Hantzschia amphioxys (Ehrenberg) Grunow, 1880

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 : 173-176

Hantzschia amphioxys (Ehrenberg) Grunow ( Figs 35–50 )

LM ( Figs 35–46 ):—Valves dorsiventral with a slightly convex to almost straight dorsal margin. Ventral margin weakly concave in the middle becoming straight near the apices.Apices abruptly protracted, shortly elongated, clearly capitate, almost straight to slightly deflected towards the dorsal side. Valve dimensions (n=25): length 34–52 μm, width is 5.0–6.0 μm. Fibulae 6–9 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 near the apices, 24–25 in 10 μm. Areolae not discernible in LM. SEM ( Figs 47–50 ): Valves on the ventral side bordered by a narrow, clearly thickened hyaline keel ( Fig. 47 ). Striae located in shallow individual depressions bordered by slightly raised costae ( Fig. 48 ). External areola openings rounded occluded by individual hymenes ( Fig. 48 ). External proximal raphe branches deflected, clearly interrupted near the valve middle ( Fig. 48 ). Internally, fibulae clearly not equidistant ( Fig. 50 ). Internal proximal raphe endings interrupted, one end being deflected and the other more or less straight ( Fig. 49 ). Striae forming narrow, deep, parallel grooves ( Fig. 50 ). Areolae separated by thin struts ( Fig. 49 , arrows).

Ecology:—So far, the species was only with certainty confirmed from the moss vegetation collected in a small pool on James Ross Island. Detailed analysis of the stria structure and the internal raphe endings is necessary to avoid confusion with H. amphioxys f. muelleri .

Figures

FIGURES 35–50. Hantzschia amphioxys. LM and SEM observations of a population from James Ross Island (sample Anna Pool). Figs 35–46. Light micrographs showing a reduction in valve length. Fig. 47. External view of an entire valve showing the irregular, narrow ventral hyaline border. Fig. 48. External detail of the central area with the deflected, interrupted proximal raphe endings. Fig. 49. Internal detail of the central area with the interrupted, deflected proximal raphe endings. The arrows indicate the small silica bars separating the areolae. Fig. 50. Internal view of an entire valve showing the irregularly placed fibulae. Scale bar represents 10 μm except for figs 48 & 49 where scale bar = 1 μm.