Hantzschia australabundans, Bulínová & Kochman-Kędziora & Kopalová & Vijver, 2018

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 : 170

Hantzschia australabundans sp. nov. ( Figs 1–10 )

Synonym:— Hantzschia abundans sensu Zidarova et al. (2010, p. 322 , Fig. 2 ) non sensu Lange-Bertalot (1993, p. 75, Fig. 85 : 12–17)

LM ( Figs 1–6 ): Valves clearly dorsiventral with a convex ventral side, occasionally flattened in the middle. Dorsal side distinctly concave in the middle but convex towards the apices. Valve apices clearly protracted, rostrate to sub-capitate in large valves, almost capitate in smaller valves. Valve dimensions (n=30): length 48–101 μm, 7.5–12.0 μm. Fibulae, 5–7 in 10 μm, with the median two clearly distant. Each fibula connected to 1–3 transapical costae. Striae radiate in the valve middle, parallel to slightly curved near the apices, equidistant 17–23 in 10 μm. Areolae not discernible in LM. SEM ( Figs 7–10 ): Valves showing a narrow hyaline, weakly thickened ventral margin ( Fig. 7 ). Striae uniseriate, composed of small, rounded areolae externally covered by individual hymenes ( Figs 9, 10 ), ca. 45 in 10 μm. Striae never situated in deep grooves ( Fig. 8 ). Externally, the central raphe endings weakly deflected to almost straight, clearly interrupted near the middle ( Fig. 8 ). Internally, proximal raphe endings close together, straight, terminating on a thickened central nodule ( Fig. 10 ). Internally, fibulae clearly unevenly distributed, connected to 1–4 transapical costae ( Fig. 9 ). Transapical striae located in deep grooves ( Figs 9, 10 ).

Type:– SOUTH SHETLAND ISLANDS, Livingston Island, sample LIV-BY16A (62°38’10.8”S / 61°6’27.4”W), leg. M. Toro, coll. date 16 December 2006 (holotype, slide BR 4512 ; isotype, slide PLP –342, University of Antwerp , Belgium) .

Ecology:— Hantzschia australabundans was found in several soil and moss samples on the South Shetland Islands. The largest population was found in sample LIV-BY16A, taken from a biofilm in an area flooded by freshwater between stones on Byers Peninsula close to the main plateau. The sample is dominated by various Luticola , Hantzschia , Pinnularia and Humidophila taxa. Due to confusion with H. abundans , the exact distribution and ecology of this species is not entirely known.

Figures

FIGURES 1–6. Hantzschia australabundans. Light micrographs (LM) of the type population (Livingston Island, Byers Peninsula, sample LIV-BY16A). Scale bar represents 10 μm.

FIGURES 7–10. Hantzschia australabundans. Scanning electron micrographs (SEM) of the type population (Livingston Island, Byers Peninsula, sample LIV-BY16A). Fig. 7. External view of an entire valve showing the ventral hyaline border. Fig. 8. External detail of the central area with the interrupted proximal raphe endings and the shallow areolae. Fig. 9. Internal view of an entire valve showing the irregularly placed fibulae. Fig. 10. Internal detail of the central area with the interrupted proximal raphe endings located on a heavily silicified central nodule. Scale bar represents 10 μm except for figs 9 & 11 where scale bar = 1 μm.

FIGURES 77–89. Hantzschia incognita. LM and SEM observations of the type population (Livingston Island, Hurd Peninsula, sample Π1a). Figs 77–85. Light micrographs showing a rather limited morphological variability. Fig. 86. External view of an entire valve showing the thickened ventral hyaline border and the grooves with the striae. Fig. 87. External detail of the central area with the continuous proximal raphe endings and the deep stria grooves. Fig. 88. Internal detail of the central area with the continuous proximal raphe endings. Fig. 89. Internal view of an entire valve showing the irregularly placed fibulae. Scale bar represents 10 μm except for figs 87 & 88 where scale bar = 1 μm.