Myriostoma coliforme (pepperpot earthstar)
Myriostoma coliforme (Photo: Mila Dobesova)
Considered extinct in UK until recently rediscovered, rare in Europe and red-listed in 12 European countries.
Prefers well-drained base-rich soils, amongst humus and plant litter in hedges, woods and occasionally grazed, grassy areas, possibly mainly in nitrogen-rich sites.
About this species
An extraordinary and distinctive species, unique amongst the earthstars in having a spore sac with multiple stalks as well as multiple pores or stomata, the latter appearing as circular holes. The pepperpot earthstar (Myriostoma coliforme) was described from England as a new species in 1776, where it was found in roadside banks and hedgerows amongst nettles in Suffolk and Norfolk. Thereafter, during the 19th century, it was found in several localities in Kent, Middlesex, and Worcestershire, but by 1880 had disappeared.
Geography and distribution
Widespread; most northerly sites in Sweden, elsewhere in Northern Europe rare, including southern England and Channel Islands, more frequent in southern Europe. Also found in parts of Russia, Afghanistan, Iran, Pakistan, South Africa, India, Hawaii, Brazil, and in Australia where it may have been introduced.
The pepperpot earthstar is one of the basidiomycete fungi, related to the well-known mushrooms and toadstools.
Unlike most of these, but in common with puffballs and stinkhorns, its spores are not forcibly discharged but passively dispersed. As with typical earthstars and many puffballs, spores are released by a bellows mechanism triggered by falling raindrops. The force of the drops hitting the wall of the spore sac pushes out the spores which are then dispersed in the air. It is the only species to have multiple pores or mouths, which inspire the common name as well as the Latin epithet which means ‘like a colander’.
Myriostoma coliforme has fruitbodies which are rounded when young and, as in all earthstars, comprise two main layers. Mature, unopened fruitbodies are mostly 3-8 cm in diameter. At this stage, the outer layer or exoperidium splits into 5-10 or so rays which turn back in a star-like pattern to expose the inner spore-bearing sac or endoperidial body. The exoperidium is 5-6 mm thick, and the rays turn back and arch somewhat under the fruitbody, raising it slightly, as in most earthstars, facilitating spore dispersal. The expanded fruitbody varies in size, but is commonly 5-10 cm diameter.
The spore sac is rounded, usually subglobose, varying mostly from 15-50 mm in diameter., and is attached to the exoperidium by multiple stalks each up to c. 5 mm high and rounded to angular or flattened in cross-section. The spore sac is grey to brown when mature, often shiny with age, and is perforated by numerous irregularly dispersed pores each roughly circular, 1-3 mm diameter, through which the spores are dispersed. It encloses the gleba which, at maturity, as in all earthstars and puffballs, comprises a powdery spore mass. Spores are brown in mass at maturity, and under the microscope globose with distinctive flange and 4-6 μm diam. It fruits mainly in autumn, but the fruitbodies are quite tough and resistant and may be found throughout the year.
Threats and conservation
Myriostoma coliforme is widespread but rather rare throughout most of its range and considered threatened in places. It is known from only a few sites in Sweden, and was considered extinct in Britain until rediscovered in 2006. Still regarded in the UK as critically endangered, it is threatened by habitat disturbance and lack of grazing. The effects of climate change on this species are not known.
The pepperpot earthstar 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 (ECCF), and included on the Red Lists of 12 European countries.
Nothing is yet documented about the uses of this fungus. Earthstars in general, despite their unique form, appear to have little associated folklore, and their uses have been mainly medical. Like other earthstars (Geastrum spp.), Myriostoma may have been used at times as a styptic, the powdery spore mass of these fungi being effective in staunching blood flow, as a painkiller, or to reduce fever. Its unique appearance has also led to its use as a decorative object.
Discovery and rediscovery - the pepperpot earthstar
The pepperpot earthstar was known to the great English naturalist John Ray, who collected it in Kent as early as 1695. In those days, before the advent of the binomial classification system introduced by Linnaeus in 1753, he used for it the descriptive phrase ‘fungus pulverulentus coli instar perforatus, cum volva stellata’. It was described and illustrated by Withering in 1776 in the second volume of his A botanical arrangement of all the vegetables growing naturally in Britain. He used the name Lycoperdon coliforme. The genus Myriostoma was introduced for this species by Desvaux in 1809; it is still the only known species in its genus.
Myriostoma coliforme was last collected in 1880 in Norfolk, and remained unrecorded thereafter until a specimen was discovered in Suffolk in 2006. It seems unlikely that such a distinctive fungus could have remained undetected in Britain for over 120 years, and a reintroduction seems plausible. However, it is interesting that the species was refound close to one of its original localities. The new collection was of an old, weathered specimen found in February 2006 on a sandy bank at the edge of oak woodland near Ipswich.
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Legon, N.W. & Henrici, A. (2005). Checklist of the British and Irish Basidiomycota. Royal Botanic Gardens, Kew.
Rees, B.J., Taeker, F., & Coveny, R.G. (2005). Myriostoma coliforme in Australia. Australasian Mycologist 24: 25 – 28.
Sunhede, S. (1989). Geastraceae (Basidiomycotina). Morphology, Ecology, and Systematics with special emphasis on the North European species. Synopsis Fungorum 1.
Kew Science Editor: Brian Spooner
Kew contributors: Heidi Döring, Begoňa Aguirre-Hudson
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