View source for Astraeus hygrometricus

{{short description|Cosmopolitan species of fungus in the family Diplocystaceae.}}
{{stack begin}}
{{speciesbox
| image = Astraeus hygrometricus 122239.jpg
| image_caption =
| species = hygrometricus
| genus = Astraeus (fungus)
| authority = ([[Pers.]]) [[Andrew P. Morgan|Morgan]] (1889)
| synonyms_ref = <ref name="urlMycoBank: Astraeus hygrometricus"/>
| synonyms = ''Lycoperdon stellatus'' <small>[[Scop.]] (1772)</small><br>
''Geastrum hygrometricum'' <small>Pers. (1801)</small><br>
''Geastrum fibrillosum'' <small>[[Schwein.]] (1822)</small><br>
''Geastrum stellatum'' <small>(Scop.) [[Wettst.]] (1885)</small><br>
''Astraeus stellatus'' <small>[[E.Fisch.]] (1900)</small>
}}
{{mycomorphbox
| name = ''Astraeus hygrometricus''
| capShape = no
| hymeniumType = gleba
| whichGills = NA
| stipeCharacter = NA
| ecologicalType = mycorrhizal
| sporePrintColor = brown
| howEdible = inedible
}}
{{stack end}}
'''''Astraeus hygrometricus''''', commonly known as the '''hygroscopic earthstar''', the '''barometer earthstar''', or the '''false earthstar''', is a species of [[fungus]] in the family [[Diplocystaceae]]. Young specimens resemble a [[puffball]] when unopened. In maturity, the mushroom displays the characteristic [[Earthstar fungus|earthstar]] shape that is a result of the outer layer of [[fruit body]] tissue splitting open in a star-like manner. The false earthstar is an [[mycorrhizal|ectomycorrhizal]] species that grows in association with various trees, especially in sandy soils. ''A.&nbsp;hygrometricus'' was previously thought to have a [[cosmopolitan distribution]], though it is now thought to be restricted to Southern Europe, and ''Astraeus'' are common in temperate and tropical regions.<ref name=":0">{{cite journal | vauthors = Phosri C, Martín MP, Watling R | title = Astraeus: hidden dimensions | journal = IMA Fungus | volume = 4 | issue = 2 | pages = 347–56 | date = December 2013 | pmid = 24563840 | pmc = 3905946 | doi = 10.5598/imafungus.2013.04.02.13 }}</ref> Its [[common name]]s refer to the fact that it is [[hygroscopic]] (water-absorbing) and can open up its rays to expose the spore sac in response to increased humidity, then close them up again in drier conditions. The rays have an irregularly cracked surface, while the spore case is pale brown and smooth with an irregular slit or tear at the top. The [[gleba]] is white initially, but turns brown and powdery when the [[spore]]s mature. The spores are reddish-brown and roughly spherical with minute warts, measuring 7.5–11 [[micrometre|micrometer]]s in diameter.

Despite a similar overall appearance, ''A.&nbsp;hygrometricus'' is not related to the true earthstars of genus ''[[Geastrum]]'', although historically, they have been [[Taxonomy (biology)|taxonomically]] confused. The species was first described by [[Christiaan Hendrik Persoon]] in 1801 as ''Geastrum hygrometricus''. In 1885, [[Andrew P. Morgan]] proposed that differences in microscopic characteristics warranted the creation of a new genus ''[[Astraeus (fungus)|Astraeus]]'' distinct from ''Geastrum''; this opinion was not universally accepted by later authorities. Several Asian populations formerly thought to be ''A.&nbsp;hygrometricus'' were renamed in the 2000s once [[Phylogenetics|phylogenetic]] analyses revealed they were unique ''Astraeus'' species, including ''[[Astraeus asiaticus|A.&nbsp;asiaticus]]'' and ''[[Astraeus odoratus|A.&nbsp;odoratus]]''. Similarly, in 2013, North American populations were divided into ''[[Astraeus pteridis|A. pteridis]]'', [[Astraeus morganii|''A. morganii'']], and [[Astraeus smithii|''A. smithii'']] on the basis of [[molecular phylogenetics]]. This research suggests that the type specimen of ''Astraeus hygrometricus'' originates in a population restricted to Europe between Southern France and Turkey, with ''[[Astraeus telleriae|A. telleriae]]'' found nearby in Spain and Greece.<ref name=":0" /> Research has revealed the presence of several [[biological activity|bioactive]] chemical compounds in ''Astraeus'' fruit bodies. North American field guides typically rate ''A.&nbsp;hygrometricus'' as inedible; while this may be accurate for the now-separate North American species, ''A.&nbsp;hygrometricus'' is commonly consumed in [[South Asia|South]] and [[Southeast Asia]].

