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A Gymnodinium-like dinoflagellate, Kirithra sigma sp. nov., was isolated from Jiaozhou Bay, China, and the southern coast of Korea, and examined by light, scanning, and transmission electron microscopy. Pigment composition and nuclear-encoded partial large subunit ribosomal RNA (LSU rRNA) gene were determined. Cells were oval-shaped (26.4‒36.4 μm long and 17.7‒27.2 μm wide), with a conical epicone and hemispherical hypocone. Its cingulum and sulcus were deep and wide. The cingulum encircled the cell completely, its ends slightly overlapping and displaced one to two cingular widths; the sulcus and sulcal extension formed a sigmoid curve. The anterior sulcal extension contacted the apical structure complex (ASC). The ASC formed a complete circle, consisting of three parallel series of vesicles, and the amphiesmal vesicles within ASC were arranged with one central vesicle (sometimes two) encircled by approximately three rows of polygonal amphiesmal vesicles. Polygonal amphiesmal vesicles of different sizes covered the whole cell surface. The subspherical nucleus was located in the hypocone. Pigment analysis showed that peridinin was the main accessory pigment. The present species is morphologically similar to Kirithra asteri but differs in numbers and rows of amphiesmal vesicles within the ASC, absence of ventral pore, and a sigmoid curve formed by the sulcus and sulcal extension. The partial LSU rRNA gene sequence (c. 1400 bases) of K. sigma differed by c. 5.3% from that of K. asteri. Molecular phylogeny revealed that K. sigma formed an independent sister clade to K. asteri, indicating they are congeneric but different species. [ABSTRACT FROM AUTHOR]

Although the genus Pseliodinium within the family Ceratoperidiniaceae includes Ceratoperidinium falcatum, Cochlodinium cf. convolutum, C. cf. helix and unidentified Cochlodinium species, it is in need of reclassification because of the morphological differences and lack of morphological details of the species within the genus. A Cochlodinium-like species was isolated from a Korean coastal area and examined by light and scanning electron microscopy, as well as by the analysis of nuclear-encoded small subunit (SSU) and large subunit (LSU) rDNA. The Korean isolate was morphologically characterized by cellular torsion, and outer rows consisting of small rectangular and polygonal vesicles were visible along the sides of the cingulum. The apical structure complex (ASC) formed a complete circle surrounding the cell apex, consisting of three parallel rows of vesicles. In the ASC, the upper row was sometimes hidden and very small knobs were present on the central row. Morphological characteristics separated the Korean isolate from Ce. margalefii, Pseliodinium fusus(=Ce. falcatum), Kirithra asteri and Gymnodinium species (Gymnodinium sp. 1 and sp. 2) within the family Ceratoperidiniaceae. However, the morphological characteristics coincided with those of the previously recorded C. convolutum, C. cf. helix and other Cochlodinium species within the same family. Phylogeny based on SSU and LSU rDNA sequences revealed that the Korean isolate forms a clade independent from P. fusus, although they have high sequence similarity. Based on the morphological and phylogenetic analyses, we propose the new genus Torquentidium gen. nov. and a new combination for C. cf. helix and the Korean isolate Torquentidium convolutum erected within the family Ceratoperidiniaceae. [ABSTRACT FROM AUTHOR]

We describe the life cycle, morphology and molecular phylogenetic position of Fragilidium mexicanum, based on vegetative cells established by incubation of resting cysts isolated from sediment trap samples collected at Jinhae–Masan Bay, Korea. Resting cysts of F. mexicanum were spherical and surrounded by transparent mucilage, similar to other Fragilidium species. Germinated vegetative cells were identified as F. mexicanum based on thecal morphology and tabulation; the plate formula was Po, Pc, 4ʹ, 8″, 10c, 6s, 7ʹʹʹ, 1p, 2ʹʹʹʹ. Molecular phylogenetic analyses of sequence data for small and large subunits of ribosomal DNA genes revealed that Fragilidium species were monophyletic with high supports and that F. mexicanum formed a separate clade with Fragilidium sp. (JQ317599). Time-lapse photography was used to clarify the life history. Isolated resting cysts germinated into an unarmoured planomeiocyte and directly formed the pellicle cyst, with an armoured planomeiocyte emerging from the pellicle cyst. The armoured planomeiocyte underwent ecdysis and formed a coccoid meiocyte, with a two-celled chain emerging from the coccoid meiocyte. Like the armoured planomeicyte, vegetative cells also underwent ecdysis and then divided into two daughter cells that eventually emerged as motile vegetative cells. The life cycle of F. mexicanum has nonmotile life history stages that regularly alternate with motile stages. The nonmotile stage consists of five forms: resting cyst, pellicle cyst, asexual coccoid stage, coccoid meiocyte, and zygote. The motile stage also has five forms: unarmoured and armoured planomeiocyte, planozygote, gamete and vegetative cell. [ABSTRACT FROM AUTHOR]

