Hannaea tibetiana Q.Liu, Glushchenko, Kulikovskiy & Kociolek, sp. nov.

(Figs 1-3)

HOLOTYPE. — Slide no 201507029-1; illustrated in Fig. 1H in collection at Qi Liu of the Freshwater Algal Herbarium of Shanxi University (SXU).

TYPE LOCALITY. — China, Midui Glacier, Tibet, unnamed river, periphyton, (N29°87.684’, E96°29.678’).

ETYMOLOGY. — The specific epithet “ tibetiana ” refers to the name of the region where this species was observed.

DISTRIBUTION. — As yet known only from the type locality.

DESCRIPTION

Valves

Asymmetrical about the apical axis, lunate to almost rectangular, with capitate to bent-capitate apices, length 22-43 µm, breadth 15-18 µm (n=45).

Central sternum

Distinct to indistinct, with striae parallel to slightly radiate, 16-18/10 µm.

Bent apices

Deflected towards the ventral margin.

The concave valve

May bear an unilaterally-positioned unornamented area on the concave margin of the valve in the center, slightly tumid to undifferentiated.

SEM, external views (Fig. 2)

The exterior of the valve can be seen to have a distinct central sternum, with heavily silicified ridges perpendicular, extending across the valve face (Fig. 2A, B). Striae uniseriate, comprised of small, rounded areolae (Fig. 2 A-C), that extend onto the valve mantle (Fig. 2C, D). Areolae number 85-90 /10 µm within a stria. Cingulum comprised of numerous bands (Fig. 2E). At one apex some striae can extend the central sternum, and even be oriented along the apical axis of the valve (Fig. 2F). An elongated opening at one end of the valve is the external expression of the single rimoportula. Ocellimbi are present at each apex, positioned on the valve mantle (Fig. 2G).

SEM, internal views (Fig. 3):

The central sternum is narrow, and striae are positioned alternatively on each side (Fig. 3A, B). At one apex there is no rimoportula (Figs 3A, C), at the other a rimoportula is present (Fig. 3A, D). The rimoportula is comprised of two thickened strips of silica on either side of a slit-like opening (Fig. 3D). At the apices striae may extend across the central sternum. Small, square-shaped porelli comprise the ocellimbi on the mantle of each apex (Fig. 3C, D).