Navicula cryptofallax var. tibetica Chudaev, 2016

Chudaev, Dmitry A. & Georgiev, Anton A., 2016, New taxa of Navicula sensu stricto (Bacillariophyta, Naviculaceae) from high-altitude lake in Tibet, China, Phytotaxa 243 (2), pp. 180-184 : 182-183

Navicula cryptofallax var. tibetica Chudaev , var. nov. ( Figs 16–32 )

Valves lanceolate with capitate apices. Valve length 29.6–34.1 μm, valve breadth 5.9–6.9 μm. Axial area narrow, linear. Central area transversely expanded, more or less circular in outline, occupying about 1/2 of valve width. Striae radiate, becoming slightly convergent at ends. Striae density 13.5–15.5 in 10 μm. Areolae lineolate, not discernible in light microscopy, 30.7–37.8 in 10 μm. There are 2–3 isolated areolae around each valve apex on the primary valve side. Raphe filiform, raphe-sternum slightly elevated over valve surface externally and slightly widened in the central part. Central external raphe endings straight, drop-like. Distal external raphe endings hook-shaped and curved to the secondary side of valve, their ends positioned on valve mantle. Central internal raphe endings straight. Accessory rib only barely distinguishable on primary side of raphe-sternum internally. Distal internal raphe endings well-developed helictoglossae.

Type:— CHINA. Tibet Autonomous Region: nameless lake, 28° 37’ 16.88” N, 93° 13’ 43.04” E, periphyton on filamentous algae, Anomymous, 3 November 2006 (Holotype: MW!, slide 313s1, diatom collection of the Department of Mycology and Algology, M. V. Lomonosov MSU, specimen here depicted in Fig. 22 . Isotype: IBIW! material 04108, collection of Maxim Kulikovskiy, Institute for Biology of Inland Waters RAS).

Etymology:— The epithet “ tibetica ” revefers to the place where the taxon was found. Distribution:— The taxon is thus far precisely known only from the type locality.

Figures

FIGURES 16–32. Navicula cryptofallax var. tibetica, var. nov. 16–28. Light microscopy, Fig. 22 illustrates the holotype specimen.29–32. SEM. 29. Valve apex, external view. 30. Valve centre, external view. 31. Valve apex, internal view. 32. Valve centre, internal view. Scale bars: 10 μm (Figs 16–28), 1 μm (Figs 29–32).