Gomphonema laticollum Reichardt, 2001

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 : 258

Gomphonema laticollum Reichardt ( Figs 167–175 , 275–281 )

Length: 24.7–42.7 μm, breadth: 9.7–11.3 μm, striae: 11–12 in 10 μm. Population from Lake Baikal is characterized by narrower valves in comparison with type population. Gomphonema laticollum as illustrated by Metzeltin et al. 2009 (pl. 167, figs 1–7) is a mixture of two different taxa. Figures 1–3 in Metzeltin et al. 2009: pl. 167 resemble individuals of G. laticollum illustrated here from Lake Baikal, while their figures 4–5 are interpreted by us to represent an independent, smaller taxon. SEM: externally, the valve has uniseriate striae with areolae that have volae giving a C - shaped appearance to the openings ( Figs 275–278 ). The raphe is strongly undulate. External proximal raphe ends are dilated slightly and deflected weakly towards the round stigma opening. External distal raphe ends are deflected to the side opposite the stigma opening and onto the valve mantle ( Figs 275, 276, 278 ). The bilobed apical pore field is positioned mostly on the mantle and comprised of porelli that are morphologically differentiated from the areolae. Internally, there are prominent helictoglossae, pseudosepta at the poles, and a central nodule bearing the proximal raphe ends and the stigma opening ( Figs 279–281 ).

Figures

FIGURES 167–186. LM. 167–175.Gomphonema laticollum. 176–190.Gomphonema microlaticollum sp. nov. Fig.178 is of the holotype. Scale bar = 10 μm.

FIGURES 274–279. SEM. 274. Gomphonema angusticephalum. External view of footpole, showing deflected distal raphe end bisecting bilobed pore field. Porelli are differentiated from C-shaped areolae. 275–279. Gomphonema laticollum. 275–278. External viws. 279. Internal view. 275, 276. Whole valve views showing outline of the valves. 277. Central area with undulate raphe dilated proximal raphe ends and round stigma opening evident. C-shaped areolae dominate the valve. 278. Headpole showing C-shaped areolae and hooked distal raphe end. 279. Valve view with central nodule, helictoglosae and note presence of pseudosepta. Scale bars = 1 μm in Fig. 274, 2 μm in Figs 277, 278; 5 μm in Figs 275, 276, 279.

FIGURES 281–285. SEM. 280–281. Gomphonema laticollum, internal views. 280. Footpole, raphe terminating in helictoglossa. There is a pseudoseptum present.282–285.Gomphonema microlaticollum sp. nov., external views. 282, 284. Whole valve views. 283, 285. Central areas with biseriate striae, round stigma opening and dilated proximal raphe ends evident. Scale bars = 1 μm in Figs 280, 281, 283, 285; 2 μm in Figs 282, 284.

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