Mayamaea sweetloveana 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 : 43

Mayamaea sweetloveana Zidarova, Kopalová & Van de Vijver , sp. nov. (Figs 46–58)

LM observations (Figs 46–56): Valves elliptic with convex margins and broadly rounded, never protracted apices. Valve dimensions (n=20): length 6.0–7.0 μm, width 3.0–3.5 μm. Axial area very narrow, linear, conforming with the sternum. Central area almost entirely lacking. Raphe straight, enclosed in a heavily silicified sternum. Distal raphe fissures not discernible in LM. Striae strongly radiate throughout the entire valve, 25–30 in 10 μm. Central striae alternatingly shortened. Areolae not discernible in LM. SEM observations (Figs 57–58): Striae composed of several square to rounded areolae, ca. 50 in 10 μm, covered externally by clearly porous hymenes. Areolae becoming more elongated near the valve mantle (Fig. 57). Around the apices areolae more slit-like, positioned at the mantle/valve face junction. External raphe branches straight with distinctly enlarged, spathulate, almost not deflected proximal raphe endings. Distal raphe fissures very short, deflected opposite to the proximal raphe endings, never continuing onto the mantle but terminating near the last striae at the apices (Fig. 57). Internal raphe branches straight with simple proximal raphe endings (Fig. 58). Distal raphe endings terminating onto small helictoglossae (Fig. 58). Areolae clearly visible as rectangular to rounded pores (Fig. 58).

Type: — ANTARCTICA. James Ross Island: Ulu Peninsula, Nadĕje Lake, sample D24 (63° 48’ 51.9” S, 57° 50’ 05.6” W), L. Nedbalová, 13 February 2008 (holotype BR! 4452, isotype PLP! 306).

Etymology: —The specific epithet refers to Drs. Maxime Sweetlove (Ghent University, Belgium), member of the CCAMBIO project.

Ecology and confirmed distribution: — Mayamaea sweetloveana has up to now only been found in a few samples from James Ross Island. Due to confusion with other Mayamaea taxa such as M. atomus ( Kützing 1844: 108) Lange-Bertalot (1997: 72) and M. permitis ( Hustedt 1945: 919) Bruder & Medlin (2008: 327) , its actual distribution is not entirely clear. The largest population (almost 75% of all counted valves) was observed in Nadĕje Lake, a cirque lake on Ulu Peninsula (James Ross Island). This is a rather shallow lake at an elevation of 240 m a.s.l. with an alkaline pH (8.4), low conductivity (<250 μS/cm) and low nutrient and phosphate values.