Eunotia sphagnicola Van de Vijver, A.Mertens & Lange-Bertalot, 2022

Vijver, Bart Van De, Lange-Bertalot, Horst, Goeyers, Charlotte, Mertens, Adrienne, Schuster, Tanja M. & Ector, Luc, 2022, The identity of Eunotia paludosa Grunow 1862 (Eunotiaceae, Bacillariophyta), a revision, and the description of three new species of Eunotia Ehrenberg, Phytotaxa 545 (3), pp. 261-277 : 264-266

Eunotia sphagnicola Van de Vijver, A.Mertens & Lange-Bertalot , sp. nov. ( Figs 37–84 )

Type:— THE NETHERLANDS, Egelmeer , Veenendaal, sample D283, coll. date 05.IV.1978, leg. H. van Dam, holo-BR-4716! (Meise Botanic Garden, Belgium), iso- slide 404! (University of Antwerp, Belgium). The holotype is represented by Fig. 44 .

PhycoBank registration:—http://phycobank.org/103146

Synonym:— Eunotia paludosa Grunow sensu Alles et al. 1991 , Eunotia paludosa Grunow sensu Krammer & Lange-Bertalot 1991 .

To exclude from synonymy:— Eunotia paludosa Grunow 1862

LM ( Figs 37–81 ): Frustules in girdle view roughly rectangular, frustule width 4–7 µm with slightly concave margins ( Figs 37–39 ). Valves weakly arched with consistently more or less convex dorsal margins and variable ventral margins, ranging from almost straight in the shortest valves to moderately concave in medium-sized to longer specimens. Apices narrowly protracted, dorsally slightly or very slightly reflexed, sometimes simply broadly rounded. Valve dimensions (n=50): length 9.5–35.0 µm, width 2.0–2.5 µm, length-to-width ratio 5–13. Terminal raphe nodules close to the poles. Terminal raphe fissures comparatively rather short in the valve face, not attaining the middle, never closer to the dorsal side of valve poles but often difficult to discern in LM. Striae equidistant on the valve face, 21–23 in 10 µm. Areolae not discernible in LM.

SEM ( Figs 82–84 ): Striae uniseriate throughout, composed of small, rounded areolae, 48–50 in 10 µm ( Figs 82, 83 ). Mantle striae ventrally composed of up to 5 areolae near the valve middle, only 2 near the apices ( Fig. 82 ). Spines lacking ( Fig. 83 ). Externally, raphe branches curving from valve mantle rather shortly up onto the valve face surrounded by a comparatively small terminal area, distinctly distant from the dorsal sides of the valve poles ( Figs 82, 83 ). Single rimoportula present at one of both poles ( Fig. 84 , arrow), located close to the helictoglossa. Helictoglossa prominent at both poles ( Fig. 84 ). Girdle composed of several open, perforated bands ( Fig. 82 ).

Etymology:—The specific epithet ‘ sphagnicola ’ refers to the almost exclusive preference of the new species for Sphagnum -dominated habitats.

Distribution and ecology:—Due to severe damaging – or land use amelioration in an anthropogenic sense (pollution, draining, eutrophication) – ombrotrophic Sphagnum -bogs in Europe have been transformed into minerotrophic waters. As a consequence, Eunotia sphagnicola has become rare, although still abundant in places under disguise of the false name E. paludosa Grunow as shown here. In the past, E. sphagnicola was likewise mistaken for several other small-celled Eunotia taxa or viewed as a related infraspecific taxon. Its autecology (as E. paludosa ) was investigated in detail by Alles et al. (1991) and Krammer & Lange-Bertalot (1991). During a study of the diatom associations in the Italian part of the southwestern Alps, Cantonati et al. (2011) investigated the “false E. paludosa ” in mountain mires, shallow pools with acidic, low mineralization waters, and peat bogs. In this study, E. sphagnicola (as E. paludosa ) was almost exclusively found associated with Sphagnum spp. and a whole plethora of acidophilous and often acidobiontic diatoms, such as 18 different Eunotia species, among them E. paludosa Grunow (1862) s.s. in one locality, which was reported as E. fennica then. They also compared peat bogs and similar habitat types hosting E. sphagnicola (as E. paludosa ) in the literature from the following countries: The Netherlands, Slovenia, border region of Czechia / Slovakia, Hungary, Romania, Volga Upland in Russia, North Mongolia. According to Lange-Bertalot et al. (2011, p. 186), E. sphagnicola (as E. paludosa ) seems less abundant in “ minerotrophic peat bog complexes, dystrophic effluents, springs, brown water lakes or periodically wet habitats on sandstone rocks ”.

Figures

FIGURES 37–81. Eunotia sphagnicola Van de Vijver,A.Mertens & Lange-Bertalot, sp. nov. LM images taken from the holotype material (sample D283, Egelmeer, Veenendaal, the Netherlands, BR-4716). Figs 37–39. LM views of frustules in girdle view. Figs 40–81. LM views of the population arranged in decreasing length. Scale bar represents 10 µm.

FIGURES 82–84. Eunotia sphagnicola Van de Vijver, A.Mertens & Lange-Bertalot, sp. nov. SEM images taken from the holotype material (sample D283, Egelmeer, Veenendaal, the Netherlands). Fig. 82. External view of a frustule in girdle view showing the ventral side with the raphe branches. Fig. 83. SEM external view in valve face view showing the short terminal raphe fissures and the absence of spines. Fig. 185. Internal view in valve face view. The arrow indicates the rimoportula. Scale bars indicate 10 µm.