Gomphonema bigutianchnensis Li, 2018

Liao, Meng-Na & Li, Yan-Ling, 2018, One new Gomphonema Ehrenberg (Bacillariophyta) species from a high mountain lake in Yunnan Province, China, Phytotaxa 361 (1), pp. 123-130 : 124-126

Gomphonema bigutianchnensis Li sp. nov. Figures 1–20 ; figure 1 is of the holotype.

Description: Valve gibbous in the center and biconstricted, with subacute headpole and footpole. Headpole is rounded or acutely rounded. Footpole is rounded ( Fig. 1 ). Valve length 36–51 μm, and breadth 5.5–6.3 μm at the center, breadth 6.5–8.1 μm at the widest point, near the headpole. Axial area is narrow. Raphe is undulate and distinctly lateral. Central area is large, laterally expanded and irregularly rectangular with two shortened median striae. Stigma distinctly separated from striae, close to the central nodule. Striae radiate, strongly so at the footpole.

Holotype: NIGLAS! The Museum of Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing. Individual in slide BGTC-200507.

Isotype: IHB! Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan. Individual in slide No. 14736.

Type Locality: Lake Bigutianchi, Yunnan Province.

SEM observations of the valve exterior show the c-shaped areolae and depressions or pitted nature of the axial area ( Figs 13–16 ). Striae number 11–15/10 μm and Puncta number 27–33/10 μm ( Figs 13–16 ). The raphe is undulate ( Fig. 13 ) and proximal ends are deflected in the same direction ( Fig. 15 ). A round stigma opening is present in the central area ( Figs 13, 15 ). External distal ends are deflected in the same direction and extend onto the valve mantle ( Figs 14, 16 ). At the footpole the distal raphe end bisects apical pore field with porelli clearly separated from the areolae ( Fig. 16 ). The apical pore fields are located entirely on the valve mantle. Internally, the valve has a conspicuous central nodule that bears a slit-like stigmal opening and proximal raphe ends deflected to one side and recurved ( Figs 17, 19 ). Distal raphe ends terminate as distinct helictoglossae ( Figs 18, 20 ). At the poles pseudosepta are visible ( Figs 18, 20 ).

Figures

FIGURES 1–12. Gomphonema bigutianchnensis, Light microscopy, valve views showing size diminution series for the species. Fig. 1 is the holotype. Scale bar = 10 μm for all images.

FIGURES 13–16. Gomphonema bigutianchnensis. SEM, external views. Fig. 13 Entire valve view showing c-shaped areolae, undulate raphe and round stigma opening. Scale bar = 3 μm. Fig. 14 View of the headpole with distal raphe end curved on the valve mantle and striae continuous around the headpole. Scale bar = 1 μm. Fig. 15 Central portion of the valve showing proximal raphe ends and rounded stigma opening. Scale bar = 1 μm. Fig. 16 Footpole with c-shaped areolae and apical pore field porelli physically separated from areolae and morphologically distinct from the areolae. Scale bar = 1 μm.

FIGURES 17–20. Gomphonema bigutianchnensis. SEM, internal views. Fig. 17 Entire valve view showing distinct central nodule and striae. Scale bar = 2 μm. Fig. 18 Headpole with distinct helictoglossa and small pseudoseptum at apex. Scale bar = 1 μm. Fig. 19 Central portion of the valve show central nodule with recurved proximal raphe ends and slit-like stigma opening. Scale bar = 1 μm. Fig. 20 Footpole with prominent helictoglossa and small pseudoseptum at the apex. Structure of the apical pore field is seen just beyond the pseudoseptum. Scale bar = 1 μm.