Pleosporales » Dictyosporiaceae » Dictyosporium

Dictyosporium canisporum

Dictyosporium canisporum L. Cai & K. D. Hyde

 

Index Fungorum number: 488327

Etymology: "canisporum", referring to the conidia which have two appendages hanging off like a dog's head.

 

Sexual morph: Undetermined. Asexual morph: Sporodochia on natural substratum 250-600 µm diam, punctiform, scattered, black, granular. Mycelium mostly immersed, composed of brown, smooth, thin-walled, septate, branched hyphae. Conidiophores micronematous, mononematous, pale brown, smooth, thin-walled, septate, branched, cylindrical, some persistent at conidial maturity. Conidiogenous cells monoblastic, integrated, pale brown, smooth, thin-walled, cylindrical, cuneiform, determinate. Conidial secession rhexolytic. Conidia (27.5 –)32.5–47.5 × 20–25 µm (x̄ = 41.5 × 23 µm, n = 25), cheiroid, complanate, medium brown, becoming dark brown with maturity, smooth, euseptate, holoblastic, one-celled thick and flattened, in surface view fan-shaped, somewhat obovoid, in lateral view cylindrical or clavate, consisting of 20–44 cells arranged in 4–5 rows. Rows flattened, not separating, united by a 4–5 µm wide, pale brown, cubical, truncate basal cell. The outer rows are usually shorter. The terminal cells of the inner rows are usually larger than other cells in the conidium. The apical cells of the outer two rows are provided with an appendage which is hyaline, thin-walled, cylindrical, membrane borne, 1–2 celled, constricted at septum, measuring 24–51 × 6–10.5 µm.

 

Culture characteristics: Colonies on CMA reaching 1.5 cm diameter after 1 week at room temperature (~23 ^oC), cottony, with abundant aerial mycelium, margin entire, white from above, reverse pale yellow. Hyphae up to 3 µm wide, flexuous, hyaline, smooth-walled, septate, branched and sterile after 3 months incubation.

 

Material examined: CHINA, Yunnan, Tangchi, on submerged wood, 21 June 2002, L. Cai, HKU(M) 17156; living culture in HKUCC 9176. Paratype: China, Yunnan, Tangchi, on submerged wood, 21 June 2002, L. Cai, HKU(M) i7157.

 

Notes: Dictyosporium canisporum is distinct in having pluricellular conidia with two hyaline, constricted, long and massive appendages borne from the two outer rows of the conidia. The pluricellular appendages with constriction at septa have not been observed in other species of Dictyosporium. D. canisporum is most comparable to D. alatum Emden (Emden, 1975), which has complanate and similarly shaped conidia composed of 5 rows of cells. Dictyosporium canisporum, however, is distinguished in having conidia with 4-5 rows of cells; the conidia are consistently darker, longer (32.5–47.5 × 20–25 µm vs. 26–32 × 15–24 µm) and have larger appendages (24–51 × 6–10.5 µm vs. 20–25 × 5 µm).

 

References

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

Emden JH van (1975). Three new species from Surinam soil. Acta Botanica Neerlandica 24: 93–197.

 

Figs 1-5. Interference contrast micrographs of Dictyosporium canisporum (from holotype). 1. Squash mount of sporodochium with conidia, 2–5. Conidia with appendages (arrowhead). Note the appendages constricted at septa (arrowhead) in 3, 4 and 5, 2. Conidia attached to conidiophore, 4. Side view of conidium. Scale bars: 1 = 40 µm, 2–5 = 20 µm. (Goh et al. 1999)

 

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