Gomphonema bicepiformis Wei Zhang & Kociolek, 2018

Zhang, Wei, Shang, Guang-Xia, Kociolek, J. Patrick, Wang, Li-Qing & Tan, Hong-Xin, 2018, Gomphonema bicepiformis sp. nov., a new diatom species (Bacillariophyta) from a stream in Zhejiang, China, Phytotaxa 375 (4), pp. 274-282 : 275-276

Gomphonema bicepiformis Wei Zhang & Kociolek , sp. nov. ( Figs 1–30 )

Light microscopy: Valves lanceolate, swollen at central area, constricted then broadening into rounded, capitate footpole; headpole rounded, clearly capitate ( Figs 1–14 ). Length 30.0–41.5 μm, breadth 8.0–9.3 μm. Length: Breadth ratio 3.7–4.7, median 4.2 (n= 60). Striae short, moderately radiate, 14–15 in 10 μm. Axial area wide, lanceolate-rhombic, broad at mid-valve, reaching 3/4 of total breadth. Circular depressions in axial area on external valve surface, often appearing as light spots in LM ( Figs 1–14 ). Raphe expanded laterally, only slightly undulate. Prominent apical pore field (APF) present at footpole. Small stigma situated near central nodule ( Figs 1–14 ).

Scanning electron microscopy: Valve face separated from mantle by small marginal ridge ( Figs 15–27 ). No clear groove along ridge on valve face, but it protrudes over mantle ( Figs 22–24 ). Raphe slightly undulate, but mostly filiform ( Figs 15–19 ). External proximal raphe ends slightly expanded and dilated ( Fig. 22 ). Distal raphe ends deflected in same direction onto valve mantle ( Figs 15–19 ). Axial area wide, rhombic, with circular and some irregular depressions along its entire length ( Figs 20–27 ). Striae uniseriate, occasionally biseriate near headpole ( Figs 20, 21 ), with slitshaped, curved, or irregularly triangular-shaped areolae. One small, irregularly rectangular external stigmal opening present near central nodule ( Figs 22, 23 ). At footpole distal raphe end bisects porelli of APF. APF composed of round, unoccluded porelli, extending from valve face across mantle ( Figs 26, 27 ). Porelli, of differing sizes, physically separate and morphological differentiated from valve face areolae ( Figs 26, 27 ). Irregular, shallow depressions in hyaline area between valve face areolae and porelli ( Figs 26, 27 ). Internally, central nodule rounded, distinct helictoglossa present at each pole ( Figs 28–31 ). Internal proximal raphe ends bend at slightly acute angle and deflected in opposite directions ( Fig. 29 ). One slit-like stigmal opening present on primary side of center area ( Fig. 29 ). Pseudoseptum present at each pole ( Figs 30–31 ).

Type: — CHINA. Shibadukeng stream, Xianju County, Taizhou City, Zhejiang Province, 28°44’24.88”N, 120°30’57.96”E, R.L. Zhang, 20 May 2016 (Holotype SHOU! Department of Hydrobiology, College of Fisheries and Life Science, Shanghai Ocean University ( SHOU), Shanghai. Individual in slide Shibadukeng 04. Isotype COLO, slide deposited in the J.P. Kociolek Collection).

Etymology: —The specific epithet “ bicepiformis ” refers to the bi-capitate poles, being similar in outline to G. biceps .

Figures

FIGURES 1–14. Light microscopy of Gomphonema bicepiformis W. Zhang & Kociolek, valve views showing the size diminution series. Scale bar = 10 μm.

FIGURES 15–19. Gomphonema bicepiformis W. Zhang & Kociolek, SEM. Exterior view of a whole valve, showing the valve variability of the holotype, slightly undulate raphe with rounded proximal ends, gibbous central portion, round, capitate foot pole and headpole. Scale bars = 10 μm.

FIGURES 20–27. Gomphonema bicepiformis, SEM. External view. 20–21. External view of the capitate headpole with the external distal raphe end curving onto the valve mantle. Striae uniseriate, mostly composed of slit-like, “C-” shaped or triangular areolae, occasionally biseriate. 22–24. External view of the central portion of the valve showing wide axial area with circular and irregular depressions, smallll and rectangular stigma, small marginal ridge separating the valve face from the mantle. 25. External view of the valve face between the central portion and footpole showing irregular depressions and biseriate striae. 26–27. External view of the capitate footpole with the deflected distal end of raphe, rounded porelli and irregular shaped depressions at valve terminus. Scale bars = 2 μm.

FIGURES 28–31. Gomphonema bicepiformis, SEM.Internalview.28.Whole valves,showing pseudosepta at bothends andhelictoglossae. 29. Central portion of the valve showing deflected central raphe endings, and internal opening of the stigma. 30. Interior view of the headpole showing the small helictoglossa. 31. Internal view of footpole showing the helictoglossa, pseudoseptum and raphe slit. Scale bars = 10 μm(Fig. 28), 2 μm(Figs 29–31).