Zhun Li

Morphology and phylogeny of a new woloszynskioid dinoflagellate Tovellia paldangensis sp. nov. (Dinophyceae)

Abstract: The genus Tovellia contains approximately eight described species. A new species, Tovellia paldangensis sp. nov. was observed by incubation of a cyst from sediment collected in the Paldang Dam Lake in Korea. The vegetative cells of this new species were 20.0–27.0 μm long, 18.0–23.0 μm wide, and 17.0–20.5 μm thick. The cingulum was displaced by one cingulum width, the nucleus was located in the posterior part of the cell, and the chloroplasts were numerous and in yellow-green in color. A prominent red body was present on each side of the cingulum. The amphiesma had numerous thin polygonal plates that were arranged in three to four latitudinal series on the epicone and in two to three series on the hypocone. A narrow apical line of plates (ALP) extended over the anterior part of the cell, approximately in a 3/4 of the ventral side and 1/4 of the dorsal side of the epicone. The antapical plate was usually hexagonal. T. paldangensis was clearly differentiated from the other species of Tovellia by the morphology of its vegetative cell (two red bodies, and the ALP lines on each side separated by a row of four to five elongate plates) and the resting cyst (typically covered with numerous short solid spines). Phylogenetic analysis based on partial large subunit ribosomal RNA gene sequences indicated that T. paldangensis was most closely related to T. coronata, T. sanguinea, and T. aveirensis.

Brigantedinium majusculum is the cyst of Protoperidinium sinuosum (Protoperidiniaceae, Dinophyceae)

Abstract: Two morphologically distinct species, Brigantedinium majusculum and Trinovantedinium applanatum, have been suggested as a cyst stage of Protoperidinium pentagonum; however, the cyst–theca relationships are still virtually undefined. In this study, we re-examined the motile stage of B. majusculum via thecal plate analysis together with a molecular phylogenetic analysis based on partial large-subunit ribosomal DNA gene sequences. The morphological features of motile cells germinated from B. majusculum were identical to those of Pr. sinuosum, and the molecular phylogenetic analysis showed that the germinated cells and B. majusculum are closely related to Pr. pentagonum and Pr. latissimum as a sister group. Additionally, high sequence divergences were observed between the germinated cells and B. majusculum as well as Pr. pentagonum and Pr. latissimum (18.0–19.5% according to P-values and 20.7–22.9% according to Kimura two-parameter values). On the basis of these results, our study indicates that B. majusculum should be accepted as the cyst of Pr. sinuosum.

Formation and germination of temporary cysts of Cochlodinium polykrikoides Margalef (Dinophyceae) and their ecological role in dense blooms

While the initiation and development of dense bloom of Cochlodinium polykrikoides have been shown to be related to some environmental factors, little is known about the ecological role of the formation and germination of temporary cysts, nor of their significance for the rapid expansion of dense regional-scale blooms. This study examined the factors affecting the formation and germination of temporary cysts of C. polykrikoides, and provides details about the germination process. In the laboratory experiments, C. polykrikoides produced the chain-forming temporary cysts that are immobile and surrounded by a hyaline membrane. The encystment experiment indicated that darkness induces the formation of chain-forming temporary cysts, consistent with field observation of morphology and fluxes of temporary cysts. Germination occurred twice from a single four-celled temporary cysts within 24h after exposure to light, and the germlings appeared as two-celled chain-forming vegetative cells. The germination behavior of temporary cysts of C. polykrikoides differs from that of other dinoflagellates, and this may be a survival strategy for the maintenance of population size during dense blooms.

Cyst-motile stage relationship, morphology and phylogeny of a new chain-forming, marine dinoflagellate Grammatodinium tongyeonginum gen. & sp. nov. from Korea

Abstract: A new phototrophic dinoflagellate, Grammatodinium tongyeonginum gen. & sp. nov., was established by incubating resting cysts collected from surface sediment samples from Tongyeong coastal area, Korea. The resting cysts were ovoid with a large reddish pigment body and surrounded with a thick mucous layer that incorporated attached detritus particles. The vegetative cells were 24.6–40.9 μm long and 16.4–27.3 μm wide. The cell surface was covered with prominent longitudinal equidistant furrows. The cingulum was narrow and descended two to eight times its width. The nucleus was located at the central part of the epicone. The peripheral chloroplasts were usually granular and yellow-green in culture and were distributed along the rim of the cingulum. The horseshoe-shaped apical groove ran from the end of the sulcal extension anticlockwise around the apex. The distal end of the apical groove was located next to the extension of the sulcus and more to the ventral side than the proximal end. Molecular phylogenetic analysis using small subunit ribosomal DNA (SSU rDNA) gene sequences revealed that G. tongyeonginum was allied with the Cucumeridinium species. Large subunit ribosomal DNA (LSU rDNA) sequences revealed that G. tongyeonginum formed a clade distantly related to the other genera of Gymnodiniales. The combination of morphological characteristics with molecular phylogenies distinguished the present species from other genera within Gymnodiniales.

