Neidium convolutum Y.Liu & Kociolek, 2020

Liu, Yan, Kociolek, John Patrick, Liu, Qi, Tan, Xiang & Fan, Yawen, 2020, A New Aerophilic Neidium Pfister (Neidiaceae, Bacillariophyta) species from Guangxi Zhuang Autonomous Region, China, Phytotaxa 432 (2), pp. 171-180 : 172-176

Neidium convolutum Y.Liu & Kociolek sp. nov. ( Figs 1–23 )

LM description ( Figures 1–6 ): Valves linear to linear-lanceolate, with wedge-shaped apices. From the end to the middle, half of the valve flat, other half of the valve twisted along the apical axis. Length 81–123 µm, breadth 18–22 µm. Margins parallel, slightly convex in the center. Axial area is narrowly lanceolate, being linear and narrow at the apices, becoming wider towards the center. Central area is small, elliptical, nearly 1/3 of the valve width. Raphe lateral, proximal raphe ends curved in opposite directions. Striae uniseriate, punctate, slightly oblique along the transapical axis, become convergent near the ends. 17–18 per 10µm. Longitudinal lines are obvious, evident along the valve margins.

SEM descriptions ( Figures 7–23 ): External views show a portion of the valve surface is flat, while the rest of the valve is slightly twisted about the apical axis. The valve face is well differentiated from the mantle. The raphe is straight, with distinct, hooked central raphe endings curved in opposite directions ( Fig. 12 ); the lacinia originates at the base of the mantle ( Figs 9, 10 , 16 ) and extends to cover the terminal raphe end at the apices ( Fig. 8 ). Striae interrupted at the margin by the longitudinal canal, extending onto the mantle.Areolae on the mantle are smaller than on the valve. Longitudinal lines covered by a hyaline area that contains one or two rows of areolae in the middle of the hyaline area and that are morphologically differentiated from the areolae elsewhere on the valve ( Fig. 10 ). On some valves there is one row of areolae present in the axial area next to the raphe ( Figs 12 , 17 ). All areolae on the valve face are round to elliptical in outline and have volate projections which can be branched, bifurcate or T-shaped ( Figs 11 , 17, 18 ). In some valves, thought to be ontogenetically incomplete, the areolae are round to elliptical in shape but without any volate projections ( Fig. 13 ). Girdle bands number 3–4 and are without poriods ( Figs 14, 15, 16 ).

Internally, the raphe sternum is almost flat with the valve surface ( Fig. 19 ). The distal raphe ends terminate in thickened, raised helictoglossae on the valve face, and are slightly bent to one side of the valve ( Figs 20, 21 ). In the central area, two distinct helictoglossae are fused to form an elongated, raised structure ( Fig. 22 ). The internal openings of the valve areolae are round, the internal opening of the longitudinal canal and mantle areolae are more elliptical. All the areolae are covered by hymenes ( Figs 20, 21, 22, 23 ). There are small renilimbi along the longitudinal canals and axial area ( Figs 20, 21, 22, 23 ).

Type:— CHINA. Guangxi Zhuang Autonomous Region: Shiwan Mts. National Forest Park. Wet-wall, Coll. Y. Liu July 2014 (holotype: HANU! Individual in slide THHN 2014235, here illustrated as Fig. 2 , isotype: COLO! JPK material No.11526, slide No. 608060)

Etymology: — This species is named for having twisted valves.

Figures

FIGURES 1–3. Neidium convolutum Liu & Kociolek sp. nov. LM pictures. Valve views showing size dimension various. Fig.2 is of the holotype. Scale bar = 10 µm.

FIGURES 4–6. Neidium convolutum Liu & Kociolek sp. nov. LM pictures. Valve views showing size dimension various. Scale bar = 10 µm.

FIGURES 7–13. Neidium convolutum Liu & Kociolek sp. nov. SEM, external view. Fig. 7: Whole valve, showing the twisted part (white arrow); Fig. 8: Wedge-shaped apex, with lacinia covered the terminal raphe ends (white arrow); Fig. 9: Wedge-shaped apex of the same valve with lacinia original from mantle (white arrow); Fig. 10: Longitudinal canal with one or two rows of areolae (with arrow); Fig. 11: Magnification of the areolae opening, showing the volate occlusions. Fig. 12: Elliptical central area, with proximal raphe ends curved in opposite sides, some areolae positioned at the axial area next to the raphe (white arrow); Fig. 13: Uncompleted valve, with unoccluded areolae.

FIGURES 14–18. Neidium convolutum Liu & Kociolek sp. nov. SEM, external view. Fig. 14: Girdle view of the whole frustule; showing the twist of the valve; Fig. 15: Unporiod girdle bands; Fig. 16: Girdle view of the apex, showing the original position of lacinia (white arrow); Fig. 17: Areolae in the axial area with volate occlusions (white arrow); Fig. 18: Areolae on the longitudinal canal with volate occlusions (white arrow).

FIGURES 19–23. Neidium convolutum Liu & Kociolek sp. nov. SEM, internal view. Fig. 19: Whole valve; Fig. 20: Valve apex, helictoglossae on the valve face (white arrow); Fig. 21: Valve apex, raised helictoglossae (white arrow) and renilimbi along the axial area (black arrow); Fig. 22: Proximal raphe ends fused to an elongated structure, raised upon the valve (white arrow), renilimbi along the axial area (black arrow); Fig. 23: Magnification of internal opening of areolae with hymenes, the opening of areolae on the longitudinal canal are elongated (white arrow), renilimbi along the longitudinal canal (black arrow).