in the water column, were monitored monthly in a shallow embayment, Ago Bay, of central Japan, where light penetrated to the seafloor. The in situ emergence flux (cells m-2 day-1) was measured by experiments using a ‘plankton emergence trap/chamber (PET chamber)’. During the study period from July 2006 to May 2008, germinating and rejuvenating cells of centric diatoms were successfully collected by the PET chamber. Furthermore, vegetative cells forming long-chain colonies, including the species which have not been known to form resting stage cells, were also found, indicating that these cells already inhabited the surface sediment prior to the start of the PET chamber experiments. The vegetative cells could be cells that grew after germination/rejuvenation and/or cells deposited from the upper layer in the water column. When comparing emergence flux in the PET chambe...
Harmful algal blooms (HABs) caused by an unknown dinoflagellate species have frequently occurred ... more Harmful algal blooms (HABs) caused by an unknown dinoflagellate species have frequently occurred in the Pearl River Estuary, China Since 2006. These blooms were associated with severe water discoloration and economic losses, ranging from several km2 to 300 km2 with the maximum recorded cell density being 2.77 × 107 cells⋅L-1. This unknown dinoflagellate species was initially identified as Cochlodinium geminatum and subsequently reclassified as Polykrikos geminatus. However, after reviewing the original descriptions for Cochlodinium geminatum sensu Schütt (1895) and the genus Polykrikos, we considered this species is incongruent with their original descriptions. Further morphological examinations and particularly phylogenetic analyses based on the SSU and partial LSU rRNA genes of isolates and resting cysts from China and Japan prompted us to consider it a new species of a new genus. This new species was proposed to be Pseudocochlodinium profundisulcus gen. et sp. nov., based on its open comma-shaped apical structure complex (ASC), cingulum encircling the cell less than one and a half turns, a deep sulcus with a torsion of a half turn, either single cell or cell chain consisting of two cells with the same number of nuclei and zooids, the resting cyst bearing lobed ornaments, and the evolutionary distances from Polykrikos (and others) on the phylogenetic trees constructed using the concatenated SSU and partial LSU rRNA gene sequences. Metabarcoding investigation of surface sediment samples collected in China revealed that the species to be widely present along the entire Chinese coast with the highest abundance in the South China Sea. Further re-analysis of the Tara Oceans metabarcoding dataset targeting the SSU rRNA gene V9 domain suggested a global distribution of this new genus. Phylogenetic analyses on 46 OTUs (average length: ∼552 bases) of its LSU rRNA gene sequences (mainly D1-D2 domains) obtained from surface sediment samples revealed intraspecific genetic diversity of this species. Interestingly, based on the different distributions and the abundance of these OTUs along the coast of China, this species appeared to have expanded its distribution from the South China Sea to the northern Yellow Sea, or preferred a warm water habitat. We consider that the present work improves the taxonomy and provides important insights into the biogeography of Pseudocochlodinium profundisulcus.⋅.
Although the life cycle of Margalefidinium polykrikoides, formerly called Cochlodinium polykrikoi... more Although the life cycle of Margalefidinium polykrikoides, formerly called Cochlodinium polykrikoides, has been described previously, the descriptions on asexual and sexual phases of this species collected from Korean coastal waters are strange and still unclear. We collected the resting cysts of M. polykrikoides from surface sediments and re-examined the germination process, and asexual and sexual life stages, and the mating behavior of the vegetative cells using a microscope equipped with high-resolution time-lapse digital camera. The resting cyst of M. polykrikoides had a distinct germination process; before germination, a mature cell in shape was visible within the resting cyst body, and the cell quickly emerged from the resting cyst. The asexual reproduction and cell chain formation of M. polykrikoides were generated in a slightly oblique direction at the epicone of cell and the chain-forming cells of M. polykrikoides could form the chain-forming temporary cysts without asexual or sexual reproduction. The planozygote produced by gamete fusion of M. polykrikoides may not necessarily develop to resting cysts but instead may divide into vegetative cells occasionally. In this phase, the armored cell, which was previously recorded by Kim et al. (2007), was not observed. The sexuality of M. polykrikoides had a homothallic mating behavior.
