Fragilaria tenera (Smith) Lange-Bertalot, 1980

Almeida, Pryscilla D., Morales, Eduardo A., Wetzel, Carlos E., Ector, Luc & Bicudo, Denise C., 2016, Two new diatoms in the genus Fragilaria Lyngbye (Fragilariophyceae) from tropical reservoirs in Brazil and comparison with type material of F. tenera, Phytotaxa 246 (3), pp. 163-183 : 168-170

Fragilaria tenera (Smith) Lange-Bertalot ( Figs 2–22 )

Basionym: Synedra tenera Smith (1856: 98) .

No illustrations accompanied the protologue of S. tenera Smith. Lange-Bertalot (1980) made the transfer of species to the genus Fragilaria and, more recently, the type material of S. tenera was lectotypified by Krammer & Lange-Bertalot (1991, pl. 115, figs 1–2). New photos from lectotype slide were provided and illustrated in Lange-Bertalot & Ulrich (2014).

The latter authors treated three varieties F. tenera var. tenera , F. tenera var. nanana ( Lange-Bertalot 1993: 48) Lange-Bertalot & Ulrich (2014: 7) and F. tenera var. lemanensis Druart et al. (2007: 284) . Due to its widespread occurrence F. tenera sensu lato has been considered as a complex by several authors in the past (e. g. Hustedt 1930, Cleve-Euler 1953, Patrick & Reimer 1966), but the complete description was given by Lange-Bertalot & Ulrich (2014). The results presented here expand the current knowledge about this complex.

Type material analysis:— Specimens of F. tenera were abundant in the lectotype material from Collection Smith VI 46 C8, housed in the Botanic Garden Meise ( BR!) and were suitable for LM and SEM imaging. Frustules slightly arched in girdle view ( Figs 2, 3 ). Valves linear-lanceolate with slightly convex margins ( Figs 5–7 , 14 ). Apices subcapitate ( Figs 4–15 ). Central area difficult to observe, sometimes inflated ( Figs 4, 9, 10 ), and marked by ghost striae ( Figs 12, 14, 17 ). In internal view, the central area is expanded bilaterally ( Figs 13, 20 ). Sternum linear, conspicuous ( Figs 5, 10, 11 ). Striae alternate, visible, with indistinct areolae ( Figs 5–8 ). Pyramidal spines located throughout entire margin at junction between valve face/mantle ( Figs 7–9 ). Spines (3–4) present also at poles ( Figs 15, 16 ). Striae composed of 2–3 areolae on valve face and 2–3 areolae on mantle ( Figs 15–22 ). Areolae rounded, covered with rotae ( Figs 15–17 ). Apical pore fields of the ocellulimbus type with 3–5 rows of poroids ( Figs 16, 19 ). Plaques present on abvalvar margin of mantle ( Figs 21, 22 ). One small rimoportula present at one of the valve ends ( Figs 16, 18 ). Length: 68.1–114.4 μm, width: 1.9–2.1 μm, stria density 18–20 in 10 μm (n = 12).

bar = 2 μm in Figs 15, 16, 18, 19, 22 .

Figures

FIGURES 2–11. LM. Fragilaria tenera (Smith) Lange-Bertalot. LM pictures taken from the isotype population (BR-4434) of Synedra tenera Smith. 2, 3. Frustules in girdle view. 4–11. Population showing variation in size and valve outline. Scale bar = 10 μm.

FIGURES 12–22. SEM. Fragilaria tenera (Smith) Lange-Bertalot. SEM images taken from the type material (BR-4434). 12, 14. Valves in external view. 13. Valve in internal view. 15, 16. External view of apices. 16. Apex showing rimoportulae. 17. Central area in external view showing pyramidal spines. 18, 19. Apices in internal view. 18. Apex showing rimoportulae in internal view. 20. Central area in internal view. 21, 22. Mantle with plaques on abvalvar margin. Scale bar = 40 μm in Figs 12–14. Scale bar = 3 μm in Figs 17, 20, 21. Scale