Caloneis australis 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 : 40

Caloneis australis Zidarova, Kopalová & Van de Vijver , sp. nov. ( Figs 1–17 )

LM observations ( Figs 1 – 12 ): Frustules in girdle view rectangular ( Fig. 12 ). Larger valves linear with weakly undulating margins, slightly inflated in the middle, and broadly rounded, almost not-protracted apices ( Figs 2, 3 ). Smaller valves linear to linear-elliptic with almost straight margins and broadly rounded, non-protracted apices ( Figs 9 – 11 ). Initial valves ( Fig. 1 ) with distinctly inflated valve margins in the valve middle. Valve dimensions (n=16): length 17.0–40.2 (42.0) μm, width 4.6–6.2 (7.7) μm. Axial area linear, very narrow near the apices but gradually widening towards the central area. Central area forming a broad rectangular, occasionally ( Fig. 11 ) asymmetrical fascia. Two lunate markings always visible in the central area in LM, located on both sides of the proximal raphe endings. Initial valves ( Fig. 1 ) lacking raphe, with clearly lanceolate axial area widening to the valve middle, forming a rhombic central area, bordered on both sides by short striae. Raphe lateral with unilaterally weakly deflected, indistinct, distantly spaced proximal raphe endings, terminating in the central area beyond the striae. Distal raphe fissures visible in larger and medium-sized valves (e. g., Figs 3, 5 ), strongly hooked opposite to the proximal raphe endings. Striae parallel to weakly radiate throughout the entire valve, 22–24 in 10 μm. Longitudinal lines are hard to resolve. SEM observations ( Figs 13–17 ): Valve face flat, curving into a deep mantle ( Fig. 13 ). Mantle quite large with a straight margin showing several longer irregular, deep slits and small rounded plaques ( Figs 15, 17 , arrows). Striae continuing shortly onto the mantle, multiseriate, composed of four rows of small, rounded poroids, occluded by hymenes ( Figs 14, 15 ). Raphe branches straight with almost straight to weakly unilaterally deflected, indistinct proximal raphe endings ( Figs 13, 14 ). Distal raphe fissures elongated, hooked, continuing onto the mantle ( Fig. 13 ). Several (6–7) elliptic, shallow depressions, organized in two lunate patterns present in the central area ( Figs 13, 14 ). Internally, raphe branches straight. Proximal raphe endings shortly unilaterally bent ( Fig. 16 ). Distal raphe endings terminating onto small linear-elliptical helictoglossae ( Fig. 16 ). Axial plate covering the alveoli, leaving only small marginal openings bordered by costae ridges, weakly thickened and raised from the valve face ( Fig. 16 ). Girdle composed of at least three, open bands, with a single row of small, elliptical pores on the pars exterior ( Fig. 17 ).

Type: — ANTARCTICA. South Shetland Islands: Livingston Island, Byers Peninsula, sample BY062 (62° 38’ 34.5” S, 61° 00’ 39.5” W, 80 m a.s.l.), B. Van de Vijver, 17 January 2009 (holotype BR! 4449, isotype PLP! 303).

Etymology: —The specific epithet ‘ australis ’ (Latin for ‘southern’) refers to the geographic distribution of the new species.

Ecology and confirmed distribution: — Caloneis australis has been observed with certainty on all major islands of the South Shetland Archipelago and on James Ross Island. It is however likely that the species is more widespread in the region but up to now it has been reported probably under the name of Caloneis bacillum . Careful analysis of all past records of the latter taxon in Antarctica should lead to a better biogeographical distribution of the new species. Large populations of Caloneis australis are typical in both larger lakes and small pools on the islands with a slightly alkaline pH (7.1–7.8), low to moderate conductivity (50–670 μS/cm) and low nutrient and sulphate levels.

Family Pinnulariaceae

Genus Chamaepinnularia Lange-Bertalot & Krammer in Lange-Bertalot & Metzeltin (1996: 32)

Figures

FIGURES 1–17. Caloneis australis sp. nov. LM and most SEM pictures taken from the holotype population (sample BY062) from Livingston Island (South Shetland Islands). 1–12. Light microscopy observations. Fig. 1 shows an intial valve, and Fig. 12 shows the girdle view. 13. SEM of an entire valve, externally. 14. SEM detail of the valve showing the central area and the lunate markings. 15. SEM detail of the valve face and mantle showing the striae; arrows indicate the slits on the mantle. 16. SEM of an entire valve, internal view (picture taken from James Ross Island, sample JRI032). 17. SEM detail of the mantle and girdle, showing the single row of pores on the valvocopula; arrows indicate the rounded plaques (picture taken from James Ross Island, sample JRI015). Scale bar represents 10 μm except for figs 14, 15 and 17 where scale bar = 1 μm.