Investigation of phytoplankton from East China Sea of the Pacific Ocean, offshore Réunion Island of the Indian Ocean, and the French Atlantic coast revealed a species of poorly known armored fusiform dinoflagellate. To clarify this species, morphology and phylogeny based on mitochondrial and nuclear protein gene sequence (Cox1, Cob and Hsp90) concatenated with the SSU, ITS region and LSU rDNA sequences were analysed. Epifluorescence and scanning electron microscopy observations revealed that the nucleus of the specimen was elongated, sausage-shaped and located equatorially on the left lateral side of the cell, and that the plate formula is Po, 3′, 1a, 6″, 6C, 8S, 5‴, 1p, 2′‴. These morphological features indicate that the species can be assigned to Centrodinium punctatum. Interestingly, the phylogenetic analyses placed this species within the Alexandrium clade, with Alexandrium affine being its closest relative. This indicates that genus Alexandrium is not monophyletic. The most similar morphological traits between C. punctatum and Alexandrium species were the shape of apical pore plate and the arrangement of the sulcal plates. However, since there are significant morphological differences between C. punctatum and Alexandrium species, further studies are needed to clarify the relation between the morphology and molecular phylogeny of other Centrodinium -related fusiform species. [ABSTRACT FROM AUTHOR]

This study provides the first morphological features of resting cysts of Cochlodinium polykrikoides collected from Korean coastal sediments. Evidence for the existence of resting cysts of C. polykrikoides is based on the morphological and molecular phylogenetic data of the germinated cells and a resting cyst. The morphology of the resting cysts differed from that reported previously in sediments and culture experiments. The distinct feature is that the cyst body was covered by the reticulate ornaments and spines. [ABSTRACT FROM AUTHOR]

• Ellipsoidal alexandrium cysts in jinhae-masan bay are produced by two species, alexandrium catenella (Group I) and A. pacificum (Group IV). • Cyst germination temperature is lower for alexandrium catenella (Group I) than for A. pacificum (Group IV). • Differences in cyst germination rates among sampling sites can be determined by the differences in distribution and abundance of the species. • Concentrations of ellipsoidal alexandrium cysts from surface sediments of jinhae-masan bay are higher in february than in august. • PST profiles of alexandrium catenella (Group I) and A. pacificum (Group IV) in jinhae-masan bay are dominated by GTX-3 and GTX-4. To better understand the outbreaks of paralytic shellfish poisoning and bloom dynamics caused by Alexandrium species in Jinhae-Masan Bay, Korea, the germination and distributions of ellipsoidal Alexandrium cysts were investigated, and paralytic shellfish toxins (PSTs) profiles and contents were determined using strains established from germling cells. The phylogeny and morphological observations revealed that the germinated vegetative cells from ellipsoidal cysts collected from the surface sediments in Jinhae-Masan Bay belong to Alexandrium catenella (Group I) and A. pacificum (Group IV) nested within A. tamarense species complex. Cyst germinations of A. catenella (Group I) were observed at only 10 °C, whereas cysts of A. pacificum (Group IV) could germinate at temperature ranges of 10 to 25 °C. Maximum germination success (85%) for isolated cysts occurred at 15 °C, and the germling cells were A. pacificum (Group IV). The results indicate that the variation in water temperature in Jinhae-Masan Bay can control the seasonal variations in germination of cysts of A. catenella (Group I) and A. pacificum (Group IV). The germination rates of ellipsoidal Alexandrium cysts were different among sampling sites in Jinhae-Masan Bay, probably because of differences in distribution and abundance of A. catenella (Group I) and A. pacificum (Group IV) in the sediments. The ellipsoidal Alexandrium cyst concentrations were much higher in February than in August, however the distributions were similar. Gonyautoxins 3 and 4 (GTX-3 and GTX-4) contributed a large proportion (>90%) of the toxins produced by strains A. catenella (Group I) and A. pacificum (Group IV) established from germling cells, and the total cellular contents were higher in A. catenella (Group I) than in A. pacificum (Group IV). [ABSTRACT FROM AUTHOR]