Stratigraphic cluster analysis using aquatic palynomorphs preserved in the core sediments reveale... more Stratigraphic cluster analysis using aquatic palynomorphs preserved in the core sediments revealed a rapid eutrophication due to anthropogenic activities from the mid 1960s in Beppu Bay, East Kyushu, Japan. These assemblages were divided into three major units: BP-I, BP-II and BP-III, and also only dinoflagellate cyst assemblages were divided into the following four units in Beppu Bay: BP-A, BP-B, BP-C, and BP-D. Unit boundaries based on aquatic palynomorphs and dinoflagellate cysts were different except in the upper part, BP-III and BP-D, both of which clearly indicated anthropogenic eutrophication in both sea water and bottom sediments. On the other hand, in dinoflagellate cyst assemblages, Unit BP-A was characterized by stable occurrence of Spiniferites bulloideus and Spiniferites hyperacanthus, Lingulodinium machaerophorum of Gonyaulacales, and reduction of heterotrophic Peridinioid Brigantedinium spp. In Unit BP-C there was a clear decrease of L. machaerophorum. Unit BP-B was c...
SUMMARYCellular and body scale structure of a new armored dinoflagellate Heterocapsa huensis, col... more SUMMARYCellular and body scale structure of a new armored dinoflagellate Heterocapsa huensis, collected from Hue, Vietnam were investigated. Morphology of motile cell was observed by light, fluorescent and scanning electron microscopy, and body scale structure was examined by whole mounts of transmission electron microscopy. Cells of H. huensis were ellipsoid with a spherical nucleus located in the posterior and multiple pyrenoids located above the nucleus; this arrangement was similar to that of Heterocapsa pygmaea. Transmission electron microscopy revealed ultrastructure of the body scales consisted of a rounded triangular basal plate and three‐dimensional ornaments. Structure of the basal plate resembles that of Heterocapsa illdefina; however, the number of the peripheral spine is different from that of H. illdefina and this structure has never been reported from Heterocapsa species. A new Heterocapsa species, H. huensis Iwataki et Matsuoka sp. nov., is described based on positions of organelles and body scale ultrastructure.
SUMMARYThe lateral variation of sediment properties and associated cyst content of sediment in Ma... more SUMMARYThe lateral variation of sediment properties and associated cyst content of sediment in Manila Bay were determined and their possible role/s in the occurrences of Pyrodinium bahamense Plate var. compressum (Bohm) Steidinger, Tester et Taylor toxic blooms were assessed. Manila Bay's surface sediment was determined to be silt dominated. Clay generally increased towards the coast, probably as a result of flocculation and rapid deposition upon entry of sediments from the rivers. High sand content characterized the southeastern part of the bay attributed to the greater sand inputs and relatively strong currents in this area. Bulk densities were lower in the eastern side of the bay from dilution by high organic load from sewage and urban areas. Benthic flux calculations, particularly NH3, suggest more than 50% nutrient contribution comes from sediments.In general, dinoflagellate cyst density increased from the center of the bay towards the coast, except in Pampanga Bay where it deceased near the coasts. A maximum of 23 dinoflagellate species were identified: 5 were autotrophic (Lingulodinium polyedrum (Stein) Dodge, Gonyaulax spp., Pyrophacus steinii (Schiller) Wall et Dale, Protoceratium reticulatum (Claparede et Lachmann) Butschli, and Pyrodinium bahamense var. compressum), and the rest were predominantly composed of Protoperidinium spp. and Diplopsalis spp. Heterotrophs comprised about 70% of the total cyst counts. Pyrodinium counts increased towards the northwestern part of the bay where it was the dominant autotroph species. Negative correlations were observed for live Pyrodinium cyst density and N flux, P flux, ratio of N to P and total organic carbon (TOC) content. However, areas with high N:P ratio contain abundant Pyrodinium live cysts.
