Catenularia minor (Hol.-Jech.) Reblova & A.N. Mill., 2021

Reblova, Martina, Nekvindova, Jana & Miller, Andrew N., 2021, Phylogeny and taxonomy of Catenularia and similar fungi with catenate conidia, MycoKeys 81, pp. 1-44 : 1

Catenularia minor (Hol.-Jech.) Reblova & A.N. Mill. comb. nov. Fig. 6

Catenularia cuneiformis minor Basionym. Catenularia cuneiformis var. minor Hol.-Jech., Česká Mykol. 37: 14. 1983.

Chaetosphaeria trianguloconidia Synonym. Chaetosphaeria trianguloconidia Réblová & Seifert, Sydowia 55: 333. 2003.

Description.

Colonies on the natural substrate effuse, tufted or hairy, dark brown to black, mycelium partly immersed, partly semi-immersed, pale brown to brown; colonies composed of conidiophores, capitate hyphae and sometimes ascomata. Anamorph. Conidiophores macronematous, solitary or arise in tufts, with dark brown stromatic hyphal cells around the base, erect, straight or flexuous, unbranched, thick-walled, paler towards the apex, forming two layers. Conidiophores of the lower layer 95-212 × 3.5-4.5(-5) μm, 4.5-5.5(-8.5) μm wide above the base, pale brown to brown; conidiophores of the upper layer 260-527 × 4.5-7 μm long, 7.5-10 μm wide above the base, dark brown. Capitate hyphae 122-186 × 3.5-5 μm, 5-5.5 μm wide above the base, scattered among the conidiophores, erect, straight, brown, extending percurrently, paler towards the apex, apical cell subhyaline, slightly swollen, 3.5-4 μm wide, broadly rounded, thin-walled; the hyaline gelatinous cap was not observed. Conidiogenous cells 15-40 × 3.5-5.5 μm tapering to 2.5-3 μm below the collarette, integrated, terminal, monophialidic, extending percurrently, cylindrical to slightly lageniform, pale brown to brown, producing conidia successively; collarettes 3.5-5(-6) μm wide, 1.5-2.5 μm deep, shallow, funnel-shaped, pale brown to subhyaline, smooth, margin entire. Conidia (6.5-)7.5-10.5(-13) μm long, 6.5-11.5 μ wide at the apical end, 1.5-2.5 μm wide at the base (mean ± SD = 8.9 ± 0.9 × 9.0 ± 1.2 × 2.1 ± 0.2 μm), cuneiform to rounded-obconic to obtriangular in side view, with 3-5 blunt corners when viewed from above, broadly rounded to flattened at the apex, truncate at the basal scar with a central pore, aseptate, pale brown to dark brown, thick-walled, smooth; formed singly, adhered in basipetal chains or clusters. Teleomorph. Ascomata 230-250 μm diam, 250-275 μm high, superficial, solitary or densely aggregated, subglobose to globose, covered by a whitish-grey powder except for the black glabrous papilla; the powdery covering is ca. 5-15 μm thick, disappearing with age, leaving the perithecia dark and glabrous. Ascomata sparsely covered with conidiophores. Ostiole periphysate. Ascomatal wall fragile, carbonaceous, 30-37.5 μm thick, two-layered. Outer layer consisting of dark brown, opaque, thin-walled, polyhedral cells. Inner layer consisting of hyaline, thinner-walled, elongated, compressed cells. Paraphyses 3-4 μm wide, tapering to ca. 2 μm, branching, anastomosing, septate, hyaline, longer than asci. Asci 102-112 × 8-9(-9.5) μm (mean ± SD = 106 ± 1.6 × 8.9 ± 0.2 µm), cylindrical-clavate, short-stipitate, rounded apically, ascal apex with a non-amyloid apical annulus 3 μm diam, 1.5-2 μm high. Ascospores 25-29(-30) × (3.5-)4-4.5 μm (mean ± SD = 27 ± 0.5 × 4 ± 0.7 µm), fusiform, straight or curved, hyaline, 1-3-septate, smooth, 1-2-seriate in the ascus (adapted from Réblová and Seifert 2003).

Specimens examined.

Cuba - Sancti Spiritus province • Soledad , Cienfuegos Province Botanical Garden ; on decaying stem of Bambusa vulgaris ; 19 Mar. 1981; M.A. Bondarceva & S. Herrera (holotype of C. cuneiformis var. minor PRM 828704) . Thailand - Nakhon Nayok Province • Khao Yai National Park, trail to Haew Suwat waterfall, elev. 720 m; on decaying bamboo culm; 2 Sep. 2001; M. Réblová, Gary J. Samuels & R. Nasit M.R. 2186/TH 438 (holotype of Ch. trianguloconidia PRM 900544) .

Habitat and geographical distribution.

Saprobe on dead culms of bamboo, known in Cuba and Thailand ( Holubová-Jechová 1983; Réblová and Seifert 2003).

Notes.

For characteristics in culture, see Réblová and Seifert (2003). The apparent similarity of C. cuneiformis var. minor ( Holubová-Jechová 1983) and Ch. trianguloconidia ( Réblová and Seifert 2003) and their habitat on dead bamboo culms prompted a revision of both species. Examination of their holotypes revealed that they are conspecific. Additionally, we discovered capitate hyphae in the type material of both species, although they were not described in the protologues. They are scattered among the conidiophores and easy to overlook. The hyaline gelatinous cap around the swollen apex of the capitate hyphae was not observed. Conidia slightly vary in size and colour, and often smaller and pale brown conidia occur together with slightly larger and darker brown conidia.

Holubová-Jechová (1983) distinguished var. Catenularia cupulifera minor from var. Catenularia cupulifera cuneiformis (= C. cupulifera , this study) in shorter collarettes, smaller conidia and the absence of capitate hyphae. Based on their different morphology, a new combination for var. Catenularia cupulifera minor is proposed at the species level with Ch. trianguloconidia reduced to synonymy.

Catenularia angulospora is similar to C. minor , and it is challenging to distinguish both species, especially if capitate hyphae may rarely occur in some specimens of the latter species. Catenularia angulospora differs in fuscous to brown conidia that are narrower (4.5-6(-7)) μm and the lack of capitate hyphae. Catenularia cupulifera is comparable to C. minor but differs in larger collarettes (9.5-12.5 μm wide and 10-12.5 μm deep) with a frayed margin, and longer (10.5-13.5 μm) conidia that are wider (3.5-4.5 μm) at the basal hilum. Conidia of C. cupulifera are cuneiform in side view, whereas conidia of C. minor are more rounded-obconic to obtriangular.

Figures

Figure 6. Catenularia minor A, B colonies composed of ascomata, conidiophores and capitate hyphae C ascus with ascospores D-F conidiophores with capitate hyphae G-J upper parts of conidiophores with conidia in chains J capitate hypha K, L conidia (arrow indicates central pore in the basal scar). Images: PRM 828704 holotype of C. minor (D, E, G, K); PRM 900544 holotype of Ch. trianguloconidia (A-C, F, H-J, L); on natural substrate (A-L). Scale bars: 250 μm (A, B); 10 μm (C, G-L); 50 μm (D-F).