Lactarius volemus
Encyclopedia
Lactarius volemus is a species of fungus
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

 in the family Russulaceae
Russulaceae
The Russulaceae are a family of fungi in the order Russulales. According to a 2008 estimate, the family contains 1243 species. Its species typically have fruit bodies with friable, chalk-like stalks, that break with a distinct crack, somewhat like a carrot but with porous flesh...

. It is widely distributed in the northern hemisphere
Northern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...

, in temperate regions of Europe, North America and Asia as well as some subtropical and tropical regions of Central America and Asia. A mycorrhiza
Mycorrhiza
A mycorrhiza is a symbiotic association between a fungus and the roots of a vascular plant....

l fungus, its fruit bodies
Basidiocarp
In fungi, a basidiocarp, basidiome or basidioma , is the sporocarp of a basidiomycete, the multicellular structure on which the spore-producing hymenium is borne. Basidiocarps are characteristic of the hymenomycetes; rusts and smuts do not produce such structures...

 grow on the ground at the base of various species of trees from summer to autumn, either individually or in groups. It is valued as an edible mushroom
Edible mushroom
Edible mushrooms are the fleshy and edible fruiting bodies of several species of fungi. Mushrooms belong to the macrofungi, because their fruiting structures are large enough to be seen with the naked eye. They can appear either below ground or above ground where they may be picked by hand...

, and is sold in markets in Asia. Several other Lactarius mushrooms resemble L. volemus, such as the closely related edible species L. corrugis
Lactarius corrugis
Lactarius corrugis, commonly known as the corrugated-cap milky, is a species of fungus in the Russulaceae family. It was first described by American mycologist Charles Horton Peck in 1879....

, but these can be distinguished by differences in distribution, visible morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

, and microscopic characteristics. L. volemus produces a white spore print
Spore print
thumb|300px|right|Making a spore print of the mushroom Volvariella volvacea shown in composite: mushroom cap laid on white and dark paper; cap removed after 24 hours showing pinkish-tan spore print...

 and has roughly spherical spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...

s about 7–8 micrometre
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...

s in diameter.

The colour of the L. volemus mushroom varies from apricot
Apricot (color)
Apricot is a light yellowish-orangeish color that attempts to represent the color of apricots. Actually, it is somewhat paler than actual apricots....

 to tawny
Tawny (color)
Tawny is a yellowish brown color. The word means "tan-colored," from Anglo-Norman tauné "associated with the brownish-yellow of tanned leather," from Old French tané "to tan hides," from Medieval Latin tannare, from tannum "crushed oak bark," used in tanning leather, probably from a Celtic source...

, and the cap
Pileus (mycology)
The pileus is the technical name for the cap, or cap-like part, of a basidiocarp or ascocarp that supports a spore-bearing surface, the hymenium. The hymenium may consist of lamellae, tubes, or teeth, on the underside of the pileus...

 may be up to 11 cm ( in) wide. The pale golden yellow gills on the underside of the cap are closely spaced and sometimes forked. One of the mushroom's most distinctive features is the large amount of latex
Latex
Latex is the stable dispersion of polymer microparticles in an aqueous medium. Latexes may be natural or synthetic.Latex as found in nature is a milky fluid found in 10% of all flowering plants . It is a complex emulsion consisting of proteins, alkaloids, starches, sugars, oils, tannins, resins,...

 ("milk") that it exudes when the gills are damaged, leading to the common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...

s weeping milk cap and voluminous-latex milky. It also has a distinctive fishy smell, which does not affect the taste. The fruit bodies have been chemically analysed and found to contain several sterol
Sterol
Sterols, also known as steroid alcohols, are a subgroup of the steroids and an important class of organic molecules. They occur naturally in plants, animals, and fungi, with the most familiar type of animal sterol being cholesterol...

s related to ergosterol
Ergosterol
Ergosterol is a sterol found in fungi, and named for ergot, a common name for the members of the fungal genus Claviceps from which ergosterol was first isolated. Ergosterol does not occur in plant or animal cells...

, some of which are unique to this species. The mushroom also contains a natural rubber that has been chemically characterized. Phylogenetic analysis suggests that Lactarius volemus represents several species or subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

, rather than a single taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...

