Gomphosphenia vallei (Bacillariophyta), a new diatom species from a stream in the “ Réserve Naturelle Nationale de la Vallée de Chaudefour ”, Massif Central (France) Author Beauger, Aude 0000-0002-0911-0500 Université Clermont Auvergne, CNRS, GEOLAB, F- 63000 Clermont-Ferrand, France & aude. beauger @ uca. fr; https: // orcid. org / 0000 - 0002 - 0911 - 0500 aude.beauger@uca.fr Author Allain, Elisabeth 0000-0002-6411-5873 Université Clermont Auvergne, CNRS, GEOLAB, F- 63000 Clermont-Ferrand, France & elisabeth. ALLAIN @ uca. fr; https: // orcid. org / 0000 - 0002 - 6411 - 5873 Author Voldoire, Olivier 0000-0003-1306-3054 Université Clermont Auvergne, CNRS, GEOLAB, F- 63000 Clermont-Ferrand, France & olivier. voldoire @ uca. fr; https: // orcid. org / 0000 - 0003 - 1306 - 3054 olivier.voldoire@uca.fr Author Blavignac, Christelle 0000-0003-2999-7644 Centre Imagerie Cellulaire Santé, UCA PARTNER, 63000 Clermont-Ferrand, France & christelle. blavignac @ uca. fr; https: // orcid. org / 0000 - 0003 - 2999 - 7644 christelle.blavignac@uca.fr Author Rossi, Sofia 0000-0003-1384-0642 39 rue Simone Weil, 49000 Angers, France & sofia. rossi 4961 @ gmail. com; https: // orcid. org / 0000 - 0003 - 1384 - 0642 sofia.rossi4961@gmail.com Author Wetzel, Carlos E. 0000-0001-5330-0494 Luxembourg Institute of Science and Technology (LIST), Environmental Research and Innovation Department (ERIN), Observatory for Climate, Environment and Biodiversity (OCEB), 41 rue du Brill, 4422 Belvaux, Luxembourg & carlos. wetzel @ list. lu; https: // orcid. org / 0000 - 0001 - 5330 - 0494 carlos.wetzel@list.lu Author Ector, Luc 0000-0002-4573-9445 Luxembourg Institute of Science and Technology (LIST), Environmental Research and Innovation Department (ERIN), Observatory for Climate, Environment and Biodiversity (OCEB), 41 rue du Brill, 4422 Belvaux, Luxembourg & luc. ector @ list. lu; https: // orcid. org / 0000 - 0002 - 4573 - 9445 luc.ector@list.lu text Phytotaxa 2022 2022-04-05 542 2 167 179 http://dx.doi.org/10.11646/phytotaxa.542.2.4 journal article 53639 10.11646/phytotaxa.542.2.4 340c66f2-8b52-4fdd-b329-c59b697c965b 1179-3163 6415941 Gomphosphenia vallei Beauger, C.E.Wetzel, Allain & Ector sp . nov . ( Figs 2 –45) Light microscopy observations ( Figs 2–25 ): Valves linear-clavate in larger specimens to clavate in smaller ones and elliptical in the smallest individuals. Headpoles rounded, footpoles narrowly rounded. Valve dimensions (n = 30): length 4.2–13.1 µm, width 1.5–2.5 µm. Raphe straight, filiform. Striae visible in LM, almost parallel throughout the valve to slightly radiate in the mid-valve, 23–29 in 10 µm. Axial area linear and narrow. Central area from absent to asymmetrical with round and distinct central nodule. In girdle view, frustules almost rectangular to slightly wedgeshaped. FIGURES 2–25. LM images of Gomphosphenia vallei . Type population from Pérouse Stream. 