Halamphora daochengensis W. Zhang, Jüttner & Levkov, 2019

Zhang, Wei, Wang, Ting, Levkov, Zlatko, Jüttner, Ingrid, Ector, Luc & Zhou, Qi-Chao, 2019, Halamphora daochengensis sp. nov., a new freshwater diatom species (Bacillariophyceae) from a small mountain lake, Sichuan Province, China, Phytotaxa 404 (1), pp. 12-22 : 14

Halamphora daochengensis W. Zhang, Jüttner & Levkov sp. nov. ( Figs 1–25 )

LM: Valves dorsiventral, moderately arched, with triundulate, convex dorsal margin, straight to slightly concave ventral margin ( Figs 1–9 ). Valve ends protracted, capitate. Dimensions: length 34.3–40.8 μm, width 5.4–6.9 μm. Axial area very narrow, central area indistinct. Raphe arched, proximal ends weakly expanded, slightly dorsally deflected, distal ends dorsally deflected. Dorsal striae with fine punctuation, slightly radiate throughout, 23–25(27) in 10 μm dorsally at valve centre, 24–27 in 10 μm ventrally, 28–30 in 10 μm near valve ends.

SEM: Externally, raphe located in flat, narrow ledge, slightly wider in valve centre ( Figs 10, 11 , 14, 17 ). Ledge ornamented with shallow, non-penetrating depressions, rounded or irregular in shape with variable size ( Figs 14, 17 ). Striae uniseriate, composed of elongate areolae of variable length ( Fig. 10–19 ). Dorsally, striae continuing uninterrupted onto mantle, mantle with 3–4 rows of areolae of variable length in valve centre, and one row of elongate areolae near valve ends ( Figs 12, 13 ). Ventrally, striae composed of one row of transapically elongated areolae ( Figs 11 , 14–16 ). Girdle bands open, each bearing one or two rows of rounded or slightly transapically elongated poroids similar in size to ventral areolae ( Figs 14–16 , 20, 24 ). Internally, distal raphe ends slightly ventrally deflected terminating in large helictoglossae ( Figs 22, 23 ). Proximally, raphe ends terminating in wide fused central helictoglossa ( Fig. 25 ).

Type: — CHINA. Sichuan Province: Tibetan Autonomous Prefecture of Garzi, Daocheng County, Haizishan Nature Reserve , Lake Congqiancuo , 29°21′58″ N, 100°04′51″E, elevation 4389 m a.s.l., samples collected by Q.C. ZHOU, 20 Sep. 2018. Holotype NMW.C.2019.01! Amgueddfa Cymru — National Museum Wales, isotype slide CQC1#, SHOU! Department of Hydrobiology , College of Fisheries and Life Science, Shanghai Ocean University ( SHOU), Shanghai.

Etymology: —The specific epithet ‘ daochengensis ’ refers to the locality from which the new species was described.

Figures

FIGURES 1–9. LM micrographs of the type population of Halamphora daochengensis in Lake Congqiancuo. Figs 1–7. Valve views, showing the valve variability of the holotype population. Figs 8, 9. Light micrographs showing the frustule in girdle view. Scale bar = 10 μm.

FIGURES 10–13. SEM, external views. Fig. 10. External view of an entire valve. Fig. 11. Ventral view of entire frustule with girdle bands. Fig. 12. Entire valve seen from the dorsal side in oblique view showing the dorsal mantle and girdle bands. Fig. 13. Entire valve seen from the dorsal side showing the girdle band areolae. Scale bars = 10 μm.

FIGURES 14–19. SEM, detail of external valve views. Fig. 14. View of central area with numerous girdle bands. Figs 15, 16. View of frustule end and girdle bands with rows of rounded poroids. Fig. 17. External detail of the valve centre. Fig. 18. External detail of valve apex showing the prominent raphe ledge. Fig. 19. External detail of part of the dorsal valve, valve face/mantle margin and mantle. Scale bars =2 μm (Figs 14, 17), 3 μm (Fig. 18), 5 μm (Figs 15, 16, 19).

FIGURES 20–25. SEM, internal valve views. Fig. 20. Internal view of entire valve with girdle bands. Fig. 21. Oblique view of valve. Fig. 22, 23. Internal view of valve apex with prominent helictoglossa. Fig. 24. Internal view of valve centre with girdle bands. Fig. 25. Internal view of valve centre with fused helictoglossa. Scale bars = 2 μm (Figs 22, 23), 3 μm (Fig. 25), 5 μm (Figs 20, 21, 24).