.

Taxonomy and naming

The first mention of Lactarius volemus in the scientific literature was in Carl Linnaeus's 1753 Species Plantarum
Species Plantarum
Species Plantarum was first published in 1753, as a two-volume work by Carl Linnaeus. Its prime importance is perhaps that it is the primary starting point of plant nomenclature as it exists today. This means that the first names to be considered validly published in botany are those that appear...

, under the name Agaricus lactifluus. In 1821, Swedish mycologist Elias Magnus Fries
Elias Magnus Fries
-External links:*, Authors of fungal names, Mushroom, the Journal of Wild Mushrooming.*...

 called it Agaricus volemus in his Systema Mycologicum
Systema Mycologicum
Systema Mycologicum is a systematic classification of fungi drawn up in 1821 by the Swedish mycologist and botanist Elias Fries. It took 11 years to complete....

. In this work he proposed a grouping of related species (called a tribus, or tribe) within the genus Agaricus, which he named Galorrheus. Fries later recognised Lactarius as a distinct genus in his 1838 Epicrisis Systematis Mycologici, citing Galorrheus as a synonym
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...

; it was in this publication that the species was first called by the name it is known by today. Although Linnaeus had published the species before Fries, Fries's name is sanctioned
Sanctioned name
In mycology, a sanctioned name is a name that was adopted in certain works of Christiaan Hendrik Persoon or Elias Magnus Fries, which are considered major points in fungal taxonomy.-Definition and effects:...

 and thus has nomenclatural priority. In 1871 Paul Kummer
Paul Kummer
Paul Kummer was a priest, teacher, and scientist in Zerbst, Germany, known chiefly for his contribution to mycological nomenclature. Earlier classification of agarics by pioneering fungal taxonomist Elias Magnus Fries designated only a very small number of genera, with most species falling into...

 raised most of Fries's tribes to generic rank, and so renamed the species Galorrheus volemus. The variety L. volemus var. subrugosus was identified by Charles Horton Peck
Charles Horton Peck
Charles Horton Peck, born March 30, 1833 in Sand Lake, New York, died 1917 in Albany, New York, was an American mycologist of the 19th and early 20th centuries...

 in 1879, but is now classified as a separate species, L. corrugis
Lactarius corrugis
Lactarius corrugis, commonly known as the corrugated-cap milky, is a species of fungus in the Russulaceae family. It was first described by American mycologist Charles Horton Peck in 1879....

. In 1891, Otto Kuntze
Otto Kuntze
Otto Carl Ernst Kuntze was a German botanist.-Biography:Otto Kuntze was born in Leipzig.An apothecary in his early career, he published an essay entitled Pocket Fauna of Leipzig. Between 1863 and...

 moved the species into Lactifluus, a genus which has since been folded back into Lactarius. Another historical synonym is Lactarius lactifluus, used by Lucien Quélet
Lucien Quélet
thumb|Lucien QuéletLucien Quélet was a French mycologist and naturalist who discovered several species and was the founder of the Société mycologique de France, a society devoted to mycological studies....

 in 1886, a renaming based on Linnaeus's Agaricus lactifluus. Lactarius wangii, reported by Hua-An Wen and Jian-Zhe Ying to be a new species from China in 2005, was synonymised two years later with L. volemus.

The specific epithet "volemus" is derived from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 vola, meaning "the hollow of the hand", suggestive of Fries's reference to the large amount of latex "flowing enough to fill the hand". Common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...

s for L. volemus include the weeping milk cap, the tawny milkcap, the orange-brown milky, the voluminous-latex milky, the lactarius orange, the fishy milkcap, and the apricot milk cap. In the West Virginia
West Virginia
West Virginia is a state in the Appalachian and Southeastern regions of the United States, bordered by Virginia to the southeast, Kentucky to the southwest, Ohio to the northwest, Pennsylvania to the northeast and Maryland to the east...

n mountains of the United States, the mushroom is called a "leatherback" or a "bradley". The latter name may originate from its German name Brätling.