2–19: Valve view; 20–25: Girdle view. Scale bar = 5 μm. Scanning electron microscopy observations ( Figs 26–33 ): Valve face flat. Externally, striae composed of single slit-like areolae, becoming very short slit near the poles ( Figs 26–30 ). Striae slightly radiate in central part of valve, becoming convergent towards both head and footpoles. Raphe straight, filiform, with slightly dilated distal and proximal raphe endings ( Figs 26–30 ). Distal raphe fissures terminating on the valve face, not extending onto the valve mantle ( Fig. 28 ). Internally, proximal raphe endings bent in the same direction ( Fig. 31 ). Internal terminal raphe fissures ending in helictoglossae ( Fig. 31 ). Single row of slit-like areolae located on the valve mantle ( Figs 26, 28, 30, 32 ), sometimes rounded in shape near the mid-valve and towards the footpole ( Figs 27, 33 ). Central area with a unilateral fascia, with a short areola on one side and absence of areola on the other side ( Figs 26–29 ). Central nodule slightly raised ( Fig. 31 ). Apical pore fields absent ( Fig. 28 ). In girdle view, frustules with cingulum composed of open bands, each bearing one row of small round pores ( Figs 28, 30, 32–33 ). FIGURES26–33. SEM images of Gomphosphenia vallei .Type population from Pérouse Stream.26–30:External view of entire valve showing the raphe structure and the striae.31:Internal view of an entire valve showing the raphe structure and the striae:32–33:Girdle view of the frustule. Scale bar = 5 μm (Figs 29–31), 4 µm (Figs 27, 32), 3 µm (Figs 26, 33) and 2 µm (Fig. 28). TABLE 2. Main characteristics of Gomphosphenia vallei and 4 similar Gomphosphenia species.

Species	Valve length (µm)	Valve width (µm)	Number of striae (in 10 µm)	Valve outline	Areolae	Axial area	Central area	Internal proximal raphe endings	Girdle view	Ecology
Gomphosphenia vallei	4.2–13.1	1.5–2.5	23–29	lanceolate-clavate in larger specimens to clavate in smaller ones and elliptical in the smallest individuals	striae uniseriate, composed of single slit-like areolae, becoming almost round poroids near the poles	linear and narrow	absent to asymmetrical	deflected in one direction	almost rectangular to slightly wedge-shaped	in running waters (streams) with low conductivity
Gomphosphenia americana Kociolek & E.W.Thomas in Kociolek et al. (2014: 45)	9.0–13.0	2.0–3.0	29–32	lanceolate-clavate	single elongated areola	linear and narrow	linear to circular, sometimes asymmetrical	recurved to one side	cuneate and flexed about the transapical axis	in lakes
Gomphosphenia fontinalis Lange-Bertalot, Ector & Werum in Werum & Lange-Bertalot (2004: 163)	5.0–8.0	1.5–2.3	25–32(36)	club-shaped	single elongated areola	lanceolate	wide, not distinctly separated from the axial area	unilaterally deflected as small hooks	wedge-shaped	species of carbonate water, apparently strictly dependent on karstic springs
Gomphosphenia indistincta Kociolek & E.W.Thomas in Kociolek et al. (2014: 46)	7.5–25.0	2.0–3.0	almost 24	linear-lanceolate clavate with margins with undulations in larger specimens	single elongated areola	narrow straight	asymmetrical-expanded	recurved in one direction	/	in lakes
Gomphosphenia stoermeri Kociolek & E.W.Thomas in Thomas et al. (2009: 230)	10.0–21.1	1.5–3.1	28–35	linear-clavate	single elongated areola	rather narrow, linear	absent to only weakly developed	tightly hooked in one direction	slightly wedge-shaped	epilithic, subaerial in Cataract Falls, on rivers of northern Sweden

