Mycelephas robustus (R.F. Castañeda) R.F. Castañeda, Mycotaxon

Miglio, Beatriz Valente & Monteiro, Josiane Santana, 2022, Mycelephas robustus (Ascomycota incertae sedis) rediscovered in the Amazon after 37 years, Phytotaxa 544 (3), pp. 295-300 : 296-297

Mycelephas robustus (R.F. Castañeda) R.F. Castañeda, Mycotaxon 110: 90 (2009). Fig. 2

Basionym: Arnoldiella robusta R.F. Castañeda, Revta Jardín bot. Nac., Univ. Habana 5(1): 60 (1984).

Colonies on natural substrate effuse, granulate, yellow to yellowish brown, aggregated. Mycelium partly superficial, partly immersed in the substrate, composed of branched, septate, brown, smooth-walled hyphae. Conidiophores macronematous, mononematous, erect, simple or branched, straight or slightly flexuous, cylindrical, septate, sometimes with 1 enteroblastic regeneration, smooth, brown to dark brown, 20–300 × 6–7.5 µm (x̅ = 201.5 × 6.7, n = 30). Conidiogenous cells mono- or polyblastic, integrated, terminal or intercalary, sympodial, cylindrical, with slightly dark scars, smooth, pale brown, 7.5–27.5 × 2–5 µm (x̅ = 15.1 × 2.7, n = 30). Conidial secession schizolytic. Conidia solitary, dry, helicoidal, 6–8 septa in the main filament, slightly constricted at septa, smooth to rugose, subhyaline to pale brown, 4–7 µm (x̅ = 5.5, n = 30) width. Bifurcated filament in two branched coils, coiled 1–1 ½ times giving an almost cochleate appearance, 5–8.5 µm (x̅ = 6.1, n = 30) diam. Mature conidia 18.5–30 × 17–25 µm (x̅ = 19.7 × 22.8, n = 30) in frontal view, 15–23.5 × 13–21 µm (x̅ = 17.6 × 15.3, n = 30) in side view. Basal cell conical, truncated, 4.5–6.5 × 4–5 µm (x̅ = 5.1 × 4.5, n = 30).

Material examined: — BRAZIL. Pará: Belém, Ilha do Combu (48º25′W, 1º25′S), on decaying rachises of Euterpe oleracea Mart. (Arecaceae) , 2 December 2020, B.V. Miglio & J.S. Monteiro (MG 241763) ; idem, on decaying petioles of E. oleracea , 2 December 2020 , idem, J.S. Monteiro (MG 241541) ; idem, on decaying rachises of E. oleracea , 24 June 2021 , idem, B.V. Miglio-117 (MG 241542) .

Life mode and habitat: —saprotrophic species found on dead bark of Bursera simaruba (L.) Sarg. ( Burseraceae ) and on decaying rachises and petioles of E. oleracea (Arecaceae) .

Distribution: — Cuba ( Castañeda-Ruiz 1984). Cited for the first time from Brazil.

Notes: —According to literature, M. robustus is regarded as a rare species with a restricted distribution to the place of collection of the holotype. This species differs from M. levisporus by smaller and rugose conidia with more septa (6–11) ( Castañeda-Ruiz 1984, Cantillo-Pérez et al. 2017). The Brazilian specimens showed conidiophores and conidiogenous cells with larger dimensions than those recorded for the Cuban collection. Conidia were also slightly larger in relation to the type material, but had fewer septa. The differences in dimensions reflect the substrates and environmental conditions where the specimens were collected ( Table 1 ). Unfortunately, it was not possible to obtain cultures of M. robustus in this study. Castañeda-Ruiz (1984) obtained colonies of this fungus on cornmeal agar with similar dimensions to those of the material on natural substrate ( Table 1 ). Some differences are perceptible in the morphology of conidia of M. robustus in pure culture being less compact and having smaller filaments. The illustrations and photomicrographs presented by Castañeda-Ruiz (1984) and Gams et al. (2009) clearly show these differences.

Figures

FIGURE 2. Mycelephas robustus. a–b.Colonies on natural substrate.c. Conidia. d. Conidiophores. e. Branched conidiophore.f.Formation of conidia on the conidiogenous cells. g. Polyblastic conidiogenous cell with conidia. h. Superficial view of conidia with rugose wall (SEM). Scale bars: a = 0.1 mm, b = 0.2 mm, c = 20 µm, d–e = 50 µm, f = 20 µm, g = 10 µm, h = 5 µm.