Phylogeny

Lactarius volemus is the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

 of the section
Section (botany)
In botany, a section is a taxonomic rank below the genus, but above the species. The subgenus, if present, is higher than the section, and the rank of series, if present, is below the section. Sections are typically used to help organise very large genera, which may have hundreds of species...

 Dulces in subgenus
Subgenus
In biology, a subgenus is a taxonomic rank directly below genus.In zoology, a subgeneric name can be used independently or included in a species name, in parentheses, placed between the generic name and the specific epithet: e.g. the Tiger Cowry of the Indo-Pacific, Cypraea tigris Linnaeus, which...

 Lactifluus. This grouping includes species with a dry cap, abundant latex, and a white or pale cream spore print
Spore print
thumb|300px|right|Making a spore print of the mushroom Volvariella volvacea shown in composite: mushroom cap laid on white and dark paper; cap removed after 24 hours showing pinkish-tan spore print...

. Because the closely related L. corrugis has overlapping morphological
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

 characters, including similar colouration in the cap and stem, it has been difficult to reliably distinguish between the two species. The difficulty in discerning the two is exacerbated by the fact that both species have several colour forms: Japanese specimens of L. volemus may have a red cap, a yellow cap with a long stem, or a velvet-like surface texture; the caps of L. corrugis may be either red, commonly rust
Rust (color)
Rust is a red-brown-orange color resembling iron oxide. It is a commonly used color in stage lighting, and appears roughly the same color as photographic safelights when used over a standard tungsten light source. The color is number 777 in the swatch book....

-coloured. In 2005, Japanese researchers clarified the relationships between these two species and others in section Dulces using molecular phylogenetics, and by comparing differences in fatty acid
Fatty acid
In chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually derived from...

 composition, morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

, and taste. The colour variants group phylogenetically
Phylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...

 into different subclades
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

, suggesting that they might better be considered as "different species, subspecies, or varieties". A 2010 molecular study of L. volemus of northern Thailand found that 79 tested specimens could be divided into 18 distinct phylogenetic species; six of these were described as new species: L. acicularis
Lactarius acicularis
Lactarius acicularis is a member of the large milk-cap genus Lactarius in the order Russulales. Described as new to science in 2010, the species is found in Chiang Mai Province of northern Thailand, where it grows in rainforests that are dominated by Castanopsis armata, Dipterocarpus sp. and...

, L. crocatus
Lactarius crocatus
Lactarius crocatus is a member of the large milk-cap genus Lactarius in the order Russulales. Found in Chiang Mai Province , it was described as new to science in 2010....

, L. distantifolius
Lactarius distantifolius
Lactarius distantifolius is a member of the large milk-cap genus Lactarius in the order Russulales. Found in Chiang Mai Province , it was described as new to science in 2010...

, L. longipilus
Lactarius longipilus
Lactarius longipilus is a member of the large milk-cap genus Lactarius in the order Russulales. Found in Chiang Mai Province , it was described as new to science in 2010. The mushrooms were found at an elevation of growing in a forest dominated by Castanopsis spp., Lithocarpus sp., and Pinus kesiya....

, L. pinguis
Lactarius pinguis
Lactarius pinguis is a member of the large milk-cap genus Lactarius in the order Russulales. Found in northern Thailand, it was described as new to science in 2010....

and L. vitellinus
Lactarius vitellinus
Lactarius vitellinus is a member of the large milk-cap genus Lactarius in the order Russulales. Found in northern Thailand, it was described as new to science in 2010....

.

Description

The fruit body
Basidiocarp
In fungi, a basidiocarp, basidiome or basidioma , is the sporocarp of a basidiomycete, the multicellular structure on which the spore-producing hymenium is borne. Basidiocarps are characteristic of the hymenomycetes; rusts and smuts do not produce such structures...

 of Lactarius volemus has a fleshy and firm cap
Pileus (mycology)
The pileus is the technical name for the cap, or cap-like part, of a basidiocarp or ascocarp that supports a spore-bearing surface, the hymenium. The hymenium may consist of lamellae, tubes, or teeth, on the underside of the pileus...

 with a velvety or smooth surface and a shape that changes with maturity: it starts off convex, with edges curved inwards, then later grows flat with a depression in the middle. With a typical diameter of 5 to 11 cm (2– in), its colour ranges from apricot to tawny
Tawny (color)
Tawny is a yellowish brown color. The word means "tan-colored," from Anglo-Norman tauné "associated with the brownish-yellow of tanned leather," from Old French tané "to tan hides," from Medieval Latin tannare, from tannum "crushed oak bark," used in tanning leather, probably from a Celtic source...

