Galerina marginata
Encyclopedia
Galerina marginata is a species
of poisonous fungus
in the family Hymenogastraceae
of the order Agaricales
. Prior to 2001, the species G. autumnalis, G. oregonensis, G. unicolor, and G. venenata were thought to be separate due to differences in habitat and the viscidity of their caps
, but phylogenetic analysis showed that they are all the same species.
The fruit bodies
of this fungus have brown to yellow-brown caps that fade in color when drying. The gills are brownish and give a rusty spore print
. A well-defined membranous ring
is typically seen on the stems
of young specimens but often disappears with age. In older fruit bodies, the caps are flatter and the gills and stems browner. The species is a classic "little brown mushroom"—a catchall category that includes all small to medium-sized, hard-to-identify brownish mushrooms, and may be easily confused with several edible
species.
Galerina marginata is widespread in the Northern Hemisphere
, including Europe, North America, and Asia, and has also been found in Australia. It is a wood-rotting fungus that grows predominantly on decaying conifer wood. An extremely poisonous species, it contains the same deadly amatoxin
s found in the death cap (Amanita phalloides). Ingestion in toxic amounts causes severe liver damage with vomiting, diarrhea, hypothermia
, and eventual death if not treated rapidly. About ten poisonings have been attributed to the species now grouped as G. marginata over the last century.
variable taxon
named Galerina marginata was once split into five distinct species. Norwegian mycologist Gro Gulden
and colleagues concluded that all five represented the same species after comparing the DNA sequences of the internal transcribed spacer
region of ribosomal DNA
for various North American and European specimens in Galerina
section Naucoriopsis. The results showed no genetic differences between G. marginata and G. autumnalis, G. oregonensis, G. unicolor, and G. venenata, thus reducing all these names to synonymy
. The oldest of these names are Agaricus marginatus, described by August Batsch
in 1789, and Agaricus unicolor, described by Martin Vahl
in 1792. Agaricus autumnalis was described by Charles Horton Peck
in 1873, and later moved to Galerina by A. H. Smith and Rolf Singer
in their 1962 worldwide monograph
on that genus. In the same publication they also introduced the G. autumnalis varieties robusta and angusticystis. Another of the synonymous species, G. oregonensis, was first described in that monograph. Galerina venenata was first identified as a species by Smith in 1953. Since Agaricus marginatus is the oldest validly published name, it has priority according to the rules of botanical nomenclature.
Another species analysed in Gulden's 2001 study, Galerina pseudomycenopsis, also could not be distinguished from G. marginata based on ribosomal DNA sequences and restriction fragment length polymorphism
analyses. Because of differences in ecology, fruit body color and spore size combined with inadequate sampling, the authors preferred to maintain G. pseudomycenopsis as a distinct species. A 2005 study again failed to separate the two species using molecular methods, but reported that the incompatibility demonstrated in mating
experiments suggests that the species are distinct.
In the fourth edition (1986) of Singer's comprehensive classification of the Agaricales
, G. marginata is the type species
of Galerina section Naucoriopsis, a subdivision first defined by French mycologist Robert Kühner
in 1935. It includes small brown-spored mushrooms characterized by cap edges initially curved inwards, fruit bodies resembling Pholiota
or Naucoria
and thin-walled, obtuse or acute-ended pleurocystidia that are not rounded at the top. Within this section, G. autumnalis and G. oregonensis are in stirps Autumnalis, while G. unicolor, G. marginata, and G. venenata are in stirps Marginata. Autumnalis species are characterized by having a viscid to lubricous cap surface while Marginata species lack a gelatinous cap—the surface is moist, "fatty-shining", or matte when wet. However, as Gulden explains, this characteristic is highly variable: "Viscidity is a notoriously difficult character to assess because it varies with the age of the fruitbody and the weather conditions during its development. Varying degrees of viscidity tend to be described differently and applied inconsistently by different persons applying terms such as lubricous, fatty, fatty-shiny, sticky, viscid, glutinous, or (somewhat) slimy."
The specific epithet marginata is derived from the Latin
word for "margin" or "edge", while autumnalis means "of the autumn". Common name
s of the species include the "marginate Pholiota" (resulting from its synonymy with Pholiota marginata), "funeral bell", "deadly skullcap", and "deadly Galerina". G. autumnalis was known as the "fall Galerina" or the "autumnal Galerina", while G. venenata was the "deadly lawn Galerina".
reaches 1.7 to 4 cm (0.669291338582677 to 1.6 in) in diameter. It starts convex, sometimes broadly conical, and has edges (margins) that are curved in against the gills. As the cap grows and expands, it becomes broadly convex and then flattened, sometimes developing a central elevation, or umbo
, which may project prominently from the cap surface.
Based on the collective descriptions of the five taxa now considered to be G. marginata, the texture of the surface shows significant variation. Smith and Singer give the following descriptions of surface texture: from "viscid" (G. autumnalis), to "shining and viscid to lubricous when moist" (G. oregonensis), to "shining, lubricous to subviscid (particles of dirt adhere to surface) or merely moist, with a fatty appearance although not distinctly viscid", to "moist but not viscid" (G. marginata). The cap surface remains smooth and changes colors with humidity (hygrophanous
), pale to dark ochraceous
tawny
over the disc and yellow-ochraceous on the margin (at least when young), but fading to dull tan or darker when dry. When moist, the cap is somewhat transparent so that the outlines of the gills may be seen as striations. The flesh
is pale brownish ochraceous to nearly white, thin and pliant, with an odor and taste varying from very slightly to strongly like flour (farinaceous).
