Nupela mongolica Glushchenko, Tseplik, Maltsev, Genkal, Nergui & Kulikovskiy, 2025

TSEPLIK, NATALIA, GLUSHCHENKO, ANTON, MALTSEV, YEVHEN, GENKAL, SERGEY, NERGUI, SONINKHISHIG & KULIKOVSKIY, MAXIM, 2025, Molecular investigation of Nupela mongolica sp. nov. (Bacillariophyceae) with the description of the family Nupelaceae fam. nov., Phytotaxa 681 (2), pp. 186-198 : 190

Nupela mongolica Glushchenko, Tseplik, Maltsev, Genkal, Nergui & Kulikovskiy sp. nov. ( Figs 2–31 )

LM description ( Figs 2–15 ):— Frustule rectangular in girdle view ( Fig. 15 ). Thickenings in the area of the central nodules clearly visible ( Fig. 15 , black arrowhead). Valves biraphid, linear to slightly transapically curved with parallel margins and rounded ends. Length 13.5–15.2 µm, width 2.4–3.0 µm. Axial area very narrow, linear, weakly expanded towards the central area. Central area rectangular, reaches almost to the edges of the valve and resembles a fascia. Raphe fine. Striae not resolvable in LM ( Figs 2–14 ).

TEM ( Figs 16–20 ):— The external openings of the areolae are transapically elongated with a crater-shaped depression ( Figs 19, 20 , white arrows), the internal openings (foramen) are smaller, rounded to weakly elliptic ( Figs 19, 20 , black arrows). The external crater-shaped depressions of the areolae are completely covered by a hymen layer ( Figs 17, 18 , black arrows) that extends beyond the areolae onto the valve. The hymenes have hexagonal perforations 8–10 nm in diameter ( Figs 17, 18 , white arrows). At the valve apices there is one row of areolae located on the junction between valve face and margin ( Fig. 16 , white arrows). Raphe branches are straight ( Fig. 16 , white arrowheads). Voigt discontinuities present ( Fig. 16 , black arrows).

SEM, external view ( Figs 21–26 ):— Valve face flat. Central area formed by 7–10 very short striae (composed of 1–2 elongated areolae) on each side ( Fig. 22 , black arrows). Raphe filiform, more or less straight ( Figs 21–24 ). Central raphe ends slightly expanded ( Fig. 21 ). Distal raphe ends hook-shaped, deflected onto the valve mantle ( Fig. 21 , black arrows) or sometimes terminating before reaching the apex of the valve ( Fig. 23 , black arrows). Striae weakly radiate, sometimes becoming almost parallel at the ends, composed of 2–4 areolae in a stria, 40–44 in 10 µm. The valves are covered with a continuous film ( Fig. 21 ). With further corrosion of the material, the structure of the areolae is exposed ( Figs 22–24 ). The areolae have a transapically elongated shape and are covered by hymenes, which completely cover the crater-like depression of the areolae ( Figs 22, 24–26 , white arrows) and extend onto the valve face. The hymenes begin to corrode from one edge ( Figs 24–26 , black arrows). When the hymen layer is completely destroyed, the internal opening of the areola becomes visible, which has a smaller diameter than the external one, which has a crater-like shape ( Figs 25, 26 , white arrowheads). Voigt discontinuities present ( Figs 22–24 ). The valve mantle has no areolae ( Figs 24, 25 , black arrowheads).

SEM, internal view ( Figs 27–31 ):— The valve branches are almost straight. Central nodule present, expanded ( Fig. 29 , black arrow). Central raphe ends T-shaped ( Figs 28, 30 , black arrows). Distal raphe ends weakly unilaterally deflected and terminate in small helictoglossae ( Figs 27, 31 , black arrows). Areolae rounded to elliptical, smaller than their external openings. Areolae form two (rarely one) longitudinal rows on both sides of the raphe ( Figs 27, 28 , white arrows).

