Attack of the parasitic jelly fungus

 

This gloopy-looking stuff is Yellow brain fungus Tremella aurantia, growing on the dead branch of a tree along one of my favourite walks, in the Deerness valley, County Durham. It’s a jelly fungus with a rather sinister lifestyle, parasitising another common fungus, hairy curtain crust Stereum hirsutum, which you can just see, dying, on the underside of the branch.

The microscopically-fine hyphae of the parasite, invisible to the unaided human eye, creep through the decaying wood, find and clamp onto those of their host and eventually kill it. The damp, foggy weather we’ve had recently has been perfect for the growth of the gelatinous parasite.

There are two common species of Tremella in the British fungal flora - this one and Tremella mesenterica - which are virtually identical and can only be easily identified by the hosts they parasitise: T. mesenterica preys on another crust fungus called Peniophora, which often grows on gorse stems hereabouts.

And here, a little further down the dead branch bearing the yellow brain fungus, is some more hairy curtain crust, so there’s plenty more of its victim for it to feed on.