Gomphosphenia vallei Beauger, C.E.Wetzel, Allain & Ector, 2022

Beauger, Aude, Allain, Elisabeth, Voldoire, Olivier, Blavignac, Christelle, Rossi, Sofia, Wetzel, Carlos E. & Ector, Luc, 2022, Gomphosphenia vallei (Bacillariophyta), a new diatom species from a stream in the “ Réserve Naturelle Nationale de la Vallée de Chaudefour ”, Massif Central (France), Phytotaxa 542 (2), pp. 167-179 : 170-173

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.

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 ).

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.

Figures

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.

FIGURES26–33.SEMimagesofGomphospheniavallei.TypepopulationfromPérouseStream.26–30:Externalviewofentirevalveshowing theraphestructureandthestriae.31:Internalviewofanentirevalveshowingtheraphestructureandthestriae:32–33:Girdleviewofthefrustule. Scale bar = 5 μm (Figs 29–31), 4 µm (Figs 27, 32), 3 µm (Figs 26, 33) and 2 µm (Fig. 28).