What It Looks (And Smells) Like When Mushrooms Hunt Nematodes
Merlin Sheldrake introduces readers to how invisible fungal forces shape our world in unexpected and ecologically important ways.
The following is an excerpt from Entangled Life: How Fungi Make Our Worlds, Change Our Minds & Shape Our Futures by Merlin Sheldrake.
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Entangled Life: How Fungi Make Our Worlds, Change Our Minds & Shape Our Futures
For some attracted by fungal chemical allure, the outcome is simpler: death.
Among the most impressive sensory feats are those performed by predatory fungi that trap and consume nematode worms. Hundreds of species of worm-hunting fungi can be found all over the world. Most spend their lives decomposing plant matter and only start to hunt when there is insufficient material to eat. But they’re subtle predators: Unlike truffles, whose scent, once begun, is always on, nematode-eating fungi only produce worm-hunting organs and issue a chemical summons when they sense nematodes are close by. If there is plenty of material to rot, they don’t bother, even if worms abound. To behave in this way, nematode-eating fungi must be able to detect the presence of worms with exquisite sensitivity. Nematodes all depend on the same class of molecule to serve a number of purposes, from regulating their development to attracting mates. In turn, fungi use these chemicals to eavesdrop on their prey.
The methods fungi use to hunt nematodes are grisly and diverse. It is a habit that has evolved multiple times—many fungal lineages have reached a similar conclusion but in different ways. Some fungi grow adhesive nets, or branches to which nematodes stick. Some use mechanical means, producing hyphal nooses that inflate in a tenth of a second when touched, ensnaring their prey. Some—including the commonly cultivated oyster mushroom (Pleurotus ostreatus)— produce hyphal stalks capped with a single toxic droplet that paralyzes nematodes, giving the hypha enough time to grow through their mouth and digest the worm from the inside. Others produce spores that can swim through the soil, chemically drawn toward nematodes, to which they bind. Once attached, the spores sprout and the fungus harpoons the worm with specialized hyphae known as “gun cells.”
Fungal worm-hunting is a variable behavior: Different individuals of a given species can respond idiosyncratically, producing different types of trap, or positioning traps in distinctive ways. One species— Arthrobotrys oligospora—behaves like a “normal” decomposer in the presence of plenty of organic material and, if needs be, can produce nematode traps in its mycelium. It can also coil around the mycelium of other types of fungi, starving them, or develop specialized structures to penetrate and feed off plant roots. How it chooses between its many options remains unknown.
How should we talk about fungal communication? In Italy, as we crowded around the hole in the muddy bank, peering in, I tried to imagine the scene from the truffle ’s point of view. In the excitement, Paride offered a lyrical interpretation. “The truffle and its tree are like lovers, or husband and wife,” he crooned. “If the threads are broken, there can be no going back. The bond is gone forever. The truffle was born from the root of the tree, defended by the wild rose.” He gestured to the brambles. “It lay inside, protected by the thorns like Sleeping Beauty, waiting to be kissed by the dog.”
The prevailing scientific view is that it is a mistake to imagine that there is anything deliberate about most nonhuman interactions. Truffle fungi are not articulate. They don’t speak. Like many of the animals and plants they depend on, truffle fungi react to their environment automatically, based on robotic routines that maximize their chance of survival. In stark contrast is the vivid experience of human life, where the quantity of a stimulus glides seamlessly into the quality of sensation; where stimuli are felt and arouse emotion; where we are affected.
I balanced on the muddy slope and suspended my nose over the pungent clod of fungus. No matter how hard I tried to reduce the truffle to an automaton, it kept springing to life in my mind.
When trying to understand the interactions of nonhuman organisms, it is easy to flip between these two perspectives: that of the inanimate behavior of preprogrammed robots on the one hand, and that of rich, lived human experience on the other. Framed as brainless organisms, lacking the basic apparatus required to have even a simple kind of “experience,” fungal interactions are no more than automatic responses to a series of biochemical triggers. Yet the mycelium of truffle fungi, like that of most fungal species, actively senses and responds to its surroundings in unpredictable ways. Their hyphae are chemically irritable, responsive, excitable. It is this ability to interpret the chemical emissions of others that allows fungi to negotiate a series of complex trading relationships with trees; to knead away at stores of nutrients in the soil; to have sex; to hunt; or to fend off attackers.
Anthropomorphism is usually thought of as an illusion that arises like a blister in soft human minds: untrained, undisciplined, unhardened. There are good reasons for this: When we humanize the world, we may prevent ourselves from understanding the lives of other organisms on their own terms. But are there things this stance might lead us to pass over—or forget to notice?
The biologist Robin Wall Kimmerer, a member of the Citizen Potawatomi Nation, observes that the indigenous Potawatomi language is rich in verb forms that attribute aliveness to the more-than-human world. The word for “hill,” for example, is a verb: to be a hill. Hills are always in the process of hilling, they are actively being hills. Equipped with this “grammar of animacy,” it is possible to talk about the life of other organisms without either reducing them to an “it” or borrowing concepts traditionally reserved for humans. By contrast, in English, writes Kimmerer, there is no way to recognize the “simple existence of another living being.” If you’re not a human subject, by default you’re an inanimate object: an “it,” a “mere thing.” If you repurpose a human concept to help make sense of the life of a nonhuman organism, you’ve tumbled into the trap of anthropomorphism. Use “it,” and you’ve objectified the organism and fallen into a different kind of trap.
Biological realities are never black-and-white. Why should the stories and metaphors we use to make sense of the world—our investigative tools—be so? Might we be able to expand some of our concepts, such that speaking might not always require a mouth, hearing might not always require ears, and interpreting might not always require a nervous system? Are we able to do this without smothering other life-forms with prejudice and innuendo?
Daniele wrapped up the truffle and carefully filled in the hole, pulling the clump of brambles back over the turned earth. Paride explained that it was to avoid disturbing the fungus’s relationship with its tree’s roots. Daniele said that it was to prevent other truffle hunters from following in our tracks. We strolled back through the field. The truffle ’s smell was less vivid by the time we arrived at the car and more muted still by the time we got back to the weighing room. I wondered how faint it would be by the time it was grated onto a plate in Los Angeles.
Excerpted from Entangled Life by Merlin Sheldrake. Copyright © 2020 by Merlin Sheldrake. Excerpted by permission of Random House Trade Paperbacks, an imprint and division of Penguin Random House LLC. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.