Staurosirella leptostauron (Ehrenb.) D. M. Williams & Round, 1854

Van de Vijver, Bart, Kusber, Wolf-Henning, Jüttner, Ingrid, Schuster, Tanja M. & Williams, David M., 2024, Revision of the Staurosirella leptostauron complex (Staurosiraceae, Bacillariophyta) in Europe with the description of three new species, Plant Ecology and Evolution 157 (2), pp. 174-201 : 174-201

Staurosirella leptostauron (Ehrenb.) D. M. Williams & Round

Fig. 4 , Supplementary materials 2 K – Z, 3 C – F, 5, , 7

Biblarium leptostauron Ehrenb. (basionym) ( Ehrenberg 1854: 8, plate VII, figs 35–36)

Fragilaria harrisonii var. β rhomboides Grunow ( Grunow 1862: 368)

Fragilaria leptostauron (Ehrenb.) Hust. ( Hustedt 1931: 153)

Fragilaria leptostauron var. rhomboides (Grunow) Hust. ( Hustedt 1931: 154)

Staurosirella rhomboides (Grunow) E. Morales & Manoylov ( Morales et al. 2010 a: 43)

Staurosira leptostauron (Ehrenb.) Kulikovskiy & Genkal ( Kulikovskiy et al. 2011: 363)

Type locality.

Germany, Polierschiefer bei Cassel, Ehrenberg BHUPM drawing sheet 2347, BHUPM sample 2726.

Epitype locality.

Moosach near Munich, Grunow Moosach sample s. n., material conserved at BR! and W!.

Lectotype.

BHUPM drawing sheet 2347 “ Cassel. ” (designated here by Kusber & Van de Vijver ), valve original annotated in black colour “ 10. δ. bl. ”, subsequently annotated in red colour “ 31 ” [icon!], the image represents a specimen on Mica BHUPM 420310 δ r that could not be found during the recent studies at BHUPM. The lectotype here selected was published in Ehrenberg (1854), see our Fig. 2 A “ 36 ”.

Epitype.

BR- 4819 (designated here by Van de Vijver for the above lectotype), slide made from the Grunow Moosach sample s. n. Figure 4 C illustrates the epitype .

Isoepitype.

W 0164841 (designated here by Schuster & Van de Vijver for the above lectotype), raw Grunow Moosach material s. n. at W .

Registration for the typification.

http://phycobank.org/104203

Analysed material.

GERMANY • Polierschiefer bei Cassel , Ehrenberg sample 2726, [icon!] drawing sheet 2347 ; BHUPM • Moosach near München ; Grunow Moosach sample s. n., slide BR- 4819 ; BR • Moosach near München ; Kützing sample 921, slide BR- 4820 ; BR .

UNITED KINGDOM – England • Burnham, Norfolk ; William Smith sample; 1 Jan. 1854; leg. Mr. Brookes; slide BR- 4824 ; BR • Redesdale, Hermits Well ; Walker Arnott sample S 445; Aug. 1856; leg. R. K. Greville; slide BR- 4823 ; BR .

IRELAND • William County Clare ; Smith sample Lough Derg; 24 Jul. 1854; leg. W. Smith; slide BR- 4825 ; BR .

Description note.

As the search for S. leptostauron in Ehrenberg’s sample 2726 was not successful, the following morphological description is based on the epitype material from Moosach.

LM description.

Frustules in girdle view rectangular, impossible to get into focus entirely due to protruding central parts. Valves isopolar to weakly heteropolar with weakly narrower footpole (Fig. 4 B, F, L ), distinctly cruciform throughout its entire cell cycle. Apices elongated, narrow, acutely rounded. Central inflation on both margins, acutely rounded. Valve dimensions (n = 25): length 15–23 µm, width 10–16 µm. Sternum broad, distinctly lanceolate, widened near the valve centre, often showing irregular markings (see for instance Fig. 4 IK and N). Striae parallel to weakly radiate at the centre, becoming more radiate towards the apices, clearly wider than the virgae, ca 9 in 10 µm. Individual areolae only rarely discernible in LM. Figure 4 A – L .

SEM description.

Valve face not flat, showing clear topography with raised virgae and sternum and depressed striae. Distinct short, parallel ridges present on the virgae, in line with the vimines separating the linear areolae. In eroded valves, ridges less prominently present to even absent. Sternum often irregularly raised. Large, flattened, irregularly shaped marginal blunt spines placed on the virgae. Numerous, irregular, often very small granules present on the virgae between the spines and the vimines. Apical pore fields present on both apices, clearly different in size and shape, giving the valves an heteropolar appearance. Pore field at the footpole composed of more than 8 long rows of small, rounded to squarish pores. At the headpole, pore field smaller, with a maximum of 5–6 short rows of small pores. Observations of valve interior in the Moosach material showing typical finely branched volae (Fig. 4 N ). Valvocopula with well-developed fimbriae. Figure 4 M – P .

Associated diatom flora.

The Moosach population is quite diverse and dominated by taxa such as Achnanthidium exile (Kütz.) Heib. , Cocconeis pseudothumensis , Denticula kuetzingii Grunow , D. tenuis Kütz. , Ellerbeckia arenaria (Moore) Dorofeyuk & Kulikovskiy , Eunotia alkalibiontica Lange-Bert. , Grunowia tabellaria (Grunow) Rabenh. , Odontidium mesodon (Ehrenb.) Kütz. , Staurosirella neopinnata E. Morales et al. , S. leptostauron (Ehrenb.) D. M. Williams & Round , and various species of Delicata , Cymbella , and Gomphonema . This species composition is often found in oligo- to mesotrophic, calcium-bicarbonate enriched, alkaline conditions ( Lange-Bertalot et al. 2017). In the Smith sample s. n. from Lough Dern ( Scotland, United Kingdom), the dominant species include Encyonopsis cesatii (Rabenh.) Krammer , several smaller species of Encyonopsis and Cymbella , Denticula tenuis , and Cymatopleura solea (Bréb.) W. Sm. The Walker Arnott population from Redesdale, a valley in the western part of Northumberland, (northeast England, United Kingdom) presents a similar species composition with very high numbers of Brachysira neoexilis , Delicata delicatula , Denticula tenuis , Eucocconeis flexella (Kütz.) F. Meister , and Fragilaria cf. amphicephaloides . All analysed UK populations indicate alkaline, mesotrophic calcium-bicarbonate enriched lake conditions ( Lange-Bertalot et al. 2017).

Figures

Figure 2. Staurosirella crux (Ehrenb.) Van de Vijver & Kusber comb. nov., LM and SEM micrographs taken from the original Smith type material for Odontidium harrisonii (BR- 4685, Hull, United Kingdom). A. LM picture of a frustule in girdle view. B – M. LM pictures of valves in valve face view in decreasing length. N. SEM external view of a complete valve. O. SEM external detail of the footpole showing the large apical pore field. P. SEM external detail of part of the central area with the marginal spines, the large virgae and the vimines. Q. SEM internal view of a complete valve. Scale bar = 10 µm (A – N, Q), 1 µm (O – P).

Figure 4. Staurosirella leptostauron (Ehrenb.) D. M. Williams & Round, LM and SEM micrographs taken from Grunow’s Moosach sample (BR- 4819, Moosach, Germany). A. Published images in Ehrenberg (1854: figs 35–36) after original drawing from C. G. Ehrenberg in BHUPM 2347. B. LM picture of three connected frustules in girdle view. B – L. LM pictures of valves in valve face view in decreasing length. M. SEM external view of two connected frustules in girdle view. N. SEM view of the valvocopula connected to the girdle showing the fimbriate extensions. Scale bar = 10 µm.