Barometer Earthstar

Astraeus hygrometricus

 ( fleshy fruit body under humid conditions)

Barometer Earthstar (Astraeus hygrometricus) is so called because the fruiting body is so hygroscopic. It dries out quickly under dry conditions to a hard, leathery consistency and then undergoes an equally rapid transformation back to its fleshy state when it is humid.

Astraeus hygrometricus

(dry, curled-up fruit body)

As the fruiting body dries out, it loses its colour and curls its ray-like limbs around the central, spherical spore producing body. But even after a little rain, the limbs flex outwards to lift and support the spore producing body above the surface of the soil. Spores are released through the pore at the top very efficiently when rain drops hit the surface. The transformation from the curled-up dry state to the upright fleshy state takes about 30 minutes.

This is an uncommon fungus in Britain with a distinct, southern distribution (mostly in England). It is rarely recorded in Wales. Roger Phillips describes it as a vulnerable Red Data List species. The specimens here were found in a little wood near Melin Cryddan, Neath. Unlike our common earthstars, the fruiting bodies persist in good condition through the winter and into spring.