Nupela major P. Yu

Yu, Pan, You, Qingmin, Kociolek, J. Patrick, Lowe, Rex & Wang, Quanxi, 2017, Nupela major sp. nov., a new diatom species from Maolan Nature Reserve, centralsouth of China, Phytotaxa 311 (3), pp. 245-254 : 246-247

Nupela major P. Yu , Q-M You & J.P. Kociolek sp. nov. ( Figs 1–34 )

Holotype: SHTU!, slide GZ-1510092!, holotype illustrated in Figs 4, 14 .

Isotypes: COLO! material 10464, Kociolek Collection, University of Colorado, Museum of Natural History Diatom Herbarium, Boulder, USA.

Type locality: CHINA. Maolan Nature Reserve, Guizhou Province, 25ᵒ15’735”N, 108ᵒ04’177E, altitude: 650 m, collected by Q-X. Wang & J.P. Kociolek, 4th October 2015).

Etymology: The species name is based on the size of this new species, the largest known species currently assigned to this genus.

Description: In LM, frustules are heterovalvate: one valve possesses a raphe, the other valve lacks a raphe. Valves are elliptical-lanceolate with more or less cuneate, slightly protracted ends. In total, 300 valves were measured. Length 20.0–41.5 μm, breadth 6.5–9.5 μm. Raphe valve has a linear-lanceolate axial area and an irregularly-shaped central area. Striae coarse, slightly radiate, irregular in the middle part, 14–17 in 10 μm, and more dense, strongly radiate near the apices, 17–22 in 10 μm. The rapheless valve has a linear-lanceolate axial area expanded laterally on one side at the center to form a more or less irregularly-shaped central area, sometimes reaching to the valve margin.

In SEM, the exterior of the raphe valve (figs 19–26) has a lateral raphe, with proximal raphe fissures appearing as small, uninflated pores (figs 19 & 20), and the distal raphe fissures deflected strongly in same direction onto the mantle, where they become recurved (figs 19–21). The central area is usually irregularly-shaped (fig. 22), the areolae are covered externally by a siliceous membrane (figs 19 & 20). Internally, the raphe is straight, the proximal raphe ends curve slightly in the same direction, the distal raphe endings terminate as small helictoglossae (figs 23–25). Striae are irregular, and the proximal raphe ends curve a little toward same directions (fig. 26). Rapheless valve (figs 27–34) with obvious siliceous thickenings on the external surface (figs 27–30), and forming a lanceolate depression in the axial area (figs 27 & 28). Areolae are difficult to observe. Internally, the striae are regularly-arranged, 17–20 in 10 μm, with an unornamented, lanceolate axial area (figs 31–34).

Ecology: pH 8.2, water temperature 20.0ᵒ, DO 9.48 mg /L, Salinity 0.16 ‰, TDS 213.2 g /L, Conductivity 296.1 μs/ cm, collected in three samples (GZ-1510090; GZ-1510091; GZ-1510092) on stones beneath a waterfall and associated with a moss community.

Distribution: So far, the new species only collected at the type locality.

Remarks: Nupela major sp. nov. can be compared to several species in the genus, based on similarities in outline and structure of the rapheless valve, including N. frezelii Potapova (2011: 85) , N. subrostrata (Hustedt) Potapova (2011: 83) and N. lapidosa (Krasske) Lange-Bertalot (1999: 280) . Comparison with these similar species is presented in Table 1. The lengths of all three species do not usually exceed 30 μm, and their breadths are less than 6.6 μm, while Nupela major sp. nov. is longer (to 41.5 μm) and wider (to 9.5 μm) than these similar taxa. Furthermore, there are obvious differences in the striae arrangement and density, shape of axial area, central area of the raphe valve and the internal proximal raphe slits. The striae of N. major sp. nov. are irregular with incompact areolae in the middle part, but the striae in N. frezelii , N. subrostrata and N. lapidosa are regular, and N. major sp. nov. has lower striae density (apices: 16–24 in 10 μm, center: 14–17 in 10 μm) than N. frezelii (29–33 in 10 μm), N. subrostrata (20–24 in 10 μm) and N. lapidosa (20–24 in 10 μm). The axial area of N. frezelii , and N. subrostrata is narrowly rhomboid, and the axial area of N. lapidosa is rhombic-lanceolate, while N. major sp. nov. has a lanceolate-shaped axial area that has a depression along the apical axis. The central area of the raphe valve of N. frezelii is strongly asymmetrical, transapically expanded, often with a depression on the wider side, and N. subrostrata and N. lapidosa have circular or elliptical central areas, sometimes asymmetrically expanded. The central area of N. major sp. nov., however, is usually irregularly-shaped. The internal proximal raphe slits of N. frezelii , N. subrostrata and N. lapidosa are T-shaped, but in N. major sp. nov., they curve a little toward the same direction. ( Potapova 2011; Camburn et al. 1978).

Figures

FIGURES 1–18. Light microscopy of Nupela major sp. nov., 1–9. Raphe valves. 10–18. Rapheless valves. 4. holotype, focus at raphe valve. 14. holotype, focus at rapheless valve. Scale bars= 10 μm.

FIGURES 19–22. Nupela major sp. nov., external view of raphe valve, SEM. 19 & 20. The valve has a undulate, lateral raphe, Striae are coarse, irregular in the middle part, and the areolae are covered externally by a hymenate occlusion. 21. Distal raphe fissure that deflect strongly in same direction onto the mantle, where they become recurved. 22. Middle portion of the valve with irregularly-shaped central area.

FIGURES 23–26. Nupela major sp. nov., internal views of raphe valve, SEM. 23 & 24. The raphe is straight, striae are made up of a number of areolae. 25. The distal raphe endings terminates in a small helictoglossa. 26. Proximal raphe ends curve slightly in the same direction. Striae appear irregular in length.

FIGURES 27–30. Nupela major sp. nov., rapheless valve, external valve views, SEM. 27 & 28. valve with obvious siliceous thickenings on the external surface. A deep trough extend the length of the valve. 29. Middle portion of the valve. 30. Apex of the valve.

FIGURES 31–34. Nupela major sp. nov., internal views of rapheless valves, SEM. 31 & 32. The valves have a lanceolate axial area, and the striae are regularly-arranged. 33. Middle portion of the valve. 34. Apex of a valve.