Malbranchea sedimenticola Guerra-Mateo, Cano & Gené, 2025

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

Fig. 9 View Figure 9

Etymology.

Latin sedimentum, settling, and Latin - cola, to inhabit, referring to the species’ preference for soil and sediment substrates.

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- 25615 , ex-type FMR 19564 View Materials , CBS 152723 View Materials ) GoogleMaps .

Description.

Saprobic on marine sediments. Mycelium superficial and immersed, composed of septate, branched, hyaline, smooth-walled, 1.5–2.5 µm wide hyphae. Asexual morph with intercalary or terminal fertile hyphae growing directly from the vegetative hyphae, often anastomosed, straight, slightly branched, branches short and sinuous, forming arthroconidia randomly, 1.5–2.5 µm wide. Arthroconidia enteroarthric, intercalary or terminal, 0–1 - septate, hyaline, smooth- and thin-walled, cylindrical to subcylindrical or T-shaped, (2.5 –) 4.5–5.5 (– 7.5) × 1.5–2.5 µm; secession rhexolytic. Sexual morph homothallic. Gymnothecia observed on OA, superficial, single or aggregated, orange-brown, globose to subglobose, 350–450 µm diam. (excluding appendages); peridium composed of a conspicuous network of hyphae, septate, branched, hyaline to brownish orange, asperulate, thick-walled, cylindrical, 2.5–3 µm wide, with short and long lateral appendages; short appendages arising at acute angles, spine-like, with subacute to truncated ends, orange-brown, asperulate, 15–40 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 a basal knuckle-joint, 500–850 µm long. Asci 8 - spored, evanescent, irregularly disposed, globose, subglobose, or pyriform, 7.5–9 × 5.5–6 µm. Ascospores unicellular, pale yellow, smooth-walled to slightly echinulate (reticulation regular with smooth polygonal meshes under SEM), thick-walled, globose, 2.5–3 µm diam.

Culture characteristics

(after 14 days at 25 ° C). Colonies on OA reaching 40 mm diam., flat, glabrous at center with abundant ascomata, white (1 A 1), producing sparse aerial mycelium towards periphery; reverse uncolored. On PDA, 46–50 mm diam., slightly umbonate, cottony, light yellow (4 A 4) to white at periphery, margin entire and diffuse; reverse reddish orange (7 B 8) to light orange (5 A 4), white towards periphery. On PYE, 47 mm diam., slightly umbonate, cottony or glabrous ( CBS 319.61 ), white (1 A 1), with light yellow patches at center, margin entire and diffuse; reverse uncolored. Diffusible pigment not observed in any of the media studied.

Additional specimens examined.

Spain • Catalonia, Mediterranean coast, Tarragona, Platja de la Arrabassada , 41°6'45"N, 1°16'51"E, from sediments at 27 m depth, June 2022, G. Quiroga-Jofre & D. Guerra-Mateo ( FMR 20150 View Materials ) GoogleMaps ; • ibid., Barcelona, discharging area of the Llobregat River , 41°17'20´´N, 2°9'16´´E, from sediments at 19 m depth, October 2023, P. Rojas & D. Guerra-Mateo ( FMR 21121 View Materials ) GoogleMaps ; the USA, California, Stanislaus Co., on soil, G. F. Orr ( CBS 319.61 View Materials ) .

Cardinal temperatures for growth.

Minimum 5 ° C ( 3 mm), optimum 25 ° C ( 50 mm), maximum 37 ° C ( 17 mm).

Habitat and geographic distribution.

Marine sediments and soil in Spain and the USA. In GlobalFungi, in soil from different environments (forest, shrubland, grassland, desert, cropland, and urban), rhizosphere soil, roots, and marine sediment. Australia, Chile, China, Mexico, Morocco, Oman, Qatar, and Tunisia (Fig. 4 View Figure 4 ).

Notes.

Malbranchea sedimenticola is phylogenetically related to M. sinuata and M. albolutea (Fig. 3 View Figure 3 ). These species can be distinguished based on colony colour and arthroconidia size. On OA and PYE, M. sedimenticola displays white mycelium, while M. albolutea produces colonies in shades of pale yellow and M. sinuata in shades of yellow to orange and reddish brown. Microscopically, the three species produce the characteristic sinuous fertile hyphae of Malbranchea but differ in arthroconidia length, M. sedimenticola [(2.5 –) 4.5–5.5 (– 7.5) µm], M. albolutea [(1.5 –) 2–5 (– 6.5) µm] ( Sigler and Carmichael 1976), and M. sinuata (1.5–3 µm) ( Torres-Garcia et al. 2023). In addition, only M. sedimenticola and M. albolutea produce the sexual morph, resembling that of the phylogenetically distant species M. thaxteri . The ascomatal peridium consists of yellow to brownish-orange, asperulate hyphae that produce short, spine-like appendages and long, straight to uncinate appendages, subglobose asci, and globose ascospores of 2.5–3 µm diam. Although the sexual morphs of M. sedimenticola and M. albolutea are morphologically similar, they can be distinguished from M. thaxteri by showing longer appendages (500–850 µm and 400–800 µm vs. 252–542 µm, respectively) and smooth to slightly echinulate ascospores under a bright field microscope ( Sigler and Carmichael 1976), while M. thaxteri ascospores are echinulate-reticulate.

It is worth mentioning that the strain CBS 319.61 was formerly identified as M. thaxteri , probably based on ascomata morphology. Although this strain remained sterile throughout the culture media assessed in this study, our phylogenetic analyses support the classification of CBS 319.61 as M. sedimenticola (Figs 2 View Figure 2 , 3 View Figure 3 ).