Butterflies Use Antenna GPS to Guide Migration

Scientists have finally located the 24-hour clock that guides the migration of monarch butterflies. Instead of being in the brain where most people expected, it turns out the circadian clock is located in the butterflies’ antennae.

Every fall, monarchs make an impressive 2,000-mile trek south, using the sun to guide them to the exact same wintering spot in central Mexico. But because the sun is a moving target, changing position throughout the day, biologists have long speculated that in addition to having a “sun compass” in their brains, butterflies must use some kind of 24-hour clock to guide their migration. Now, researchers have located this special GPS system.

The scientists had been studying the ability of butterfly antenna to sense odors when they uncovered something surprising: When they clipped off the insects’ antennae and tethered them in a flight simulator, the butterflies no longer flew in a uniform direction. Without their feelers, the butterflies lost the ability to navigate using the sun, as if they could no longer adjust their direction based on the time of day. This raised the prospect that the timing mechanism may actually be in the antennae.

The researchers tested their hypothesis by painting the antennae of half their butterflies with black enamel, which blocked all input from the sun, and the other half with clear paint that allowed the sun’s rays through. While the monarchs covered with clear paint kept flying south, the butterflies with blacked-out antennae started to drift consistently north, suggesting that their molecular clock was running about an hour off schedule.

The new finding not only changes how scientists think about butterfly antennae, but may also suggest a similar role for an antennal clock in other types of insects, such as bees and ants, that also operate elaborate navigation systems. Like butterflies, honeybees use a sun compass to find flowers and communicate their specific position to the rest of the hive, and they could be using a circadian clock in their antenna to adjust the sun’s position to the time of day.

Original article here.