Neidium undulatum Bahls, 2013

Bahls, Loren, 2013, New diatoms (Bacillariophyta) from western North America, Phytotaxa 82 (1), pp. 7-28 : 18-19

Neidium undulatum Bahls , stat. nov. ( Figs 66–68 )

Basionym: — Neidium kozlowi var. undulata Stoermer (1963 : p. 6, text fig. 1).

Type:— USA, Iowa: Dickinson County, West Lake Okoboji , coll. E.F. Stoermer, 26 June 1959, holotype slide ANSP GC8299 a.

Reported as: — Neidium kozlowii ( Krammer & Lange-Bertalot 1986: 276, fig. 102: 12)

Vouchers: — USA, Montana: Madison County, Grassy (Axolotl) Lake , 45.2422 o N, 111.8836 o W, elev. 2190 m, coll. L. Bahls, 29 September 2011. MDC sample 490701, MDC slides 41-5 ( Figs 66–68 ), 125-68. MONTU !

Observations:— Stoermer (1963) described this taxon as 98 µm long by 24 µm wide with 10–12 striae in 10 µm. Specimens recently collected from Grassy Lake in Montana ( Figs 66–68 ) are 82–110 µm long and 23–26 µm wide with 11–12 striae in 10 µm. This species differs from Neidium kozlowii Mereschkowsky (1906: 16 , fig. 5) by having more rounded (less truncate) apices and a wider axial area with a longitudinal row of depressions on the external valve surface along one side of the raphe. There are also obvious scattered depressions along the margins of the central area, which are not evident in Mereschkowky’s original drawing of N. kozlowii . Valve margins of N. undulatum are somewhat undulate in Stoermer’s illustration, less pronounced in the Montana specimens and not at all evident in the drawing of N. kozlowii . Krammer & Lange-Bertalot (1986) published an image (fig. 102: 12) of what appears to be N. undulatum from Zürichsee and called it N. kozlowi . Metzeltin et al. (2009) pictured a similar taxon (pl. 102, fig. 1) from Mongolia and called it Neidium spec. cf. kozlowii . However, the Mongolian taxon has very blunt ends, an elliptic-lanceolate valve shape, and distinctly undulating valve margins. Another taxon illustrated on the same plate (figs 2–7) more closely matches Mereschkowsky’s illustration of N. kozlowii except that it has 14 striae in 10 µm, which is too high for N. kozlowii (10–12 in 10 µm). In Mereschkowsky’s original drawing of N. kozlowii , the proximal raphe ends are straight, not bent, and the axial area is very narrow (see also Hustedt 1930: 247, fig. 387). Given the straight proximal raphe ends, one might suppose that Mereshkowsky made his drawing from an internal valve view. However the axial area would also be narrow on the outside and it is unlikely that he overlooked the conspicuous depressions on the external valve surface. The type for N. kozlowii and original material from Tibet are unavailable for study. See also observations for N. bobmarshallensis .

Ecology: —Grassy (Axolotl) Lake in the Gravelly Range of southwestern Montana has a pH of 9.73 and specific conductance of 177 µS/cm.

Family Naviculaceae Kützing 1844: 88

Genus Navicula J.B.M. Bory de St. -Vincent 1822: 128

Figures

FIGURES 52–68: Neidium inconstans, Neidium bobmarshallensis, Neidium fogedii, Neidium undulatum. Figs 52–55: Neidium inconstans from Indian Springs Pond, Waterton Lakes National Park, Alberta. Figs 56–59: Neidium bobmarshallensis. Fig. 56: Logging Lake, Glacier National Park, Montana. Figs 57, 59: Dean lake, Bob Marshall Wilderness, Montana (type locality). Fig. 57: Holotype specimen. Fig. 58: Upper Trilobite Lake, Bob Marshall Wilderness, Montana. Figs 60–65: Neidium fogedii from Mexican Cut Upper Pond No. 56, Gunnison County, Colorado. Figs 66–68: Neidium undulatum from Grassy (Axolotl) Lake, Madison County, Montana. Scale bars: 10 µm.