Nagumoea livingstonensis Van de Vijver & Kociolek, 2018

Vijver, Bart Van De & Kociolek, J. Patrick, 2018, A new species of Nagumoea (Bacillariophyta) from Antarctica, and a further consideration of the systematic position of the genus, Phytotaxa 349 (2), pp. 152-158 : 153-155

Nagumoea livingstonensis Van de Vijver & Kociolek sp. nov. ( Figs 1–9 )

Light Microscopy ( Figs 1–5 ): Frustules in girdle view rectangular, symmetrical in both apical and transapical axes. Valves linear to linear-lanceolate with weakly convex margins and non-protracted broadly rounded apices. Valve dimensions (n=10): length 7–13 μm, width 1.8–2.2 μm. Raphe in LM only very weakly detectable. Fibulae very distinct, visible in both valve and girdle view, 3–6 in 10 μm. Striae and areolae not discernible in LM. SEM ( Figs 6–9 ): Valve face slightly arched. Mantle relatively deep ( Fig. 8 ). Transapical striae on the valve face composed of one, relatively large, rounded areola, positioned very close to the axial area ( Fig. 7 ). Mantle striae composed of rarely one, usually two large, rounded areolae, located close to the valve face/mantle junction ( Fig. 8 ), ca. 40 in 10 μm. Mantle edge formed by a broad hyaline zone. Clear hyaline zone between valve face areolae and mantle areolae ( Figs 7, 8 ). External raphe branches straight, rather deep ( Fig. 8 ). Proximal raphe endings straight, weakly expanded, positioned very closely together ( Figs 7, 8 ). Terminal raphe fissures continuing onto the valve mantle, clearly unilaterally hooked ( Fig. 7 ). Internally, raphe simple with proximal endings terminating on a raised, narrow central nodule ( Fig. 6 ). Distal endings terminating onto small helictoglossae ( Fig. 9 ). Fibulae very robust, showing a complicated shape as typical for the genus Nagumoea ( Fig. 9 ). Fibulae usually broad, often even plate-like with a broad base near the valve margin and a concave near the middle ( Fig. 9 ). Siliceous elevations present connecting the lower parts of the fibulae ( Figs 6, 9 , arrows). Presence of a keel never observed.

Type:— Coastal pool near Shepherd’s Hill, Byers Peninsula, Livingston Island , South Shetland Islands , Maritime Antarctic Region , sample BY002, B. Van de Vijver, 9 January 2009 (62°40’11.4”S / 61°06’02.0”W) (holotype: BR! slide no. 4502; isotype: PLP! slide no. 336, University of Antwerp, Belgium). Figure 4 is of the holotype .

Etymology:—The specific epithet refers to Livingston Island where the new species is described from.

Ecology and associated diatom flora:— Nagumoea livingstonensis was so far only found in a sample taken from a relatively large coastal pool on the shore of Byers Peninsula. The pool had a pH of 7.27 and a conductivity of 247 μS/cm. Dominant taxa in the sample include Psammothidim papilio (D.E. Kellogg et al. 1980: 183) Van de Vijver & Kopalová (in Kopalová et al. 2012: 204), P. germainii (Manguin in Bourrelly & Manguin 1954: 20) Sabbe (in Sabbe et al. 2003: 242) and Mayamaea permitis ( Hustedt 1945: 919) K. Bruder & Medlin (2008: 327) .

Figures

FIGURES 1–9. Nagumoea livingstonensis sp. nov. LM and SEM pictures taken from the type locality (Byers Peninsula, Livingston Island, South Shetland Islands, Sample BY002). 1–4. LM pictures of valve views showing the fibular structure. Fig. 5. Entire frustule in girdle view. Fig. 6. SEM internal detail of the central area showing the typical fibular structure with the connecting siliceous ridges (see arrow) and the proximal raphe endings terminating on the central nodule. Fig. 7. SEM external view of an entire valve. Fig. 8. SEM external view of an entire valve, showing the valve face/mantle junction and the valve mantle. Fig. 9. SEM internal view of an entire valve. The arrows indicate the siliceous connections between the fibulae. Scale bar represents 10 μm for Figs 1–5 and 7, 1 μm for Fig. 6 and 5 μm for Figs 8 & 9.