Geastrum saccatum

Geastrum saccatum

Mycological characteristics
Geastrum saccatum Mycological characteristics
	Glebal hymenium
	No distinct cap
	Hymenium attachment is not applicable
	Lacks a stipe
	Spore print is brown
	Ecology is saprotrophic
	Edibility is inedible

Geastrum saccatum
Scientific classification
Domain:	Eukaryota
Kingdom:	Fungi
Division:	Basidiomycota
Class:	Agaricomycetes
Order:	Geastrales
Family:	Geastraceae
Genus:	Geastrum
Species:	G. saccatum
Binomial name
	Geastrum saccatum; Fr. (1829)

Last updated October 15, 2024

Geastrum saccatum, commonly known as the sessile earthstar^[1] or rounded earthstar,^[2] or star of the land,^[3] is a species of mushroom belonging to the genus Geastrum . The opening of the outer layer of the fruiting body in the characteristic star shape is thought to be due to a buildup of calcium oxalate crystals immediately prior to dehiscence. G. saccatum is distinguished from other earthstars by the distinct circular ridge or depression surrounding the central pore.

Description

The immature fruiting body is 0.6 to 2.5 centimetres (1⁄4 to 1 in) in diameter and 0.8 to 1.5 cm (3⁄8 to 5⁄8 in) tall. Initially, the fruiting body is egg-shaped—similar in appearance to puffballs—and has strands of mycelia (rhizomorphs) at the base that attach it to the growing surface. The 'skin,' or peridium, is composed of two separate layers: the outer layer (exoperidium), which is a golden tan to yellowish-brown color, separates away from the inner basidiocarp and splits into five to eight rays^[4] that curve backward (recurve) to the base.

The mushroom is 2 to 5 cm (3⁄4 to 2 in) in diameter after the rays have expanded. Unlike some other members of the genus Geastrum (such as G. fornicatum ) the arms do not push the basidiocarp off the ground; rather, it lies flat. The inner spore-bearing basidiocarp is 0.5 to 2 cm (1⁄4 to 3⁄4 in) broad, and has a central pore surrounded by a circular dull-brown apical disc; the disc is distinctly ridged or depressed.^[2] The inside of the interior sphere is white when young, but matures into a mass of brown, powdery spores mixed with thick-walled fibres known as capillitium.^[5] The flesh is bitter.^{[ citation needed ]}

A fresh specimen of G. saccatum Geastrum.Saccatum.002.jpg — A fresh specimen of *G. saccatum*

Spores

The spores are rounded, with warts, and have dimensions of 3.5–4.5 μm.^[5]

Mechanism of dehiscence

A study has shown that the formation of calcium oxalate crystals on the hyphae that form the endoperidial layer of the basidiocarp is responsible for the characteristic opening (dehiscence) of the outer peridial layers.^[6] Calcium oxalate is a common compound found in many fungi,^[7] including the earthstars.^[8] Curtis Gates Lloyd was the first to note the presence of these crystals on the endoperidium of Geaster calceus (now known as Geastrum minimum).^[9] The formation of calcium oxalate crystals stretches the layers of the outer walls, pushing the inner and outer layers of the peridium apart.^[6]

Similar species

The related species Geastrum fimbriatum does not have an apical disc,^[10] and its pores are slightly smaller. G. saccatum may be distinguished from G. indicum by the absence of loose tissue forming a collar around the base of the endoperidium. Other similar species include G. fornicatum and G. triplex .^[10] Astraeus earthstars usually have less orderly rays.^[11]

Habitat and distribution

Geastrum saccatum is saprobic, and grows scattered or clustered together in leaf litter of humus, usually in late summer and fall. It has a cosmopolitan distribution, and is well adapted to tropical regions.^[3] It is common in Hawaiian dry forests.^[12]

The species has been collected in North America (Canada, the United States and Mexico), Central America (the Congo and Panama), South America (Argentina, Uruguay, and Brazil), Cuba, Africa (Tanzania, West Africa, and South Africa), Asia (China and India), and Tobago.^[13] In North America, it is found September–December on the west coast and July–October elsewhere.^[11]

