Pleosporales » Roussoellaceae » Roussoella

Roussoella intermedia



Roussoella intermedia Y.M. Ju, J.D. Rogers & Huhndorf

Index Fungorum number: IF415227

Holotype: WSP, Ju 76110103


Sexual morph: Ascomata 190–195 × 168–176 μm, immersed, becoming partially erumpent, gregarious and in rows surrounded by stromatic tissue, dark brown, globose to broadly obpyriform, with clypeus covering the ostiole; clypeus slightly raised, dark brown. Beak 54.5–58.5 × 39–47 μm, central, periphysate. Peridium 17–19.5 μm thick, composed of compressed hyaline cell layers; cells thickened and darkened toward the apex. Pseudoparaphyses trabeculate, 1–2 μm wide, embedded in a gelatinous matrix, branched and anastomosing above the asci. Asci 76–98 × 8–10 μm, broadly cylindrical, with rounded apex, persistent, narrowing to a short hoof-shaped stipe, fissitunicate, with small ocular chamber seen when mounted in 5% KOH, containing eight overlapping uniseriate ascospores. Ascospores 12–15(–16) × 4–6 μm ( = 13.5 × 5 μm), fusiform-ellipsoid, brown, 1-septate, slightly constricted at the septum, mostly with rounded ends, with longitudinal striations less than 1 μm wide. Asexual morph: Undetermined. (Description from Fallah and Shearer 2001)


Material examined: United States of America, Wisconsin, Trout Lake, UTM Zone 16, 293196mE, 5098921mN, 46°00.838'N, 89°40.283'W, on submerged, partially decomposed bark, 14 Nov 1997, PMF and JLC P1-109 (ILLS 54062).


Notes: The genus Roussoella, typified by R. nitidula and originally found on bamboo, was established by Saccardo and Paoletti (1888). There are at least nine species within this genus all of which occur either on bamboo or palm (Hyde 1997). The asci in Roussoella are bitunicate and although the endotunica are commonly ejected outward by applying pressure on the coverslip, the asci have not yet been seen to discharge ascospores in a fissitunicate manner (Hyde et al 1996; P.M. Fallah personal observation). The LTER specimen described from Trout Lake was found on submerged bark of probably Alnus. Ascomata are grouped in rows and possess stromatic tissue formed under a darkened clypeus. Ju et al. (1996) separated Roussoella from Didymosphaeria based primarily on the presence of multiple ascomata per stroma, formation of stromatal tissue under a clypeus, and distinct Iongitudinal striations on ascospores. The ascomata of the LTER specimen do occur in groups formed in rows, but they are not at very close proximity to one another such as those found in R. aequatoriensis (Hyde 1997), R. intermedia or R. scabrispora. The ascospore measurements are closest to R. intermedia, a species that has a spore size range between that of R. hysteroides and R. pustulans (Ju et al. 1996). (Notes from Fallah and Shearer 2001)


Freshwater distribution: United States of America (Fallah and Shearer 2001)




Fig. 1 Roussoella intermedia (ILLS 54062). 179. Median longitudinal section through ascoma. 180. Periphyses in ostiolar canal. 181. Peridium. 182. Trabeculate pseudoparaphyses embedded in low viscosity embedding media. 183. Trabeculate pseudoparaphyses showing branching and anastomosing. 184. Asci and trabeculate pseudoparaphyses in gel matrix. 185. Mature ascus. 186. A dehisced ascus. 187. Ascospores with dark septa and striations. Bars: 179 = 50 μm, 180–186 = 25 μm, 187 = 12.5 μm. (Fallah and Shearer 2001)



Fallah PM, Shearer CA (2001) Freshwater ascomycetes: new or noteworthy species from north temperate lakes in Wisconsin. Mycologia 93:566–602

Hyde KD (1997) The genus Roussoëlla, including two new species from palms in Cuyabeno, Ecuador. Mycol Res 101:609–616

Hyde KD, Eriksson OE, Yue JZ (1996) Roussoëlla, a genus of uncertain relationships, with a Cytoplea anamorph. Mycol Res 100:1522–1528

Ju YM, Rogers JD, Huhndorf SM (1996) Valsaria and notes on Endoxylina, Pseudothyridaria, Pseudovalsaria, and Roussoella. Mycotaxon. 58:419–481

Saccardo PA, Paoletti G (1888) Mycetes Malaccenses. Atti Institute Vaneto di Scienze Lettere, ed Arti ser 6. 6:387428


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