Nitzschia papillosa Bertolli, Talgatti & Torgan, 2016

Bertolli, Lucielle M., Talgatti, Dávia M. & Torgan, Lezilda C., 2016, Nitzschia papillosa (Bacillariaceae, Bacillariophyta): a new species from a Brazilian salt marsh, Phytotaxa 247 (1), pp. 75-84 : 77

Nitzschia papillosa Bertolli, Talgatti & Torgan , sp. nov. ( Figs 2–40 )

LM: Valves lanceolate to linear-lanceolate, with cuneate apices, 17.6–57.4 μm long, 3.0–6.3 μm wide. Margins parallel with a slight constriction in the middle of the valve ( Figs 16–24 ), more pronounced in the larger specimens ( Figs 25–32 ), the smaller specimens tend to present more convex margins ( Figs 2–4 ). Striae parallel and equidistant (18–26 in 10 μm). Areolae indistinguishable. Keel eccentric, with fibulae clearly visible, somewhat irregularly distributed, denser at the ends (6–12 in 10 μm) than at the center (5–10 in 10 μm). Highly silicificated dots distributed almost equidistantly along the non-fibulate margin (9–16 in 10 μm), sometimes disposed in pairs ( Figs 8, 12, 14, 21, 30–33 ).

SEM: Few specimens were found in external valve view. The valves were frequently coated with a thin layer of silica, which undermined the images’ quality and hindered the observation of the details of N. papillosa ’s external morphology ( Fig. 33 ). The dots observed under LM are silica protuberances little rounded or squarer, which we refer as papillae, always situated on the transapical costae in the internal face ( Figs 34–40 ). Its distribution frequently follows a pattern; the costa with the papilla is preceded and followed by a costa without that structure ( Figs 34–36 ). In some cases, there are two or more consecutive costae with papillae and they may be very close and stick together forming a single siliceous bar ( Fig. 37 ). The striae are composed by a single row of rounded pores which may become double towards the fibulate margin ( Figs 38, 39 ). The fibulae start from one or two transapical costae and can become broader or conserve its width towards the valvar margin, assuming triangular or quadrangular shapes, respectively ( Figs 38–40 ). The two middle striae and fibulae are a little more distant than in the rest of the valve ( Fig. 34 ). There are usually one or two areolae after the line of silica thickenings ( Figs 38, 39 ), which may be joined, forming a single elongated pore ( Fig. 37 ). The small helictoglossae are visible at the valve poles ( Figs 39, 40 ).

Type: — BRAZIL. Rio Grande do Sul State: Rio Grande city, Ilha da Pólvora, 32º 01’14.42” S, 52º 05’ 59.09” W, 2 m a.s.l., epiphyton attached to Scirpus maritimus, D. Talgatti & L. Donadel , 18 February 2011. (holotype: HAS!, circled specimen on slide 6614, here illustrated as Fig. 8 . Isotype: UPCB!, circled specimen on slide 76087).

Etymology: —the epithet “ papillosa ” was designed because of the silica protuberances observed in the valve (papillae), which are the distinguishable feature of the species.

Figures

FIGURES 2–32. Morphological variation of Nitzschia papillosa sp. nov. in LM. 8. Holotype. Scale bar = 10 μm.

FIGURES 33–40. Nitzschia papillosa sp. nov. in SEM. 33. General external valve view. 34. General internal valve view. 35, 36. General internal valve view. 37. Detail of the papillae in the median region disposed alone, in pairs (white arrows) and sticking forming a single bar (black arrow). Note the pores joined after the line of papillae, forming a single elongate pore (black head arrow). 38. Detail of the papillae in the median region disposed alone, in pairs and in triplets (white arrows). Note that the striae’s single row of pores becomes double towards the fibulate margin (black arrow). 39, 40. Detail of the valve ends. Papillae disposed in pairs (white arrows) and double row of pores above the fibulae (black arrow). Note areolae after the line of silica excrescences (white head arrows) and the helictoglossae at the ends of the valvae (black head arrow). Scale bars: Fig. 33 = 2 μm, Figs 34–40 = 1μm.