The gills are typically narrow and crowded together, with a broadly adnate
to nearly decurrent
attachment to the stem and convex edges. They are a pallid brown when young, becoming tawny at maturity. Some short gills, called lamellulae, do not extend entirely from the cap edge to the stem, and are intercalated among the longer gills. The stem
ranges from 3 to 6 cm (1.2 to 2.4 in) long, 3 to 9 mm (0.118110236220472 to 0.354330708661417 in) thick at the apex, and stays equal in width throughout or is slightly enlarged downward. Initially solid, it becomes hollow from the bottom up as it matures. The membranous ring
is located on the upper half of the stem near the cap, but may be sloughed off and missing in older specimens. Its color is initially whitish or light brown, but usually appears a darker rusty-brown in mature specimens that have dropped spores on it. Above the level of the ring, the stem surface has a very fine whitish powder and is paler than the cap; below the ring it is brown down to the reddish-brown to bistre
base. The lower portion of the stem has a thin coating of pallid fibrils which eventually disappear and do not leave any scales. The spore print
is rusty-brown.
, and are slightly inequilateral in profile view, and egg-shaped in face view. Like all Galerina species, the spores have a plage
, which has been described as resembling "a slightly wrinkled plastic shrink-wrap covering over the distal end of the spore". The spore surface is warty and full of wrinkles, with a smooth depression where the spore was once attached via the sterigmatum to the basidium
(the spore-bearing cell). When in potassium hydroxide
(KOH) solution, the spores appear tawny or darker rusty-brown, with an apical callus. The basidia are four-spored (rarely with a very few two-spored ones), roughly cylindrical when producing spores, but with a slightly tapered base, and measure 21–29 by 5–8.4 µm.
Cystidia are cells of the fertile hymenium
that do not produce spores. These sterile cells, which are structurally distinct from the basidia, are further classified according to their position. In G. marginata, the pleurocystidia (cystidia from the gill sides) are 46–60 by 9–12 µm, thin-walled, and hyaline
in KOH, fusoid to ventricose
in shape with wavy necks and blunt to subacute apices (3–6 µm diameter near apex). The cheilocystidia (cystidia on the gill edges) are similar in shape but often smaller than the pleurocystidia, abundant, with no club-shaped or abruptly tapering (mucronate) cells present. Clamp connection
s are present in the hyphae.
species. Pholiota mutabilis produces fruit bodies roughly similar in appearance and also grows on wood, but may be distinguished from G. marginata by its stems bearing scales up to the level of the ring, and from growing in large clusters (which is not usual of G. marginata). However, the possibility of confusion is such that this good edible species is "not recommended to those lacking considerable experience in the identification of higher fungi." Furthermore, microscopic examination shows smooth spores in Pholiota. G. marginata may be easily confused with other edibles such as Armillaria mellea
and Kuehneromyces mutabilis
. Regarding the latter species, one source notes "Often, G. marginata bears an astonishing resemblance to this fungus, and it requires careful and acute powers of observation to distinguish the poisonous one from the edible one." K. mutabilis may be distinguished by the presence of scales on the stem below the ring, the larger cap, which may reach a diameter of 6 cm (2.4 in), and spicy or aromatic odor of the flesh. The related K. vernalis is a rare species and even more similar in appearance to G. marginata. Examination of microscopic characteristics is typically required to reliably distinguish between the two, revealing smooth spores with a germ pore
.
Another potential edible lookalike is the "velvet foot", Flammulina velutipes. This species has gills that are white to pale yellow, a white spore print, and spores that are elliptical, smooth, and measure 6.5–9 by 2.5–4 µm. A rough resemblance has also been noted with the edible Hypholoma capnoides
, as well as Conocybe filaris
, another poisonous amatoxin-containing species.
fungus, obtaining nutrients by breaking down organic matter. It is known to have most of the major classes of secreted enzyme
s that dissolve plant cell wall
polysaccharide
s, and has been used as a model saprobe in recent studies of ectomycorrhizal
fungi. Because of its variety of enzymes capable of breaking down wood and other lignocellulosic materials, the Department of Energy Joint Genome Institute (JGI) is currently sequencing its genome. The fungus is typically reported to grow on or near the wood of conifers, although it has been observed to grow on hardwoods as well. Fruit bodies may grow solitarily, but more typically in groups or small clusters, and appear in the summer to autumn. Sometimes, they may grow on buried wood and thus appear to be growing on soil.
