Vomiting Russula

Appearance

The sticky cap of ''R. emetica'' is 2.5–8.5 cm wide, with a shape ranging from convex to flattened, sometimes with a central depression, and sometimes with a shallow umbo. It is a bright scarlet or cherry red, and in maturity, the margins have fine radial grooves extending 2–7 mm towards the center of the cap. The cuticle can be readily peeled from the cap almost to the centre. The brittle flesh is white, measures 4–9 mm thick, and has a very sharp and peppery taste. Gills are closely spaced, white to creamy-white, and have an attachment to the stem ranging from adnate to adnexed or completely free. They are intervenose and occasionally forked near the cap margin. Fruit bodies have a slightly fruity or spicy smell.

The white stem measures 4.5–10.5 cm long by 0.7–2.4 cm thick, and is roughly the same width throughout its length, although it can be a bit thicker near the base. Its surface is dry and smooth, sometimes marked by faint longitudinal grooves. It is either stuffed or partially hollow, and lacks a ring or partial veil.

''Russula emetica'' produces a white to yellowish-white spore print. Spores are roughly elliptical to egg-shaped, with a strongly warted and partially reticulate surface. They have dimensions of 8.8–11.0 by 6.6–8 μm, and are amyloid, meaning that they will stain blue, bluish-grey, to blackish in Melzer's reagent. Basidia are club-shaped, four-spored, hyaline , and measure 32.9–50 by 9.0–11.6 μm. Cystidia located on the gill face are somewhat cylindrical to club-shaped or somewhat spindle-shaped, and measure 35–88 by 7.3–12.4 μm. They are yellowish, and contain granular contents. Cheilocystidia , which are similar in shape to the pleurocystidia, are thin-walled, hyaline, and measure 14–24 by 4.4–7.3 μm. Clamp connections are absent from the hyphae.

The red pigments of this and other russulas are water soluble to some degree, and fruit bodies will often bleach or fade with rain or sunlight; the cap colour of older specimens may fade to pink or orange, or develop white blotches. The main pigment responsible for the red colour of the fruit bodies is called ''russularhodin'', but little is known of its chemical composition.

Habitat

Like all species of ''Russula'', ''R. emetica'' is mycorrhizal, and forms mutually beneficial partnerships with roots of trees and certain herbaceous plants. Preferred host plants are conifers, especially pines. Fruit bodies grow singly, scattered, or in groups in sphagnum moss near bogs, and in coniferous and mixed forests. The fungus occasionally fruits on humus or on very rotten wood. The mushroom is known from North Africa, Asia, Europe, and North America, and can be locally very common. There is some doubt over the extent of its range in North America, as some sightings refer to the related ''R. silvicola''; initially the name "Russula emetica" was often applied to any red-capped white ''Russula''. Sightings in Australia are now referred to the similarly coloured ''R. persanguinea''.

A multi-year field study of the growth of ''R. emetica'' production in a scots pine plantation in Scotland found that total productivity was 0.24–0.49 million mushrooms per hectare per year , corresponding to a fresh weight of 265–460 kg per hectare per year . Productivity was highest from August to October. The longevity of the mushrooms was estimated to be 4–7 days. In a study of the fungal diversity of ectomycorrhizal species in a Sitka spruce forest, ''R. emetica'' was one of the top five dominant fungi. Comparing the frequency of fruit body production between 10-, 20-, 30-, or 40-year-old forest stands, ''R. emetica'' was most prolific in the latter.

Defense

As its name implies, the sickener is inedible, though not as dangerous as sometimes described in older mushroom guides. The symptoms are mainly gastrointestinal in nature: nausea, diarrhoea, vomiting, and colicky abdominal cramps. These symptoms typically begin half an hour to three hours after ingestion of the mushroom, and usually subside spontaneously, or shortly after the ingested material has been expelled from the intestinal tract. The active agent has not been identified but are thought to be sesquiterpenes, which have been isolated from the related genus ''Lactarius'' and from ''Russula sardonia''. Sesquiterpenoids that have been identified from ''R. emetica'' include the previously known compounds lactarorufin A, furandiol, methoxyfuranalcohol, and an unnamed compound unique to this species.

The bitter taste does disappear on cooking and it is said to then be edible, though consumption is not recommended. The mushroom used to be widely eaten in eastern European countries and Russia after parboiling , and then salting or pickling. In some regions of Hungary and Slovakia, the cap cuticle is removed and used as a spice for goulash. Both the red squirrel and the American red squirrel are known to forage for, store and eat ''R. emetica''. Other creatures that have been documented consuming the mushroom include the snail ''Mesodon thyroidus'', several species of slugs , the fruit flies ''Drosophila falleni'' and ''D. quinaria'', and the fungus gnat ''Allodia bipexa''.