Halamphora hezhangii, 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 : 80-81

Halamphora hezhangii Q.-M. You & J.P. Kociolek, sp. nov. ( Figs. 20–34 )

Valves semi-lanceolate, dorsiventral with convex, weakly undulated dorsal margin and ventral margin concave in the middle, slightly convex near the end. Valve ends protracted and capitate. Length 38.2–43.5 μm, valve breadth 6.4–7.0 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. 28, 30–32 ). External proximal raphe ends rounded ( Fig. 31 ). Dorsal raphe ledge small, and more or less expanded near the poles. Axial area linear. Dorsal part of the valve with coarse, dash-like, biseriate areolae ( Figs. 30, 31 , see arrows). Striae slightly radiate throughout, 14–16/ 10 μm. Internally, The proximal raphe ends terminate at a narrow central helictoglossae ( Fig. 33 ). Distally, the internal raphe ends terminate as helictoglossae ( Fig. 34 ).

Type:— CHINA. Guizhou: Hezhang (holotype SHTU!, slide GZ09001, illustrated in Fig. 24 ).

Etymology:— This species is named after Hezhang County, as it is only known from this region.

Distribution and Ecology:— Hezhang, Guizhou, China, altitude 1450 m a.s.l., pH 7.2, collected in the pond near the road, with many filamentous green algae present.

Observations:— Our species has similar valve outline with Halamphora acutiuscula ( Kützing 1844: 108) Levkov (2009: 167) . However, H. acutiuscula differs from the species from Hezhang County by having a smooth dorsal margin, evident widened axis area and finer striae density, up to 22/ 10 μm. Halamphora hezhangii also resembles H. holsatica ( Hustedt 1925: 115) Levkov (2009: 196) in size and striae density, however the two species are distinguished from one another by many different characters. Halamphora holsatica has valves with a convex dorsal margin and straight ventral margin, sometimes with a slight central inflation. The dorsal striae in H. holsatica are uniseriate with transapically elongated areolae that occasionally alternate with small circular ones. From an internal view, the valves of H. holsatica show that the first areola of each stria is different in shape from the others by being wider than long. The ventral striae in H. holsatica are denser and consist of only a single row of small linear to circular areolae. The central area in H. holsatica is small, and two proximal raphe ends are much closer with each other ( Wang et al. 2014). These features all differentiate H. holsatica from H. hezhangii .

Figures

FIGURES 20–34. Halamphora hezhangii, sp. nov. 20–27. LM. Valve views showing size diminution series. Figure 24 is of the holotype. Scale bars = 10 μm for all LM figures. 28–34. SEM. 28, 30–32. External views. 28. Entire valve showing shape of the valve. 30. Show of dash–like areolae composed of biseriate, which distinctly in several rows of axial areolae near the raphe ledge. 31. View of central area with curved proximal raphe. 32. View of curved distal raphe end. 29, 33, 34. Internal views. 29. Entire valve view. 33. Central area with a narrow central helictoglossae. 34. View of valve end, with curved distal raphe ends and helictoglossa. Scale bars show in each SEM figure.