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The family Peridiniopsidaceae encompasses mainly freshwater species of the genera Peridiniopsis, Palatinus and Parvodinium. Only one benthic, marine species ‘Scrippsiella’ hexapraecingula has been attributed to this family. Here we established five strains by isolating single Parvodinium-like cells from the marine Gulf of Thailand, Hainan Island waters (China), off Manado (Indonesia) and from a freshwater reservoir in Fuzhou (China). All strains were examined with light, scanning and transmission electron microscopy, and their SSU, ITS-5.8S and partial LSU rRNA regions were sequenced. Four marine strains share a plate formula of Po, cp, X, 4′, 2a, 6′′, 6C, 4S, 5′′′, 2′′′′ and are herein attributed to a new genus Johsia as J. chumphonensis gen. et sp. nov. Its theca is characterized by an epitheca 1.5 times as long as the hypotheca in dorsal view and a 2a plate about half the size of 1a. A type B eyespot was observed in J. chumphonensis comprising two rows of lipid globules within a chloroplast with a single row of crystals overlying the eyespot. Production of spherical cysts was observed in culture. The freshwater strain shows a plate pattern of Po, cp, X, 4′, 2a, 7′′, 6C, 5S, 5′′′, 2′′′′, characterized by two unequal antapical plates and a lack of antapical spines, fitting the description of Peridinium parvulum, which was transferred to Parvodinium as P. parvulum comb. nov. In this species, a type A eyespot was observed comprising four rows of lipid globules within a chloroplast. A molecular phylogeny was inferred based on concatenated data from SSU, ITS-5.8S and partial LSU rRNA gene sequences using maximum likelihood and Bayesian inference. Our results show that Johsia is nested within the Peridiniopsidaceae and is a sister clade to Peridiniopsis borgei and the strain UTEX1948 identified as ‘Scrippsiella’ hexapraecingula with three anterior intercalary plates.

The genus Acanthogonyaulax (Kofoid) H.W.Graham is a rarely observed tropical gonyaulacoid dinoflagellate, first documented at the end of the 19th century. It was initially described as a species of...

A new dinoflagellate cyst genus and species are described here as Hiddenocysta gen. nov. and Hiddenocysta matsuokae sp. nov. from Holocene sediments in a core from the west coast of Vancouver Island (British Columbia, Canada). The genus Hiddenocysta encompasses spherical to ovoid skolochorate cysts, characterized by a gonyaulacoid plate pattern and a 2P precingular archeopyle. The species H. matsuokae is characterized by a granular wall and slender trifurcate processes with heavily perforated process bases. Two end members are described here based on process morphology and number of processes (formas 1 and 2). Cyst wall chemistry is analyzed using micro-Fourier transform infrared (FTIR) spectroscopy and reveals a unique dinosporin composition consistent with a gonyaulacoid autotrophic feeding strategy.

Gonyaulax verior was initially described as Amylax diacantha from Belgian coastal waters a century ago but its detailed morphology needed restudy. Here, we established nine strains of G. verior by germinating cysts or isolating cells from localities from the European Atlantic to the Caspian Sea and the Pacific Ocean. Both cyst and thecal morphology were examined by light and scanning electron microscopy. SSU, LSU and/or ITS-5.8S rRNA gene sequences were obtained from all strains. Cells of G. verior have a plate formula of Po, 4′, 2a, 6-7′′, 6C, 6S, 6′′′, 1p, 1′′′′ with an L-type ventral organisation, characterised by two either straight or curved antapical horns of variable length. Cysts of G. verior are oval, smooth and contain one or two yellow accumulation bodies. The maximum-likelihood and Bayesian inference analyses based on SSU and LSU rRNA gene sequences revealed two clades of G. verior, referred to as ribotypes A and B. Genetic distances based on ITS-5.8S rRNA gene sequences within the same ribotype were less than 0.06, but greater than 0.32 between ribotypes. G. verior is reclassified as Sourniaea diacantha gen. et comb. nov., which is attributed to Lingulodiniaceae together with Pyxidinopsis, Lingulodinium and Amylax. Our results suggest that Lingulodiniaceae can be separated from Protoceratiaceae and Gonyaulacaceae based on ventral organisation, apical complex, ventral pore and number of anterior intercalary plates. One strain of S. diacantha was examined for yessotoxin production by LC-MS/MS but did not produce toxin.

Among dinoflagellates, extant cladopyxidaceans may provide a missing link to better understand the first evolutionary transformations from ancestral configurations towards the more abundant and more derived patterns in Gonyaulacales and Peridiniales. A restudy of the extant, motile-defined Micracanthodinium setiferum from plankton samples from the Indian and Atlantic Oceans and Mediterranean Sea demonstrates that the correct plate formula is Po Pt X 3′+*4′ 4a 7′′ 7C 4S? 6′′′ 0p 2′′′′. A ventral pore is found between 1′, 3′ and *4′. A restudy of the extinct, fossil-defined Cladopyxidium saeptum from the upper Paleocene of Delaware (U.S.A), demonstrated the presence of an identical tabulation. A ventral pore (=porichnion) was positioned between *1′ and 7′′. Cladopyxidium is morphologically closer to Micracanthodinium than to Cladopyxis. However, since Cladopyxidium has been extinct since the middle Eocene it is unlikely that Micracanthodinium and Cladopyxidium will have a direct biological link; the close morphological link between both does suggest an important phylogenetic relationship between both in the evolution of cladopyxidaceans.

