Luticola contii, 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 : 162-164

Luticola contii sp. nov. ( Figs 35–49 )

Type:— ANTARCTICA. South Shetland Islands : Deception Island, Sample D 37, leg. R. Zidarova, coll. date 24/01/2013, slide no. BR- 4366 (holotype), slide PLP-255 (isotype University of Antwerp , Belgium), BRM-ZU9/68 (isotype BRM) .

Etymology:—The species is named after Gabriel (Tano) Conti, Base Commander at “Decepción” Base ( Argentina) during the 2012-2013 Antarctic season to thank him for his hospitality and readiness to help us in the field work during our (RZ) stay on Deception Island.

Valves linear with triundulate margins and rostrate-subcapitate, rostrate or almost truncated apices. Valve length 12.3– 20.7 µm, width 6.0– 8.1µm. Axial area narrow, linear, not or weakly widening towards the central area. Central area bowtie shaped to almost rectangular, bordered on both sides by 2–3 areolae. One rounded isolated pore present in the central area. Raphe straight, proximal raphe endings almost straight to weakly deflected away from the isolated pore. Distal raphe fissures very short, straight to weakly deflected away from the isolated pore. Striae radiate, 16–19 in 10 µm.

Ecology and distribution: — Due to confusion with Luticola nivalis the exact distribution of L. contii remains unknown and so far the species has been observed with certainty on Deception Island and King George Island (South Shetland Islands). The largest populations were found in soils and among almost dry mosses growing on coastal rocks, at places with moderate nutrient input and elevated salinity levels due to the proximity of the sea. Accompanying taxa included Pinnunavis gebhardii and several other Luticola species.

LM observations:— ( Figs 35–48 ): The valves are linear with almost parallel, triundulate margins. The margin undulations are moderately deep, rounded and almost equal in width. The valve apices in larger valves are rostratesubcapitate whereas in the smallest valves they are rostrate to almost truncated, always narrower than the valve middle. Valve dimensions (n=32): length 12.3–20.7 µm, width 6.0– 8.1µm. The axial area is narrow, linear (occasionally weakly lanceolate, fig. 44), not or weakly widening towards the central area. The central area is expanded into a bow-tie shaped, sometimes almost rectangular ( Figs 44, 46 ) stauros, usually bordered on both sides by a single row of 2–3 areolae. Occasionally 2–3 very short striae enclose the central area at one of the sides ( Figs 41, 48 ). One rounded isolated pore is present in the central area, located almost halfway between the raphe and the margin showing a solitary position. The raphe is straight with slightly expanded proximal raphe endings, finishing almost straight to weakly deflected away from the isolated pore. The distal raphe fissures are very short and terminate straight to weakly deflected to the same side as the central raphe endings. The striae are radiate throughout the entire valve, 16–19 in 10 µm.

SEM observations:— ( Fig. 49 ): The striae are composed of 2–4 rounded areolae that become distinctly larger towards the valve margins. The areolae next to the axial area are very small and rounded. The areolae of the outer row are much larger and usually transapically elongated. One row of rounded areolae, not interrupted at the poles, is present on the valve mantle. The isolated pore opening is small, rounded to weakly transapically elongated. The proximal raphe endings are first weakly deflected away from the isolated pore but then hook shortly towards the isolated pore. Small pit-like depressions are present next to the raphe endings. The distal raphe fissures terminate near the last stria but never extend onto the mantle, first weakly deflected away from the isolated pore and then shortly hooked towards the isolated pore-bearing side.

Similar species:— Luticola contii has a unique raphe structure that is not observed in any other Luticola species with triundulate margins and this makes it easy to distinguish from the similar taxa, even in LM. However, in Antarctica the species has been reported for quite a long time as L. nivalis . Based on the studies of L. nivalis by Levkov et al. (2013: 175), the latter species has a denser striation pattern and different raphe endings ( Table 3). The proximal raphe endings in L. nivalis are distinctly bent opposite the isolated pore and not towards the isolated pore, while the distal raphe fissures are hooked and much more prolonged compared to the distal raphe fissures in L. contii . Other Luticola taxa with a similar valve outline include Luticola cocquytiae Levkov, Metzeltin & Pavlov in Levkov et al. (2013: 89), L. pseudonivalis (Bock) Levkov, Metzeltin & Pavlov in Levkov et al. (2013: 199) and L. pulchra (McCall) Levkov, Metzeltin & Pavlov in Levkov et al. (2013: 202). They all have a finer striation pattern and proximal raphe endings that are bent or deflected opposite to the isolated pore-bearing side ( Table 3). Other known Luticola taxa with triundulate margins are sufficiently different in valve outline and/or shape of the apices, striation and raphe structure to avoid confusion. In Antarctica, however, the species can be easily misidentified with L. olegsakharovii sp. nov. (see below). Detailed comparison between these two Antarctic taxa is given under L. olegsakharovii and in Table 3.

Figures

FIGURES 35–49. Luticola contii Zidarova, Levkov & Van de Vijver, sp. nov. Light (LM) and scanning electron microscope (SEM) micrographs: Figs 35, 36–48. LM of 14 valves from the type population, Deception Island, sample D37 (scale bars = 10 µm). Fig. 49. SEM external view of a valve from the type population, Deception Island, sample D37 (scale bar = 5 µm).