Achnanthidium tibeticum Y. Liu & J.P. Kociolek, 2022

Ge, Danyang, Zhang, Simeng, Liu, Hongyan, Liu, Yan, Kociolek, Patrick John, Zhu, Huan, Liu, Guoxiang & Fan, Yawen, 2022, One new species of Achnanthidium Kützing (Bacillariophyta, Achnanthidiaceae) from Tibet, China, Phytotaxa 538 (4), pp. 268-280 : 271-275

Achnanthidium tibeticum Y. Liu & J.P. Kociolek sp. nov. Figures 1–32

Type:­— CHINA. Tibet: Medog County, Yarang Village, Streams , 95°28’22.8 E, 29°29’97.0 N,19 June, 2019. (holotype HANU! Slide no. THTYJZL12, College of Life Science and Technology, Harbin Normal University, Harbin, China. Figs 1 & 2 are of the holotype specimen) . Isotype : Material no. YJZL12-12 , slide no. YJZL12-12 #. Cleaned material stored in Key laboratory of Algal Biology, Institute of Hydrobiology , Chinese Academy of Sciences , Wuhan, China .

Description:­— LM ( Figs 1–14 ): Raphe valve slightly convex, rapheless valve slightly concave. Valves linear to elliptic, with apices rounded. Length 7.9–3.6 μm, width 2.9–3.9 μm (n=25). Axial area narrow and linear. On the raphe valve, striae become coarser in the middle of valve, central area is inconspicuous. On the rapheless valves, central area is absent. On the raphe valves, striae slightly radiate in the center, becoming radiate towards the ends; 9–12 per 10 μm in center of raphe valve, denser near the ends at 18–20 per 10 μm. On the rapheless valve, striae nearly parallel in the center and become slightly radiate towards the ends; 12–15 per 10 μm.

SEM: Raphe valve ( Figs 15–26 ): Externally, raphe on the valve face never extends onto the mantle, straight, distal raphe ends?-shaped, curved to the same direction ( Figs 15–17, 20 ), proximal raphe ends slightly expanded, teardrop-shaped. Striae uniseriate, areolae almost round, with varying sizes. One row of slit-like areolae present in the mantle. Internally, raphe straight, distal raphe ends terminate in small helictoglossae, proximal raphe ends curved to the opposite directions. Areolae are occluded by fine hymenate structures.

Rapheless valve ( Figs 27–32 ): Externally, axial area narrow and linear; central area absent, areolae almost round. One row of slit-like areolae present on the mantle. Internally, sternum slightly raised on the apices, areolae structure similar to the raphe valve, with finely structured occlusions.

Etymology:­— Named for the province of the type locality.

Figures

FIGURES 1–14. Achnanthidium tibeticum Y.Liu & Kociolek sp. nov. LM images showing the size diminution of the valve. “=” means the raphe valve and rapheless valve are from the same frustule. Scale bar: 10 μm.

FIGURES 15–20. Achnanthidium tibeticum Y.Liu & Kociolek sp. nov. SEM pictures, external view of the raphe valve. 15. Whole valve view. 16–17. Distal raphe end from the same valve. 18. Proximal raphe ends. 19. Proximal raphe end and the areolae openings. 20. Whole valve view, showing the round areolae opening on the valve face (small arrow) and slit-like areolae on the mantle (wide arrow). Scale bars indicated in each figure.

FIGURES 21–26. Achnanthidium tibeticum Y.Liu & Kociolek sp. nov. SEM pictures, internal view of the raphe valve. 21, 26. Whole valve view. 22–23 Helictoglossa of the same valve. 24. Internal opening of the areolae. 25. Proximal raphe ends. Scale bars indicated in each figure.

FIGURES 27–32. Achnanthidium tibeticum Y.Liu & Kociolek sp. nov. SEM pictures, rapheless valve. 27–30. External view. 27. Whole valve view, showing the round areolae on the valve face (small arrow) and slit-like areolae on the mantle (wide arrow). 28–29.Apices of the same valve. 30. External areolae openings. 31–32. Internal view, apex of the valve (Fig. 31) and of the whole valve (Fig. 32). Scale bars indicated in each figure.