In just over a week, UW-Madison will hold its annual “Darwin Day” celebration.
One group of university scientists is especially excited about this year’s festivities.
The team members will show off a new ant installation and talk up their groundbreaking work.
WUWM Environmental Reporter Susan Bence traveled to Madison to find out how the little bitty creatures might someday impact medicine and energy.
Millions of years ago in the heart of the Amazon, colonies of leaf-cutter ants played an integral role in cycling nutrients through the rain forest.
I’m watching some of their descendants inside the Microbial Sciences Building at UW Madison
These leaf-cutters are ensconced in a wooden-framed Plexiglas home. At one end, a man-made tree holds a net of maple and oak leaves. A clear tube connects that “forest” with a fungus garden the ants have been making.
“They can carry a tremendous amount of weight, roughly about 10 tens what something that small should be able to carry,” Garret says.
Garret Suen is a postdoctoral fellow immersed in leaf-cutter research. We’re watching hundreds of foragers methodically grasp bits of leaf and then march through the tube to the garden.
“You see all those ants holding the leaf pieces in place,” Garret says.
Garret says it’s not unusual, once arriving in the garden, for an ant to patiently hold the morsel “just so” for several hours.
“Other ants will come by and snip off a little piece of that little leaf and then chew it up and… they’ll incorporate it into the garden. .And then the fungus grows on top of it and the leaf pieces themselves provide the structure for the entire fungus garden. So all that white stuff that you see, that’s all fungus," Garret says.
If you happen to touch it...
“The leaf-cutter ant fungus garden is like it’s a giant sponge. It’s got the consistency of a sponge,” Garret says.
Garret calls the entire process a mutually beneficial relationship – the ants provide the garden with a constant supply of food. In turn, the fungus garden produces nutrient-packed sacks that the ants thrive on. And so it goes, seemingly forever.
“In fact the evolutionary history is so tight, it's been going on for roughly 50 million years – if the ants lose their fungus, the entire colony dies. In addition, the fungus cannot live without the ants. We’ve never been able to find this fungus just growing on its own in the middle of the forest,” Garret says.
Garret says scientists have been studying the behavior of leaf cutters for decades and know quite a bit about their living arrangements. For instance, some ants serve as soldiers to protect the foragers from potential predators. Other ants move garden debris to composting areas. And Garret says, without its queen, the colony would be nothing. We step over to another Plexiglas window, in hopes of spying her.
“The queen is going to be really hard to see, unfortunately. Like most leaf cutting ant colonies, the queens are buried deep inside, because they need to be protected,” Garret says.
If all goes well the queen will live 15 years and lay 200 million eggs.
But there are other amazing elements at work here that researchers still don't understand. Four floors up in the Currie lab, Garret's team of 20 is trying to unravel those mysteries. The scientists discovered that a parasitic mold is constantly present in the leaf cutter colony. And although it would seem the parasite would harm the ants, it does not. Garret says they somehow grow and maintain a bacteria that has protected the colonies delicate balance for perhaps 50 million years. He points to a white speck on one of the ants.
"So there seems to be this interesting theme where insects are using microbes, especially antibiotic producing microbes, to help defend themselves. Sort of like an immune system,” Garret says.
If the parasite threatens to infect the colony, somehow, the ants can produce big batches of the bacteria.
“You’ll see ants covered entirely in white, they look like sheep. It’s as though somebody took an ant and dusted it with baking sugar or some flour,” Garret says.
Garret says the bacteria could help scientists develop more effective antibiotics, not only for human health but also agricultural applications. He says researchers have known for years that ants harvest an enormous amounts of leaf material.
“Every single year a mature colony can harvest close to 400 kilogramsin dry weight of leaf materials. That’d be the same amount of weight as two SUVs,” Garret says.
That fact piqued the interest of the U.S. Department of Energy, which wanted to know how the process works. With federal funding, the UW team was able to fast forward the research. It unearthed the discovery that the ant system is a very efficient converter of biomass energy.
Because the members of the Madison team come from diverse backgrounds, Garret is confident they will be able to crack the codes that have kept the ants' world in perfect sync. He says every member of the team hopes to have his or her name attached to the next big breakthrough in understanding the elegance of the leaf-cutter system.
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