Galerina marginata is widely distributed throughout the Northern Hemisphere, found in North America, Europe, Japan, Iran, continental Asia, and the Caucasus
. In North America, it has been collected as far north as the boreal forest of Canada
and subarctic
and arctic
habitats in Labrador
, and south to Jalisco, Mexico. It is also found in Australia.
s. Amatoxins belong to a family of bicyclic octapeptide derivatives composed of an amino acid
ring bridged by a sulphur atom and characterized by differences in their side groups
; these compounds are responsible for more than 90% of fatal mushroom poisoning
s in humans. The amatoxins inhibit the enzyme
RNA polymerase II
, which copies the genetic code
of DNA into messenger RNA
molecules. The toxin naturally accumulates in liver cells
, and the ensuing disruption of metabolism accounts for the severe liver dysfunction cause by amatoxins. Amatoxins also lead to kidney failure because, as the kidneys attempt to filter out poison, it damages the convoluted tubules and reenters the blood to recirculate and cause more damage. Initial symptoms after ingestion include severe abdominal pain
, vomiting
, and diarrhea
which may last for six to nine hours. Beyond these symptoms, toxins severely affect the liver which results in gastrointestinal bleeding
, a coma
, kidney failure, or even death, usually within seven days of consumption.
Galerina marginata was shown in various studies to contain the amatoxins α-amanitin
and γ-amanitin
, first as G. venenata, then as G. marginata and G. autumnalis. The ability of the fungus to produce these toxins was confirmed by growing the mycelium
as a liquid culture
(only trace amounts of ß-amanitin
were found). G. marginata is thought to be the only species of the amatoxin-producing genera that will produce the toxins while growing in culture. Both amanitins were quantified in G. autumnalis (1.5 mg/g dry weight
) and G. marginata (1.1 mg/g dry weight). Later experiments confirmed the occurrence of γ-amanitin and ß-amanitin in German specimens of G. autumnalis and G. marginata and revealed the presence of the three amanitins in the fruit bodies of G. unicolor. Although some mushroom field guide
s claim that the species (as G. autumnalis) also contains phallotoxin
s, scientific evidence does not support this contention. A 2004 study determined that the amatoxin content of G. marginata varied from 78.17 to 243.61 µg/g of fresh weight. In this study, the amanitin amounts from certain Galerina specimens were higher than those from some Amanita phalloides, a European fungus generally considered as the richest in amanitins. The authors suggest that "other parameters such as extrinsic factors (environmental conditions) and intrinsic factors (genetic properties) could contribute to the significant variance in amatoxin contents from different specimens." The lethal dose of amatoxins has been estimated to be about 0.1 mg/kg human body weight, or even lower. Based on this value, the ingestion of 10 G. marginata fruit bodies containing about 250 µg of amanitins per gram of fresh tissue could poison a child weighing approximately 20 kilograms (44.1 lb). However, a 20-year retrospective study of more than 2100 cases of amatoxin poisonings from North American and Europe showed that few cases were due to ingestion of Galerina species. This low frequency may be attributed to the mushroom's nondescript appearance as a "little brown mushroom" leading to it being overlooked by collectors, and by the fact that 21% of amatoxin poisonings were caused by unidentified species.
The toxicity of certain Galerina species has been known for a century. In 1912, Charles Horton Peck
reported a human poisoning case due to G. autumnalis. In 1954, a poisoning was caused by G. venenata. Between 1978 and 1995, ten cases caused by amatoxin-containing Galerinas were reported in the literature. Three European cases, two from Finland and one from France were attributed to G. marginata and G. unicolor, respectively. Seven North American exposures included two fatalities from Washington due to G. venenata, with five cases reacting positively to treatment; four poisonings were caused by G. autumnalis from Michigan and Kansas, in addition to poisoning caused by an unidentified Galerina species from Ohio. Several poisonings have been attributed to collectors consuming the mushrooms after mistaking them for hallucinogenic Psilocybe
species, such as P. stuntzii
.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of poisonous 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 Hymenogastraceae
Hymenogastraceae
The Hymenogastraceae is a family of fungi in the Agaricales.The blue-staining members of the genus Psilocybe form a clade that is sister to Galerina in the Hymenogastraceae; however, they have not yet been formally transferred....
of the order Agaricales
Agaricales
The fungal order Agaricales, also known as gilled mushrooms , or euagarics, contains some of the most familiar types of mushrooms. The order has 33 extant families, 413 genera, and over 13000 described species, along with five extinct genera known only from the fossil record...
. Prior to 2001, the species G. autumnalis, G. oregonensis, G. unicolor, and G. venenata were thought to be separate due to differences in habitat and the viscidity of their caps
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...
, but phylogenetic analysis showed that they are all the same species.
The 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...
of this fungus have brown to yellow-brown caps that fade in color when drying. The gills are brownish and give a rusty 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...
. A well-defined membranous ring
Annulus (mycology)
An annulus is the ring like structure sometimes found on the stipe of some species of mushrooms. The annulus represents the remaining part of the partial veil, after it has ruptured to expose the gills or other spore-producing surface. An annulus may be thick and membranous, or it may be cobweb-like...
is typically seen on the stems
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...
of young specimens but often disappears with age. In older fruit bodies, the caps are flatter and the gills and stems browner. The species is a classic "little brown mushroom"—a catchall category that includes all small to medium-sized, hard-to-identify brownish mushrooms, and may be easily confused with several 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...
species.
Galerina marginata is widespread 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...
