Arthromyces pulverulentus A. E. Franco-Molano, T. J. Baroni & L. J. J. van de Peppel 2024, sp. nov.
Creators: name: Franco-Molano, Ana E.
name: Baroni, Timothy J.
name: Van De Peppel, Lennart J. J.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Fungi
Basidiomycota
Agaricomycetes
Agaricales
Tricholomataceae
Arthromyces
Arthromyces pulverulentus

description: Arthromyces pulverulentus A.E. Franco-Molano, T.J. Baroni & L.J.J. van de Peppel, sp. nov. Fig. 2 A–F
Mycobank—MB851622
Etymology —from the powdery pulverulent pileus margin
Type — COLOMBIA. Antioquia: Municipio de Envigado, El Salado, sector de las Cuevas del Higuerón, 2400 m asl. 15 December 2023. Juan Carlos Quiroz Mejía s.n. (holotype HUA233518!, isotype NY04285950!). Genbank: ITS (PP294860), LSU (PP294858), TEF1α (PP278605).
Diagnosis— Arthromyces pulverulentus differs from A. claviformis, A. glabriceps and A. matolae, by the thick, white mycelioid roll around the margin of the pileus, producing dense brown pulverulent masses of arthroconidia in long chains, the arthroconidia surfaces are smooth and not ornamented as found in the other arthroconidia producing species A. claviformis and A. matolae, and the cheilocystidia are not encrusted in A. pulverulentus.
Description —Pileus 7–12 mm broad, plano-convex or slightly and broadly depressed, some become convexcampanulate, always with thickened rounded margin covered with dense cream gray (oac801) to cream (oac816) mycelioid roll at first, the thickened roll incurved and covering lamellae from margin or to mid pileus, then eventually covering the lamellae completely to the stipe, the marginal roll becoming pulverulent-powdery and turning olivaceous brown from arthroconidia production, disc surface black (oac908) to margin, glabrous, shiny or matte, smooth or becoming rugulose, solid and glass-like as dried. Context 1 mm thick, solid, dark gray (aoc901). Lamellae adnate with a decurrent tooth, close to subdistant, narrow (1 mm) white to grayish (oac909-893) at first, edges olivaceous and granulate-floccose. Stipe 35–70 mm long, 1.5–2 mm broad at apex, central, cylindrical, equal above ground, but gradually tapered to a long pseudorhizal base below ground level, surface fuscous-black but mostly covered over the upper portions at first or the entire above ground surface with fine white (oac909) velutinous pubescence that eventually turns olivaceous brown over the upper apical regions like the pileus marginal roll, pseudorhiza attached to ball shaped masses of insect faecal pellets composed of masticated plant materials, these faecal pellets bound together by white mycelium that produced the basidiomata.
Basidiospores 4–5 × (2–) 3–4 µm, (n= 23, L=4.6 ± 0.44, W=2.95 ± 0.45, Q = 1.25–2, QM = 1.6 ± 0.2), ellipsoid in profile and face views, round in polar view, smooth, walls thin cyanophilic. Basidia not abundant, (12–) 15–19 × 4–5 µm, cylindrical, 4-sterigmate, filled with small cyanophilic bodies when mounted in Cotton Blue and Congo Red droplets when mounted in Congo Red ammonia solution. Basidioles similar in dimensions to basidia, cylindrical or quite often fusoid, filled with cyanophilic bodies. Cheilocystidia 25–52 × 4–6 µm, narrowly clavate or more frequently cylindrical-capitate (capitulum 5–8 um broad), hyaline in NH 4 OH, with abundant, large shiny lipoidal bodies in Cotton Blue. Pleurocystidia absent. Lamella trama composed of parallel, cylindric hyphae, 2–6 (–10) µm broad. Pileipellis a dark brown layer in NH 4 OH, of repent cylindrical hyphae, 3–6 µm in diam, walls of hyphae fainty but distinctly encrusted with brown pigment, separating and producing a zebra like pattern on individual hyphae.
Clamp connections absent.
Arthroconidia on pileus margin dark olivaceous in NH 4 OH, often in long chains of 10–20 cells, individual conidia, thick-walled, mostly short or elongate rectangular, some curved, smooth, 3–6.5 (–7) × 3–3.5 (–4) µm.
Habit and habitat —solitary, on soil among pine needles, on insect pellet frass masses, apparently associated with an insect in its life cycle. April through December.
Additional material examined — COLOMBIA. Antioquia, municipio de Medellín, Corregimiento de San Antonio de Prado, Vereda Astilleros, Reserva Natural Astillera; bosque de niebla, 2500–2800 m asl (6.25425, -75.66986), 28 June 2022, Laura Vélez Jaramillo #37 (HUA 233492; CORT 014891); Antioquia, municipio de Medellín, Corregimiento de San Antonio de Prado, Vereda Astilleros, Reserva Limona-Manguala, cuchilla del Romeral. 2441.95 m asl, (6.171650, -75.756765), 15 November 2023, Juan Jose Celis #2 (HUA 233519); Antioquia, municipio de Envigado, El Salado, camino ancentral a Cuevas del Higueron, (6.12364612, -75.561523), 12 September 2021, Brayan Zora Vergara s.n. (HUA 227833); Antioquia, municipio de Medellin, Corregimiento de Santa Elena, vereda El Rosario, (6.245319, -75.493642237535), 26 May 2024, Juan Jose Celis #88 (HUA 237535).
Comments— Arthromyces pulverulentus differs from other species in the genus by its distinctive thick cottonypulverulent roll producing olivaceous-brown chains of arthroconidia around the pileus margin, and not on the disc of the pileus as typical for A. matolae and A. claviformis, the two other arthroconidia producing taxa in this genus (Baroni et al. 2007). Arthromyces glabriceps does not produce arthroconidia on its basidiomata (van de Peppel 2022a). The cheilocystidia of A. pulverulentus are also distinctive by lacking encrusting exudates that are found on the cheilocystidia of all the other species of Arthromyces described so far. Also, the arthroconidia produced by A. pulverulentus are smooth, not ornamented as is typical for the other arthroconidial producing taxa, A. matolae and A. claviformis. A final, and not insignificant difference, is that the basidiospores of A. pulverulentus are smaller than the other three taxa in this genus (i.e. A. claviformis — 4.5–6.5 x 3–4 µm; A. glabriceps —5–7.5 x 3–4 µm; A. matolae —5.5–7.5 x 3.4–4.5 µm: Baroni et al. 2007, van de Peppel et al. 2022a).
description: Published as part of Franco-Molano, Ana E., Baroni, Timothy J. & Van De Peppel, Lennart J. J., 2024, Arthromyces pulverulentus sp. nov. (Basidiomycota, Agaricales, Lyophyllaceae), a new insect associated conidia-producing species from the cloud forests of Colombia, pp. 271-278 in Phytotaxa 662 (3) on pages 274-276, DOI: 10.11646/phytotaxa.662.3.6, http://zenodo.org/record/14516053