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Fanged, carnivorous plant pals up with swimming ants

TheftUniversity of Cambridge

It ain't exactly a match made in heaven, but it's a friendship forged in the steamy peat swamp forests of Borneo.

That's where the fanged pitcher plant, or Nepenthes bicalcarata, teams up with a plucky, fluid-diving ant that makes its home nowhere else in the world but on the stalks and leaves of the carnivorous plant. The ant, Camponotus schmitzi, even swims around in the plant's lethal pools of digestive fluid!

Ordinarily, N. bicalcarata is a deathtrap for ants and many other insects. The plant uses beguiling colors and sweet nectar to lure prey to the lips of its large, deadly pitchers. Once insects crawl up to the lip, they encounter a slick substance that is impossible to cling to. 

Before you can say, "Dinner is served," the doomed insects plops into the pitcher, where they drown in a deep pool of digestive fluids. The fluids are not very strong, but they do help break down dead insects over time and provide the plant with crucial nutrients like nitrogen.

And, just to add to the plant's "Little Shop of Horrors" mystique, some of the plant's pitchers sport two thorns that look like fangs.

Enter C. schmitzi, a unique species of carpenter ant.

The ants are able to negotiate the plant's slippery lip goo without losing their footing, and they are skilled swimmers. Because of this, they are able to dive for and retrieve larger insects such as cockroaches, which they then eat.

Although scientists have long understood the benefit that the ants get from their close relationship with the plant, it's been more of a mystery as to what exactly the fanged pitcher plant gets out of the deal.

Now a study published Wednesday in the journal PLOS One sheds new light on the matter.

Although some scientists speculated that the tiny ants were kleptoparasites and simply stole prey from the pitchers, study authors noted that plants that contained ant colonies were bigger and healthier than plants without them. 

In a series of experiments, study authors determined that there were a couple of ways the ants improved the plant's health: First, they kept the surface of the plant clean. Second, they ate fly and mosquito larvae that lived in the pitcher's liquid.

By eating these larvae, the ants prevent them from stealing nutrition from the digestive pool. More important, they convert the larvae into nutrients for the plant in the form of waste. If the ants didn't do this, the larvae would eventually develop into a fly or mosquito and fly away.

To test this theory, study authors placed larvae and ants together in the pitcher fluids and watched as the ants tore into the larvae, dragging them out of the liquid and up the walls of the pitcher.

"Kneeling down in the swamp amidst huge pitcher plants in a Bornean rainforest, it was a truly jaw-dropping experience when we first noticed how very aggressive and skilled the Camponotus schmitzi ants were in underwater hunting," wrote lead author Mathias Scharmann, an insect biomechanics student at the University of Cambridge. "It was a mosquito massacre!"

(Click on "Video: Ant battles fly larvae" in upper left to check out the action.)

Study authors described the relationship as a novel type of "nutritional mutualism."

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Copyright © 2014, Los Angeles Times
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TheftUniversity of Cambridge
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