A ‘ghost mushroom’ captured at Merimbula by local photographer Peter Harris. Photo: Peter Harris.
The recent deluge of rain on NSW’s south coast has been good for one thing: mushrooms. But the mushrooms currently popping up in our hinterland forests aren’t just any mushrooms.
These are literally glowing in the dark. Think Avatar.
In recent weeks, photographers from as far south as the Victorian border to the Illawarra region have been capturing the phenomenon, known to science as “bioluminescent fungi”, but to most of us as “ghost mushrooms”.
The mushrooms have also been spotted in Tasmania and South Australia, usually in autumn and after bouts of rain.
The light seeping through the cell walls of these mushrooms is usually a greenish colour, like the iridescent green seen in an aurora in the night’s sky.
But as for why they’re glowing? That remains a mystery.
Professor Celeste Linde from the ANU Research School of Biology said there are about 94 known causes of bioluminescence in the natural world, and “fungi is just one of them”.
“It occurs in many other things – plants, animals, worms, snails, everywhere – and there are about 110 known species of mushroom that are bioluminescent, and quite a few are found in Australia.”
Ghost mushrooms in Bournda National Park. Photo: Tera Rickards.
The mushroom species most commonly glowing is the Omphalotus nidiformis, with fruiting bodies measuring up to 30 cm across.
Professor Linde says they create their own light through a chemical reaction, in a similar way to fireflies.
“It’s a compound that the organism has, called luciferin, and that interacts with an enzyme called luciferase,” she explains.
“If you give it a bit of energy and oxygen, there’s a chemical process that then emits light. The luciferin gets ‘excited’ and emits light to get less excited.”
The Omphalotus nidiformis mushroom is most commonly the species that glows. Photo: Cas Liber.
While ghost mushrooms usually luminesce for around 22 hours a day, the light peaks overnight.
“You just don’t see it in the day because there is too much other light drowning it out,” Professor Linde says.
Others glow only in their roots, or “mycelium”, so they are impossible to spot unless dug up.
“Given that it’s in these different organs of the fungus, it’s clear there’s probably not a function at all for bioluminescence,” she says.
One study in Brazil’s Amazon rainforest theorised that the light from the mushrooms attracted insects, which would then help spread the spores, but a subsequent study in South Australia couldn’t find any evidence of this.
“They thought the insects were not involved in dispersal, and so the bioluminescence has no effect. Basically, they suggest it’s an accident, and that bioluminescence is really cool and beautiful, but it has no function.”
But Professor Linde says, “We need to do more research”.
“Is there really no advantage of glowing in the night? Because it’s a funny accident to happen across 94 lineages in the world of all the biodiversity we know.”
Professor Celeste Linde (left) in the field, picking mushrooms. Photo: ANU.
In the meantime, do you need a night light in your house? Because that’s another weird thing about the ghost mushrooms.
“The amazing thing about bioluminescence in fungi is that it keeps glowing even after it is picked. One we picked kept on glowing for a day or two until it dried up.
“They are just really cool.”
