Mallomonas alpestrina Němcová & Zeisek, sp. nov. (Fig. 3A–I)

Three types of scale are discerned, including collar, body, and rear scales; however, a continuous transition between body and rear scales is evident. Collar scales (4.5 × 2.9 μm) are approximately triangular with rounded distal part. The submarginal rib is well developed at the dorsal and posterior ends of the scale, but totally reduced along the ventral edge. The submarginal rib is reinforced by internal struts, which appear striated in TEM images. The ventral flange is broad and smooth. The triangular hook-like dome is small, and protrudes above the surface of the other scales. The proximal border (rim) encircles only the dorsal part of the collar scale; together with the submarginal rib, they serve as tracks to fit the neighbouring collar scale in place. The scale shield is covered by a regularly arranged reticulum, large groups of pores (up to 20–25) are surrounded by short ridges of reticulum, and there is a thickened part (papilla) in the middle of each pore group (Fig. 3A). Domeless body scales (3.5 – 3.9 × 1.9–2.1 μm) are rhombic and extremely asymmetrical (Figs 3C, F). There is a smooth transition between posterior submarginal ribs and anterior flanges/submarginal ribs. Posterior submarginal ribs are striated (or bear internal struts, see Fig. 3D for detail). One of the anterior flanges is considerably broader and shorter, strengthened by ribs providing a wavy appearance. The other flange is penetrated by several groups of pores positioned along the anterior submarginal rib, but it lacks cross ribs (Figs 3B, E). The posterior flange is narrow and smooth. The proximal border (rim) encircles approximately one-third of the scale. Reticulation of the shield is similar to that of the collar scales. The rear scales ((2.0) 2.4 – 2.7 × 1.5 – 1.6 μm) are asymmetric, with one anterior flange considerably longer than the other, and the longer one bears 2−3 ribs (Figs 3G – I). The distal rear scales are almost rounded and bear a diminutive spine (Fig. 3I). Bristles are not observed; the species probably does not produce bristles. The cyst is unknown. The cell dimensions are unknown.

Type:— CHINA. Northern Yunnan: Diqin county, Zhongdian, unnamed lake on the slopes of Haba Xue Shan (Haba Snow Mountain), close to Haba village, 27° 20.798’ N 100° 4.582’ E, 4192 m a.s.l., V. Zeisek, 8 September 2012 (holotype: Fig. 3B).

Etymology:— The epithet refers to the occurrence of the species in a glacial lake at high elevation.

Habitat:— Oligotrophic high mountain lake.

Distribution:— China, the species was only found in the type locality.