Everything about Gyromitra Esculenta totally explained
Gyromitra esculenta is an
ascomycete fungus from the genus
Gyromitra widely distributed across Europe and North America, and one of several species of fungi known as
False morels. It is normally found in sandy soils under
coniferous trees in spring and early summer. The fruiting body, or mushroom, is an irregular brain-shaped
cap dark brown in colour which can reach 10 cm (4
in) high and 15 cm (6 in) wide, perched on a stout white
stalk up to 6 cm (2½ in) high.
Although
Gyromitra esculenta is highly toxic and potentially fatal if eaten raw, it's described by
aficionados as one of the best of all culinary mushrooms. It is popular in
Scandinavia, Eastern Europe, and the upper
Great Lakes region of
North America. In
Finland, it may be sold fresh, but it must be accompanied by warnings and instructions on correct preparation. Though it's still commonly consumed after
parboiling, recent evidence suggests that even that procedure may not make the fungus entirely safe; thus raising concerns of risk even when prepared properly. When consumed, the false morel's principal active agent
gyromitrin, is metabolized into the toxic compound
monomethylhydrazine (MMH).
Taxonomy and naming
The fungus was first described by
mycologist Christian Hendrik Persoon as
Helvella esculenta in 1800, before being placed in the genus
Gyromitra by
Fries in 1849, thus gaining its current accepted name. The generic name is derived from the
Greek terms
gyros/γυρος 'round' and
mitra/μιτρα 'headband'. Its specific epithet is derived from the
Latin esculentus, 'edible'.
It is known by a variety of common names such as
lorchel,
brain mushroom,
turban fungus, or
beefsteak mushroom/morel. The Finnish name
Korvasieni is derived from the terms
korva 'ear', and
sieni 'mushroom/fungus',
while the Swedish
Stenmurkla is
Sten 'stone' and
murkla 'morel'.
Gyromitra esculenta is a member of a family of fungi known as "
False morels", named as such for their resemblance to the highly regarded true morels of the genus
Morchella. The grouping also includes other species of the genus
Gyromitra, such as
G. infula (elfin saddle),
G. caroliniana and
G. gigas (Snow morel). While some of these species contain little to no gyromitrin, many sources recommend treating them all as poisonous, since their similar appearance and significant intraspecific variation can make reliable identification difficult.
The more distantly related ascomycete mushrooms of the genus
Verpa, such as
V. bohemica and
V. conica, are also known as false morels, early morels or thimble morels (and, like the
Gyromitra, are also eaten by some and considered poisonous by others).
Analysis of the
ribosomal DNA of many of the
Pezizales showed
Gyromitra esculenta and the other false morels to be most closely related to the genus
Discina, and also
Pseudorhizina,
Hydnotrya, and only distantly related to
Helvella. Thus the four genera are now included in the family
Discinaceae.
Description
The irregularly shaped
cap may be up to 10 cm (4
in) high and 15 cm (6 in) wide. Initially smooth, it becomes progressively more wrinkled as it ages, resembling a brown
brain when mature, and is attached to the
stipe or stem at several points. The cap colour may be various shades of reddish-, chestnut-, purplish-, bay-, dark or sometimes golden-brown. Those from California have been reported as often more reddish-brown in colour.
It is somewhat similar in appearance to the true morel (
Morchella sp.), although the latter is more symmetric and looks more like a pitted gray, tan, or brown
sponge. False morels (
G. esculenta) are also generally darker and larger than true morels.
Distribution and habitat
Gyromitra esculenta grows on sandy soil in
coniferous and
deciduous woodlands, although it prefers the former. Among conifers it's mostly found under pines (
Pinus spp.), but also sometimes aspen (
Populus spp.). It is an early mushroom, and the hunting period is from April to July, sometimes appearing with the melting snow. The growth can be promoted by breaking the terrain further in places where false morel is known to grow.
Although more abundant in
montane and northern coniferous woodlands such as the
Sierra Nevada and the
Cascade Range in northwestern North America,
Gyromitra esculenta is found widely across the continent, It is also common in Central Europe and less commonly in the east, and more montane areas than lowlands. It has been recorded from
Northern Ireland, from
Uşak Province in Western Turkey, and from the vicinity of
Kaş in the
Antalya Province of Turkey's southern coast.
Toxicity
Toxic reactions were known from the early 20th century at least, though the wide range in effects meant that some experts speculated the reaction was more of an allergic one related to the consumer, or misidentification, rather than innate toxicity of the fungus. Some would suffer severely or perish while others exhibited no symptoms after eating similar amounts of mushrooms from a single dish. Yet others would be poisoned after eating the mushroom for many years without ill-effects. However, the fungus is now widely recognized as potentially deadly.
Gyromitra esculenta contains the poison
gyromitrin and although these mushrooms are only rarely involved in poisonings in either
North America or Western
Europe intoxications are seen frequently in eastern Europe and
Scandinavia. At one time up to 23% of mushroom fatalities each year were attributed to this species in
Poland. and there's anecdotal evidence fungi west of the
Rocky Mountains in North America contain less toxin than those to the east. However, poisonings in the west have been reported,
Biochemistry
The identity of the toxic constituents eluded researchers until 1968, when
N-methyl-
N-formylhydrazone acetaldehyde, better known as
gyromitrin, was isolated. Gyromitrin is a
volatile water-soluble hydrazine compound metabolized in the body into
monomethylhydrazine (MMH). MMH is a strongly
reductive substance. Other
N-methyl-
N-formylhydrazone derivatives have been isolated in subsequent research, although they're present in smaller amounts. These other derivatives likely also yield monomethylhydrazine when metabolized in the body. However, it remains unclear how much each contributes to the false morel's toxicity.
