Nitzschia nienhuisii F.A.S. Sterrenburg & F.J.G. Sterrenburg

Lobban, Christopher S., 2015, Benthic marine diatom flora of Guam: new records, redescription of Psammodictyon pustulatum n. comb., n. stat., and three new species (Colliculoamphora gabgabensis, Lauderia excentrica, and Rhoiconeis pagoensis), Micronesica 2015 (2), pp. 1-49 : 10

Nitzschia nienhuisii F.A.S. Sterrenburg & F.J.G. Sterrenburg Figs 89–94

Ref. illus: Sterrenburg & Sterrenburg 1990, figs 2–4; Hein et al. 2008, pl. 59, figs 2, 3

Samples: GU7R; GU44AY-6; GU52P-1

Dimensions: Length 49–53 µm, width 16 µm; striae not resolved, even in SEM.

Diagnostics: Hyaline cells with protracted apices, the raphe raised on a keel, both branches curving to the same side.

Comments: This species is very similar to a hyaline Entomoneis in our flora, but is distinguished by the raphe branches curving to the same side, whereas those of Entomoneis are sigmoid (curve to opposite sides). The Entomoneis is also larger. When valves are acid cleaned the membranous valve collapses. There do not appear to be fibulae on the keel in the usual sense of them in Nitzschia , and Sterrenburg & Sterrenburg (1990) assigned this species to the genus with hesitation. There are markings on the keel, but these in SEM appear to be nothing more than wrinkles in the membranous valve material. The structure of this species is baffling but may be resolved with TEM.

Figures

Figures 87–97. Figs 87, 88. Nitzschia janischii whole mount, details of central nodule and apex (GU44Z-15) (SEM). Figs 89–94. Nitzschia nienhuisii. Figs 89, 90. Girdle and valve views of the same cell in a wet mount (DIC). Figs 91, 92. Girdle and valve views of frustules in permanent mounts (GU44R-1, GU52P-1) (phase contrast). Figs 93, 94. Whole mount in SEM, and detail of central raphe endings (GU7R). Figs 95–97. Petroneis humerosa (GU44I-3). Fig. 95. Valve (DIC). Fig. 96. External view of valve (SEM). Fig. 97. Internal detail (SEM). Scale bars: Figs 87–93, 95, 96 = 10 µm, Fig. 94 = 2 µm, Fig. 97 = 5 µm.