Staurosirella jonssoniana Van de Vijver & Iris Hansen, 2024

Van de Vijver, Bart, Peeters, Valérie, Hansen, Iris, Ballings, Petra & de Haan, Myriam, 2024, Five new species in the genus Staurosirella (Bacillariophyta) from European freshwater habitats, PhytoKeys 242, pp. 139-160 : 139-160

Staurosirella jonssoniana Van de Vijver & Iris Hansen sp. nov.

Fig. 5

Holotype.

BR- 4843 (Meise Botanic Garden, Belgium). Fig. 5 H represents the holotype .

Isotype.

Slide 445 (University of Antwerp, Belgium) .

Registration.

http://phycobank.org/104536.

Type locality.

Grenlækur, southern Iceland, sampling site at Græntorfa , 63 ° 43.96 ' N, 17 ° 58.07 ' W, coll. date 03 Jul. 2017, leg. Iris Hansen .

Description.

LM (Fig. 5 A – U ). Valves isopolar to weakly heteropolar, lanceolate with convex margins, and narrowly protracted, rostrate apices. Smallest valves almost elliptical (Fig. 5 T – U ). Valve dimensions (n = 25): length 6–15 µm, width 3.0–3.5 µm. Sternum narrow, linear. Striae alternating, almost parallel to very slightly radiate in the middle, more strongly radiate towards the apices, 12–13 in 10 µm. Areolae not discernible in LM. SEM (Fig. 5 V – Y ). External valve face weakly undulating with slightly raised virgae and striae sunken in ‘ punch hole-like’ depressions (Fig. 5 V – X ). Striae extending without interruption from valve face onto the mantle (Fig. 5 X ), gradually narrowing towards the sternum (Fig. 5 V – X ) giving the striae a lanceolate appearance. Striae uniseriate, composed of long, slit-like, linear areolae, running parallel to the apical axis (Fig. 5 V – X ). Vimines very thin, not raised. Marginal spines very obvious, one per virga, each located in a shallow, pit-like depression (Fig. 5 V – X ). Apical pore fields absent, replaced by one or two spines. Internally, striae distinctly sunken between the flat, doubly flared virgae and sternum (Fig. 5 Y ). Areolae occluded by irregularly shaped volae, extending from the longer inner side of each vimen (Fig. 5 Y ).

Etymology.

The new species honours our friend and colleague Gunnar Steinn Jónsson (Reykjavik, Iceland) in recognition of his important contributions to the diatom research in Iceland.

Distribution.

Staurosirella jonssoniana has so far only been found in Iceland.

Ecology and associated diatom flora.

The type locality, Grenlækur, is a small spring-fed stream in southern Iceland. The stream has a slightly alkaline pH (7.8), a rather low conductivity (156 µS / cm), low nitrate (0.02 mg / l) and phosphate (0.97 mg / l), and moderate sulphate (37.8 mg / l) levels. The diatom flora in the sample is quite diverse and dominated by a large number of species with Staurosirella jonssoniana only being relatively rare in the sample. The dominant species include Fragilaria landnama Van de Vijver & Iris Hansen , F. sandellii Van de Vijver & Jarlman , Staurosira cf. sviridae Kulikovskiy et al. , Planothidium lanceolatum (Brébisson) Lange-Bertalot , different Cocconeis species (mainly C. euglypta Ehrenberg ), Surirella brebissonii Krammer & Lange-Bertalot , Gomphonema pumilum var. rigidum E. Reichardt & Lange-Bertalot , although none of them reaches more than 10 % of all counted valves. Rarer species include Odontidium mesodon (Ehrenberg) Kützing , Navicula radiosa Kützing , N. slesvicensis Grunow and Amphora ovalis (Kützing) Kützing. The flora points to colder, fast-flowing, meso- to eutrophic, alkaline conditions ( Lange-Bertalot et al. 2017; Van de Vijver et al. 2023).

Figures

Figure 5. Staurosirella jonssoniana Van de Vijver & Iris Hansen, sp. nov., LM and SEM micrographs taken from the holotype material (BR- 4843, Grenlækur, southern Iceland) A – U LM pictures of valves in valve face view in decreasing length V – X SEM external view of three complete valves with focus on the spines located in pit-like depressions. Note the absence of apical porefields Y SEM internal view of a complete valve. Scale bars: 10 µm (A – W, Y); 1 µm (X).