December 13, 2007

A Carnivorous Fungus Trapped in Amber

When people think about fungi, a few images usually come to mind. Usually, it's a mushroom or athlete's foot. Fungi are things that decompose organic matter and generally sit quietly. They don't lay traps and go fishing for animals to consume.

Except they actually do. A number of modern fungi derive part of their nutritional intake by catching small animals, particularly tiny worms called nematodes. Humans don't generally interact much with such fungi; they tend to be rather inconspicuous soil dwellers. The main exception to that is the oyster mushroom, Pleurotus ostreatus, which lots of people have eaten at least in Chinese food at some time.

At the same time, fossils of fungi are rare things. Having no hard parts, just chitin, not many fossils of ancient filamentous fungi have survived and many that have come down to us are little more than mycelia, bits of fungal thread, about which we can say very little in terms of their identity. We can say they're fungi, of course, but most often little more than that.

Researchers at Humboldt University of Berlin, however, have just increased our knowledge in a major way. In Mexico, they found amber dating back approximately 100,000,000 years... and inside is a carnivorous fungus caught in the act of fishing for nematodes. Prior to this find, the oldest known carnivorous fungus only went back about 20,000,000 years. If you're a mycologist, this is exciting stuff!

Ancient Fungus Lassoed Tiny Worms

The oldest-known carnivorous fungus on the planet has been found locked within 100-million-year-old amber.

The fossil find pushes back the known existence of such predators by about 80 million years. Like a microscopic Wild West of sorts, unsuspecting nematode worms and other tiny critters were subject to being lassoed by the ancient organism lurking in forest floor soils.

"These kinds of fossils are very hard to find, and this one is fantastic," said researcher Alexander Schmidt, a biologist at the Humboldt University of Berlin. "There is Mexican amber from about 15 to 20 million years ago with carnivorous fungus in it, but it doesn't show the trapping structures very well at all."

The new hunk of amber, he said, clearly shows predatory fungi rounding up tiny nematodes — about as long as a human hair is wide — right before tree resin encased the soil ecosystem.

The fungal traps were loops made of single cells. When wormy prey happened to slip through its vices, the ring cinched down on and stuck to its query. With a nematode in its grasp, the fungi got to work by injecting hyphae, or root-like projections of cells, into its body to suck out a nutritious meal...
The paper documenting the find is being published in tomorrow's issue of Science. I am so there!

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