Dictyosporium stellatum G.P. White & Seifert, Persoonia 26: 156 (2011)
Index Fungorum number: 561250
Etymology. From stellata (L.), referring to the star-like appearance of the colonies on the natural substrate.
Holotype: DAOM 241241; culture ex-type: CCFC 241241
Sexual morph: Undetermined. Asexual morph: Colonies on the natural substratum conspicuous, black, scattered, up to c. 7 mm diam, irregular in outline, composed of stellate sporodochia c. 200–500 μm wide, comprised of conidia radiating from a central point, often coalescing into irregular masses; often associated with or growing on stromata of a Hypoxylon-like fungus. Mycelium immersed in the substrate, not seen. Conidiophores c. 2–5 μm wide, micronematous, inconspicuous, composed of hyaline, thin-walled, irregularly branched, frequently septate hyphae. Conidiogenous cells 6.5–11 × 4.5–10 μm, globose, ellipsoidal or clavate, often remaining attached to the base of the conidium, hyaline and thin-walled, often collapsing, hyaline and thin-walled, sometimes becoming brown and thicker walled and then not collapsing; clavate cells with cylindrical connections to the basal cells of conidia rarely observed, perhaps suggestive of sympodial proliferation of conidiogenous cells that do not detach with the conidia. Conidia (50–)95–140(–175) μm long, (27.5–)30–40(–52.5) μm wide, 7.5–15 μm thick, dark brown, paler in apical cells, planar, cheiroid in ventral view, cylindrical to acicular in lateral view, consisting of (59–)110–165(–180) cells; individual cells discoid or doliiform, more oblong in side view than in face view, 3.5–6.5 μm tall, 4.5–6 μm wide in face view, 6–12 μm deep; typically arranged in (5–)6(–7) columns, 14–33 cells per column, the inner columns nested within the outer columns, the outer columns derived from the basal cell of the conidium; the intermediate columns are derived from the first or second cell of the outer columns; the inner columns derived from the first or second cell of the intermediate columns; usually with 2–3 central columns longest and of equal length, 2 – 3 peripheral columns shorter and of equal length, and one of the outer columns shortest but with several variations observed, including additional branching of one or more of the columns resulting in conidia with up to 9 columns, or straight or curved extension of 1–2 adjacent columns far beyond than the rest of the columns. Conidial appendages absent. Conidia germinating by hyaline hyphae 2–3 μm wide from the terminal cells of each column. (Description from Crous et al. 2011)
Photographic illustration: See Crous et al. (2011)
Culture characteristics: Colonies on cornmeal agar at RT 8–15 mm radius after 15 d, planar, obverse and reverse hyaline, margin uneven, sporulating after about 10 d, and then colonies with a uneven, spotty ring of conidial clusters around the inoculum, surface otherwise smooth and overlaid with sparse, hyaline aerial hyphae.
Notes: Dictyosporium stellatum produces the longest conidia of the approximately 34 species described (Goh et al. 1999, Cai et al. 2003, Crous et al. 2009). Stellate sporodochia, which give the species its epithet, have not been reported in other species. Despite the many collections attributable to this genus deposited in DAOM by the senior author and his mentor Dr S.J. Hughes over several decades, no other specimens were found and thus D. stellatum may be a rare fungus. On the holotype, sporulation was often most prolific on stromata of a Hypoxylon-like fungus, and some parasitism may be involved. The phylogenetic analysis below is based on recent internal transcribed spacer (ITS) analyses of Dictyosporium and related cheiroid genera (Tsui et al. 2006, Cai et al. 2008) with our own species added. Our species has distinct ITS sequences from those sequenced to date and sits in a well-supported clade that includes the type species, D. elegans. Although Dictyosporium appears monophyletic in this NJ tree, it is paraphyletic with the Pseudodictyosporium /Cheiromoniliophora/Cheirosporium clade in nine of ten MPTs in a heuristic parsimony analysis (not shown). No analyses have well-supported overall structure, perhaps reflecting the scant sampling of species in this group. (Notes from Crous et al. 2011)
Freshwater distribution: Ontario (Crous et al. 2011)
Crous PW, Groenewald JZ, Shivas RG, Edwards J, Seifert KA, Alfenas AC, Alfenas RF, Burgess TI, Carnegie AJ, Hardy GEStJ, Hiscock N, Hüberli D, Jung T, Louis-Seize G, Okada G, Pereira OL, Stukely MJC, Wang W, White GP, Young AJ, McTaggart AR, Pascoe IG, Porter IJ, Quaedvlieg W (2011) Fungal Planet description sheets: 69–91. Persoonia 26:108–156
Cai L, Zhang KQ, McKenzie EHC, Lumyong S, Hyde KD (2003) New species of Canalisporium and Dictyosporium from China and a note on the differences between these genera. Cryptogam Mycol 24:3–11
Crous PW, Braun U, Wingfield MJ, Wood AR, Shin HD, Summerell BA, Alfenas AC, Cumagun JCR, Groenewald JZ (2009) Phylogeny and taxonomy of obscure genera of microfungi. Persoonia 22:139–161
Goh TK, Hyde KD, Ho WH, Yanna (1999) A revision of the genus Dictyosporium, with descriptions of three new species. Fungal Divers 2:65–100
Recent SpeciesNeohelicomyces submersus