==Taxonomy, naming, and phylogeny==

Because this species resembles the earthstar fungi of ''Geastrum'', it was placed in that genus by early authors, starting with [[Christian Hendrik Persoon]] in 1801<ref name=Persoon1801/> (as ''Geaster'', an alternate spelling of ''Geastrum''). According to the American botanist [[Andrew P. Morgan]], however, the species differed from those of ''Geastrum'' in not having open chambers in the young gleba, having larger and branched [[capillitium]] threads, not having a true [[hymenium]], and having larger spores. Accordingly, Morgan set Persoon's ''Geaster hygrometricum'' as the [[type species]] of his new genus ''Astraeus'' in 1889.<ref name=Morgan1889/> Despite Morgan's publication, some authorities in the following decades continued to classify the species in ''Geastrum''.<ref name=Coker1928/><ref name=Lloyd1902/> The New-Zealand based mycologist [[Gordon Herriot Cunningham]] explicitly transferred the species back to the genus ''Geastrum'' in 1944, explaining: <blockquote>The treatment of this species by certain taxonomists well illustrates the pitfalls that lie in wait for those who worship at the shrine of [[ontogenic]] classification ... The only feature of those outlined in which the species differs from others of ''Geastrum'' is the somewhat primitive hymenium. In the developing plant the glebal cavities are separated by tramal plates so tenuous as to be overlooked by the uncritical worker. Each cavity is filled with basidia somewhat irregularly arranged in clusters (like those of ''[[Scleroderma]]'') and not in the definite palisade of the species which have been studied. This difference disappears as maturity is reached, when plants resemble closely the fructification of any other member of the genus. The taxonomist is then unable to indicate any point of difference by which "''Astraeus''" may be separated from ''Geastrum'', which indicates that the name should be discarded.<ref name=Cunningham1944/></blockquote> Cunningham's treatment was not followed by later authorities, who largely considered ''Astraeus'' a distinct genus. According to the taxonomical authority [[MycoBank]],<ref name="urlMycoBank: Astraeus hygrometricus"/> [[synonym (biology)|synonyms]] of ''Astraeus hygrometricus'' include ''Lycoperdon stellatus'' Scop. (1772);<ref name=Scopoli1772/> ''Geastrum fibrillosum'' Schwein. (1822);<ref name=Schweinitz1822/> ''Geastrum stellatum'' (Scop.) Wettst. (1885); and ''Astraeus stellatus'' E.Fisch. (1900).<ref name=Engler1900/>

''Astraeus hygrometricus'' has been given a number of [[common name|colloquial names]] that allude to its hygroscopic behavior, including the "[[hygrometer]] earthstar", the "hygroscopic earthstar", the "[[barometer]] earthstar", and the "water-measure earthstar".<ref name=Roody2003/><ref name=McKnight1987/> The resemblance to ''Geastrum'' species (also known as true earthstars) accounts for the common name "false earthstar".<ref name=Alexopoulos1996/> The [[specific name (botany)|specific name]] is derived from the [[Greek language|Greek]] words {{lang|grc|ὑγρός}} ({{lang|grc-Latn|hygros}}) 'wet' and {{lang|grc|μέτρον}} ({{lang|grc-Latn|metron}}) 'measure'.<ref name=Rea1922/> The [[German Mycological Society]] selected the species as their "Mushroom of the Year" in 2005.<ref name=DGfM/>

Studies in the 2000s showed that several species from Asian collection sites labelled under the specific epithet ''hygrometricus'' were actually considerably variable in a number of [[macroscopic scale|macroscopic]] and [[microscopic scale|microscopic]] characteristics.<ref name=Phosri2004/> Molecular studies of the [[DNA sequence]]s of the [[internal transcribed spacer|ITS]] region of the [[ribosomal DNA]] from a number of ''Astraeus'' specimens from around the world have helped to clarify phylogenetic relationships within the genus. Based on these results, two Asian "''hygrometricus''" populations have been described as new species: ''[[Astraeus asiaticus|A.&nbsp;asiaticus]]''<ref name=Phosri2004/> and ''[[Astraeus odoratus|A.&nbsp;odoratus]]'' (synonymous with Petcharat's ''A.&nbsp;thailandicus'' described in 2003<ref name=Petcharat2003/>). Preliminary DNA analyses suggests that the European ''A.&nbsp;hygrometricus'' described by Persoon is a different species than the North American version described by Morgan, and that the European population may be divided into two distinct [[phylotype]]s, from France (''A. hygrometricus'') and from the Mediterranean (''[[Astraeus telleriae|A. telleriae]]'').<ref name=Phosri2007/><ref name=Fangfuk2010/> A follow-up analysis from 2013 named two new North American species: ''[[Astraeus morganii|A. morganii]]'' from the Southern US and Mexico and ''[[Astraeus smithii|A. smithii]]'' from the Central and Northern United States, and grouped western US specimens in ''[[Astraeus pteridis|A. pteridis]]''.<ref name=":0" /> A 2010 study identified a Japanese species, previously identified as ''A.&nbsp;hygrometricus'', as genetically distinct; it has yet to be officially named.<ref name=Fangfuk2010/>

