Sellaphora antarctica Zidarova, Kopalová & Van de Vijver, 2016

Zidarova, Ralitsa, Kopalová, Kateřina & Vijver, Bart Van De, 2016, Ten new Bacillariophyta species from James Ross Island and the South Shetland Islands (Maritime Antarctic Region), Phytotaxa 272 (1), pp. 37-62 : 50-51

Sellaphora antarctica Zidarova, Kopalová & Van de Vijver , sp. nov. ( Figs 136–156 )

LM observations ( Figs 136–153 ): Frustules in girdle view rectangular ( Figs 152, 153 ). Valves linear-elliptic with weakly convex to almost parallel (largest specimens) margins. Valve apices not protracted, bluntly rounded. Valve dimensions (n=20): length 7.5–15.0 μm, width 2.5–3.5 μm. Axial area narrow, linear, not or only weakly widening ( Fig. 136 ) near the central area. Central area large, rounded, sometimes asymmetrical ( Fig. 149 ), bordered on both sides by usually 2, up to 4 shortened striae. Raphe slightly curved with indistinct to slightly expanded, distantly spaced proximal raphe endings. Distal raphe fissures not visible in LM. Striae radiate in the middle, becoming parallel at the apices, 18–21 in 10 μm. Areolae not discernible in LM. SEM observations ( Figs 154–156 ): Externally, valve face flat ( Fig. 154, 155 ). Striae biseriate composed of small, almost rounded to slightly apically elongated areolae ( Fig. 154 ). Striae bordering the central area becoming uniseriate near the valve middle ( Figs 154, 155 ). External raphe branches straight to weakly curved. Proximal raphe endings almost straight, simple, never expanded ( Fig. 154 ). Distal raphe fissures elongated, hooked opposite the proximal raphe endings, continuing onto the mantle ( Fig. 154, 155 ). Mantle striae very short, finishing immediately beyond the valve face/mantle junction ( Fig. 155 ). Around the apices striae reduced to a few areolae ( Fig. 154 ). Valvocopula with one row of rounded poroids ( Fig. 155 ). Internally, raphe straight with simple, weakly unilaterally deflected proximal raphe endings ( Fig. 156 ). Distal raphe endings terminating onto weakly developed helictoglossae ( Fig. 156 ). Areolae internally occluded by individual hymenes. At each apex, one shallow depression present ( Fig. 156 , arrow).

Type: — ANTARCTICA. South Shetland Islands: Livingston Island, Byers Peninsula, sample BYM-051 (62° 38’ 20.1” S, 61° 06’ 44.2” W, 60 m a.s.l.), B. Van de Vijver, 15 January 2009 (holotype BR! 4457, isotype PLP! 311).

Etymology: —The specific epithet refers to the region where the species was first discovered. Ecology and confirmed distribution: —Due to possible confusion with Sellaphora seminulum ( Grunow 1860:

552) D.G. Mann (1989: 2) in the past the exact distribution of S. antarctica based on literature data is not known. The new species has been found with certainty on Livingston Island and King George Island (South Shetland Islands) and on James Ross Island. Under the name Sellaphora cf. seminulum it was also reported from Signy Island (South Orkney Islands) and Beak Island (Antarctic Peninsula area) by Sterken et al. (2015, figs 3BR-BT). The largest population of Sellaphora antarctica was found living on submerged mosses in a large lake having a circumneutral pH (7.3) and a low conductivity level (<100 μS/cm). The sample was dominated by several Psammothidium (Grunow in Cleve & Grunow 1880: 21) Bukhtiyarova & Round (1996: 3) taxa.

Figures

FIGURES 136–156. Sellaphora antarctica sp. nov. LM and part of the SEM pictures taken from the holotype population (sample BYM051) from Livingston Island (South Shetland Islands). 136–153. LM views of 18 valves from the type population. Figs 152–153 represent girdle view. 154. SEM of an entire valve, external view (picture taken from James Ross Island, sample JRI-004). 155. SEM of the valve exterior, showing the mantle and girdle. 156. SEM of an entire valve, internal view (picture taken from James Ross Island, sample JRI-11). Arrow indicates the shallow depression present at each apex. Scale bar represents 10 μm except for fig. 154 where scale bar = 5 μm and figs 155 and 156 where scale bar = 2 μm.