Angusticopula chilensis Houk

Angusticopula chilensis (Grunow) Houk et al.

http://phycobank.org/ 102314 Figs 1–27

Melosira dickiei forma chilensis Grunow in Van Heurck (1882: pl. 90, figs 13–14).

Since only the original slide 1015 in the Grunow collection (V) is available as type material and unmounted material is no longer present (A. Igersheim, Grunow Collection, Vienna, pers. comm.), we designate sample BAS 286 as epitype to illustrate in more detail the morphological structures of this species.

Epitype (here designated)

CAMPBELL ISLAND • sample BAS286; 12 Jan. 1970; D. Vitt leg.; BR-4576.

Light microscopy (Figs 1–19)

Frustules cylindrical to short barrel-shaped. Cells most likely forming short chains, as often two sibling valves are found attached to each other. Valve diameter (n = 20): 8–25 μm, mantle height (n = 10): 4.5–11 μm. Valves showing thick wall (Fig. 8), having a relatively low mantle and rounded, flat valve face. Internal valves occasionally present (Figs 5, 12). Rimoportulae organized in marginal ring close to the valve face margin, visible as a series of tube-like channels. Striae and areolae not discernible in LM.

Scanning electron microscopy (Figs 20–27)

Girdle composed of a large number (up to 8) of narrow, open copulae (Figs 20–22) showing a fimbriate pars interior (Fig. 22, arrows). Small ligulae fill the gaps created by the open copulae (Fig. 20, arrows). Mantle rather high, densely punctated, clearly rimmed (Figs 21, arrows, 26). Valve faces clearly flat (Fig. 23), lacking granules and spines (Figs 23–24), finely perforated by very small areolae, arranged in irregular, uniseriate striae, ca 80 in 10 μm (Fig. 24). External rimoportula openings visible as slightly elongated slits (Fig. 26, arrows). Valves very thick (Fig. 27). Internally, sessile rimoportulae arranged in an irregular ring near the valve face/mantle junction, visible as slightly raised projections (Figs 25, 27).

The largest populations of A. chilensis were found in mosses growing on cliffs next to a waterfall dominated by several species of Humidophila, Diatomella balfouriana Grev. and Achnanthes muelleri C.F.W.Carlson emend. Van de Vijver & Goeyers. The latter species are all known to thrive mostly in aerophilic, moist environments (Van de Vijver et al. 2002). Angusticopula chilensis was also found on several sub-Antarctic islands located in the southern Indian Ocean such as Iles Crozet (Van de Vijver et al. 2002), Iles Kerguelen (Van de Vijver et al. 2001) and the Prince Edward Islands (Van de Vijver et al. 2008). The species was almost always incorrectly identified as Melosira sp. or Melosira varians C.Agardh.