James Carey has spent most of his adult life studying the mating and foraging habits of insects, concentrating on young bugs with a zest for life. But an accidental discovery has turned his career upside down.
Now, instead of worrying about how the Mediterranean fruit fly procreates and stays alive, he's trying to understand how it dies. He calls it the "biology of death," and it's an area of research that has received scant attention over the years.
Traditionally, biology is focused on young individuals in the prime of life, says the professor of entomology at the University of California, Davis.
"When they get old, they're boring and nobody cares about them," he says.
That's pretty much what he had thought when he instructed a postgraduate researcher from Greece, Nikos Papadopoulos, to take one project a step further. They had been studying the mating behavior of the Mediterranean fruit fly. The Med fly lives an average of about 60 days, and that brief life span allows researchers to study many generations in a relatively short period of time, so it is a popular subject for research into various life processes.
"So I said let's monitor the mating behavior for a couple of hundred of these flies until each one drops dead of old age," Carey recalls. They didn't expect to learn much, because mating occurs during the prime of life, but what the researchers saw was "just remarkable," he says.
"Lo and behold, about 30 days into this, Nik observed some of these flies flat on their backs in a catatonic state, with their legs straight up like the classic Far Side dead bug," Carey says.
But the flies weren't dead.
"If you nudge them they get up and run around and fly and more or less look normal in the early stages," he says.
But the condition turned out to be progressive as the flies became more and more listless. In a couple of weeks, they died.
Nearly all of them went through the same pattern, and Carey says he had never seen that kind of behavior before with any insect. But he thinks he and his researchers have stumbled upon something that could prove vitally important in the study of aging, even human aging.
The on-the-back routine was the beginning of the end for the flies, a "biomarker," Carey calls it, signaling that the life of the fly had entered a terminal phase. It wasn't because of anything that had happened in the lab. It's just that their time had come, he says.
This "supine behavior," as he calls it, occurred at different times for different flies, but it always lead to death within about 14 days. So flies that began lying on their backs at 30 days were usually dead at around day 44. And those hardier bugs that didn't flop over until they were 60 days old died about the age of 74.
"So it's not just age dependent," he says. The research was published in the Aug. 22 issue of British journal Proceedings of the Royal Society: Biological Sciences.
The next phase of the project, which is funded by the National Institute of Aging, will seek to determine the cause of death among the flies, which Carey suspects may be almost as varied as it is among humans. What's significant, he says, is that nearly all the flies followed the same pattern, so something was ordering "the onset of the end phase of life," he says.
He likens it to the human condition in which an elderly person begins using a cane, then a walker, then a wheelchair, and finally is bedridden.