Luticola doliiformis Kopalová & Van de Vijver, 2011

Kopalová, Kateŕina, Nedbalová, Linda, Haan, Myriam De & Vijver, Bart Van De, 2011, Description of five new species of the diatom genus Luticola (Bacillariophyta, Diadesmidaceae) found in lakes of James Ross Island (Maritime Antarctic Region), Phytotaxa 27, pp. 44-60 : 49-50

Luticola doliiformis Kopalová & Van de Vijver , sp. nov. ( Figs 14–28 )

Valvae lanceolatae marginibus convexis, apicibusque capitatis. Longitudo 17–22 µm, latitudo 7–8 µm. Area axialis lata, lanceolata, clare dilatata in aream centralem, leviterque dilatata in apices. Area centralis formans staurum rectangularem, marginatum serie una areolarum rotundatatrum. Stigma solitaria rotundata prope marginem valvae adest. Raphe filiformis, clare curvata, terminationibus proximalibus unilateraliter deflexis, fissurisque distalibus curtis, rectis. Striae transapicales radiatae in centro valvae, convergentes ad apices, 18–20 in 10 µm. Areolae parvae, semper rotundae, 2-3 per striam.

Type: — ANTARCTICA. James Ross Island , Ulu Peninsula, Lachman Crags, sample D07, leg. L. Nedbalová, coll. date 27/01/2008, slide no. BR-4250 (holotype BR, Fig. 20 is the encircled holotype specimen), slide PLP-195 (isotype University of Antwerp, Belgium), BRM-ZU8/07 (isotype BRM) .

Valves lanceolate with convex margins and capitate apices ( Figs 14–24 ). Valve length 17–22 µm, valve width 7–8 µm (n=15). Axial area broad, lanceolate, clearly widening towards central area, only slightly widening towards apices ( Fig. 25 ). Central area forming a broad, rectangular stauros, bordered by one series of small, rounded areolae ( Fig. 27 ). One small, solitary, rounded stigma present, close to valve margin ( Fig. 27 ). External raphe branches clearly curved, with weakly unilaterally deflected, simple proximal endings away from stigma ( Fig. 27 ). Distal raphe fissures very short, straight ( Fig. 28 ). Transapical striae radiate near valve centre becoming convergent towards apices, 18–20 in 10 µm ( Fig. 25 ). Striae composed of 2-3 small, always rounded areolae ( Fig. 25 ). Internal structure hardly visible since only one valve was found ( Fig. 26 ). Clearly developed stauros present. Detail of internal stigma opening obscured by debris. Proximal raphe endings terminating on edge of stauros.

Habitat, Ecology and Distribution:— Luticola doliiformis was found in small cracks on wet soil on the table mountain Lachman Crags close to the glacier front. The sample was dominated by Luticola cohnii , Hantzschia amphioxys ( Ehrenberg 1843: 413) Grunow (in Cleve & Grunow 1880: 103) and several unidentified species of Diadesmis .

Etymology: — This specific epithet doliiformis refers to its close resemblance to L. dolia (- formis: Latin for ‘resembling’).

Observations: — The James Ross Island (JRI) specimen of Luticola doliiformis bears a strong resemblance to L. dolia , a taxon described from the McMurdo Dry Valleys on the Antarctic Continent ( Esposito et al. 2008). The valve dimensions do not permit discrimination between the two taxa but there are other important differences. Unfortunately, in the original description of Esposito et al. (2008), the ultrastructure of the valves and girdle could not be examined as specimens were rare in the samples. Therefore, isotype material (INSTAAR Collection slide 532, isotype slide for Luticola dolia Spaulding & Esposito, Esposito et al. 2008: 1385 ) was re-examined using SEM and two valves were found showing some of the morphological features enabling separation between L. dolia and L. doliiformis ( Figs 29–34 ). Based on the description in Esposito et al. (2008) and our observations of the isotype material, several differences can be noted. The distal raphe fissures in the JRI population are very short contrary to L. dolia where slightly elongated fissures were noted ( Fig. 33 ). The valve apices in L. dolia are usually much narrower than in L. doliiformis that have normally broadly rounded, enlarged apices ( Figs 29–31 ). The shape and size of the areolae also differs with transapically elongated, larger areolae in L. dolia , whereas L. doliiformis has small, always rounded areolae ( Figs 32, 33 ). Moreover, the number of striae in 10 µm is higher in the JRI population contrary to that stated in the original description (18–20 vs 14–18). Although the external stigma opening could not be observed in the isotype material, it is clear that, based on the LM and the internal SEM views of L. dolia ( Fig. 34 ), the stigma opening is positioned more to the valve middle whereas in L. doliiformis , the stigma opening is closer to the valve margin ( Fig. 25 ). Based on these differences, separation of these taxa can be made.

Figures

FIGURES 14–28. Luticola doliiformis Kopalová & Van de Vijver sp. nov. Light (LM) and scanning electron micrographs (SEM). Specimens from James Ross Island. Figs 14–24. LM of size diminution series (Fig. 20 is the holotype). Fig. 25. SEM of external valve view. Fig. 26. SEM of Internal valve view. Fig. 27. SEM of external detail of central area Fig. 28. SEM of external detail of raphe endings. LM scale bar = 10 µm. SEM scale bars = 10 µm except for Figs 27 & 28, where scale bars = 1 µm.

FIGURES 29–34. Luticola dolia Eposito & Spaulding. Light (LM) and scanning electron micrographs (SEM). Specimens from isotype slide INSTAAR 532. Figs 29–31. LM images. Fig. 32. SEM of external valve view. Fig. 33. SEM of external detail of raphe endings. Fig. 34. SEM of Internal valve view. LM scale bar = 10 µm. SEM scale bars = 10 µm except for Figs 33, where scale bars = 1 µm.