. The cap colouration, however, is somewhat variable, as has been noted in Asian, European, and North American specimens. The stem
Stipe (mycology)
thumb|150px|right|Diagram of a [[basidiomycete]] stipe with an [[annulus |annulus]] and [[volva |volva]]In mycology a stipe refers to the stem or stalk-like feature supporting the cap of a mushroom. Like all tissues of the mushroom other than the hymenium, the stipe is composed of sterile hyphal...

, whose height varies between 4 and 12 cm ( and 5 in), and which is typically between 1 and 1.5 cm (0.393700787401575 and 0.590551181102362 in) thick, has a slightly lighter colouration than the cap. It is firm, with a velvety or smooth surface that sometimes has depressions running longitudinally up and down its length. The gills are adnate
Adnation
Adnation in plants is the "union of unlike parts; organically united or fused with another dissimilar part, e.g. an ovary to a calyx tube, or stamens to petals". This is in contrast to connation, the fusion of similar organs....

 to slightly decurrent
Decurrent
Decurrent is a term used in botany and mycology to describe plant or fungal parts that extend downward.In botany, the term is most often applied to leaf blades that partly wrap or have wings around the stem or petiole and extend down along the stem...

, brittle, narrow, quite closely spaced and sometimes forked. Normally a pale golden yellow colour, the gills turn brown when bruised. Interspersed between the gills are lamellulae, short gills that do not extend to the stem. The flesh
Trama (mycology)
In mycology trama is a term for the inner, fleshy portion of a mushroom's basidiocarp, or fruit body. It is distinct from the outer layer of tissue, known as the pileipellis or cuticle, and from the spore-bearing tissue layer known as the hymenium....

 is whitish and firm. The mushroom smells somewhat fishy; one source suggests the odour is "like a dead shad
Shad
The shads or river herrings comprise the genus Alosa, fish related to herring in the family Clupeidae. They are distinct from others in that family by having a deeper body and spawning in rivers. The several species frequent different areas on both sides of the Atlantic Ocean, Mediterranean Sea....

, which anglers will tell you is probably the most malodorous freshwater fish". The odour is concentrated when the fruit bodies are dried. One of the mushroom's most distinctive features is the abundant latex
Latex
Latex is the stable dispersion of polymer microparticles in an aqueous medium. Latexes may be natural or synthetic.Latex as found in nature is a milky fluid found in 10% of all flowering plants . It is a complex emulsion consisting of proteins, alkaloids, starches, sugars, oils, tannins, resins,...

, so plentiful that a small nick on the gills will cause it to "weep" the milky substance. The latex tends to impart brown stains on whatever it contacts.
The spore print
Spore print
thumb|300px|right|Making a spore print of the mushroom Volvariella volvacea shown in composite: mushroom cap laid on white and dark paper; cap removed after 24 hours showing pinkish-tan spore print...

 is whitish. The spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...

s are roughly spherical, translucent (hyaline
Hyaline
The term hyaline denotes a substance with a glass-like appearance.-Histopathology:In histopathological medical usage, a hyaline substance appears glassy and pink after being stained with haematoxylin and eosin — usually it is an acellular, proteinaceous material...

), and typically measure 7.5–10.0 by 7.5–9.0 µm. The spore surface is reticulate—covered with ridges that form a complete network. The ridges are up to 0.8 µm high and have conspicuous projections up to 1.2 µm high. The spore-bearing cells of the hymenium
Hymenium
The hymenium is the tissue layer on the hymenophore of a fungal fruiting body where the cells develop into basidia or asci, which produce spores. In some species all of the cells of the hymenium develop into basidia or asci, while in others some cells develop into sterile cells called cystidia or...

