Phaeoseptum aquaticum Ying Zhang, J. Fourn. & K.D. Hyde
Index Fungorum number: IF561890
Etymology: from the Latin ‘‘aquaticum’’, in reference to the freshwater habitat of this taxon
Holotype: IFRD 8986
Saprobic on submerged wood in freshwater. Sexual morph: Ascomata scattered to gregarious, fully immersed under a small blackened pseudoclypeus, which are 170–250 μm long, 80 μm wide, appearing as black, elongated regions on host surface; ascomata depressed spherical, 300–400 μm high3400–600 μm diam, laterally flattened. Pseudoclypeus 20–28 μm thick, composed of host cells with black deposits and dark brown hyphae. Peridium pseudoparenchymatous, of thin-walled cells, 20–30 μm thick, at apex comprising small, isodiametric angular cells that are more pigmented outwardly, at sides with larger and more flattened hyaline cells, at base of small angular pigmented cells. Hamathecium of narrowly cellular pseudoparaphyses, 1.7–2 μm broad, septate, anastomosing. Asci 135–190 × 19–25 μm, eight-spored, bitunicate, fissitunicate dehiscence not observed, cylindrical-clavate, pedicel well defined, 28–65 μm long; ocular chamber small and truncate, with a small apical ring best seen in immature asci, ascus apex thickened. Ascospores 30.5–38 × 9.5–12 μm, uniseriate at base and overlapping triseriate at apex, broadly fusoid with broadly rounded ends, slightly curved, 9–13(–16)-transversally septate, end cells usually larger than others, with a vertical septum in nearly all cells, exceptionally with a Y-shaped septum in the end cell, not constricted at the septa, partly pale brown, the septa, having at maturity a thickened and heavily pigmented appearance, wall smooth, without sheath or appendages. Asexual morph: Undetermined. (Descriptions from Zhang et al. 2013)
Material examined: FRANCE, Haute Garonne, Palaminy, in a swamp along D 10 road, on submerged branch of Robinia pseudoacacia, 14 Jan 2007, leg J Fournier, Michel Delpont & Xavier Besombes, det J Fournier (MFLU10-1101, paratype). Martres Tolosane, Le Moulin, banks of Garonne River, on driftwood of Salix sp., 23 Jun 2007, leg J Fournier, Michel Delpont & Xavier Besombes, det J Fournier (IFRD 8986, holotype), ex-type culture CBS 123113.
Notes: Phaeoseptum aquaticum is morphologically comparable with Mauritiana rhizophorae. They both share medium-sized immersed ascomata that form under a pseudoclypeus, narrowly cellular pseudoparaphyses, eight-spored cylindrical to broadly clavate asci as well as pale brown ascospores with thickened septa. They differ in that Ph. aquaticum has dictyosporous ascospores, while M. rhizophorae has phragmosporous ascospores. Phaeoseptum is from freshwater, while Mauritiana is amaritime genus growing in the intertidal region of mangroves. Phaeoseptum aquaticum is sibling to the clade of Pontoporeia biturbinata, Halotthia posidoniae and M. rhizophorae. Thus, a new genus, Phaeoseptum, is introduced here to accommodate Ph. aquaticum. (Notes from Zhang et al. 2013)