Chamaepinnularia elliptica 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 : 40-41

Chamaepinnularia elliptica Zidarova, Kopalová & Van de Vijver , sp. nov. ( Figs 18–34 )

LM observations ( Figs 18–30 ): Valves elliptic-lanceolate to rhombic-elliptic (e. g. Figs 20, 25 ) in larger specimens, more strictly elliptic in smaller valves with clearly convex margins and broadly rounded apices. Valve dimensions (n=27): length 12.0–15.0 μm, width 3.8– 4.5 μm. Valves on Livingston Island, the South Shetland Islands ( Figs 28–30 ) slightly smaller than valves on James Ross Island ( Figs 18–27 ). Axial area weakly lanceolate, narrow near the apices and gradually widening towards the central area. Central area variable in size, rhombic (e. g. Fig. 26 ) to rounded (e. g. Fig. 27 ), rarely asymmetric ( Fig. 19 ), bordered on both sides by several shortened striae, never forming a fascia. Raphe straight with straight simple to weakly drop-like expanded pores. Distal fissures not discernible in LM. Striae radiate in the middle, becoming parallel toward the apices, 22–24 in 10 μm. SEM observations ( Figs 31–34 ): Striae composed of two large areolae, one located on the valve face and a second on the mantle, separated by a silica line at the valve face/mantle junction, covered externally by porous hymenes ( Figs 31, 32 ). Areolae continuing around the poles ( Fig. 32 ). Virgae and striae of equal width. Raphe branches straight. Proximal external raphe endings shortly deflected to one side, terminating in small, spatulate pores ( Figs 31, 32 ). Distal raphe fissures short, finishing on the valve face, deflected opposite the central raphe endings ( Figs 31, 32 ). Internally, proximal raphe endings unilaterally bent ( Fig. 34 ). Distal endings terminating in small helictoglossae ( Fig. 33 ). Central nodule clearly developed ( Fig. 33 ).

Type: — ANTARCTICA. James Ross Island: Lachman 2 Lake, sample JRI-D02 (63° 47’ 59.9” S, 57° 48’ 31.1” W), L. Nedbalová, 22 January 2008 (holotype BR! 4450, isotype PLP! 304).

Etymology: —The specific epithet refers to the overall elliptic shape of the valves of this species.

Ecology and confirmed distribution: — Chamaepinnularia elliptica has been found on several localities in the Maritime Antarctic Region, although never in large populations. The largest populations were observed on James Ross Island and Livingston Island. On James Ross Island, the species was found in a large, coastal lake with an almost circumneutral pH (7.3) and a low conductivity value (120 μS/cm). On Livingston Island, the largest population was recorded in a circumneutral (pH 6.7) run-off river from the Rotch Dome ice cap bordering Byers Peninsula. Only a few valves were observed on King George Island and Nelson Island (South Shetland Islands) among cyanobacterial mats and green algae on the bottom of small pools and on very wet soils.

Family Cosmioneidaceae

Genus Cosmioneis D.G. Mann & Stickle in Round et al. (1990: 665)

Figures

FIGURES 18–34. Chamaepinnularia elliptica sp. nov. Most LM and part of the SEM pictures taken from the holotype population (sample JRI-D02) from James Ross Island. 18–27. Light microscopy observations. 28–30. LM views of valves from South Shetland Islands. 31. SEM of an entire valve, external view (picture taken from Livingston Island, sample BY040). 32. SEM of an entire valve, external view. 33. SEM of an entire valve, internal view (picture taken from Livingston Island, sample BY040). 34. SEM of an entire valve, internal view. Scale bar represents 10 μm except for fig. 34 where scale bar = 1 μm.