Natures wonders: a fly trap with a neurotoxin (Introduction)

by David Turell , Monday, December 04, 2023, 16:05 (145 days ago) @ David Turell

Found in India:

https://www.science.org/content/article/toxic-bait-indian-pitcher-plants-lures-hungry-i...

"Pitcher plants in the genus Nepenthes thrive in places where they shouldn’t. There’s very little nitrogen in the Southeast Asian and Australian soils where they grow—but they do just fine, thanks to a macabre source for this essential nutrient: the dissolved flesh of small animals, mostly insects, that slip into their bulbous traps.

"A new study suggests why Nepenthes is so effective at catching its victims: It produces a sweet nectar containing a potent neurotoxin that could make them lose their balance at the pitcher’s edge. The work, published as a preprint on bioRxiv this month, is the first known example of nectar acting both as a lure and a poison.

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'Phytochemist Sabulal Baby has been studying carnivorous plants—“the most unique life forms on Earth,” he says—for more than a decade. He and his colleagues at the Jawaharlal Nehru Tropical Botanic Garden and Research Institute had previously discovered that the rims of the Indian pitcher plant Nepenthes khasiana are fluorescent and that newly opened traps emit carbon dioxide—features that attract insects. Because they knew the plants also produce nectar on and around their traps, which acts as a lure, they decided to examine it more closely.

"In other plants, such extrafloral nectar isn’t designed to harm insects. The liquid’s high sugar content appeals to ants, whose presence—and aggression—wards off potential herbivores. But when Baby and colleagues teased out the contents of the nectars of N. khasiana and several other pitcher plants growing in their institute’s botanic garden, they found something unexpected. The nectars contained (+)–isoshinanolone—a compound that interferes with the activity of an enzyme called acetylcholinesterase, which prevents the buildup of the neurotransmitter acetylcholine between neurons. Too much acetylcholine in lab animals leads to muscle cramps, weakness, blurry vision, and paralysis.

"And indeed when Baby and his colleagues examined ants that had drowned in the pitcher fluid of N. khasiana, they found almost no acetylcholinesterase activity in their tissues. Ants collected on the plant’s exterior showed more of this activity. This indicates that the nectar inhibits the insects’ locomotion, Baby says, making them temporarily clumsy and more likely to tumble into a pitcher. The nectar is a “toxic bait,” he says. “Prey capture by these pitchers is a story of total deception.”

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"Bauer notes that the authors’ method for nectar sampling—which involved rinsing cut sections of plant to collect the fluid—could have introduced intracellular compounds. So future work should confirm that (+)–isoshinanolone is in the nectar that the ants consume, not just the plant’s tissues.

"Still, she wouldn’t be too surprised if it is. Pitcher plants have “such an amazing diversity of tricks for how to trap insects” that toxic nectar would hardly be the strangest."

Comment: carnivorous plants are always amazing. Adding a neurotoxin to the trapping mix is not surprising. My wife has some Nepenthes in our house. Another design by God.