Ardissonea fulgens (Greville) Grunow ex De Toni, 1892

Lobban, Christopher S., Ashworth, Matt P., Camacho, Terance, Lam, Daryl W. & Theriot, Edward C., 2022, Revision of Ardissoneaceae (Bacillariophyta, Mediophyceae) from Micronesian populations, with descriptions of two new genera, Ardissoneopsis and Grunowago, and new species in Ardissonea, Synedrosphenia and Climacosphenia, PhytoKeys 208, pp. 103-184 : 103

Ardissonea fulgens (Greville) Grunow ex De Toni, 1892

References.

Peragallo and Peragallo 1897-1908, p. 311, pl. 79, fig. 5; Hustedt 1931-1959, p. 228, fig. 717a; Navarro 1982, p. 260, figs 64, 65; Poulin et al. 1986, figs 31, 32; Witkowski et al. 2000, p. 44, pl. 31, figs 9-11; Hein et al. 2008, p. 23, pl. 8: 1, 2).

Description from literature.

Kanjer et al. (2021) reported the ultrastructure of Greville’s type material of this species, collected at Mull, Scotland, and clearly showed a pseudoseptum and sculpted apices on the valvocopula; no apical notch was observed. That architecture is not visible in LM and so we can only assume that collections reported from Atlantic and Mediterranean Europe are the same until they can be examined. The species as traditionally understood is described as follows: Valves narrow, linear except slightly wider in the middle, 170-450 µm long, 10-15 µm wide, striae 12-14 in 10 µm, offset slightly where they meet such that a central line ( “pseudoraphe”) is distinct but very narrow; longitudinal costae very near to the valve edge and normally difficult to see ( Hustedt 1931-1959). Kanjer et al. (2021) show an undulation in the annulus near the middle of the valves in holotype material, a feature not reported elsewhere; they reported a stria density of 15-16 in 10 µm. Poulin et al. (1986, figs 31, 32) showed a valve without pseudoseptum, i.e., of the Ardissoneopsis type, with transapical costae on the virgae except at the poles, and the annulus near the valve-mantle junction marked externally by a gap in the areolae and internally by a longitudinal costa on each side. SEMs of var. Ardissoneopsis mediterranea , with 17 striae in 10 µm, in Güttinger (1989), include an oblique view suggesting that the annulus is not internally thickened. Navarro (1982) gave dimensions of 554 µm long by 13.5 µm wide, 14-15 striae in 10 µm. Hein et al. (2008) showed " Ardissonea cf. fulgens " with dimensions of 123-186 µm long by 6.5 µm wide, striae 20 in 10 µm-i.e., smaller and more finely striated than classical descriptions, and they noted that their counts of striae from images in Witkowski et al. (2000) showed stria densities of 19-22 in 10 µm.

Taxonomic comments.

For the reasons given below for separating single-walled Ardissonea taxa, it cannot remain in Ardissonea sensu stricto. If this species is confirmed to lack the apical notch, its pseudoseptum and sculpted valvocopula are sufficiently strong characters to place it in Synedrosphenia ; it certainly does not belong in Ardissoneopsis , proposed below, which lacks those characters, and we therefore must describe our Ardissoneopsis fulgens -like taxa as new species and propose a new combination of Synedrosphenia fulgens for Greville’s species.