Planothidium paisiusii Tseplik, Glushchenko, Maltsev, Genkal, Iurmanov & Kulikovskiy, 2025

Tseplik, Natalia, Glushchenko, Anton, Maltsev, Yevhen, Genkal, Sergey, Iurmanov, Anton & Kulikovskiy, Maxim, 2025, Molecular and morphological investigation of Sellaphora ashinovii sp. nov. and Planothidium paisiusii sp. nov. - two new diatom species from Oromia Region, Ethiopia, Phytotaxa 701 (2), pp. 161-176 : 167-169

Planothidium paisiusii Tseplik, Glushchenko, Maltsev, Genkal, Iurmanov & Kulikovskiy sp. nov. ( Figs 27–63 )

Holotype. Slide no. 05583 (represented here by Figure 49 ), deposited in the Herbarium of K.A. Timiryazev Institute of Plant Physiology , Russian Academy of Sciences (HD), Moscow, Russia, prepared from oxidized culture strain CBMC155 ef.

Isotype. Slide no. 05583a, Herbarium of Addis Ababa University, Addis Ababa, Ethiopia.

Reference strain. CBMC 155ef from the Culture and Barcode Collection of Microalgae and Cyanobacteria “Algabank” (СВМС), isolated from sample E14.

Type locality. Ethiopia, Mesekelhericho, Adaba, West Arsi, nameless mountain stream, periphyton, 2978 m elev., 07°1.96’ N 39°33.277’E., leg. B.A. Levin, 3 April 2016. Sample E14.

Description. LM ( Figs 27–59 ). Cells in girdle view rectangular, slightly bent. Valves linear-elliptic to linear-lanceolate, with rounded ends. Length 8.6–11.7 μm (9.8 ± 0.6; n=32), width 3.7–4.5 μm (4.1 ± 0.2; n=32). Raphe straight, filiform, with expanded central ends.Axial area on the raphe valve narrow linear, central area may be indistinct, usually asymmetric, formed by 1–2 central striae shortened and spaced wider than the rest. Striae radiate, 15–16 in 10 μm. Axial area on the rapheless valve also linear, widening towards the centre. A rounded cavum is present on the one side of the rapheless valve. Striae weakly radiate to almost parallel in the centre of the valve, more radiate towards the ends, 14–18 in 10 μm.

SEM. Raphe valve ( Figs 60, 62 ). External central raphe ends straight, expanded, distal ends curved to one side and extended onto the mantle. Internal central raphe ends slightly bent to the opposite sides and set quite widely apart, distal ends terminate in small helictoglossae. Striae multiseriate, each stria consists of 4 (3) rows of small circular areolae.

Rapheless valve ( Figs 61, 63 ). Cavum large, rounded, usually with a relatively small opening. A vestigial raphe is present on the inside. Striae multiseriate, consisting of 3–4 rows of small circular areolae. Internally, the interstriae are distinctly raised on both valves.

Sequence data. Partial 18S rDNA gene sequence comprising V4 domain sequence (GenBank accession number PV383266) and partial rbc L sequence (GenBank accession number PV384975) for the strain CBMC155ef.

Etymology. This species is named after Archimandrite Paisius (Vasily Filippovich Balabanov, 1832–1912), the leader of the spiritual mission of Ashinov’s expeditions to Abyssinia in 1888–1889, honoring his contribution to the strengthening of Russia-Abyssinia ties.

Distribution. As yet known only from the type locality.

Molecular study. On the phylogenetic tree ( Fig. 64 ), this species forms a separate branch that is related to strains of the Planothidium frequentissimum (Lange-Bertalot) Lange-Bertalot (1999: 282) and Planothidium victori Novis, Braidwood & Kilroy in Novis et al. (2012: 22) complex.

Figures

FIGURE 64. Phylogenetic position of Planothidium paisiusii sp. nov. (indicated in bold) based on Bayesian inference for a concatenated alignment of 54 partial rbcL and partial 18S rDNA sequences. The total length of the alignment is 1,040 characters. Values above the horizontal lines are bootstrap support from ML analyses (<50 are not shown); values below the horizontal lines (or to the right of the slash) are Bayesian posterior probabilities (<0.9 are not shown). Strain numbers (if available) and GenBank numbers are indicated for all sequences.

FIGURES 27–40. Planothidium paisiusii sp. nov. LM, DIC. Sample of wild population, size diminution series. Figs 27–33. Raphe valves. Figs 34–39. Rapheless valves. Fig. 40. Girdle view. Scale bar = 10 μm.

FIGURES 41–63. Planothidium paisiusii sp. nov. Strain CBMC155ef, type material. 41–59. LM, DIC. Slide no. 05583 from oxidized culture. 41–50. Raphe valves. 51–59. Rapheless valves. Holotype represented by fig. 49. 60–63. SEM. 60. Raphe valve, external view. 61. Rapheless valve, external view. 62. Raphe valve, internal view. 63. Rapheless valve, internal view. Scale bar 10 μm (figs 41–59), 2 μm (figs 60, 61), 1 μm (figs 62, 63).