Cockroaches can sense danger in sugar
Cockroaches will eat anything except sugar. Some of the common pests
have evolved to learn how to detect and avoid a certain kind of glucose
often used in bait traps, according to research published in Science.
Scientists focused on the slender and small brown German cockroaches,
which live all over the world in homes, offices and apartment buildings
- anywhere humans tread and leave crumbs behind.
An apparent disdain for sweet-laced traps was first observed in some
of these roaches in the early 1990s, about seven to eight years after
commercial traps using glucose came on the market and entered into
widespread use, said researcher Coby Schal of North Carolina State
University.
The roaches were evolving quickly, scientists found. New generations
were emerging that had inherited a genetic aversion to glucose. And now,
Schal says he and his colleagues understand why. Glucose-averse roaches
use their small taste-hairs to sample food first and if it contains
glucose, they actually taste it as bitter, not sweet.
"They bounce back as if they got an electric shock. It is a very,
very, very clear behaviour. They just absolutely refuse to ingest it,"
said Schal, a professor of entomology.
"It is kind of like if you put something really bitter or really sour
in your mouth and you immediately want to expel it." Schal said this
evolution came about "incredibly fast," but noted that the development
of antibiotic resistance in bacteria moves even faster.
It is hard to know what percentage of roaches have become averse to
glucose.
In this study, Schal and colleagues sampled various roaches from
infestations in the United States, Russia, Puerto Rico and South Korea.
Of 19 populations studied, they found seven that contained
glucose-averse roaches in their midst.
"This is a global phenomenon. It is not restricted to the US," he
said. Professional exterminators have known about the issue for some
time.
The agrochemical industry has responded by altering baits to replace
glucose with other attractants.
"We haven't used any kind of trap that used sugar for years," said
Bob Kunst, president of Fischer Environmental, a pest control company in
Louisiana.
Kunst, who was not involved in the study, described German
cockroaches as "filthy little creatures" because they can carry
salmonella.
Many of the major players in the pesticide industry keep their
attractants under wraps for competitive purposes, but experts have a
good idea of what works these days, he said.
"I would suggest certain high carbohydrate and base proteins are very
popular with roaches," Kunst said. To illustrate how keen these newly
evolved roaches are to survive and thrive without glucose, Schal and
colleagues filmed the critters as they chose a fructose-based blob of
jelly over one right next to it that contained glucose.
They also captured video of the roaches entirely avoiding a mound of
jam containing glucose and flocking instead to a glob of peanut butter.
"We are showing that cockroaches can learn incredibly well. They can
associate the punishment of tasting glucose with the smell of the bait."
Schal said he hopes the agrochemical industry will take steps to more
widely eliminate glucose from baits.The German cockroach represents just
one of about 5,000 species of roaches, and getting rid of the household
pests all together would not be a bad thing, he said.
- Inquirer.net |