, the basidia, are club-shaped, hyaline, four-spored, and have dimensions of 40–62 by 7.2–10.4 µm. Interspersed among the basidia are sterile cells called cystidia. The pleurocystidia (cystidia on the side of a gill) are roughly spindle- to club-shaped, and measure 48–145 by 5–13 µm. The cheilocystidia (cystidia on the edge of a gill) may be spindle-, club-, or awl-shaped (subulate), or intermediate in between these forms, and measure 27–60 by 5–7 µm. Additionally, there are cystidia present on both the surface of the cap and the stem. If a drop of ferric sulphate
Iron(II) sulfate
Iron sulfate or ferrous sulfate is the chemical compound with the formula FeSO4. Known since ancient times as copperas and as green vitriol, the blue-green heptahydrate is the most common form of this material...

 (used as a chemical test in mushroom identification) is applied to the mushroom flesh, it will immediately stain dark bluish-green.

The variety Lactarius volemus var. flavus was described by Alexander H. Smith
Alexander H. Smith
Alexander Hanchett Smith was an American mycologist known for his extensive contributions to the taxonomy and phylogeny of the higher fungi, especially the agarics.-Early life:...

 and Lexemuel Ray Hesler
Lexemuel Ray Hesler
-External links:* Finding Aid for the Lexemuel Ray Hesler Collection, 1899-1982...

 in their 1979 monograph
Monograph
A monograph is a work of writing upon a single subject, usually by a single author.It is often a scholarly essay or learned treatise, and may be released in the manner of a book or journal article. It is by definition a single document that forms a complete text in itself...

 of North American Lactarius species. This rare variety, found in the southeastern United States (ranging from South Carolina
South Carolina
South Carolina is a state in the Deep South of the United States that borders Georgia to the south, North Carolina to the north, and the Atlantic Ocean to the east. Originally part of the Province of Carolina, the Province of South Carolina was one of the 13 colonies that declared independence...

 to Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

 and extending west to Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...

), has a cap that stays yellow throughout its development. It also has slightly smaller spores than the regular variety: 6.5–9.0 by 6–8 µm. Some authors have considered the rarely-collected L. volemus var. oedematopus, found in central and southern Europe, to be a distinct variety distinguished from the common variety by a darker reddish-brown cap and a swollen stem. This assessment is not universally accepted, possibly because it falls within the range of morphological variation shown by the main variety. L. volemus var. asiaticus was named in 2004 based on Vietnamese specimens; associating with Khasi pine
Khasi Pine
The Khasi Pine, Pinus kesiya, is one of the most distributed pines in Asia. Its range extends south and east from the Khasi hills in the northeast Indian state of Meghalaya from where it got its name to northern Thailand, Burma, Laos, southernmost China, Vietnam and the Philippines...

 (Pinus khasya), it has small, dull brown, velvety fruit bodies. In general, little taxonomical significance has been ascribed to the several varieties of L. volemus that have been proposed.

Similar species

Lactarius volemus is closely related to L. corrugis, and generally similar in appearance. L. corrugis usually has more surface wrinkles, darker gills, weaker or absent scent, and less orange colouration; however, intermediate colour forms can be found. The two can be distinguished more definitively by microscopic characteristics: L. corrugis has larger spores—typically 10.4–12.8 by 9.6–11.8 µm—with a coarser surface reticulum, and larger pleurocystidia. Lactarius hygrophoroides
Lactarius hygrophoroides
Lactarius hygrophoroides is a member of the large milk-cap genus Lactarius in the order Russulales. It was first described scientifically by Miles Joseph Berkeley and Moses Ashley Curtis in 1859....

also resembles L. volemus, but differs in having widely spaced gills, and spores that lack surface reticulations.

The Zambia
Zambia
Zambia , officially the Republic of Zambia, is a landlocked country in Southern Africa. The neighbouring countries are the Democratic Republic of the Congo to the north, Tanzania to the north-east, Malawi to the east, Mozambique, Zimbabwe, Botswana and Namibia to the south, and Angola to the west....

n species L. chromospermus
Lactarius chromospermus
Lactarius chromospermus is a member of the large milk-cap genus Lactarius in the order Russulales. It was first described scientifically by David N. Pegler in 1982....

has a superficial resemblance to L. volemus, but the former species, in addition to its African distribution, can be identified by its cinnamon-brown spore print—unique in the Russulaceae
Russulaceae
The Russulaceae are a family of fungi in the order Russulales. According to a 2008 estimate, the family contains 1243 species. Its species typically have fruit bodies with friable, chalk-like stalks, that break with a distinct crack, somewhat like a carrot but with porous flesh...

