Oyster Mushroom (Pleurotus ostreatus)

Dear Readers, what could be more delicate and enticing than an oyster mushroom, with its frilly gills? They look to me like a troupe of ballerinas, and also turn my thoughts to frying them up in a bit of butter and garlic. Who would have thought that these fungi are nematode worm murderers? Well, buckle up because this is an astonishing tale, and makes it clear that mushrooms and toadstools are much more complicated than we ever thought.

Apparently, it’s been known since the 1980s that oyster mushrooms are carnivorous – they kill and digest microscopic nematode worms, But how? They can hardly knock them over the head with a stick, and the thought of oyster mushrooms prowling through the undergrowth is too much for even my imagination to comprehend.

What they actually do is far more interesting. Scientist Yen-Ping Hseuh discovered that the fungi produce little lollipop-shaped structures that break open when the nematode worms bash their heads against them.

‘Lollipop’ structures on the hyphae of oyster mushrooms (Photo byYi-Yun Lee, Academia Sinica, from the New Scientist article linked below)

These innocent-looking structures release a toxic nerve gas called 3-octanone – it triggers a cascade of calcium ions in the bodies of the worms, which induces paralysis and death. Fortunately, it’s only the hyphae (the parts of the fungus that live underground) that contain the toxin, rather than the fruiting bodies (which are the bits which end up in stir-fries).

Having dispatched their victims, the hyphae then grow into the bodies of the worms and digest them from the inside out. Lovely.

But why? I hear you asking. After all, most fungi make do with vegetable matter. It appears that the soils that the mushrooms grow in are particularly deficient in nitrogen, which is such an important element, and so difficult to access, that this fungus has turned to nematode-hunting. If we ever needed a hint that fungi are more closely related to animals than to plants, this is it.

You can read the whole article here.