Bauer, Wolfgang, Gottschling, Marc, Keupp, Helmut, Kusber, Wolf-Henning, Mertens, Kenneth N. (2021): Validation of the calcareous dinophyte Wallidinellum (Peridiniales), with notes on the status of fossils in the Code. Phytotaxa 520 (3): 296-300, DOI: 10.11646/phytotaxa.520.3.9, URL: http://dx.doi.org/10.11646/phytotaxa.520.3.9

The chemical composition of recent and fossil organic-walled dinoflagellate cyst walls and its diversity is poorly understood and analyses on single microscopic specimens are rare. A series of infrared spectroscopic experiments resulted in the proposition of a standardized attenuated total reflection micro-Fourier transform infrared-based method that allows the collection of robust data sets consisting of spectra from individual dinocysts. These data sets are largely devoid of nonchemical artifacts inherent to other infrared spectrochemical methods, which have typically been used to study similar specimens in the past. The influence of sample preparation, specimen morphology and size and spectral data processing steps is also assessed within this methodological framework. As a result, several guidelines are proposed which facilitate the collection and qualitative interpretation of highly reproducible and repeatable spectrochemical data. These, in turn, pave the way for a systematic exploration of dinocyst chemistry and its assessment as a chemotaxonomical tool or proxy.

A high-resolution dinoflagellate cyst analysis on a sediment core GLW31D from the northern South China Sea (SCS) was performed to reconstruct paleoceanographic conditions over the last 12,500 years through qualitative, semi-quantitative, and quantitative methods. A modern dataset with 398 reference sites in the northern Pacific was assembled and used to identify the relationship between dinoflagellate cyst assemblages and sea-surface temperature (SST), sea-surface salinity (SSS) and primary productivity (PP). Modern analog technique (MAT) was applied to offer first dinoflagellate-cyst-based quantitative estimates of Holocene sea-surface conditions in the western North Pacific. The downcore reconstructions show that SST, SSS and PP were predominantly controlled by the changes in coastal and oceanic currents due to the changes in sea level and monsoon systems. Our results indicate that SST increased while SSS and PP decreased from 12,500 to ~6800 cal yr BP, reaching the maximum SST and the minimum SSS and PP during ~6800–5000 cal yr BP, and followed by a slight decline in SST with minor increases in SSS and PP. The three intervals correspond to the regional onshore sea-level stages of rising, stabilization in a highstand and slight drop, respectively. The Kuroshio Current strongly influenced the core site before ~9900 cal yr BP, reflected by the highest abundances of oceanic Impagidinium spp. and high reconstructed SSS values. This can be explained by a lack of water input from the East China Sea before the opening of the Taiwan Strait. The warmest period, from ~6800 cal yr BP to ~5500 cal yr BP, is recorded by the highest Dapsilidinium pastielsii abundances. Two short-term high-PP events of ~2700–2400 cal yr BP and ~1000–600 cal yr BP, which were characterized by opposite climatic conditions, coincided with two notable societal (dynasty) collapses of China. Enhanced anthropogenic activities since the Late Bronze Age most likely partially affected the high PP through influencing river inputs to the northern SCS.

It is well known that modern resting cysts with morphologies matching those of species of the fossil genus Spiniferites germinate into motile cells of the genus Gonyaulax. Different Spiniferites species have been connected to a single Gonyaulax species, raising the question of whether they are over-classified. Through germination experiments of cysts with the morphological features of four species of Spiniferites, viz. S. bentorii, S. hyperacanthus, S. ramosus and S. scabratus, we established cyst-theca relationships. Cysts with the morphology of S. bentorii gave rise to vegetative, motile cells of Gonyaulax nezaniae sp. nov., which is characterized by two stout antapical spines. Cysts with S. hyperacanthus and S. ramosus morphologies germinated into Gonyaulax whaseongensis and G. spinifera, respectively. Cysts with S. scabratus morphology lacked a ventral pore and were attributed to Gonyaulax cf. spinifera. Gene sequences for SSU, LSU and/or ITS-5.8S rRNA were obtained from these four species, and from cysts with the morphology of Spiniferites belerius, S. mirabilis, S. lazus, Spiniferites cf. bentorii and Tectatodinium pellitum. The maximum likelihood and Bayesian inference analyses based on LSU and SSU rRNA gene sequences revealed that cysts assignable to Spiniferites formed a polyphyletic group, intermingled with Tectatodinium, Bitectatodinium, Ataxiodinium and Impagidinium, whereas Gonyaulax species appeared as monophyletic. From our results we inferred the phylogenetic positions of S. bentorii, S. mirabilis, S. lazus, S. scabratus, Tectatodinium pellitum and Gonyaulax digitale for the first time, supporting the idea that Spiniferites species are not over-classified and each of them may correspond to different Gonyaulax species.

The dinoflagellate order Peridiniales encompasses several well circumscribed families. However, the family level of some genera, such as Bysmatrum and Vulcanodinium, has remained elusive for many years. Four Peridinium-like strains were established from the Atlantic coast of France and North Sulawesi, Indonesia through cyst germination or isolation of single cells. The cyst-theca relationship was established on specimens from the French Atlantic. Their morphologies were examined using light, scanning and transmission electron microscopy. The cells were characterized by a much larger epitheca relative to the hypotheca, a large anterior sulcal (Sa) plate deeply intruding the epitheca and a small first anterior intercalary plate. The plate formula was identified as Po, cp, X, 4 ', 3a, 7 '', 6C, 5S, 5 ''', 2 '''', shared by Apocalathium, Chimonodinium, Fusiperidinium and Scrippsiella of the family Thoracosphaeraceae but the configuration of Sa plate and anterior intercalary plates is different. Transmission electron microscopy showed that the eyespot was located within a chloroplast comprising two rows of lipid globules and thus belongs to type A. All four strains were classified within a new genus Caladoa as C. arcachonensis gen. et sp. nov. Small subunit ribosomal DNA (SSU rDNA), partial large subunit ribosomal DNA (LSU rDNA) and internal transcribed spacer ribosomal DNA (ITS rDNA) sequences were obtained from all strains. Genetic distance based on ITS rDNA sequences between French and Indonesian strains reached 0.17, suggesting cryptic speciation in C. arcachonensis. The maximum likelihood and Bayesian inference analysis based on concatenated data from SSU and LSU rDNA sequences revealed that Caladoa is monophyletic and closest to Bysmatrum. Our results supported that Caladoa and Bysmatrum are members of the order Peridiniales but their family level remains to be determined. Our results also support that Vulcanodinium is closest to the family Peridiniaceae.

