Gomphonema californicum Stancheva & Kociolek, 2016

Stancheva, Rosalina, Sheath, Robert G. & Kociolek, J. Patrick, 2016, New Freshwater Gomphonemoid Diatoms from Streams in the Sierra Nevada Mountains, California, USA, Phytotaxa 289 (2), pp. 118-134 : 120

Gomphonema californicum Stancheva & Kociolek , sp. nov. ( Figs 1–27 )

LM observations

Valves are lanceolate-clavate with rounded head pole and narrower foot pole. Cells are 5.6–8.3 μm wide, 22–67 μm long ( Figs 1–13 ); initial cell 10 μm wide, 71 μm long ( Fig. 14 ). Striae are slightly radiate at the center of the valve 10–13 in 10 μm, becoming denser up to 15 in 10 μm near both apices and strongly radiate toward the foot pole. Striae composed of areolae, which are coarser and distinguishable near the head pole, 28–32 in 10 μm. Striae sometimes are interrupted, particularly around the central area ( Figs 2 and 3 ). Axial area narrow, lanceolate. One, occasionally two median striae on both sides of the central area are shorter than the others ( Figs 4–6 ). Central area is rectangular transversely extended, delimited by two or three curved striae ( Figs 2, 6, 8, 10 ), rarely elliptical ( Fig. 4 ). One isolated stigma is positioned close to the proximal raphe ends. Sometimes one or a few small indistinct depressions are present in the central area, not easily resolvable with LM ( Fig. 2 ). The raphe is lateral, slightly undulate. Frustules are slightly cuneate in girdle view with single or double irregular rows of puncta on each mantle, in some specimens interrupted near the middle ( Figs 12 and 13 ).

Figures

FIGURES 1–14. Gomphonema californicum Stancheva & Kociolek, sp. nov., LM images.Figs 1, 4, 5, 6 (type material, site 507DCABSF). Figs 3, 10, 12, 13, 14 (site 518RCNAPC). Figs 2, 7, 8, 9, 11 (site 521BTC303). Figs 1–11 valve view. Figs 12 and 13 girdle view; note that the focus on Fig. 13 is on the apical spines. Fig. 14 initial valve. Scale bar: 10 μm.

FIGURES 15–21. Gomphonema californicum Stancheva & Kociolek, sp. nov. type material from Digger Creek, California, USA (site 507DCABSF). SEM images. Figs 15, 16, 19, 20 external valve view. Figs 17, 18, 21 external girdle view. Figs 17, 18, 19, 21 show an apical spine at the head pole (white arrows). Fig. 20 illustrates narrow, unornamented area within the apical pore field at the foot pole (white arrowheads). Figs showing the same specimen are: 15 and 19; 16 and 20; 18 and 21. Scale bars: Figs 15–18 = 10 μm; Figs 19–21 = 2 μm.

FIGURES 22–27. Gomphonema californicum Stancheva & Kociolek, sp. nov. type material from Digger Creek, California, USA (site 507DCABSF).SEM images.Figs 22 and 23 show external valve view of the central area with isolated stigma and small depressions (white arrows), surrounded by short striae composed of areolae with variable shape. Figs 24–27 internal valve view. Figs 25 and 26 illustrate the interval view of the central nodule, bearing a slit-like stigma opening and dilated and recurved proximal raphe ends. Figs showing the same specimen are: 24 and 25; 26 and 27. Scale bars: Figs 24, 27 = 10 μm; Figs 22, 23, 25, 26 = 2 μm.