Platessa itoupensis Tudesque, Le Cohu & C. E. Wetzel 2016, sp. nov.
Creators: name: Tudesque, Loïc
name: Cohu, René Le
name: Wetzel, Carlos E.
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Chromista
Bacillariophyta
Bacillariophyceae
Achnanthales
Achnanthaceae
Platessa
Platessa itoupensis

description: Platessa itoupensis Tudesque, Le Cohu & C.E.Wetzel, sp. nov. (Figs 72−145)   
LM (Figs 72−136): Valves linear-elliptical in the largest individuals (Figs 106, 107) becoming narrowly elliptical in large individuals (Figs 72−74) to elliptical in the smallest ones (Figs 100−105, 132−136). Length: 7.0−18.7 μm; width: 4.4−6.3 μm, ratio length/width: 1.5−3.2 (n= 60). Raphe sternum valve with narrow lanceolate axial area slightly widened towards the asymmetrical central area (Figs 72−105). Central area bordered by 1 to 3 shorter striae. Raphe branches straight with proximal endings hardly expanded. Striae radiate, coarse and curved; density: 8.5−12.6/10 μm. Sternum valve with a relatively wide lanceolate axial area (Figs 106−136). Striae subparallel in the central part of the valve becoming slightly radiate near the apices. Density of striae: 7.0−10/10 μm, with interstriae wider than the striae. SEM (Figs 137−145): Externally, RSV with proximal endings drop-like shaped surrounded by a weakly extended groove (Figs 137, 138, 140, arrow). Straight distal endings located in a transapically extended groove inverse circumflexe-like shaped (looks like bird flying, Figs 137−139, 141). Very narrow hyaline area surrounding the valve, widened and more silicified at the apices (Figs 137−139). Internally, proximal raphe endings clearly deflected to opposite directions, distal raphe ending slightly deflected in a tiny helictoglossa (Fig. 142). Externally, SV slightly convex (Fig. 143). Internally, areolae lying in shallow depressions and extending on the mantle (Fig. 145). Biseriate striae, sometimes irregularly triseriate. Areolae open externally (Figs 137−141) and occluded internally by a hymen stomato-like (Fig. 142, 144, 145). Apical striae frequently merged in the RSV but not in the SV (Figs 137−139, 141, 142). On both valves presence of notches (RSV Figs 137, 138, arrows; SV notches hidden by valvocopula). Valvocupula open (Fig. 142, arrow).  
 Type: — FRENCH GUIANA. River “Sable” in the southeastern side of the Oyapock basin in the Itoupe Mountains, Southern center of French Guiana, 3.040° N, 53.078° W, benthic periphyton, Sébastien Brosse, October 2010 (holotype PC! 00145187, Muséum National d’Histoire Naturelle de Paris, Paris, France, isotype ANSP! GC 26826 and raw material GCM 10312, the algae collection of the Academy of Natural Sciences, Philadelphia, U.S.A.)   
 Habitat:—freshwater periphyton from tropical and subtropical moist broadleaf forest.   
 Etymology:—in reference to the location where this species was sampled (i. e. Itoupe Mountains).   
 Distribution and ecology: —the only place where P. itoupensis has been sampled is the type locality and nowhere else to our knowledge. At the place where it was sampled, the trophic status and the saprobic degree are very low, respectively oligotrophic and oligosabrobic. The diversity of the diatom community is rather low. As example, P. itoupensis is accompanied by Gomphonema puiggarianum Grunow in Van Heurck (1880: 25), Luticola frenguelli Metzeltin & Lange-Bertalot (1998: 137) and Nupela astartiella Metzeltin & Lange-Bertalot (1998: 157).
description: Published as part of Tudesque, Loïc, Cohu, René Le & Wetzel, Carlos E., 2016, Two new Platessa (Bacillariophyceae) from Amazonia: Platessa guianensis spec. nov., and P. itoupensis spec. nov., pp. 237-255 in Phytotaxa 267 (4) on pages 245-246, DOI: 10.11646/phytotaxa.267.4.1, http://zenodo.org/record/13667166