, including Europe, North America, and Asia, and has also been found in Australia. It is a wood-rotting fungus that grows predominantly on decaying conifer wood. An extremely poisonous species, it contains the same deadly amatoxin
Amatoxin
Amatoxins are a subgroup of at least eight toxic compounds found in several genera of poisonous mushrooms, most notably Amanita phalloides and several other members of the genus Amanita, as well as some Conocybe, Galerina and Lepiota mushroom species.-Structure:The compounds have a similar...
s found in the death cap (Amanita phalloides). Ingestion in toxic amounts causes severe liver damage with vomiting, diarrhea, hypothermia
Hypothermia
Hypothermia is a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as . Body temperature is usually maintained near a constant level of through biologic homeostasis or thermoregulation...
, and eventual death if not treated rapidly. About ten poisonings have been attributed to the species now grouped as G. marginata over the last century.
Taxonomy and naming
What is now recognized as a single morphologicallyMorphology (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....
variable 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...
named Galerina marginata was once split into five distinct species. Norwegian mycologist Gro Gulden
Gro Gulden
Gro Sissel Gulden is a Norwegian mycologist.She was hired as a curator at the Natural History Museum at the University of Oslo in 1967, and was promoted to professor in 2001. She retired in the autumn of 2006. A replacement curator has not been found as of early 2009. Gulden has published several...
and colleagues concluded that all five represented the same species after comparing the DNA sequences of the internal transcribed spacer
Internal transcribed spacer
ITS refers to a piece of non-functional RNA situated between structural ribosomal RNAs on a common precursor transcript. Read from 5' to 3', this polycistronic rRNA precursor transcript contains the 5' external transcribed sequence , 18S rRNA, ITS1, 5.8S rRNA, ITS2, 28S rRNA and finally the 3'ETS...
region of ribosomal DNA
Ribosomal DNA
Ribosomal DNA codes for ribosomal RNA. The ribosome is an intracellular macromolecule that produces proteins or polypeptide chains. The ribosome itself consists of a composite of proteins and RNA. As shown in the figure, rDNA consists of a tandem repeat of a unit segment, an operon, composed of...
for various North American and European specimens in Galerina
Galerina
Galerina is a genus of small brown-spored saprobic mushrooms, with over 300 species found throughout the world, from the far north to remote Macquarie Island in the Southern Ocean. Species are typically small and hygrophanous, with a slender and brittle stem. They are often found growing on wood,...
section Naucoriopsis. The results showed no genetic differences between G. marginata and G. autumnalis, G. oregonensis, G. unicolor, and G. venenata, thus reducing all these names to synonymy
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...
. The oldest of these names are Agaricus marginatus, described by August Batsch
August Batsch
Dr August Johann Georg Karl Batsch was a German naturalist. He was a recognised authority on mushrooms, and also described new species of ferns, bryophytes, and seed plants.- Life and career :...
in 1789, and Agaricus unicolor, described by Martin Vahl
Martin Vahl
Martin Henrichsen Vahl was a Danish-Norwegian botanist and zoologist.He studied botany in Copenhagen and in Uppsala under Carolus Linnaeus. He edited Flora Danica fasc. XVI-XXI , Symbolæ Botanicæ I-III , Eclogæ Americanæ I-IV and Enumeratio Plantarum I-II...
in 1792. Agaricus autumnalis was described 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 1873, and later moved to Galerina by A. H. Smith and Rolf Singer
Rolf Singer
Rolf Singer was a German-born mycologist and one of the most important taxonomists of gilled mushrooms in the 20th century....
in their 1962 worldwide 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...
on that genus. In the same publication they also introduced the G. autumnalis varieties robusta and angusticystis. Another of the synonymous species, G. oregonensis, was first described in that monograph. Galerina venenata was first identified as a species by Smith in 1953. Since Agaricus marginatus is the oldest validly published name, it has priority according to the rules of botanical nomenclature.
Another species analysed in Gulden's 2001 study, Galerina pseudomycenopsis, also could not be distinguished from G. marginata based on ribosomal DNA sequences and restriction fragment length polymorphism
Restriction fragment length polymorphism
In molecular biology, restriction fragment length polymorphism, or RFLP , is a technique that exploits variations in homologous DNA sequences. It refers to a difference between samples of homologous DNA molecules that come from differing locations of restriction enzyme sites, and to a related...
analyses. Because of differences in ecology, fruit body color and spore size combined with inadequate sampling, the authors preferred to maintain G. pseudomycenopsis as a distinct species. A 2005 study again failed to separate the two species using molecular methods, but reported that the incompatibility demonstrated in mating
Mating in fungi
Mating in fungi is a complex process governed by mating types. Research on fungal mating has focused on only a few model species. Since not all of the fungi reproduce sexually and many that do are isogamous, the terms male and female do not apply to this kingdom...
experiments suggests that the species are distinct.
In the fourth edition (1986) of Singer's comprehensive classification of the Agaricales
Agaricales
The fungal order Agaricales, also known as gilled mushrooms , or euagarics, contains some of the most familiar types of mushrooms. The order has 33 extant families, 413 genera, and over 13000 described species, along with five extinct genera known only from the fossil record...
