Oricymba voronkinae Glushchenko, Kulikovskiy & Kociolek, 2015

Kulikovskiy, Maxim, Glushchenko, Anton & Kociolek, John Patrick, 2015, The diatom genus Oricymba in Vietnam and Laos with description of one new species, and a consideration of its systematic placement, Phytotaxa 227 (2), pp. 120-134 : 127-129

Oricymba voronkinae Glushchenko, Kulikovskiy & Kociolek , sp. nov. ( Figs 74–113 )

LM ( Figs 74–101 ): valves narrow lanceolate or linear-lanceolate, with moderately arched valve margins gradually tapering towards the rounded, slightly protracted ends. Length 27–49 μm, breadth 8–11 μm. Raphe nearly central, with external proximal raphe ends turned toward stigma on the ventral side. One large rounded stigma present, easily distinguished in LM. Axial area lanceolate. Central area rhombic-lanceolate, slightly asymmetrical, about 1/3 of valve width. One central dorsal stria is shortened, ventral central striae visibly shortened. Striae parallel or slightly radiate, 9–10 in 10 μm. Individual areolae visible, about 20 in 10 μm. SEM, external view ( Figs 102–108 ): shape of the valve and the undulate raphe branches are evident at lower magnifications, as well as the marginal ridge of silica ( Figs 102, 103 ). The valve face has the narrowly rectangular striae, more rounded along the axial area, with dendritic projections below the surface of the valve. Axial area may be smooth or have small depressions along is length. Proximal raphe ends are dilated slightly, and deflected weakly towards the round stigma opening ( Figs 104, 105 ). The distal raphe end curves at nearly right angles, and does not bisect the apical pore fields, which are restricted to the valve mantle only. Porelli of the apical pore fields are physically removed and structurally differentiated from the areolae ( Figs 104, 105 ). In girdle view the striae extend from the valve face onto the mantle ( Fig. 108 ). The siliceous marginal ridge is evident ( Figs 106 , 108 ). SEM, internal view ( Figs 109–113 ): The valve interior is dominated by the asymmetrical central area, which bears an internally elevated ridge or mound ( Figs 109, 110 ), at the base of which there are two elliptical stigmal openings that are covered with fine siliceous dendritic structures ( Figs 110, 111 ). There are no evident proximal raphe ends, and the central raphe ends may be considered continuous. Alveolae are bordered by small siliceous granules ; the complex nature of the areolar coverings is evident from the interior ( Figs 111–113 ). Raphe terminates in helictoglossae, which are offset from the main axial area at both apices. Porelli of the apical pore fields are evident at the mantle of the apices ( Figs 112, 113 ). Type:— LAOS. Somphamit Waterfall, 15° 16.552’ N, 105° 55.538’ E, A. M. Glushchenko, 1 December 2011 (holotypus: IBIW!, individual in slide no. 00992, collection Maxim Kulikovskiy, I.D. Papanin Institute for Biology of Inland Waters , Russian Academy of Sciences, here illustrated as Fig. 75 ) .

Etymology:—species dedicated to Dr. Natalia Vladimirovna Voronkina, botanist from Kaluga State University, mentor of second author of this paper.

Distribution:—As far known only from the type locality.

Remarks:—This species differs from both O. japonica and O. perjaponica in the more linear outline of the valves and by the slightly protracted apices.

Figures

FIGURES 74–101. Oricymba voronkinae sp. nov. LM. Valve views showing size range. Holotype is illustrated in Fig. 75. Scale bar = 10 μm.

FIGURES 102–107. Oricymba voronkinae sp. nov. SEM, external views. 102, 103. Low magnification valve views showing arched raphe and round stigma opening. 104, 105. Central area with dilated proximal raphe ends and round stigma opening. Marginal ridge is evident. 106. View of striae with the overlay of silica to form the characteristic striae with subtending dendritic coverings. The marginal ridge is evident. 107. Apex with strongly hooked distal raphe end not bisecting the apical pore field. Pore field restricted to mantle. Scale bars = 10 μm in Figs 102, 103; 1 μm in Fig. 104; 2 μm in Fig. 105; 0.5 μm in Figs 106, 107.

FIGURES 108–113. Oricymba voronkinae sp. nov. 108. external view. 109–113, internal views. 108. Girdle view showing distinct marginal ridge and striae extending from valve face to mantle. 109. Low magnification valve view with distinct central nodule present. 110, 111. Central area demonstrating lack of an intermission and two elongate-elliptical stigma openings occluded by a dendritic structure. 112, 113. Apices with distinct helictoglossae offset from axial area. Siliceous granules are present around aveoli. Porelli area restricted to the mantle. Scale bars = 5 μm in Fig. 108; 10 μm in Fig. 109; 1 μm in Figs 110, 112; 0.5 μm in Figs 111, 113.