Gomphonema acuminatum Ehrenberg, 1832

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 : 252

Gomphonema acuminatum Ehrenberg ( Figs 1–21 , 25–45 , 256–259 )

Length: 30–48 μm, breadth: 7.3–9.3 μm, striae: 9–12 in 10 μm. Morphology of this species in Lake Baikal shown in Figs 1–21 is identical to those illustrated and discussed by Reichardt (1999). An interesting group of valves is shown in Figs 25–45 . These valves are characterized by evidently coarser striae, shorter striae in the central part and larger central area. However, measurements of valves have shown that the individuals in Figs 25–45 are almost identitical to individuals with a more typical appearance, thus it is not possible currently to separate this group. SEM: external views of this species ( Figs 256–259 ) appear to be ‘smeared’ with silica. The proximal raphe ends are slightly dilated, and the stigma opening is round ( Figs 256, 257 ). Distal raphe ends are strongly deflected ( Figs 258, 259 ). Apical pore field porelli are restricted to the mantle, and bisected by the distal raphe ends. Porelli are morphologically distinct form the C - shaped areolae ( Fig. 259 ).

Figures

FIGURES 1–24. LM. 1–21. Gomphonema acuminatum. 22–24. Gomphonema brebissonii. Scale bar = 10 μm.

FIGURES 25–45. Gomphonema acuminatum. LM. Scale bar = 10 μm.

FIGURES 256–261. SEM.256–261. Gomphonema acuminatum. External views. 256. External view of central area to headpole.Proximal and distal ends evident. 266. Central area with dilated proximal raphe ends and small, round stigma opening evident. 258. Headpole showing protracted apex and hooked distal raphe end. 259. Footpole with deflected distal raphe end bisecting apical pore field on the valve mantle. 260, 261. Gomphonema pseudacuminatum sp. nov., external views. 260. Entire valve view showing valve proportions. 261. Central area with dilated proximal raphe ends, small elliptical stigma opening and occlusion of areolae resulting in C-shaped openings. Scale bars = 5 μm in Figs 256, 260, 2 μm in Fig. 258, 1 μm in Figs 257, 259, 261.