, G. marginata 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 Galerina section Naucoriopsis, a subdivision first defined by French mycologist Robert Kühner
Robert Kühner
Robert Kühner, born Paris 15 March 1903, died Lyon 27 February 1996, was a French mycologist most notable for reviewing many agaric genera.-References:...
in 1935. It includes small brown-spored mushrooms characterized by cap edges initially curved inwards, fruit bodies resembling Pholiota
Pholiota
Pholiota is a genus of small to fleshy mushrooms in the family Strophariaceae. The genus has a widespread distribution, especially in temperate regions, and contains about 150 species....
or Naucoria
Naucoria
Naucoria is a genus of fungi in the Hymenogastraceae family of the Agaricales order. The genus has a widespread distribution, and contains 30 species that usually form mycorrhizal relationships with species of Alder. The genus name is synonymous with Alnicola....
and thin-walled, obtuse or acute-ended pleurocystidia that are not rounded at the top. Within this section, G. autumnalis and G. oregonensis are in stirps Autumnalis, while G. unicolor, G. marginata, and G. venenata are in stirps Marginata. Autumnalis species are characterized by having a viscid to lubricous cap surface while Marginata species lack a gelatinous cap—the surface is moist, "fatty-shining", or matte when wet. However, as Gulden explains, this characteristic is highly variable: "Viscidity is a notoriously difficult character to assess because it varies with the age of the fruitbody and the weather conditions during its development. Varying degrees of viscidity tend to be described differently and applied inconsistently by different persons applying terms such as lubricous, fatty, fatty-shiny, sticky, viscid, glutinous, or (somewhat) slimy."
The specific epithet marginata 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...
word for "margin" or "edge", while autumnalis means "of the autumn". 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 of the species include the "marginate Pholiota" (resulting from its synonymy with Pholiota marginata), "funeral bell", "deadly skullcap", and "deadly Galerina". G. autumnalis was known as the "fall Galerina" or the "autumnal Galerina", while G. venenata was the "deadly lawn Galerina".
Description
The capPileus (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...
reaches 1.7 to 4 cm (0.669291338582677 to 1.6 in) in diameter. It starts convex, sometimes broadly conical, and has edges (margins) that are curved in against the gills. As the cap grows and expands, it becomes broadly convex and then flattened, sometimes developing a central elevation, or umbo
Umbo (mycology)
thumb|right|[[Cantharellula umbonata]] has an umbo.thumb|right|The cap of [[Psilocybe makarorae]] is acutely papillate.An umbo is a raised area in the center of a mushroom cap. Caps that possess this feature are called umbonate. Umbos that are sharply pointed are called acute, while those that are...
, which may project prominently from the cap surface.
Based on the collective descriptions of the five taxa now considered to be G. marginata, the texture of the surface shows significant variation. Smith and Singer give the following descriptions of surface texture: from "viscid" (G. autumnalis), to "shining and viscid to lubricous when moist" (G. oregonensis), to "shining, lubricous to subviscid (particles of dirt adhere to surface) or merely moist, with a fatty appearance although not distinctly viscid", to "moist but not viscid" (G. marginata). The cap surface remains smooth and changes colors with humidity (hygrophanous
Hygrophanous
The adjective hygrophanous refers to the color change of mushroom tissue as it loses or absorbs water, which causes the pileipellis to become more transparent when wet and opaque when dry....
), pale to dark ochraceous
Ochre
Ochre is the term for both a golden-yellow or light yellow brown color and for a form of earth pigment which produces the color. The pigment can also be used to create a reddish tint known as "red ochre". The more rarely used terms "purple ochre" and "brown ochre" also exist for variant hues...
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...
over the disc and yellow-ochraceous on the margin (at least when young), but fading to dull tan or darker when dry. When moist, the cap is somewhat transparent so that the outlines of the gills may be seen as striations. 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 pale brownish ochraceous to nearly white, thin and pliant, with an odor and taste varying from very slightly to strongly like flour (farinaceous).
The gills are typically narrow and crowded together, with a broadly 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 nearly 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...
attachment to the stem and convex edges. They are a pallid brown when young, becoming tawny at maturity. Some short gills, called lamellulae, do not extend entirely from the cap edge to the stem, and are intercalated among the longer gills. 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...
ranges from 3 to 6 cm (1.2 to 2.4 in) long, 3 to 9 mm (0.118110236220472 to 0.354330708661417 in) thick at the apex, and stays equal in width throughout or is slightly enlarged downward. Initially solid, it becomes hollow from the bottom up as it matures. The membranous ring
Annulus (mycology)
An annulus is the ring like structure sometimes found on the stipe of some species of mushrooms. The annulus represents the remaining part of the partial veil, after it has ruptured to expose the gills or other spore-producing surface. An annulus may be thick and membranous, or it may be cobweb-like...
is located on the upper half of the stem near the cap, but may be sloughed off and missing in older specimens. Its color is initially whitish or light brown, but usually appears a darker rusty-brown in mature specimens that have dropped spores on it. Above the level of the ring, the stem surface has a very fine whitish powder and is paler than the cap; below the ring it is brown down to the reddish-brown to bistre
Bistre
Bistre is either: 1) A shade of gray, 2) A shade of brown made from soot, and 3) The name for a color resembling the pigment. Bistre's appearance is generally of a dark grayish brown, with a yellowish cast....
base. The lower portion of the stem has a thin coating of pallid fibrils which eventually disappear and do not leave any scales. 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 rusty-brown.
