Gomphonema cf. capitatum Ehrenberg, 1838

Kulikovskiy, Maxim S., Kociolek, John P., Solak, Cüneyt N. & Kuznetsova, Irina, 2015, The diatom genus Gomphonema Ehrenberg in Lake Baikal. II. Revision of taxa from Gomphonema acuminatum and Gomphonema truncatum-capitatum complexes, Phytotaxa 233 (3), pp. 251-272 : 262-263

Gomphonema cf. capitatum Ehrenberg ( Figs 244–255 , 299–301 )

Valves clavate, swollen at the center. Central undulation slightly lager than headpole. Length: 30–38 μm, breadth: 9.3–10.7 μm. Headpole is broadly rounded, capitate, with fooptopole narrower. Axial area is narrow. Central area small, rectangular. Raphe lateral, undulate. Stigma isolated and distinct. Striae punctate, radiate, more radiate at the footpole, 11–12 in 10 μm. SEM: valve exterior shows striae with C - shaped opening of the areolae produced by volate occlusions ( Figs 299–301 ). Raphe is undulate, with proximal ends slightly dilated, and distal ends deflected onto the mantle.

Observations: —This population is distinguished from G. capitatum as shown by Reichardt (2001) by its smaller size, more elongate shape, and lower number of striae in 10 μm.

Figures

FIGURES 228–255. LM. 228–236. Gomphonema capitatum. 237–243. Gomphonema microcapitatum sp. nov. Fig. 238 is of the holotype. 244–255. Gomphonema cf. capitatum. Scale bar = 10 μm.

FIGURES 298–301. SEM. 298. Gomphonema capitatum, external view, footpole with apical pore field restricted almost entirely to the valve mantle. Pore field bisected by deflected distal raph end. C–shaped areolae evident. 299–301. Gomphonema cf. capitatum, external views. 299. General valve view. 300. Headpole with distal raphe end deflected onto mantle. Striae with C-shaped areolae continue from valve all around the mantle. 301. Central area. Undulate raphe is distinct. Striae formed of C-shaped areolae. Scale bars = 2 μm in Figs 298, 300, 301; 5 μm in Fig. 299.