Cymbopleura tumida Levkov, 2011

Levkov, Zlatko & Williams, David M., 2011, Fifteen new diatom (Bacillariophyta) species from Lake Ohrid, Macedonia, Phytotaxa 30, pp. 1-41 : 17-20

Cymbopleura tumida Levkov , sp. nov. ( Figs 115–121 , 126–130 )

Valvae leviter dorsiventrales, late ellipticae marginibus convexis, dorsali magis convexa, margine ventrali leviter convexa. Apices curte protracti et acute rotundati. Longitudo 42–56 µm, latitudo 22–27.5 µm. Area axialis modice angusta, ad aream centralem dilatata, area centralis angusta, asymmetrica vel lanceolata. Raphe lateralis ad aream centralem et ad apices sensim filiformis fissuris proximalibus bulbiformibus. Striae transapicales crasse punctatae, parallelae in media parte, 6–7/ 10 µm, radiatae ad apices 9–10 in 10 µm. Puncta striarum 22–24 in 10 µm.

Type:— MACEDONIA. Lake Ohrid, Bay of St. Naum, sand, small spring, collection date: 8 August 2006 (accession No. MKNDC 000693 ). Slide MKNDC 000693 (holotype). Slide BM 101474 (isotype) .

Valves slightly dorsiventral, broadly elliptical with convex margins, dorsal margin more strongly arched. Valve ends slightly protracted and acutely rounded. Valve length 42–56 µm, valve width 22.0– 27.5 µm. Axial area narrow, expanding into an asymmetrical or lanceolate central area. Raphe lateral, becoming filiform near poles. Central pores largely expanded. Striae radiate in middle, 6–7 in 10 µm, becoming strongly radiate at poles, 9–10 in 10 µm. Striae coarsely punctate with 22–24 areolae in 10 µm (LM).

Valve face flat, transition from valve face to valve mantle gradual ( Fig. 126 ). Markings (depressions) in central and axial area are absent ( Fig. 127 ). Raphe slightly lateral, proximally terminates in expanded teardrop-shaped central pores, while distally, the raphe fissures deflect towards dorsal valve side ( Figs 127, 128 ). Apical pore fields absent. Striae uniseriate, composed of round to elliptical areolae. Internally, areolae also with round openings. Internally, valve face flat ( Figs 129, 130 ). Interstriae wider than striae. Central nodule is elevated from valve ( Fig. 130 ). Raphe distally terminates with small helictoglossae. Intermissio is absent ( SEM).

Observations:— Cymbopleura tumida resembles C. budayana (Pantocsek) Krammer (2003: 19) (here as Figs 122–125 ) but can be differentiated by valve shape (broadly lanceolate in C. budayana ), width of axial and central areas (much wider in C. budayana ), areolae density (15–21 in 10 µm in C. budayana ), and absence of markings in the axial and central area. Cymbopleura juriljii Levkov & Metzeltin (in Levkov et al. 2007: figs 147: 1–4) (here as Fig. 114 ) has a similar valve outline to C. tumida but is longer (L= 100–120 µm) and wider (B= 34–40 µm). Cymbopleura cuspidata (Kützing) Krammer (2003: 8) has narrower valves (B= 14–17 µm) with densely spaced striae (S= 8–12 in 10 µm in the middle, becoming 12–15 in 10 µm at valve apices). Cymbopleura apiculata Krammer (2003 : fig 7: 8–10, fig 9: 1–6, fig 10: 1–4, fig 11: 1–3b) has comparable valve size and striae density but has a large central area which is distinctly set off and about ⅓ of valve width.

Family Gomphonemataceae Kützing (1844)

Genus Gomphosphenia Lange-Bertalot (1995)

Figures

FIGURES 114–125: LM micrographs. Fig. 114. Cymbopleura juriljii. Figs 115–121. Cymbopleura tumida. Figs 122– 125. Cymbopleura budayana. Scale bar = 10 µm.

FIGURES 126–130: SEM micrographs of Cymbopleura tumida. Fig. 126. External valve view. Fig. 127. Detail of midvalve showing central area, with teardrop–shaped central pores. Fig. 128. Detail of valve end, showing distal raphe fissure and uniseriate striae. Fig. 129. Internal valve view. Fig. 130. Detail of mid-valve showing central nodule. Scale bars in Figs 126, 129 = 20 µm; Figs 127, 128, 130 = 5 µm.