Environment

Pollution can play havoc with pollinators’ favorite flower smells. But one kind of moth can learn how to take to an unfamiliar new scent like, well, a moth to a flame.
Floral aromas help pollinators locate their favorite plants. Scientists have established that air pollutants scramble those fragrances, throwing off the tracking abilities of such beneficial insects as honeybees (SN: 4/24/08). But new lab experiments demonstrate that one pollinator, the tobacco hawkmoth (Manduca sexta), can quickly learn that a pollution-altered scent comes from the jasmine tobacco flower (Nicotiana alata) that the insect likes.
That ability may imply that the moth can find food and pollinate plants, including crucial crops, despite some air pollution, researchers report September 2 in the Journal of Chemical Ecology. Scientists already knew that some pollinators can learn new smells, but this is the first study to demonstrate an insect overcoming pollution’s effects on odors.
Chemical ecologist Markus Knaden and colleagues focused on one pollutant — ozone, the main ingredient in smog. Ozone reacts with flower aroma molecules, changing their chemical structure and therefore their fragrance.

Sign Up For the Latest from Science News

Headlines and summaries of the latest Science News articles, delivered to your inbox

In Knaden’s lab at the Max Planck Institute for Chemical Ecology in Jena, Germany, his team blew an ozone-altered N. alata scent from a tiny tube into a refrigerator-sized plexiglass tunnel, with a moth awaiting at the far end of the tunnel. Usually, when the moth smells the unaltered floral fragrance, it flies upwind and uses its long, skinny mouthparts to probe the tube the way that it would a blossom.
The researchers expected that the modified scent might throw the moth off a little. But the insect wasn’t attracted at all to a flower aroma exposed to levels of ozone that are typical on some hot, sunny days.
In addition to scent, tobacco hawkmoths track flowers visually, so Knaden’s team used that trait, along with a sweet snack, to train the moth to be attracted to a pollution-altered scent. The researchers wrapped a brightly-colored artificial flower around the tube to lure the moth back across the tunnel, despite the unfamiliar aroma. And the team added sugar water to the artificial flower. After a moth was given four minutes to taste the sweet stuff, it was attracted to the new smell when sent into the tunnel 15 minutes later, even when neither the sugar water nor the visual cue of the artificial flower was present. 
[embedded content]
In the lab, researchers showed that tobacco hawkmoths can learn to drink from a fake flower whose scent has been scrambled by pollution. To train the moths to accept the altered scent, a visual cue — dressing up a tube emitting a fouled bouquet as an artificial flower — attracts the moth, and a sugar-water reward teaches the insect that it’s worth a return trip.
Still, in an ozone-polluted environment in the wild, tobacco hawkmoths would have to be close enough to a tobacco flower to see it to learn its altered scent, and Knaden isn’t sure how often that will occur. The moths are difficult to observe in nature because they feed at twilight and are fast flyers.
“This study is a clarion call to other scientists” to examine whether and how different pollinators might also adapt to human-driven changes to their environment, says chemical ecologist Shannon Olsson of the Tata Institute of Fundamental Research in Bangalore, India, who wasn’t involved with the work.
Although the results suggest that some adaptation by insects to pollution is possible, Knaden is cautious about being too optimistic. “I don’t want the take-home message to be that pollution is not a problem,” he says. “Pollution is a problem.”
This study focused on only one moth species, but Knaden’s team is now working on planning experiments with other pollinators that are easier to follow than tobacco hawkmoths. While he suspects honeybees might also be as adaptable as the moth was, that won’t be true of every pollinator. “The situation can become very bad for insects that are not as clever or cannot see that well.” More

Last year marked the third year in a row of when Indonesia’s bleak rate of deforestation has slowed in pace. One reason for the turnaround may be the country’s antipoverty program. That initiative is associated with a 30 percent reduction in tree cover loss in villages, researchers report June 12 in Science Advances. In 2007, […] More

Water pollution, Science News, April 11, 1970 — A new water pollution control bill that provides clear assignments of liability without proof of negligence to the source of an oil spill was signed into law by President [Richard] Nixon last week…. It would add pesticide levels to the factors involved in formulating all new water […] More

Allison Fong dangles over the edge of a “river” running through a massive chunk of sea ice floating between the North Pole and Russia’s Komsomolets Island. The river cracked open in the ice just a few days ago, exposing the Arctic Ocean below. Already starting to freeze over, the river’s surface is a dark scar […] More

If you’ve ever had the misfortune of stepping on a Lego, you know the plastic building blocks have absolutely no give. Now, scientists have discovered another unpleasant consequence of the toys’ indestructibility: A single Lego could take hundreds of years to break down in the ocean.   Earth’s oceans are littered with plastic of all kinds […] More

Getting set for a black gold rush, Science News, February 14, 1970 — Nobody has ever done what the engineers designing the Trans-Alaska Pipeline are faced with: the need to carry hot oil through the Arctic. The Trans-Alaska Pipeline, expected to be completed in 1972, will carry 600,000 barrels of oil a day across Alaska. […] More