Staurophora columbiana Bahls, 2013

Bahls, Loren, 2013, New diatoms (Bacillariophyta) from western North America, Phytotaxa 82 (1), pp. 7-28 : 8-10

Staurophora columbiana Bahls , sp. nov. ( Figs 1–6 )

Synonym: — Navicula sp. 6 PISCES Cumming et al. (1995: 38, pl. 29, figs 1–10; pl. 30, figs 1–6, 11–15).

Valves linear-lanceolate to elliptic-lanceolate with subrostrate apices. Valves strongly arched in transapical axis; valve face and mantle indistinguishable. Valve length 35–54 µm; valve width 7.9–12.7 µm. Axial area very narrow. Central area small and irregular; transverse fascia lacking. Raphe filiform with straight and slightly expanded proximal ends. Terminal raphe fissures hooked in the same direction. Striae finely punctate, weakly radiate at valve center to parallel or slightly convergent at apices, 15–20 in 10 µm. Striae irregularly shortened and more widely spaced near valve center. Areolae difficult to resolve in LM. Janus valves present with large rounded central area, more distant proximal raphe ends, and more irregularly spaced striae.

Holotype: — USA, Montana: Chouteau County, Kingsbury Lake , 47.5583 o N, 110.3428 o W, elev. 970 m, coll. R. Apfelbeck, 21 June 1994. MDC sample 145401; MDC slide P3-17-4 ( Figs 1, 2, 3, 6 ) (circled holotype specimen in Fig. 1 ). MONTU!

Isotype: — ANSP GC 65174.

Paratypes: — USA, Montana: Stillwater County, Hailstone National Wildlife Refuge , 46.0066 o N, 109.1810 o W, elev. 1220 m, coll. R. Apfelbeck, 26 April 1993. MDC sample 123701; MDC slide P3-8-5 ( Figs 4, 5 ). MONTU !— USA, Montana: Stillwater County, Big Lake , 45.8839 o N, 109.0513 o W, elev. 1200 m, coll. R. Apfelbeck, 6 April 1994. MDC sample 142901; MDC slide P3-15-19. MONTU !

Etymology:— Staurophora columbiana is named for the Canadian province of British Columbia, where it was first reported.

Observations: — Cumming et al. (1995), noted two forms of this taxon: form 1 with a larger, circular central area, more variable striae spacing, and more widely spaced proximal raphe ends (pl. 29, figs 1–5); and form 2, the typical form (pl. 29, figs 6–10; pl. 30, figs 1–6, 11–15). Examination of Montana specimens shows that form 1 represents occasional janus valves ( Fig. 4 ) opposite the more typical valves ( Fig. 5 ). Staurophora columbiana may be distinguished from other Staurophora species by the size and shape of its valves and by its very small central area. The highly arched valves, finely punctate striae, and saline water habitats (see below) are all characteristics of Staurophora species.

Distribution and Ecology: — Staurophora columbiana has been collected from 11 shallow hypersaline lakes: eight in southern British Columbia ( Cumming et al. 1995) and three on the Northwestern Great Plains in central Montana (holotype, paratypes). The British Columbia lakes have a salinity range of 40.83–248.31 g / L. The pH of all three Montana lakes measured a constant 9.20 and specific conductance ranged from 44100 to 67800 µS/cm.

Figures

FIGURES 1–12: Staurophora columbiana, Staurophora soodensis. Figs 1–6: Staurophora columbiana. Figs 1, 2, 3, 6: Kingsbury Lake, Chouteau County, Montana (type locality). Fig. 1: Holotype specimen. Figs 4, 5: Hailstone National Wildlife Refuge, Stillwater County, Montana. Fig. 4: Janus valve. Figs 7–12: Staurophora soodensis from White Lake, Sheridan County, Montana. Fig. 9: Girdle view. Scale bars: 10 µm.