Malbranchea sexualis Guerra-Mateo, Cano & Gené, 2025

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

Fig. 11 View Figure 11

Etymology.

Latin sexus, sex, referring to the exclusive presence of the sexual morph in the type strain.

Type.

Spain • Catalonia, Mediterranean coast, discharging area of the Ebro River , 40°44'21"N, 0°55'31"E, from sediments at 27 m depth, May 2023, Q. Roca & D. Guerra-Mateo ( holotype CBS H- 25617 , ex-type FMR 20852 View Materials , CBS 152726 View Materials ) GoogleMaps .

Description.

Saprobic on marine sediments. Mycelium superficial and immersed, composed of hyaline, septate, branched, smooth-walled, 1.5–2 µm wide hyphae. Racket hyphae present. Asexual morph not observed. Sexual morph homothallic. Gymnothecia observed on OA, superficial, single or confluent, pale yellow, globose to subglobose, 250–420 µm diam. (excluding appendages); peridium composed of a conspicuous network of hyphae, septate, branched, hyaline to orange-brown, asperulate, thick-walled and cylindrical, 3–4.5 µm wide, with short and long lateral appendages; short appendages arising at acute angles, spine-like, with subacute to rounded ends, orange-brown, finely asperulate, 15–25 µm long; long appendages arising from peridium at acute and subacute angles, unbranched, straight or curved, cylindrical, progressively tapering terminally, orange-brown, asperulate and thick-walled toward the base, paler and smooth terminally, with a rounded or subacute curved apex and mostly with a basal knuckle-joint, 150–340 µm long. Asci 8 - spored, evanescent, irregularly disposed, globose, subglobose, or pyriform, 6–8 × 4.5–5.5 µm. Ascospores unicellular, pale yellow, smooth-walled to slightly echinulate (reticulation regular with smooth polygonal meshes under SEM), thick-walled, globose, 2–2.5 µm diam.

Culture characteristics

(after 14 days at 25 ° C). Colonies on OA reaching 20 mm diam., flat with sparse aerial mycelium, yellowish white (4 A 2) at initial stages, brownish yellow (5 C 7) when mature, margin entire, ascomata abundant and densely aggregated in center; reverse orange (5 B 8) to pale orange (5 A 3). On PDA, 22–26 mm diam., crateriform, radially sulcate at periphery, light orange to orange, velvety, margin entire to slightly lobate; reverse brownish orange (7 C 8) at center, deep yellow (4 A 8) towards periphery. On PYE, 26–28 mm diam., elevated, slightly crateriform, radially sulcate, velvety, deep yellow (4 A 8) at center, light orange (5 A 5) towards periphery, margin entire, slightly lobate; reverse brownish orange (7 C 8) to deep yellow (4 A 8). Diffusible pigment not observed in any of the media studied.

Cardinal temperatures for growth.

Minimum 5 ° C ( 1.5 mm), optimum 25 ° C ( 22–26 mm), maximum 30 ° C ( 14 mm).

Habitat and geographic distribution.

Marine sediments in Spain. In GlobalFungi, in rhizosphere soil and soil from different environments (forest, woodland, shrubland, grassland, desert, wetland, cropland, and urban), marine sediment, aquatic plant shoots, terrestrial plant shoots and roots. Australia, China, England, Estonia, Finland, Germany, Russia, Spain, Sweden, Tunisia, and the USA (Fig. 4 View Figure 4 ).

Notes.

Malbranchea sexualis represents an independent lineage phylogenetically related to M. gymnoascoides , M. ostraviensis , M. phuphaphetensis , and M. umbrina (Fig. 3 View Figure 3 ). Macroscopically these species are characterized by the production of colonies in shades of yellow and orange, with M. ostraviensis being characterized by the production of a reddish diffusible pigment on MEA, PDA, and PCA that has not been observed in the other species. Regarding the reproductive structures, M. sexualis is characterized by exclusively producing the sexual morph, while M. phuphaphetensis is only known by its asexual morph ( Preedanon et al. 2023). On the other hand, M. gymnoascoides , M. ostraviensis , and M. umbrina produce both sexual and asexual morphs. The species that display sexual morph produce gymnothecia with similar features (i. e., yellow to brownish orange, asperulate peridial hyphae with short spine-like appendages and long appendages, globose to pyriform asci, and globose ascospores), but can be distinguished by the length of the peridial appendages and ascospore ornamentation. Malbranchea umbrina displays the shortest appendages (5–72 µm) and reticulate ascospores ( Hubka et al. 2013), M. ostraviensis displays the longest appendages (350–600 µm) and smooth (reticulate with a central depression under SEM) ascospores ( Hubka et al. 2013), and both M. sexualis and M. gymnoascoides produce appendages of overlapping length (150–340 µm vs. 250–400 µm, respectively; Rodríguez-Andrade et al. 2021), but differ in ascospore ornamentation. While the ascospores in M. gymnoascoides are smooth-walled ( Rodríguez-Andrade et al. 2021), those of M. sexualis are smooth to slightly echinulate (reticulate under SEM). Although we have not observed the asexual morph for M. sexualis in any of the media tested, the great phylogenetic distance and the morphological characters of the sexual morph confirm it as a novel species.