Astraeus (fungus)
| Astraeus | |
|---|---|
 |
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| Astraeus hygrometricus | |
| Scientific classification | |
| Kingdom: | Fungi |
| Division: | Basidiomycota |
| Class: | Agaricomycetes |
| Order: | Boletales |
| Family: | Diplocystaceae |
| Genus: |
Astraeus Morgan (1885) |
| Type species | |
|
Astraeus hygrometricus (Pers.) Morgan (1889) |
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| Species | |
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A. asiaticus |
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A. asiaticus
A. hygrometricus
A. koreanus
A. morganii
A. odoratus
A. pteridis
A. sirindhorniae
A. smithii
A. telleriae
Astraeus is a genus of fungi in the family Diplocystaceae. The genus, which has a cosmopolitan distribution, contains nine species of earthstar mushrooms. 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.
The mycelium of immature specimens is fibrous, and originates from all parts of the surface. The peridium is roughly spherical, and made of two distinct tissue layers. The outer layer, the exoperidium, is thick, leathery, and initially inseparable from the inner layer (endoperidium). At maturity, the exoperidium bursts open into several pointed "rays". The inner layer of tissue, the endoperidium, is thin, like a membrane. The spore case enclosed by the endoperidium has no stalk (sessile), and is opened at the top by a tear or pore. Microscopically, sterile cells, long-threaded cells called capillitium originate from the inner surface of the peridium; they are highly branched and interwoven. The spores are large, spherical, minutely warted, and brown.Astraeus species are strongly hygroscopic, and absorb moisture from the environment, so that the rays are closed over the spore case when dry, but open up flat when moistened.
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