Gomphonema jamesrossense Van de Vijver, Kopalová, Zidarova & Kociolek, 2016

Vijver, Bart Van De, Kopalová, Kateřina, Zidarova, Ralitsa & Kociolek, J. Patrick, 2016, Two new Gomphonema species (Bacillariophyta) from the Maritime Antarctic Region, Phytotaxa 269 (3), pp. 209-220 : 210-212

Gomphonema jamesrossense Van de Vijver, Kopalová, Zidarova & Kociolek , sp. nov. ( Figs 1–21)

LM ( Figs 1–16): Frustules in girdle view almost rectangular, weakly clavate with narrower footpole ( Figs 15, 16). Valves linear-clavate with almost parallel margins and broadly rounded obtuse head- and footpole. Valves occasionally asymmetrical to the apical axis. Valve dimensions (n=25): length 20–37 μm, width 3.5–4.5 μm, the greatest width being almost in the middle of the valve. Axial area narrow, linear to linear-lanceolate, almost 1/6 of the total valve width, never widened until the central area. Central area asymmetrical, rectangular. One side with one very shortened stria, other side with one longer stria. Stigmoid present at the end of the longer stria, almost not separated from the last areola. Raphe branches undulate, weakly lateral with straight to slightly deflected, simple proximal raphe endings and hooked distal fissures. Striae clearly radiate near the central area becoming almost parallel towards the headpole, 11–14 in 10 μm. Near the apices, striae positioned more closely together, up to 17 in 10 μm. Areolae almost not discernible in LM. SEM ( Figs 17–21): Striae uniseriate composed of “C”- to “3”-shaped areolae ( Figs 17, 18). Striae continuing uninterruptedly onto the mantle, eventually terminating in one small rounded areola ( Fig. 21). Mantle edge forming a relatively broad hyaline zone ( Fig. 21). Footpole with a hyaline tip, bordered by a large apical pore field composed of up to 8 rows of very small pores ( Fig. 18). Apical pore field bisected by the distal raphe fissures ( Fig. 18). External raphe branches clearly undulate ( Fig. 17). External proximal endings weakly deflected terminating in simple, almost non-expanded pores ( Fig. 17). Distal raphe fissures (strongly) hooked, almost not continuing onto the mantle ( Fig. 18). External stigmoid opening rounded, not more distantly separated from the last areola of the central stria ( Fig. 17). Foot- and headpole with small pseudoseptum ( Fig. 19). Internally, central nodule raised. Internal proximal raphe endings positioned closely together, clearly recurved ( Fig. 20). Distal raphe endings terminating on small helictoglossae ( Fig. 19). Striae internally bearing vimines, oriented perpendicularly to the striae. Occasionally, areolae subdivided by transapical vimines ( Fig. 20, arrow). Internal stigmoid opening slit-like ( Fig. 20).

Type:— JAMES ROSS ISLAND. Ulu Peninsula: Lake Katia II, sample D15 (63° 52’ 15.9” S, 57° 58’ 32.5”), L. Nedbalová, 1 February 2008 (holotype BR! slide no. 4444, isotype PLP! slide 299, University of Antwerp, Belgium).

Ecology and distribution: — The highest relative abundance of Gomphonema jamesrossense was found in an epilithon sample, collected from Katia II Lake, on the Ulu Peninsula, at an altitude of 45 m a.s.l. The lake has circumneutral pH (7.3) with a moderate conductivity (580 μS/cm), very low nutrient but higher salinity levels (Cl- 106 mg /l, SO 4 2-: 66 mg /l). The species was likewise found in several other samples of James Ross Island but always in very low abundances. On other investigated localities of the Maritime Antarctic Region, the species seems to be absent so far.

Etymology: — The species is named after James Ross Island where several populations were found.

Taxonomic remarks: — Although Gomphonema jamesrossense shows a typical gomphonemoid structure and outline, there are hardly any Gomphonema taxa that can be confused with the new species. Gomphonema clavatulum Reichardt (1999: 25) shows a slight resemblance in valve outline although the footpole in the later is more acutely rounded giving the valve a more clavate outline compared to the almost linear valves in G. jamesrossense . Gomphonema sarcophagus Gregory (1856: 13) has a similar linear outline, but with clearly protracted, rostrate headpoles and footpoles. The Antarctic Gomphonema signyensis has a less linear valve outline with a narrower headpole, compared to G. jamesrossense , a larger valve width of more than 5 μm ( Kociolek & Jones 1995), whereas the valves of G. jamesrossense do not exceed 4.5 μm in width, and a finer striation of up to 18 striae in 10 μm (instead of up to 14 in G. jamesrossense ).