First person to use this name on MO: Image Sharer
On dung of Macropus: Tasmania
Pileus 5-10 mm broad, conico-convex or subcampanulate, viscid or slimy, slightly hygrophanous, glabrous, brownish orange (5C4-5) throughout, browner (6D5) at the disc, fading to pale buff. Lamellae subdecurrent, yellowish grey, then greyish brown. Stipe 18-52 × 1-1.5 mm, equal, viscid with a thin glutinous layer below the position of the veil, yellowish white (4A2), sub-bulbous at the base. Context thin, concolorous with pileus. Veil arachnoid, evanescent.
Spores 12.9-15.4 × 7.5-9.2 × 7.9-9.6 um, elongate ellipsoidal, germ pore broad. Basidia (18.3-) 21.7-35 × 9.2-19.2 um, 4-spored, clavate or pyriform. Pleurocystidia as chrysocystidia, 32.1-47.5 × 11.7-20 um, fusoid ventricose. Cheilocystidia 25.8-38.3 (-41.7) x (4.2-) 5-9.2 um, hyaline, lageniform or elongate clavate. Subhymenium subcellular. Trama regular, tending to interwoven near edge of lamellae, hyphae 2-16 um broad, pale yellowish brown (5% KOH). Epicutis a thin layer of gelatinised repent hyphae, 2-A um broad, bearing numerous clamp connections. Hypodermium a broad layer of encrusted, yellowish brown hyphae, 4-16 um broad, clamp connections present. Basal mycelium with acanthocytes.
Solitary on wallaby dung.
Holotype: Tasmania, Mt Field National Park, near car park, 27 June 1990, Y.S. Chang, CYS486 (HO300130).
Other specimens examined: Tasmania, near Nugent, on wallaby dung, 15 May 1990, Y.S. Chang, CYS364 (HO300864); Sandspit River Forest Reserve, past Robertson Bridge, Y.S. Chang, 23 April 1991, CYS526 (HO300131).
Comments: Although it might be mistaken for a diminutive form of a member of the Psilocybe semiglobata (Batsch : Fr.) Noordel. species group complex, the very slender, delicate habit of P. parvula sp. now, its sometimes faint pinkish hue to the pileus with a diameter seldom exceeding 10 mm, and its exclusivity to the dung of native animals, suggest that it differs from other coprophilous species. The spore size (12.9-15.4 × 7.5-9.6 irm) should separate it from the ‘typical’ P. semiglobata of "the Northern Hemisphere, whose spores measure 16-21 × 8.5-11 um (Noordeloos 1999) or 15-19 × 7.5-10 um (Arora 1986). Psilocybe semiglobata in Tasmania, as found in grazed paddocks and grasslands, usually has spores in the range 13-16.5 × 7.5-9.5 um, making them inseparable from those of P. parvula sp. nov.
Noordeloos (1999) synonymised Stropharia stercoraria (Schum. : Fr.) Quel. with P.semiglobata, as spore size was the only macroscopic character separating those two species. This suggests that P. parvula sp. nov. may just be a reduced form of the P. semiglobata species complex. However, evidence of a distinction between P. parvula and members of that complex derive from a study of isoenzyme patterns and mating compatibility trials (Chang 1992). In crosses between the isolates of two collections of this taxon with medium- and large-spored forms of S. stercoraria, negative pairings were always obtained. In addition, the isozyme patterns of P. parvula sp. nov. were always distinct from those of collections of the other coprophilous taxa. Therefore, we conclude that P. parvula sp. nov., despite the fact that canonical discriminant analysis of microscopic characters failed to separate this taxon from P. semiglobata, can be recognised as a biological species in the sense espoused by Taylor et al. (2000). It has so far been found on the dung of native animals only.
Etymology: parvulus = very small.