A sticky-capped Russula, usually purple to wine-red but sometimes greenish or brownish, with a stem that bruises yellow then brown and a fishy, shrimp-like odor that strengthens with age. Iron salts turn its flesh dark green. The name belongs to a European conifer species; MushroomExpert treats North American 'shrimp russulas' as an inadequately studied group of species that probably do not match it.
Edible with caution. Wikipedia counts it among the best edible Russulas; the shellfish odor persists in cooking. North American 'shrimp russulas' are a group of species, probably not this European one. Confirm the fishy odor, brown bruising, yellowish spore print and green FeSO4 reaction. The acrid, emetic R. emetica (red cap, pure white gills and stem, no fishy odor) causes GI poisoning. Never eat a Russula that tastes peppery.
Never eat a wild mushroom based on a web page — confirm with an expert.
Habitat
Ectomycorrhizal. In Europe in conifer woods (Wikipedia names Douglas-fir, less often pine or larch, sometimes beech and oak); North American shrimp russulas occur with conifers or hardwoods. Alone or in groups; July to October in eastern North America, October to January in the west.
Distribution
Widespread in north temperate regions; Wikipedia reports it across North America and south to Costa Rica. MushroomExpert states that the name properly belongs to a purplish-red European species associated with conifers and doubts that the same species occurs in North America.
Characteristics
Cap: 5-20 cm, domed becoming flat or slightly depressed; sticky; purple to wine-red or greenish (North American shrimp russulas range from red, pink and purple to brown, olive or yellowish). Gills: attached, close, white becoming cream to yellowish. Stem: 4-12 cm long, 1.5-4 cm thick, white or flushed reddish, bruising brown. Flesh: white, slowly browning; turns dark green with iron salts (FeSO4). Odor: shellfish or crab-like, stronger with age. Taste: mild. Spore print: cream-yellow to ochre. Spores: 8.8-9.9 x 6.7-7.8 um, with spines about 1 um (Wikipedia; MushroomExpert).
