Anorthoneis hyalina Hustedt 1955: 15

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 : 219-221

Anorthoneis hyalina Hustedt 1955: 15 ( Figs 68–87 )

References:— Hustedt (1955), pl. 2 figs 3–4, pl. 5 figs 12–13; Foged (1975), pl. 7, figs 12, 13; Simonsen (1987), p. 404, pl. 604, figs 1–8; Witkowski et al. (2000), p. 98, pl. 51, fig. 1; Garcia & Talgatti (2006), figs 3–4, 9–15.

Description. Valves ovoid to circular in outline ( Figs 76 , 81 ). Apical axis: 24–36 μm, transapical axis: 20–28μm.

SV:— Externally, valve face flat in its central part, distally convex, curving gradually into a shallow undifferentiated mantle ( Figs 76, 78 ). Sternum strongly asymmetric, expanded in the centre, giving rise to a very large, semi-circular central area, occupying more than 2/3 of the entire valve surface ( Figs 76, 78 ), covered with randomly scattered, irregular concavities and flanked by groove-like fissures ( Figs 78, 79 arrow). Similar irregular, apically elongated groove-like fissures mark the apical axis ( Figs 76, 78 ). Striae uniseriate, radiate, 9–11 in 10 μm close to the valve centre, becoming denser towards the margin (15–17 in 10 μm), composed of slit-like areolae (10 in 10 μm) internally occluded by vela ( Fig. 80 ). The internal areola openings are larger than those on the exterior. Internally, almost undiscernible sternum and very large hyaline central area appear heavily silicified and smooth ( Fig. 77 ).

RSV:— Externally, valve face concave with slightly raised asymmetrical raphe-sternum ( Figs 81, 84 ). Valve mantle wide, terminating at the valve margin in a narrow marginal area bordered by a thickened rim; same thickening occurs on valvocopula ( Figs 82, 85 arrows); ligulate structures are visible on the valvocopula ( Fig. 85 , black arrow). Striae radiate and strongly radiate near the apices ( Figs 81, 82 ), 17–18 in 10 μm, uniseriate, becoming biseriate on the mantle ( Figs 82, 85, 87 ). Circular areolae almost equal in size, 30 in 10 μm, occluded by perforated hymenes. A smaller, nonhymenate areola is present on the valve margin, at the end of each stria ( Fig. 85 , white arrowhead). Asymmetric central area small, subtriangular ( Figs 81, 83 ). Raphe branches straight with close, coaxial, and slightly expanded proximal endings, deflected slightly to one side ( Figs 81, 83 ). Distal raphe endings straight, slightly expanded, hardly reaching sub-circular terminal areas, distant from the valve margin ( Fig. 82 ). Internally, both the raphe-sternum and the central nodule thickened and prominent ( Fig. 86 ). Distal ones end in reduced helictoglossae, not reaching the hyaline terminal areas ( Fig. 86 ).

Figures

FIGURES 68–75. Historical reports of Anorthoneis hyalina by different authors. (68) Raphe-sternum and sternum valve drawings of A. hyalina from Hustedt (1955) (holotype); (69) Sternum valve micrographs of A. hyalina from Witkowski et al. (2000); (70) Micrograph of A. hyalina specimen H65236 from slide ZT1/91 (isolectotype), material AM792 from Beaufort, North Carolina, USA (Hustedt Diatom Collection, Bremerhaven, Germany); (71) Micrograph of A. hyalina specimen H65075 from slide ZT1/84 (isolectotype) material AM791 from Beaufort, North Carolina, USA (Hustedt Diatom Collection, Bremerhaven, Germany); (72) Micrograph of A. hyalina specimen H64958 from slide ZT1/79 (lectotype), material AM791 from Beaufort, North Carolina, USA (Hustedt Diatom Collection, Bremerhaven, Germany); (73) Micrograph of A. hyalina specimen H65365a from slide ZT2/01(Paralectotypes), cleaned material AM794 from Beaufort, North Carolina, USA (Hustedt Diatom Collection, Bremerhaven, Germany); (74) Micrograph of A. hyalina specimen H65159 from slide ZT1/87 (isolectotype), cleaned material AM791 from Beaufort, North Carolina, USA (Hustedt Diatom Collection, Bremerhaven, Germany); (75) A. hyalina specimen from cleaned material AM791, Beaufort, North Carolina, USA (Hustedt Diatom Collection, Bremerhaven, Germany). Magnification: Fig. 69: x1500. Scale bars: Figs 70–75 = 10 μm.

FIGURES 76–80. Anorthoneis hyalina specimens from Hustedt’s cleaned material AM791, AM794, Beaufort, North Carolina, USA (Hustedt Diatom Collection, Bremerhaven, Germany), SEM images. (76) External view of sternum valve showing the asymmetrical hyaline central area; (77) Internal view of sternum valve with thickened hyaline central area; (78) Tilted external view (60°) of sternum valve; (79) Detail of sternum valve surface showing imperforated areolae (arrow); (80) Detail of sternum valve mantle in internal view showing the slit-like areolae occluded by vela. Scale bars: Figs 76, 77 = 10 μm; Fig. 78 = 5 μm; Figs 79, 80 = 2 μm.

FIGURES 81–87. Anorthoneis hyalina specimens from Hustedt’s cleaned material AM791, AM794, Beaufort, North Carolina, USA (Hustedt Diatom Collection, Bremerhaven, Germany), SEM images. (81) Raphe-sternum valve in external view; (82) External view of the apically elongated distal raphe ending terminating in a hyaline submarginal area; (83) Detail of coaxial proximal raphe endings in external view; (84) Tilted external view (60°) of raphe-sternum valve; (85) Tilted external view (60°) of raphe-sternum mantle terminating in narrow submarginal area bordered by a thickened rim (arrows). Smaller non-hymenate poroids are present at the end of each biseriate stria (white arrowhead) and ligulate structures are visible on the marginal area (black arrowhead); (86) Raphe-sternum valve in internal view; (87) Detail of the internal surface of raphe-sternum valve showing the biseriate mantle striae. Scale bars: Figs 81, 84, 86 = 10 μm; Fig. 87 = 2 μm; Figs 82, 83, 85 = 1 μm.