Microscopic characteristics
The spores measure 8–10 by 5–6 µmMicrometre
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...
, and are slightly inequilateral in profile view, and egg-shaped in face view. Like all Galerina species, the spores have a plage
Plage (mycology)
A plage is a clear, unornamented area on the basal area of an otherwise ornamented spore. Characteristic of spores from the euagaric genus Galerina.-Images:* - line drawing* - photo...
, which has been described as resembling "a slightly wrinkled plastic shrink-wrap covering over the distal end of the spore". The spore surface is warty and full of wrinkles, with a smooth depression where the spore was once attached via the sterigmatum to the basidium
Basidium
thumb|right|500px|Schematic showing a basidiomycete mushroom, gill structure, and spore-bearing basidia on the gill margins.A basidium is a microscopic, spore-producing structure found on the hymenophore of fruiting bodies of basidiomycete fungi. The presence of basidia is one of the main...
(the spore-bearing cell). When in potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
(KOH) solution, the spores appear tawny or darker rusty-brown, with an apical callus. The basidia are four-spored (rarely with a very few two-spored ones), roughly cylindrical when producing spores, but with a slightly tapered base, and measure 21–29 by 5–8.4 µm.
Cystidia are cells of the fertile 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...
that do not produce spores. These sterile cells, which are structurally distinct from the basidia, are further classified according to their position. In G. marginata, the pleurocystidia (cystidia from the gill sides) are 46–60 by 9–12 µm, thin-walled, and 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...
in KOH, fusoid to ventricose
Ventricose
In mycology, Ventricose is a condition in which the cystidia, lamella or stipe of a mushroom is swollen in the middle....
in shape with wavy necks and blunt to subacute apices (3–6 µm diameter near apex). The cheilocystidia (cystidia on the gill edges) are similar in shape but often smaller than the pleurocystidia, abundant, with no club-shaped or abruptly tapering (mucronate) cells present. Clamp connection
Clamp connection
A clamp connection is a structure formed by growing hyphal cells of certain fungi. It is created to ensure each septum, or segment of hypha separated by crossed walls, receives a set of differing nuclei, which are obtained through mating of hyphae of differing sexual types...
s are present in the hyphae.
Similar species
Galerina marginata may be mistaken for a few edible mushroomEdible 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...
species. Pholiota mutabilis produces fruit bodies roughly similar in appearance and also grows on wood, but may be distinguished from G. marginata by its stems bearing scales up to the level of the ring, and from growing in large clusters (which is not usual of G. marginata). However, the possibility of confusion is such that this good edible species is "not recommended to those lacking considerable experience in the identification of higher fungi." Furthermore, microscopic examination shows smooth spores in Pholiota. G. marginata may be easily confused with other edibles such as Armillaria mellea
Armillaria mellea
Armillaria mellea is a plant pathogen and a species of Honey fungus. It causes Armillaria root rot in many plant species. The mushrooms are edible but some people may be intolerant to them. The fungus produces mushrooms around the base of trees it has infected...
and Kuehneromyces mutabilis
Kuehneromyces mutabilis
Kuehneromyces mutabilis , commonly known as the Sheathed Woodtuft, is an edible fungus which grows in clumps on tree stumps or other dead wood. A few other species have been described in the genus Kuehneromyces, but K...
. Regarding the latter species, one source notes "Often, G. marginata bears an astonishing resemblance to this fungus, and it requires careful and acute powers of observation to distinguish the poisonous one from the edible one." K. mutabilis may be distinguished by the presence of scales on the stem below the ring, the larger cap, which may reach a diameter of 6 cm (2.4 in), and spicy or aromatic odor of the flesh. The related K. vernalis is a rare species and even more similar in appearance to G. marginata. Examination of microscopic characteristics is typically required to reliably distinguish between the two, revealing smooth spores with a germ pore
Germ pore
A germ pore is a small pore in the outer wall of a fungal spore through which the germ tube exits upon germination. It can be apical or eccentric in its location, and, on light microscopy, may be visualized as a lighter coloured area on the cell wall....
.
Another potential edible lookalike is the "velvet foot", Flammulina velutipes. This species has gills that are white to pale yellow, a white spore print, and spores that are elliptical, smooth, and measure 6.5–9 by 2.5–4 µm. A rough resemblance has also been noted with the edible Hypholoma capnoides
Hypholoma capnoides
Hypholoma capnoides is an edible mushroom which like its poisonous or suspect relatives H. fasciculare and H. sublateritium grows on decaying wood, for example in tufts on old tree stumps. Anyone thinking to eat this mushroom needs to be able to distinguish it from Sulphur Tuft, which is more...
, as well as Conocybe filaris
Conocybe filaris
Conocybe filaris is a common lawn mushroom which is widely distributed and especially common in the pacific northwest. It contains the same mycotoxins as the death cap. It is also known as Pholiotina filaris.- Description :...
, another poisonous amatoxin-containing species.
