Pycnopulvinus aurantiacus Toome & Aime

Toome, Merje & Aime, M. Catherine, 2014, Pycnopulvinusaurantiacus gen. et sp. nov., a new sporocarp-forming member of Pucciniomycotina, MycoKeys 8, pp. 43-50 : 47-49

Taxon classification Fungi Heterogastridiales Heterogastridiaceae

Pycnopulvinus aurantiacus Toome & Aime sp. nov. Figure 2

Diagnosis.

Sporocarps minute, orange, with a swollen basal cushion (up to 3 mm wide) and long narrow neck (up to 3 mm long) subtended by a light yellow to orange mucous droplet (up to 1.5 mm diam.) of hyaline, 2-4 celled spores, averaging 3.25 × 11.8 μm. Found on palm leaf litter.

Type.

ECUADOR. Manabi Division, near Bilsa Biological Station, in the vicinity of N0.350444, W79.732075, on palm leaf mid-rib in the litter, 3 May 2004, M.C. Aime, MCA 2548 (holotype PUL F2679; isotype QCA). GenBank no. KJ676978 (ITS), KJ676979 (LSU).

Description.

Gregarious, light to dark orange (ca. 5A6-7), superficial, stilboid sporocarps with swollen globose base (0.5-3 mm wide in fresh specimen, drying to 0.2-1 mm), surrounded by hyphae with globular apical cells, 20-30 μm wide and 45-55 μm long. Sporocarp necks erect, long (0.5-2 mm), narrow (up to 110 μm at base, 50-70 μm at middle and widening up to 130 μm at tip), tubular, light yellow to orange, smooth. Hyphae on the outer layer of the neck 5 μm wide, septate; hyphae at the base and inside the neck 2-2.5 μm wide, septate. Ostiolar hyphae extend from the outer layer of the neck cells, hyaline, non-septate, 10-12 μm wide, narrowing at the tip. Clamp connections not observed. Spores accumulate in pale to orange mucous droplets at tips of sporocarp necks, approximately half of the size of the basal cushion in diam. (up to 1.5 mm diam. in fresh material). Spores hyaline, mostly 2-4 celled and cylindrical or somewhat fusiform, measuring 3-4 × 7-18 μm (average 3.25 × 11.8 μm), breaking into smaller compartments. No sporogenous cells were detected at the interior of the sporocarp, but the spores are likely asexually produced. Basidia not observed.

Ecology and distribution.

On palm leaf litter in tropical forest of Ecuador. Possibly occurring in association with other fungi. Known only from the type locale.

Etymology.

aurantiacus = orange, for the color of fresh sporocarps.

Specimens examined.

PUL F2679.

Discussion.

The sporocarps most likely represent an asexual stage of Pycnopulvinus aurantiacus . Anamorphic stilboid conidiomata have been described for other members of Pucciniomycotina, especially in Atractiellomycetes (e.g. Oberwinkler et al. 2006). However, multicellular spores have not previously been described for any sporocarp-forming member of Atractiellomycetes or Microbotryomycetes. The organic matter of palm trees is not a common substrate among Pucciniomycotina and only one other basidiocarp-forming genus, Agaricostilbum Wright, is known to specifically inhabit palm litter ( Wright et al. 1981). The recovery of Ceratocystis paradoxa from the material might hint on a possible mycoparasitic strategy for Pycnopulvinus aurantiacus .