Round brown process-bearing cysts (RBPC) produced by dinoflagellates (Dinophyceae) occur as an important part of assemblage diversities in seafloor sediments worldwide. Here a new species, Islandinium pacificum, is described from surface sediment samples from coastal waters of British Columbia (Canada). Additional observations are made on material from the Holocene of Kyuquot Sound (Vancouver Island, Canada) and the Eemian of the Voring Plateau (North Atlantic). The cysts have a smooth wall and bear acuminate processes with barbs. Incubation experiments reveal an affinity with the motile stage Protoperidinium mutsuense. The ecology of the new species is specified.

To evaluate the stability and resilience1 of coastal ecosystem communities to perturbations that occurred during the Anthropocene,2 pre-industrial biodiversity baselines inferred from paleoarchives are needed.3,4 The study of ancient DNA (aDNA) from sediments (sedaDNA)5 has provided valuable information about past dynamics of microbial species6, 7, 8 and communities9, 10, 11, 12, 13, 14, 15, 16, 17, 18 in relation to ecosystem variations. Shifts in planktonic protist communities might significantly affect marine ecosystems through cascading effects,19, 20, 21 and therefore the analysis of this compartment is essential for the assessment of ecosystem variations. Here, sediment cores collected from different sites of the Bay of Brest (northeast Atlantic, France) allowed ca. 1,400 years of retrospective analyses of the effects of human pollution on marine protists. Comparison of sedaDNA extractions and metabarcoding analyses with different barcode regions (V4 and V7 18S rDNA) revealed that protist assemblages in ancient sediments are mainly composed of species known to produce resting stages. Heavy-metal pollution traces in sediments were ascribed to the World War II period and coincided with community shifts within dinoflagellates and stramenopiles. After the war and especially from the 1980s to 1990s, protist genera shifts followed chronic contaminations of agricultural origin. Community composition reconstruction over time showed that there was no recovery to a Middle Ages baseline composition. This demonstrates the irreversibility of the observed shifts after the cumulative effect of war and agricultural pollutions. Developing a paleoecological approach, this study highlights how human contaminations irreversibly affect marine microbial compartments, which contributes to the debate on coastal ecosystem preservation and restoration.

To clarify an unspecified toxic Gambierdiscus-like species isolated from seawaters off Jeju Island, Korea, its morphology and molecular phylogeny based on the small subunit (SSU) and partial large subunit (LSU) rRNA gene sequences were examined. Cells were narrow in ventral view and broad in lateral view with a smooth surface. The round thecal pores were evenly distributed, with an average diameter of 0.41 µm. Cell depth, width and height were 51.7 ± 4.5 μm, 43.0 ± 4.2 μm and 55.0 ± 4.7 μm, respectively, and depth-to-width (D/W) and height-to-width (H/W) ratios were 1.1 ± 0.2 μm and 1.3 ± 0.02 μm, respectively. The nucleus was located in the hypotheca. Scanning electron microscope observations revealed that the cells displayed a plate formula of Po, 4′, 6′′, 6c, 6s, 5′′′ and 2′′′, and transmission electron microscope observation demonstrated that the cells contained crystal-like particles. Morphological features indicated that the unspecified Korean isolate belonged to the genus Fukuyoa, and based on the H/W and D/W ratios, the apical pore H/W ratio and thecal pore size, it could be differentiated from other Fukuyoa species. The phylogenetic analyses based on the SSU and LSU rRNA sequences revealed that the Korean isolate was nested within the genus Fukuyoa with high support, and it grouped with F. cf. yasumotoi isolated from Japan. Based on the morpho-molecular data, a new species, Fukuyoa koreansis sp. nov. is proposed. The maximum growth rate (0.254 d−1) of F. koreansis was observed at 25°C and a salinity of 25. The required levels of temperature and salinity for growth distinguished Fukuyoa koreansis from Gambierdiscus species. Previous article

8 pages, 2 tables, A recently published study analyzed the phylogenetic relationship between the genera Centrodinium and Alexandrium, confirming an earlier publication showing the genus Alexandrium as paraphyletic. This most recent manuscript retained the genus Alexandrium, introduced a new genus Episemicolon, resurrected two genera, Gessnerium and Protogonyaulax, and stated that: “The polyphyly [sic] of Alexandrium is solved with the split into four genera”. However, these reintroduced taxa were not based on monophyletic groups. Therefore this work, if accepted, would result in replacing a single paraphyletic taxon with several non-monophyletic ones. The morphological data presented for genus characterization also do not convincingly support taxa delimitations. The combination of weak molecular phylogenetics and the lack of diagnostic traits (i.e., autapomorphies) render the applicability of the concept of limited use. The proposal to split the genus Alexandrium on the basis of our current knowledge is rejected herein. The aim here is not to present an alternative analysis and revision, but to maintain Alexandrium. A better constructed and more phylogenetically accurate revision can and should wait until more complete evidence becomes available and there is a strong reason to revise the genus Alexandrium. The reasons are explained in detail by a review of the available molecular and morphological data for species of the genera Alexandrium and Centrodinium. In addition, cyst morphology and chemotaxonomy are discussed, and the need for integrative taxonomy is highlighted, Support to DMA from the NOAA ECOHAB program (Grant #NA15NOS4780181) is gratefully acknowledged. Support to EG, AR, NS from the COPAs project (CTM2017-86121-R) is acknowledged. IGL and CJBS are COFFA-IPN and EDI-IPN fellows, With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