Dense patches were observed in the tidal pools of the southern area of Korea. To clarify the causative organisms, the cells were collected and their morphological features were examined using light and scanning electron microscopy (SEM). In addition, after establishing strains for the cells the molecular phylogeny was inferred with concatenated small subunit (SSU) and large subunit (LSU) rRNA sequences. The cells were characterized by a nucleus in the hypotheca, strong reticulations in thecal plates, the separation of plates 2a and 3a, the tear-shaped apical pore complex, an elongated rectangular 1a plate and the absence of the right sulcal list. The thecal plate formula was Po, X, 4′, 3a, 7″, 6c, 4S, 5′′′, 2′′′′. Based on these morphological features, the cells were identified as Bysmatrum subsalsum. In the culture, the spherical cysts of B. subsalsum without thecal plates were observed. Molecular phylogeny revealed two ribotypes of B. subsalsum are identified; The Korean isolates were nested within the ribotype B consisting of the isolates from China, Malaysia and the French Atlantic, whereas the ribotype A includes only the isolates from the Mediterranean Sea. In the phylogeny, B. subsalsum and B. austrafrum were grouped. This can be supported by the morphological similarity between the two species, indicating that the two species may be conspecific, however B. subsalsum may distinguish from B. austrafrum, because of differences in the types of eyespots reported in previous studies. These findings support the idea that there is cryptic diversity within B. subsalsum. [ABSTRACT FROM AUTHOR]

Two new benthic freshwater species belonging to the genus Achnanthidium were found in Korea. Achnanthidium ovale sp. nov. and A. cavitatum sp. nov. are described as new species based on light and scanning electron microscopy observations and molecular analyses. Both species are compared with the type material of morphologically similar taxa. Achnanthidiumovale differs from other species belonging to the A.pyrenaicum complex in outline, striation pattern, raphe central endings, and freestanding areolae at the apices. Achnanthidiumcavitatum differs from other species in the A.minutissimum complex in outline, broad axial central area in the raphel ess valve, and slit-like areolae near the axial central area. We assessed their molecular characteristics by analyzing nuclear small subunit (SSU) rRNA and chloroplast-encoded rbcL gene sequences. Both the morphological comparison and the SSU and rbcL sequence analyses provide strong evidence to support the recognition of A. ovale and A. cavitatum as new species. [ABSTRACT FROM AUTHOR]

• Prorocentrum shikokuense Hada, P. donghaiense Lu and Prorocentrum obtusidens Schiller are conspecific. • Prorocentrum obtusidens is a senior to P. shikokuense and P. donghaiense. • Prorocentrum obtusidens is a separate species from P. dentatum sensu stricto , P. veloi and P. monacense. • The periflagellar area of Prorocentrum obtusidens consists of seven platelets bearing a wing-like structure and two platelets without a wing-like structure, one flagellar pore and one accessory pore. In Japanese, Chinese and Korean coastal waters, recurrent blooms of a small, elongate Prorocentrum species have been observed in recent years. In previous studies, this species has been respectively identified as P. shikokuense , P. donghaiense and P. dentatum , despite morphological similarity and identical rDNA sequences. To resolve the confusion, morphological features, including the architectural details of the periflagellar area, were examined and ribosomal DNA (rDNA) sequences were obtained from specimens collected from the East China Sea and Korean coast, and a strain established in the waters off the Canary Islands of Spain. In addition, the descriptions of the three species and allied species were reviewed. Morphological observations and a phylogeny based on the SSU, ITS region and LSU rDNA sequences revealed that the previously confused species and our studied strains are conspecific and that the morphology of strains identified as P. dentatum in the phylogenetic trees does not coincide with P. dentatum sensu stricto. The confusion can be traced back to Dodge (1975, p. 116), who considered P. veloi, P. monacense and P. obtusidens as junior heterotypic synonyms of P. dentatum. However, Dodge's P. dentatum are closer to P. obtusidens sensu stricto , rather than P. dentatum sensu stricto. P. obtusidens sensu stricto can be distinguished from P. dentatum sensu stricto by its relatively small size, parallel sides towards the anterior and a blunt anterior extension on one side. This indicates that P. obtusidens should not be considered a synonym of P. dentatum sensu stricto. In addition, a comparison of the original descriptions of P. obtusidens and allied species allowed to conclude that small, elongate Prorocentrum from Japanese, Chinese and Korean coastal waters previously identified as P. shikokuense , P. donghaiense , P. dentatum sensu Yoo and Lee (1986) and the specimens studied herein, which share identical rDNA sequences, morphologically coincide with P. obtusidens. Therefore, it is proposed that P. shikokuense and P. donghaiense should be regarded as junior synonyms of P. obtusidens. [ABSTRACT FROM AUTHOR]