Taxonomic re-examination of the toxic armored dinoflagellate Pyrodinium bahamense Plate 1906: Can morphology or LSU sequencing separate P. bahamense var. compressum from var. bahamense?

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.This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/harmful-algae/,The publisher has made available a Corrigendum for Figure 3. It can be found in Harmful Algae, Vol. 42, February 2015, Pages 71-72. doi:10.1016/j.hal.2014.12.002. It may also be viewed here as a secondary "Corrigendum" file.Keywords: Saxitoxins, LSU, Biometry, Theca, Thermophile, Cys

Pentaplacodinium saltonense gen. et sp. nov. (Dinophyceae) and its relationship to the cyst-defined genus Operculodinium and yessotoxin-producing Protoceratium reticulatum

Strains of a dinoflagellate from the Salton Sea, previously identified as Protoceratium reticulatum and yessotoxin producing, have been reexamined morphologically and genetically and Pentaplacodinium saltonense n. gen. et sp. is erected to accommodate this species. Pentaplacodinium saltonense differs from Protoceratium reticulatum (Claparède et Lachmann 1859) Bütschli 1885 in the number of precingular plates (five vs. six), cingular displacement (two widths vs. one), and distinct cyst morphology. Incubation experiments (excystment and encystment) show that the resting cyst of Pentaplacodinium saltonense is morphologically most similar to the cyst-defined species Operculodinium israelianum (Rossignol, 1962) Wall (1967) and O. psilatum Wall (1967). Collections of comparative material from around the globe (including Protoceratium reticulatum and the genus Ceratocorys) and single cell PCR were used to clarify molecular phylogenies. Variable regions in the LSU (three new sequences), SSU (12 new sequences) and intergenic ITS 1-2 (14 new sequences) were obtained. These show that Pentaplacodinium saltonense and Protoceratium reticulatum form two distinct clades. Pentaplacodinium saltonense forms a monophyletic clade with several unidentified strains from Malaysia. LSU and SSU rDNA sequences of three species of Ceratocorys (C. armata, C. gourreti, C. horrida) from the Mediterranean and several other unidentified strains from Malaysia form a well-supported sister clade. The unique phylogenetic position of an unidentified strain from Hawaii is also documented and requires further examination. In addition, based on the V9 SSU topology (bootstrap values >80%), specimens from Elands Bay (South Africa), originally described as Gonyaulax grindleyi by Reinecke (1967), cluster with Protoceratium reticulatum. The known range of Pentaplacodinium saltonense is tropical to subtropical, and its cyst is recorded as a fossil in upper Cenozoic sediments. Protoceratium reticulatum and Pentaplacodinium saltonense seem to inhabit different niches: motile stages of these dinoflagellates have not been found in the same plankton sample

Introduction to Spiniferites Mantell 1850 special issue

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 her

Should Gonyaulax hyalina and Gonyaulax fragilis (Dinophyceae) remain two different taxa?

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

Reply to: Comments on Mertens et al. (2022): the taxonomic identity of Micracanthodinium setiferum (Lohmann) Deflandre (Dinophyceae incertae sedis) remains elusive, and its epitypification is not achieved

We here epitypify Micracanthodinium setiferum by selecting a previously published micrograph from the Ionian Sea, and we typify both formae. We also clarify several points that were raised by our critics

A morphological comparison of two cladopyxidacean dinoflagellates: the extant Micracanthodinium setiferum and the fossil Cladopyxidinium saeptum (Dinophyceae, Gonyaulacales)

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

Fensomea setacea, gen. & sp. nov. (Cladopyxidaceae, Dinophyceae), is neither gonyaulacoid nor peridinioid as inferred from morphological and molecular data

Dinophyte evolution is essentially inferred from the pattern of thecal plates, and two different labelling systems are used for the important subgroups Gonyaulacales and Peridiniales. The partiform hypotheca of cladopyxidoid dinophytes fits into the morphological concepts of neither group, although they are assigned to the Gonyaulacales. Here, we describe the thecate dinophyte Fensomea setacea, gen. & sp. nov., which has a cladopyxidoid tabulation. The cells displayed a Kofoidean plate formula APC, 3′, 4a, 7″, 7C, 6S, 6′′′, 2′′′′, and slender processes were randomly distributed over the echinate or baculate surface. In addition, we obtained rRNA sequences of F. setacea, gen. & sp. nov., but dinophytes that exhibit a partiform hypotheca did not show a close relationship to Gonyaulacales. Character evolution of thecate dinophytes may have progressed from the ancestral state of six postcingular plates, and two more or less symmetrically arranged antapical plates, towards patterns of only five postcingular plates (Peridiniales) or more asymmetrical configurations (Gonyaulacales). Based on our phylogenetic reconsiderations the contact between the posterior sulcal plate and the first postcingular plate, as well as the contact between an antapical plate and the distalmost postcingular plate, do not represent a rare, specialized gonyaulacoid plate configuration (i.e., the partiform hypotheca of cladopyxidoid dinophytes). Instead, these contacts correspond to the common and regular configuration of peridinioid (and other) dinophytes

Morpho-molecular and spectroscopic characterization of the freshwater dinoflagellate Unruhdinium penardii var. robustum (Kryptoperidiniaceae, Peridiniales), blooming in the Loir River, France

A freshwater dinoflagellate formed extensive red tides in the Loir River, France in September 2018. Morphological observations using light microscopy and field emission scanning electron microscopy identified the causative organism as the "dinotom" Unruhdinium penardii var. robustum, with a tabulation of Po, x, 4', 0a, 6 '', 5c (or t+4c), 5s, 5 ''', 2 ''''. The thecal plate overlap of the variety is documented for the first time. Division cysts were also observed in the plankton assemblage. Sequences obtained from the vegetative cells of small subunit (SSU) and large subunit (LSU) ribosomal DNA (rDNA) are identical to previously published sequences from Japan. This is the first unambiguous identification from French waters of this species and its variety. A SSU rDNA sequence is also reported for the diatom endosymbiont, which is close to the diatom genus Discostella. Fourier transform infrared spectroscopic analysis showed that division cysts and thecae of U. penardii var. robustum are cellulose-like, but with a higher degree of cross-linking than in microcrystalline cellulose and with a more complex macromolecular buildup