Dinoflagellates are a major component of the modern plankton. Of the 2192 species of marine free-living dinoflagellates presently described, an increasing number are being shown to produce resting cysts (probably hypnozygotes) within their life cycle. With rare exception, only the resting cysts fossilize, so they are of central importance in tracing the history of dinoflagellates through geological time. Cysts of many of the more common dinoflagellate species have distinctive morphologies allowing their geographic and stratigraphic occurrences to be traced. An ever-increasing number of taxa are also being shown to produce distinctive and geologically preservable cysts, potentially enhancing our knowledge of the diverse representation of dinoflagellates through time. Here the organic-walled cysts of 73 rare, poorly known or morphologically problematic marine dinoflagellate cyst species belonging to the orders Gymnodiniales (nine species) and Peridiniales (64 species) are reviewed, described and illustrated, and their stratigraphic ranges assessed. The names Echinidinium aculeatum and Echinidinium transparantum are validated herein. © 2019 Elsevier B.V.

The taxonomy of the dinoflagellate cyst-based genus Votadinium has been in need of revision. This was accomplished here by integrating morphology, LSU rDNA sequences, and cyst wall composition analyses through micro-Fourier transform infrared spectroscopy. Three new species, Votadinium pontifossatum, V. rhomboideum and V. reidii, were described as cyst stages of Protoperidinium paraoblongum, P. quadrioblongum, and P. steidingerae, respectively. A previously undescribed type of ornamentation was reported for V. pontifossatum. A fourth new species was assigned to V. concavum. Furthermore, Lejeunecysta psilodora Benedek (=Lejeunecysta psuchra Matsuoka), was re-described as V. psilodora and the holotype re-illustrated, as was done for the holotype of V. spinosum Reid. New illustrations were provided for V. elongatum and V. nanhaiense. LSU rDNA sequences of V. concavum revealed its placement in the Oceanica section of the genus Protoperidinium, supporting earlier evidence that the Oceanica section and the cyst based genus Votadinium form a monophyletic clade. Thus, Votadinium could be considered the cyst equivalent of the motile-defined Oceanica section. The cyst walls of Votadinium spinosum, V. calvum and V. pontifossatum are built from carbohydrate-based macromolecules with N-containing functional groups in agreement with the heterotrophic nature of their motile stage. Comparison with related genera Trinovantedinium and Quinquecuspis reveals that the species and genera can be separated based on cyst wall composition, supporting the phylogeny based on molecular data and/or ecological differences. Furthermore, Trinovantedinium applanatum spectra unexpectedly show an additional absorption at 1510 cm−1 indicating an aromatic group that is commonly reported for sporopollenin and not seen in dinoflagellate cysts so far. This study stabilizes the taxonomy of the cyst genus Votadinium, clarifies its relationship to the Oceanica section of Protoperidinium, and further supports the application of whole cyst wall chemistry in helping address problems in dinoflagellate cyst taxonomy and ecology.

Organic-walled resting cysts of planktonic dinoflagellates occur commonly in modern marine sediment where they represent, with rare exceptions, the only geologically preservable part of the life cycle. Although many species do not produce fossilizable resting cysts, upper Quaternary sediments contain a diverse cyst record that is used frequently for paleoenvironmental reconstruction and stratigraphic analysis. Reconstructions of past sea-surface conditions rely on an understanding of the distributions of dinoflagellate cysts in modern sediments linked to their respective environmental parameters, underpinned by sound taxonomy and standardized nomenclature. Stratigraphic studies additionally require knowledge of morphological details to distinguish extant from similar extinct taxa. Here, 51 dinoflagellate cyst species and two informal cyst morphotypes that are commonly encountered during routine palynological analysis of upper Quaternary marine sediments from the Northern Hemisphere are briefly described taxonomically and illustrated. In addition, their lowest stratigraphic occurrences are provided.

The gonyaulacean family Protoceratiaceae is characterised by five precingular plates. It currently encompasses the type genus Ceratocorys and the fossil genus Atopodinium. Fourteen strains of Ceratocorys, Pentaplacodinium, and Protoceratium were established from Malaysian and Hawaiian waters, and their morphologies were examined using light and scanning electron microscopy. Two new species, Ceratocorys malayensis sp. nov. and Pentaplacodinium usupianum sp. nov., were described from Malaysian waters. They share a Kofoidean plate formula of Po, Pt, 3ʹ, 1a, 6ʹʹ, 6C, 6S, 5ʹʹʹ, 1p, 1ʹʹʹʹ. Ceratocorys malayensis has a short first apical plate (1ʹ) with no direct contact with the anterior sulcal plate (Sa) whereas Pentaplacodinium usupianum had a parallelogram-shaped 1ʹ plate which often contacted the Sa plate. The genera Ceratocorys and Pentaplacodinium were emended accordingly to incorporate species bearing five or six precingular plates. The Protoceratium strain from Hawaii was morphologically similar to P. reticulatum, but differed in the lack of a ventral pore in plate 1′ and slight or lack of contact between plates 1′ and Sa, and is here designated as P. cf. reticulatum. The maximum-likelihood and Bayesian inference analyses based on SSU, LSU and ITS ribosomal DNA sequences revealed that these three genera are monophyletic and form a well-resolved group. Our results support Protoceratium and Pentaplacodinium as members of the family Protoceratiaceae, characterised by the presence of one anterior intercalary plate. Seven strains of Protoceratium cf. reticulatum, Ceratocorys malayensis and Pentaplacodinium usupianum were examined for yessotoxin production by LC-MS/MS but none produced a detectable amount of toxin.