A form of the species found in Korea and Japan, ''A.&nbsp;hygrometricus'' var. ''koreanus'', was named by V.J. Stanĕk in 1958;<ref name=Stanek1958/> it was later (1976) published as a distinct species—''A.&nbsp;koreanus''—by [[Hanns Kreisel]].<ref name=Kreisel1976/> As pointed out by Fangfuk and colleagues, clarification of the proper name for this taxon must await analysis of ''A.&nbsp;hygrometricus'' var. ''koreanus'' specimens from the [[type locality (biology)|type locality]] in North Korea.<ref name=Fangfuk2010/>

==Description==
[[File:Astraeus hygrometricus 113828.jpg|left|thumb|A collection of fruit bodies]]
Young specimens of ''A.&nbsp;hygrometricus'' have roughly spherical [[sporocarp (fungi)|fruit bodies]] that typically start their development partially embedded in the [[substrate (biology)|substrate]]. A smooth whitish mycelial layer covers the fruit body, and may be partially encrusted with debris. As the fruit body matures, the mycelial layer tears away, and the outer tissue layer, the [[peridium|exoperidium]], breaks open in a star-shaped ([[wikt:stellate|stellate]]) pattern to form 4–20 irregular "rays". This simultaneously pushes the fruit body above ground to reveal a round spore case enclosed in a thin papery endoperidium. The rays open and close in response to levels of moisture in the environment, opening up in high humidity, and closing when the air is dry.<ref name=Schaechter1998/> This is possible because the exoperidium is made of several different layers of tissue; the innermost, fibrous layer is hygroscopic, and curls or uncurls the entire ray as it loses or gains moisture from its surroundings.<ref name=Gaumann1928/> This adaptation enables the fruit body to disperse spores at times of optimum moisture, and reduce evaporation during dry periods.<ref name=Foy1991/><ref name="urlFotM"/> Further, dry fruit bodies with the rays curled up may be readily blown about by the wind, allowing them to scatter spores from the pore as they roll.<ref name=Schaechter1998/>
{{Quote box |width = 33% |quote= "This veritable barometer is the most theatrical of all the earthstars. A few minutes immersion in water will open up old, dried-up specimens that seem as tightly closed as clenched fists."|source = [[David Arora]] in ''[[Mushrooms Demystified]]''<ref name=Arora1986/>}}
The fruit body is {{convert|1|–|8|cm|in|abbr=on|round=0.5}} in diameter from tip to tip when expanded.<ref name=Arora1986/> The exoperidium is thick, and the rays are typically [[wikt:areolate|areolate]] (divided into small areas by cracks and crevices) on the upper surface,<ref name=Orr1979/> and are dark grey to black. The spore case is [[Sessility (botany)|sessile]] (lacking a [[stipe (mycology)|stalk]]), light gray to tan color and {{convert|1|to|3|cm|in|1|abbr=on}} broad with a felt-like or scurfy (coated with loose scaly crust) surface; the top of the spore case is opened by an irregular slit, tear or pore.<ref name=Phillips1991/> The gleba is white and solid when young, and divided into oval [[locule]]s—a characteristic that helps to distinguish it from ''Geastrum''.<ref name=Miller2006/> The gleba becomes brown and powdery as the specimen matures.<ref name=Jordan2004/> Small dark hairlike threads ([[rhizomorph]]s) extend from the base of the fruit body into the substrate. The rhizomorphs are fragile, and often break off after maturity.<ref name=Coker1928/>
[[File:Astraeus hygrometricus1928.jpg|left|300px|thumb|Mature fruit body (''left''); cross-section of young fruit body (''right'')]]
The spores are spherical or nearly so, reddish-brown, thick-walled and verrucose (covered with warts and spines). The spores' dimensions are 7–11&nbsp;[[micrometre|μm]];<ref name= Healy2008/> the warts are about 1&nbsp;μm long.<ref name=Ellis1990/> The spores are non-[[amyloid]], and will not stain with iodine from [[Melzer's reagent]].<ref name=Roody2003/> The use of [[scanning electron microscopy]] has shown that the spines are 0.90–1.45&nbsp;μm long, rounded at the tip, narrow, tapered, and sometime joined at the top.<ref name=Phosri2004/> The [[capillitia]] (masses of thread-like sterile fibers dispersed among the spores) are branched, 3.5–6.5&nbsp;μm in diameter, and [[hyaline]] (translucent).<ref name=Coker1928/> The [[basidia]] (spore-bearing cells) are four- to eight-spored,<ref name=Coker1928/> with very short [[sterigmata]].<ref name=Pegler1995/> The basidia are arranged in long strings of clusters; individual basidia measure 11–15 by 18–24&nbsp;μm. The threads of the capillitia arise from the inner surface of the peridium, and are thick-walled, long, interwoven, and branched, measuring 3–5.5&nbsp;μm thick.<ref name=Coker1928/> The exoperidium (the outer layer of tissue, comprising the rays) is made of four distinct layers of tissue: the mycelial layer contains branched [[hypha]]e that are 4–6&nbsp;μm in diameter; the hyphae of the fibrous layer are 6–8&nbsp;μm diameter and branched; the [[collenchyma]]-type layer has branched hyphae of 3–4&nbsp;μm diameter; the soft layer contains hyphae that are 3–6&nbsp;μm in diameter.<ref name=Baseia2002/>