Habitat and distribution
Galerina marginata is a saprobicDetritivore
Detritivores, also known as detritophages or detritus feeders or detritus eaters or saprophages, are heterotrophs that obtain nutrients by consuming detritus . By doing so, they contribute to decomposition and the nutrient cycles...
fungus, obtaining nutrients by breaking down organic matter. It is known to have most of the major classes of secreted enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s that dissolve plant cell wall
Cell wall
The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...
polysaccharide
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...
s, and has been used as a model saprobe in recent studies of ectomycorrhizal
Mycorrhiza
A mycorrhiza is a symbiotic association between a fungus and the roots of a vascular plant....
fungi. Because of its variety of enzymes capable of breaking down wood and other lignocellulosic materials, the Department of Energy Joint Genome Institute (JGI) is currently sequencing its genome. The fungus is typically reported to grow on or near the wood of conifers, although it has been observed to grow on hardwoods as well. Fruit bodies may grow solitarily, but more typically in groups or small clusters, and appear in the summer to autumn. Sometimes, they may grow on buried wood and thus appear to be growing on soil.
Galerina marginata is widely distributed throughout the Northern Hemisphere, found in North America, Europe, Japan, Iran, continental Asia, and the Caucasus
Caucasus
The Caucasus, also Caucas or Caucasia , is a geopolitical region at the border of Europe and Asia, and situated between the Black and the Caspian sea...
. In North America, it has been collected as far north as the boreal forest of Canada
Boreal forest of Canada
Canada's boreal forest comprises about one third of the circumpolar boreal forest that rings the northern hemisphere, mostly north of the 50th parallel. Other countries with boreal forest include Russia, which contains the majority, and the Scandinavian and Nordic countries . The boreal region in...
and subarctic
Subarctic
The Subarctic is a region in the Northern Hemisphere immediately south of the true Arctic and covering much of Alaska, Canada, the north of Scandinavia, Siberia, and northern Mongolia...
and arctic
Arctic
The Arctic is a region located at the northern-most part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Greenland, the United States, Norway, Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost...
habitats in Labrador
Labrador
Labrador is the distinct, northerly region of the Canadian province of Newfoundland and Labrador. It comprises the mainland portion of the province, separated from the island of Newfoundland by the Strait of Belle Isle...
, and south to Jalisco, Mexico. It is also found in Australia.
Toxicity
The toxins found in Galerina marginata are known as amatoxinAmatoxin
Amatoxins are a subgroup of at least eight toxic compounds found in several genera of poisonous mushrooms, most notably Amanita phalloides and several other members of the genus Amanita, as well as some Conocybe, Galerina and Lepiota mushroom species.-Structure:The compounds have a similar...
s. Amatoxins belong to a family of bicyclic octapeptide derivatives composed of an amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
ring bridged by a sulphur atom and characterized by differences in their side groups
Substituent
In organic chemistry and biochemistry, a substituent is an atom or group of atoms substituted in place of a hydrogen atom on the parent chain of a hydrocarbon...
; these compounds are responsible for more than 90% of fatal mushroom poisoning
Mushroom poisoning
Mushroom poisoning refers to harmful effects from ingestion of toxic substances present in a mushroom. These symptoms can vary from slight gastrointestinal discomfort to death. The toxins present are secondary metabolites produced in specific biochemical pathways in the fungal cells...
s in humans. The amatoxins inhibit the enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
RNA polymerase II
RNA polymerase II
RNA polymerase II is an enzyme found in eukaryotic cells. It catalyzes the transcription of DNA to synthesize precursors of mRNA and most snRNA and microRNA. A 550 kDa complex of 12 subunits, RNAP II is the most studied type of RNA polymerase...
, which copies the genetic code
Genetic code
The genetic code is the set of rules by which information encoded in genetic material is translated into proteins by living cells....
of DNA into messenger RNA
Messenger RNA
Messenger RNA is a molecule of RNA encoding a chemical "blueprint" for a protein product. mRNA is transcribed from a DNA template, and carries coding information to the sites of protein synthesis: the ribosomes. Here, the nucleic acid polymer is translated into a polymer of amino acids: a protein...
molecules. The toxin naturally accumulates in liver cells
Hepatocyte
A hepatocyte is a cell of the main tissue of the liver. Hepatocytes make up 70-80% of the liver's cytoplasmic mass.These cells are involved in:* Protein synthesis* Protein storage* Transformation of carbohydrates...
, and the ensuing disruption of metabolism accounts for the severe liver dysfunction cause by amatoxins. Amatoxins also lead to kidney failure because, as the kidneys attempt to filter out poison, it damages the convoluted tubules and reenters the blood to recirculate and cause more damage. Initial symptoms after ingestion include severe abdominal pain
Abdominal pain
Abdominal pain can be one of the symptoms associated with transient disorders or serious disease. Making a definitive diagnosis of the cause of abdominal pain can be difficult, because many diseases can result in this symptom. Abdominal pain is a common problem...
, vomiting
Vomiting
Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...
, and diarrhea
Diarrhea
Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...
which may last for six to nine hours. Beyond these symptoms, toxins severely affect the liver which results in gastrointestinal bleeding
Gastrointestinal bleeding
Gastrointestinal bleeding or gastrointestinal hemorrhage describes every form of hemorrhage in the gastrointestinal tract, from the pharynx to the rectum. It has diverse causes, and a medical history, as well as physical examination, generally distinguishes between the main forms...