Here we present new observations of Spiniferites alaskensis, a relatively rare species described from the Eemian of the Gulf of Alaska. We show that the species shows a gonyaulacacean tabulation: Po, 4´, 6´´, 6c,? s, 6´´´, 1p, 1´´´´. The surface is finely granulate to scabrate. The species bears characteristic processes: these are exclusively gonal, membranous, perforated and end distally in platforms with stumpy ends. We provide more detail as how this species compares to closely related species belonging to the genus Spiniferites.

The first chapter of this special issue introduces the proceedings of two workshops concerning the cystbased genus Spiniferites Mantell 1850. The historical background of the cyst-based genus Spiniferites, its closely related genera and the theca-based genus Gonyaulax Diesing 1866 is presented here.

We restudied the morphological complex comprising the cyst-based species Spiniferites elongatus/Spiniferites frigidus/Rottnestia amphicavata. We reviewed existing studies, and acquired new morphometric measurements of recent cysts from across the Northern Hemisphere, scanning electron microscopy (SEM) observations of cysts from Barents Sea surface sediments, and genetic analyses of cysts from the Beaufort Sea. The measurements suggest that populations and morphospecies cannot be distinguished based on morphometric criteria. Furthermore, sequential sediment trap samples from Hudson Bay reveal that morphological variation can occur at the same location over a few weeks, arguing against a uniform morphological response to environmental parameters. The SEM observations reveal a consistent gonyaulacacean tabulation (Po, 4′, 6′′, 6c, 5 s, *6′′′, 1p, 1′′′′). The small and large subunit ribosomal RNA genes and the internal transcribed spacer sequences obtained from differing cysts from the Beaufort Sea with morphologies attributable to the complex, including forms that correspond to Rottnestia amphicavata, were all identical and conform to those of Gonyaulax elongata from the Orkney Islands. The molecular analyses thus support the conclusion that the morphological variability is not reflected genetically and occurs within one species. Based on arguments against the generic attribution of amphicavata to Rottnestia, the continuum between the extreme ends of the morphological range, and the molecular data, we suggest Rottnestia amphicavata to be conspecific with Spiniferites frigidus, and both to be junior synonyms of Spiniferites elongatus. The morphometric data further indicate that Spiniferites ellipsoideus, an elongate cyst from the Miocene, can also be considered a junior synonym of Spiniferites elongatus. It is recommended to use two informal types in census work (i.e. Spiniferites elongatus – Beaufort morphotype for morphologies formerly assignable to Spiniferites frigidus/Rottnestia amphicavata, and Spiniferites elongatus – Norwegian morphotype for cysts with strongly reduced processes) to separate specimens at both extreme ends of the morphological spectrum from typical specimens of Spiniferites elongatus.

Dinoflagellates are part of the marine plankton and about 200 species produce a cyst (dinocyst) during their life cycle, these organic-walled sexually-produced cysts being fossilizable in sediments for hundreds of millions of years. Over the past 40–50 years, dinocysts have led to major advances on Mesozoic-Cenozoic research, in terms of biostratigraphy and paleogeogeography. Dinocyst taxonomy has then been continuously revised, with the tabulation being the main morphological link between living dinoflagellates and fossilized cysts. Over the Quaternary, and based on the principle of uniformitarianism (i.e. species ecology did not change through time), relationships between modern assemblages and present-day environmental factors controlling their distribution also allow for dinocyst-based quantitative reconstructions derived from transfer function calculations. This paper presents a non-exhaustive review of the dinocyst literature allowing the reader to get a perspective about how they were discovered and defined, but also how they are applied in (paleo)ecological studies according to the timescale considered allowing then to provide useful insights into the future climate change and its associated ecological repercussions.

A total of 31 surface sediment samples from 16 coastal inlets in five sounds of western Vancouver Island were investigated for dinoflagellate cysts and other palynomorphs. Well-preserved and abundant dinoflagellate cysts were recovered, including a total of 32 cyst taxa belonging to four families. Total dinoflagellate cyst concentrations vary two orders of magnitude, with concentrations between 2267 and 918,584 cysts g−1. The highest values were observed in samples from Tofino Inlet. Southern sites are characterized by cysts of autotrophic dinoflagellates, mainly Operculodinium centrocarpum sensu Wall & Dale 1966. Other abundant cysts of autotrophic dinoflagellates are Spiniferites spp. and cysts of Pentapharsodinium dalei. In general, other inlets in Quatsino, Kyuquot-Nootka and Clayoquot Sounds have lower total concentrations but have more cysts of heterotrophic dinoflagellates, mainly Round brown cysts, Brigantedinium spp., and Spiny brown cysts. Neroutsos Inlet is characterized by high concentrations of Arcellacean testate amoebae. Within inlets, cyst concentrations and assemblages vary. Near the heads of the inlets, concentrations are generally lower and assemblages are dominated by cysts of autotrophic dinoflagellates, mostly O. centrocarpum sensu Wall & Dale 1966. Concentrations of cysts produced by heterotrophic dinoflagellates and their proportions in the assemblages generally increase from the head to the mouth of each inlet. Measured sedimentary biogenic silica abundances (%Opal) have consistently higher values in Clayoquot Sound and lower values in Quatsino Sound. Within individual inlets, biogenic silica generally increases in the head to mouth direction. The trend in heterotrophic cyst abundances is similar. Correlations between total organic carbon (TOC), total nitrogen (TN) and terrestrial palynomorph concentrations in the sediments indicate that the organic material at sites near inlet heads are mainly derived from terrestrial input. A significant negative correlation between biogenic silica and TOC/TN ratio was observed in the dataset, but not between the total heterotrophic cyst concentrations and relative abundances of biogenic silica. Statistical analyses (PCA, RDA) indicate that the assemblages of dinoflagellate cysts and other palynomorphs, their spatial distributions, and sedimentary geochemical measurements are related to the regional environmental setting (e.g., latitudinal trends in weather, primary productivity, and upwelling) and local characteristics of the inlets (e.g., site location relative to freshwater input, inlet morphology and bathymetry, as well as possible anthropogenic influences). Process length variation of O. centrocarpum sensu Wall & Dale 1966 was measured and it is comparable to previous measurements in similar environmental settings, allowing seawater densities to be inferred. Cysts of Alexandrium spp. were found in most of the samples, with the highest abundance in the inlet heads of Kyuquot and Quatsino Sounds.