. L. subvelutinus
Lactarius subvelutinus
Lactarius subvelutinus is a member of the large milk-cap genus Lactarius in the order Russulales. It was first described scientifically by American mycologist Peck in 1904....

is also similar to L. volemus, but lacks the fishy odour, has a dull yellow-orange to bright golden orange cap, narrow gills, and a white latex that does not change colour. The species L. austrovolemus
Lactarius austrovolemus
Lactarius austrovolemus is a member of the large milk-cap genus Lactarius in the order Russulales. It was first described scientifically by Japanese mycologist Tsuguo Hongo in 1973....

is closely related, but has more crowded gills, while L. lamprocystidiatus
Lactarius lamprocystidiatus
Lactarius lamprocystidiatus is a member of the large milk-cap genus Lactarius in the order Russulales. Found in Papua New Guinea, it was first described scientifically by Verbeken and Horak in 2000....

can only be reliably distinguished from L. volemus by microscopic characteristics: the reticulations on its spores are taller and more acute, and the meshes formed by the intersections of the reticulations are smaller. Both L. austrovolemus and L. lamprocystidiatus are known only from Papua New Guinea
Papua New Guinea
Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...

.

Edibility and other uses

Despite the unappealing fishy scent that develops after the mushroom is picked, L. volemus is edible
Edible mushroom
Edible mushrooms are the fleshy and edible fruiting bodies of several species of fungi. Mushrooms belong to the macrofungi, because their fruiting structures are large enough to be seen with the naked eye. They can appear either below ground or above ground where they may be picked by hand...

 and recommended for culinary usage, though, typical of Lactarius, it has a slightly granular texture that some may find unappetizing. The odor disappears during cooking. The latex only has a mild taste. The species is considered good for novice mushroom hunters to eat, and is best prepared by slow cooking to prevent it from becoming too hard; specimens that have been rehydrated after having been dried will require longer cooking times to eliminate the grainy texture. The mushroom has also been suggested for use in casserole
Casserole
A casserole, from the French for "saucepan", is a large, deep dish used both in the oven and as a serving vessel. The word casserole is also used for the food cooked and served in such a vessel, with the cookware itself called a casserole dish or casserole pan...

s and thick sauces. Pan frying
Pan frying
Pan frying is a form of frying characterized by the use of minimal cooking oil or fat ; typically using just enough oil to lubricate the pan...

 is not a recommended cooking technique, due to the large amounts of latex it exudes. L. volemus is one of several species of Lactarius that are sold in rural markets in Yunnan Province, China, and it is among the most popular wild edible mushroom species collected for consumption and sale in Nepal. In their 2009 book on Lactarius species of North America, Bessette and colleagues consider the mushroom "the best-known and most popular edible milk mushroom" in the eastern United States. A Turkish study of the nutritional composition of the fruit bodies concluded that L. volemus is a good source of protein and carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...

s.

Bioactive compounds

Fruit bodies contains a unique sterol
Sterol
Sterols, also known as steroid alcohols, are a subgroup of the steroids and an important class of organic molecules. They occur naturally in plants, animals, and fungi, with the most familiar type of animal sterol being cholesterol...

 molecule called volemolide, a derivative
Derivative (chemistry)
In chemistry, a derivative is a compound that is derived from a similar compound by some chemical or physical process. In the past it was also used to mean a compound that can be imagined to arise from another compound, if one atom is replaced with another atom or group of atoms, but modern...

 of the common fungal sterol ergosterol
Ergosterol
Ergosterol is a sterol found in fungi, and named for ergot, a common name for the members of the fungal genus Claviceps from which ergosterol was first isolated. Ergosterol does not occur in plant or animal cells...

 that may have application in fungal chemotaxonomy
Chemotaxonomy
Chemotaxonomy , also called chemosystematics, is the attempt to classify and identify organisms , according to demonstrable differences and similarities in their biochemical compositions. The compounds studied in most of the cases are mostly proteins, amino acids and peptides...