===Edibility===
[[File:เห็ดเผาะ หรือ เห็ดถอบ.jpg|thumb|The cooked fungus is relatively popular in [[Northern Thailand]] ''(pictured)'']]
North American sources list ''A.&nbsp;hygrometricus'' as inedible,<ref name="Miller2006" /> in some cases because of its toughness.<ref name=Phillips1991/><ref name="urlCalifornia Fungi: Astraeus hygrometricus"/><ref name=Smith1975/> However, they are regularly consumed in Nepal<ref name=Christensen2008/> and South [[Bengal]], where "local people consume them as delicious food".<ref name=Maiti&Chandra2008/> They are collected from the wild and sold in the markets of India.<ref name=Maiti&Bhutia2008/><ref name=Harsh1996/> ''A. hygrometricus'' is also eaten in [[Japan]], being especially popular in the [[Tōhoku region]] as a seasonal summer delicacy. The skin is washed and cooked with rice or deep fried.<ref>{{Cite book |last=Ushijima |first=Shuji |title=牛島秀爾『道端から奥山まで採って食べて楽しむ菌活 きのこ図鑑』 |date=November 1, 2021 |publisher=Tsuribitosha |year=2021 |isbn=978-4-86447-382-8 |location=Japan |pages=82 |trans-title=Enjoy Fungal Activities with Mushrooms: Picking and Eating from Roadsides to Deep Mountains}}</ref>

A study of a closely related southeast Asian ''Astraeus'' species concluded that the fungus contained an abundance of [[volatility (chemistry)|volatile]] eight-carbon compounds (including [[1-octanol]], [[1-octen-3-ol]], and [[1-octen-3-one]]) that imparted a "mushroom-like, earthy, and pungent odor that was evident as an oily and moss-like smell upon opening the caps". The study's authors further noted that the fruit bodies after cooking have a "roasted, [[Maillard reaction|maillard]], herbal, and oily flavor". Volatile compounds detected after cooking the mushroom samples included [[furfural]], [[benzaldehyde]], [[cyclohexenone]], and [[furan]]yl compounds.<ref name=Kakumyan2009/> The regional differences in opinions on edibility are from sources published before it was known that North American and Asian versions of ''A.&nbsp;hygrometricus'' were not always the same; in some cases Asian specimens have been identified as new species, such as ''A.&nbsp;asiaticus'' and ''A.&nbsp;odoratus''.<ref name=Phosri2004/><ref name=Phosri2007/>

