Fragilaria lucectorii Van de Vijver & C.E.Wetzel sp. nov. (Figs 105–149)
Light microscopy (Figs 105–145): Frustules solitary or in pairs, rectangular in girdle view (Fig. 105). Valves linear-lanceolate with usually slightly convex margins throughout the entire cell diminution series. Smaller valves with more distinctly convex margins (Figs 141–145).Apices protracted, rostrate to subcapitate, broadly rounded. Valve dimensions (n=50): valve length 15–25 µm, width 3.0–4.0 µm. Sternum narrow throughout its entire length, only weakly widening near the central area. Central area very large, buttressed, shallowly depressed, in part of the population unilateral, with large hyaline zone on one side and shortened striae on the opposite side. Other part of the population having large, fascia-like central area (e.g. Fig. 136). Ghost striae rarely discernible in LM (Figs 115, 136). Striae usually parallel to rarely very weakly radiate throughout the entire valve, alternating, 16–17 in 10 µm. Areolae not discernible in LM.
Scanning electron microscopy (Figs 146–149): Marginal spines absent (Fig. 146). Very large mantle plaques present at the mantle margin (Fig. 148, arrow). Striae uniseriate, composed of very broad, raised virgae compared to the small vimines (Figs 146–148). Areolae small, rounded to very slightly apically elongated (Figs 146–147). One small, rimmed rimoportula present at one apex, located on the last stria, replacing some of the areolae, close to the axial area (Fig. 147). Apical pore field of the ocellulimbus type, relatively large, composed of six rows of small rimmed pores, entirely located on the mantle (Fig. 147). Internally, rimoportula large, oblique (Fig. 149). Virgae clearly raised (Fig. 149).
Type: — FRANCE, Beaume River at Rosière, coll. date 18/05/2011, leg. M.-Y. Bey; (Holotype slide: BR-4894, Fig. 111 represents the holotype).
Registration:—http://phycobank.org/105484
Etymology:— The new species is named in honour of our late friend and colleague Luc Ector (†2022).
Ecology:— Wetzel & Ector (2015) reported the presence of the new species (as F. pectinalis) in several French rivers characterised by hard water and a relatively good water quality. The holotype sample was collected from the small (length 44 km) river Beaume in the Department of the Ardèche. In 2011 (the year of sampling) the river had a pH ranging between 7.6–8.4, a conductivity ranging between 38 and 499 µS/cm with the higher values in spring and summer and the lower values only in the winter months, and very low nutrient values of nitrate and phosphate. In Wetzel & Ector (2015, p. 282) a list of dominant taxa in the sample is added mainly composed of several Achnanthidium and Fragilaria species. According to Bey & Ector (2013, p. 228) the species is observed in the Rhône-Alpes region in watercourses of good quality. The species is very rare in the Rhône-Alpes region: observed only on the lower Drôme, the Romanche, the Baume, and the Eygues rivers (Wetzel et al. 2015).
Publication Date: 2025-10-30