The toxins react with pyridoxal-5-phosphate, which is the activated form of pyridoxine, forming a hydrazone. Overall this results in diminished formation of the neurotransmitter
GABA via decreased activity of
glutamic acid decarboxylase. This interference causes the neurological symptoms. MMH also causes oxidative stress leading to
methemoglobinemia. Inhibition of
diamine oxidase (histaminase) causes elevation of
histamine levels resulting in headaches, nausea, vomiting, and abdominal pain.
Symptoms
The symptoms of poisoning are typically
gastrointestinal and
neurological. The symptoms occur within 6-12 hours of consumption, although cases of more severe poisoning may present sooner - as little as 2 hours after ingestion. Initial symptoms are gastrointestinal, with sudden onset of
nausea, vomiting, and watery
diarrhea which may be bloodstained.
Dehydration may develop if the vomiting or diarrhea is severe. Dizziness, lethargy,
vertigo, tremor,
ataxia,
nystagmus, and headaches develop soon after; In most cases of poisoning, symptoms don't progress from these initial symptoms and patients recover after 2 to 6 days of illness.
liver damage, and neurological dysfunction including seizures and coma. These signs usually develop within 1-3 days in serious cases. Cases of severe poisoning may progress to a terminal neurological phase, with
delirium, muscle fasciculations and seizures, and
mydriasis progressing to
coma, circulatory collapse, and
respiratory arrest. Death, if it occurs, is usually after 5 to 7 days.
Treatment
Treatment is mainly supportive; gastric decontamination with
activated charcoal may be beneficial if medical attention is sought within a few hours of consumption. However, symptoms take often longer than this to develop and patients don't usually present for treatment until many hours after ingestion, thus limiting its effectiveness. If patients have severe vomiting or diarrhea
IV fluids can be used to rehydrate the patient. Monitoring of biochemical parameters such as methemoglobin levels, electrolytes, liver and kidney function, urinalysis, and
complete blood count is undertaken and any abnormalities are corrected.
Dialysis can be used if kidney function is impaired or the kidneys are failing. Hemolysis may require a
blood transfusion to replace the lost red blood cells, while methemoglobinemia is treated with intravenous
methylene blue.
Pyridoxine, also known as
vitamin B6, can be used as an antidote to MMH as MMH
inhibits a pyridoxine-dependent step in the synthesis of the
neurotransmitter GABA. By giving additional pyridoxine GABA synthesis can continue and symptoms are relieved. Pyridoxine is given at a dose of 25 mg/kg, if symptoms don't improve this can be repeated up to a maximum total daily dose of 15 to 30 g. Pyridoxine doesn't decrease hepatic toxicity and is only useful for the neurological symptoms.
Benzodiazepines are given to control seizures, they also modulate GABA receptors and may increase the effect of pyridoxine. Additionally MMH inhibits the chemical transformation of
folic acid into its active form,
folinic acid, this can be treated by folinic acid given at 20-200 mg daily. The toxins may be cumulative and even small amounts may have a carcinogenic effect. Although cancer caused by this mushroom hasn't been observed in humans, Similarly in
Sweden, the
Swedish National Food Administration warns it isn't fit for human consumption, and restricts purchase of mushrooms to restaurants alone. It is still highly regarded and consumed in
Bulgaria, being also sold in markets and picked for export there. In some countries such as
Spain, especially in the eastern
Pyrenees, they're traditionally considered a delicacy, and many people report consuming them for many years with no ill effects. Despite this, all false morels are listed as hazardous in official mushroom lists published by the Catalan Government in Spain. Selling and purchasing fresh false morels is legal according to Finnish law, where it's also highly regarded. However, the mushrooms are required by law to be accompanied with a warning that they're poisonous and legally prescribed preparation instructions. False morels are also sold prepared and canned, in which case they're ready to be used. As well as Europe,
Gyromitra esculenta is consumed in the
Great Lakes region and some western states in the United States.
Preparation
To render false morels edible most of the gyromitrin must be removed. The recommended procedure involves either first drying and then boiling the mushrooms, or boiling the fresh mushrooms directly. To prepare fresh mushroom it's recommended that they're cut into small pieces and boiled twice in copious amounts of water, at least three parts water to one part chopped mushrooms, for at least five minutes, after each boiling the mushroom should be rinsed thoroughly in clean water.. The gyromitrin will dissolve in the water where it'll remain, therefore the parboiling water must be discarded and replaced with fresh water after each boiling. This process is called
parboiling, equalling
leaching as a
unit operation; the gyromitrin is leached off the mushrooms. Drying the mushrooms can also reduce the concentration of gyromitrin; ten days of open air desiccation leads to the loss of 90% of gyromitrin. Poorly ventilated spaces allow vapor to accumulate, resulting in gyromitrin poisoning. If boiling the mushrooms indoors, care should be taken to ensure adequate ventilation, and, if symptoms of gyromitrin poisoning appear, immediately seek fresh air. Even after boiling, small amounts of gyromitrin remain in the mushrooms. Given the possibility of accumulation of toxins, repeated consumption isn't recommended.
Prospects for cultivation
Despite its toxicity,
Gyromitra esculenta is clearly highly regarded gastronomically by many. Toxin levels corroborate well between mycelium and fruiting bodies, and strains with much lower concentrations of gyromitrin have been discovered. Furthermore, the fungus has been successfully grown to fruiting in culture. Thus there's scope for future research into cultivation of safer strains. Enthusiasts in Finland have been reported burying newspaper inoculated with the fungus in the ground in autumn and returning the following spring to collect mushrooms.
Further Information
Get more info on 'Gyromitra Esculenta'.
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