Eunotia filiformis, Luo & You & Yu & Pang & Wang, 2019

Luo, Fen, You, Qingmin, Yu, Pan, Pang, Wanting & Wang, Quanxi, 2019, Eunotia (Bacillariophyta) biodiversity from high altitude, freshwater habitats in the Mugecuo Scenic Area, Sichuan Province, China, Phytotaxa 394 (2), pp. 133-147 : 137

Eunotia filiformis sp. nov. ( Figs 19–27 ; holotype = Fig. 21 )

Valve gently bent, ventral and dorsal margins parallel, ends not noticeably or only slightly inflated, broadly rounded. Length 86–100 μm, breadth 3–4 μm. Striae straight and parallel on the entire valve, 15–18/10 μm ( Fig. 27 ). Under SEM, striae uniseriate, areolae round with polygonal velum, 40–50/10 μm ( Fig. 26 ). External valve proximal raphe fissures at the junction between valve face and mantle, terminal raphe fissures curving in an angle of 180° back from apical nodules on the valve ( Figs 25–26 ). Internal valve showed a hyaline field in the position of external terminal raphe fissures, a single rimportula at one apex of a valve ( Figs 23–24 ).

Locality: China. Sichuan Province: Mugecuo Scenic Area, 30º11′13″N, 101º52′26″E. The new species was found in Mugecuo Lake, collected by Q-X. Wang, J-G. Cao, & Y. Cao et al. in August 2015.

Holotype: SHTU! slide and material SC201508039, Biology Department Diatom Herbarium , Shanghai Normal University, Shanghai, China, here illustrated as Fig. 21 .

Isotypes: COLO! Material 629039, University of Colorado, Museum of Natural History Diatom Herbarium, Boulder, USA.

Etymology: This species is named for its slim valve.

Remarks: Lange-Bertalot et al. (2011) identified this species as Eunotia . aff. E. julma Lange-Bertalot ( Lange-Bertalot et al., 2011: 130), and aff. E. latitaenia Kobayasi, Ando & Nagumo ( Kobayasi et al., 1981: 100). Eunotia aff. E. julma and aff. E. latitaenia are not in line with international nomenclature. Moreover, Lange-Bertalot did not give a formal description and instead only provided photographs for this species. Therefore, we described this species in detail as E. filiformis sp. nov.

E. filiformis has a more narrow valve and more dense striae compared to E. julma (breadth 4.5–5 μmɼ striae 14–16/10 μm) ( Lange-Bertalot et al., 2011). E. filiformis differs from E. latitaenia (breadth 5–7 μmɼ striae 11–14/10 μm) ( Kobayasi et al., 1981) by the narrower valves, denser striae, and by the consistently shorter terminal raphe fissure ( Lange-Bertalot et al., 2011). In addition, the difference between E. filiformis and E. gallica Lange-Bertalot & Witkowski ( Lange-Bertalot et al., 2011: 108) is that E. gallica (Length 90–180 μm, breadth 4–4.7 μm)has a wider valve and more pronounced end ( Lange-Bertalot et al., 2011).

Habitats: The collected material was a mixture of epiphytic (i.e., filamentous algae) and epilithic material in Qisehai Lake. Sample number: SC201508039. This species was rare in our sample, with only 3–5 observations in a slide.

Distribution: Finland ( Lange-Bertalot et al., 2011); China (This paper)

Figures

FIGURES 19–27. E. filiformis sp. nov. 19–22. LM images; 21. Holotype; 23–27. SEM images; 23–24 Terminal ends of internal valve, arrow show a hyaline areas; 25–26. Terminal ends of external valve, arrow show terminal raphe fissures; 27. External valve view. LM scale bars, 10 μm.