Porphyrosiphon latissimus Kaštovský, Fučíková & Bohunická, 2016

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), Phytotaxa 247 (3), pp. 153-180 : 160

Porphyrosiphon latissimus Kaštovský, Fučíková & Bohunická , sp. nov. ( Fig. 4 )

Cells approximately isodiametric, 4.5–6.0(7.0) μm wide, 3.5–5.5(7.0) μm long, barrel shaped, distinctly constricted at the cross walls, with granulated, yellow-brown content without aerotopes. Apical cells rounded, without calyptra, of the same dimensions as other cells in the filament ( Figs 4B, E, G ). Sheath wide, distinctly lamellate, yellow to brown, widely open at the tip, considerably longer than the trichome ( Figs 4B, E–G ). Filament, including the sheath, (25)30–40(50) μm wide. Generally one trichome per sheath, two in rare cases of pseudobranching ( Fig. 4F ). Reproduction by disintegration of the ends of trichomes into one or more motile hormogonia ( Fig. 4C ) with 8–22 cells. Necridic cells were not observed.

Type:— VENEZUELA. Bolívar State: Guyana Highlands, Chimantá Massif, Churí-tepui–Charles Brewer Cave Base Camp, Bathroom Creek canyon, above entrance into Charles Brewer Cave, 5º 14.952’ N, 62º 1.588’ W, 2200 m a.s.l., J. Kaštovský, 17 January 2012 (holotype: CBFS! A-020, 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 latissimus (widest), referring to the extraordinary width of the filament of the species.

Ecology and distribution:—This taxon occurred frequently on wet sandstone rocks, on top of Churí-tepui and Roraima, Venezuela. This species was observed in 10 % of the samples from Churí-tepui wet walls and previously also more frequently on Roraima (30 % of wet walls samples, identified as P. cf. notarisii, Kaštovský et al. 2011 ).

Comparison with similar taxa:— Generic characteristics (a single Phormidium -like trichome in wide lamellate and colored sheath, rarely two trichomes in a filament) correspond with the genus Porphyrosiphon , but the specimens from tepuis have a specific combination of relatively thin trichomes and the widest sheaths in the whole genus ( Table 3). All the known species having filaments with at least similar width to P. latissimus ( P. notarisii Kutzing ex Gomont (1892: 331) , P. notarisii var. major Gardner (1927: 41) and P. robustus Gardner (1927: 41 , 42)) have trichomes two- or more times wider and differ by color of the sheath. The trichome of the tepui-dwelling species is somewhat similar to trichomes of P. notarisii var. minor Li (1994: 70) from China, but that taxon has filaments half the size of P. latissimus (sheath of P. notarisii var. minor is significantly thinner, Tab. 3).

(according Komárek & Anagnostidis 2005).

Figures

FIGURE 4. Porphyrosiphon latissimus sp. nov. A. Line drawing of middle of the filament, hormogonium and the end of filament. B, E, F, G. Filaments end and multilayered colored sheath. C. Hormogonium. D. Central part of filament. Scale bars = 20 μm.