Placoneis asymmetricus Glushchenko, Kezlya, Asie du Sud-Est, Kulikovskiy & Kociolek 2022, sp. nov.
Creators: name: Kezlya, Elena
name: Glushchenko, Anton
name: Kociolek, John Patrick
name: Maltsev, Yevhen
name: Genkal, Sergey
name: Kulikovskiy, Maxim
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Chromista
Ochrophyta
Bacillariophyceae
Naviculales
Naviculaceae
Placoneis
Placoneis asymmetricus

description: Placoneis asymmetricus Glushchenko, Kezlya, Kulikovskiy & Kociolek, sp. nov.
(Figs 2-4)
HOLOTYPE. — Vietnam. Đồng Nai Province, Cát Tiên National Park, from soil sampled at Đồng Nai riverside, 11°26’05.6”N, 107°25’44.8”E, 03.VI.2019, E.S. Gusev & E.M. Kezlya, slide no. 06728 (oxidized material of cultured strain VP57). Deposited in the collection of Maxim Kulikovskiy at the Herbarium of the Institute of Plant Physiology, Russian Academy of Science, Moscow, Russia (Fig. 2P).
ISOTYPE. — Same data as holotype, slide no. 06728a. Deposited in the collection of the Main Botanical Garden of the Russian Academy of Science, Moscow, Russia (MHA).
TYPE LOCALITY. — Vietnam. Đồng Nai Province, Cát Tiên National Park, Đồng Nai riverside, 11°26’05.6”N, 107°25’44.8”E.
ETYMOLOGY. — The specific epithet refers to the typical asymmetry of the valves of this species.
SEQUENCE DATA. — Nuclear-encoded SSU rDNA partial sequence (GenBank accession: MW 979509), plastid gene rbc L partial sequence (GenBank accession: MW 987572).
DISTRIBUTION. — So far only known from the type locality.
DESCRIPTION
LM (Fig. 2)
Cells solitary, rectangular in girdle view, with a single chloroplast with medially positioned centre and lobes beneath both valves (Fig. 2 A-I). Chloroplasts share the characteristic organization typical for the genus (Mereschkowsky 1903; Cox 1987, 2003). The chloroplast is single, large, and extends along the inner surface of the cell. The central column (isthmus) is offset to one side from the central axis and forms a slight bend. Libroplast is missing or represented by only one granule (Fig. 2A, F). The chloroplast has four irregular outgrowths (similar to petals) extending from the isthmus. Valve are linear-elliptical, slightly asymmetric along the longitudinal axis (Fig. 2 J-Z). Apices are bluntly rostrate, often asymmetric, breadth 1.3-2.0 µm. Valve length 10.3- 15.4 µm, valve width 6.0-6.8 µm. Axial area narrow, almost linear, very slightly wided towards the valve middle. Central area is absent. Raphe filiform, straight, central pores are small. The structure of distal raphe ends not discernible in the LM. Striae radiate, 17-21 in 10 µm, in the valve middle 2-3 irregularly shortened striae are present on each side. Areolae not resolvable in LM.
SEM external views (Fig. 3)
Valve face is flat. Raphe narrow, linear (Fig. 3A). Proximal raphe ends straight, small, slightly expanded (Fig. 3B). Distal raphe ends hook-shaped, extending to the valve mantle and unilaterally bent (Fig. 3A, C). Striae composed of 3-11 rounded or weakly elongated areolae, continuing onto the valve mantle. Areolae 45-50 in 10 µm. Stigma is absent.
SEM internal views (Fig. 4)
The raphe is straight (Fig. 4A). Proximal raphe ends are hooked-shaped and deflected to one side (Fig. 4B). Distal ends terminating on small helictoglossae and may be slightly deflected to opposite sides (Fig. 4A, C). The striae are bordered by broad interstriae (virgae) (Fig. 4C). Areolae small, square or round.Two isolated areolae are present at the apices (Fig. 4C). Volate occlusions were not preserved during the material treatment.
description: Published as part of Kezlya, Elena, Glushchenko, Anton, Kociolek, John Patrick, Maltsev, Yevhen, Genkal, Sergey & Kulikovskiy, Maxim, 2022, A new species of Placoneis Mereschkowsky (Bacillariophyceae: Cymbellales) from wet soils in southern Vietnam, pp. 177-188 in Cryptogamie, Algologie 20 (11) on pages 180-181, DOI: 10.5252/cryptogamie-algologie2022v43a11, http://zenodo.org/record/7829344