Ceratostomella melanospora Réblová, 2024

Réblová, Martina, Nekvindová, Jana, Kolařík, Miroslav, Jurjević, Željko, Kolář, Michal & Hubka, Vít, 2024, Re-evaluation of Ceratostomella and Xylomelasma with introduction of two new species (Sordariomycetes), MycoKeys 110, pp. 319-360 : 319-360

Ceratostomella melanospora Réblová , sp. nov.

Figs 7 , 8

Etymology.

Melanos (Greek) meaning black, dark, spora (Latin) from Ancient Greek sporá, meaning a seed, referring to brown ascospores.

Type.

Czech Republic • Pardubice Region, Chrudim district, Železné hory Mts. Protected Landscape Area, Horní Bradlo, Malá Střítež settlement , Polom National Nature Reserve; 600 m alt.; on decaying wood of Fagus sylvatica ; 9 Oct 2020; M. Réblová M. R. 4088 (holotype PRA -21822 !, ex-type culture CBS 147993 ) .

Description.

Sexual morph. Ascomata non-stromatic, densely grouped or solitary, superficial, semi-immersed or immersed with only neck protruding. Venter 300–480 µm diam, subglobose, upright or lying horizontally in the host tissue, dark brown to black, with brown, septate, slightly flexuous hairs 2.5–4 µm wide sparsely covering the sides and bottom. Neck 90–100 µm wide, up to 500 µm long, central, cylindrical, upright, glabrous, tapering, apex sulcate; the neck is sometimes slightly wider near the top. Ostiole periphysate. Ascomatal wall fragile to leathery, 55–65 µm thick, two-layered. Outer layer consisting of thick-walled, dark brown, polyhedral cells with opaque walls of textura prismatica, with several cells forming the external crustose layer ca. 8–13 µm thick, cells tend to be more flattened and paler towards the interior. Inner layer consists of several rows of thin-walled, hyaline, flattened cells. Paraphyses abundant, longer than the asci, may become partially disintegrated with age, septate, constricted at the septa, hyaline, (5 –) 6.5–10.5 µm wide, wider near the base, tapering to 3–4 µm. Asci 63–78 × 6.5–8 (– 8.5) µm (mean ± SD = 70.8 ± 4.2 × 7.2 ± 0.7 μm), 51–60 (– 62.5) µm (mean ± SD = 57.0 ± 3.3 μm) long in the sporiferous part; truncate at the apex, cylindrical, with a short tapering stipe, apical annulus non-amyloid, ca. 2.5 µm wide, 1–1.5 µm high, 8 - spored. Ascospores (8 –) 8.5–10.5 (– 11) × 4–5 µm (mean ± SD = 9.3 ± 0.7 × 4.5 ± 0.3 μm), ellipsoidal, slightly apiculate at both ends, brown, aseptate, smooth, with an inconspicuous germ pore at one or both ends, occasionally with one oil drop, often collapsing, obliquely uniseriate or partially overlapping, or partially 2 - seriate within the ascus. Asexual morph. Unknown.

Culture characteristics

(after 2 / 4 wk at 23 ° C). On CMD colonies 30–32 mm / 64–70 mm diam, circular, flat, margin diffuse, cobwebby, mucoid towards the margin, dark brown, with an outer beige zone of conspicuous submerged growth, reverse of the same colour. On MLA colonies 20–21 mm / 48–50 mm diam, circular, flat margin fimbriate to somewhat lobate, floccose and whitish grey centrally, cobwebby to mucoid and dark olivaceous grey towards the periphery, reverse of the same colour. On OA colonies 28–30 mm / 73–75 mm diam, circular, flat, margin diffuse, lanose and pale olivaceous grey at the centre, sparse to cobwebby and olivaceous black towards the margin, reverse dark brown. On PCA colonies 17–18 mm / 53–54 mm diam, circular, flat, margin rhizoidal, submerged, floccose and beige-grey centrally, cobwebby and dark brown towards the margin, reverse dark brown. Sporulation was absent on all media.

Temperature dependent growth at 30, 35, 37, 41 ° C was assessed as colony diam on MEA, PDA, and OA, respectively, after a period of two weeks: 30 ° C 27–29 mm / 23–24 mm / 23 mm, 35 ° C no growth / no growth / no growth, 37 ° C no growth / no growth / no growth, 41 ° C no growth / no growth / no growth.

On MLA, colonies are effuse, with submerged hyphae 1–2 μm in diameter. These hyphae are hyaline to subhyaline, sparsely branched, septate, smooth, intertwined with vein-like dark brown hyphae, 3–4.5 μm in diameter. Monilioid hyphae were not observed.

Habitat and geographical distribution.

This species is a saprobe on decaying wood of Fagus sylvatica and is known to occur in the Czech Republic. According to GlobalFungi, identical sequences were identified in seven environmental samples obtained from various localities within the temperate zone of the Northern Hemisphere. These samples were primarily isolated from air and soil in cropland and forest biomes, with occasional findings in anthropogenic habitats in Canada, China, Italy, and Sweden.

Notes.

Ceratostomella melanospora is characterised by ellipsoidal, slightly apiculate, mid-brown ascospores arranged 1 - seriately, occasionally partially 2 - seriately in the ascus. The species is micromorphologically indistinguishable from C. crypta and C. sordida but differs by the colony characteristics and can also be clearly differentiated by ITS, rpb 2, and tef 1 - α sequences. Pigmented monilioid hyphae, which formed abundantly in the culture of C. crypta and to some extent in C. sordida , were not observed in C. melanospora (Fig. 8 ).

Figures

Figure 7. Ceratostomella melanospora (A – P from holotype PRA - 21822 Q from ex-type strain CBS 147993) A-C ascomata D a longitudinal section of the ascomatal wall E, F asci with ascogenous cells G paraphyses H ascal apex I stipe of the ascus J-M asci with ascospores N-O asci of different ages with maturing ascospores Q colony morphology at 23 ° C after 4 weeks on CMD, MLA, OA and PCA (from left to right). Images: on natural substrate (A-P). Scale bars: 500 μm (A-C); 20 μm (D); 10 μm (E-G, J-P); 5 μm (H, I); 1 cm (Q).

Figure 8. Vegetative mycelium of Ceratostomella spp. on MLA A, B C. melanospora CBS 147993 C-G C. sordida CBS 116000. Scale bars: 10 μm (A-G).