Luticola olegsakharovii, Zidarova & Levkov & Vijver, 2014

Zidarova, Ralitsa, Levkov, Zlatko & Vijver, Bart Van De, 2014, Four new Luticola taxa (Bacillariophyta) from Maritime Antarctica, Phytotaxa 170 (3), pp. 155-168 : 164-167

Luticola olegsakharovii sp. nov. ( Figs 50–64 )

Type:— ANTARCTICA. South Shetland Islands : King George Island , Fildes Peninsula, Sample KGI81, leg. R. Zidarova, coll. date 13/02/2013, slide no. BR-4367 (holotype), slide PLP-256 (isotype University of Antwerp , Belgium), BRM-ZU9/71 (isotype BRM) .

Etymology:—The species is named after Oleg Sakharov, Base Commander of “Bellingshausen” Russian Station on King George Island during 2012-2013 Russian Antarctic overwintering Expedition to thank him for his hospitality and his professionalism in solving successfully the problems we had during our (RZ) field trips there.

Valves linear to linear-elliptic with triundulate margins and subcapitate apices. Valve length 20.6–26.0 µm, width 7.6–9.5 µm. Axial area narrow, weakly lanceolate. Central area bow-tie shaped, bordered on both sides by a single row of 2–3 areolae. One rounded isolated pore present in the central area. Raphe straight with proximal and distal raphe endings shortly bent away from the isolated pore. Striae radiate, 15–17 in 10 µm.

Ecology and distribution:— Luticola olegsakharovii was observed on several islands of the South Shetland Archipelago: Livingston Island, Deception Island and King George Island. The largest populations were found in moist soils with elevated nutrient input, close to skuas nests, usually accompanied by various Pinnularia and Humidophila (formerly Diadesmis ) species and other Luticola taxa. It is possible that the species is more widespread in the Antarctic but its distribution is obscured due to confusion with Luticola nivalis in the past.

LM observations:— ( Figs 50–62 ): The valves are linear to linear-elliptic with triundulate margins and subcapitate, broadly rounded apices. The undulations of the margins are rounded, with the median one slightly wider than the others. Valve dimensions (n=23): length 20.6–26.0 µm, width 7.6–9.5 µm. The axial area is narrow, weakly lanceolate and widens towards the central area. The central area is expanded into a bow-tie shaped stauros and is bordered on both sides by a single row of 2–3 areolae. Occasionally the central area is enclosed at the isolated pore-bearing side by very short striae ( Figs 56, 57 ). One rounded isolated solitary pore is present in the central area, located almost halfway between the raphe and the margin. The raphe is straight with both proximal and distal raphe endings shortly bent away from the isolated pore ( Fig. 50 ). The striae are radiate throughout, 15–17 in 10 µm.

SEM observations:— ( Figs 63–64 ): Externally, the striae are composed of 2–4 transapically elongated areolae becoming larger towards the margins. Rarely some of the areolae of the inner row are almost rounded ( Fig. 63 ). One row of rounded areolae, interrupted at the valve poles, is present on the valve mantle. The external isolated pore opening is transapically elongated. The external proximal raphe endings are slightly expanded and are shortly bent away from the isolated pore. The distal fissures are short and terminate just below the last striae, bent to the same direction as the proximal raphe endings. Internally ( Fig. 64 ), the central nodule is thickened. The raphe is straight and terminates onto small helictoglossae at the poles. The internal isolated pore opening is rounded and covered by an almost circular silica flap. The areolae are covered by hymenes and form a continuous strip over the striae.

Similar species:— Luticola olegsakharovii is most similar to L. contii (see above) but can be separated by the slightly larger valve width, the rounded, subcapitate apices and the completely different raphe structure with shortly bent opposite to the pore-bearing side distal and central raphe endings, contrary to L. contii where both the central and distal raphe endings are hooked toward the pore-bearing side ( Table 3). Likewise L. contii , L. olegsakharovii has also been reported from Antarctica as L. nivalis . All similar taxa in the L. nivalis group can be easily differentiated from L. olegsakharovii based on the distal raphe fissures, which are strongly hooked and not shortly bent as in L. olegsakharovii . Moreover, the distal raphe endings in the similar taxa of L. nivalis group are hooked to the porebearing side and not to the side opposite the isolated pore ( Table 3). Luticola nivalis has also a smaller valve width and a finer striation pattern ( Table 3). Other similar taxa, such as L. pulchra , L. cocquytiae and L. pseudonivalis , apart of hooked distal raphe fissures, also have a finer striation pattern ( Table 3). Luticola cocquytiae and L. pseudonivalis both have much smaller valve dimensions ( Table 3). Luticola pseudonivalis and L. pulchra also have much smaller valve apices compared to L. olegsakharovii . Other Luticola taxa with triundulate margins are sufficiently different in valve outline and raphe structure to be confused with L. olegsakharovii .

Figures

FIGURES 50–64. Luticola olegsakharovii Zidarova, Levkov & Van de Vijver, sp. nov. Light (LM) and scanning electron microscope (SEM) micrographs: Figs 50, 51–62. LM of 13 valves from the type population, King George Island, sample KGI81 (scale bars = 10 µm). Fig. 63. SEM external view of a valve from the type population, King George Island, sample KGI81 (scale bar = 5 µm). Fig. 64. SEM internal view of a valve from the type population, King George Island, sample KGI81 (scale bar = 5 µm).