Ulnaria verhaegeniana Van de Vijver, M.de Haan, Mertens & Cocquyt, 2017

Vijver, Bart Van De, Haan, Myriam De, Mertens, Adrienne & Cocquyt, Christine, 2017, Ulnaria verhaegeniana, a new diatom (Bacillariophyta) species from Belgium, Phytotaxa 326 (3), pp. 221-226 : 222-223

Ulnaria verhaegeniana Van de Vijver, M.de Haan, Mertens & Cocquyt sp. nov. ( Figs 1 –18)

LM ( Figs 1–13 ): Valves linear with parallel margins almost to valves’ apices; tapering abruptly towards very narrowly rounded, acute apices. Valves regularly slightly constricted mid-valve. Valve dimensions (n=20): length 55–90 μm, width 5.0–6.0 μm. Sternum almost central, occasionally eccentric, rather distinctive, often more or less irregular due to irregular shortening of bordering striae. Central area forming a large, apically elongated, rectangular fascia. Ghost striae often present. Striae parallel throughout entire valve, 10–12 in 10 μm, usually opposite on both sides of sternum although often stria number different on both sternum sides. One rimoportula present at each apex.

SEM (Figs 14–18): Valve face with weakly raised virgae and striae slightly sunken between them (Figs 14, 17). Striae uniseriate, composed of very small, rounded, externally occluded, almost cribrate areolae. Striae continuing without interruption onto valve mantle (Fig. 17). Two very small, almost invisible spines located above ocellulimbus (Fig. 16, arrows). Ocellulimbus large, with several rows of small poroids (Figs 16, 18). External rimoportulae openings rounded, located in middle of sternum, present at each pole (Figs 14, 16). Internally, rimoportulae possessing bilabiate shape, eccentrically positioned at 45–80° angle with axial sternum (Figs 15, 18). Striae sunken between raised virgae. Virgae interconnected by small struts (vimines) (Fig. 18). Cingulum structure not observed.

Type:— River Zenne , Sint-Pieters-Leeuw, Belgium, sample VMM156-2016 (50°47’28.60”N, 04°18’20.51”E), leg. VMM, coll. date 22 August 2016 (holotype, slide BR 4499 ; isotype, slide PLP –333, University of Antwerp, Belgium) .

Ecology and distribution:— Ulnaria verhaegeniana is up to now only found in two samples in the valley of the Zenne in Flanders, Belgium. The species was observed together with a large population of Ulnaria ulna in the river Zenne having an alkaline pH of 7.8 and a conductivity around 800 μS/cm. The species was also observed in one river in the southern part of Belgium during a routine monitoring (B. Van de Vijver, pers. obs.).

Etymology:—The new species is named in honour of our dear friend and colleague, Mrs. Gaby Verhaegen (VMM, Belgium) to thank her, on the occasion of retirement, for all these years of nice collaboration in diatom science and water monitoring.

Figures

FIGURES 1–13. Ulnaria verhaegeniana sp. nov. Type population from the river Zenne, Sint-Pieters-Leeuw (sample VMM156-2016). Figs 1–13. LM views of entire valves. Scale bar = 10 μm.