. A 2001 study identified a further nine sterols, three of which were previously unknown to science. According to the authors, these types of highly oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

ated compounds—similar to sterols found in marine soft coral and sponges—are rare in fungi. The mushroom also contains volemitol
Volemitol
Volemitol is a naturally occurring seven-carbon sugar alcohol. It is a substance widely distributed in plants, red algae, fungi, mosses, and lichens. It was also found in lipopolysaccharides from E. coli. In certain higher plants, such as Primula, volemitol plays several important physiological roles...

 (D-glycero-D-mannoheptitol), a seven-carbon sugar alcohol
Sugar alcohol
A sugar alcohol is a hydrogenated form of carbohydrate, whose carbonyl group has been reduced to a primary or secondary hydroxyl group . Sugar alcohols have the general formula Hn+1H, whereas sugars have HnHCO...

 first isolated from the species by the French scientist Émile Bourquelot
Émile Bourquelot
Elime Bourquelot was a French chemist, and professor of pharmacy at the University of Paris. He was born in Jandun , to a farmer, and was the eldest of three sons. Bourqelot became the Chief Pharmacist at the Laënnec Hospital in 1887, where he established a laboratory to conduct his research into...

 in 1889. Volemitol occurs as a free sugar
Monosaccharide
Monosaccharides are the most basic units of biologically important carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste. Examples of monosaccharides include glucose , fructose , galactose, xylose...

 in many plant and brown algal species.

Due to their natural polyisoprene content (1.1–7.7% by dry weight
Dry matter
The dry matter is a measurement of the mass of something when completely dried.The dry matter of plant and animal material would be its solids, i.e. all its constituents excluding water. The dry matter of food would include carbohydrates, fats, proteins, vitamins, minerals, and antioxidants...

 of fruit bodies), L. volemus fruit bodies can also be used to produce rubber
Rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...

. The chemical structure of rubber from the mushroom consists of a high molecular mass
Molecular mass
The molecular mass of a substance is the mass of one molecule of that substance, in unified atomic mass unit u...

 homologue of polyprenol
Polyprenol
Polyprenols are natural long-chain isoprenoid alcohols of the general formula H-n-OH where n is the number of isoprene units. Any prenol with more than 4 isoprene units is a polyprenol. Polyprenols play an important function acting as natural bioregulators and are found in small quantities in...

, arranged as a dimethylallyl group, two trans isoprene
Isoprene
Isoprene , or 2-methyl-1,3-butadiene, is a common organic compound with the formula CH2=CCH=CH2. Under standard conditions it is a colorless liquid...

 units, a long sequence of cis isoprenes (between 260–300 units), terminated by a hydroxyl
Hydroxyl
A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...

 or fatty acid ester. Biosynthetically
Biosynthesis
Biosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step...

, the creation of the polyisoprene begins with the compound trans,trans-farnesyl pyrophosphate
Farnesyl pyrophosphate
Farnesyl pyrophosphate is an intermediate in the HMG-CoA reductase pathway used by organisms in the biosynthesis of terpenes, terpenoids, and sterols...

, and is thought to terminate by ester
Ester
Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...

ification of polyisoprenyl pyrophosphate. The enzyme isopentenyl-diphosphate delta isomerase
Isopentenyl-diphosphate delta isomerase
Isopentenyl-diphosphate delta isomerase is an isomerase which catalyzes the conversion of the relatively un-reactive isopentenyl pyrophosphate to the more-reactive electrophile dimethylallyl pyrophosphate...

 has been identified as required for the initiation of rubber synthesis in L. volemus and several other Lactarius species.

Ecology, distribution, and habitat

Like all Lactarius species, L. volemus forms ectomycorrhizae
Mycorrhiza
A mycorrhiza is a symbiotic association between a fungus and the roots of a vascular plant....

