Hygroscopic Earthstar

(Astraeus hygrometricus)

               
Conservation Status

IUCN Red List

not yet assessed

Hygroscopic Earthstar

NatureServe

not listed

Minnesota

not listed

Occurrence

Widespread in North and Central America. Common in the Great Lakes and coastal states. Uncommon in Minnesota.

Season

Late summer and fall

Habitat/Hosts

Disturbed sites; old fields, pastures, roadsides

    Photo by Luciearl
 
Identification

This is a late season, small or medium-sized mushroom—small when closed, medium-sized when open. It is similar in appearance to true earthstars in the genus Geastrum, but it is not even closely related. It is an example of convergent evolution, where species of different lineages evolve similar features. It appears on the ground in late summer and fall, singly, scattered, or in groups. It is found in sandy soil in old fields, pastures, roadsides, and other disturbed sites. It obtains its nutrients from rotting wood (saprobic).

The fruiting body begins as a round to flattened case below the soil surface. It emerges as it expands and looks like a puffball. As it matures the outer layer of the case splits into 6 to 15 pointed rays, exposing a nearly spherical spore sac. When fully expanded, the fruiting body is to 3 or more in diameter.

The rays are tough and leathery when moist, about 1 32 (1 mm) thick, and more or less triangular. The upper (inner) surface is dark brown and is broken up into somewhat polygonal pieces. When fresh, it sometimes has a pale tan foreground with dark cracks and crevices, appearing like dried, cracked mud in a dry lake bed. The lower (outer) surface is covered with matted, blackish, hair-like fibers. When moist, the rays arch backward to the ground, raising the spore sac, and facilitating distribution of the dust-like spores. In dry conditions the rays fold back over the spore sac and become hard. Old specimens have blackish-brown rays.

The spore sac is stalkless, grayish or brownish, thin, papery, to 1¼ in diameter, and more of less spherical or somewhat flattened. The outer surface is roughened by numerous particles. There is a poorly-defined opening (pore) at the top. The interior (spore mass) when young is white, solid, and divided into oval-shaped compartments. As it matures it becomes brown to cocoa-brown, and powdery. At maturity, the spore case ruptures through the pore at the top, and the spores are disbursed by the wind.

It is not edible due to the toughness of the rays. Similar mushrooms collected and eaten in Asia, once thought the same, have subsequently been identified as new species.

 
Similar
Species

 

 
Distribution Distribution Map  

Sources: 4, 24, 29, 30.

 
Comments

 

 
Taxonomy

Division:

Basidiomycota (club fungi)

 

Subdivision:

Agaricomycotina (jelly fungi, yeasts, and mushrooms)

 

Class:

Agaricomycetes (mushroom-forming fungi)

 

Subclass:

Agaricomycetidae

 

Order:

Boletales (boletes)

 

Suborder:

Sclerodermatineae

 

Family:

Diplocystidiaceae

 
Synonyms

 

 
Common
Names

Barometer Earthstar

False Earthstar

Hygroscopic Earthstar

Water-measure Earthstar

 

 

 

 

 

 

Glossary

Saprobic

Obtaining nutrients from non-living organic matter, such as decaying plant or animal matter.

       
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Luciearl
       
  Hygroscopic Earthstar    
       

Earthstar Mushroom

They don't last long. Happen to catch this one on the right day. Went back a few days later and it was shrinking.

  Hygroscopic Earthstar    
       
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Other Videos
 
  Astraeus hygrometricus.wmv
espacenature
 
   
 
About

Published on Jan 30, 2010

   
       
  Astraeus hygrometricus rehydrating over about 40 minutes
Carl de Boer
 
   
 
About

Published on Sep 27, 2015

The "water measurer" earth star, although not a true earth star fungus, absorbs water from the air, opening its petals in response, and so is said to measure the relative humidity. Here, one is placed in a shallow pool of water and allowed to re-hydrate, with photos taken at 10 second intervals over about 40 minutes.

   
       
  Time Lapse of the Barometer Earthstar, Astraeus hygrometricus (Pers.) Morgan
zaacis1
 
   
 
About

Published on Sep 17, 2013

Time lapse footage at 2 seconds of a Barometer Earthstar. This specimen was brought in to the Trailside Nature Museum by Harry Zirlin. Read more on Tom Volk's website: http://botit.botany.wisc.edu/toms_fungi/dec2003.html

   
       
  False earth star (Astraeus hygrometricus)
ProjectHEALCreekRun
 
   
 
About

Published on Mar 19, 2013

I believe this is a false earth star (Astraeus hygrometricus). Collingswood, March, under oak.

   
       

 

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Luciearl
9/27/2020

Location: Cass County

Hygroscopic Earthstar


Luciearl
7/19/2018

Location: Cass County

They don't last long. Happen to catch this one on the right day. Went back a few days later and it was shrinking.

Hygroscopic Earthstar


     
     
 
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Created: 7/25/2018

Last Updated:

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