Halamphora subfontinalis, You & Kociolek & Wang, 2015

You, Qingmin, Kociolek, John Patrick & Wang, Quanxi, 2015, Taxonomic studies of the diatom genus Halamphora (Bacillariophyceae) from the mountainous regions of southwest China, including the description of two new species, Phytotaxa 205 (2), pp. 75-89 : 77-80

Halamphora subfontinalis Q.-M. You & J.P. Kociolek, sp. nov. ( Figs. 1–19 )

Valves semi-lanceolate, dorsiventral with convex dorsal margin and less convex ventral margin. Valve ends protracted and weakly capitate. Length 30.8–38.5 μm, valve breadth 5.0–6.4 μm. Externally, the raphe is weakly arched and both proximal and distal raphe ends are deflected or curved towards the dorsal margin of the valve ( Figs. 12, 13, 15 ), proximal raphe ends rounded ( Figs. 12, 13 ). A dorsal raphe ledge is present ( Figs. 12, 13 , arrows). The axial area is narrow on the dorsal side, and on the ventral side is expanded into a wide hyaline area/fascia, and widens quickly from the apices towards the valve center, creating a semi-lanceolate axial area ( Figs. 10, 12, 13 ). Dorsal part of the valve with a small rectangular unornamented area in the center, the first row of axial dorsal areolae is elongate and biseriate ( Fig. 12 ). Ventral margin with one row of continuous elongate areolae ( Fig. 13 ). Striae slightly radiate throughout, 17–21/ 10 μm at mid–valve, 18–22/10 μm near the ends. Internally, the thickened central virgae are evident on the dorsal side ( Fig. 14 ). The proximal raphe ends terminate at a narrow central helictoglossae ( Fig. 14 ). Distally, the internal raphe ends terminate as helictoglossae ( Fig. 16 ). Girdle bands are numerous, and on the ventral side with two rows of round poroids ( Figs. 17–19 ).

Type:— CHINA. Yunnan: Weixi (holotype SHTU!, slide 064304, illustrated in Fig. 1 ).

Etymology:— This species is named for its similarity to H. fontinalis .

Distribution and ecology:— Weixi, Yunnan, China, altitude 1929 m a.s.l., collected in mountain river; Lijiang, Yunnan, China, altitude 2795 m a.s.l., pH 7.9, collected in meadow stream.

Observations:— The valve outline of this species is similar to H. fontinalis ( Hustedt 1937: 414) Levkov (2009: 190) , however H. fontinalis has a straighter ventral margin, and the dorsal striae are shortened at the center. Ventral striae are indistinct in the LM. For H. fontinalis , while in the SEM striae are seen to be uniseriate throughout the valve, with one row of areolae at ventral margin interrupted at the center ( Levkov 2009). Our species has an evident convex ventral margin, dorsal striae are longer at the center and distinct in the LM, the dorsal striae near the raphe is composed of biseriate areolae, and areolae on the ventral margin are continuous. H. subfontinalis may also be compared with H. punctata Stepanek & Kociolek (2013: 70) , a species much smaller (length 15–25 μm, valve breadth 3.5–4.5 μm) and having striae in center of the valve that are not interrupted.

Figures

FIGURES 1–16. Halamphora subfontinalis, sp. nov. 1–9. LM. Valve views showing size diminution series. Figure 1 is of the holotype. Scale bars = 10 μm for all LM figures. 10–16. SEM. 10, 12, 13, 15, external views. 10. Entire valve showing shape of the valve. 12, 13. View of central area with curved proximal raphe, as well as raphe ledge (see arrows). 15. View of valve end with curved raphe end. 11, 14, 16, internal views. 11. Entire valve view. 14. Central area with evident thickened central virgae. 16. View of valve end, with helictoglossa. Scale bars show in each SEM figure.

FIGURES 17–19. Halamphora subfontinalis, sp. nov. SEM. 17. External view of the frustule. 18. View of central area with numerous girdle bands. 19. View of frustule end, each girdle band with two rows of round poroids. Scale bars show in each SEM figure.