Megacapitula villosa J.L. Chen & Tzean, Mycol. Res. 97(3): 347 (1993)

Index Fungorum number: IF 359484; MycoBank number: MB 359484; Facesoffungi number: FoF 09196; Figs. 1, 2

Saprobic on submerged decaying wood. Sexual morph Undetermined. Asexual morph Hyphomycetous. Mycelium superficial, partly immerged, composed of a loose network of repent, septate, branched, hyaline to light brown hyphae connected with conidia. Colonies on natural substrate effuse, solitary, dark brown to black. Conidiophores reduce to conidiogenous cells. Conidiogenous cells monoblastic, semi-macronematous, integrated, terminal or intercalary on mycelial extensions, branched, almost sessile. Conidia 139–321.5×42.5–94 µm (x̅=231×77 µm, n=15), holoblastic, solitary, scattered, oblong to ovoid, obclavate, ellipsoidal or obpyriform, internally with bundles of narrow cylindrical hyphae, together emerging as brown apical appendages from the top, disappearing when dry, faintly septate, dark brown to black, smooth-walled.

Culture characteristics – Conidia germinating on malt extract agar (MEA) within 12 h. Colonies growing on MEA, reaching 18 mm in 2 weeks at 28 °C, low convex, round with scalloped from middle to margin, radiating, slightly wavy, greyish brown to dark brown in surface, dark brown to black in reverse. Mycelium superficial and partly immersed, branched, septate, with hyaline to dark brown, pigmented verrucose, rough-walled, conidia produced on mycelium in culture at 45 days, 117–314×48–91 µm (x̅=213×70 µm, n=10), oblong to ovoid, obclavate, ellipsoidal or obpyriform, muriform, internally with bundles of narrow of cylindrical hyphal appendages emerging from the top, faintly septate, dark brown to black, smooth-walled.

Material examined – THAILAND, Chanthaburi Province, Laem Sing, on submerged decaying wood in a small freshwater stream, 7 July 2015, S. Boonmee, LS03 (MFLU 19-0257, new geographical record), living culture, MFLUCC 16-1231.

GenBank numbers – ITS=MZ538513, LSU=MZ538547, TEF1-α=MZ567115.

Notes – Megacapitula comprises a single species M. villosa as the type species (Wijayawardene et al. 2020; Index Fungorum 2021). Our new collection is a typical of Megacapitula, and it shares similar conidial morphology to Megacapitula villosa (PPH17E: ex-type species) from Taiwan (Chen and Tzean 1993), and strain GUFCC 15515 from India (Prabhugaonkar and Bhat 2011). Phylogenetic analysis of a combined LSU and ITS sequence dataset showed that our newly obtained strain MFLUCC 16-1231 clustered among Megacapitula villosa strains (AL4, cp053a), and basal to unidentified endophytic and saprobic strains with 100% MLBS and 1.00 BYPP support (Fig. 3). Comparison of ITS sequences showed that Megacapitula villosa (MFLUCC 16-1231) has 100% similarity with strain GUFCC 15,515. Two unidentified morphological strains AL4 and cp053a have only 1/459 (0.21%) base pair different from our taxon. Therefore, we identify our collection as M. villosa isolated from submerged decaying wood in a small freshwater stream and it is reported here as a new geographical record from Thailand (Figs. 1 and 2). Megacapitula villosa is likely to comprise more than one species and may represent a distinct
family.

Figure 1 – Megacapitula villosa (MFLU 19-0257, new geographical record). a, b Appearance of conidia with hyphal-like appendages and habit on wood substrate. c Immature conidium with hyphal-like appendages. d–g Mature conidia with apical hyphal-like appendages. h Conidium changed to brown in lactoglycerol and composed of compressed prosenchyma cells. Scale bars: a, b=200 µm, c–h=100 µm

Figure 2 – Megacapitula villosa sporulated in culture (MFLUCC 16-1231). a Germinated conidium with germ tubes surrounded. b, c Cultures on MEA after 1 month. d, e Mycelium development in culture. f–h Conidia. Scale bars: a, f–h=100 µm, d, e=10 µm

Figure 3 – Maximum likelihood phylogenetic tree based on a combined LSU and ITS sequence dataset of Megacapitula taxa and related families in Pleosporales. Sixty-seven strains are included in the combined analyses which comprise a total of 1456 characters. Cyclothyriella rubronotata CBS 385.39 is selected as the outgroup taxon. The best RAxML tree with a final likelihood value of − 12939.878192 is presented. RAxML analysis yielded 723 distinct alignment patterns and 29.63% of undetermined characters or gaps. Estimated base frequencies were as follows: A=0.242721, C=0.238518, G=0.291320, T=0.227442, with substitution rates AC=1.943333, AG=2.988826, AT=2.324598, CG=1.416039, CT=8.575259, GT=1.000000; gamma distribution shape parameter alpha=0.245601. Bootstrap support values for maximum likelihood (MLBS, left) equal to or greater than 70% is given above the nodes. Bayesian posterior probabilities (BYPP, right) equal to or greater than 0.95 are given above the nodes. Ex-type strains are in bold and newly generated sequence is in blue