Pinnularia gemella Van de Vijver

• Main Authors: Zidarova, Ralitsa, Kopalová, Kateŕina, Vijver, Bart Van De
• Format: Text
• Language: unknown
• Published: Zenodo 2012
• Subjects: Biodiversity; Taxonomy; Chromista; Bacillariophyta; Bacillariophyceae; Naviculales; Naviculaceae; Pinnularia; Pinnularia gemella; Pinnularia subantarctica; Pinnularia subantarctica var. elongata manguin in bourrelly & manguin van de vijver & le cohu in van de vijver, frenot & beyens; Antarctic; The Antarctic; South Shetland Islands; Livingston Island; Byers; Hurd; Byers peninsula; Hurd peninsula; Antarc*
• Online Access: https://dx.doi.org/10.5281/zenodo.4976120; https://zenodo.org/record/4976120

Pinnularia gemella Van de Vijver (in Van de Vijver et al. 2009: 432) (Figs 197–204) Valves linear with strictly parallel margins and broadly rounded, non-protracted apices. Valve dimensions (n=20): length 43–52 µm, width 7.3–8.8 µm. Axial area moderately broad, linear to linear-lanceolate, not, or only very slightly, widening towards the central area. Central area forming a rectangular, usually asymmetrical fascia. Raphe lateral with deflected proximal raphe endings terminating in weakly expanded pores. Distal raphe fissures bayonet-shaped. Striae almost parallel throughout the entire valve. Longitudinal lines absent. One single row of small spines visible on the primary side, 9–10 in 10 µm. Valves usually found in pairs, connected by linking spines, lying in juxtaposition. Habitat:— Pinnularia gemella was found in several larger lakes on the central plateau of Byers Peninsula. All lakes had a pH varying between 7.2 and 7.5 and a very low specific conductance level (<60 µS/ cm). The species seems to be absent from Hurd Peninsula. Observations:— Pinnularia gemella cannot be mistaken with any other species of Pinnularia due to the presence of the spines on the primary side. Only a few Pinnularia species have spines or form colonies in juxtaposition. Van de Vijver et al. (2004a, 2009) reviewed all colony- and/or spine-forming species of Pinnularia . Pinnularia subantarctica var. elongata has a similar valve outline but higher stria density and lacks the typical spines of P. gemella . 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. 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. : Published as part of Zidarova, Ralitsa, Kopalová, Kateŕina & Vijver, Bart Van De, 2012, The genus Pinnularia (Bacillariophyta) excluding the section Distantes on Livingston Island (South Shetland Islands) with the description of twelve new taxa, pp. 11-37 in Phytotaxa 44 on pages 31-32, DOI: 10.11646/phytotaxa.44.1.2, http://zenodo.org/record/4894994 : {"references": ["Van de Vijver, B., Agius, J. T., Gibson, J. A. E. & Quesada, A. (2009) An unusual spine-bearing Pinnularia species from the Antarctic Livingston Island (South Shetland Islands). Diatom Research 24: 431 - 441.", "Van de Vijver, B., Gremmen, N., Beyens, L. & Le Cohu, R. (2004 a) Pinnularia sofia Van de Vijver & Le Cohu spec. nov., a new spine-bearing, chain-forming Pinnularia species from the sub-Antarctic region. Diatom Research 19: 103 - 114."]}