==Similar species==
[[File:Astraeus pteridis 70869.jpg|thumb|right|''Astraeus pteridis'' is similar in appearance, but larger; it is found in North America and the [[Canary Islands]].]]
Although ''A.&nbsp;hygrometricus'' bears a superficial resemblance to members of the "true earthstars" ''Geastrum'', it may be readily differentiated from most by the hygroscopic nature of its rays. Hygroscopic earthstars include ''[[Geastrum arenarium|G.&nbsp;arenarium]]'', ''[[Geastrum corollinum|G.&nbsp;corollinum]]'', ''[[Geastrum floriforme|G.&nbsp;floriforme]]'', ''[[Geastrum recolligens|G.&nbsp;recolligens]]'', and ''[[Geastrum kotlabae|G.&nbsp;kotlabae]]''.<ref name=Arora1986/> Unlike ''Geastrum'', the young fruit bodies of ''A.&nbsp;hygrometricus'' do not have a columella (sterile tissue in the gleba, at the base of the spore sac).<ref name=Metzler1992/> ''Geastrum'' tends to have its spore sac opening surrounded by a [[peristome]] or a disc, in contrast with the single lacerate slit of ''A.&nbsp;hygrometricus''. There are also several microscopic differences: in ''A.&nbsp;hygrometricus'', the [[basidia]] are not arranged in parallel columns, the spores are larger, and the threads of the capillitia are branched and continuous with the hyphae of the peridium.<ref name=Coker1928/><ref name=Orr1979/> Despite these differences, older specimens can be difficult to distinguish from ''Geastrum'' in the field.<ref name=McKnight1987/> One species of ''Geastrum'', ''[[Geastrum mammosum|G.&nbsp;mammosum]]'', does have thick and brittle rays that are moderately hygroscopic, and could be confused with ''A.&nbsp;hygrometricus''; however, its spores are smaller than ''A.&nbsp;hygrometricus'', typically about 4&nbsp;μm in diameter.<ref name=Healy2008/>

''[[Astraeus pteridis]]'' is larger, {{convert|5|to|15|cm|in|abbr=on|round=0.5}} or more when expanded, and often has a more pronounced areolate pattern on the inner surface of the rays.<ref name=Arora1986/> It is found in North America and the [[Canary Islands]].<ref name=Phosri2007/> ''[[Astraeus asiaticus|A.&nbsp;asiaticus]]'' and ''[[Astraeus odoratus|A.&nbsp;odoratus]]'' are two similar species known from throughout Asia and [[Southeast Asia]], respectively.<ref name=Phosri2007/> ''A.&nbsp;odoratus'' is distinguished from ''A.&nbsp;hygrometricus'' by a smooth outer mycelial layer with few adhering soil particles, 3–9 broad rays, and a fresh odor similar to moist soil. The spore ornamentation of ''A.&nbsp;odoratus'' is also distinct from ''A.&nbsp;hygrometricus'', with longer and narrower spines that often joined.<ref name=Phosri2004/> ''A.&nbsp;asiaticus'' has an outer peridial surface covered with small granules, and a gleba that is purplish-chestnut in color, compared to the smooth peridial surface and brownish gleba of ''A.&nbsp;hygrometricus''. The upper limit of the spore size of ''A.&nbsp;asiaticus'' is larger than that of its more common relative, ranging from 8.75 to 15.2&nbsp;μm.<ref name=Phosri2007/> ''[[Astraeus koreanus|A.&nbsp;koreanus]]'' (sometimes named as the variety ''A.&nbsp;hygrometricus'' var. ''koreanus''; see Taxonomy) differs from the more common form in its smaller size, paler fruit body, and greater number of rays; microscopically, it has smaller spores (between 6.8 and 9&nbsp;μm in diameter), and the spines on the spores differ in length and morphology.<ref name=Phosri2004/> It is known from Korea and Japan.<ref name=Fangfuk2010/>

==Habitat, distribution, and ecology==

''Astraeus hygrometricus'' is an [[mycorrhizal|ectomycorrhizal]] fungus and grows in association with a broad range of tree species.<ref name=Harley1997/> The [[mutualism (biology)|mutualistic]] association between tree roots and the mycelium of the fungus helps the trees extract nutrients (particularly [[phosphorus]]) from the earth; in exchange, the fungus receives [[carbohydrate]]s from [[photosynthesis]].<ref name=Maiti&Chandra2008/> In North America, associations with [[oak]] and [[pine]] are usual,<ref name=Roody2003/> while in India, it has been noted to grow commonly with [[chir pine]] (''Pinus roxburghii'') and [[Shorea robusta|sal]] (''Shorea robusta'').<ref name=Maiti&Chandra2008/> The false earthstar is found on the ground in open fields, often scattered or in groups, especially in nutrient-poor, sandy or [[loam]]y soils.<ref name=Orr1979/><ref name=Ellis1990/><ref name=Pegler1995/> It has also been reported to grow on rocks, preferring acid [[substrate (biology)|substrates]] like [[slate]] and [[granite]], while avoiding substrates rich in [[lime (material)|lime]].<ref name=Mishra2005/> In Nepal, fruit bodies have been collected at elevations of {{convert|3000|m|abbr=on}}.<ref name=Browne1955/> Fruit bodies typically appear in autumn, although the dry fruit bodies are persistent and may last up to several years.<ref name=Healy2008/> ''[[Gelatinipulvinella astraeicola]]'' is a [[Leotiaceae|leotiaceous]] fungus with minute, gelatinous, pulvinate (cushion-shaped) [[apothecia]], known to grow only on the inner surface of the rays of dead ''Astraeus'' species, including ''A.&nbsp;hygrometricus''.<ref name=Hosoya1995/>

