Gomphonema shanghaiensis W. Zhang & Kociolek, 2016

Zhang, Wei, Xu, Xiao-Ying, Kociolek, J. Patrick & Wang, Li-Qing, 2016, Gomphonema shanghaiensis sp. nov., a new diatom species (Bacillariophyta) from a river in Shanghai, China, Phytotaxa 278 (1), pp. 29-38 : 31-32

Gomphonema shanghaiensis W. Zhang & Kociolek , sp. nov. ( Figs 1–30 )

Light microscopy: valves narrowly-lanceolate to rhombic-lanceolate, slightly asymmetrical to the apical axis, with a gibbous central portion. Footpole rounded and headpole slightly rostrate to narrowly-rounded ( Figs 1–8 ). Valve length 45.9–74.8 μm, breadth 9.8– 12.5 μm, length/breadth ratio 4.6–5.9 (n=37). Raphe straight, filiform for most of its length, slightly lateral near the central area. Axial area narrow, linear. Center area small, irregularly rectangular in shape, unilaterally widened, formed by one short stria being slightly more distant from others. 1–5 rounded external stigmal openings present in or around the central area ( Figs 1–8 ). Striae slightly radiate at the center and towards the headpole, radiate towards the footpole. Striae number 14–16/10 μm (mostly 14–15/10 μm) in the middle of the valve, becoming up to 17–19/10 μm towards the ends. Areolae not discernible in LM. Prominent bilobed apical pore field (APF) at the footpole separated from the striae by a smooth area ( Figs 1, 2, 4 ). Small septa and pseudosepta at head and footpole. Scanning electron microscopy: valve exterior has a linear, straight axial area, a straight and mostly filiform raphe ( Figs 9–11 ). External proximal raphe endings slightly expanded and dilated. Distal raphe ends deflected in the same direction onto the valve mantle ( Fig. 11 ). Striae uniseriate, occasionally biseriate near the headpole ( Figs 15–21 ), with C-shaped, curved, irregularly S- or 3-shaped areolae. 1–5 round external stigmal openings present at the end of individual striae in the central area ( Figs 15–20 ). At the footpole the distal raphe end bisects the porelli of the APF. The APF is composed of round, unoccluded porelli and extends from the valve face across the mantle ( Fig. 22 ). Porelli, of differing sizes, are physically separate and morphological differentiated from the valve face areolae ( Fig. 22 ). Porelli number 60–70/10 μm. Internally, the central nodule is rounded and a distinct helictoglossa is present at each pole ( Figs 12–14 ). The helictoglossae are offset to one side of the axial area and appears elevated on a ridge of silica ( Figs 29, 30 ). Internal proximal raphe ends bend at a slightly acute angle and deflected in opposite directions ( Figs 23–28 ). 1–5 slitlike or elliptical stigmal openings are present on the primary or secondary sides of the center area ( Figs 23–28 ). A pseudoseptum is present at each pole ( Figs 29, 30 ).

Type:— CHINA. Shujiawan River, Baoshan District, Shanghai, 31° 29’ 6.2” N, 121° 19’ 15.8” E, X. Y. Xu, 12 January 2016 (holotype: Laboratory of Aquatic Ecology and Environmental Restoration, Department of Hydrobiology, College of Fisheries and Life Science, Shanghai Ocean University, slide Shujia 01, illustrated in Fig. 1 . Isotype COLO, slide deposited in the J.P. Kociolek Collection).

Etymology:— Gomphonema shanghaiensis is named after the type locality.

Figures

FIGURES 1–8. Light microscopy of Gomphonema shanghaiensis, valve views showing the size diminution series. Scale bar = 10 μm.

FIGURES 9–14. Gomphonema shanghaiensis W. Zhang & Kociolek, SEM. External and internal views. 9–11. Exterior view of a whole valve, showing the valve variability, straight raphe with rounded proximal ends, gibbous center portion, round foot pole and rostrate to narrow round headpole. 12–14. Interior view of differently shaped whole valves, showing pseudosepta at both ends and offset helictoglossae. Scale bars = 10 μm.

FIGURES 15–22. Gomphonema shanghaiensis, SEM. External view. 15–20. Centre of valve exterior of six different specimens. Slightly expanded and dilated proximal raphe ends, striae composed of “C” shaped or round areolae. 21. External view of the headpole with the external distal raphe end curving onto the valve mantle. 22. Exterior of valve showing the deflected apical end of raphe and rounded porelli. Scale bars = 2 μm (Figs 15–21) and 1μm (Fig. 22).

FIGURES 23–30. Gomphonema shanghaiensis, SEM. Internal view. 23–28. Internal center. Deflected central raphe endings, internal openings of the stigmata. 29. Interior view of the headpole showing the large helictoglossae and pseudosepta.30. Internal view of footpole showing the helictoglossae, pseudosepta and raphe slit. Scale bars = 2 μm.