Pinnularia tupensis A.C. Pereira, Melo & Torgan sp. nov. (Figs 13–17, 26–32)

Type: — BRAZIL. Amazonas: Tupé Lake 03 o 02'35.4''S, 60 o 15'17.5''W, 23 September 2008, Pereira, A. C., sediment, station 3, (Holotype HAS slide n o 6494! holotype specimen = Figure 13, row sample HAS 109581 ; isotype BR 4321!).

Valves elliptic-lanceolate with strongly protracted capitate ends (Figs 13–17, 26, 30), valve length 52–64.2 µm, breadth 10.8–13 µm, length/breadth ratio is 4.75–4.93. Axial area narrow, widening towards the central area. Central area present, forming symmetric fascia. Raphe straight, filiform, proximal raphe endings slightly bent in same direction (Fig. 29), terminal fissures bayonet-shaped (Figs 31, 32). Terminal raphe endings curved towards secondary side of valves, while drop-like central pores deflect to primary side (Figs 29, 30). Internally, terminal fissures end in a prominent helictoglossa (Fig. 27). Striae (11–12 in 10 µm) radiate at middle, convergent at poles. Alveoli pattern with 3–6 rows of rounded areolae, each row with 12–13 areolae in 2 µm (Fig. 31).

Etymology: —Dedicated to study area Tupé Lake. Tupé means mat in the Tupy Guarany language.

Observations:— P. tupensis resembles in its outline P. brauniana (Grunow) Studnicka (1888: 737), P. rostratissima Hustedt (1965: 397) and P. rostratissima Hustedt var. ventricosa Metzeltin & Krammer in Metzeltin & Lange-Bertalot (1998: 186) but differs from these species mainly by the shape of the ends, area axial and striae pattern. P. rostratissima and P. rostratissima var. ventricosa have capitate rounded ends, wide axial area strongly expanded towards center of the valve and short striae. P. tupensis differs from P. brauniana by the valve breadth and shape of the poles (see table 2).

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1 Metzeltin & Lange-Bertalot (2007); 2 Patrick & Reimer (1966); 3 Metzeltin & Lange-Bertalot (1998); 4 Camburn & Charles (2000); 5 Hustedt (1965); 6 Studnicka (1888); 7 Smith (1856).

Pinnularia tupensis was observed in the sediment, and in the plankton, during the fall water with 6.40 m depth, 0.90 m transparency, high temperature (29.9ºC), low pH (4.5) and conductivity (7.60 µS.cm -1).