, mutually beneficial symbiotic
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...

 associations with various tree species. In this association, the fungal hyphae grow around the root
Root
In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...

 of the plant and between its cortical
Cortex (botany)
In botany, the cortex is the outer layer of the stem or root of a plant, bounded on the outside by the epidermis and on the inside by the endodermis. It is composed mostly of undifferentiated cells, usually large thin-walled parenchyma cells of the ground tissue system. The outer cortical cells...

 cells, but do not actually penetrate them. The hyphae extend outward into the soil, increasing the surface area for absorption to help the plant absorb nutrients from the soil. It is found growing at the base of both coniferous and broad-leaved
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...

 trees, although it is more common in deciduous woods. It may also sometimes be found in peat moss
Sphagnum
Sphagnum is a genus of between 151 and 350 species of mosses commonly called peat moss, due to its prevalence in peat bogs and mires. A distinction is made between sphagnum moss, the live moss growing on top of a peat bog on one hand, and sphagnum peat moss or sphagnum peat on the other, the...

 beds. The fruit bodies, which appear between summer and autumn, are common. They can be found growing solitarily or in groups, and are more abundant in weather that is warm and humid.

Fruit bodies can be inhabited by species of limoniid
Limoniidae
Limoniidae is a family of flies closely related to the crane flies Tipulidae although they can usually be distinguished by the way the wings are held at rest. Limoniids usually hold/fold the wings along the back of the body whereas tipulids usually hold them out at right angles. Members of the...

 flies, such as Discobola marginata or Limonia yakushimensis
Limonia yakushimensis
Limonia yakushimensis is a crane fly in the family Limoniidae. The species occurs in the Palearctic region. L. yakushimensis is known to rear its young in the fruit bodies of the fungus Lactarius volemus....

, as well as several species of fungi-dwelling mite
Mite
Mites, along with ticks, are small arthropods belonging to the subclass Acari and the class Arachnida. The scientific discipline devoted to the study of ticks and mites is called acarology.-Diversity and systematics:...

s. The flies are hosts for the mites in a symbiotic
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...

 association known as phoresis, whereby the mites are mechanically carried by its host. Mites are small and unable to migrate the relatively long distances between mushrooms without assistance; the insect hosts, in comparison, are large and can transfer the mites between their preferred feeding habitats.

Lactarius volemus is found in warm temperate regions and as well as some subtropical and tropical regions of the Northern Hemisphere
Northern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...

. The fungus is widely distributed throughout Europe, although it is in decline in some countries, and has become rare enough in the Netherlands (and Flanders
Flanders
Flanders is the community of the Flemings but also one of the institutions in Belgium, and a geographical region located in parts of present-day Belgium, France and the Netherlands. "Flanders" can also refer to the northern part of Belgium that contains Brussels, Bruges, Ghent and Antwerp...

) to be considered locally extinct
Local extinction
Local extinction, also known as extirpation, is the condition of a species which ceases to exist in the chosen geographic area of study, though it still exists elsewhere...

. In the Americas, the northern limit of its distribution reaches southern Canada east of the Great Plains
Great Plains
The Great Plains are a broad expanse of flat land, much of it covered in prairie, steppe and grassland, which lies west of the Mississippi River and east of the Rocky Mountains in the United States and Canada. This area covers parts of the U.S...

, and the species extends south to the East Coast of the United States and Mexico, and beyond into Central America (Guatemala). It is also known from Asia, including China (Qinling Mountains
Qinling Mountains
The Qin Mountains are a major east-west mountain range in southern Shaanxi province, China. The mountains provide a natural boundary between the North and South of the country, and support a huge variety of plant and wildlife, some of which is found nowhere else on Earth.To the north is the...

, Guizhou Province, and Yunnan Province), Japan, India, Korea, Nepal, and Vietnam. Collections have also been made from the Middle East, including Iran and Turkey.

External links

  • Photos at Mushroom Observer
    Mushroom Observer
    Mushroom Observer is a collaborative amateur mycology website started by Nathan Wilson in 2006. Its purpose is to "record observations about mushrooms, help people identify mushrooms they aren’t familiar with, and expand the community around the scientific exploration of mushrooms".As of 2010, the...

  • A 360° panorama featuring L. volemus in Marselisborg Forest, Denmark
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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