Pinnularia manausensis A.C. Pereira & Torgan, 2014

Pinnularia manausensis A.C. Pereira & Torgan sp. nov. ( Figs 2–6 View FIGURES 2–21 , 22–25 View FIGURES 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 View FIGURES 2–21 , row sample GoogleMaps ; isotypes HAS 109582 ! GoogleMaps ; BR 4319 ! GoogleMaps ).

Valves linear with slightly triundulate margins, middle inflated, subcapitate rounded ends ( Figs 2–6 View FIGURES 2–21 , 22 View FIGURES 22–25 ), 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 View FIGURES 22–25 ), terminal fissures sickle-shaped ( Fig. 23 View FIGURES 22–25 ). Terminal raphe endings curved towards secondary side of valves, while drop-like central pores deflect to primary side ( Figs 23, 24 View FIGURES 22–25 ). 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 View FIGURES 22–25 ).

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 View 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).