Search

The Prorocentrales are a unique group of dinophytes based on several apomorphic traits, but species delimitation is challenging within the group. Prorocentrum triestinum was described by Josef Schiller in 1918 as an important bloom-forming species from Trieste (Mediterranean, Adriatic Sea) with a conspicuous asymmetric outline and a small, asymmetrically located subapical spine. All subsequent records under this name fail to conform to Schiller's original description. These inconsistencies have their origin in John Dodge's 1975 revision of Prorocentrum, which placed Prorocentrum redfieldii, a more symmetrical, slender species with a long apical spine, into synonymy under P. triestinum. To clarify this confusion, we collected samples at the type locality of P. triestinum in Trieste and established a strain that is morphologically consistent with the protologue and suitable for use in epitypification. Morphology and rRNA sequence data of this strain were compared with four new strains identified as P. redfieldii from the Mediterranean Sea and the North Atlantic Ocean. Cells of P. triestinum had an asymmetric outline in lateral view and a small, dorso-subapical spine. These features, which are readily resolved by light microscopy, were distinct from those of the nearly symmetrical and slender cells of P. redfieldii, which had a long, apically located spine. The species are nevertheless closely related and share an identical architecture of the periflagellar area with a distinctive, largely reduced accessory pore together with a very small platelet 7. This apomorphy clearly differentiates both species from other species of Prorocentrum. Both species differ in their primary rRNA sequences, and ITS and LSU sequence differences will enable them to be distinguished in future meta-barcoding studies. The present study demonstrates that P. triestinum and P. redfieldii are distinct species and thus contributes to a reliable biodiversity assessment of Prorocentrum. HIGHLIGHTS Prorocentrum triestinum is characterised molecularly for the first time and delimited from P. redfieldii. The identity of important bloom-forming species is clarified. Structural details of the periflagellar area are described. [ABSTRACT FROM AUTHOR]

Peridinium cinctum is a common freshwater dinophyte with a long history of research. Erich Lindemann was the first to assess intraspecific variability in this species focusing on plate pattern variation. Since then, this issue has been neglected but with the application of DNA sequence diagnostics, a combination of morphological and molecular characters may enable taxonomic delimitations. Our aim was to identify distinct morphotypes using plate pattern as the main characteristic and then compare them to the geographic occurrence of particular ribotypes (as inferred from sequences of the Internal Transcribed Spacer: ITS) in samples from Central Europe. Approximately 200 observations were carried out under the inverse light microscope for each of a total of 15 strains. We observed two main variations from the abundant plate pattern in P. cinctum, namely an unusual position of the 2a plate and the irregular shape of the 1a plate. In 88 (predominantly clonal) strains, we identified five different ribotypes (submitted as 71 new GenBank entries) which had no clear correlation to the defined morphotypes and/or spatial occurrences. In four cases, we detected two distinct ribotypes at the same locality. However, samples collected south of the Danube River presented a different predominant morphotype from the rest of the samples, thus implying a potential biogeographic signal as inferred from morphology. In general, there is morphological and molecular variability in P. cinctum, which is under-studied and which may uncover geographic or ecological correlations or even the existence of cryptic species. [ABSTRACT FROM AUTHOR]

Amphidomais an old though poorly studied thecate dinophyte that has attracted attention recently as a potential producer of azaspiracids (AZA), a group of lipophilic phycotoxins. A new species,Amphidoma parvula, sp. nov. is described from the South Atlantic shelf of Argentina. With a Kofoidean thecal plate pattern Po, cp, X, 6′, 6′′, 6C, 5S, 6′′′, 2′′′′, the cultivated strain H-1E9 (from which the type material ofAm. parvula, sp. nov. was prepared) shared the characteristic plate arrangement ofAmphidomaeach with six apical, precingular and postcingular plates.Amphidoma parvula, sp. nov. differs from other species ofAmphidomaby a characteristic combination of small size (10.7–13.6 µm in length), ovoid shape, high length ratio between epitheca and hypotheca, and small length ratio between apical and precingular plates. Other morphological details, such as the number and arrangement of sulcal plates and the fine structure of the apical pore complex support the close relationship betweenAmphidomaand the other known genus of Amphidomataceae,Azadinium. However,Am. parvula, sp. nov. lacks a ventral pore, a characteristically structured pore found in all contemporary electron microscopy studies ofAmphidomaandAzadinium. As inferred from liquid chromatography coupled with tandem mass spectrometry,Am. parvula, sp. nov. did not produce AZA in measurable amounts. Molecular phylogenetics confirmed the systematic placement ofAm. parvula, sp. nov. inAmphidoma(as sister species ofAmphidoma languida) and the Amphidomataceae. The results of this study have improved the knowledge of Amphidomataceae biodiversity. [ABSTRACT FROM AUTHOR]

The phylogenetic relationships of Scrippsiella sensu lato (including cyst taxa such as Calcigonellum, Calciodinellum , and Pernambugia ) were investigated based on sequences from the ribosomal 5.8S rRNA and the Internal Transcribed Spacers ITS1 and ITS2, including interpretations on morphology and distribution. To attach importance to the cyst diversity present in calcareous dinoflagellates, a segregation of Scrippsiella sensu lato into four well-recognizable and monophyletic groups is proposed, corresponding to more- or less-established taxonomic units: (i) Calciodinellum (including Calcigonellum and a few species assigned to Scrippsiella ), (ii) Pernambugia (presumptively including Lebessphaera ), (iii) S. precaria and S. ramonii , and (iv) Scrippsiella sensu stricto comprising largely the S. trochoidea species complex. The phylogenetic relationships among these four groups are not sufficiently resolved. Molecular data suggest the existence of numerous cryptic taxa showing molecular, but not morphological, variation (especially in Scrippsiella sensu stricto ). Closely related strains have a wide range of distribution and occur (at least partly) sympatrically in cold through to tropical seas of the world. [ABSTRACT FROM AUTHOR]