Type:— Mongolia, Arkhangai Province, Davaa Lake (48°10.803′N; 98°46.107′E); leg. M.S. Kulikovskiy, 08 July 2015. Slide no. 03240 from oxidized culture strain Mnp 155, isolated from sample Mn 084, deposited in Herbarium of MHA, Main Botanical Garden, Russian Academy of Science , Moscow, Russia. Holotype specimen illustrated in Figure 3 .

Isotype:—Slide no. 03240a deposited in collection of Maxim Kulikovskiy at the Herbarium of the Institute of Plant Physiology Russian Academy of Sciences, Moscow, Russia.

Reference strain:— Mnp155, isolated from the sample Mn075, deposited in the collection of Maxim Kulikovskiy at the Herbarium of the Institute of Plant Physiology, Russian Academy of Sciences, Moscow, Russia.

Sequence data:— Partial 18S rDNA gene sequence comprising V4 domain sequence (GenBank accession number PM350064) and partial rbc L sequence (GenBank accession number PM349978) for the strain Mnp155.

Etymology: —The specific epithet refers to the name of the country where this species was observed.

Distribution:— As yet known only from the type locality.

Figures

FIGURES 2–15. Nupela mongolica sp. nov. LM, DIC, size diminution series. Slide no. 03240 from oxidized culture, strain Mnp155. Figs 2–14. Valve view. Fig. 15. Frustule in girdle view, black arrowhead shows the thickening of the central nodule. Fig. 3 represents the holotype. Scale bar = 10 μm.

FIGURES 16–20. Nupela mongolica sp. nov. TEM. Oxidized culture, strain Mnp155. Fig. 16. Whole valve. Black arrows show the Voigt discontinuities. White arrows show the one row of areolae located on the junction between valve face and mantle. White arrowheads show the straight raphe branches. Figs 17, 18. Black arrows show the hymen layer completely covering the external crater-shaped depression of the areolae, extending beyond the areola onto the valve. White arrows show the rounded perforations in the hymen layer. Figs 19, 20. White arrows show the external openings of the areolae that are transapically elongated with a crater-shaped depression. Black arrows show the internal openings of the areolae. Scale bars = 1 µm (Fig. 16), 0.2 µm (Figs 17, 19, 20), 0.1 µm (Fig. 18).

FIGURES 21–26. Nupela mongolica sp. nov. SEM, external views. Oxidized culture, strain Mnp155. Figs 21–24. Whole valve. Figs 25, 26. Details of valves. Fig. 21. Black arrows show the distal raphe ends deflected onto the valve mantle. Fig. 22. Black arrows show the very short striae that form the central area. White arrow shows the areola, covered by a hymen, which completely covers the crater-like depression of the areola. Fig. 23. Black arrows show the distal raphe ends terminating before reaching the apex of the valve. Fig. 24. Black arrow shows the hymen beginning to corrode from one edge. White arrow shows the areola, covered by a hymen which completely covers the crater-like depression of the areola. Figs 25, 26. Black arrows show the hymenes beginning to corrode from one edge. White arrows show the areolae, covered by hymenes which completely cover the crater-like depressions of the areolae. Black arrowheads show the absence of areolae on the valve mantle. White arrowheads show the hymen layer that is completely destroyed and the internal opening of the areola becomes visible, which has a smaller diameter than the external crater-like one. Scale bars = 1 µm (Figs 21–24), 0.5 µm (Figs 25, 26).

FIGURES 27–31. Nupela mongolica sp. nov. SEM, internal views. Oxidized culture, strain Mnp155. Figs 27–29. Whole valve. Fig. 30. Details of valve. Fig. 31. Valve end. Fig. 27. Black arrows show the raphe ends weakly unilaterally deflected and terminating in small helictoglossae. White arrows show the areolae forming two longitudinal rows on both sides of the raphe.Fig. 28. Black arrows show the Tshaped central raphe ends. White arrows show the areolae forming one and two longitudinal rows on both sides of the raphe.Fig. 29. Black arrow shows the expanded central nodule. Fig. 30. Black arrows show the T-shaped central raphe ends. Fig. 31. Black arrows show the raphe ends weakly unilaterally deflected and terminating in small helictoglossae. Scale bars = 1 µm (Figs 27–29), 0.25 µm (Figs 30, 31).