The genus has a [[cosmopolitan distribution]] except for [[climate of the Arctic|arctic]], [[alpine climate|alpine]] and cold [[temperate]] regions;<ref name=Pegler1995/> it is common in temperate and [[tropical]] regions of the world.<ref name=Phosri2007/> It has been collected in Africa, Asia, Australia, Europe, North America,<ref name=Petcharat2003/> and South America.<ref name=Nouhra1998/>

==Bioactive compounds==
[[File:Astrahygrols.svg|thumb|right|Backbone chemical structure upon which the unique [[triterpene]]s astrahygrol (R1=OH, R2=H), 3-''epi''-astrahygrol (R1=H, R2=OH), and astrahygrone (R1=R2=O) are formed]]
Mushroom [[polysaccharide]]s from a number of species have attracted research interest for their [[immunomodulatory]] and [[antitumor]] properties.<ref name=Moradali2007/> Extracts from ''A.&nbsp;hygrometricus'' containing the polysaccharide named AE2 were found to inhibit the growth of several [[cell culture|tumor cell lines]] in laboratory tests,<ref name=Mallick2010/><ref name=Mallick2010b/>  and stimulated the growth of [[splenocyte]]s, [[thymocyte]]s, and [[bone marrow]] cells from mice. The extract also stimulated mouse cells associated with the [[immune system]]; specifically, it enhanced the activity of mouse [[natural killer cell]]s, stimulated [[macrophage]]s to produce [[nitric oxide]], and enhanced production of [[cytokine]]s.<ref name=Maiti&Bhutia2008/><ref name=Pramanik1997/><ref name=Pramanik2000/><ref name=Chakraborty2004/> The activation of macrophages by AE2 might be mediated by a [[mitogen-activated protein kinase]] pathway of [[signal transduction]].<ref name=Mallick2009/><ref name=Mallick2011/> AE2 is made of the simple sugars [[mannose]], [[glucose]], and [[fucose]] in a 1:2:1 ratio.<ref name=Maiti&Chandra2008/>

In addition to the previously known [[steroid]] compounds ergosta-7,22-diene-3-ol acetate and ergosta-4,6,8-(14),22-tetraene-3-one, three unique triterpenes—[[derivative (chemistry)|derivatives]] of 3-hydroxy-[[lanostane]]—have been isolated from fruit bodies of ''A.&nbsp;hygrometricus''. The compounds, named astrahygrol, 3-''epi''-astrahygrol, and astrahygrone (3-oxo-25''S''-lanost-8-eno-26,22-lactone), have δ-[[lactone]] (a six-membered ring) in the [[side chain]]—a chemical feature previously unknown in the [[basidiomycetes]].<ref name=Takaishi1987/><ref name=Hill1991/> A previously unknown [[steryl ester]] (3β, 5α-dihydroxy-(22''E'', 24''R'')-ergosta-7,22-dien-6α-yl palmitate) has been isolated from mycelia grown in [[liquid culture]]. The compound has a polyhydroxylated [[ergostane]]-type nucleus.<ref name=Shao2007/>

Ethanol extracts of the fruit body are high in [[antioxidant]] activity, and have been shown in laboratory tests to have [[anti-inflammatory]] activity comparable to the drug [[diclofenac]].<ref name=Biswas2010/> Studies with [[mouse model]]s have also demonstrated hepatoprotective (liver-protecting) ability, possibly by restoring diminished levels of the antioxidant enzymes [[superoxide dismutase]] and [[catalase]] caused by experimental exposure to the liver-damaging chemical [[carbon tetrachloride]].<ref name=Biswas2011/>

