A still from a video about the roaches' behaviour (Photo: AP/Ayako Wada-Katsumata)
Ever heard that saying about how cockroaches will be the only creatures who survive if nuclear war breaks out (Mythbusters looked into that one, by the way, and they say it's "plausible")?
Well, here's more proof that it's very difficult to get rid of a cockroach: scientists at North Carolina State University has found that a strain of cockroaches in Europe has evolved to outsmart the sugar traps that people use to kill them, the BBC reports.
About 20 years ago, researchers using an apartment test kitchen to check on the effectiveness of roach traps noticed that they were no longer working because the insects refused to take the bait.
Apparently the roaches that avoid the traps, which are baited with a sweet, glucose-based substance, have a "reorganized" sense of taste: they have mutated so that the poisoned bait no longer tastes sweet, but bitter.
To test their theory, the researchers offered roaches a choice of two foods: peanut butter or glucose-filled jam.
"You can see the mutant cockroaches taste the jelly and jump back - they're repulsed and they swarm over the peanut butter," Dr. Coby Shal explains in the journal Science.
After watching the behaviour, the scientists examined the insects' taste receptors (cells that respond to flavour).
They found that the cells that normally respond to bitter tastes were now activated by glucose - proof that the insects had developed a different genetic makeup in order to stay alive.
The head of a male mutated cockroach with a flavoured test substance (Photo: AP/Ayako Wada-Katsumata)
In fact, a mutant cockroach that is exposed to a sweet flavour "behaves like a baby that rejects spinach," according to Dr. Schal: "It shakes its head and refuses to imbibe that liquid."
Dr. Elli Leadbeater at the Institute of Zoology in London told the BBC that the work is proof of evolution at work, calling the changed taste receptors "an effective way for natural selection to quickly produce cockroaches that won't accept the sugar baits that hide poison."
So: good news for the scientists studying this trait in cockroaches. They've got a fascinating finding that sheds more light on evolution.
Bad news for humans in the ongoing evolutionary battle with cockroaches.
"We keep throwing insecticides at them and they keep evolving mechanisms to avoid them," Dr. Schal said.