Roridomyces austrororidus, commonly known as the austro dripping bonnet, is a species of agaric fungus in the family Mycenaceae. Described as new to science in 1962 by American mycologist Rolf Singer, it is found in Chile, New Zealand, and Australia, where it grows on rotting wood. The fruit bodies (mushrooms) have several distinguishing characteristics that facilitate identification, including thick, white, glutinous stems, and white to pale cream, convex caps that measure 1–2 cm (0.4–0.8 in). The gills are white, widely spaced, and have a fused or decurrent attachment to the stem. Spores are smooth, ellipsoid, and measure about 9–15 by 6–9 micrometres. The smooth and white stems are 4–6 cm (1.6–2.4 in) long and 0.1–0.2 cm (0.04–0.08 in) thick, and covered with a thick coating of gluten.
Taxonomy, naming, and classification
The species was first described as Mycena rorida by mycologist Rolf Singer in 1962, based on specimens he collected from Masatierra, in the Juan Fernandez Islands, Chile. It was transferred to the genus Roridomyces by Karl-Heinz Rexer in his 1994 doctoral thesis. The name Mycena veronicae, published by New Zealand mycologist Greta Stevenson in 1964, is a synonym. The mushrooms is commonly known as the "austro dripping bonnet".
The cap is shallowly convex to convex or irregularly convex, and with or without a shallow umbo, measuring up to 16 mm (0.63 in) in diameter and up to 5 mm (0.20 in) high. The cap margin is curved downward, sometimes slightly flared, and sometimes has translucent radial striations marking the positions of the gills underneath. The flesh is white, and thickest at the center of the cap, and tapers gradually to the margin. The gills are broadly adnate (fused) to decurrent (running down the length of the stem). The gill edges are either smooth and even, or may have minute teeth. The gills are well-spaced, with 16 to 24 gills extending fully from the cap margin to the stem, and two or three tiers of interspersed lamellulae (short gills that do not extend fully from the cap margin to the stem). The stem is up to 27 mm (1.1 in) long, and up to 2.5 mm (0.1 in) in diameter at the base, narrowing towards the top. It is hollow, cylindrical, smooth, silky to shiny, and glutinous—usually with very thick gluten at base. Sometimes, there are short white hairs at the stem base, although their presence is variable. The mushroom has no distinctive odor.
Spores are roughly ellipsoidal in shape with a Q ratio (the fraction of length/width) of 1.6, and dimensions of 9.4–15.4 by 6.2–9.0 μm. They have a small, oblique apiculus, lack oil droplets, and are smooth, thin-walled, and hyaline (translucent). The spores are acyanophilous and strongly amyloid, meaning they stain with Methyl blue and Melzer's reagent, respectively. The basidia (spore-bearing cells) are four-spored (rarely two-spored) and club-shaped with long, robust sterigmata up to 6.0 μm long; they have clamp connections at their bases, and measure 35.3–49.6 by 10.3–14.4 μm. Roridomyces austrororidus has two types of cheilocystidia. One is rare, broadly club-shaped, and tapers to a narrow stem; it measures 24.1–39.5 by 6.8–12.7 μm. The other is moderately dense to abundant, and forms sterile gill edge; it is cylindrical, measures 27.5–70.4 by 5.4–10.4 μm, and often has a swollen tip that splits into two, rarely three branches.
Habitat and distribution
The fruit bodies of Roridomyces austrororidus grow in clusters or groups on rainforest trees, on decayed logs, on fallen Eucalyptus branches, Bedfordia salicina logs and branches, and Nothofagus cunninghamii logs. Specimens have been collected from April to June, and in August.
The fungus is known to occur in Chile, New Zealand, and Australia. In Australia it can be found in Queensland, New South Wales, Victoria, Tasmania and Western Australia. Australian mycologist Tony Young suggests that the distribution of the species indicates that its ancestor may have originated from the ancient continent Gondwana.
- Rexer K-H. (1994) (in German). Die Gattung Mycena s.l., Studien zu Ihrer Anatomie, Morphologie und Systematik (Ph.D. thesis). Tübingen, Germany: Eberhard-Karls-Universität Tübingen.
- "Roridomyces austrororidus (Singer) Rexer 1994". MycoBank. International Mycological Association. http://www.mycobank.org/BioloMICS.aspx?Table=Mycobank&Rec=375302&Fields=All. Retrieved 2012-10-20.
- Horak E. (1978). "Mycena rorida (Fr.) Quél. and related species from the Southern Hemisphere". Berichte der Schweizerischen Botanischen Gesellschaft 88 (1–2): 20–29. doi:10.5169/seals-62336.
- Singer R. (1962). "Basidiomycetes from Masatierra". Arkiv før Botanik. 2 4 (5): 370–400.
- Stevenson G. (1964). "The Agaricales of New Zealand: V". Kew Bulletin 19 (1): 1–59. JSTOR 4108283.
- Young AM. (2004). A Field Guide to the Fungi of Australia. Sydney, Australia: University of New South Wales Press. p. 157. ISBN 978-0-86840-742-5.
- Grgurinovic C. (1995). "Mycena in Australia: section Roridae". Australian Systematic Botany 8: 537–47. doi:10.1071/SB9950537.