Gomphonema prowsei Glushchenko, Kulikovskiy & Kociolek, 2017

Glushchenko, Anton, Kulikovskiy, Maxim & Kociolek, John Patrick, 2017, New diatom species from the Gomphonema subtile group in Southeast Asia, Phytotaxa 329 (3), pp. 223-232 : 229-230

Gomphonema prowsei Glushchenko, Kulikovskiy & Kociolek sp. nov. ( Figs 64–83 )

Description.

LM. Valves lanceolate-clavate with headpole protracted, expanded and capitate and footpole rounded and sometimes subcapitate. Length 50–60 μm, breadth 8–9 μm. Axial area narrowly lanceolate, central area barely distinguished and possessing a single, enlarged stigma positioned at the end of a central stria. Raphe more or less lateral, slightly undulate, with external proximal ends dilated slightly and distal ends deflected onto the valve mantle. Striae parallel to radiate, 11–15 in 10 μm, slightly coarser at the center of the valve; 6–7 areolae in stria.

SEM. The valve exterior has areolae occluded by flaps, giving the openings the appearance of being c-shaped ( Figs 76, 78, 80, 82 ). The center of the valve has dilated proximal raphe ends and enlarged, round stigmal opening ( Fig. 80 ). At the headpole, the distal raphe end is deflected onto the mantle ( Fig. 78 ). At the footpole, the apical pore field (APF) is positioned on the valve mantle ( Fig. 82 ). Internally, there is a small central nodule bearing recurved proximal raphe ends and a slit-like stigma opening ( Figs 77, 81 ). Helictoglossae are offset from the raphe branch, and septa and small pseudosepta are evident at both apices ( Figs 79, 83 ). At the footpole, porelli of the APF are occluded ( Fig. 83 ).

Type: — VIETNAM. Đồng Nai Province, Cát Tiên National Park, Tà Lài Reservoir, N11°23.260’ E107°21.490’. 05.10.2015, E.S. Gusev & M.S. Kulikovskiy, 5 th October 2015, (collection of Maxim Kulikovskiy, I.D. Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences ( IBIW), holotype here designated, slide no 03496 = Fig.66 ).

Differential diagnosis. Species differs from G. pseudosubtile Reichardt by the capitate and enlarged apex at the headpole, finer stria density (11–15 in 10 μm, not 10–12 in 10 μm in G. pseudosubtile ), as well as having a more narrow central area.

Etymology. This species is dedicated to the British ichthyologist and phycologist G.A. Prowse (1916–1977), who studied algae, fungi and lichens from Malaysia and Singapore.

Distribution. Malaysia ( Prowse 1962: pl. XVI, Figs b, j–l), Papua New Guinea ( Vyverman 1991: pl. 53, Fig. 5 ), Japan ( Shiono & Jordan 1995: pl. 10, Fig. 4 ). Species found in our samples 02400 and 03496.

( Figs 76, 77 ); 1 μm ( Figs 78 – 83 ).

Figures

FIGURES 64–75: Gomphonema prowsei Glushchenko, Kulikovskiy & Kociolek sp. nov. LM. Size diminution series, valve views. Figure 66 is of the holotype.

FIGURES 76–83: Gomphonema prowsei Glushchenko, Kulikovskiy & Kociolek sp. nov. SEM. Figs 76, 78, 80, 82 are external views; 77, 79, 81, 83 are internal views. Fig. 76. Whole valve illustrating valve shape, with characteristic headpole and footpole. Fig. 77. Whole valve with distinctly punctate striae evident. Fig. 78. Headpole, with the hooked-shaped distal raphe end curving onto the valve mantle. C- and E-shaped areolar openings are evident. Fig. 79. Headpole, showing prominent helictoglossa, septum and pseudoseptum. Helictoglossa is offset to one side. Fig. 80. Valve center with slightly dilated proximal raphe ends, round stigma opening and areolae occluded by flaps that create C- or irregularly-shaped openings. Fig. 81. Valve center with small central nodule bearing recurved proximal raphe ends and slit-like stigma opening. Striae are in troughs, with thickened rims around each areola. Fig. 82. Footpole, with round porelli positioned mostly on the valve mantle, physically separated, and morphologically distinct from the areolae. Fig. 83. Footpole, with large helictoglossa and pseudoseptum evident. Porelli are occluded internally. Small siliceous projections can be seen around the areolae. Scale bars = 10 μm

FIGURES 1–25: Gomphonema pantropicum Reichardt. LM. Size diminution series, valve views. Scale bar = 10 μm.