Myriostoma

Myriostoma
Scientific classification
Kingdom:	Fungi
Phylum:	Basidiomycota
Class:	Agaricomycetes
Subclass:	Phallomycetidae
Order:	Geastrales
Family:	Geastraceae
Genus:	Myriostoma Desv.
Type species
Myriostoma coliforme (Dicks.) Corda
Synonyms[1]
Species Bovistoides simplex Lloyd Geastrum coliforme (Dicks.) Pers. Geastrum columnatum Lév. Lycoperdon coliforme Dicks. Myriostoma anglicum Desv. Myriostoma coliforme (Dicks.) Corda Polystoma coliforme (Dicks.) Gray Genus Bovistoides Lloyd 1919 Polystoma Gray 1821

Myriostoma is a genus of fungus in the family Geastraceae. The genus is monotypic, containing the single species Myriostoma coliforme. It is an earthstar, so named because outer wall of the spore-bearing body splits open into the shape of a star. The inedible fungus has a cosmopolitan distribution, and has been found in Africa, Asia, North and South America, and Europe, where it grows on humus-rich forest or woodland floor, especially on well-drained and sandy soils. This somewhat rare fungus was included in 2004 in a list of 33 species proposed for protection under the Bern Convention by the European Council for Conservation of Fungi, and included on the Red Lists of 12 European countries.

The fruit body, initially shaped like a puffball, is encased within an outer covering that splits open from the top to form rays. These rays curve down to expose an inner papery spore case, the endoperidium, which contains the fertile gleba. The fungus is unique among the earthstars in having a spore case that is supported by multiple stalks, as is perforated by several small holes suggestive of its common names salt-shaker earthstar and pepperpot. It is the largest of the earthstar fungi, and reaches diameters of up to 12 cm (4.7 in). Its spores have elongated warts that creates a ridge-like pattern on the surface described as being reticulate.

Taxonomy, phylogeny, and naming

Illustration from James Sowerby's Coloured Figures of English Fungi or Mushrooms (1803)

The species was first mentioned in the scientific literature by Samuel Doody in the second edition of John Ray's Synopsis methodica Stirpium Brittanicorum in 1696.^[2] Ray described the mushroom like so: "fungus pulverulentus coli instar perforatus, cum volva stellata", and went on to explain that he has found it in 1695 in Kent.^[3] It was first described scientifically as a new species from England in 1776 by James Dickson, who named it Lycoperdon coliforme. He found it growing in roadside banks and hedgerows among nettles in Suffolk and Norfolk.^[4] Christian Hendrik Persoon called it Geastrum coliforme in 1801,^[5] and Gray called it Polystoma coliforme in 1821.^[6] In North America, the fungus was reported from Colorado by Charles Horton Peck, collected in Florida by Lucien Underwood in 1891, and had notes published about it by Andrew Price Morgan in American Naturalist, April 1892.^[7] Curtis Gates Lloyd named it Bovistoides simplex in 1919,^[8] but in 1942, William Henry Long examined the specimen and concluded that it was a weathered spore sac of M. coliforme that had become detached from the outer star-shaped exoperidium.^[9] This conclusion was confirmed in a later study of the type material.^[10] The genus Myriostoma was named and described by Nicaise Auguste Desvaux published in the Journal de Botanique, Rédigé par une Société di Botanistes in 1809.^[11]

Various Geastrum & Radigera spp. Myriostoma Pyrenogaster spp. Sclerogaster xerophilus

Phylogeny and relationships of Myriostoma and other Geastrales based on ribosomal DNA sequences.[12]

Myriostoma had been classified in the Geastraceae family until British mycologist Donald Dring (1973) placed it in the Astraceae (Sclerodermatales) based on the presence of the trabeculae (stout columns which extend from the peridium to the central core of the fruit body) in the gleba, and the absence of a true hymenium.^[13] In his 1989 monograph, Sunhede placed in again in the Geastraceae.^[14] Phylogenetic analysis has shown that Myriostoma and Geastrum form a sister group to the Phallales, but are not closely related to the Lycoperdales.^[15]

Other taxa formerly classified as Myriostoma include Myriostoma anglicum Desv. (1809) (the type species, and the variety Myriostoma coliforme var. coliforme (Dicks.) Corda (1842) and Myriostoma coliforme var. capillisporum V.J. Staněk (1958). These are all considered synonymous with Myriostoma coliforme,^[1] given its current name by August Carl Joseph Corda in 1842.^[16] M. coliforme is the sole species in Myriostoma, making the genus monotypic.^[17] Because the original type material has been lost, in 1989 Sunhede suggested that Dickson's illustration in his 1776 publication (tab. III: 4a & b) be selected as the lectotype.^[14]

The specific epithet is derived from the Latin words colum, "strainer", and forma, "shape". Berkeley's vernacular name "Cullenden puff-ball" refers to a colander;^[18] Gray called it the "sievelike pill-box".^[6] The generic name is from the Greek words μνριος "countless" and στομα "mouth".^[19] It is commonly known as the "salt-and-pepper shaker earthstar"^[20] or the "pepperpot".^[21]

