Ferocia subantarctica Van de Vijver & Houk, 2019

Vijver, Bart Van De & Houk, Václav, 2019, Two new centric diatoms (Bacillariophyta) from the sub-Antarctic region, Phytotaxa 394 (1), pp. 50-58 : 52

Ferocia subantarctica Van de Vijver & Houk sp. nov. Figs 1–20

LM ( Figs 1–18 ): Frustules cylindrical with hemispherical valves bearing large, acute spines connecting the frustules forming short chains.Valve diameter (n=50): 5.0–14.0 μm, valve height 3.0–5.0 μm. Spines usually arranged at the valve face/mantle margin with some irregularly scattered spines on the valve face. Valves dome-shaped with a moderately high mantle and rounded valve face. Small rounded hyaline central area present. Internal valves occasionally present. SEM ( Figs 19–25 ): Valves hemispherical with a large, very thick mantle ( Figs 19, 24 ) and a slightly domed valve face. Müller step clearly visible ( Fig. 21 , arrows). A few large, thick, linking spines present on the valve face/mantle junction. Spines not entirely hollow, usually broken during observations, when not eroded showing sharp, acute endings ( Figs 22, 23, 24 ). Valve face lacking spines or granules, rather smooth or with very weakly raised, slit-like ridges. Central part of the valve face flattened, hyaline, rounded, often entirely devoid of any ornamentation or areolae ( Fig. 23 ). Cingulum composed of a large number of narrow, open, unperforated ligulate copulae ( Fig. 20 ). Pars interior of the copulae clearly fimbriate ( Fig. 20 ). Areolae on the mantle small, rounded, irregularly scattered on the mantle, almost never arranged in rows ( Figs 21, 24 ). Internally, ring of slit-like, equidistantly placed rimoportulae present near the valve face/mantle junction ( Fig. 25 , arrows). Rimoportulae rounded, located on a slightly raised silica thickening. Areolae tubular, internally individually covered by vela ( Fig. 25 ).

Type:— Round Hill, Heard Island, Subantarctica, sample HE199 (53°03’50.1S / 73°38’10.1”E, leg. N. J. M.Gremmen), coll. date 13/12/2000 (holotype BR!, slide no. 4553, isotype PLP!, slide no. 360, University of Antwerp, Belgium).

Etymology:— The specific epithet refers to the wide geographical area where the new species is found: the sub-Antarctic islands.

Ecology, distribution and associated diatom flora:— Ferocia subantarctica was found in a several moss samples on almost every subantarctic island in the southern Indian Ocean. Most populations were found on Heard Island where the species seems typical for wet terrestrial mosses (such as Bartramia , Brachythecium or Orthotheciella ) growing in shallow, semi-shaded damp caves. Smaller populations were found on the Prince Edward Islands and Ile de la Possession (Crozet Archipelago) where the species was present in wet soils and cracks in coastal cliffs (Van de Vijver, unpubl. res.). Accompanying species include several Humidophila species such as H. ingeae (Van de Vijver in Van de Vijver et al. 2002b: 338) Lowe et al. (2014: 358), H. vidalii (Van de Vijver & P. Ledeganck in Van de Vijver et al. 2002b: 334) Lowe et al. (2014: 359) and H. arcuata ( Heiden & Kolbe 1928: 62) Lowe et al. (2014: 357) , several Psammothidium species (such as P. investians ( Carter 1966: 445) Bukhtiyarova (in Bukhtiyarova & Round 1996: 26) or P. germainii (Manguin in Bourelly & Manguin 1954: 20) Sabbe (in Sabbe et al: 2003:) and Pinnularia obscura Krasske (1932: 117) . These species are all known to prefer typical terrestrial, wet and often shaded conditions.

Class Coscinodiscophyceae Round & Crawford in Round et al. (1990)

Order Arcanodiscales E.Morales & Maidana in Maidana et al. (2017)

Family Arcanodiscaceae Maidana & E.Morales in Maidana et al. (2017)

Genus Arcanodiscus Maidana & E.Morales in Maidana et al. (2017)

Figures

FIGURES 1–25. Ferocia subantarctica sp. nov.Light (LM) and Scanning electron (SEM) micrographs of the holotype population (sample HE199) from Round Hill, Heard Island, Subantarctica. Figs 1–10 LM photographs of several valves in girdle view connected to each other via spines. In some pictures, the girdle bands can be seen. Figs 11–18. LM photographs in valve face view. Fig. 19. SEM view of several valves in girdle view showing the domed valve face, the mantle with the Müller step and the numerous girdle bands. Fig. 20. SEM view of the girdle bands. Fig. 21. Mantle SEM view of two valves connected via linking spines. The arrows indicate the Müller step. Fig. 22. SEM view of a valve face showing the irregular placement of the spines. Note the lack of a large hyaline zone in the central area. Fig. 23. SEM mantle view of a valve with the slightly domed valve face, the irregular placement of the spines and the hyaline central area. Fig. 24. SEM view of the valve mantle showing the mantle areolae and some broken, not entirely hollow spines. Fig. 25. Internal SEM view of entire valve. The arrows indicate the rimoportulae. Note the areolar canal in the broken part of the valve. Scale bars represent 10 μm except for Fig. 22 where scale bar = 5 μm.