Pinnularia subantarctica var. elongata (Manguin in Bourrelly & Manguin) Van de Vijver & Le Cohu in Van de Vijver, Frenot & Beyens

Pinnularia subantarctica var. elongata ( Manguin in Bourrelly & Manguin) Van de Vijver & Le Cohu in Van de Vijver, Frenot & Beyens (Figs 206 –217)

Valves linear to weakly linear-lanceolate with parallel to weakly convex valve margins and broadly rounded, subrostrate apices. Valve dimensions (n=25): length 27–59 µm, valve breadth 5.4–7.9 µm. Axial area narrow, near the centre weakly deltoid. Central area forming a broad almost rectangular, sometimes asymmetrical, fascia. Raphe slightly lateral with expanded and weakly deflected central pores. Terminal raphe fissures “?”- shaped. Striae slightly to moderately radiate in the middle, becoming convergent towards the apices, 14–15 in 10 µm. Longitudinal lines clearly present.

Habitat:— Pinnularia subantarctica var. elongata was most abundant among wet mosses in areas close to the sea and in larger lakes, usually near the shoreline where the presence of animals was clearly visible. PH ranges from 6.9 to 8.4 with a specific conductance varying from 34 to almost 250 µS/cm.

Observations:— Pinnularia subantarctica var. elongata is one of the smallest Pinnularia taxa presenting a longitudinal line running across its striae due to the partly internal covering of the striae, leaving only a small opening. It cannot be confused with other species. Pinnularia microstauron has a unique valve outline with more rostrate apices and clearly convex margins.