==Traditional beliefs==

This earthstar has been used in [[traditional Chinese medicine]] as a [[hemostatic]] agent; the spore dust is applied externally to stop wound bleeding and reduce [[chilblain]]s.<ref name=Hobbs1995/> Two [[India]]n forest tribes, the [[Baiga (tribe)|Baiga]] and the [[Bharia people|Bharia]] of [[Madhya Pradesh]], have been reported to use the fruit bodies medicinally. The spore mass is blended with [[mustard seed]] oil and used as a [[salve]] against burns.<ref name=Rai1993/> The [[Blackfoot]] of North America called the fungus "fallen stars", considering them to be stars fallen to the earth during supernatural events.<ref name=Burk1983/>

==See also==
{{portal|Fungi}}
*[[Medicinal mushrooms]]

==References==
{{Reflist|colwidth=30em|refs=

<ref name=Alexopoulos1996>{{cite book |vauthors=Alexopoulos CJ, Mims CW, Blackwell M |title=Introductory Mycology |year=1996 |page=551 |publisher=John Wiley and Sons |location=New York, New York |isbn=0-471-52229-5}}</ref>

<ref name=Arora1986>{{cite book |vauthors=Arora D |title=Mushrooms Demystified: a Comprehensive Guide to the Fleshy Fungi |publisher=Ten Speed Press |location=Berkeley, California |year=1986 |page=[https://archive.org/details/mushroomsdemysti00aror_0/page/706 706] |isbn=0-89815-169-4 |url-access=registration |url=https://archive.org/details/mushroomsdemysti00aror_0/page/706 }}</ref>

<ref name=Baseia2002>{{cite journal | vauthors = Baseia IG, de Galvão TC |title=Some interesting Gasteromycetes (Basidiomycota) in dry areas from northeastern Brazil |journal=Acta Botanica Brasilica |year=2002 |volume=16 |issue=1 |pages=1–8 |doi=10.1590/S0102-33062002000100002|doi-access=free }}</ref>

<ref name=Biswas2010>{{cite journal | vauthors = Biswas G, Sarkar S, Acharya K |title=Free radical scavenging and anti-inflammatory activities of the extracts of ''Astraeus hygrometricus'' (Pers.) Morg |journal=Latin American Journal of Pharmacy |year=2010 |volume=29 |issue=4 |pages=549–53| url=http://sedici.unlp.edu.ar/handle/10915/7946}}</ref>

<ref name=Biswas2011>{{cite journal|vauthors=Biswas G, Sarkar S, Acharya K |title=Hepatoprotective activity of the ethanolic extract of ''Astraeus hygrometricus'' (Pers.) Morg |journal=Digest Journal of Nanomaterials and Biostructures |year=2011 |volume=6 |issue=2 |pages=637–41 |url=http://www.chalcogen.infim.ro/637_Biswas.pdf |url-status=dead |archive-url=https://web.archive.org/web/20120331115054/http://www.chalcogen.infim.ro/637_Biswas.pdf |archive-date=2012-03-31 }}</ref>

<ref name=Browne1955>{{cite journal |vauthors=Balfour-Browne FL |title=Some Himalayan fungi |journal=Bulletin of the British Museum (Natural History) |year=1955 |volume=1 |issue=7 |pages=187–218 (see p. 201) |url=https://www.biodiversitylibrary.org/page/30751282#page/229/mode/1up}}</ref>

<ref name=Burk1983>{{cite journal |vauthors=Burk W |title=Puffball usages among North American Indians |journal=Journal of Ethnobiology |year=1983 |volume=3 |issue=1 |pages=55–62 |url=http://ethnobiology.org/sites/default/files/pdfs/JoE/3-1/Burk1983.pdf}}</ref>

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<ref name=Maiti&Bhutia2008>{{cite journal |vauthors=Maiti S, Bhutia SK, Mallick SK, Kumar A, Khadgi N, Maiti TK |year=2008 |title=Antiproliferative and immunostimulatory protein fraction from edible mushrooms |journal=Environmental Toxicology and Pharmacology |volume=26 |issue=2 |pages=187–91 |doi=10.1016/j.etap.2008.03.009 |pmid=21783909}}</ref>

<ref name=Maiti&Chandra2008>{{cite journal |vauthors=Maiti D, Chandra K, Mondal S, Ojha AK, Das D, Roy SK, Ghosh K, Chakraborty I, Islam SS |year=2008 |title=Isolation and characterization of a heteroglycan from the fruits of ''Astraeus hygrometricus'' |journal=Carbohydrate Research |volume=343 |issue=4 |pages=817–24 |doi=10.1016/j.carres.2007.12.003 |pmid=18206864}}</ref>

