Angusticopula cosmica Goeyers & Van de Vijver 2020, sp. nov.

Angusticopula cosmica Goeyers & Van de Vijver sp. nov.

http://phycobank.org/ 102315 Figs 28–43

The specific epithet refers to the general outlook of the valves in scanning electron microscopy giving the impression, due to the many granules, of a cosmos with numerous stars.

Holotype

CAMPBELL ISLAND • sub-Antarctic region; sample BAS303; 12 Jan. 1970; D. Vitt leg.; BR-4577.

Isotype

CAMPBELL ISLAND • same collection data as for holotype; slide at University of Antwerp, Belgium; PLP-368.

Light microscopy (Figs 28–36)

Frustules rectangular with valve diameter much larger than the mantle height. Cells always solitary; chains, even short ones, never observed. Numerous discoid plastids present. Valve diameter (n = 50): 18–45 μm, mantle height (n = 1): ca 8 μm. Valves with a low mantle and flat valve face. Internal valves never observed. Central area large, diameter 10–25 μm (50–60% of the total valve diameter, irregularly bordered by marginal striae. Marginal striae radial, clearly punctate, 31–35 in 10 μm, clearly visible in LM. Ring of rimoportulae visible close to the valve face/mantle junction (Fig. 35, arrows).

Scanning electron microscopy (Figs 37–43)

Girdle comprising a large number (up to 8) of narrow, open, non-perforated copulae (Fig. 37). Small ligulae filling the gaps created by the open copulae (Figs 37, arrows, 38). Mantle rather shallow, with dense uniseriate striation pattern, composed of very small, rounded areolae. Mantle edge with a constricted rim bordered by a serrate marginal edge (Figs 38, 39, double white arrows). Valve face/mantle junction gently sloping showing a shallow marginal ridge (Figs 39, black arrows, 40). Valves faces clearly flat (Fig. 40), entirely covered by irregularly scattered small granules (Figs 40–41). Central area weakly raised, clearly visible in oblique view (Fig. 37). Spines absent (Fig. 40). Valve face striation restricted to a broad marginal zone. Striae uniseriate, forming rather irregular series of small areolae bordered by a very shallow siliceous rim (Fig. 41). Internally, valves weakly dome-shaped (Fig. 42), perforated by a marginal pattern of small areolae, closed by individual hymenes. Areolae clearly arranged in striae, separated by very narrow interstriae. Irregular ring of rather large rimoportulae present near the mantle edge (Figs 42–43). Rimoportulae visible internally as short raised tubes (Fig. 43).

Angusticopula cosmica sp. nov. was described from a Racopilum moss vegetation collected from a wet rock east of Moubray Hill. The sample was dominated by Frankophila dalevittii, a recently described endemic species for Campbell Island (Van de Vijver et al. 2020), Diatomella balfouriana and Diatomella colonialis Van de Vijver & Le Cohu.

Class Coscinodiscophyceae Round & R.M.Crawford in Round et al. (1990) emend. Medlin & Kaczmarska Subclass Coscinodiscophycidae Round & R.M.Crawford in Round et al. (1990) Order Melosirales R.M.Crawford in Round et al. (1990) Family Melosiraceae Kütz. (Kützing 1844) emend. R.M.Crawford in Round et al. (1990) Genus Ferocia Van de Vijver et al.