Achnanthidium sieminskae Witkowski, Kulikowskiy & Riaux-Gob.

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 : 153-154

Achnanthidium sieminskae Witkowski, Kulikowskiy & Riaux-Gob.

( Figs 5-8 )

Witkowski et al. in Wołowski et al., Current Advances in Algal Taxonomy and its Applications: Phylogenetic, Ecological and Applied Perspective: 65, fig. 6 ( Witkowski et al. 2012).

DESCRIPTION

LM ( Figs 5 A-BN; 7A-BQ)

Frustules moderately arched, convex RL, concave RV, poles slightly to moderately recurved.Valves linear to linear-lanceolate. Valve margins slightly or moderately curved, tapering towards subcapitate or capitate poles.Valves occasionally slightly asymmetrical with one valve margin almost straight or less curved than the other (more commonly observed in United Kingdom populations). Valve dimensions:length 11.0-26.0 µm (populations United Kingdom, n = 20), 10.0-19.5 µm (populations Germany, Austria, n=15), width at valve centre 2.0-3.0 µm. On RV, central area small rounded or indistinct, bordered by 1-2 slightly shortened, more widely spaced striae on each side, central striae can be absent. Raphe filiform, straight, central pores slightly widened, terminating close to margin of central area. Central area on RL indistinct or narrow rhombic. Axial area narrow linear on both valves, slightly widening towards valve centre. Striae weakly radiate in valve centre, becoming more strongly radiate towards poles on both valves, RV 32-34 in 10 µm, RL 30-34 in 10 µm (populations United Kingdom), 30-32 in 10 µm (RV and RL, populations Germany, Austria).

SEM ( Figs 6 A-H; 8A-F)

Raphe located on slightly raised sternum, terminal fissures straight terminating at valve/mantle junction. Internally, central raphe endings shortly deflected to opposite sides, terminal raphe endings form small helictoglossae. Striae composed of 2-4 (RV) and 3-5 (RL) areolae. Areolae round, oval or slitlike, those adjacent to valve margin often slit-like. A row of transapically elongated areolae on the mantle separated from the areolae on the valve face by a hyaline area.

Figures

FIG. 5. — Achnanthidium sieminskae Witkowski,Kulikowskiy & Riaux-Gob.: A-I, specimens from Loch Morlich,Scotland;J-P, specimens from River Spey,Scotland; Q-W, specimens from River Feshie,Scotland; X-AR, specimens from unnamed stream west of Arnisdale,Highland,Scotland;AS-AX, specimens from River Ehen, England; AY-BN, specimens from Llyn y Fan Fawr, Wales; B-P, R-W, Y-BN, LM views of valves; A, Q, X, LM views of frustules in girdle view. Scale bar: 10 µm.

FIG. 6. — Achnanthidium sieminskae Witkowski, Kulikowskiy & Riaux-Gob.: A, E, specimens from River Spey, Scotland; B-D, F-H, specimens from River Feshi, Scotland; A, B, SEM external views of raphe valve; C, SEM internal view of raphe valve; D, E, SEM external views of rapheless valves; F, SEM internal view of raphe valve; G, SEM external view of rapheless valve and mantle; H, external view of frustule in girdle view. Scale bars: A-D, F-H, 5 µm; E, 2 µm.

FIG. 7. — Achnanthidium sieminskae Witkowski, Kulikowskiy & Riaux-Gob.: A-W, specimens from Brunnsee, Germany; X-AT, specimens from Plansee, Austria; AU-BC, specimens from Fischkaltersee; BD-BI, specimens from Ammelsheiner See; BJ-BM, specimens from Harthsee; BN-BQ, specimens from Speicher Dreiweibern; B-BC, BE-BI, BK-BM, BO-BQ, LM views of valves; A, BD, BJ, BN, LM views of frustules in girdle view. Scale bar: 10 µm.

FIG. 8. — Achnanthidium sieminskae Witkowski, Kulikowskiy & Riaux-Gob., specimens from Brunnsee, Germany: A, SEM external view of raphe valve; B, SEM external view of rapheless valve, internal view of raphe valve; C, SEM external view of rapheless valve; D, SEM internal view of rapheless valve; E, SEM external view of rapheless valve at centre; F, SEM external view of rapheless valve at pole. Scale bars: A-D, 5 µm; E, F, 3 µm.