Hantzschia amphioxys (Ehrenberg) Grunow f. muelleri Ko-Bayashi

Bulínová, Marie, Kochman-Kędziora, Natalia, Kopalová, Kateřina & Vijver, Bart Van De, 2018, Three new Hantzschia species (Bacillariophyta) from the Maritime Antarctic Region, Phytotaxa 371 (3), pp. 168-184 : 176

Hantzschia amphioxys (Ehrenberg) Grunow f. muelleri Ko-Bayashi ( Figs 51–65 )

LM ( Figs 51–61 ):—Valves dorsiventral with a slightly convex to almost straight dorsal margin. Ventral margin weakly concave in the middle becoming slightly convex near the apices. Apices abruptly protracted, elongated and clearly capitate, slightly deflected towards the dorsal side. Valve dimensions (n=25): length 40–55 μm, width 5.0–6.0 μm. Fibulae 6–7 in 10 μm, unequally spaced, the middle two fibulae clearly more distant. Each fibula connected to 1–3 transapical costae. Striae equidistant, weakly radiate in the middle becoming more parallel and even convergent near the apices, 22–26 in 10 μm. Occasionally, middle striae slightly more spaced than the others. Areolae not discernible in LM. SEM ( Figs 62–65 ): Valves on the ventral side bordered by a clearly thickened keel covered with irregularly scattered areolae ( Fig. 62 ). Striae located in rather deep grooves bordered by raised costae ( Figs 62, 63 ), more prominently deepened near the ventral margins ( Fig. 63 ). External areola openings rounded occluded by individual hymenes ( Fig. 63 ). External proximal raphe branches deflected, clearly interrupted near the valve middle ( Fig. 63 ). Internally, fibulae clearly not equidistant ( Fig. 65 ). Internal proximal raphe endings unclear, interrupted by a thickened central nodule ( Fig. 64 ). Striae forming narrow, deep, parallel grooves ( Fig. 64 ).

Ecology:— Hantzschia amphioxys f. muelleri is a very commonly reported species, often observed in terrestrial habitats such as seepage areas, wet moss vegetations and soils (Kellogg & Kellogg 2002 and references therein). The ecological separation from H. amphioxys is unclear. All populations will need further morphological research to determine their exact ecological preferences.

Figures

FIGURES 51–65. Hantzschia amphioxys f. muelleri. LM and SEM observations of a population from Livingston Island (sample LIV- 16A). Figs 51–61. Light micrographs showing a reduction in valve length. Fig. 62. External view of an entire valve showing the thickened ventral hyaline border with scattered areolae. Fig. 63. External detail of the central area with the deflected, interrupted proximal raphe endings. Fig. 64. Internal detail of the central area with the thickened central nodule. Proximal raphe endings are not clearly discernible. Fig. 65. Internal view of an entire valve showing the irregularly placed fibulae. Scale bar represents 10 μm except for figs 63 & 64 where scale bar = 1 μm.