Eunotia zackenbergensis Goeyers, Van de Vijver & 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 : 270-272

Eunotia zackenbergensis Goeyers, Van de Vijver & Lange-Bertalot , sp. nov. ( Figs 127–168 )

Type:— GREENLAND, Zackenberg (sample M446, coll. date VIII.1998, leg. L. Beyens), holo- BR-4718! (Meise Botanic Garden, Belgium), iso- slide 406! (University of Antwerp, Belgium). The holotype is represented by Fig. 133 .

PhycoBank registration:—http://phycobank.org/103148

LM ( Figs 127–161 ): Frustules rectangular in girdle view ( Fig. 127 ). Valves weakly arched with parallel margins. Dorsal margins clearly convex. Ventral margins moderately concave in almost all cell cycle stages, smaller valves becoming more or less straight. Apices protracted, obliquely subcapitate and usually dorsally reflexed in the entire cell diminution series. Valve dimensions (n=50): length 16–62 µm, width 2.5–3.0 µm, length-to-width ratio 6.8–20. Terminal raphe nodules close to the poles. Striae 21–22 in 10 µm, equidistant throughout the entire valve length. Areolae not discernible in LM.

SEM ( Figs 162–168 ): Striae uniseriate throughout, composed of small, rounded areolae, 42–44 in 10 µm ( Figs 163, 164 ). Mantle striae ventrally composed of up to 7 small, rounded areolae near the valve middle ( Fig. 162 ). Apices with two rows of small, circular areolae ( Fig. 162 ). Spines lacking ( Figs 162, 163 ). Externally, raphe branches curving from almost halfway on the valve mantle onto the valve face ( Figs 162, 165 ). Terminal raphe fissures extending ca. halfway towards the dorsal side, visible on the valve face, ending in a distinct pore ( Fig. 164 ). Single rimoportula present at one of both poles, internally located close to the helictoglossa ( Figs 166, 167 ). Helictoglossa prominent at both poles ( Figs 167, 168 ).

Etymology:—The specific epithet zackenbergensis refers to Zackenberg, a Danish research station in the Northeast Greenland National Park in northeastern Greenland, where the species was first identified.

Distribution and ecology:— Eunotia zackenbergensis was collected from very wet mosses, growing in an Arctic bog pond in northeastern Greenland. Van Kerckvoorde et al. (2000) identified the species as E. fallax A.Cleve ( Cleve,1895: 33) and grouped the sample (M446) in an assemblage characterised by high frequencies of Rossithidium petersenii (Hustedt) Round & Bukhtiyarova ( Hustedt 1937: 179, Round & Bukhtiyarova 1996: 178) and several Pinnularia species. The new species is one of the most frequently observed Eunotia species in Greenland, often reaching relative abundances of up to 70% of the total diatom composition and usually present in bog ponds or fens (Goeyers, unpubl. res.). Due to confusion with E. paludosa , regularly reported from Arctic localities, its precise ecology and distribution is at present not well known.

Figures

FIGURES 127–161. Eunotia zackenbergensis Goeyers, Van de Vijver & Lange-Bertalot, sp. nov. LM images taken from the holotype material (sample M446, Zackenberg, Greenland, BR-4718). Fig. 127. Single valve in girdle view. Figs 128–161. LM views of the population arranged in decreasing length. Scale bar represents 10 µm.

FIGURES 162–168. Eunotia zackenbergensis Goeyers, Van de Vijver & Lange-Bertalot, sp. nov. SEM images taken from the holotype material (sample M446, Zackenberg, Greenland). Fig. 162. External view of a valve in girdle view. Note the course of the raphe branches on the mantle. Fig. 163. SEM external view in valve face view showing the short terminal raphe fissures and the absence of spines. Fig. 164. External detail of a valve apex focusing on the terminal raphe fissures. The external rimoportula opening is not discernible. Fig. 165. SEM external detail of a valve apex in girdle view, focusing on one of the raphe branches and the areolae on the apex. Fig. 166. Internal view in valve face view. Fig. 167. SEM internal detail of a valve apex showing the helictoglossa and the rimoportula. Fig. 168. SEM internal detail of a valve apex showing the helictoglossa. Scale bars indicate 10 µm for figs 162, 163 & 166, 1 µm for figs 164, 165, 167 & 168.