Ascominuta lignicola Ranghoo & K.D. Hyde
Index Fungorum number: IF 464377
Holotype: HKU (M) 5246
Etymology: From the Latin, lignum = wood, and -cola = dweller, in reference to the habitat on wood.
Sexual morph: Ascomata 60–65 µm high, 70–75 µm diam, no visible necks even in section, superficial to partly immersed the host substrate, globose, dark brown to black, solitary or aggregated. Ostiole periphysate. Peridium 10–15 µm wide, comprising three to five layers of hyaline compressed cells, with an outer layer of dark brown textura angularis. Pseudoparaphyses 5–15 µm long, 2–3 µm wide at base, comprising shor tchains of globose cells, often breaking up into individual cells, constricted at the septa. Asci 25–30 × 25–30 µm, 4-spored, globose, pedicellate, bitunicate. Following the dehiscence of the ectotunica, theendotunica extends and finally the ascospores are released. Ascospores 22–25 × 8–10 µm, biseriate, broadly fusiform, 1-septate, constricted at the septa, hyaline, surrounded by an irregular mucilaginous sheath. Asexual morph: Undetermined. (Description from Ranghoo and Hyde 2000)
Material examined: CHINA, Hong Kong, New Territories, Plover Cove Reservoir: on submerged wood, Jan. 1997, V. M. Ranghoo (HKUM 5246); culture ex-type HKUCC 3709.
Notes: Ascominuta lignicola resembles some species of Wettsteinina (e.g, W. savilei Shoemaker et Babcock) in producing hyaline, 1-septate ascospores, surrounded by a mucilaginous sheath. Species of Wettsteinina, however, are usually pathogenic or saprobic on plant material (not wood) and asci are globose to broadly fusiform with 8(16) ascospores. The ascospores in Wettsteinina are 1-7-sepate and usually brown when mature (Shoemaker and Babcock 1987). Pseudoparaphyses are numerous and filiform in Wettsteinina as compared to sparse and composed of short chains of globose cells in Ascominuta. Wettsteinina does therefore not appear to be a suitable genus to accommodate Ascominuta. Ascominuta lignicola should also be compared with Mycosphaerella Johanson (Mycosphaerellaceae) as the ascomata of Mycosphaerella species generally lack pseudoparaphyses. Ascominuta is similar to several Mycosphaerella species in having small globose ascomata and 2-celled ascospores (Corlett 1988; Hanlin 1990; Fröhlich and Hyde 1998). Ascominuta differs from Mycosphaerella in having 4-spored globose asci, while those of Mycosphaerella are 8-spored and clavate to obclavate. (Notes from Ranghoo and Hyde 2000)
Freshwater distribution: China (Ranghoo and Hyde 2000), Thailand (Hu et al. 2010)
Fig. 1. Ascominuta lignicola 1. Superficial ascomata (arrowed). 2. Section through ascoma. 3, 5. Asci with 4-spores. 4. Pseudoparaphyses (arrowed). 6–8. One-septate ascospores with large mucilaginous sheaths. Scale bars: 1=100 µm, 2, 3, 5 = 20 µm, 4, 6–8 = 10 µm. (Ranghoo and Hyde 2000)
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Hanlin RT (1990) Illustrated genera of ascomycetes. APS Press, Minnesota, USA
Hu DM, Cai L, Chen H, Bahkali AH, Hyde KD (2010) Fungal diversity on submerged wood in a tropical stream and an artificial lake. Biodivers Conserv 19:3799–3808. https://doi.org/10.1007/s10531-010-9927-5
Ranghoo VM, Hyde KD (2000) Ascominuta lignicola, a new loculoascomycete from submerged wood in Hong Kong. Mycoscience 41:1–5. https://doi.org/10.1007/BF02464379
Shoemaker RA, Babcock CE (1987) Wettsteinina. Can J Bot 65:373–405. https://doi.org/10.1139/b87-048