ABSTRACT We propose a standardization of the gonyaulacalean (Dinophyceae) Kofoidian plate tabulat... more ABSTRACT We propose a standardization of the gonyaulacalean (Dinophyceae) Kofoidian plate tabulation using plate homology and overlap patterns, on the basis of a new morphological study of species belonging to 17 genera previously classified in the order Gonyaulacales: Acanthogonyaulax, Alexandrium, Amphidoma, Azadinium, Ceratium, Ceratocorys, Cladopyxis, Cribroperidinium, Fragilidium, Gonyaulax, Heterodinium, Lingulodinium, Paleophalacroma, Peridiniella, Spiraulax, Triadinium and Tripos. The plate immediately left of the flagellar pore is reinterpreted as a sulcal plate rather than its more conventional interpretation as a postcingular plate. With this new perspective the studied genera fall into two groups: 1) genera with only five Kofoidian postcingular plates (Acanthogonyaulax, Alexandrium, Ceratocorys, Cribroperidinium, Gonyaulax, Lingulodinium, Spiraulax and Triadinium) or six postcingular plates (Fragilidium); 2) genera with six Kofoidian postcingular plates, as well as differences in episomal plate patterns (Amphidoma, Azadinium, Cladopyxis, Heterodinium, Paleophalacroma and Peridiniella). The former are here considered true gonyaulacaleans, whilst the latter need further study for a more appropriate phylogenetic placement, and are here informally called non-gonyaulacaleans. In these non-gonyaulacalean genera, the first posterior intercalary plate overlaps the first postcingular plate/anterior left sulcal plate, but is always overlapped by the second postcingular homologue plate (a plate in similar position) demonstrating that the first plate of the postcingular series is not homologous in the two groups. Additionally, the identical overlapping pattern shows that the anterior left sulcal plate (Ssa) in gonyaulacaleans with five postcingular plates is the same plate as the first postcingular plate in gonyaulacaleans with six postcingular plates. Kofoidian definitions of posterior intercalary plates as well as antapical plates remain the same and are applied here. The Kofoidian hyposomal plate formula for gonyaulacaleans would then be 5–6''', 2p, 1''''.
An edited transcript is presented for discussions on more than 24 taxa of Neogene and Quaternary ... more An edited transcript is presented for discussions on more than 24 taxa of Neogene and Quaternary dinoflagellates, chosen either as being in some way taxonomically problematical or because they hold unusual interest concerning their morphology, (paleo)ecology, or biostratigraphy. These discussions took place at the Third Workshop on Neogene and Quaternary Dinoflagellates and are based on observations of numerous holotypes and
In situ emergence of the centric diatoms from the surface sediment, along with the occurrence of ... more In situ emergence of the centric diatoms from the surface sediment, along with the occurrence of the vegetative cells in the water column, were monitored monthly in a shallow embayment, Ago Bay, of central Japan, where light penetrated to the seafloor. The in situ emergence flux (cells m-2 day-1) was measured by experiments using a ‘plankton emergence trap/chamber (PET chamber)’. During the study period from July 2006 to May 2008, germinating and rejuvenating cells of centric diatoms were successfully collected by the PET chamber. Furthermore, vegetative cells forming long-chain colonies, including the species which have not been known to form resting stage cells, were also found, indicating that these cells already inhabited the surface sediment prior to the start of the PET chamber experiments. The vegetative cells could be cells that grew after germination/rejuvenation and/or cells deposited from the upper layer in the water column. When comparing emergence flux in the PET chambe...
