Mastogloia binotata (Grunow) Cleve 1895

Pennesi, Chiara, Poulin, Michel, Hinz, Friedel, Romagnoli, Tiziana, Stefano, Mario De & Totti, Cecilia, 2013, Comparison of two new species of Mastogloia (Bacillariophyceae) with other small members of section Ellipticae, Phytotaxa 126 (1), pp. 1-21 : 3

Mastogloia binotata (Grunow) Cleve 1895 ( Figs 1–8 )

Basionym: — Cocconeis binotata Grunow 1863, p. 145 , pl. 4 (13), fig. 13a.

Synonym:— Cocconeis binotata var. stauroneiformis Grunow 1863, p. 145 , pl. 4 (13), fig. 13b. Orthoneis binotata (Grunow) Grunow 1867, p. 15 .

References:— Van Heurck 1880 –1885, pl. 28, fig. 7, as Orthoneis binotata ; Van Heurck 1896, p. 284, pl. 29, fig. 815, as Orthoneis binotata ; Peragallo & Peragallo 1897 –1908, p. 27, pl. 5, fig. 2, as Orthoneis binotata ; Hustedt 1933, p. 470, fig. 889; Hendey 1964, p. 238, pl. 37, fig. 11; Cholnoky 1968, p. 41, fig. 38; Ricard 1973, p. 163, pl. 1, fig. 7; 1975, p. 51, pl. 2, figs 9–11; Stephens & Gibson 1979a, p. 500, figs 2–9; 1979b, fig. 4; Navarro 1983, p. 120, figs 18, 19; Kociolek et al. 1987, figs 1–23; Paddock & Kemp 1990, figs 112, 132; Hein et al. 1993, figs 12, 13; 2008, p. 60, pl. 34, fig. 7; John 1994, p. 192, fig. 18; Witkowski et al. 2000, p. 240, pl. 75, figs 15–18.

Material:— Sample from Calabria, Italy. SEM stub no. DISVAR-ANC59SP43.

SEM morphology:— Externally, the raphe-sternum is slightly transapically dilated at centre into a very thin lanceolate fascia that does not reach the valve margins ( Figs 1, 2, 7 ). The raphe consists externally of two straight branches ending centrally and distally in apically expanded pores ( Figs 1–3, 7 ). Internally, the straight raphe branches are bordered by ribs, which are slightly raised only at the central nodule and the helictoglossae at the poles ( Figs 4, 5 ). The transapical striae (14–18 in 10 µm) are uniseriate and vary from parallel at centre to curved and radiate at poles, and they are crossed by a more or less quincunx pattern which is more evident near the apex ( Figs 1, 7 ). The areolae forming the striae are both externally and internally circular, sunken onto the valve surface and occluded by vela with rotae, decreasing in size at the valve–mantle junction ( Figs 1–5, 7, 8 ). There is only one large, rectangular and central partectum (1.9–2.8 µm in width) ( Fig. 4 , arrowhead) attached to each side of the valvocopula with a flange consisting in a series of very short costae and biseriate striae ( Figs 4, 6 , arrowhead). The partecta are ornamented on its surface with uni- to triseriate rows of small pores. Each partectum opens externally in the middle of the valvocopula through a large and elongate partectal pore ( Fig. 7 , arrowhead), while beyond one row of small pores is present. Length: 19.6– 27.3 µm; width: 11.4–16.4 µm ( Table 1).

Figures

FIGURES 1–8. Mastogloia binotata, SEM (DISVAR-ANC59SP43, Calabria, Italy). (1) External view of valve with straight raphe branches; (2) External view of the central region showing raphe endings and thin fascia; (3) External view of apex showing distal raphe ending with no terminal fissure; (4) Internal valve view showing one large, rectangular and central partectum (arrowhead) on each side of the valvocopula; (5) Internal valve view showing raised central nodule; (6) Internal view of valve margin showing flange (arrowhead) attaching the partectum to the valvocopula; (7) Oblique view of tilted specimen showing partectal pore (arrowhead) on open valvocopula; (8) External view showing sunken rounded areolae on the valve face covered by vela with rotae.