Potential uses

The species is inedible.^[14]

Bioactive compounds

A β-glucan–protein complex extracted from G. saccatum was isolated and analysed and shown to have antiinflammatory, antioxidant, and cytotoxic activities. It is suggested that the mechanism for the antiinflammatory activity is due to inhibition of the enzymes nitric oxide synthase and cyclooxygenase.^[3]

In culture

In Brazil, its common name translates to "star of the land".^[3]

Related Research Articles

<span class="mw-page-title-main">Puffball</span> Fungus

Puffballs are a type of fungus featuring a ball-shaped fruit body that bursts on contact or impact, releasing a cloud of dust-like spores into the surrounding area. Puffballs belong to the division Basidiomycota and encompass several genera, including Calvatia, Calbovista and Lycoperdon. The puffballs were previously treated as a taxonomic group called the Gasteromycetes or Gasteromycetidae, but they are now known to be a polyphyletic assemblage.

Geastrum is a genus of puffball-like mushrooms in the family Geastraceae. Many species are commonly known as earthstars.

Calostoma is a genus of 29 species of gasteroid fungi in the suborder Sclerodermatineae. Like other gasteroid fungi, Calostoma do not have the spore discharge mechanism associated with typical gilled fungi (ballistospory), and instead have enclosed spore-bearing structures. Resembling round puffballs with raised, brightly colored spore openings (ostioles), elevated on a thick, gelatinous stalks, species have been collected in regions of deciduous, temperate, tropical or subtropical forests. Their distribution includes eastern North America, Central America, Asia, and Australasia. The common name given to some species, "prettymouth", alludes to the brightly colored raised openings (ostioles) that may somewhat resemble lips. Other common names include "hotlips" and "puffball in aspic".

Sphaerobolus is a genus of fungi in the family Geastraceae. Commonly known as the "shotgun fungus", "artillery fungus" or "cannonball fungus", species discharge their spores with explosive force. Discharged spore sacs are sticky and have a tendency to strongly adhere to whatever surface they encounter, making them a nuisance to homeowners, pressure washing contractors, landscape mulch producers and insurance companies.

Geastrum fornicatum, commonly known as the acrobatic earthstar or the arched earthstar, is an inedible species of mushroom in the family Geastraceae. Like other earthstar mushrooms, the thick outer skin splits open at maturity, exposing the spore sac to the elements. It is found in the southwest United States.

The peridium is the protective layer that encloses a mass of spores in fungi. This outer covering is a distinctive feature of gasteroid fungi.

Myriostoma is a fungal genus in the family Geastraceae. Basidiocarps resemble earthstars, but the spore sac is supported by multiple columns and has multiple ostioles instead of a single, apical ostiole. Until 2017, the genus was thought to be monotypic with a single, widespread species, Myriostoma coliforme. Recent research has, however, shown that at least six species occur worldwide.

Geastrum berkeleyi, or Berkeley's earthstar, is an inedible species of mushroom belonging to the genus Geastrum, or earthstar fungi. It can be distinguished from other Geastrum species by the flat bipyramidal shape of the calcium oxalate crystals found on its endoperidium.

Geastrum fimbriatum, commonly known as the fringed earthstar or the sessile earthstar, is an inedible species of mushroom belonging to the genus Geastrum, or earthstar fungi.

Geastrum pectinatum is an inedible species of mushroom belonging to the earthstar family of fungi. Although young specimens are spherical, fruit body development involves the outer layer of tissue splitting open like a star into 7 to 10 pointed rays that eventually bend back to point downward, revealing a small – 1 to 2.5 cm broad – spore sac. The spore sac is supported by a small radially wrinkled stalk. There is a distinct conical opening (peristome) at the top of the spore sac that is up to 8 mm long. It is commonly known as the beaked earthstar or the beret earthstar, in reference to the shape of the spore sac and its prominent, protruding peristome. The mass of spores and surrounding cells within the sac, the gleba, is dark-brown, and becomes powdery in mature specimens. Spores are spherical, measuring 4 to 6 micrometers in diameter, with warts on their surfaces.

