Mimeomyces digitatus W. Rossi & M. Leonardi, sp. nov.

Index Fungorum number: IF 557385; MycoBank number: MB 557385; Facesoffungi number: FoF 07845; Fig. 1

Etymology – From Latin: bearing a finger, because of the finger-like preapical outgrowth.

Holotype – FI WR3388

Receptacle almost wholly blackened, with the basal cell pale yellow to almost hyaline above the foot; the rest of the thallus is yellowish brown, darker just above the receptacle and paler in the distal portion of the branchlets of the appendages; the preapical outgrowth of the perithecium is chestnut brown. Basal cell of the receptacle relatively large, obconical, slightly inflated above the foot. Suprabasal cell very short, irregularly pentagonal. Axis of the appendage consisting of five superimposed cells subequal in length but progressively narrower, bearing on the inner side short, erect, relatively stout branchlets, most of which are bifurcate from the base. Antheridia not seen. Stalk cell of the perithecium oblique, distinctly broader than long. Basal cells of the perithecium relatively large, subequal, distinctly longer than the stalk cell. Perithecium oblong, nearly symmetrical, slightly inflated below, the septa between the wall cell tiers marked by slight elevations, the tip rather abruptly tapering to a subtuncate apex bearing tiny hyaline lips and a subapical long, slender, straight outgrowth pointing obliquely upwards. Length from foot to perithecial apex 295–310 µm; from foot to tip of longest appendages 160 µm; perithecium 35–37×195–205 µm; perithecial outgrowth 35 µm.

Material examined – ECUADOR, Napo, near Papallacta, Rio Guango, 2714 msl, 00°22′35″ S 78°04′29″ W, 29 July 2009, W. Rossi and J.A. Torres Celi, on styla of Philonthus sp. (Coleoptera, Staphylinidae, Staphilininae, Philonthini) (FI WR3388, holotype).

Notes – Because of the long, straight and nearly erect preapical outgrowth, the new species can be easily distinguished from the 16 others in the same genus, 9 of which bear no outgrowth at all (Fig. 1). To date, the only species of Mimeomyces reported from Ecuador were M. latonae (Proaño Castro and Rossi 2008) and M. gregarius (Rossi 2010), both of which lack any preapical outgrowth; the latter is also the only species associated with Philonthus, all the others being parasitic on Staphylininae Quediini, except M. latonae occurring on Paederinae (Tavares 1985).

Figure 1 – Mimeomyces digitatus (FI WR3388, holotype). a, b Thalli from the type slide. Scale bars: a, b=100 µm