Morphological identification of Alexandrium species (Dinophyceae) from Jinhae-Masan Bay, Korea

Outbreaks of paralytic shellfish poisoning (PSP) and dense blooms caused by Alexandrium species in Jinhae-Masan Bay, Korea have been nearly annual events for many years. However, excluding some Alexandrium species responsible for PSP, there are no critical reports on the morphology of Alexandrium species in this bay. To identify the Alexandrium species based on detailed morphological features, vegetative cells collected water samples and established by the incubation of resting cysts isolated from sediment trap samples were analyzed. Four species of Alexandrium were identified: Alexandrium affine, A. fundyense, A. catenella, and A. insuetum. Morphological features of these species were basically consistent with those outlined in previous studies. However, the ventral pore and the connecting pore on the sulcal plate, which have been accepted as diagnostic characteristics for the identification of A. fundyense and A. catenella, need to be reevaluated, indicating that useful morphological features for identifying these two species should be recommended to avoid confusion in the classification of species in genus Alexandrium.

Morphology and phylogeny of an unarmored dinoflagellate, Karlodinium jejuense sp. nov. (Gymnodiniales), isolated from the northern East China Sea

An unarmored dinoflagellate, Karlodinium jejuense sp. nov., was isolated from the northern East China Sea. The species was characterized by light, fluorescence, and scanning electron microscopy of laboratory cultures, as well as SSU rDNA, ITS region (ITS1‐5.8S‐ITS2) and LSU rDNA gene sequences. Cells were ellipsoid to oval, small‐sized, 9.9–16.0 μm in length and 6.2–12.7 μm in width. The chloroplasts were 7–10 in number and yellow‐green in color. The central nucleus was large, located in the center of the cell. The linear apical groove with outward thick rolled margins was very short, and there was no ventral pore. Small pores were irregularly distributed on the cell surface. The amphiesmal vesicles were hexagonal and pentagonal. Karlodinium jejuense was morphologically similar to K. ballantinum but differed in cell surface characteristics and swimming pattern. The partial LSU sequence of K. jejuense differed by 3.7–4.1% from that of K. ballantinum. Molecular phylogenetic analyses of multi‐gene sequences revealed that K. jejuense was an independent species nested within the Karlodinium clade. Phylogenetic analysis based on partial LSU rDNA gene sequences indicated that K. jejuense was most closely related to K. gentienii and K. ballantinum.

Morphology and phylogeny of Triadinium polyedricum (Pouchet) Dodge (Dinophyceae) from Korean coastal waters

To identify features that can be used to differentiate Triadinium polyedricum from other related species, such as Fukuyoa paulensis and Alexandrium species, the detailed morphology and phylogeny of T. polyedricum collected from Korean coastal waters were investigated. The cells had a plate formula of Po, 3′, 7″, 5‴, 1p and 2″″, which is consistent with morphological descriptions in previous reports. Large subunit ribosomal DNA sequences also revealed that T. polyedricum from Korean coastal waters is identical to previously recorded isolates. T. polyedricum is morphologically characterized by a ventral pore in the 1″ plate that is comparable to F. paulensis and Alexandrium species. This result indicates that the location and presence of this ventral pore seems suitable for differentiating T. polyedricum from other related species.

Morphological Features of Marine Dinoflagellates from Jangmok Harbour in Jinhae Bay, Korea: A Case of 30 Species in the Orders Prorocentrales, Dinophysiales, Gonyaulacales and Gymnodiniales

Most previous studies on dinoflagellates in Korean coastal areas were conducted without morphological descriptions and illustrations of the observed dinoflagellates. This indicates that the species and diversity of dinoflagellates may have been respectively misidentified and underestimated in the past, probably due to cell shrinkage, distortion and loss caused by sample fixation. This study provides information on the morphological observations of four dinoflagellate orders (Prorocentrales, Dinophysiales, Gonyaulacales and Gymnodiniales) from Jangmok Harbour in Jinhae Bay, Korea. The unfixed samples were collected weekly from December 2013 to February 2015. A total of 13 genera and 30 species were identified using light and scanning electron microscopy, although some samples were not clarified at the species level. Harmful dinoflagellates, Prorocentrum donghaiense, Tripos furca, Alexandrium affine, A. fundyense, Akashiwo sanguinea and Cochlodinium polykrikoides, were identified based on the morphological observations. The results also reflect the occurrence and identification of dinoflagellates that had not been previously recorded in Jangmok Harbour.