Luticola bogaertsiana, 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 : 160

Luticola bogaertsiana sp. nov. ( Figs 21–34 )

TYPE:— ANTARCTICA. South Shetland Islands : King George Island , Fildes Peninsula, Sample KGI12, leg . R. Zidarova, coll. date

30/01/2013, slide no. BR-4365 (holotype), slide PLP-254 (isotype University of Antwerp , Belgium), BRM-ZU9/70 (isotype BRM). Etymology :— The species is named after our dear colleague and friend Ann Bogaerts (Botanic Garden Meise, Belgium) .

Valves linear with a single constriction in the middle, and broadly rounded, capitate apices. Valve length 16.5–22.0 µm, width 5.7–7.3 µm (constriction) and 7.0– 8.7 µm (widest part). Axial area narrow, linear, weakly widening towards the elliptical to bow-tie shaped central area. Central area bordered on both sides by a single row of areolae. One rounded isolated pore present in the central area. Raphe almost straight with proximal endings weakly deflected opposite the pore-bearing side and then hooked to the pore, and distal raphe fissures abruptly hooked to the pore-side. Striae radiate throughout, 15–19 in 10 µm.

Ecology and distribution: — Luticola bogaertsiana is rarely observed and usually in very low numbers in soils and mosses, growing on rocks as well as on wet rocks at places with moderate to relatively high nutrient levels and elevated salinity. The largest populations were found in soils on coastal rocks and on wet rocks on King George Island where the species was recorded together with various Humidophila Lowe, Kociolek, Johansen, Van de Vijver, Lange-Bertalot & Kopalová (2014: in press) [formerly Diadesmis Kützing (1844: 109) ] and Luticola taxa. Small populations were also observed on Livingston Island and Deception Island (Zidarova, Van de Vijver, pers. obs.). So far, no data exist from other localities in Antarctica. Kellogg & Kellogg (2002) list no records of Luticola binodis (or synonyms) with whom this species is often confused.

LM observations:— ( Figs 21–32 ): The valves are linear with parallel margins showing a clear single constriction in the middle. The valve apices are broadly rounded and capitate. Valve dimensions (n=14): length 16.5–22.0 µm, width 5.7–7.3 µm (at the constriction) and max. 7.0– 8.7 µm (widest part of the valve). The axial area is very narrow, linear and weakly widening towards the central area. The central area is expanded forming an almost elliptical ( Fig. 30 ) to bow-tie shaped stauros ( Figs 21, 26, 32 ), bordered on both sides by a single row of areolae. One rounded isolated pore is present in the central area, located almost halfway between the valve center and the valve margin and not associated with a stria. The raphe is almost straight with barely visible proximal raphe endings that are first weakly deflected away from the isolated pore and at the end hooked towards the pore-bearing valve side ( Figs 21, 31 ). The distal fissures are hooked to the same direction ( Figs 21, 26 ). The striae are radiate throughout the entire valve, 15–19 in 10 µm.

SEM observations:— ( Figs 33–34 ): Externally ( Fig. 33 ), the striae are composed of 2–3(4) transapically elongated areolae becoming larger near the valve margins and smaller and more rounded towards the poles. The external proximal raphe endings are weakly but continuously deflected opposite to the isolated pore-bearing side, then abruptly shortly hooked towards the isolated pore. The distal fissures are abruptly shortly hooked to the same direction. The observations of the valve interior were only made on a single valve from the Deception Island population ( Fig. 34 ). Internally, the central nodule is thickened. The central raphe endings are straight with the distal raphe endings terminating onto small helictoglossae. The areolae are covered by hymenes, forming a continuous strip along the striae. The internal isolated pore opening is covered by a c-shaped silica flap.

Similar species:— Luticola bogaertsiana was earlier reported as L. binodis by Van de Vijver et al. (2011). Levkov et al. (2013) already doubted that the maritime Antarctic species depicted in Van de Vijver et al. (2011, figs 46–48) would be conspecific with L. binodis s.s. Luticola binodis s.s., according to Levkov et al. (2013: 77) has a finer striation pattern as well as different raphe endings ( Table 2). The proximal raphe endings in L. binodis are clearly bent opposite the pore-bearing side whereas in L. bogaertsiana they are abruptly shortly hooked to the pore-side. The distal raphe fissures in L. bogaertsiana differ also, being abruptly and shortly hooked, whereas the distal raphe fissures in L. binodis are elongated and strongly hooked. Of all known Antarctic Luticola taxa only L. adelae Van de Vijver & Zidarova in Van de Vijver et al. (2011: 148) and L. tomsui Kopalová in Kopalová et al. (2011: 56) can be confused with L. bogaertsiana . Luticola adelae has slightly smaller valve dimensions ( Table 2). The axial area in L. adelae is clearly widening towards the central area whereas the axial area in L. bogaertsiana is narrow, linear and only weakly widening near the central area. The raphe endings in L. adelae are weakly deflected, whereas L. binodis has hooked raphe endings ( Table 2). Luticola tomsui differs in having a broad, lanceolate axial area and completely different raphe structure with proximal raphe endings turned away from the pore-bearing side and short, weakly deflected distal raphe fissures ( Table 2). Other Luticola taxa with biundulate margins that share similar features with L. bogaertsiana include L. binodeformis Levkov, Metzeltin & Pavlov in Levkov et al. (2013: 76) and Luticola mollis Rumrich & Lange- Bertalot in Rumrich et al. (2000: 149). Luticola binodeformis is smaller, with a higher number of striae ( Table 2). The proximal raphe endings are only weakly bent opposite the pore-bearing side and not abruptly hooked toward the isolated pore as in L. bogaertsiana . Luticola mollis has a broad axial area, widening towards the central area, as well as completely different raphe endings compared to L. bogaertsiana ( Table 2).

Figures

FIGURES 21–34. Luticola bogaertsiana Zidarova, Levkov & Van de Vijver, sp. nov. Light (LM) and scanning electron microscope (SEM) micrographs: Figs 21, 22–28. LM of 8 valves from the type population, King George Island, sample KGI12 (scale bars = 10 µm). Figs 29–32. LM of 4 valves from a Deception Island population, sample D37 (scale bars = 10 µm). Fig. 33. SEM external view of a valve from the type population, King George Island, sample KGI12 (scale bar = 5 µm). Fig. 34. SEM internal view of a valve from a Deception Island population, sample D37 (scale bar = 5 µm).