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The weird world inside a pitcher plant

They appear to be belching, or singing, or screaming out the catch phrase of their cousin in Hollywood — “Feed me Seymour.”

This is Nepenthes ampullaria, an unusual pitcher plant found on the islands of Southeast Asia and the Malay Peninsula. And its “Seymour” is the worm larva of Xenoplatyura beaveri, a species of fungus gnat that develops inside the plant’s mouth. When grown, it looks like a mosquito with big biceps.

They’ve got a strange relationship, these two.

The plant gives the gnat baby a safe place to eat and develop. In exchange, the baby builds a web across the plant’s lips, captures and eats other insects and then defecates into its maw, or pitcher. The plant eats the ammonium-rich droppings. And all is well in this miniature world of weird.

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It’s not romantic. It’s not sweet. But researchers call this relationship “mutualistic” in a study published Wednesday in Biology Letters. Their findings, based on laboratory experiments that simulated this insect-plant interaction in the wild, suggest that cohabitation may have its benefits for these two obscure organisms. How tiny pitcher plant communities like this one and others the group is studying function may reveal secrets of plant and insect life, said Weng Ngai Lam, a graduate student in botany at the National University of Singapore, who led the research.

These pitcher plants carry out a quirky version of their family’s strategies for surviving in a nutrient-poor environment. The alien mouths of pitcher plants are really just modified leaves shaped like fairy pottery and connected by a vine that can climb dozens of feet into the forest canopy. The pitchers collect rainwater and juices the plant secretes. Animals, mostly insects and the occasional crab or frog, find shelter and grow up inside this wet mouth.

But others get trapped and die there. Their proteins, once broken down, provide nutrients like nitrogen and phosphorus deficient in the soil.

Most species of pitcher plants lure prey into acid-filled pitchers with nectar-coated lips. The prey falls in, drowns and dissolves on contact.

But N. ampullaria is different. It makes less nectar and its juices are less acidic, and can’t seem to dissolve insects whole. Instead, it consumes fallen leaves and depends more on its inhabitants to break down its prey.

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That’s where X. beaveri comes in. The larvae have only been found in these pitcher plants in Singapore, and then only in 4 percent of those sampled. Though rare, they provide a significant service to a plant that can contain dozens of pitchers. Mosquitoes and flies, which also develop inside the pitcher’s fluid, get trapped in X. beaveri webs when exiting the plant as adults. It’s unclear if others are trapped going in. The larvae behave kind of like some worms that capture prey like spiders in caves, “only its cave is a very small pitcher,” Lam said.

In the lab, the insects captured mosquitoes and feasted on them for hours, depositing their nutrient-filled feces into the artificial pitcher like a toilet. The researchers wonder how important the web is for the plant and if other, more common inhabitants of N. ampullaria that don’t make a web can also provide this service of breaking down prey.

In the meantime, the pitchers’ mouths are always open.

This article originally appeared in The New York Times.

JOANNA KLEIN © 2018 The New York Times

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