Achnanthidium neomicrocephalum Lange-Bert. & F.Staab

Jüttner, Ingrid, Hamilton, Paul B., Wetzel, Carlos E., De, Bart Van, Vijver, King, Lydia, Kelly, Martyn G., Williams, David M. & Ector, Luc, 2022, A study of the morphology and distribution of four Achnanthidium Kütz. species (Bacillariophyta), implications for ecological status assessment, and description of two new European species, Cryptogamie, Algologie 20 (10), pp. 147-176 : 155

Achnanthidium neomicrocephalum Lange-Bert. & F.Staab

( Figs 9-13 )

Süsswasserflora von Mitteleuropa, Bacillariophyceae. 4. Teil Achnanthaceae : 431, pl. 89, figs 1-13 (Krammer & Lange-Bertalot 2004).

DESCRIPTION

LM ( Fig. 9 A-DZ)

Frustules slightly arched, with convex RL, concave RV.Valves linear-lanceolate. Margins slightly tapering towards small protracted, capitate poles. Valve margins slightly inflated in valve centre, sometimes more strongly on one side. Valve dimensions (n = 31): length 12-30.5 µm, width at valve centre 2-2.5 µm. On RV, central area small rounded, bordered by 1-2 slightly shortened, more widely spaced striae on each side, or small transverse fascia. Raphe filiform, straight, central pores terminating close to margin of central area. Central area on rapheless valve indistinct. Axial area narrow, linear on both valves, slightly widening towards valve centre. Striae radiate throughout on both valves, 30-32 in 10 µm (RV and RL).

SEM ( Figs 10 A-H; 11A-F; 12A-H; 13A-D)

Raphe located on slightly raised sternum, terminal raphe fissures straight terminating at valve/mantle junction. Internally, central raphe endings shortly deflected to opposite sides. Striae composed of 2-3 areolae (RV and RL). Areolae round or oval adjacent to axial area, sometimes slit-like adjacent to valve margin. Row of transapically elongated areolae on mantle separated from areolae on valve face by hyaline area.

Figures

FIG. 9. — Achnanthidium neomicrocephalum Lange-Bert. & F.Staab: A-W, specimens from Lustsee, Germany; X-AD, specimens from Fischkaltersee, Germany; AE-AO, specimens from Loch Tarff, Scotland; AP-CH, specimens from Ullapool River, Scotland; CI-DP, specimens from Llyn y Fan Fawr, Wales; DQ-DZ, specimens from Petta Water, Shetland Islands, Scotland; A-DO, DR-DZ, LM views of valves; DP-DQ, LM views of frustules in girdle view. Scale bar: 10 µm.

FIG. 10. — Achnanthidium neomicrocephalum Lange-Bert. & F.Staab, specimens from Lustsee, Germany: A-H, SEM views of raphe valves; A-C, SEM external views of raphe valves; D, SEM internal view of raphe valve; E, SEM external view of valve centre; F, SEM external view of half of valve and pole; G, SEM internal view of valve centre; H, SEM internal view of valve pole. Scale bars: A, B, D, 5 µm; C, 10 µm; E-H, 1 µm.

FIG. 11. — Achnanthidium neomicrocephalum Lange-Bert. & F.Staab, specimens from Lustsee, Germany: A-F, SEM views of rapheless valves; A, SEM external view of valve; B, SEM internal view of valve; C, SEM external view of pole; D, SEM external view of valve centre; E, SEM internal view of valve centre; F, SEM internal view of pole. Scale bars: A, B, 5 µm; C-F, 1 µm.

FIG. 12. — Achnanthidium neomicrocephalum Lange-Bert. & F.Staab: A, C-F, specimens from Loch Tarff, Scotland; B, G, H, specimens from Llyn y Fan Fawr, Wales; A-H, SEM views of raphe valves; A-C, SEM external views of valves; D, internal view of valve; E, SEM external view of valve centre; F, SEM external view of valve pole; G, SEM internal view of valve centre; H, SEM internal view of valve pole. Scale bars: A-C, 5 µm; D, 3 µm; E-H, 1 µm.

FIG. 13. — Achnanthidium neomicrocephalum Lange-Bert. & F.Staab: A, specimen from Loch Tarff, Scotland; B-D, specimens from Llyn y Fan Fawr, Wales; A-D, SEM views of rapheless valves; A, B, SEM external views of valves; C, SEM external view of valve pole; D, SEM external view of valve centre. Scale bars: A, B, 5 µm; C, D, 2 µm.