Pinnularia perlanceolata Van de Vijver & Zidarova, 2011

Vijver, Bart Van De & Zidarova, Ralitsa, 2011, Five new taxa in the genus Pinnularia sectio Distantes (Bacillariophyta) from Livingston Island (South Shetland Islands), Phytotaxa 24, pp. 39-50 : 47

Pinnularia perlanceolata Van de Vijver & Zidarova , sp. nov. ( Figs 45–50 )

Valvae elliptico-lanceolatae marginibus calro convexis, apicibusque non-protractis, late rotundatis. Dimensiones (n=17): longitudo 23.8–35.5 µm, latitudo 10.6–12.8 µm. Area axialis moderate angusta, linearis, dilatans ad aream centralem. Area centralis parva ad moderate lata, rotundata ad rectangularis. Fascia abest. Raphe fere recta ad leviter curvata, terminationibus raphis proximalibus rectis ad unilateraliter leviter deflexis, poriformibus. Fissurae distales unciformes. Striae transapicales latae, distincte radiatae ad aream centralem, minus radiatae in apices, 5–6 in 10 µm.

Valves elliptic-lanceolate to rhombic-lanceolate with clearly convex valve margins and rather broadly rounded, non protracted but clearly narrowing apices. Valve dimensions (n=17): length 23.8–35.5 µm, width 10.6–12.8 µm. Axial area (moderately) narrow, linear, widening towards central area. Central area small to moderately large, rounded to rectangular, bordered by 1–2 short striae. Raphe almost straight to weakly curved, with straight to unilaterally slightly deflected proximal, pore-like endings ( Fig. 50 ). Distal fissures sickle-shaped. Transapical striae broad, distant, clearly radiate near central area, becoming slightly less radiate near apices, 5–6 in 10 µm. Longitudinal lines absent.

Type:— Byers Peninsula, Livingston Island , South Shetland Islands , sample BY67, leg. B. Van de Vijver, coll. date 18/01/2009, slide no. BR-4236 (holotype BR), slide PLP-186 (isotype University of Antwerp, Belgium), BRM-7/99 (isotype BRM) .

Habitat and Distribution:— Pinnularia perlanceolata has only been found on Livingston Island. It is a very rare species and so far only observed in one large (70 m ²), circumneutral (pH 7.3) shallow pool near the southern beaches of Byers Peninsula surrounded by fellfields and moss vegetations, growing into the water. The sediment of the pool was very fine and mainly composed of algal mats. This was the source of sample BY67.

Etymology:—the specific epithet refers to the similarity with P. borealis var. lanceolata .

Observations:— Pinnularia perlanceolata has similarities with both P. borealis var. lanceolata and var. undata (Table 1). Pinnularia borealis var. undata has more acutely rounded apices and is slightly larger, while the var. lanceolata non sensu Krammer has more lanceolate valves with more distant striae. Pinnularia borealis var. pseudolanceolata has a higher number of striae (6–8 vs. 5–6 in 10 µm in P. perlanceolata ) and narrower valves (up to 9.5 µm vs. 10.6–12.8 in P. perlanceolata ). [For further comment see P. quesadae sp. nov.]

Pinnularia borealis f. lanceolata may possible be the same taxon but it has less elliptic-lanceolate valves and a larger axial area. Boye-Petersen also described a f. ovalis ( Boye-Petersen 1928: 402) , which has valves with a clearly elliptic outline and broadly rounded, less tapering valve ends in contrast to P. perlanceolata that has valves that are more rhombic-lanceolate with narrowing apices. A similar situation applies for P. borealis var. elliptica Zanon (1938: 246) , described from Spitsbergen, which have valves with a clearly elliptical outline but with a less prominent larger width near the middle of the valve.

Figures

FIGURES 39–56. Pinnularia laterotundata sp. nov., Pinnularia perlanceolata sp. nov. and Pinnularia quesadae sp. nov. from Byers Peninsula. Figs 39–44. Pinnularia laterotundata sp. nov. Figs 39–44. LM of valves from specimens of type population. Figs 45–50. Pinnularia perlanceolata sp. nov. Figs 45–49. LM of valves from specimens of type population. Fig. 50. SEM of external view of entire valve. Figs 51–56. Pinnularia quesadae sp. nov. Figs 51–55. LM of valves from specimens of type population. Fig. 56. SEM of external view of entire valve. Scale bar = 10 µm, except Figs 50 & 56, scale bar = 5 µm.