What You Should Know
Galiella rufa is a distinctive cup fungus that features a light brown spore surface, a dark brown lower surface, and gelatinous flesh. In North America, it is difficult to confuse this species with any others. The fruit bodies have the texture of tough, gelatinous rubber, and have a rough, blackish-brown, felt-like outer surface and a smooth reddish-brown inner surface. Although generally considered inedible by North American mushroom field guides, it is commonly consumed in Malaysia.
Because of its rather dull color, Galiella rufa often tends to blend in with the leaf litter on the forest floor.
Other names: Rubber Cup, Rufous Rubber Cup, Hairy Rubber Cup.
Galiella rufa Mushroom Identification
Saprobic on decaying hardwood sticks and logs; growing alone, gregariously, or (most often) in loose clusters; early summer and summer; widely distributed east of the Rocky Mountains.
Immature Fruiting Body
More or less cylindric; wrinkled; dark brown to black; hairy; interior gray and gelatinous; developing an apical cavity, enclosed and protected by the lid-like outer surface, in which the hymenium develops; with approaching maturity the cavity ruptures, exposing the hymenium and creating the fringed, pustulate margin.
Goblet-shaped to cup-shaped; 2-4 cm across; upper surface concave, orangish to brownish orange, bald; margin incurved, often finely toothed, fringed, or pustulate; undersurface hairy, dark brown to black, running down the pseudostem, becoming somewhat wrinkled with age; pseudostem 1-2 cm long, 3-5 mm thick, terminating in black basal mycelium; flesh gelatinous-rubbery and tough.
Spores 17-21 x 8-10 µ; ellipsoid or occasionally nearly subfusiform; developing thick (1 µ) walls; with guttules in KOH when immature; surface appearing very finely stippled or pitted in both KOH and Melzer's; hyaline. Asci 8-spored; hyaline in KOH and in Melzer's. Paraphyses to about 175 x 2 µ filiform; cylindric; hyaline. Elements on the undersurface of two types: 1) subglobose to pyriform, grayish brown, thin-walled elements 8-10 µ across, tightly packed and sometimes chained together; and 2) thick-walled (1 µ), septate, grayish-brown hairs 4-6 µ wide and often over 250 µ long.
Look-Alikes species include Bulgaria inquinans, Sarcosoma globosum, and Wolfina aurantiopsis . Galiella amurense is similar in appearance to G. rufa. It is found in north temperate Asia, where it grows on the rotting wood of Spruce trees. It has larger ascospores than G. rufa, typically 26–41 by 13–16 µm. Bulgaria inquinans is similar in shape and size but has a shiny black hymenium. Sarcosoma globosum, another species found in eastern North American, is black, has a more liquid interior than G. rufa, and is larger—up to 100 mm (3.9 in) across. Wolfina aurantiopsis has a shallower, woodier fruit body with a yellowish inner surface.
Galiella rufa Taxonomy and Etymology
The species was originally named Bulgaria rufa in 1832 by Lewis David de Schweinitz, based on material collected from Bethlehem, Pennsylvania. In 1913, Pier Andrea Saccardo transferred it to the genus Gloeocalyx as defined by George Edward Massee in 1901 (a genus now synonymous with Plectania) due to its hyaline (translucent) spores. Richard Korf made it the type species of his newly created Galiella in 1957, a genus that encompasses bulgarioid species (those with a morphology similar to those in Bulgaria) with spores that feature surface warts that are made of callose-pectic substances that stain with methyl blue dye.
In 1906, Charles Horton Peck described the variety magna from material collected in North Elba, New York. Peck explained that the variety differed from the typical species in several ways: var. magna grew among fallen leaves under balsam fir trees, or among mosses on the ground, not on buried wood; it lacked a stem, and was instead broad and rounded underneath; its hymenium was more yellow-brown then the nominate variety; and, its spore were slightly longer.
The specific epithet rufa means "rusty" or reddish-brown", and refers to the color of the hymenium. In Sabah, it is known as mata rusa (deer eyes), and in Sarawak, mata kerbau (buffalo eyes).
Galiella rufa Bioactive Compounds
Galiella rufa produces several structurally related hexaketide compounds that have attracted attention for their biological properties: pregaliellalactone, galiellalactone. The compounds have anti-nematodal activity, killing the nematodes Caenorhabditis elegans and Meloidogyne incognita. These compounds have been shown in laboratory tests to inhibit the early steps of the biosynthetic pathways induced by plant hormones known as gibberellic acids, and they also inhibit the germination of seeds of several plants. Galiellalactone is additionally a highly selective and potent inhibitor of interleukin-6 (IL-6) signaling in HepG2 cells. IL-6 is a multifunctional cytokine that is produced by a large variety of cells and functions as a regulator of the immune response, acute phase reactions, and hematopoiesis. Researchers are interested in the potential of small-molecule inhibitors (such as the ones produced by G. rufa) to interfere with the IL-6 signaling cascade that leads to the expression of genes involved in disease.
Galiella rufa Synonyms
Bulgaria rufa Schwein. (1832)
Gloeocalyx rufa (Schwein.) Sacc. (1913)
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