Stauroneis schinzii var. argentina Frenguelli 1933

Vouilloud, A. A., Guerrero, J. M., Palladino, M. B. & Lamaro, A. A., 2021, Revision Of The Type Materials Of Stauroneis Schinzii Var. Argentina Frenguelli And S. Schinzii Var. Maxima Frenguelli (Bacillariophyceae), Phytotaxa 478 (1), pp. 119-130 : 121-122

Stauroneis schinzii var. argentina Frenguelli 1933 (384, Pl. 1, fig. 10) ( Figs 2–21 )

Original description (as Stauroneis schinzi var. argentina ): Fig. 2

Difiere del tipo de Brun (Espèces Nouvelles, pág. 38, pl. 16, fig. 1) por los extremos valvares leve, pero claramente atenuados, y por sus estrías menos numerosas. En todo lo demás corresponde a la especie, sobre todo si tenemos presente la figura de Heiden en A. Schmidt, Atlas, pl. 242, fig. 9. Valva: largo 0,165 a 0,182, ancho 0,019 a 0,020. La especie tipo corresponde a los lagos de la región tropical de África S-W, según Brun y Cleve; pero, ha sido indicada como viviente también en Santos, Brasil (Zimmermann) y fósil en Montgomery, Alabama (Heiden). Una variedad, var. nyassensis , según O. Müller, vive en aguas estancadas de África tropical (pantano de Puerto Wied, cerca de Nyassa).

Here translated: “It differs from Brun’s type (Espèces Nouvelles, p. 38, pl. 16, fig. 1) by the slightly but clearly attenuated valve ends, and by the less numerous striae. In everything else it fits in the species, mainly considering Heiden’s figure in A. Schmidt, Atlas, pl. 242, fig. 9. Valve: length 0.165 to 0.182 [mm], width 0.019 a 0.020 [mm]. According to Brun and Cleve, the type species has been found in tropical lakes of SW Africa; but it has also been reported as extant in Santos , Brazil ( Zimmermann ) and as fossil in Montgomery , Alabama ( Heiden ). According to O. Müller, var. nyassensis lives in stagnant waters in tropical Africa (swamp in Port Wied, near Nyassa)” .

Frenguelli recorded S. schinzii var. argentina as frequent in Series 260 and rare in Series 261. Our LM examination of the slides yielded 39 specimens of this variety in Series 260 and no specimens in Series 261. During SEM examination of Series 260 we found only 3 broken valves, one in external view and two in internal view.

Figures

FIGURES 2–16. Stauroneis schinzii var. argentina Frenguelli. Fig. 2. Original drawing of Frenguelli (1933, Pl. I, fig. 10). Figs 3–16. LM. Specimens from type population. Figs 5–6. Lectotype, same specimen in different focus. Fig.15. Detail of valve end showing distal raphe fissure. Fig. 16. Detail of valve centre showing sternum and proximal raphe ends. Note the irregularly long striae delimiting the axial area (arrow). Scale bars: 10 µm (Figs 2–14); 5 µm (Figs 15–16).

FIGURES 17–21. Stauroneis schinzii var. argentina Frenguelli. Specimens from type population. SEM. Fig. 17. Broken valve in external view. Fig.18. Broken valve in internal view. Fig. 19. Detail of external valve end showing distal raphe fissure. Note one row of poroids on each girdle band (arrows). Fig. 20. Detail of external valve face; note the transapical elongated areolae. Fig. 21. Detail of internal valve center showing proximal raphe ends. Scale bars: 10 µm (Figs 17–18); 2 µm (Figs 19–21).