Fungi

A Grisly Meal

"Feed Me" by Renee Silverman. Image licensed under creative commons.
“Feed Me” by Renee Silverman. Image licensed under creative commons by Flickr.com.

By Emma Stuhl –

From grizzlies to wolves to the people-eating plant in The Little Shop of Horrors, carnivores capture our imaginations, and sometimes send shivers down our spines. So, imagine my astonishment and wonder when I recently learned that below the ground, at a microscopic scale, there are fungi that hunt and eat live animals. Fungi. Hunting. This astounding news took my understanding of the weirdness and wildness of fungal diversity to new heights.

I knew that some fungi kill our plant crops, such as the wheat rust that Ben described in his post last month. I also knew that some fungi are top-tier recyclers that break down 85 billion tons of carbon each year as they transform dead material into soil and food for their growing bodies. But I had never heard that some fungi snare, trap, and devour nematodes, amoebas, and bacteria in the soil. Images of a microscopic fungal safari began to flit through my mind, prompting me to spread the word—in classes, at dinner parties, and while blogging.

A fungus of the genus Arthrobotrys, showing adhesive nets which it uses to trap nematodes. Numbered ticks are 122 µm apart. "20100828 005957 Fungus" by Bob Blaylock. Image licensed under creative commons by wikipedia.com.
A fungus of the genus Arthrobotrys, showing adhesive nets which it uses to trap nematodes. 
“20100828 005957 Fungus” by Bob Blaylock. Image licensed under creative commons by wikipedia.com.

One such story starts with the large fungal spore of Arthrobotrys anchonia, our first creature-in-profile. Fungal spores are minute reproductive structures that help spread the relatively immobile creatures across the land. This particular spore is packed with enough energy to sprout a hypha, a root-shaped structure that is the main body of the fungus. As the hypha develops, it also grows circular, pressure-sensitive snares. Once these traps are set, the fungus waits, living on stored energy until a nematode inadvertently wanders into one of the rings. As soon as the snare senses a touch, the triggered cells rapidly expand and the loop tightens around the nematode. Fungi don’t have mouths, so the fungus penetrates and grows into the nematode’s body to consume the meal. This first food is critical to the life of the fungus; if it doesn’t capture prey before it uses up its stored energy, it withers and dies.

“Oyster Mushroom” photograph by Aaron Sherman. Image licensed under creative commons by wikipedia.com.
“Oyster Mushroom” photograph by Aaron Sherman. Image licensed under creative commons by wikipedia.com.

Even the more familiar oyster mushroom, Pleurotus ostreatus, is a well-equipped hunter. The fungus’ hyphae exude droplets of a paralyzing toxin into the soil. When nematodes unwittingly bump into these stupefying droplets, the fungus grows into the immobile prey and digests the quarry. Bacteria suffer a similar fate when they encounter this deadly trapper.

Fungi never cease to amaze. So next time life seems mundane, investigate one of these mysterious creatures. Scientists estimate that only 10% of all fungal species have been described. It is truly a frontier waiting to be explored.

Emma Stuhl is a second-year student in the Field Naturalist Program. Much thanks to Terry Delaney’s Plant Pathology course for inspiration and species information.

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