Brefeldia maxima slime mould at Strumpshaw Fen – Winter 2025

Wow – a new slime mould for us.

Along the drainage channel path at the edge of the alder carr we spotted some newly consolidated white aethalia. Were they a Fuligo species or surely they were Didymium spongiosum…? I mean, that’s our experience of a white slime mould in this form.

But there was something not quite Didymium spongiosum about them. Didymium spongiosum has that convoluted rugose structure, whereas these aethalia had a fuller aethalial form and a micro-cauliflower-like surface rather like a young Reticularia lycoperdon (false puffball) aethalium.

Note the translucent, silvery hypothallus coating on the twigs.

This aethalium still had a bobbly plasmodial surface structure and had been creeping along a mossy branch leaving a hypothallus trail.

A week later our expectations were confounded – the mature aethalia were dark fuscous to black 🤯 These weren’t Didymium spongiosum or any Fuligo species that we had ever seen or knew of. After some online research, I came across a reference to Brefeldia maxima. Cross-referencing with Bruce Ing’s ID handbook and online images – these must be Brefeldia maxima.

The aethalium below is the one in the fourth photo from the previous week’s sequence, that had fallen from the bramble stem.

And the aethalium below is the same one featured in the fifth photo from the previous week’s sequence.

Six weeks later the aethalial masses were still intact and had become the substrate for a white fungal mould. In the photo below, you can see the brown mass of spores.

NOTE: Didymium spongiosum is now the accepted name for Mucilago crustacea.