Pinnularia subcarteri, Zidarova & Kopalová & Vijver, 2012

Zidarova, Ralitsa, Kopalová, Kateŕina & Vijver, Bart Van De, 2012, The genus Pinnularia (Bacillariophyta) excluding the section Distantes on Livingston Island (South Shetland Islands) with the description of twelve new taxa, Phytotaxa 44, pp. 11-37 : 15

Pinnularia subcarteri sp. nov. ( Figs 20–28 )

Valvae anguste lanceolatae, margines leviter convexae in media parte valvae, graduatim decrescentes in apices capitatos, anguste rotundatos. Longitudo 17–30 µm, latitudo 3.0– 4.5 µm. Area axialis angustissima, linearis, dilatans in aream centralem. Area centralis formans fasciam latam, cuneiformem. Raphe filiformis, ramis rectis, terminationibus raphis proximalibus unilateraliter leviter deflexis cum poris guttiformibus expansis, relative distantibus inter se. Terminationes raphis distales paene non discernandae in LM, falcatae. Striae fortiter radiatae in media parte valvae, abrupte convergentes ad apices, 12–14 in 10 µm. Lineae speciosae longitudinales nullae.

Valves narrowly lanceolate, slightly convex in the middle and gradually narrowing towards the capitate, narrowly rounded valve apices. Valve dimensions (n=19): length 17–30 µm, width 3.0– 4.5 µm. Axial area very narrow, widening towards the central area. Central area forming a broad, wedge-shaped fascia. Raphe filiform, straight with only slightly deflected central endings terminating in clearly droplike expanded, relatively distant, central pores. Terminal fissures almost indistinct in LM, probably sickle-shaped ( Figs 22– 23 ). Striae strongly radiate in the middle, becoming abruptly strongly convergent at the apices, 12–14 in 10 µm. Longitudinal lines absent.

Type:— Byers Peninsula, Livingston Island , South Shetland Islands , sample BY068, leg. B. Van de Vijver, coll. date 18/01/2009, slide no. BR-4252 (holotype BR), slide PLP-197 (isotype University of Antwerp, Belgium), slide ZU8/28 (isotype BRM) .

Habitat:— Pinnularia subcarteri is a rare species on Livingston Island and was found in a few samples. The type population was sampled from the sandy bottom of a small pool near the southern beaches, with an almost circumneutral pH (7.2) and a low specific conductance (<100 µS/cm) value. The species was also observed in the surrounding moss vegetation. On Hurd Peninsula, the species was occasionally observed mostly on moss vegetations surrounding small water basins and in a small brook, flowing out from a shallow melt-water pool, with low specific conductance values (58 µS/cm).

Etymology:— The specific epithet refers to the close resemblance to P. carteri Krammer (2000: 48) .

Observations:— Pinnularia subcarteri shows some similarities to P. diversa Østrup (1901: 273) and P. carteri . Both P. diversa and its variety subcapitata Krammer & Lange-Bertalot (in Krammer 2000: 46) differ, however, in having a larger width (5–6 µm vs 3.0–4.5) and a lower stria density (10–12 vs. 12–14 in 10 µm). Pinnularia carteri is also distinctly wider (4.8–5.2 µm) with a coarser striation pattern (10–11 striae in 10 µm) and has large central pores that are close together, in contrast to P. subcarteri , which has distant central pores. Rumrich et al. (2000, plate 144, figs 17–20) illustrate several valves identified as P. martinii Krasske (1939: 394) that are probably conspecific with P. subcarteri . However, comparison with type material of P. martinii (Van de Vijver et al., unpubl. res.) indicated that the illustrated valves in Rumrich et al. (2000) certainly do not belong to P. martinii sensu Krasske. The latter is characterized by more convex, less tumid valve margins, an axial area that is clearly widened towards the central area and a much larger central area (Lange-Bertalot et al. 1996, Van de Vijver et al., unpubl. res.).

Figures

FIGURES 1–47. Pinnularia pseudolaucensis sp. nov., Pinnularia subcarteri sp. nov., Pinnularia subaltiplanensis, Pinnularia strictissima and Pinnularia sp1 from Livingston Island. Figs 1–19. LM of P. pseudolaucensis sp. nov.. Figs 20–28. LM of P. subcarteri sp. nov. Figs 29–35. LM of P. subaltiplanensis. Figs 36–43. LM of P. strictissima. Figs 44– 47. LM of Pinnularia sp1. Scale bar = 10 µm.