biology

Russula xerampelina

Russula xerampelina is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Russula xerampelina rather than just read about it. In short: Russula xerampelina, also commonly known as the shrimp russula, crab brittlegill, or shrimp mushroom, is a basidiomycete mushroom of the brittlegill genus Russula. Two subspecies are recognised.

Key takeaways

Russula xerampelina belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Russula xerampelina to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Russula xerampelina from memory before moving on to harder problems.

Reference excerpt

Russula xerampelina, also commonly known as the shrimp russula, crab brittlegill, or shrimp mushroom, is a basidiomycete mushroom of the brittlegill genus Russula. Two subspecies are recognised. The fruiting bodies appear in coniferous woodlands in autumn in northern Europe and North America. Their caps are coloured various shades of wine-red, purple to green. Mild tasting and edible, it is one of the most highly regarded brittlegills for the table. It is also notable for smelling of shellfish or crab when fresh.

Taxonomy Russula xerampelina was originally described in 1770 as Agaricus xerampelina from a collection in Bavaria by the German mycologist Jacob Christian Schaeffer, who noted the colour as fusco-purpureus or "purple-brown". It was later given its present binomial name by Swedish mycologist Elias Magnus Fries. Its specific epithet is taken from the Ancient Greek meaning "colour of dried vine leaves", xeros meaning "dry", and ampělinos or "of the vine". Two subspecies have been recognised, var. xerampelina and var. tenuicarnosa, with thinner flesh in the cap and the stipe. The name R. erythropoda is now considered a synonym, and former subspecies R. (xerampelina subsp.) amoenipes (originally named by Henri Romagnesi) now a separate species. A former variety with a greenish cap, R. xerampelina var. elaeodes, is now classified as R. clavipes. Recent studies show that Russula xerampelina is actually a species complex, with at least three species: R. xerampelina, R. clavipes, and R. graviolens. Sometimes, more than three are recognized, including R. olympiana. As the first defined species, it gives its name to the section Xerampelinae, a group of related species within the genus Russula, occasionally all termed R. xerampelina in the past. Common names include shrimp mushroom, shrimp Russula, crab brittlegill, and shellfish-scented Russula.

Description

Russula xerampelina has a characteristic odour of boiled crab or shrimp. Trimethylamine and its precursor, trimethylamine N-oxide, are the source of this mushroom's distinct odour. The cap is 5–20 cm (2–8 in) wide, domed, flat, or with a slightly depressed centre, and sticky. The colour is variable, most commonly purple to wine-red, or greenish, and darker towards the centre of the cap. There are fine grooves up to 1 cm long running perpendicular to the margin. The stipe is 4–12 cm (1.5–4.5 in) long, 1.5–4 cm (0.5–1.5 in) wide, cylindrical, white or sometimes with a reddish blush, bruising brown. The gills have a mild to rather bitter taste, narrowly spaced, and turn creamy-yellow on aging specimens. The spore print is creamy-yellow to ochre. The oval spores measure 8.8–9.9 by 6.7–7.8 μm and are covered with 1 μm spines. This Russula has been divided into several similar species by some mycologists. However, they all have the singular dark green colour reaction to iron salts (iron(II) sulfate) when applied to the flesh and smell of shellfish. This aroma is quite distinct and becomes stronger with age.

Similar species More reddish-capped forms could be confused with the sickener (R. emetica), although the latter always has a white stipe and gills; greener-capped species may resemble R. aeruginea. Many other species in the genus are similar, e.g. R. graveolens, but most lack the seafood smell. Russula olivacea has a more velvety cap.

Distribution and ecology Russula xerampelina is widely distributed; quite common in northern temperate zones, and often ranging into the Arctic Circle, it also ranges south to Costa Rica. In North America, it appears from July to October to the east and October to January in the west. Variety tenuicarnosa has been found on sandy soils under pine in Slovakia and northern Italy in Trentino. It grows solitary, or in groups with conifers, and seems to have a preference for Douglas fir, or more rarely pine trees or larch. It is sometimes found in deciduous woods, such as beech and oak. Adults of the pleasing fungus beetle Tritoma angulata have been recorded from this fungus, but it does not seem to be a regular food source for them.

Uses The flavor is mild. This russula is considered one of the best edible species of its genus, although the shellfish smell will persist even when cooking. This is less pleasant in older specimens. The young caps are said to be superb stuffed with any suitable ingredients, and are rarely maggoty.

Illustrations

Worked examples

Example 1 — a first encounter with Russula xerampelina

Start with the simplest possible case. Write down what Russula xerampelina claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Russula xerampelina before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Russula xerampelina ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Russula xerampelina

In research: Russula xerampelina appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Russula xerampelina in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Russula xerampelina is common in secondary-school and first-year university syllabi. It links to neighbouring topics Edible fungi, Fungi described in 1774, Fungi of Europe, so understanding it makes those chapters shorter.
In everyday life: Look for Russula xerampelina outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Russula xerampelina in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Russula xerampelina means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Russula xerampelina out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Russula xerampelina in simple terms?

Russula xerampelina, also commonly known as the shrimp russula, crab brittlegill, or shrimp mushroom, is a basidiomycete mushroom of the brittlegill genus Russula. Two subspecies are recognised.

Why does Russula xerampelina matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Russula xerampelina?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Russula xerampelina.