A new marine raphid diatom, Plagiolemma distortum Nézan, sp. nov. is described from plankton samples from the Atlantic Ocean, south Brittany (north-western France), where it was regularly observed, but never in high abundances. Cells have an unusual and complex shape under light microscopy (LM) depending on their position and orientation. The two valves are highly vaulted and narrow in width (transapical axis). Cells contain four complexly lobed plastids and a variable number of refractive granules without particular localization. In addition, capsules containing motile cells were observed. Ultrastructural details of the frustules were investigated using scanning electron microscopy (SEM). The girdle bands are simple. Each valve possesses a sigmoid raphe raised on a ridge and ending in external large openings with elaborate internal helictoglossae. Moreover, each valve displays outer slit-like foramina and inner rounded hymenes, external terminal minute holes (micropyles) arranged in a row at the poles. In addition, on each valve face, one to several short transverse median costae are observed, terminating far away from the valve edges. Morphological comparisons with closely related taxa show that P. distortum is a new species. A video clip of a moving cell is provided for better understanding of the cell shape. The formation and function of capsules are discussed as well as the species habitat. A phylogenetic study, based on nuclear small subunit (SSU) ribosomal DNA (rDNA) sequence data, which includes new sequences relative to Plagiolemma and Plagiotropis, was performed. Furthermore, some morphological details observed with SEM are included in an emended generic diagnosis of Plagiolemma.

The dinophyceaen genus Gymnodinium was established with the freshwater species G. fuscum as type. According to Thessen et al. (2012), there are 268 species, with the majority marine species. In recently published molecular phylogenies based on ribosomal DNA sequences, Gymnodinium is polyphyletic. Here, a new freshwater Gymnodinium species, G. plasticum, is described from Plastic Lake, Ontario, Canada. Two strains were established by incubating single cysts, and their morphology was examined with light microscopy and scanning electron microscopy. The cyst had a rounded epicyst and hypocyst with a wide cingulum and smooth surface. Vegetative cells were characterized by an elongated nucleus running vertically and a deep sulcal intrusion. The apical structure complex was horseshoe‐shaped and consisted of two pronounced ridges with a deep internal groove, encircling 80% of the apex. Small subunit ribosomal DNA (SSU rDNA), large subunit ribosomal DNA (LSU rDNA) and internal transcribed spacer (ITS) sequences were obtained from cultured strains. Molecular phylogeny based on concatenated SSU, LSU and ITS sequences supports the monophyly of the Gymnodiniales sensu stricto clade but our results suggest that many Gymnodinium species might need reclassification. Gymnodinium plasticum is closest to Dissodinium pseudolunula in our phylogeny but distant from the type species G. fuscum, as are the other gymnodiniacean taxa.

We investigate the cyst-theca relationship of Impagidinium caspienense. Through an incubation experiment, we succeeded in examining the motile stage. Additional molecular analysis of single-cyst PCR (LSU and SSU rDNA) reveal that the cyst is related to the species Gonyaulax baltica Ellegaard et al. (2002). The ability of this species to belong to two types of cyst-based genera (spiniferate and impagidinioid) suggests that environmental (particularly salinity) and not genetic factors explain the formation of both morphotypes by Gonyaulax baltica, which provides evidence for heterospory in this species. The affiliation to Gonyaulax baltica demonstrates that Impagidinium caspienense is not endemic to the Caspian Sea. The phylogenetic position of several other gonyaulacoid species is also documented: Impagidinium pallidum, Ataxiodinium choane, Pyxidinopsis psilata, Spiniferites belerius, and Spiniferites ramosus. The LSU and SSU rDNA based phylogenies suggest that the genera Impagidinium and Spiniferites are not monophyletic, and that Pyxidinopsis psilata and Ataxiodinium choane are close to Gonyaulax verior and Gonyaulax polygramma, respectively. In addition, this study accentuates the importance of cyst morphology in the classification of the Gonyaulacales. This article is protected by copyright. All rights reserved.

We present a record of dinoflagellate cyst assemblage composition, abundance, and morphology from the central Baltic Sea, spanning the late 19th to the early 21st centuries. Environmental time-series were analyzed in relation to changes in community structure and diversity as inferred from the sediment record, and average summer sea surface salinity (SSS) was reconstructed based on the average process length of Protoceratium reticulatum resting cysts. The reconstructed summer SSS was compared to instrumental data for a critical evaluation of this approach. The most abundant species in this record were P. reticulatum and Biecheleria baltica, and on average ten taxa were identified per sample. The cyst record of B. baltica indicated that although this species has been present in the Gotland Basin at least since the 1880s, its concentrations have increased significantly since the 1980s, possibly linked to eutrophication. Variations in assemblage composition and P. reticulatum cyst morphology reflected patterns of major, instrumentally recorded hydrographic and environmental changes in the Baltic Sea during the past century. The variability in microfossil relative abundances was best explained by the average spring SSS as well as by the average NO3 concentrations during spring and by the combined effects of average summer SSS and NAO variability. Reconstructed summer SSS and instrumental SSS showed notable differences, depending on the year and function applied for reconstruction. Although roughly reflecting the same patterns, the reconstructed values are offset when compared to instrumental measurements. We put forward suggestions for improvement of the process-length method and recommend using the reconstructed values as an indication of relative changes in past summer sea surface salinity, preferably as part of a multiproxy approach.