Type locality : — FRANCE . Chambon-sur-Lac , “Réserve Naturelle Nationale de la Vallée de Chaudefour”: Pérouse Stream , sample PER _200821, 1,184 m a.s.l. , E688534.487, N6493049.143 ( Lambert 93), collection date 20 August 2021 (assigned here, holotype : CLF !, slide no. CLF310234 ; isotype: BR ! slide no. BR-4707. The holotype is represented by Fig. 12 ). Etymology : — This species is named for Eric Vallé, curator of the National Nature Reserve and passionate about botany. Ecology and associated diatom taxa : — The Pérouse Stream, situated in the glacial cirque of Chaudefour Valley, is characterized by a low conductivity (35 μS cm-1 ), a low temperature (11.9 °C) and is well oxygenated (92.9% of dissolved oxygen) ( Table 1 ). The pH is 7.09. As underlined the conductivity, the concentrations of the measured ions are low with a maximum for the sodium concentration ( 2.53 mg L- 1 ). The type population of G. vallei was found in Pérouse Stream associated with other taxa. In August 2021 , the two co-dominant taxa were Planothidium lanceolatum (Brébisson ex Kützing 1846: 247 ) Lange-Bertalot (1999: 287) (36%) and Rhoicosphenia abbreviata (C. Agardh 1831: 34 ) Lange-Bertalot (1980: 586) (30%). The other species well represented (<10%) were Achnanthidium subatomus ( Hustedt 1939: 554 ) Lange-Bertalot (1999: 273) (7.1%), Gomphonema sp. cf. minutum C. Agardh (1831: 34) (6.4%), Navicula reichardtiana Lange-Bertalot in Lange-Bertalot & Krammer (1989: 163) (2.3%), Odontidium mesodon ( Ehrenberg 1839: 57 ) Kützing (1849: 12) (2.3%), Gomphosphenia vallei (2.3%), Reimeria sinuata (W. Gregory 1856: 4 ) Kociolek & Stoermer (1987: 457) (1.9%), Planothidium curtistriatum C.E.Wetzel, Van de Vijver & Ector in Wetzel et al . (2019: 61) (1.9%), Cocconeis rouxii Héribaud & Brun in Héribaud (1893: 45) (1.9%) and Encyonema minutum (Hilse in Rabenhorst 1862 : No. 1261) D.G.Mann in Round et al. (1990: 667) (1.1%). At last, Chamaepinnularia obsoleta ( Hustedt 1942a: 69 ) C.E.Wetzel & Ector in Wetzel et al. (2013: 158) , Cyclotella antiqua W. Smith (1853: 28) , Geissleria acceptata ( Hustedt 1950: 398 ) Lange-Bertalot & Metzeltin (1996: 64) , Gomphonema clavatum Ehrenberg (1832: 88) , Gomphonema exilissimum (Grunow in Van Heurck 1880 : pl. 25, fig. 12) Lange-Bertalot & E.Reichardt in Lange-Bertalot & Metzeltin (1996: 70) , Humidophila perpusilla ( Grunow 1860: 552 ) R.L.Lowe, Kociolek, J.R.Johansen, Van de Vijver, Lange-Bertalot & Kopalová (2014: 358) , Mayamaea permitis ( Hustedt 1945: 919 ) Bruder & Medlin (2008: 327) , Meridion constrictum Ralfs (1843: 458) , Nitzschia hantzschiana Rabenhorst (1860: 40) , Nitzschia soratensis E.Morales & M.L.Vis (2007: 128) , Nupela lapidosa ( Krasske 1929: 350 ) Lange-Bertalot (1999: 274) , Pantocsekiella ocellata ( Pantocsek 1901: 134 ) K.T.Kiss & Ács in Ács et al. (2016: 62) , Pinnularia sinistra Krammer (1992: 105) , Psammothidium helveticum ( Hustedt 1933: 385 ) Bukhtiyarova & Round (1996: 8) , Psammothidium subatomoides (Hustedt in Schmidt 1936 : pl. 404) Bukhtiyarova & Round (1996: 13) and Sellaphora atomoides (Grunow in Van Heurck 1880: 107 ) C.E.Wetzel & Van de Vijver in Wetzel et al. (2015: 219) represented less than 1% of the whole community.