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Protoperidinium claudicans is a planktonic, heterotrophic, bioluminescent dinoflagellate species commonly found in neritic waters. It has long been considered to display phenotypic variation in its second anterior intercalary plate, which could vary between quadra, penta and hexa. The equivalent spinose, cordate cyst goes under the name of Votadinium spinosum. Here we perform incubation experiments with cysts from France, Canada, China and Japan, which demonstrate that P. claudicans forms a species complex, with at least two ribotypes with a penta configuration (P. claudicans) and one with a quadra configuration (P. carriae sp. nov.). A fossil-based cyst, V. multispinosum sp. nov., is described as the equivalent of P. carriae. Molecular phylogenetics using large subunit ribosomal DNA supports these observations. The cyst–theca relationships for Votadinium psilodora and another, undescribed, cordate, spineless Votadinium species are also reported from China. Macromolecular analyses of the cyst wall of V. multispinosum reveal it is comprised of a protein-rich carbohydrate compound. We show that this compound is not uncommon in dinoflagellate and ciliate cysts and that it is unlikely to preserve very well upon sedimentation and burial. [ABSTRACT FROM AUTHOR]

Attenuated total reflection (ATR) microscope Fourier transform infrared (micro‐FTIR) spectroscopy was used to investigate the dinosporin composition in the walls of modern, organic‐walled dinoflagellate resting cysts (dinocysts). Variable cyst wall compositions were observed, which led to the erection of four spectrochemical groups, some with striking similarities to other resistant biomacromolecules such as sporopollenin and algaenan. Furthermore, possible proxies derivable from the spectrochemical composition of modern and fossil dinocysts were discussed. The color of the dinocyst walls was reflected in the spectral data. When comparing that color with a standard and the results of a series of bleaching experiments with oxidative agents, eumelanin was assigned as a likely pigment contributing to the observed color. Following this assignment, the role of eumelanin as an ultraviolet sunscreen in colored dinocysts was hypothesized, and its implications on the autofluorescence and morphological preservation of dinocysts were further discussed. Unlike what had previously been assumed, it was shown that micro‐FTIR data from dinocysts cannot be used to unambiguously infer trophic affinities of their associated cells. Finally, using methods with high spatial resolutions (synchrotron transmission micro‐FTIR and optical photothermal infrared spectroscopy), it was shown that dinocyst wall layers are chemically homogenous at the probed scales. This study fills a large knowledge gap in our understanding of the chemical nature of dinocyst walls and has nuanced certain assumptions and interpretations made in the past. [ABSTRACT FROM AUTHOR]

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. Graphical Abstract [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The taxonomy of the dinoflagellate cyst-based genus Votadinium has been in need of revision. This is accomplished here by integrating morphology, large subunit (LSU) rDNA sequences, and cyst wall composition analyses through micro-Fourier transform infrared spectroscopy. Three new species, Votadinium pontifossatum, V. rhomboideum and V. reidii, are described as cyst stages of Protoperidinium paraoblongum, P. quadrioblongum, and P. steidingerae, respectively. A previously undescribed type of ornamentation is reported for V. pontifossatum. A fourth new species is assigned to V. concavum. Furthermore, Lejeunecysta psilodora Benedek (= Lejeunecysta psuchra Matsuoka), is re-described as V. psilodora and the holotype re-illustrated, as is done for the holotype of V. spinosum Reid. New illustrations are provided for V. elongatum and V. nanhaiense. LSU rDNA sequences of V. concavum reveal 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 a 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. [ABSTRACT FROM AUTHOR]

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 Vøring 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. [ABSTRACT FROM AUTHOR]

Highlights • Halodinium verrucatum sp. nov. is described, Hexasterias problematica is emended. • LSU and SSU rDNA is obtained for Halodinium verrucatum and Hexasterias problematica. • Molecular phylogeny and DAPI-staining demonstrate these are ciliate resting cysts. • micro-FTIR of resting cysts and tintinid loricae supports this affiliation. • The distribution and ecology of both palynomorphs is discussed. Abstract 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. [ABSTRACT FROM AUTHOR]

The dinoflagellate genus Bysmatrum encompasses five epibenthic or tide-pool species and has been characterized by separated anterior intercalary plates. In the present study, we obtained six strains of Bysmatrum from the South China Sea and French Atlantic coast by isolating single cells/cysts from plankton and sediment samples. All strains were examined with light microscopy and scanning electron microscopy. Based on morphological observations, three strains were identified as Bysmatrum subsalsum, characterized by the elongated and rectangular first and a hexagonal second anterior intercalary plate. They differ from each other in the number of sulcal lists and the configuration of the first anterior intercalary plate. One strain was identified as Bysmatrum gregarium and the other two as Bysmatrum granulosum. The cyst-theca relationship of B. subsalsum from the French Atlantic was established by incubation of the cyst, and the geochemical composition of the cyst wall was measured through micro-Fourier transform infrared spectroscopy. Bysmatrum subsalsum from Malaysia shows a bright red stigma in the sulcal area under light microscopy, which was confirmed with transmission electron microscopy: it was identified as a type B eyespot. Small subunit ribosomal DNA (SSU rDNA), partial large subunit ribosomal DNA (LSU rDNA) and internal transcribed spacer (ITS) sequences were obtained from all six strains. The maximum likelihood and Bayesian inference analysis based on concatenated SSU, ITS and LSU sequences revealed that Bysmatrum is monophyletic and nested within Peridiniales. Our strains of B. subsalsum form a new ribotype in the molecular phylogeny (designated as ribotype B). The genetic distance based on ITS sequences among Bysmatrum species ranged from 0.34 to 0.47 and those genetic distances at the intraspecific level of B. subsalsum could reach 0.41, supporting the possibility of hidden crypticity within B. subsalsum. [ABSTRACT FROM AUTHOR]

The resting cysts of the benthic dinoflagellate Prorocentrum leve from a natural reservoir in Gujan-Mestras (Gironde, France) were described in this study. The incubated urn-shaped cysts gave rise to cells of P. leve. Morphological observations through light microscopy and scanning electron microscopy, particularly of the periflagellar platelets, combined with large subunit ribosomal DNA sequences obtained through single-cell analysis confirm their affinity to the species P. leve. The cysts were characterized by a specific shape and the presence of an anterior plug. This is the first conclusive evidence for fossilizable resting stages within the Prorocentrales, one of the major orders within the Dinophyceae. Palynological treatments show that the cysts and endospores withstand hydrochloric and hydrofluoric acids. Micro-Fourier transform infrared analysis on single specimens suggests that the composition of the endospore is cellulosic and the cyst wall a more robust, noncellulosic β-glucan. The spectra overall are similar to other published spectra of resting cysts from autotrophic, planktonic dinoflagellates. [ABSTRACT FROM AUTHOR]