Platessa itoupensis Tudesque, Le Cohu & C.E.Wetzel, 2016

Tudesque, Loïc, Cohu, René Le & Wetzel, Carlos E., 2016, Two new Platessa (Bacillariophyceae) from Amazonia: Platessa guianensis spec. nov., and P. itoupensis spec. nov., Phytotaxa 267 (4), pp. 237-255 : 245-246

publication ID	https://doi.org/ 10.11646/phytotaxa.267.4.1
DOI	https://doi.org/10.5281/zenodo.13667182
persistent identifier	https://treatment.plazi.org/id/A9278170-FFDB-8107-FF5B-50046D02FDBD
treatment provided by	Felipe
scientific name	Platessa itoupensis Tudesque, Le Cohu & C.E.Wetzel
status	sp. nov.

Treatment

Platessa itoupensis Tudesque, Le Cohu & C.E.Wetzel , sp. nov. ( Figs 72−145 View FIGURES 72–136 View FIGURES 137–142 View FIGURES 143–145 )

LM ( Figs 72−136 View FIGURES 72–136 ): Valves linear-elliptical in the largest individuals ( Figs 106, 107 View FIGURES 72–136 ) becoming narrowly elliptical in large individuals ( Figs 72−74 View FIGURES 72–136 ) to elliptical in the smallest ones ( Figs 100−105, 132−136 View FIGURES 72–136 ). 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 View FIGURES 72–136 ). 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 View FIGURES 72–136 ). 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 View FIGURES 137–142 View FIGURES 143–145 ): Externally, RSV with proximal endings drop-like shaped surrounded by a weakly extended groove ( Figs 137, 138, 140 View FIGURES 137–142 , arrow). Straight distal endings located in a transapically extended groove inverse circumflexe-like shaped (looks like bird flying, Figs 137−139, 141 View FIGURES 137–142 ). Very narrow hyaline area surrounding the valve, widened and more silicified at the apices ( Figs 137−139 View FIGURES 137–142 ). Internally, proximal raphe endings clearly deflected to opposite directions, distal raphe ending slightly deflected in a tiny helictoglossa ( Fig. 142 View FIGURES 137–142 ). Externally, SV slightly convex ( Fig. 143 View FIGURES 143–145 ). Internally, areolae lying in shallow depressions and extending on the mantle ( Fig. 145 View FIGURES 143–145 ). Biseriate striae, sometimes irregularly triseriate. Areolae open externally ( Figs 137−141 View FIGURES 137–142 ) and occluded internally by a hymen stomato-like ( Fig. 142 View FIGURES 137–142 , 144, 145 View FIGURES 143–145 ). Apical striae frequently merged in the RSV but not in the SV ( Figs 137−139, 141, 142 View FIGURES 137–142 ). On both valves presence of notches (RSV Figs 137, 138 View FIGURES 137–142 , arrows; SV notches hidden by valvocopula). Valvocupula open ( Fig. 142 View FIGURES 137–142 , 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) .