Kolbesia sichuanenis P. Yu

Yu, P., You, Q-M., Pang, W-T., Cao, Y. & Wang, Q-X., 2019, Five new Achnanthidiaceae species (Bacillariophyta) from Jiuzhai Valley, Sichuan Province, Southwestern China, Phytotaxa 405 (3), pp. 147-170 : 164-167

Kolbesia sichuanenis P. Yu , Q-M. You & Q-X Wang sp. nov. ( Figs 356–408 )

Holotype: SHTU!, slide JZG–201307018, holotype illustrated in Figs 356, 379 . Diatom samples are housed in the Biology Department Diatom Herbarium, Shanghai Normal University, China.

Isotypes: COLO!, slide 614007, Samples are housed in the Kociolek Collection, University of Colorado, Museum of Natural History Diatom Herbarium, Boulder, U.S.A.

Type locality: CHINA. Samples collected from Jiuzhai Valley Nature Reserve, Sichuan Province, 33°09’43”N, 103°53’34”E, altitude: 2332 m, collected by Q.X. Wang, on July 5, 2013.

Etymology: Species was named based on its finding in Sichuan Province.

Description: According to LM observations ( Figs 356–402 ), frustules were heterovalvar, and monoraphid. Valves were linear-lanceolate in shape, with broadly capitated ends, and valves had a central inflation slightly larger in width at the apical expansions. Valve length was 10.8–14.1 μm, and width 3.2–3.7 μm (n =50). Raphe valves possessed a narrowly linear-lanceolate axial area that had a small oval central area, and striae slightly radiated along the entire valve. Striae number was 22–26/10 μm at the center, and up to 28–30/10 μm near the apices on the raphe valve. Rapheless valves possessed a narrowly linear-lanceolate axial area that widened slightly towards the middle portion, and striae slightly radiated along the entire valve. Striae number was 24–28/10 μm in the middle and 28–32/10 μm near the apices. Individual areolae were not visible with an LM.

SEM observations of both valves revealed that the valve face: had a mantle junction bordered by a narrow hyaline area and the mantle had a single row of linear areolae ( Figs 403 , 405 ). On the exterior of the raphe valve, the raphe was filiform and straight; proximal and distal raphe ends were straight, small, and drop shaped, and the distal raphe did not extend along the valve mantle ( Fig. 403 ). Striae were uniseriate, and narrow striae comprised 1 macroareola (rarely 2 or 3) in the entire valve ( Fig. 403 ). Internally, the raphe terminated distally as an elevated helictoglossa, and the proximal raphe endings were short, deflecting in opposite directions ( Fig. 404 ).

On the external surface of the rapheless valve, the axial area was narrowly linear-lanceolate and had some cutting lines that widened slightly towards the middle portion ( Fig. 405 ). Striae were uniseriate with one macroareola on the external valve ( Fig. 405 ). Areolae occluded with a fine hymen structure that could be seen externally ( Fig. 407 ). Internally, macroareolae were on the valve face, and the occlusions comprised a fine hymenate structure ( Figs 406, 408 ).

Ecology: Collected in one sample JZG–201307018 on sediment (pH 8.42, water temperature 9.9 °C, TDS 0.246 g /L, conductivity 367 μs/cm). This new species occurred at 2 % relative abundances (total counted 400 valves) in sample JZG–201307018.

Distribution: Thus far, the new species was collected only at the type locality in Jiuzhai Valley.

Remarks: Kolbesia sichuanenis can be compared to several species in the genus Achnanthidium , based on similarities in the outline and structure of the valve, including A. rosenstockii (Lange-Bertalot) Lange-Bertalot ( Krammer & Lange-Bertalot 2004: 433), A. rosenstockii var. inareolatum Lange-Bertalot ( Krammer & Lange-Bertalot 2004: 433), A. capitatum Riaux Gobin, Romero, Compère & Al Handal ( Riaux-Gobin et al. 2011: 13) and A. trinode Ralfs ( Krammer & Lange-Bertalot 2004: 286). The morphological characteristics A. uniporatus and these similar species are summarized in Table 5 to facilitate a comparison. The width of K. sichuanenis is narrower (3.2–3.7 μm) than A. rosenstockii var. inareolatum (4.2–5.1 μm), A. capitatum (4–5 μm), and A. trinode (5–6 μm). On the raphe valve, K. sichuanenis has a small oval central area, while A. rosenstockii var. inareolatum and A. capitatum have no central area, and A. trinode possesses a round central area. Additionally, the density of striae at the apices of K. sichuanenis is higher on both the raphe (28–30/10 μm) and rapheless (28–32/10 μm) valves than in A. rosenstockii var. inareolatum (20/10 μm at the apices on both valves) and A. capitatum (22–25/10 μm on the raphe valve), but less than A. trinode (30–35/10 μm on both valves). Furthermore, the distal ends of raphe are straight, small, and drop shaped in K. sichuanenis , but in A. capitatum they are gently and doubly hooked on the same side. Moreover, the proximal raphe ends are straight, small, and drop shaped in K. sichuanenis , while A. capitatum are relatively close. Additionally, striae are comprised of one macroareola on both valves in this new species, but the number of areolae per striae of A. rosenstockii is 2–4 on the raphe valves and 3–4 on the rapheless valves, and A. trinode is 5–9 on the raphe valves and 4–7 on the rapheless valves.

Kolbesia sichuanenis is clearly different from the other species when compared to the genus Kolbesia based on the new species linear-lanceolate shape, while the other species are elliptical, linear-elliptical, elliptical-lanceolate (e.g., K. amoena , K. gessneri , K. kolbei , K. nitidiformis , K. ploenensis , and K. suchlandtii ), or linear ( K. sinica ). Additionally, the width of K. sichuanenis usually does not exceed 4 μm, while other species are wider, including K. amoena , K. nitidiformis , K. suchlandtii (up to 5 μm), K. kolbei (up to 7.5 μm), K. ploenensis (up to 6 μm), K. gessneri (up to 7 μm), and K. suchlandtii (up to 5 μm).

Figures

FIGURES 356–404. Kolbesia sichuanenis sp. nov. 356–378. LM of raphe valve. 379–402. LM of rapheless valve. 356, 379. Holotype. 403–404. SEM views of raphe valve. 403. External view of an entire raphe valve. 404. Internal view of an entire raphe valve. Scale bars 10 μm (356–402), 1 μm (403–404).

FIGURES 405–408. Kolbesia sichuanenis sp. nov. SEM views of rapheless valve. 405. External view of an entire rapheless valve. 406. Internal view of an entire rapheless valve. 407. Detail of the areolae on the external of the rapheless valve. 408. Internal areola openings with fine hymenate structures. Scale bars 1 μm (405–406), 0.2 μm (407–408).