Staurosirella neorhomboides Van de Vijver, Kusber & Jüttner, 2024

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 neorhomboides Van de Vijver, Kusber & Jüttner sp. nov.

Fig. 7

Type locality.

Killen Burn, Highland, Scotland, UK.

Holotype.

BR- 4827 ( Meise Botanic Garden , Belgium), slide made from original Killen Burn material. Figure 7 G illustrates the holotype .

Isotype.

Slide 435 ( University of Antwerp , Belgium ).

Analysed material.

UNITED KINGDOM – Scotland • Killen Burn , Highland; slide BR- 4827; BR .

Registration.

http://phycobank.org/103341

LM description.

Frustules rectangular in girdle view, solitary (Fig. 7 A ). Valves weakly heteropolar with slightly broader headpoles and more acute footpoles, rhombic-lanceolate in larger valves, becoming more strictly lanceolate to even elliptical in smaller specimens. Apices not protracted in smaller valves, cuneately to broadly rounded, elongated in longer specimens. Valve dimensions (n = 60): length 5–20 µm, width 3.5–7.0 µm. Sternum variable, moderately broad, lanceolate, slightly widened near the centre to very narrow, linear. Striae narrower than the virgae, weakly radiate throughout the entire valve, 9–10 in 10 µm. Areolae not discernible in LM. Figure 7 A – AG.

SEM description.

Sternum and virgae externally raised above the striae. Weakly raised parallel ridges present on the virgae. Single or double, irregularly shaped spines present on the virgae, with a large number of small granules present between the spines on virgae and vimines. Striae narrower than the virgae, composed of linear, slit-like areolae, separated by thin vimines. Areolae diminishing in length near the sternum. Both apices not depressed. Apical pore fields present on both apices, on the footpole larger than on the headpole. On the footpole, pore field composed of at least 7 long rows of small, rounded pores, covered by small, but distinct, silica plates. Valvocopula very large, plain, with distinct fimbriae. Internal areola occlusions formed by finely branched volae. Figure 7 AH – AK.

Etymology.

The specific epithet refers to Staurosirella rhomboides (now considered a synonym of S. leptostauron ), the name that was used in the past to identify this species.

Associated diatom flora.

The sample from Killen Burn is dominated by species of Achnanthidium , Navicula lanceolata (C. Agardh) Ehrenb. , N. tripunctata , Planothidium reichardtii Lange-Bert. & Werum, and Tabellaria flocculosa (Roth) Kütz. with Cocconeis pseudothumensis , Frustulia vulgaris (Thwaites) De Toni , Gomphonema exilissimum (Grunow) Lange-Bert. & E. Reichardt , Navicula gregaria Donkin , Planothidium lanceolatum (Bréb.) Lange-Bert. , and Reimeria sinuata (W. Greg.) Kociolek & Stoermer showing lower abundances. According to Lange-Bertalot et al. (2017) and Werum and Lange-Bertalot (2004), this community indicates alkaline, higher nutrient conditions.

Figures

Figure 7. Staurosirella neorhomboides Van de Vijver & Jüttner sp. nov., LM and SEM micrographs taken from the type material (BR- 4827, Killen Burn, United Kingdom). A. LM picture of a frustule in girdle view. B – AG. LM pictures of valves in valve face view in decreasing length. AH – AJ. SEM external view of several valves, clearly showing the irregular spines and papillae on the valve margins. AK. SEM internal view of a complete valve. AL. SEM view of the broad valvocopula with the fimbriate extensions. Scale bar = 10 µm (A – AI, AK – AL), 1 µm (AJ).