Anorthoneis vortex Sterrenburg 1987: 16

Pennesi, Chiara, Majewska, Roksana, Sterrenburg, Frithjof A. S., Totti, Cecilia & Stefano, Mario De, 2018, Taxonomic revision and morphological cladistics analysis of the diatom genus Anorthoneis (Cocconeidaceae), with description of Anorthoneis arthus-bertrandii sp. nov., Phytotaxa 336 (3), pp. 201-238 : 227

Anorthoneis vortex Sterrenburg 1987: 16 ( Figs 112–129 )

References:— Sterrenburg (1987), p. 15, 4 figs; Sterrenburg (1988), p. 375, pl. 1, figs 5, 7, pl.2, figs 8–15, pl. 5, figs 30–35; Hein (1991) figs 22–24, 25–28; Witkowski et al. (2000), pl. 42, figs 23–25.

Description. Valves broadly elliptical to almost circular in outline ( Figs 116 , 122 ). Apical axis: 14–16 μm, transapical axis: 11–12 μm.

SV:— Externally, valve face flat, becoming convex near the undifferentiated wide mantle, which terminates in a reduced marginal area ( Figs 116, 117 ). The eccentric sternum, very narrow, not well discernible, not reaching the valve margin and lacking terminal areas ( Figs 116, 117 ). In the valve centre, corresponding with an asymmetrical, irregular hyaline area, reduced and imperforated areolae are present ( Figs 116 arrow, 118). Transapical striae radiate 20–22 in 10 μm, uniseriate on the entire valve surface and composed of small, circular areolae, 22–24 in 10 μm, externally occluded by hymenes with small, radially distributed perforations ( Fig. 118 ). Virgae not raised. On the valve margin, close to the end of each stria, a smaller imperforated areola is present ( Figs 117–119 arrow). Internally, sternum narrow, thickened, expanding into irregular hyaline central area, with slightly raised small central nodule ( Figs 120, 121 ). Virgae raised on both the valve face and the mantle ( Fig. 121 ).

RSV:— Externally, valve face flat to convex, with concave mantle ( Figs 122, 123 ). Raphe sternum asymmetric, developed entirely within the valve face ( Figs 122, 123 ). Proximal raphe endings expanded, pore-like, converge on a short, strongly asymmetric central area ( Figs 122, 123, 126 ). Distal raphe endings similar in shape to the central ones terminate in roundish terminal areas, distant from the valve margin ( Fig. 127 ). Striae radiate, 22–24 in 10 μm, uniseriate on the valve face, becoming biseriate on the mantle ( Figs 122, 127 ), composed of small circular areolae (22–24 in 10 μm) occluded by hymenes ultrastructurally similar to those in the SV. As in the SV, a smaller areola is present on the valve margin, close to the end of each biseriate stria ( Figs 127, 129 arrows). Internally, both the raphe-sternum and the central nodule thickened and prominent ( Fig. 125 ). Proximal raphe endings deflected in opposite directions and hooked ( Fig. 128 ). Distal ones terminate in reduced helictoglossae hardly reaching the hyaline terminal areas ( Fig. 129 ). Valvocopula open, with a smooth inner margin ( Figs 125, 129 ).

Figures

FIGURES 112–115. Historical report of Anorthoneis vortex by different authors, LM images. (112–114) A. vortex specimens from Sterrenburg (1987), slide BM 81500, Bergen aan Zee, The Netherlands; (115) A. vortex specimens from Witkowski et al. (2000). Scale bars: Figs 112–114 = 5 μm.

FIGURES 116–121. Anorthoneis vortex specimens from Sterrenburg (1987) cleaned material from Bergen aan Zee, The Netherlands. (116) External view of sternum valve with slightly visible eccentric sternum and imperforated areolae in the asymmetrical hyaline-like area (arrow); (117) Tilted external view (60°) of sternum valve showing the wide convex mantle; (118) Detail of the sternum valve areolae; (119) Internal view of the sternum valve mantle showing smaller poroids present at the end of each stria close to the valve margin (arrow); (120) Internal view of sternum valve; (121) Tilted internal view (60°) of sternum valve showing the thickening of sternum and eccentric central area. Scale bars: Figs 117, 120 = 5 μm; Figs 116, 121 = 2 μm; Figs 118, 119 = 1 μm.

FIGURES 122–129. Anorthoneis vortex specimens from Sterrenburg (1987) cleaned material from Bergen aan Zee, The Netherlands, SEM images. (122) External raphe-sternum valve with asymmetric raphe; (123) Tilted external view (60°) of raphe-sternum valve showing the concave mantle; (124) Internal view of raphe-sternum valve; (125) Tilted external view (60°) of raphe-sternum valve; (126) External coaxial, expanded, pore-like central raphe endings; (127) External expanded, pore-like distal raphe ending terminating in a roundish submarginal hyaline area. Smaller, non-hymenate poroid is present at the end of each biseriate stria close to the valve margin (arrow); (128) Internal, uncinated proximal raphe endings deflected in opposite directions converging on the central nodule; (129) Internal distal raphe ending terminating in a reduced helictoglossa close to the hyaline terminal area. Smaller, not-hymenate poroid is present at the end of each biseriate stria (Arrow). Scale bars: Figs 122, 124, 125 = 5 μm; Fig. 123 = 2 μm; Figs 126–129 = 1 μm.