Eunotia multirimoportulata Veselá, Bohunická & Kaštovský, 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 : 166-171

Eunotia multirimoportulata Veselá, Bohunická & Kaštovský , sp. nov. ( Figs 9–12 )

Frustules rectangular in girdle view from the ventral side ( Figs 9I–K ), ca. 40 μm wide. Valves with slightly to moderately concave ventral margins and highly convex dorsal margins, constantly with four wave crests on the dorsal margin ( Figs 9A–H , 10A–K ). Valve crests rounded, with a similar degree of curvature of the crests and the depressions ( Fig. 10A ). Valves relatively large for the genus, 85–128 μm long, 36–46 μm wide in the largest peak, and 33–43 μm wide in between the crests and the center of ventral margin. Valve length-to-width ratio mostly around 2.6 (2.5–3.0). Valve apices broadly truncated (e. g., Figs 9A, G , 10A ) to round (e. g., Figs 9C, H , 10F, K ). Terminal nodules on the ventral side of the valve, not far from the apices ( Figs 9A–H , 10A–K ). Terminal raphe fissures curving onto the valve face ( Figs 11B, D, E, H, I ), pointing towards the center of the apical part of the valve ( Figs 9A , 10A , 11F ). Helictoglossa is massive and well visible in LM ( Figs 9A–H , 10 ). Number and arrangement of rimoportulae highly variable, two to five (most commonly three or four) rimoportulae per each valve apex ( Figs 10D , 12B, E–I ), in total five to eight per valve. Rimoportulae arranged individually ( Figs 12B, F ), as a group ( Figs 12G, H ), or as a combination of both ( Figs 12E, I ). External opening of each individual rimoportula (or a group of rimoportulae) usually as an elongated pore ( Fig. 11C–E, H, I ), sometimes as a round pore ( Fig. 11C ), located at the apex on the mantle. Valves densely striated (e. g., Figs 9A , 10A , 11A , 12A ), 14.0–17.5 striae in 10 μm near the center of ventral part of the valve ( Fig. 12C ), up to 23 striae in 10 μm at the wave crests due to the inserted striae ( Fig. 11G , 12D ), and 20–23 striae in 10 μm near the apices ( Fig. 11F ). External small ridges in between striae irregularly spaced, giving the valve surface appearance of a “rough cloth” ( Figs 9B , 10G , 11A, G ). On the mantle, slightly below the valve edges, a thin irregular siliceous rim-like structure present ( Figs 11C–E, H, I ). Externally areolae open, small and embedded in between the ridges ( Fig. 11G ), internally areolae also unoccluded, well rounded and large ( Fig. 12J ), 20–25 in 10 μm.

Type:— VENEZUELA. Bolívar State: Guyana Highlands, Chimantá Massif, Churí-tepui, small pool close to the entrance of Charles Brewer Cave, 5º 14.952’ N, 62º 1.588’ W, 2200 m a.s.l., J. Kaštovský 508, 20 January 2012 (holotype: ANSP!, slide GC 26824, specimen 9.1 mm south by 6.7 mm east from the benchmark cross on the slide, here illustrated as Fig. 9A . Isotype: CBFS!, slide A-054, specimen 14.3 mm south by 10.3 mm east from the benchmark cross on the slide, here illustrated as Fig. 9D ).

Etymology:—From the Latin words multi (many) and rimoportula (labiate process), referring to the prominent feature of having a noticeably larger number of rimoportulae compared to other species within the genus Eunotia .

Ecology and distribution:—This taxon was observed at a single site as an epiphyte on a red alga Audouinella sp. growing on the bottom of a small pool close to the entrance to the Charles Brewer Cave.

Comparison with similar taxa:— Eunotia multirimoportulata is extremely similar to the here described taxon E. churiensis , although the moderate curvature of the valve crests (correlated with a smaller crest height, Fig. 10A , Table 4B), slightly higher striation density at the apices (Table 4A), higher number of rimoportulae (Table 4B), and different ecology (see above) clearly separate E. multirimoportulata from E. churiensis . In addition, E. multirimoportulata has slightly longer and narrower valves compared to E. churiensis (therefore larger length-to-width ratio, Table 4A).

Eunotia multirimoportulata is also very similar to E. tetraodon . Eunotia multirimoportulata , however, possesses more than two times larger valves, with dimensions completely outside of the reported size range for E. tetraodon (Table 4A). Furthermore, valves of E. multirimoportulata have a denser striation compared to E. tetraodon (Table 4A). Based on our observations on the number of rimoportulae in E. tetraodon (see under E. churiensis ), E. tetraodon possesses zero to two rimoportulae at one apex and none on the other, unlike E. multirimoportulata with two to five rimoportulae at each apex and at least five rimoportulae present on each valve. Additionally, the valve face of E. tetraodon is smooth ( Lange-Bertalot et al. 2011: plate 103, figs 3, 4) without any hint of ridges as observed in valves of E. multirimoportulata .

Similarly to E. churiensis , E. multirimoportulata should be compared with E. semicircularis . However, E. semicircularis can be easily recognized from E. multirimoportulata based on its smaller valve width, valves without any rimoportulae and distribution only in cold regions of Northern Hemisphere (Scandinavia and the Arctic, Table 4B).

Figures

FIGURE 9. Eunotia multirimoportulata, sp. nov. Size diminution series and the variation of the valve shapes of the population from the type locality in LM (part 1), including girdle views. Fig. 9A represents the holotype specimen; Fig. 9D the isotype specimen. “=” indicate the same specimen in different foci. Scale bars = 10 μm.

FIGURE 10. Eunotia multirimoportulata, sp. nov. Size diminution series and the variation of the valve shapes of the population from the type locality in LM (part 2). Thick white lines in Fig. 10A draw attention to the typical similar shape of the top of the crests and the area in between the crests (compare to Fig. 6A). The thin white lines in Fig. 10A illustrate the method used for measuring crest heights (a distance from a line drawn between the centers of two surroundings saddle parts to the top of the crest). “=” indicate the same specimen in different foci. Well visible multiple rimoportulae are marked with white arrows. Scale bars = 10 μm.

FIGURE 11. Eunotia multirimoportulata, sp. nov., external views in SEM. valve overviews (A, B), details of the apices (C–F) with multiple openings to rimoportulae (C–E, H, I, white arrows), detail of the uneven valve surface (F, G) with external areolae openings (G), and the detail of the external raphe endings on the valve mantle together with several girdle bands (H, I). “=” indicate different parts or views of the same specimen. Scale bars = 10 μm (A, B, H, I) or 1 μm (C–G).

FIGURE 12. Eunotia multirimoportulata, sp. nov., internal views in SEM. valve overview (A), close-ups of the striae arrangement on the ventral (C) and dorsal part of the valve (D), close-ups of apices (B, E–I) with a various number and layout of rimoportulae (2 in B; 3 in G; 4 in E, F, I; and 5 in H), and a detail of internal openings of areolae (J). “=” indicate different parts or views of the same specimen. Scale bars = 10 μm (A) or 1 μm (B–J).