Russula nigricans

Description

Russula nigricans is a gilled mushroom found in woodland in Europe. The cap is dirty white when young, but swiftly turns brown, and then black on aging. There is usually a large depression in the center of mature caps, which are three-quarter peeling. The stem is white, firm, and straight; it too blackens with age. The gills are off-white initially, very widely spaced, and are adnate. These turn red; then grey, and finally black, when bruised. The flesh, which has a fruity smell, when cut turns pale Indian red, and then grey, and black within 20 minutes.

Old specimens are sometimes parasitized by fungi of the genus Asterophora or Nyctalis, in particular the species N. parasitica and N. asterophora (the pick-a-back toadstool).

It gains both its common and scientific name from its propensity to turn black from cutting or bruising.

Common names: Blackening Russula, Blackening Brittlegill.

Mushroom Identification

1. Cap

   6 to 20 cm (exceptionally 25 cm) in diameter, convex with an inrolled margin and then later flatter and centrally depressed, the caps are dirty white at first, turning gray-brown and then eventually blackening all over.

2. Gills

   The widely-spaced adnate gills of Russula nigricans are thick and extremely brittle; they are interspersed with many shorter gills (known as lamellae). Ivory-white to straw-colored at first, the gills soon turn grey and bruise rosy red-brown when damaged. Eventually, like the rest of the fruiting body, the gills turn dull black.

3. Stem

   1 to 4 cm in diameter and 3 to 8 cm tall, the smooth, blackening stems are cylindrical or taper in slightly towards the base. The stem flesh is white at first, blackening with age; reddening, and then blackening when bruised. There is no stem ring.

4. Spores

   Ellipsoidal or ovoid; 7-8 x 6-7µm; warts to typically 0.3µm tall, finely linked in a partial reticulum (mesh-like network).

5. Spore Print

   White.

6. Odor and Taste

   Slight fruity odor; mild taste becoming hotter after a few moments.

7. Habitat & Ecological Role

   Ectomycorrhizal; occurs in both coniferous and broadleaf woodland.

Look-Alikes

1. Russula densifolia

   Found mainly under beech trees; it has crowded gills and turns black without an intermediate brown stage.

2. Russula albonigra

   Has closer gills and is far less common. It bruises directly to black, lacking the red intermediary phase.

Medicinal Properties

1. Antitumor activity

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

2. Molluscicidal activity

   A dichloromethane extract of Russula nigricans was shown to be molluscicidal towards Biomphalaria glabrata (Keller et al., 2002).

History

The Blackening Brittlegill was first described in 1785 by French mycologist Jean Baptiste Francois Pierre Bulliard, who gave it the scientific name Agaricus nigricans. In 1838 this species was moved to the genus Russula by the famous Swedish mycologist Elias Magnus Fries.

Russula, the generic name, means red or reddish, and indeed many of the brittlegills have red caps. The specific epithet nigricans means 'becoming black'.

Russula nigricans Synonyms

1. Agaricus nigricans Bull.

2. Agaricus elephantinus Bolton

3. Omphalia adusta ß elephantinus (Bolton) Gray

4. Russula elephantina (Bolton) Fr.

5. Russula nigrescens Krombh.

Photo sources:

Photo 1 - Author: Strobilomyces (CC BY-SA 3.0)

Photo 2 - Author: Strobilomyces (CC BY-SA 3.0)

Photo 3 - Author: Holger Krisp (CC BY 3.0)