The fight for survival has led to the evolution of many strategies to obtain food, and some fungi have taken on a carnivorous lifestyle. There are over 700 species of carnivorous fungi identified that prey upon nematode worms, rotifers, and tardigrades. While fungi usually dine on decaying organic matter, sometimes that is not enough. Decaying wood, for example, does not provide enough nitrogen, and in these environments, fungi turn to carnivorism for their nitrogen needs. In case you were wondering, the Venus flytrap is also found in nitrogen-poor environments.
Carnivorous fungi are thought to have evolved about 419 million years ago, about 130-180 million years after nematodes emerged on this planet. Since then, carnivorous fungi have devised various ways to trap prey. More active forms of carnivorism rein in prey using lassos and rings, while more passive forms rely on sticky traps, time, and patience for unsuspecting worms to fall in.
Though carnivorous fungi have exist for all of human history, it wasn’t until the 1890s that Friedrich Wilhelm Zopf, a botanist and mycologist, recorded the first observation of carnivorous fungi in action (that we know about). He saw the fungus Arthrobotrys oligospora capture live nematodes and he began to grow the fungi with eelworms in a chamber. It only took two hours for the fungi to capture and kill the eelworm.
In 1959, Davis Pramer and Normal Stoll explored this predator-prey relationship further. When they gave Arhtrobotrys fungi sterile growth medium, they did not produce traps. But when the researchers first grew nematodes in the growth medium, filtered out the worms, and gave the remaining liquid to fungi, the fungi produced traps in response. They concluded that there was a substance produced by the worms that stimulated trap production, called it “nemin,” and ends their publication in Science with the sentence, “the nature of nemin remains to be determined.”
Fifty years later, scientists learned the identity of this mysterious substance. Yen-Ping Hsueh from the California Institute of Technology led a group of researchers to pinpoint the compounds that provoke fungi into carnivorism. These compounds are the ascarosides, pheromones that mediate aggression, mate finding, and development in nematodes. By adding these pheromones to fungal cultures, Hsueh found that a variety of fungal species “eavesdrop” on ascarosides to determine when to set traps.
The fungal world is full of fascinating strategies for survival and part-time carnivorism is only one scheme out of many. Though many of us may have never heard of the Arhtrobotrys fungi, another carnivorous fungus might be sitting right there on our plates at the dinner table: the oyster mushroom.
Want to dive deeper into the fungal world? Check the following articles:
There’s a Fungus Among Us and It’s Making Peppers Spicy
Botrytis cinerea: a fungus that gives us sweet wine grapes or moldy crops
Woah, such a great article! Thank you for sharing