Schizothrix venezuelana Kaštovský, Fučíková & Bohunická, sp. nov. (Fig. 3) Trichomes in mats or fascicles (Fig. 3D), pale green, 1–2 per sheath (Figs 3C, E, F). Sheaths wide, distinctly lamellate, red, dark red to red-brown, sometimes colorless (especially in the centre of the mats), narrowing towards the ends and closed at the tip, (13)17–20(25) μm wide (Figs 3A, B). Cells 1.5–2.0(3.0) μm wide, 1.5–2.0(2.5) times longer than wide. Cell content smooth or granulated, without aerotopes. Trichomes slightly constricted or not constricted at the cross walls. Apical cells rounded, without calyptra, sometimes tapered at the end and longer than normal cells (up to 11 μm) (Figs 3A, B). Reproduction by disintegration of the ends of the trichomes into motile few-celled hormogonia. Necridic cells or false branching were not observed. Type:— VENEZUELA. Bolívar State: Guyana Highlands, Chimantá Massif, Churí-tepui–Charles Brewer Cave Base Camp, “Kitchen grieta”, rim above the entrance into the Charles Brewer Cave, 5º 14.952’ N, 62º 1.588’ W, 2200 m a.s.l., J. Kaštovský, 16 January 2012 (holotype: CBFS! A-021, Herbarium for Nonvascular Cryptogams at the Department of Botany, Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic). Etymology:— From the Latin adjective venezuelana (from Venezuela), referring to the country where the species was first discovered. Ecology and distribution:—This taxon occurred frequently on wet sandstone rocks on top of Churí-tepui and Roraima, Venezuela. This species was found abundantly in 55 % of the collected samples from wet rock walls on Churí-tepui. Comparable abundance was observed on Roraima, where it was identified as S. cf. telephoroides (Kaštovský et al. 2011). Comparison with similar taxa:— Schizothrix venezuelana has a unique combination of morphological features within the genus Schizothrix —wide, dark red colored sheath and a thin trichome. Table 2 compares main morphological features of all known taxa similar to S. venezuelana. Schizothrix telephoroides (Montagne ex Kützing 1849: 309) Gomont (1890: 319), according to its original description, has much wider trichomes and, according to the modern point of view, it is closer to the genus Symplocastrum (Gomont 1892: 316) Kirchner in Engler & Prantl (1898: 69) than to Schizothrix (see Komárek & Anagnostidis 2005). Golubić (1967) reported a cyanobacterium with thin trichomes and red wide sheath under the name S. telephoroides, which rarely occurred on wet sandstone rocks in the lowland of east Venezuela in the vicinity of the city Cumaná. The species reported by Golubić (1967: 697) does not correspond with the original S. telephoroides description, but is more similar to S. venezuelana (see Table 2). Ecology and geographic origin of this cyanobacterium is similar, but its morphology is different. Schizothrix venezuelana has slightly narrower trichomes and wider filaments but especially differs by the end of the filament: S. venezuelana has sheaths closed at the tip, whereas S. telephoroides sensu Golubić 1967 has sheaths open at the ends of filaments (Golubić 1967: 695). Schizothrix minor (Gardner 1927: 53) Anagnostidis (2001: 368), from lateritic soil in Puerto Rico, has similar dimensions of the trichomes, but presents false branching (lacking in the newly described species) and has pink sheaths (and not dark red or red-brown as in S. venezuelana). Schizothrix epiphytica Fritsch in Fritsch & Rich (1924: 361) has slightly narrower trichomes, significantly narrower filaments and different ecology. Schizothrix gomontii Weber van Bosse (1913: 20) has thinner sheaths and forms macroscopic colonies, which were never observed in S. venezuelana (Tab. 2).

Published as part of Kaštovský, Jan, Veselá, Jana, Bohunická, Markéta, Fučíková, Karolina, Štenclová, Lenka & Brewer-Carías, Charles, 2016, New and unusual species of cyanobacteria, diatoms and green algae, with a description of a new genus Ekerewekia gen. nov. (Chlorophyta) from the table mountain Churí-tepui, Chimantá Massif (Venezuela), pp. 153-180 in Phytotaxa 247 (3) on page 157, DOI: 10.11646/phytotaxa.247.3.1, http://zenodo.org/record/13675639