Harmful algal blooms (HABs) caused by an unknown dinoflagellate species have frequently occurred ... more Harmful algal blooms (HABs) caused by an unknown dinoflagellate species have frequently occurred in the Pearl River Estuary, China Since 2006. These blooms were associated with severe water discoloration and economic losses, ranging from several km2 to 300 km2 with the maximum recorded cell density being 2.77 × 107 cells⋅L-1. This unknown dinoflagellate species was initially identified as Cochlodinium geminatum and subsequently reclassified as Polykrikos geminatus. However, after reviewing the original descriptions for Cochlodinium geminatum sensu Schütt (1895) and the genus Polykrikos, we considered this species is incongruent with their original descriptions. Further morphological examinations and particularly phylogenetic analyses based on the SSU and partial LSU rRNA genes of isolates and resting cysts from China and Japan prompted us to consider it a new species of a new genus. This new species was proposed to be Pseudocochlodinium profundisulcus gen. et sp. nov., based on its open comma-shaped apical structure complex (ASC), cingulum encircling the cell less than one and a half turns, a deep sulcus with a torsion of a half turn, either single cell or cell chain consisting of two cells with the same number of nuclei and zooids, the resting cyst bearing lobed ornaments, and the evolutionary distances from Polykrikos (and others) on the phylogenetic trees constructed using the concatenated SSU and partial LSU rRNA gene sequences. Metabarcoding investigation of surface sediment samples collected in China revealed that the species to be widely present along the entire Chinese coast with the highest abundance in the South China Sea. Further re-analysis of the Tara Oceans metabarcoding dataset targeting the SSU rRNA gene V9 domain suggested a global distribution of this new genus. Phylogenetic analyses on 46 OTUs (average length: ∼552 bases) of its LSU rRNA gene sequences (mainly D1-D2 domains) obtained from surface sediment samples revealed intraspecific genetic diversity of this species. Interestingly, based on the different distributions and the abundance of these OTUs along the coast of China, this species appeared to have expanded its distribution from the South China Sea to the northern Yellow Sea, or preferred a warm water habitat. We consider that the present work improves the taxonomy and provides important insights into the biogeography of Pseudocochlodinium profundisulcus.⋅.
Although the life cycle of Margalefidinium polykrikoides, formerly called Cochlodinium polykrikoi... more Although the life cycle of Margalefidinium polykrikoides, formerly called Cochlodinium polykrikoides, has been described previously, the descriptions on asexual and sexual phases of this species collected from Korean coastal waters are strange and still unclear. We collected the resting cysts of M. polykrikoides from surface sediments and re-examined the germination process, and asexual and sexual life stages, and the mating behavior of the vegetative cells using a microscope equipped with high-resolution time-lapse digital camera. The resting cyst of M. polykrikoides had a distinct germination process; before germination, a mature cell in shape was visible within the resting cyst body, and the cell quickly emerged from the resting cyst. The asexual reproduction and cell chain formation of M. polykrikoides were generated in a slightly oblique direction at the epicone of cell and the chain-forming cells of M. polykrikoides could form the chain-forming temporary cysts without asexual or sexual reproduction. The planozygote produced by gamete fusion of M. polykrikoides may not necessarily develop to resting cysts but instead may divide into vegetative cells occasionally. In this phase, the armored cell, which was previously recorded by Kim et al. (2007), was not observed. The sexuality of M. polykrikoides had a homothallic mating behavior.
Stratigraphic cluster analysis using aquatic palynomorphs preserved in the core sediments reveale... more Stratigraphic cluster analysis using aquatic palynomorphs preserved in the core sediments revealed a rapid eutrophication due to anthropogenic activities from the mid 1960s in Beppu Bay, East Kyushu, Japan. These assemblages were divided into three major units: BP-I, BP-II and BP-III, and also only dinoflagellate cyst assemblages were divided into the following four units in Beppu Bay: BP-A, BP-B, BP-C, and BP-D. Unit boundaries based on aquatic palynomorphs and dinoflagellate cysts were different except in the upper part, BP-III and BP-D, both of which clearly indicated anthropogenic eutrophication in both sea water and bottom sediments. On the other hand, in dinoflagellate cyst assemblages, Unit BP-A was characterized by stable occurrence of Spiniferites bulloideus and Spiniferites hyperacanthus, Lingulodinium machaerophorum of Gonyaulacales, and reduction of heterotrophic Peridinioid Brigantedinium spp. In Unit BP-C there was a clear decrease of L. machaerophorum. Unit BP-B was c...
SUMMARYCellular and body scale structure of a new armored dinoflagellate Heterocapsa huensis, col... more SUMMARYCellular and body scale structure of a new armored dinoflagellate Heterocapsa huensis, collected from Hue, Vietnam were investigated. Morphology of motile cell was observed by light, fluorescent and scanning electron microscopy, and body scale structure was examined by whole mounts of transmission electron microscopy. Cells of H. huensis were ellipsoid with a spherical nucleus located in the posterior and multiple pyrenoids located above the nucleus; this arrangement was similar to that of Heterocapsa pygmaea. Transmission electron microscopy revealed ultrastructure of the body scales consisted of a rounded triangular basal plate and three‐dimensional ornaments. Structure of the basal plate resembles that of Heterocapsa illdefina; however, the number of the peripheral spine is different from that of H. illdefina and this structure has never been reported from Heterocapsa species. A new Heterocapsa species, H. huensis Iwataki et Matsuoka sp. nov., is described based on positions of organelles and body scale ultrastructure.