Description

Fruit body

The fruit bodies start their development underground or buried in leaf debris, and have a strand of mycelium at the base. As they mature, the exoperidium (the outer tissue layer of the peridium) curves backwards and splits open into rays. This movement pushes the fruit body above the surface of the substrate. There are 8–14 rays that are unequal in size, with tips that are often rolled inward. Fully opened individuals can reach dimensions of 2–12 cm (0.8–4.7 in) across from ray tip to tip. The rays are made of three distinct layers of tissue. The thick pseudoparenchymatous layer is fleshy and thick when fresh, pale beige but becoming yellow to brown as it matures, and often cracking and peeling off in the process. The exterior mycelial tissue layer, often matted with fine leaf debris or dirt, usually cracks to reveal the middle fibrous layer, which is made of densely packed hyphae that are 1–2.5 μm wide. The base is concave to vaulted, often showing a large umbilical scar where the mycelial strand was attached. The spore sac, or endoperidium, have very short, inconspicuous pedicels, shaped like flattened spheres, 1–5 cm (0.4–2.0 in) in diameter. It is gray-brown in color, and minutely roughened with small subreticulate warts. There are usually one to six evenly dispersed mouths (ostioles, or stomata), mainly on upper half of the spore sac. They are roughly circular and have fringed (fimbriate) margins.^[22][23] The fruit bodies are inedible.^[24]

Like many earthstars, the fungus uses the force of falling raindrops to help disperse the spores; the spores are ejected in little bursts as falling raindrops strike the outer wall of the spore sac. The gleba is brown grayish-brown. It has a "cottony" or "hairy" texture that when compressed, allows the endoperidium to flex quickly, creating a puff of air that is forced out through the ostiole. This generates a cloud of spores that are lifted in the air, facilitating dispersal.^[25] There are several to many columellae (sterile tissue usually in the base of the gleba, and extending up into the gleba), which are usually not evident in the mature gleba, but apparent at the base of the spore sac. The columellae are not connected to the openings at the top of the spore case, but rather, terminate at some distance from them in the gleba. The capillitium (coarse thick-walled cells found in the gleba) are long, slender, free, tapering, unbranched, and 2–5 μm thick, with thick walls. The spores are spherical, nonamyloid, and are ornamented with warts up to 2 μm high. They measure 4–5 μm diameter (without ornamentation), and 5.4–7.0 μm including the warts.^[23]

Similar species

Myriostoma coliforme is the largest earthstar fungus, and the only one that produces numerous openings on the top of its spore sac, and numerous stalks that support the spore sac.^[26] Historically, it was thought that the openings might have been a result of insect action. This was addressed in an early report of the fungus by Woodward (1797):

It has been doubted whether these mouths might not be accidental, and formed by insects after the expansion of the plant. But this (not to mention their regularity, and that each is furrowed by its border of ciliae) is clearly disproved, from the marks of the projections formed by the mouths being seen on the expanded rays, when freshly opened... I have likewise found an abortive plant, in which the seed did not ripen; but which had numerous projecting papillae on the head, where the mouths should have been formed.^[27]

Ecology, habitat and distribution

Myriostoma is a saprobic species.

The fungus grows in groups in well-drained or sandy soil, often in the partial shade of trees.^[22] It is saprobic, deriving nutrients by decomposing organic matter. It can be found in both deciduous and mixed forests, gardens, along hedges and grassy road banks as well as grazed grasslands. In the Northern Hemisphere, it tends to grow on well-drained south-facing slopes, while it prefers similar habitat on south facing slopes in Australia.^[14] In Europe, its major habitat is Riparian mixed forests along the great rivers, dominated by Salix alba and Populis alba galleris.^[21] In Hawaii, it has been collected at elevations above 2,000 m (6,600 ft) where it appears to favor the mamame (Sophora chrysophylla) forest.^[28] The fungus is widespread in Europe, having been found in Czechoslovakia,^[29] Germany,^[30] Italy,^[31] The Netherlands,^[32] Poland,^[33] Portugal,^[34] and Sweden^[35]—its most northerly location; it is generally rare in northern Europe.^[26] It has also been found in the Canary Islands,^[36] Morocco (in the Mamora forest),^[37] and in South Africa.^[14] In South America, the fungus has been collected in the Galapagos Islands,^[38] Argentina,^[39] Brazil,^[40] and Chile.^[41] The North American distribution ranges from Canada to Mexico (Ajos-Bavispe National Forest Reserve).^[42] In the Middle East, it has also been found in Afghanistan^[43] and Iran. It is also in Australia (where it may be an introduced species)^[23] China,^[44] and India.^[14]

Myriostoma coliforme is listed as one of the 33 threatened fungi in Europe, and is listed on 12 Regional Red Lists.^[21] In the United Kingdom, it was considered extinct in mainland Britain due to lack of collections since 1880,^[45] but it was found in Suffolk in 2006 near Ipswich, one of its original localities.^[26] It is also found in the Channel Islands.^[24]

References

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3. ^ Ray J. (1696) (in Latin, English). Synopsis Methodica Stirpium Britannicarum. London: Impensis Gulielmi & Joannis Innys. p. 28. http://books.google.ca/books?id=GUg-AAAAcAAJ&lpg=PA290&ots=LW8Xj5efxN&dq=Synopsis%20methodica%20Stirpium%20Britannicarum&pg=PA28#v=onepage&q=perforatus&f=false. Retrieved 2010-09-29. 
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26. ^ ^{a b c} Spooner B, Döring H, Aguirre-Hudson B.. "Plants & Fungi: Myriostoma coliforme (pepperpot earthstar)". Species profile from Kew. Kew Botanical Gardens. http://www.kew.org/plants-fungi/Myriostoma-coliforme.htm. Retrieved 2010-09-29. 
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40. ^ Baseia IG. (2002). "Some interesting gasteromycetes (Basidiomycota) in dry areas from northeastern Brazil". Acta Botanica Brasilica 16 (1). doi:10.1590/S0102-33062002000100002. http://www.scielo.br/scielo.php?pid=S0102-33062002000100002&script=sci_arttext. 
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External links

• Myriostoma in Index Fungorum.
• Lectotype illustration from Tab. III of James Dickson's 1776 Fasciculus plantarum cryptogamicarum Britanniae