Russula xerampelina — Shrimp russula

Shrimp russula, Russula xerampelina

Shrimp russula2, photograph by Benjamin Woo, with permission from University of Washington, Burke Museum.

Shrimp russula, Russula xerampelina

Shrimp russula9, photograph by Benjamin Woo, with permission from University of Washington, Burke Museum.

Russula xerampelina spores

Shrimp russula spores10, sketches and notes by Benjamin Woo, with permission from University of Washington, Burke Museum.

Shrimp russulas are big and rather thick, with wine-red to purple, or (rarely) tan caps. Diagnostic for the species is that the stem turns brown when scratched, in combination with a distinctive fishy to shrimp-like odour.

Odour: Fishy to shrimp-like, especially in mature specimens.
Taste: Mild.
Cap: 5–15 (20) cm in diameter, starting out convex flattening out with age, centre becoming depressed. The colour can vary from dark purple via wine-red to red-brown and tan coloured, often the darkest in the depression. The cap surface is smooth, slightly viscid when wet.
Gills: Attached to the stem; moderately close to crowded; cream-coloured when young, darker to ochre with age; brown where bruised. They are fragile. Most of the gills extend all the way from the stem to the cap margin; shorter spacer gills (lamellulae) are few. Some gills are forked.
Stem: 4–10 cm long x 1–4 cm wide, often widest in the basal part. The base colour is white, often with a pink blush. Where the stem is handled or scratched, the colour changes (slowly) to brown. This is a tell tale character for the species. The stem has a pith-like core and it is fragile rather than fibrous, breaking easily with a snap.
Ring or veil: None.
Cup: None.
Spores: 8.5–10 x 7.0–8.0 µm, with up to 1 µm high spines that are connected by low lines.
Habitat: On the ground in mixed conifer forests.
Geographical distribution: Russula xerampelina in the wide sense is widespread in the temperate and boreal regions of the Northern Hemisphere.

Russula species with an acrid or peppery taste should not be eaten as they may be poisonous, causing symptoms including gastrointestinal distress6. Be aware that in some species, an initially mild taste might change to hot, so take your time tasting a pea-sized piece of the mushroom (and spit out the piece you have tasted).

Russula subnigricans, a toxic species in the blackening russula group has been implicated in eight deaths in Japan7. Although the Asian species is not known from BC or the Pacific northwest, related species may also be poisonous and so eating any of the dingy grey, brown or black-capped species that turn red or black when bruised is not recommended.

Russulas are easy to recognize to genus by their brittle flesh, white- to cream-coloured gills, and often, bright purple, red, or yellow caps. Unlike the related genus Lactarius, they do not ooze milky or coloured juice (latex) where cut or broken. However, russulas are notoriously difficult to identify to species because their characters including their cap colours are strikingly variable8. For the russulas, taste (hot or mild), spore print colour (from white to yellow or ochre), and odour are useful characters helpful in correct identification to species group, if not necessarily to an exact species8.

Russula xerampelina is a species complex of several closely related species that are extremely hard to distinguish from each other. Russula xerampelina was originally described from Europe, and it is possible that the Pacific northwest specimens belong to a different species. Russula viridofusca is distributed across western North America and it is a similar species that shares the shrimp- or fish-like odour. In R. viridofusca, unlike R. xerampelina, the cap margin is often ridged and tuberculate (ridges bear rows of minute bumps) and the cap is more likely to be yellow brown or reddish brown rather than red or purple8.

All specimens with the characteristic wine-red purple cap, cream to yellow gills, cream-coloured stem that slowly turns brown when handled, a mild taste and an odour of fish or shrimp are considered edible for most people.

No toxins are known in shrimp russulas, but illnesses are occasionally reported by individuals with unusual sensitivities6.

Treatment: Contact your regional Poison Control Centre if you or someone you know is ill after eating wild mushrooms. Poison Centres provide free, expert medical advice 24 hours a day, seven days a week. If possible, save the mushrooms or some of the leftover food containing the mushrooms to help confirm identification.

Poison Control:
British Columbia: 604-682-5050 or 1-800-567-8911.
United States (WA, OR, ID): 1-800-222-1222.

MyCoPortal. Mycology Collections Portal, <> accessed February 2018.

Specimen Russula xerampelina WTU-F-038427, GenBank #KX813548.

Trudell, S., Ammirati, J. F. & Mello, M. Mushrooms of the Pacific Northwest. Timber Press, Portland, Oregon (2009).

Siegel, N. & Schwarz, C. Mushrooms of the Redwood Coast. A Comprehensive Guide to the Fungi of Coastal Northern California. Ten Speed Press, Berkeley, California (2016).

Adamčík, S. Taxonomy of the Russula xerampelina group. Part 2. Taxonomic and nomenclatural study of Russula xerampelina and R. erythropoda. Mycotaxon 82, 241-267 (2002).

Beug, M. W., Shaw, M. & Cochran, K. W. Thirty-plus years of mushroom poisoning: Summary of the approximately 2,000 reports in the NAMA case registry. McIlvainea 16, 47-68 (2006).

Gonmori, K., Fujita, H., Yokoyama, K., Watanabe, K. & Suzuki, O. Mushroom toxins: a forensic toxicological review. Forensic Toxicology 29, 85-94, doi:10.1007/s11419-011-0115-4 (2011).

Bazzicalupo, A. L. et al. Troubles with mycorrhizal mushroom identification where morphological differentiation lags behind barcode sequence divergence. Taxon 66, 791-810, doi:10.12705/664.1 (2017).

Specimen Russula xerampelina WTU-F-039181, GenBank #KX813333.

Specimen Russula xerampelina WTU-F-039344, GenBank #KX813285.