Escalera et al. (2018. Phycologia 57: 453–464) concluded that Gonyaulax hyalina and G. fragilis were the same species. Here, the morphologies of G. hyalina and G. fragilis were restudied in field samples from different parts of the World Ocean. Results showed that Escalera et al. did not observe G. fragilis, as all strains used in their study belong to one species, G. hyalina. In consequence, it is hereby proposed that the two taxa remain as separate species until further genetic studies are carried out. Additionally, the interpretation of the anterior sulcal plate as unique within gonyaulacoids is considered here inaccurate, as the plate pattern of both species is similar to other species of Gonyaulax, e.g. G. polygramma. We also show that both species may co-occur in the same sample. Their observation of an anterior intercalary plate in cultures of G. hyalina was confirmed in field samples.

The cosmopolitan, potentially toxic dinoflagellate Protoceratium reticulatum possesses a fossilizable cyst stage which is an important paleoenvironmental indicator. Slight differences in the internal transcribed spacer ribosomal DNA (ITS rDNA) sequences of P. reticulatum have been reported, and both the motile stage and cyst morphology of P. reticulatum display phenotypic plasticity, but how these morpho-molecular variations are related with ecophysiological preferences is unknown. Here, 55 single cysts or cells were isolated from localities in the Northern (Arctic to subtropics) and Southern Hemispheres (Chile and New Zealand), and in total 34 strains were established. Cysts and/or cells were examined with light microscopy and/or scanning electron microscopy. Large subunit ribosomal DNA (LSU rDNA) and/or ITS rDNA sequences were obtained for all strains/isolates. All strains/isolates of P. reticulatum shared identical LSU sequences except for one strain from the Mediterranean Sea that differs in one position, however ITS rDNA sequences displayed differences at eight positions. Molecular phylogeny was inferred using maximum likelihood and Bayesian inference based on ITS rDNA sequences. The results showed that P. reticulatum comprises at least three ribotypes (designated as A, B, and C). Ribotype A included strains from the Arctic and temperate areas, ribotype B included strains from temperate regions only, and ribotype C included strains from the subtropical and temperate areas. The average ratios of process length to cyst diameter of P. reticulatum ranged from 15% in ribotype A, 22% in ribotype B and 17% in ribotype C but cyst size could overlap. Theca morphology was indistinguishable among ribotypes. The ITS-2 secondary structures of ribotype A displayed one CBC (compensatory change on two sides of a helix pairing) compared to ribotypes B and C. Growth response of one strain from each ribotype to various temperatures was examined. The strains of ribotypes A, B and C exhibited optimum growth at 15 °C, 20 °C and 20–25 °C, respectively, thus corresponding to cold, moderate and warm ecotypes. The profiles of yessotoxins (YTXs) were examined for 25 strains using liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS). The parent compound yessotoxin (YTX) was produced by strains of ribotypes A and B, but not by ribotype C strains, which only produced the structural variant homoyessotoxin (homoYTX). Our results support the notion that there is significant intra-specific variability in Protoceratium reticulatum and the biogeography of the different ribotypes is consistent with specific ecological preferences. publishedVersion

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.

Lycopodium clavatum marker-grain tablets are often added before palynological processing to calculate the absolute abundance of organic-walled microfossils in sediments. In this study we investigate the reproducibility of dinoflagellate cyst concentrations by performing nine different tests: varying dinoflagellate cyst/ Lycopodium spore ratios, sample weights, centrifuge speeds and times, sonication times, and mesh sizes; manually powdering the sediment using a mortar and pestle prior to processing, using a water jug instead of squirt bottles during sieving, decanting over a 6 μm sieve and adding Lycopodium tablets at the end. Previous studies have reported loss of Lycopodium spores during processing. In this study we investigate sources of this loss by microscopically analyzing residue on stir sticks and sieves, and what is lost through the sieves and decanting. We document an average loss of 8.2 % of Lycopodium spores during processing, with the greatest loss occurring through the fine sieve and resulting in only a 4.8% overestimation of the cyst concentration. Results using powdered sediment and sonicating for more than 5 min are less reproducible. Large cyst/ Lycopodium spore ratios were found to have higher cyst concentrations and standard deviations, thus we recommend ratios of less than five, and ideally ratios between 0.5 and 2 to facilitate counting.

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 spin...

Centrodinium punctatum is a fusiform dinoflagellate with a global marine distribution. Due to a close phylogenetic relationship of one C. punctatum strain to Alexandrium species, toxin production of this C. punctatum strain was assessed using liquid chromatography coupled to tandem mass spectrometry. The paralytic shellfish toxin (PST) profile of C. punctatum was dominated by six analogs, i.e. STX (30%), GTX-1 (20%) and neoSTX (24%), followed by GTX-2 (9%), GTX-4 (9%) and GTX-3 (8%); deoxy-STX was also putatively identified while no gymnodimines, spirolides or goniodomins were detected. This is the first record of C. punctatum producing saxitoxins. The estimated cellular toxicity was rather elevated, between 91 and 212 pg cell−1 (or 259 and 601 fmol cell−1). When considering the toxicity equivalent factors, results suggest that this species can produce high cellular toxicity compared to other STX-producing dinoflagellates. Morphological details of the sulcal area and the hypotheca of Centrodinium punctatum were re-examined by scanning electron microscopy (SEM); this revealed that in the sulcal area, the left posterior sulcal plate (Ssp) is larger and longer than the left posterior sulcal plate and extended into the hypotheca. Based on the morphological observation, a revised interpretation of the sulcus and hypotheca is proposed.