, a coma
Coma
In medicine, a coma is a state of unconsciousness, lasting more than 6 hours in which a person cannot be awakened, fails to respond normally to painful stimuli, light or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as...
, kidney failure, or even death, usually within seven days of consumption.
Galerina marginata was shown in various studies to contain the amatoxins α-amanitin
Alpha-amanitin
alpha-Amanitin or α-amanitin is a cyclic peptide of eight amino acids. It is possibly the most deadly of all the amatoxins, toxins found in several species of the Amanita genus of mushrooms, one being the Death cap as well as the Destroying angel, a complex of similar species, principally A....
and γ-amanitin
Gamma-amanitin
gamma-Amanitin or γ-amanitin is a cyclic peptide of eight amino acids. It is an amatoxin, a group of toxins isolated from and found in several members of the Amanita genus of mushrooms, one being the Death cap as well as the Destroying angel, a complex of similar species, principally...
, first as G. venenata, then as G. marginata and G. autumnalis. The ability of the fungus to produce these toxins was confirmed by growing the mycelium
Mycelium
thumb|right|Fungal myceliaMycelium is the vegetative part of a fungus, consisting of a mass of branching, thread-like hyphae. The mass of hyphae is sometimes called shiro, especially within the fairy ring fungi. Fungal colonies composed of mycelia are found in soil and on or within many other...
as a liquid culture
Microbiological culture
A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture media under controlled laboratory conditions. Microbial cultures are used to determine the type of organism, its abundance in the sample being tested,...
(only trace amounts of ß-amanitin
Beta-amanitin
beta-Amanitin or β-amanitin is a cyclic peptide of eight amino acids. It is an amatoxin, a group of toxins isolated from and found in several members of the Amanita genus of mushrooms, one being the Death cap as well as the Destroying angel, a complex of similar species, principally A. virosa...
were found). G. marginata is thought to be the only species of the amatoxin-producing genera that will produce the toxins while growing in culture. Both amanitins were quantified in G. autumnalis (1.5 mg/g 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...
) and G. marginata (1.1 mg/g dry weight). Later experiments confirmed the occurrence of γ-amanitin and ß-amanitin in German specimens of G. autumnalis and G. marginata and revealed the presence of the three amanitins in the fruit bodies of G. unicolor. Although some mushroom field guide
Field guide
A field guide is a book designed to help the reader identify wildlife or other objects of natural occurrence . It is generally designed to be brought into the 'field' or local area where such objects exist to help distinguish between similar objects...
s claim that the species (as G. autumnalis) also contains phallotoxin
Phallotoxin
The phallotoxins consist of at least seven compounds, all of which are bicyclic heptapeptides , isolated from the death cap . Phalloidin had been isolated in 1937 by Feodor Lynen, Heinrich Wieland's student and son-in-law, and Ulrich Wieland of the University of Munich...
s, scientific evidence does not support this contention. A 2004 study determined that the amatoxin content of G. marginata varied from 78.17 to 243.61 µg/g of fresh weight. In this study, the amanitin amounts from certain Galerina specimens were higher than those from some Amanita phalloides, a European fungus generally considered as the richest in amanitins. The authors suggest that "other parameters such as extrinsic factors (environmental conditions) and intrinsic factors (genetic properties) could contribute to the significant variance in amatoxin contents from different specimens." The lethal dose of amatoxins has been estimated to be about 0.1 mg/kg human body weight, or even lower. Based on this value, the ingestion of 10 G. marginata fruit bodies containing about 250 µg of amanitins per gram of fresh tissue could poison a child weighing approximately 20 kilograms (44.1 lb). However, a 20-year retrospective study of more than 2100 cases of amatoxin poisonings from North American and Europe showed that few cases were due to ingestion of Galerina species. This low frequency may be attributed to the mushroom's nondescript appearance as a "little brown mushroom" leading to it being overlooked by collectors, and by the fact that 21% of amatoxin poisonings were caused by unidentified species.
The toxicity of certain Galerina species has been known for a century. In 1912, 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...
reported a human poisoning case due to G. autumnalis. In 1954, a poisoning was caused by G. venenata. Between 1978 and 1995, ten cases caused by amatoxin-containing Galerinas were reported in the literature. Three European cases, two from Finland and one from France were attributed to G. marginata and G. unicolor, respectively. Seven North American exposures included two fatalities from Washington due to G. venenata, with five cases reacting positively to treatment; four poisonings were caused by G. autumnalis from Michigan and Kansas, in addition to poisoning caused by an unidentified Galerina species from Ohio. Several poisonings have been attributed to collectors consuming the mushrooms after mistaking them for hallucinogenic Psilocybe
Psilocybe
Psilocybe is a genus of small mushrooms growing worldwide. This genus is best known for its species with psychedelic or hallucinogenic properties, widely known as "magic mushrooms", though the majority of species do not contain hallucinogenic compounds...
species, such as P. stuntzii
Psilocybe stuntzii
Psilocybe stuntzii, also known as Stuntz's Blue legs and Blue Ringers it is a psilocybin mushroom of the Strophariaceae family, having psilocybin andpsilocin as main active compounds....
.