Ferocia houkiana Goeyers & Van de Vijver 2020, sp. nov.

Ferocia houkiana Goeyers & Van de Vijver sp. nov.

http://phycobank.org/ 102316 Figs 44–73

The species is named in honour of our colleague and friend Dr Václav Houk (Institute of Botany, Czech Republic) to acknowledge him for his work on melosiroid diatoms.

Holotype

CAMPBELL ISLAND • sub-Antarctic region; sample BAS284; 12 Jan. 1970; D. Vitt leg.; BR-4578.

Isotype

CAMPBELL ISLAND • same collection data as for holotype; slide at University of Antwerp, Belgium; PLP-369.

Light microscopy (Figs 44–62)

Frustules rectangular. Cells connected via a central ring of spines, forming short chains. Numerous discoid plastids present. Girdle composed of large number of very narrow copulae, covering two adjacent valves. Valve diameter (n = 20): 4–11 μm, mantle height (n = 5): 4.0–5.5 μm. Valves with a relatively low mantle and rounded, flat valve face. Internal valves occasionally observed (Figs 50–51). Central area dominated by a regular crown of spines. Scattered spines present on the entire valve face. Striae not discernible in LM.

Scanning electron microscopy (Figs 63–73)

Girdle composed of a large number (up to 20) of narrow, open, non-perforated copulae (Fig. 63). Girdle bands attached to one of the valves of a cell extending over one of the new daughter valves after each cell division, meeting and overlapping with the bands attached to the other parent valve, covering that way two new valves of the daughter cells (Fig. 63). Copulae fimbriate on pars inferior giving the misleading impression of perforated girdle bands in non-eroded girdles (Figs 63, 65). Valves connected via central crown of large, wedge-shaped spines (Fig. 64). Müller step on mantle occasionally observed (Fig. 66, arrow). Mantle striae straight, composed of small, rounded areolae (Figs 64, 66). Near mantle edge, areolae very much smaller than near and at valve face/mantle junction, areolae irregularly scattered (Fig. 64). Mantle edge not rimmed. Rimoportula openings on the mantle not distinguishable from mantle areolae. Valve face/mantle junction thickened, relatively abrupt (Figs 63, 66). Valve face dominated by a central regular ring of large, relatively low, wedge-shaped spines (Figs 67–68). Spines hollow but apparently chambered with small silica walls inside the spines (Fig. 68). Spines occasionally lacking or reduced to series of low silica outgrowths (Fig. 69). Central area clearly raised, bordered by a narrow flat valve face edge, covered by an irregular pattern of small, rounded to slit-like areolae (Figs 67, 68, arrows). Striation pattern not detectable in the areolae. Internally, a few sessile rimoportula visible close to the mantle edge (Figs 71, 72, arrows), irregularly scattered. One rimoportula present near the valve center on the valve face (Figs 70, 73, arrow). Internal valve surface covered by numerous small areolae (Fig. 73).

Ferocia houkiana sp. nov. is a frequently observed species on Campbell Island. It was found in several moss samples on rocks and next to waterfalls, usually dominated by species belonging to the genera Pinnularia, Pinnunavis and Eunotia. The type sample is dominated by the new species of Ferocia and is accompanied by Pinnularia borealis s. lat. Ehrenb. which points to a drier character of the environment, often influenced by sea spray (Van de Vijver et al. 2002).