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Mertens K.N.,Ghent University | Bringue M.,University of Victoria | Van Nieuwenhove N.,University of Quebec at Montreal | Van Nieuwenhove N.,Leibniz Institute of Marine Science | And 11 more authors.
Journal of Quaternary Science | Year: 2012

Process length variation of cysts of the dinoflagellate Protoceratium reticulatum (Claparède et Lachmann) Bütschli in surface sediments from the North Pacific was investigated. The average process length showed a significant inverse relation to annual seawater density: σ t annual=-0.8674×average process length+1029.3 (R 2=0.84), with a standard error of 0.78kgm -3. A sediment trap study from Effingham Inlet in British Columbia revealed the same relationship between average process length and local seawater density variations. In the Baltic-Skagerrak region, the average process length variation was related significantly to annual seawater density: σ t annual=3.5457×average process length-993.28 (R 2=0.86), with a standard error of 3.09kgm -3. These calibrations cannot be reconciled, which accentuates the regional character of the calibrations. This can be related to variations in molecular data (small subunit, long subunit and internal transcribed spacer sequences), which show the presence of several genotypes and the occurrence of pseudo-cryptic speciation within this species. © 2012 John Wiley & Sons, Ltd.

Mertens K.N.,Ghent University | Gu H.,Third Institute of Oceanography | Takano Y.,Institute for East China Sea Research ECSER | Price A.M.,McGill University | And 7 more authors.
Palynology | Year: 2016

We establish the cyst-theca relationship of the dinoflagellate cyst species Trinovantedinium pallidifulvum Matsuoka 1987 based on germination experiments of specimens isolated from the Gulf of Mexico. We show that the motile stage is a new species, designated as Protoperidinium louisianensis. We also determine its phylogenetic position based on single-cell polymerase chain reaction (PCR) of a single cell germinated from the Gulf of Mexico cysts. To further refine the phylogeny, we determined the large subunit (LSU) sequence through single-cell PCR of the cyst Selenopemphix undulata isolated from Brentwood Bay (Saanich Inlet, BC, Canada). The phylogeny shows that P. louisianensis is closest to P. shanghaiense, the motile stage of T. applanatum, and is consistent with the monophyly of the genus Trinovantedinium. Selenopemphix undulata belongs to a different clade than Selenopemphix quanta (alleged cyst of P. conicum), suggesting that the genus Selenopemphix is polyphyletic. Trinovantedinium pallidifulvum is widely distributed with occurrences in the Gulf of Mexico, the North Atlantic, the northeast Pacific and southeast Asia. In addition, we illustrate the two other extant species, Trinovantedinium applanatum and Trinovantedinium variabile, and two morphotypes of Trinovantedinium. Geochemical analyses of the cyst wall of T. pallidifulvum indicate the presence of amide groups in agreement with other heterotrophic dinoflagellate species, although the cyst wall of T. pallidifulvum also includes some unique features. © 2016 AASP – The Palynological Society

Mertens K.N.,Ghent University | Takano Y.,Institute for East China Sea Research ECSER | Yamaguchi A.,Kobe University | Gu H.,Third Institute of Oceanography | And 5 more authors.
Systematics and Biodiversity | Year: 2015

Kolkwitziella acuta is a cyst-forming dinoflagellate with a unique tabulation, occurring in freshwater to brackish environments of Eurasia and the USA. Based on the unique thecal plate arrangement, this species was previously interpreted as a missing link in the evolution between the genus Protoperidinium and the Diplopsalioideae. We isolated living K. acuta cysts from the south-western Caspian Sea and the central Baltic (Finland), and re-established the cyst-theca relationship. The cysts had a distinctive polar and dorsoventral compression and a characteristic wrinkly texture. The plate formula of the thecate stage was Po, X, 4′, 2a, 7″, 3c+t, ?s, 5″′, 1″″. Large subunit (LSU) and small subunit (SSU) ribosomal DNA sequences obtained through single-cell PCR of these cysts reveal that this species is close to Protoperidinum excentricum which belongs to the Excentrica section of the genus Protoperidinium. We suggest that it evolved from the genus Diplopsalis through a split of the apical and anterior intercalary plates. Furthermore, that the split of the antapical plates occurred several times independently in the evolution of Protoperidinium and Diplopsalioideae and is therefore a polyphyletic trait. The cyst of Kolkwitziella is considered an indicator of low salinities, specifically between 0 and 22 psu. Geochemical analysis of the cyst walls suggests a heterotrophic mode of nutrition. © The Trustees of the Natural History Museum, London 2015. All Rights Reserved.

