Pinnularia manausensis A.C. Pereira & Torgan, 2014

Pereira, Andreia Cavalcante, Torgan, Lezilda Carvalho & Melo, Sérgio, 2014, Four new Pinnularia Ehrenberg (Bacillariophyta, Pinnulariaceae) species from Amazonian black water (Tupé Lake, Amazonas State, Brazil), Phytotaxa 158 (2), pp. 154-168 : 159-161

Pinnularia manausensis A.C. Pereira & Torgan sp. nov. ( Figs 2–6 , 22–25 )

Type: — BRAZIL. Amazonas: Tupé Lake 03 o 02'17,1''S, 60 o 15'45,3''W, 16 December 2003, Melo S., plankton, station 9, ( Holotype HAS slide n o 6492 !, holotype = Figure 2 , row sample ; isotypes HAS 109582 ! ; BR 4319 ! ).

Valves linear with slightly triundulate margins, middle inflated, subcapitate rounded ends ( Figs 2–6 , 22 ), valve length 121–130.2 µm, breadth 15.5–18.5 µm, length/breadth ratio 7.0–7.8. Axial area 1/3 width of valve, widening near central area. Central area present, generally forming symmetric fascia. Raphe lateral, proximal raphe endings bent in same direction ( Fig. 24 ), terminal fissures sickle-shaped ( Fig. 23 ). Terminal raphe endings curved towards secondary side of valves, while drop-like central pores deflect to primary side ( Figs 23, 24 ). Striae ( 10–11 in 10 µm) radiate at middle, convergent at ends. Alveoli pattern with 3–7 rows of rounded areolae, each row with 12–13 areolae in 2 µm ( Fig. 25 ).

Etymology:— Dedicated to Manaus city, Amazonas State.

Observations:— P. monicae Metzeltin & Lange-Bertalot (2007: 211) exhibits some similarities to P. manausensis but differs by its valve outline and axial area shape (lanceolate), which is not linear as it is in P. manausensis . Furthermore, P. monicae has broadly rounded poles and a lower density of striae ( Table 2 ).

Pinnularia manausensis was observed in the plankton, during low waters, which showed 0.30 m depth, 0.30 m transparency, high temperature (28.6ºC), low pH (4.7) and conductivity (7.10 µS.cm -1).

Figures

FIGURES 2–21. LM valve views. Figs 2–6. P. manausensis sp. nov. Figs 7–12. P. nelsonii sp. nov. Figs 13–17. P. tupensis sp. nov. Figs 18–21. P.walkerae sp. nov. Scale bar = 10 µm.

FIGURES 22–25. SEM: Pinnularia manausensis sp. nov. External view of morphological features. Fig. 22. General view of valve. Fig. 23. Detail of the sickle-shaped raphe fissure at pole. Fig. 24. Central area showing proximal raphe fissures bent in same direction. Fig. 25. Alveolus with rows of rounded areolae. Scale bars: Fig. 22 = 10 µm; Figs 23, 24 = 5 µm; Fig. 25 = 2 µm.