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 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 ectomycorrhizal species that grows in association with various trees, especially in sandy soils. A. 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. Its common names 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 spores mature. The spores are reddish-brown and roughly spherical with minute warts, measuring 7.5–11 micrometers in diameter.

Astraeus is a genus of fungi in the family Diplocystaceae. The genus, which has a cosmopolitan distribution, contains nine species of earthstar mushroom. They are distinguished by the outer layer of flesh (exoperidium) that at maturity splits open in a star-shape manner to reveal a round spore sac. Additionally, they have a strongly hygroscopic character—the rays will open when moist, but when hot and dry will close to protect the spore sac. Species of Astraeus grow on the ground in ectomycorrhizal associations with trees and shrubs. Despite their similar appearance to the Geastrum earthstars, the species of Astraeus are not closely related.

Geastrum triplex is a fungus found in the detritus and leaf litter of hardwood forests around the world. It is commonly known as the collared earthstar, the saucered earthstar, or the triple earthstar—and less commonly by the alternative species name Geastrum indicum. It is the largest member of the genus Geastrum and expanded mature specimens can reach a tip-to-tip length of up to 12 centimeters.

<span class="mw-page-title-main">Gasteroid fungi</span> Group of fungi

The gasteroid fungi are a group of fungi in the Basidiomycota. Species were formerly placed in the obsolete class Gasteromycetes Fr., or the equally obsolete order Gasteromycetales Rea, because they produce spores inside their basidiocarps rather than on an outer surface. However, the class is polyphyletic, as such species—which include puffballs, earthstars, stinkhorns, and false truffles—are not closely related to each other. Because they are often studied as a group, it has been convenient to retain the informal (non-taxonomic) name of "gasteroid fungi".

Geastrum jurei is a species of fungus in the Geastrales, or earthstar fungi. It is known only from Algarrobo, in the Valparaíso province of Chile. It is a fornicate species of earthstar, meaning that the tips of the rays press down so as to raise the spherical spore sac into the air.

Geastrum quadrifidum, commonly known as the rayed earthstar or four-footed earthstar, is an inedible species of mushroom belonging to the genus Geastrum, or earthstar fungi. First described scientifically by Christian Hendrik Persoon in 1794, G. quadrifidum is a cosmopolitan—but not common—species of Europe, the Americas, Africa, Asia, and Australasia. The fungus is a saprobe, feeding off decomposing organic matter present in the soil and litter of coniferous forests.

Geastrum welwitschii is a species of fungus in the earthstar family. First collected from Spain in the mid-19th century, the fungus is distributed in Europe, North America, and Bermuda.

Myriostoma coliforme, commonly known as the saltshaker earthstar or pepper pot, is a fungal species in the family Geastraceae. Basidiocarps resemble earthstars, but the spore sac is supported by multiple columns and has multiple ostioles instead of a single, apical ostiole. It has also been called "salt-shaker earthstar". The fungus has a north temperate distribution, but was formerly thought to be more widespread due to confusion with related Myriostoma species. Myriostoma coliforme is an uncommon species and appears on the Red Lists of 12 European countries. In 2004 it was one of 33 species proposed for protection under the Bern Convention by the European Council for Conservation of Fungi.

Geastrum minimum, the tiny earthstar, is an inedible species of mushroom belonging to the genus Geastrum. Although rare, it is widespread in Europe, where it occurs in a range of habitats. It is a priority species in the UK, where it has been found in the sand dunes at Holkham National Nature Reserve.

Geastrum britannicum is a fungal species in the family Geastraceae. Its recommended English name is vaulted earthstar. Like other earthstars, the basidiocarps are initially globose. Their thick outer skin splits open at maturity to expose the puffball-like spore sac surrounded by the split rays of the outer skin. In the vaulted earthstar, the rays split apart and form an arch, raising the spore sac upwards.

References

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↑ Phillips, Roger (2010). Mushrooms and Other Fungi of North America. Buffalo, NY: Firefly Books. p. 336. ISBN 978-1-55407-651-2.