Luo Z.,Third Institute of Oceanography | Neil Mertens K.,Ghent University | Bagheri S.,Iranian Fisheries Science Institute | Aydin H.,Celal Bayar University | And 4 more authors.
European Journal of Phycology | Year: 2016

Species belonging to the dinophyte genus Scrippsiella are frequently reported in marine waters, but information on their distribution in brackish environments is limited. Here we describe a new species, S. plana, through incubation of non-calcified cysts from sediments collected in the South China Sea and Caspian Sea. The vegetative cells consist of a conical epitheca and a rounded hypotheca with the plate formula of Po, X, 4′, 3a, 7′′, 5C+t, 5S, 5′′′, 2′′′′. It differs from other Scrippsiella species by its flattened body in dorsoventral view and a small first anterior intercalary (1a) plate (half the size of plate 3a). Scrippsiella plana strains from the South China Sea and Caspian Sea share identical internal transcribed spacer (ITS) sequences, and show phenotypic plasticity and local adaptation in growth rate at various salinities, consistent with the environments in which they originated. In addition, two strains of S. spinifera were obtained by incubating ellipsoid cysts with calcareous spines from sediments collected along the Turkish and Hawaiian coast. They also share identical ITS sequences and differ from Duboscquodinium collinii (a parasite of tintinnids) only at two base pair positions (in the ITS2 region). Molecular phylogeny based on ITS and large subunit ribosomal DNA (LSU rDNA) sequences revealed that S. plana was nested within the Calciodinellum (CAL) clade and S. spinifera within the S. trochoidea (STR) clade. The phylogenetic position of ‘Peridinium’ wisconsinense is reported for the first time, which supports multiple transitions of the Peridiniales to freshwater. © 2016 British Phycological Society

Mertens K.N.,Ghent University | Wolny J.,University of South Florida | Wolny J.,Annapolis flyer cab | Carbonell-Moore C.,Oregon State University | And 8 more authors.
Harmful Algae | Year: 2015

Pyrodinium bahamense Plate 1906 is a tropical to subtropical dinoflagellate that can cause paralytic shellfish poisoning (PSP). Based on differences in the morphology of the motile stage, as well as geographic distribution, this species was separated into two varieties, the toxic var. compressum and the non-toxic var. bahamense by Steidinger et al. (1980). Thereafter, Balech (1985) carefully reinvestigated the two varieties and concluded there were no significant morphological differences between them. We re-examined the motile cell and cyst morphology of these two varieties, concurring with the arrangement of the sulcal plates, but demonstrating the plate overlap for the first time. The observed size-frequency spectra of cell body diameter, cyst body diameter and cyst process length were unimodal. Overall, we agree with Balech (1985) that there is no consistent criterion to unequivocally separate both varieties based on morphology. We therefore recommend ceasing the use of these varieties (and forma). In addition, we suggest that observations of both varieties in a single plankton sample should be interpreted as the occurrence of different life stages at the sampling time. However, the phylogenetic analysis using partial LSU rDNA sequence data revealed two clearly separated ribotypes within the Pyrodinium clade, an Indo-Pacific and Atlantic-Caribbean ribotype, suggesting that Pyrodinium bahamense is a species complex. The genetic distance between these ribotypes is short, which suggests a late Quaternary separation. Geochemical analyses of the cyst walls also show differences between specimens from both geographical regions. © 2014 Elsevier B.V.

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