Time internal

2019-03-07 11:10:16

By Matt Walker BIOLOGICAL clocks don’t just keep animals in sync with their environment. Researchers have found the first evidence that these clocks are also essential for coordinating the body’s inner workings. Biological clocks allow organisms to anticipate when to feed, mate or, in the case of some insects, find safety in numbers by emerging from pupae en masse. Periodic environmental cues, such as dawn or dusk, regulate these clocks, and there is evidence that matching clocks to these cues helps animals live longer. But if this is the only function of these clocks, they should disappear over time in populations raised in an environment that has no periodic changes, says Amitabh Joshi, a biologist at the Jawaharlal Nehru Centre for Advanced Scientific Research in Bangalore, India. He decided to test this in fruit flies. Traits that confer no fitness advantage to the flies are known to be washed away by random mutations within 200 generations. Joshi and his colleagues bred a colony of fruit flies for 600 generations under constant brightness. They collected the eggs of the last generation and placed groups of them in either constant light or dark conditions, or a 12-hour light and dark cycle. The “hatching rhythm” of the flies disappeared under constant light conditions, but reappeared when triggered by the move into a dark environment (Naturwissenschaften, vol 86, p 448). So the flies had retained the genetic cogs of their body clocks. “It’s strong evidence for some intrinsic benefit of possessing a clock per se that is quite independent of synchronising one’s activities with the environment,” says Joshi. The researchers think the clocks help animals coordinate metabolic and physiological processes. “Internal synchronisation could give a fitness advantage,