Gomphonema 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 : 260

Gomphonema capitatum Ehrenberg ( Figs 228–236 , 295–298 )

Length: 28.7–37.3 μm, breadth: 10.3–12.7 μm, striae: 12–13 in 10 μm. This population from Lake Baikal mostly closely resembles individuals of G. capitatum sensu Reichardt (2009) . Our individuals, however, appear slightly more robust in their shape as compared to Reichardt’s. Since we do not have a broader range of variation within the diminution series, we are hesitant to recognize this population from Lake Baikal as different from Reichardt’s. However, we do not exclude the possibility that in future this group can be described as independent taxon. SEM: valve exterior has uniseriate striae with volate occlusions that give areolae C - shaped openings ( Figs 295–298 ). Striae extend from the valve face to the mantle ( Figs 295–298 ). The raphe is undulate. Stigmal opening is small, round ( Figs 295, 296 ). Apical pore field is barely on the valve face, almost exclusively on the mantle. It is bisected by the distal raphe end. Porelli are differentiated from the areolae ( Fig. 298 ).

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 292–297. SEM. 292. Gomphonema cf. truncatum. External views. Footpole, with deflected distal raphe end and apical pore field mostly on the valve mantle. Porelli are physically separated from and morphologically differentiated from C-shape areolae. 293. Valve view with undulate raphe and C-shaped areolae distinct. 294. Gomphonema paracapitatum sp. nov., external view. Girdle view showing wedge-shaped frustule and extension of striae from valve view onto mantle. 295–297. Gomphonema capitatum, external views. 295. General valve view. 296. Central area with distinct C-shaped areolae. Proximal raphe ends are dilated weakly. 297. Headpole, Cshaped areolae evident. Scale bars = 1 μm in Fig. 292; 5 μm in Figs 293, 294; 10 μm in Fig. 295; 2 μm in Figs 296, 297.

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.