Riomyces rotundus A. Ferrer, A.N. Mill., Sarmiento & Shearer
Index Fungorum number: 561100
Sexual morph: Ascomata on submerged wood, 440–720 ´ 440–600 µm, immersed to erumpent in the substrate, globose to subglobose, membranous, black, ostiolate. Neck short, dark brown, 76 ´ 84 µm. Hamathecium composed of globose, wide, hyaline, deliquescent cells, 35–100 µm diam. Asci 250–340 ´ 25–30 µm, unitunicate, broadly cylindrical, thin-walled, with a short pedicel, lacking an apical pore and other apical structures, eight-spored, uniseriate. Ascospores 30–40 ´ 20–25 µm (mean = 35 ´ 22 µm, n = 30), broadly ellipsoidal-fusiform, hyaline, three-septate, not constricted at septa, thick-walled (4–5 µm), surrounded by an irregular gelatinous sheath extending about ca. 10–20 µm from the ascospore wall; sheath margins stain in aqueous nigrosin, ascospores accumulate in a mass at the tip of the neck after discharge.
Asexual morph: Undetermined
Specimen examined: COSTA RICA, Alajuela and Heredia, on submerged wood
References: Ferrer A, Miller AN, Sarmiento C, Shearer CA. (2012) Three new genera representing novel lineages of Sordariomycetidae (Sordariomycetes, Ascomycota) from tropical freshwater habitats in Costa Rica. Mycologia 104, 865–879.
Fig. Riomyces rotundus from the holotype (AF303-1). 30. Whole mount of ascoma. 31. Neck. 32. Asci surrounded by globose cells. 33. Unitunicate ascus. 34. Empty Asci. 35, 36. Globose cells. 37, 38. Ascospores showing gelatinous sheath expanding in water. Scale Bar 30-38 = 10 µm.