New morphological data and molecular phylogeny of the benthic dinoflagellate Pseudothecadinium campbellii (Dinophyceae, Gonyaulacales)
Introduction
The monotypic genus Pseudothecadinium Hoppenrath and Selina, 2006, with P. campbellii as type species, was described from plankton of shallow-water from the Lunskiy Bay in the Sea of Okhotsk (Hoppenrath and Selina 2006). Earlier, this species has been recorded from plankton of the estuarine region of Gales Greek, North Carolina, under the invalidly published name Thecadinium aureum (nomen nudum; Campbell 1973) and from the Gulf of Mexico as ‘unidentified thecate #2’ (Steidinger and Williams 1970). Pseudothecadinium campbellii showed some similarity in cell morphology (incomplete precingular plate series) to Thecadinium kofoidii (Herdman) Larsen and Thecadiniopsis tasmanica Croome, Hallegraeff and Tyler, and hence, together with the latter species, it was tentatively assigned to the family Thecadiniaceae of the order Gonyaulacales (Hoppenrath and Selina 2006). Apart from morphological differences, the above species differed in their ecology: Thecadiniopsis tasmanica is a freshwater planktonic species, while T. kofoidii is marine sand-dwelling (Croome et al. 1987; Hoppenrath 2000). Pseudothecadinium campbellii was first recorded in coastal plankton (Campbell 1973; Steidinger and Williams 1970) and described from plankton of a shallow lagoon (Hoppenrath and Selina 2006). Long-term studies of benthic dinoflagellates in Peter the Great Bay, Sea of Japan, showed that P. campbellii is a permanent component of the epiphytic community and sometimes reaches high abundances in sublittoral sands (Selina and Levchenko 2011; Selina et al. 2014).
In the classification by Fensome et al. (1993), T. kofoidii and Thecadiniopsis tasmanica were placed in the order Gonyaulacales, but family uncertain. Later, the three genera were separated into a distinct group, the Thecadinioide (Hoppenrath 2017). The phylogenetic relationships and position within the group Thecadinioide remain obscure. In Adl et al. (2019) these genera were classified as “incertae sedis Dinoflagellate”. However, so far, no molecular data are available for Pseudothecadinium. In this study, we determined and analyzed the small subunit ribosomal RNA gene sequences (18S rRNA), and the D1/D2 and D8/D10 regions of the large subunit (28S rRNA) of P. campbellii. Data on the morphology of the apical pore complex, cingular and sulcal areas of P. campbellii were specified and added.
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Cell isolation and culturing
Investigations were carried out using clonal cultures of Pseudothecadinium campbellii (strains MBRU_Ps1, MBRU_Ps2, MBRU_Ps3) and field samples. Cells of P. campbellii for establishment of cultures were isolated from the green alga Codium fragile (Suringar) Hariot that was collected on 27 November 2014 in the Bosfor Vostochny Strait (43°04′24″N, 131°57′34″E) of Peter the Great Bay, Sea of Japan at about 1 m depth. In addition, field samples from epiphytic assemblage at same station on 27
Morphology of Russian population of Pseudothecadinium campbellii (Figs. 1–3)
Cells laterally flattened, oval or obovate in lateral view (Figs. 1, 2a–c), 33.6–54.5 μm (43.4 ± 5.3, n = 50) long, 26.1–45.8 μm (34.6 ± 4.4, n = 50) deep, with a length/depth ratio of 1.1–1.4 (1.25 ± 0.06, n = 50). Nucleus oval, at dorsal side of hypotheca (Fig. 1a, b). Chloroplasts numerous, yellow-brown, radiating from cell center. In some cells small rounded greenish granules located in parietal part of epitheca and hypotheca (Fig. 1a). Left part of epitheca almost two times smaller
Discussion
Light and scanning electron microscopic observations of cultured cells revealed all species-specific characteristics of Pseudothecadinium campbellii: (1) incomplete precingular plate series, (2) apical intercalary plates separated from each other, and (3) ventral intercalary plate with a pore (Hoppenrath and Selina 2006). One more characteristic feature was specified — the antapical plate was not entirely on the right lateral side of the hypotheca, a small part continued onto the left side. The
Author contributions
K.V.E. and M.S.S. conceptualised the project; M.S.S. collected samples; K.V.E. and M.S.S. carried out the research; K.V.E. performed molecular-phylogenetic analysis; M.S.S. performed electron microscopy analysis; K.V.E., M.S.S. and M.H. wrote the manuscript. All authors read and approved the final manuscript.
Funding
Financial support was provided by the Dalnii Vostok program (project 18-4-050); and Ministry of Science and High Education Program for support of bioresource collections for maintenance of microalgae cultures.
References (45)
- et al.
Basic local alignment search tool
J. Mol. Biol.
(1990) - et al.
Ostreopsis cf. siamensis and Ostreopsis cf. ovata from the Atlantic Iberian Peninsula: morphological and phylogenetic characterization
Harmful Algae
(2013) - et al.
A review of arthropod phylogeny: new data based on ribosomal DNA sequences and direct character optimization
Cladistics
(2000) - et al.
Phylogeny of the arachnid order Opiliones (Arthropoda) inferred from a combined approach of complete 18S and partial 28S ribosomal DNA sequences and morphology
Mol. Phylogen. Evol.
(1999) - et al.
Morphological and genetic analysis of the Coolia monotis species complex with the introduction of two new species, Coolia santacroce sp. nov. and Coolia palmyrensis sp. nov. (Dinophyceae)
Harmful Algae
(2015) - et al.
Discovery of a new clade nested within the genus Alexandrium (Dinophyceae): morpho-molecular characterization of Centrodinium punctatum (Cleve) FJR Taylor
Protist
(2019) - et al.
Molecular data and the evolutionary history of dinoflagellates
Eur. J. Protistol.
(2004) - et al.
Seasonal dynamics and spatial distribution of epiphytic dinoflagellates in Peter the Great Bay (Sea of Japan) with special emphasis on Ostreopsis species
Harmful Algae
(2014) - et al.
Molecular and phylogenetic characterization of Ostreopsis (Dinophyceae) and the description of a new species, Ostreopsis rhodesae sp. nov., from a subtropical Australian lagoon
Harmful Algae
(2016) - et al.
Molecular phylogeny of the benthic dinoflagellate genus Amphidiniopsis and its relationships with the family Protoperidiniaceae
Protist
(2016)