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Fungi form distinct networks depending on how food sources are arranged.
Fungi can be enigmatic organisms. Mushrooms or other structures may be visible above the soil, but beneath lurks a complex network of filaments, or hyphae, known as the mycelium. It is even possible for fungi to communicate through the mycelium—despite having no brain.
Other brainless life-forms (such as slime molds) have surprising ways of navigating their surroundings and surviving through communication. Wanting to see whether fungi could recognize food in different arrangements, researchers from Tohoku University and Nagaoka College in Japan observed how the mycelial network of Phanerochaete velutina, a fungus that feeds off dead wood, grew on and around wood blocks arranged in different shapes.
The way the mycelial network spread out, along with its wood decay activity, differed based on the wood block arrangements. This suggests communication because the fungi appeared to find where the most nutrients were and grow in those areas.
“[Our work] suggests that fungal mycelia may be capable of processing information about spatial locations within their network and adaptively altering their behavior,” the researchers said in a study recently published in Fungal Ecology.
Making a connection
To see how P. velutina would respond to specific arrangements of dead wood, the researchers soaked wood blocks and incubated them with the fungus on agar, giving it a chance to colonize. They then placed the wood blocks, which were colonized with fungus, in plates of damp soil that each had nine blocks arranged in either a circle or an X. They were then allowed to incubate for 116 days.
Because the soil layer was so thin, most hyphae, which usually grow and spread underground by releasing spores, were easily seen, giving the researchers an opportunity to observe where connections were being made in the mycelium. Early hyphal coverage was not too different between the X and circle formations. Later, each showed a strong hyphal network, which makes up the mycelium, but there were differences between them.
While the hyphal network was pretty evenly distributed around the circle, there were differences between the inner and outer blocks in the X arrangement. Levels of decay activity were determined by weighing the blocks before and after the incubation period, and decay was pretty even throughout the circle, but especially evident on the four outermost blocks of the X. The researchers suggest that there were more hyphal connections on those blocks for a reason.
“The outermost four blocks, which had a greater degree of connection, may have served as “outposts” for foraging and absorbing water and nutrients from the soil, facilitated by their greater hyphal connections,” they said in the same study.
Talk to me
Fungal mycelium experiences what’s called acropetal growth, meaning it grows outward in all directions from the center. Consistent with this, the hyphae started out growing outward from each block. But over time, the hyphae shifted to growing in the direction that would get them the most nutrients.
Why did it change? Here is where the team thinks communication comes in. Previous studies found electrical signals are transmitted through hyphae. These signals sync up after the hyphae connect into one huge mycelium, much like the signals transmitted among neurons in organisms with brains. Materials such as nutrients are also transferred throughout the network.
In these experiments, nutrients were equally distributed throughout the wood blocks and soil. Despite this, the strongest hyphal connections to the soil were on the blocks at the ends of the X, and why this happened is still a mystery. According to researcher Yu Fukasawa, the fungi possibly found areas richer in nutrients than others, and more connections offer more channels for signals and nutrients to travel through the entire mycelium.
“It’s possible that they prioritize outward growth to expand their colony and disregard the center, even when nutrients are still available there,” he told Ars Technica. “My hypothesis is that they are transmitting information across the mycelial network via electric potential.”
Throughout the circle formation, hyphal connections and decomposition activity were relatively equal from block to block, but a shift away from acropetal growth was also observed in the circle configuration. It seems that there must have been no need to form more connections around specific blocks because resources in the circle were just about equal for the fungi.
Some fungi are capable of processes that appear to mirror certain aspects of brain function. The research team argues that P. velutina showed signs of basal cognition, or cognition at the cellular level in brained organisms. This relates to sensory functions (finding nutrients) and the processing of information (sending signals about where those nutrients are throughout the mycelium). More research on when and why they send these signals still needs to be done.
Does this mean fungi have a way of thinking? Though a network of fungi can function like the neurons of a brain in some senses, they do not literally think. Let’s just hope that keeps them from plotting world domination.
Fungal Ecology, 2024. DOI: 10.1016/j.funeco.2024.101387
Elizabeth Rayne is a creature who writes. Her work has appeared on SYFY WIRE, Space.com, Live Science, Grunge, Den of Geek, and Forbidden Futures. She lurks right outside New York City with her parrot, Lestat. When not writing, she is either shapeshifting, drawing, or cosplaying as a character nobody has ever heard of. Follow her on Threads and Instagram @quothravenrayne.
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