Annulatascales » Annulatascaceae » Annulatascus

Annulatascus thailandensis


Annulatascus thailandensis W. Dong, H. Zhang & K.D. Hyde, in Hyde et al., Mycosphere 11(1): 418 (2020) 

             Index Fungorum number: IF556954

             Holotype – MFLU 18-1556


Saprobic on decaying wood submerged in freshwater. Sexual morph: Ascomata 170–200 μm high, 250–300 μm diam, solitary or gregarious, superficial, ellipsoidal or subglobose, black, coriaceous, with a lateral neck, often lying horizontally or obliquely to the substrate surface. Neck long or short, black, curving upwards or lying on the host surface, up to 600 μm long. Ostiole eccentric, lateral, black, periphysate. Peridium 32–37 μm thick at upper part, comprising 5–8 layers of brown to dark brown, thick-walled, compressed cells of textura angularis or round cells; 75–85 μm thick near the base where below the neck, comprising 12–15 layers of pale brown to brown, thin-walled, compressed cells of textura angularis or irregular cells; 3–5 layers of hyaline, compressed cells of textura angularis inwardly. Paraphyses ca 4–5.5 μm diam. near the base, tapering distally, hypha-like, numerous, hyaline, unbranched, septate, constricted at the septa. Asci 275–375 × 13–15 μm (x̅ = 310 × 13.7 μm, n = 10), 8-spored, unitunicate, cylindrical, apically rounded, with a long pedicel, up to 130 μm long, with a massive, wedge-shaped, refractive apical ring, 3.5–4 μm high × 5.5–6 μm wide. Ascospores 28–33 × 10.5–11.5 μm (x̅ = 30.8 × 11.2 μm, n = 10), uniseriate, hyaline, ellipsoidal to fusiform, straight to curved, 1–2-septate, slightly constricted at the septa, minutely guttulate, thin-walled, with a large, nearly ellipsoidal, mucilaginous sheath, 10–15 μm thick. Asexual morph: Undetermined (Hyde et al. 2020).

Culture characteristics: On PDA, colony circular with filamentous margin, reaching 30 mm in 35 days at 25°C, brown to white from above, white to pale brown from below, surface rough, dry, raised, with dense mycelia, edge filiform.

GenBank numbers: LSU: MN733254, SSU: MN733253, ITS: MN733256


           Notes: Annulatascus thailandensis fits well within the generic concept of Annulatascus in having a typical massive, apical ring and ellipsoidal to fusiform ascospores (Hyde 1992b, Maharachchikumbura et al. 2016b). In the phylogenetic tree, A. thailandensis clustered with A. hongkongensis with strong bootstrap support (Hyde et al. 2020). However, A. thailandensis has smaller ascospores (28–33 × 10.5–11.5 μm vs. 35–37.5 × 12.5–15 μm) and longer and thinner asci (275–375 × 13–15 μm vs. 250–275 × 25–30 μm). The ascospores of A. thailandensis are 1–2-septate, whereas those of A. hongkongensis are 3-septate (Ho et al. 1999). Annulatascus thailandensis is also similar to A. saprophyticus in asci and ascospore morphology and they have overlapping ascospore size (Luo et al. 2015). However, they can be separated by characters of ascomata (superficial, with long or short necks, lying horizontally or obliquely to the substrate surface vs. partly immersed, with straight upright necks to the substrate surface), size of asci (275–375 × 13–15 μm vs. 230.5–261 × 13.5–16.5 μm) and septa of ascospores (1–2-septate vs. 0–3-septate) (Luo et al. 2015).




           Figure 2. Annulatascus thailandensis (Material examined – THAILAND, Nakhon Si Thammarat Province, on submerged wood in a stream, 10 May 2018, W. Dong hat650, MFLU 18-1556, holotype). a-c Ascomata superficial on host surface. d Vertical section of ascoma. e Structure of peridium near the base. f Structure of peridium at upper part. g-j Unitunicate asci. k Paraphyses. l-o Ascospores. p Ascospore mounted in India ink. q Colony on PDA (from front). r Colony on PDA (from reverse). Scale bars: d, e, g-i = 50 μm, f = 30 μm, j-p = 20 μm (image from Hyde et al. 2020).



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