<ref name=Mallick2009>{{cite journal |vauthors=Mallick SK, Bhutia SK, Maiti TK |title=Macrophage stimulation by polysaccharides isolated from barometer earthstar mushroom, ''Astraeus hygrometricus'' (Pers.) Morgan (Gasteromycetideae) |journal=International Journal of Medicinal Mushrooms |year=2009 |volume=11 |issue=3 |pages=237–48 |doi=10.1615/IntJMedMushr.v11.i3.30}}</ref>

<ref name=Mallick2010>{{cite journal |vauthors= Mallick SK, Maiti S, Bhutia SK, Maiti TK |title=Antitumor properties of a heteroglucan isolated from ''Astraeus hygrometricus'' on Dalton's lymphoma bearing mouse |journal=[[Food and Chemical Toxicology]] |year=2010 |volume=48 |issue=8–9 |pages=2115–21 |doi=10.1016/j.fct.2010.05.013 |pmid=20472019}}</ref>

<ref name=Mallick2010b>{{cite journal |vauthors=Mallick SK, Maiti S, Bhutia SK, Maiti TK |title=Immunostimulatory properties of a polysaccharide isolated from ''Astraeus hygrometricus'' |journal=Journal of Medicinal Food |year=2010 |volume=13 |issue=3 |pages=665–72 |pmid=20521989 |doi=10.1089/jmf.2009.1300}}</ref>

<ref name=Mallick2011>{{cite journal |vauthors=Mallick SK, Maiti S, Bhutia SK, Maiti TK |title=Activation of RAW 264.7 cells by ''Astraeus hygrometricus''-derived heteroglucan through MAP kinase pathway |journal=Cell Biology International |year=2011 |volume=35 |issue=6 |pages=617–21 |pmid=21143204 |doi=10.1042/CBI20100199|s2cid=36705550 }}</ref>

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<ref name=Shao2007>{{cite journal |vauthors=Shao HJ, Fang LZ, Yang WQ, Wang F, Liu JK |title=A new steryl ester from the culture mycelia of the Basidiomycete ''Astraeus hygrometricus'' (Astraceae) |journal=Acta Metallurgica Sinica|year=2007 |volume=29 |issue=3 |pages=371–4 |issn=0412-1961}}</ref>

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<ref name=Takaishi1987>{{cite journal |vauthors=Takaishi Y, Murakami Y, Ohashi T, Nakano K, Murakami K, Tomimatsu T |title=Three triterpenes from ''Astraeus hygrometricus'' |journal=Phytochemistry |year=1987 |volume=26 |issue=8 |pages=2341–4 |doi=10.1016/S0031-9422(00)84715-9|bibcode=1987PChem..26.2341T }}</ref>

<ref name="urlCalifornia Fungi: Astraeus hygrometricus">{{cite web |vauthors=Wood M, Stevens F |url=http://www.mykoweb.com/CAF/species/Astraeus_hygrometricus.html |title=''Astraeus hygrometricus'' |publisher=MykoWeb. California Fungi |access-date=2011-08-29}}</ref>

<ref name="urlFotM">{{cite web |url=http://botit.botany.wisc.edu/toms_fungi/dec2003.html |title=''Astraeus hygrometricus'', an earth star. Tom Volk's Fungus of the Month for December 2003 |author=Volk T. |publisher=University of Wisconsin-La Crosse, Department of Biology |year=2003 |access-date=2011-08-24}}</ref>

<ref name="urlMycoBank: Astraeus hygrometricus">{{cite web |title=''Astraeus hygrometricus'' (Pers.) Morgan 1889 |url=http://www.mycobank.org/MycoTaxo.aspx?Link=T&Rec=122650 |publisher=[[MycoBank]]. International Mycological Association |access-date=2011-08-24}}</ref>

}}

==External links==
{{Commons category|Astraeus hygrometricus}}
{{Wikispecies|Astraeus hygrometricus}}

{{Taxonbar|from=Q980655}}
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[[Category:Boletales]]
[[Category:Fungi of Asia]]
[[Category:Fungi of Australia]]
[[Category:Fungi of Europe]]
[[Category:Fungi of North America]]
[[Category:Fungi of Colombia]]
[[Category:Inedible fungi]]
[[Category:Medicinal fungi]]
[[Category:Plant morphology]]
[[Category:Fungi described in 1801]]
[[Category:Taxa named by Christiaan Hendrik Persoon]]
[[Category:Fungus species]]