Stropharia aeruginosa

Description

Stropharia aeruginosa is a medium-sized blue-green, slimy woodland mushroom, found on lawns, mulch, and woodland from spring to autumn. The edibility of this mushroom is controversial - some sources claim that it is edible, while others claim it to be poisonous, although effects are little known and its toxic constituents undescribed.

In most instances, the caps are much nearer to green than to blue, but when young and fresh they are very beautiful and quite startling.

The caps, initially bell-shaped, flatten and turn paler from the center. White scales adorn the young caps of this remarkable fungus.

A spectacularly beautiful mushroom, Psilocybe aeruginosa is listed in most books as a Stropharia. Noordeloos (1995) proposed a new combination, placing this mushroom, more appropriately, into the genus Psilocybe, following the suggestions of Alexander Smith (1979). This mushroom has historically been reported as poisonous, perhaps because of its psilocybin content. (Some books still report it is poisonous, without providing elaboration or references.) Analyses of specimens from Washington found no psilocybin or psilocin (Beug and Bigwood 1982b). Since the consumability of this species is questioned, caution is advised until the biochemistry of this species is studied further.

Common names: Verdigris Agaric, Verdigris Roundhead, Blue-green Stropharia, Grünspan-träuschling (German), Kopergroenzwam (Dutch).

Mushroom Identification

1. Ecology

   Saprobic, growing alone or gregariously under hardwoods or conifers, and sometimes in the grass; also found on woody debris; summer and fall; not common; probably widely distributed in North America, at least as a species group.

2. Cap

   3–5 cm; convex or broadly bell-shaped at first, becoming broadly convex, with or without a central bump—or nearly flat; very slimy when fresh; bald; when young deep blue-green, but soon fading to yellowish-green and developing yellowish areas and spots; finally becoming brownish yellow overall; the marginal area often decorated with whitish partial veil remnants, especially when young.

3. Gills

   Broadly attached to the stem but receding with maturity; close or, at maturity, nearly distant; short-gills frequent; whitish to pale gray at first, becoming purplish gray to purple-black; edges pale and contrasting.

4. Stem

   3–7 cm long; 5–10 mm thick; equal; dry; with a fragile, soon-disappearing, sheathing ring with a flared and ragged upper edge; often with white scales when young; pale above, colored like the cap below; basal mycelium white; attached to white rhizomorphs.

5. Flesh

   Soft; white or colored like the cap; unchanging when sliced.

6. Odor and Taste

   Odor fragrant and a bit foul (almost reminiscent of the "green corn" odor found in some species of Inocybe); taste not distinctive, or somewhat radishlike.

7. Chemical Reactions

   KOH on cap surface dull yellow.

8. Spore Print

   Purplish brown to purplish black.

9. Microscopic Features

   Spores 6–10 x 3.5–5 µm; ellipsoid to slightly amygdaliform; smooth; pale, dull brown in KOH; yellowish-brown in Melzer's; with a very tiny pore. Cheilocystidia abundant; 25–37.5 x 5–10 µm; capitate to subcapitate; hyaline in KOH; thin-walled. Pleuro-chrysocystidia scattered; often scarcely projecting; 30–50 x 10–15 µm; clavate to fusoid-ventricose or mucronate; hyaline and thin-walled; with yellowish-refractive inclusions. Pileipellis a thick ixocutis of hyaline to golden, smooth, cylindric elements 5–10 µm wide.

Stropharia aeruginosa Similar Species

1. Stropharia caerulea

   Paler blue-green and its cap scales are usually evident only on young fruitbodies; it has brown gills without white edges.

2. Stropharia pseudocyanea

   Smaller; slighter, but strikingly similar grassland species, with a very fleeting ring.

3. Clitocybe odora

   Also blue-green but does not have a slimy cap with scales; it has a strong odor of aniseed.

Medicinal Properties

Antitumor effects

Polysaccharides extracted from the mycelial culture of S. aeruginosa and administered intraperitoneally into white mice at a dosage of 300 mg/kg inhibited the growth of Sarcoma 180 and Ehrlich solid cancers by 70% and 60%, respectively (Ohtsuka et al., 1973).

Neuromodulatory effects

Water and ethanol extracts of S. aeruginosa caused both inhibition and excitation of impulse activity of neurons from the hippocampal stratum pyramidale (CA1 region) (Moldavan et al., 2001).

History

Although this blue mushroom has been known to science for more than two centuries, its separation from Stropharia caerulea as a distinct species.

The basionym of this species was created when the Verdigris Roundhead was described in 1782 by British naturalist William Curtis (1746 - 1799), who gave it the binomial scientific name Agaricus aeruginosus. It was French mycologist Lucien Quélet who, in 1872, established the currently-accepted scientific name of this species as Stropharia aeruginosa.

Synonyms of Stropharia aeruginosa include Agaricus aeruginosus Curtis, and Pratella aeruginosa (Curtis) Gray.

Stropharia, the genus name, comes from the Greek word strophos meaning a belt, and it is a reference to the stem rings of fungi in this generic grouping. The specific epithet aeruginosa means deep blue-green.

Photo sources:

Photo 1 - Author: Jamain (CC BY-SA 3.0, 2.5 Generic, 2.0 Generic and 1.0 Generic)

Photo 2 - Author: Jerzy Opioła (CC BY-SA 3.0)

Photo 3 - Author: Lukas from London, England (CC BY-SA 2.0)

Photo 4 - Author: Anneli Salo (CC BY-SA 3.0)

Photo 5 - Author: Th. Kuhnigk (CC BY-SA 3.0)