Lactarius torminosus

Description

Lactarius torminosus is a large agaric fungus. A common and widely distributed species, it is found in North Africa, northern Asia, Europe, and North America. It has a convex cap becoming depressed in the middle and pale salmon/orange coloring with darker scaled concentric rings.

Although it is valued for its peppery flavor and eaten after suitable preparation in Russia and Finland, the species is highly irritating to the digestive system when eaten raw. The toxins, also responsible for the strongly bitter or acrid taste, are destroyed by cooking. Studies have identified several chemicals present in the mushrooms, including ergosterol and derivatives thereof, and the pungent-tasting velleral.

Common names: Bearded Milkcap, Woolly Milkcap, Parastais vilnītis (Latvia).

Mushroom Identification

1. Cap

   5 to 15 cm in diameter, convex and then flattening and developing a slight central depression, the buff and pink caps are woolly, particularly at their inrolled margins, and they have slightly darker concentric circles most noticeably towards the center; this zoning tends to fade as the fruitbodies age. Beneath the woolly cuticle, the thick cap flesh is white and brittle.

   The distinctive shaggy margin of the cap and its lovely pink coloring makes identification of this milkcap particularly easy - something that cannot be said of the great majority of mushrooms in this genus.

   Seen in black-and-white print, pictures of the Woolly Milkcap are remarkably similar to those of the Brown Rollrim, Paxillus involutus.

2. Gills

   The shortly decurrent, crowded pale pink gills exude a white or pale cream latex when damaged. The very acrid latex does not change color as it dries.

3. Stem

   1 to 2cm in diameter and 4 to 8cm tall, the cylindrical stems are paler than the cap. Stems of young specimens are downy and solid, but as the fruit body matures the stems become smooth and hollow - as seen on the left.

4. Spores

   Subglobose to broadly ellipsoidal, 8-10 x 5.5-7μm, hyaline; ornamented with a well-developed network of ridges and a few isolated warts to 0.7μm tall.

5. Spore Print

   Pale yellowish-cream.

6. Odor and Taste

   A slight odor of turpentine; hot acrid taste.

7. Habitat & Ecological Role

   Mycorrhizal, found under birch trees nearly always in damp places.

Look-Alikes

1. Lactarius pubescens

   Similar but much paler and poisonous.

2. Lactarius scrobiculatus

   Immature fruit bodies resemble L. torminosus, but they have a white latex that soon turns yellow upon exposure to air, and their stems have shiny depressed spots.

3. Lactarius cilicioides

   The caps are not zonate, and their spores are smaller.

4. Lactarius controversus

   Has a cap margin that is not as hairy, whitish to cream-colored gills, and larger spores measuring 7.5–10 by 6–7.5 μm.

5. Lactarius mairei

   Has a coloration similar to L. torminosus, but is rarer and typically found associated with oak trees on calcareous soil.

6. Lactarius subtorminosus

   It can be distinguished by its mild-tasting latex and smaller, roughly spherical spores measuring 5.5–7 by 5.5–6.5 μm.

History

The Woolly Milkcap was described in 1762 by the great German mycologist Jacob Christian Schaeffer, who established the basionym of this species when he gave it the binomial scientific name Agaricus torminosus. It was Christiaan Hendrik Persoon who, in 1797, transferred this milkcap mushroom to the genus Lactarius, thus creating its currently-accepted scientific name Lactarius torminosus.

Lactarius torminosus has several synonyms including Agaricus torminosus Schaeff., Agaricus lactifluus var. torminosus (Schaeff.) Pers., and Lactarius torminosus var. sublateritius Kühner & Romagn.

The generic name Lactarius means producing milk (lactating) - a reference to the milky latex that is exuded from the gills of milkcap fungi when they are cut or torn. The specific epithet torminosus is a Latin adjective that translates to 'cause of colic'.

Lactarius torminosus Chemistry

The compound thought to be responsible for the toxicity of raw L. torminosus is the pungent-tasting velleral present at a concentration of 0.16 mg/g mushroom. Velleral is a breakdown product of stearyl-velutinal. Broken lactifers—specialized hyphal cells that produce the mushroom's latex—leak the precursor chemicals whose breakdown products act as the defensive agents toxic to humans, effectively deterring certain vertebrates that might consume the mushroom. The lactarane-type sesquiterpene lactone 15-hydroxyblennin A is one of several sesquiterpenes produced by the species.

Other lactaranes are found in various Lactarius species, such as blennin A in L. deliciosus and L. blennius, and lactarorufin N in Lactarius rufus. Fungal sesquiterpenes are commonly produced as toxins to defend against predation, and as a result, some have chemical properties that may have applications in medicinal chemistry.

Fruit bodies of Lactarius torminosus contain several sterols, of which ergosterol (a component of fungal cell walls) is the most predominant at 60.5% of all sterols, followed by its derivatives and ergosta-5/7-dien-3-ol (17.0%), ergost-7-en-3-ol (13.7%) and ergosta-7-22-dien-3-ol (8.3%). Researchers have identified 28 volatile compounds that contribute to the odor of the mushroom. Many of these are alcohols and carbonyl compounds with eight carbon atoms; the predominant volatile compound (about 90%) is 1-octen-3-one, an odorant common in mushrooms.

Photo sources:

Photo 1 - Author: Jerzy Opioła (CC BY-SA 3.0)

Photo 2 - Author: Jomo (Public Domain)

Photo 3 - Author: Strobilomyces (CC BY-SA 3.0)

Photo 4 - Author: Th. Kuhnigk (CC BY-SA 3.0)

Photo 5 - Author: RussianSpy (CC BY-SA 3.0)