SUMMARYThe lateral variation of sediment properties and associated cyst content of sediment in Ma... more SUMMARYThe lateral variation of sediment properties and associated cyst content of sediment in Manila Bay were determined and their possible role/s in the occurrences of Pyrodinium bahamense Plate var. compressum (Bohm) Steidinger, Tester et Taylor toxic blooms were assessed. Manila Bay's surface sediment was determined to be silt dominated. Clay generally increased towards the coast, probably as a result of flocculation and rapid deposition upon entry of sediments from the rivers. High sand content characterized the southeastern part of the bay attributed to the greater sand inputs and relatively strong currents in this area. Bulk densities were lower in the eastern side of the bay from dilution by high organic load from sewage and urban areas. Benthic flux calculations, particularly NH3, suggest more than 50% nutrient contribution comes from sediments.In general, dinoflagellate cyst density increased from the center of the bay towards the coast, except in Pampanga Bay where it deceased near the coasts. A maximum of 23 dinoflagellate species were identified: 5 were autotrophic (Lingulodinium polyedrum (Stein) Dodge, Gonyaulax spp., Pyrophacus steinii (Schiller) Wall et Dale, Protoceratium reticulatum (Claparede et Lachmann) Butschli, and Pyrodinium bahamense var. compressum), and the rest were predominantly composed of Protoperidinium spp. and Diplopsalis spp. Heterotrophs comprised about 70% of the total cyst counts. Pyrodinium counts increased towards the northwestern part of the bay where it was the dominant autotroph species. Negative correlations were observed for live Pyrodinium cyst density and N flux, P flux, ratio of N to P and total organic carbon (TOC) content. However, areas with high N:P ratio contain abundant Pyrodinium live cysts.
ABSTRACT We propose a standardization of the gonyaulacalean (Dinophyceae) Kofoidian plate tabulat... more ABSTRACT We propose a standardization of the gonyaulacalean (Dinophyceae) Kofoidian plate tabulation using plate homology and overlap patterns, on the basis of a new morphological study of species belonging to 17 genera previously classified in the order Gonyaulacales: Acanthogonyaulax, Alexandrium, Amphidoma, Azadinium, Ceratium, Ceratocorys, Cladopyxis, Cribroperidinium, Fragilidium, Gonyaulax, Heterodinium, Lingulodinium, Paleophalacroma, Peridiniella, Spiraulax, Triadinium and Tripos. The plate immediately left of the flagellar pore is reinterpreted as a sulcal plate rather than its more conventional interpretation as a postcingular plate. With this new perspective the studied genera fall into two groups: 1) genera with only five Kofoidian postcingular plates (Acanthogonyaulax, Alexandrium, Ceratocorys, Cribroperidinium, Gonyaulax, Lingulodinium, Spiraulax and Triadinium) or six postcingular plates (Fragilidium); 2) genera with six Kofoidian postcingular plates, as well as differences in episomal plate patterns (Amphidoma, Azadinium, Cladopyxis, Heterodinium, Paleophalacroma and Peridiniella). The former are here considered true gonyaulacaleans, whilst the latter need further study for a more appropriate phylogenetic placement, and are here informally called non-gonyaulacaleans. In these non-gonyaulacalean genera, the first posterior intercalary plate overlaps the first postcingular plate/anterior left sulcal plate, but is always overlapped by the second postcingular homologue plate (a plate in similar position) demonstrating that the first plate of the postcingular series is not homologous in the two groups. Additionally, the identical overlapping pattern shows that the anterior left sulcal plate (Ssa) in gonyaulacaleans with five postcingular plates is the same plate as the first postcingular plate in gonyaulacaleans with six postcingular plates. Kofoidian definitions of posterior intercalary plates as well as antapical plates remain the same and are applied here. The Kofoidian hyposomal plate formula for gonyaulacaleans would then be 5–6''', 2p, 1''''.
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Papers by Kazumi Matsuoka