The geographical distribution of dinoflagellate cysts was investigated in palynologically treated surface sediments from the South China Sea (SCS) to understand the driving environmental factors associated with specific taxa. The western SCS generally has higher total cyst concentrations (>300 cysts g−1) than the eastern region ( 1000 cysts g−1) occur off southern Vietnam, whereas the lowest cyst concentrations are off Luzon. The ratio of heterotrophic to autotrophic taxa has inverse distributional patterns to total cyst concentrations, and is likely to be related to an increase in relative abundances of autotrophic taxa when nutrient inputs increase. Brigantedinium spp., Selenopemphix nephroides, and Stelladinium reidii have their highest relative abundances and concentrations off Borneo. Their concentrations are significantly positively correlated with January sea-surface temperature (SST-Jan). In contrast, concentrations of Selenopemphix undulata, Spiniferites hyperacanthus, Dapsilidinium pastielsii and Operculodinium?longispinigerum are negatively correlated with SST-Jan. Lejeunecysta sabrina, cysts of Protoperidinium spp., Votadinium spp., Quinquecuspis concreta and Selenopemphix quanta are positively correlated with chlorophyll-a (chl-a) concentrations and are found in the high primary productivity regions of the SCS. Total Impagidinium, Impagidinium aculeatum, Impagidinium paradoxum, Impagidinium patulum, Nematosphaeropsis labyrinthus, and Polysphaeridium zoharyi are positively correlated with water depth. Their highest abundances are recorded in the northern slope-deep basin that is influenced by the Kuroshio Current, and this cyst assemblage indicates an open-ocean environment.

Dinoflagellate resting cysts with rare exception produce the only discrete link between the biology of extant dinoflagellate species and their fossil record. The geological preservability of such cysts allows them to be used for quantitative paleoecological reconstructions, especially in the Quaternary, and for biostratigraphy and the calibration of molecular clocks with the geological record. This contribution reviews and updates the taxonomy of 27 uncommon dinoflagellate cyst species and morphotypes belonging to the orders Gonyaulacales and Suessiales with occurrences in upper Quaternary marine sediments of the Northern Hemisphere. Comparative descriptions and illustrations are provided along with the biological affinity of each taxon where known and lowest stratigraphic occurrence.

Investigation of phytoplankton from East China Sea of the Pacific Ocean, offshore Reunion 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.

Species in the genera Hexasterias and Halodinium have been recorded over the last decades as acritarchs in palynological and/or plankton studies. In paleoenvironmental studies, these resting stages are often interpreted as indicators of freshwater input. The biological affinity of these genera has never been definitely established. Here, a new species, Halodinium verrucatum sp. nov., is described and molecular evidence (single specimen SSU and LSU rDNA sequencing) reveals that both this new species and Hexasterias problematica, collected from sediment samples in the Skagerrak and Baltic Sea, are resting stages of prorodontid ciliates. Additionally, infrared spectroscopic analysis (micro-FTIR) of Hexasterias problematica and Halodinium spp. specimens indicates a carbohydrate-based composition of the cyst wall with evidence for nitrogen-containing functional groups. A similar composition is recorded for tintinnid loricae, which further supports the placement of Hexasterias and Halodinium as ciliate cysts, and the composition is consistent with the heterotrophic nature of ciliates. The morphologically similar species Radiosperma corbiferum has a comparable composition, suggesting a similar ciliate affinity and indicating the utility of micro-FTIR in understanding acritarch affinity. Hexasterias problematica typically occurs in coastal waters from temperate to arctic regions. Halodinium verrucatum sp. nov. is observed in temperate estuarine sediments in the northern hemisphere.

The genus Gymnodinium includes many morphologically similar species, but molecular phylogenies show that it is polyphyletic. Eight strains of Gymnodinium impudicum, Gymnodinium dorsalisulcum and a novel Gymnodinium-like species from Chinese and Malaysian waters and the Mediterranean Sea were established. All of these strains were examined with light microscopy, scanning electron microscopy and transmission electron microscopy. SSU, LSU and internal transcribed spacers rDNA sequences were obtained. A new genus, Wangodinium, was erected to incorporate strains with a loop-shaped apical structure complex (ASC) comprising two rows of amphiesmal vesicles, here referred to as a new type of ASC. The chloroplasts of Wangodinium sinense are enveloped by two membranes. Pigment analysis shows that peridinin is the main accessory pigment in W. sinense. Wangodinium differs from other genera mainly in its unique ASC, and additionally differs from Gymnodinium in the absence of nuclear chambers, and from Lepidodinium in the absence of Chl b and nuclear chambers. New morphological information was provided for G. dorsalisulcum and G. impudicum, e.g., a short sulcal intrusion in G. dorsalisulcum; nuclear chambers in G. impudicum and G. dorsalisulcum; and a chloroplast enveloped by two membranes in G. impudicum. Molecular phylogeny was inferred using maximum likelihood and Bayesian inference with independent SSU and LSU rDNA sequences. Our results support the classification of Wangodinium within the Gymnodiniales sensu stricto clade and it is close to Lepidodinium. Our results also support the close relationship among G. dorsalisulcum, G. impudicum, and Barrufeta. Further research is needed to assign these Gymnodinium species to Barrufeta or to erect new genera.