Malbranchea seminuda Guerra-Mateo, Cano & Gené, 2025

Malbranchea seminuda Guerra-Mateo, Cano & Gené sp. nov.

Fig. 10 View Figure 10

Etymology.

Latin semi -, half, and Latin nūda, naked, referring to the ascomata with slightly differentiated peridial hyphae.

Type.

Spain • Catalonia, Mediterranean coast, Tarragona, Platja del Miracle , 41°6'6"N, 1°15'44"E, from sediments at 27 m depth, June 2021, G. Quiroga-Jofre & D. Guerra-Mateo ( holotype CBS H- 25614 , ex-type FMR 19403 View Materials , CBS 152722 View Materials ) GoogleMaps .

Description.

Saprobic from marine environment. Mycelium superficial and immersed, composed of hyaline, septate, branched, smooth-walled, 2.5–3 µm wide hyphae. Asexual morph with straight, branched, cylindrical, 2.5–3 µm wide fertile hyphae, giving rise to arthroconidia in a random disposition. Arthroconidia enteroarthric, 0–1 - septate, hyaline, smooth- and thin-walled, cylindrical to subcylindrical or T-shaped, (4 –) 12–13 (– 14.5) × 2.5–3 µm; secession rhexolytic. Sexual morph homothallic. Gymnothecia observed in all media tested, superficial, aggregated, white to pale yellow, turning pale orange-brown in old cultures (8 weeks), globose to subglobose, 350–500 µm diam.; peridium composed of a subtle network of hyphae, septate, branched, hyaline to pale yellow, verruculose to verrucose (tuberculate under SEM), 2.5–3 µm wide. Asci 8 - spored, evanescent, irregularly disposed, subglobose or pyriform, 11.5–14 × 9–10.5 µm. Ascospores unicellular, pale yellow, reticulate (reticulation regular with polygonal meshes and conspicuous ridges under SEM), thick-walled, globose, 4–5 µm diam.

Culture characteristics

(after 14 days at 25 ° C). Colonies on OA reaching 30 mm, flat, with sparse white aerial mycelium at center and glabrous towards periphery, margin diffuse, ascomata abundant and densely aggregated in a concentric ring; reverse uncolored. On PDA, 37 mm diam., slightly floccose, with concentrical rings, greenish yellow (1 A 6), margin entire and diffuse, ascomata abundant arranged in concentric rings; reverse brownish yellow (5 C 8) at center, yellowish brown (5 E 8) and yellowish white (1 A 2) at periphery. On PYE, 44 mm diam., slightly raised with concentrical rings, radially sulcate, floccose, white (1 A 1) to greenish yellow (1 A 6), margin entire, submerged in the medium, ascomata abundant arranged in concentric rings; reverse uncolored. Diffusible pigment not observed in any of the media studied.

Cardinal temperatures for growth.

Minimum 5 ° C ( 1 mm), optimum 25 ° C ( 37 mm), maximum 30 ° C ( 24 mm).

Habitat and geographic distribution.

Marine sediments in Spain. In GlobalFungi, in soil from different environments (forest, shrubland, and grassland) and marine and terrestrial sediments. Germany, Greece, the Netherlands, South Africa, Spain, the USA, and Zimbabwe (Fig. 4 View Figure 4 ).

Notes.

Malbranchea seminuda is phylogenetically related to M. longispora and M. multiseptata (Fig. 3 View Figure 3 ). The three species produce an asexual morph consisting of hyaline and smooth-walled enteroarthric conidia. However, they differ in conidia disposition and size, with M. longispora showing straight chains of larger conidia (4–24 × 1–5.5 µm) ( Crous et al. 2013), M. seminuda displaying straight chains of medium-size conidia (4 –) 12–13 (– 14.5) × 2.5–3 µm, and M. multiseptata producing straight and sinuous chains of smaller conidia (3–9 × 1.5–2 µm) ( Rodríguez-Andrade et al. 2021). In addition, only M. seminuda and M. longispora produce sexual morphs, which differ in the peridium morphology; while the former species shows a subtle network of hyaline and verruculose to verrucose hyphae, M. longispora displays a conspicuous network of pale yellow to orange-brown, thick-walled, tuberculate hyphae ( Crous et al. 2013). Other phylogenetically distant species with ascomata morphologically similar to those of M. seminuda are M. concentrica and M. kuehnii . The three species can be distinguished by the ornamentation pattern of the peridial hyphae, being verrucose in M. seminuda and M. kuehnii but smooth-walled in M. concentrica ( Solé et al. 2002) . Malbranchea seminuda differs from M. kuehnii in the colour of the ascospores (pale yellow vs. hyaline, respectively) and colonies on PDA (greenish-yellow vs. brown, respectively) ( Solé et al. 2002).