Occultibambusa pustula D.Q. Dai & K.D. Hyde, Fungal Diversity 82: 30 (2016)
Saprobic on decaying wood submerged in freshwater. Sexual morph: Ascomata 190–220 μm high, 320–350 μm diam., black, scattered, immersed with proliferating papilla erumpent through host surface, ellipsoidal, ostiolate. Papilla 60–80 μm high, 25–70 μm wide, obvious short cylindrical, central ostiolate, periphysate. Peridium 25–90 μm thick, composed of several layers of brown to black, thin-walled cells of textura angularis, flattened and thin at the base, with palisade-shaped cells near the base. Pseudoparaphyses 2–3 μm wide, numerous, cellular, hypha-like, hyaline, septate. Asci 8-spored, bitunicate, mostly broadly clavate or sometimes narrowly clavate, (60–)78–125 × 12.5–15.5 μm ( = 90 × 14 μm, n = 15), apically rounded, with an ocular chamber, 2.8 μm high × 3.8 μm wide, short or long pedicellate and up to 37 μm long when mature. Ascospores 22–29 × 6–8 μm ( = 27 × 7.5 μm, n = 20), uni- to bi-seriate, fusiform, mostly slightly curved towards different directions at each end, pale brown and 1-septate when young, brown, 3-septate and deeply pigmented at septa when mature, becoming dark brown in central two cells and hyaline to pale brown in bipolar cells, constricted at the septa, guttulate, thin-walled, smooth, without sheath. Asexual morph: Undetermined.
Culture characteristics: On PDA, colony circular, reaching 15 mm in 25 days at 25 °C, dark grey from above, black from below, surface rough, with dense mycelium, dry, raised, edge entire.
Material examined: CHINA, Yunnan Province, Dehong, on submerged wood in a stream, 25 November 2017, G.N. Wang, H1B-1 (MFLU 18-1208), living culture MFLUCC 18-1028; ibid., H1B-2 (HKAS 101724), living culture KUMCC 18-0074.
Notes: The collection of Dong et al. (2020), MFLUCC 18-1028, clusters with Occultibambusa pustula MFLUCC 18-1028 with high bootstrap support. Occultibambusa pustula only has LSU and ITS sequence data in GenBank. They have identical LSU sequence data and three nucleotide differences in ITS sequence data between MFLUCC 18-1028 and MFLUCC 11-0502, which indicate them to be the same species.
Occultibambusa pustula was collected from dead culm of bamboo in Thailand and characterized by immersed ascomata with central ostiole, cylindrical asci, and fusiform, 1-septate, hyaline to pale brown ascospores (Dai et al. 2017). Our collection has very similar morphological characters with O. pustula and they have overlapping ascus and ascospore size. The holotype of O. pustula studied by Dai et al. (2017) was immature as shown in their photo plate, and thus we describe more details for this species from our mature collection MFLUCC 18-1028. In our collection, the ascospores are initially pale brown and 1-septate, which are similar to the holotype. At maturity, ascospores become brown, 3-septate, deeply pigmented at septa, and with two dark brown central two cells and hyaline to pale brown end cells. In addition, we observed prominent cylindrical papilla and palisade-shaped cells near the ascomatal base, which were not described in the holotype. Based on phylogenetic analysis and morphological observation, Dong et al. (2020) identify their collection MFLUCC 18-1028 as O. pustula. This is a new habitat and geographical record for O. pustula from freshwater in China.
Freshwater distribution: China (Dong et al. 2020)