Migrating monarch butterflies 'nose' their way to Mexico

Sep 24, 2009
monarch butterfly
Photo by Derek Ramsey. Via Wikipedia.

The annual migration of monarch butterflies from across eastern North America to a specific grove of fir trees in Mexico has long fascinated scientists who have sought to understand just how these delicate creatures can navigate up to 2,000 miles to a single location. Neurobiologists at the University of Massachusetts Medical School (UMMS) have now found that a key mechanism that helps steer the butterflies to their ultimate destination resides not in the insects' brains, as previously thought, but in their antennae, a surprising discovery that provides an entirely new perspective of the antenna's role in migration.

"We've known that the insect antenna is a remarkable organ, responsible for sensing not only olfactory cues but wind direction and even sound vibration," said Steven M. Reppert, MD, professor and chair of neurobiology and senior author of the study. "But its role in precise orientation over the course of butterfly migration is an intriguing new discovery, one that may spark a new line of investigation into neural connections between the antennae and the sun compass, and navigation mechanisms in other insects."

In a paper to be published in the , Reppert and his colleagues Christine Merlin, PhD, and Robert J. Gegear, PhD, have demonstrated that the butterflies' antennae —formerly believed to be primarily odor detectors—are actually necessary for sun-related orientation, a critical function commonly thought to be housed solely in the insect's brain.

"Previous studies have shown that use their , an internal timing device such as the one that controls our own sleep-wake cycles, to correct their flight orientation and maintain a southerly course even as the sun moves across the sky," Reppert said. The time correction factor of the sun compass mechanism was assumed to reside in the brain, where the sun compass itself is located, although this presumptive role of brain clocks had never been tested directly.

Recalling an observation from 50 years ago—made even before the discovery that millions of monarchs fly to specific wintering grounds in Mexico—when it was noticed that migrating butterflies became lost in free flight when their antennae were removed, Reppert and colleagues sought to unravel the role of the antennae in migration.

In their studies, the investigators removed the antennae of a number of butterflies and tested their ability to fly south while tethered in an outdoor flight simulator rigged to calculate the insects' flight direction. They found that the antennaeless migratory butterflies could not orient themselves to the proper southerly direction, while butterflies with intact antennae could orient correctly. They also showed that the molecular cycles of the brain clocks were not altered by removing the antennae and that the antennae actually contain circadian clocks that function independently of those in the brain.

The researchers next covered the antennae in black paint, effectively blocking light sensing by the antennal clocks. Those butterflies homed in on an incorrectly fixed direction: the insect's brain could sense light but couldn't adjust the timing of the sun's movement across the sky in order to steer towards the proper destination. However, when the team used clear paint—which did not alter antennal light input—the butterflies accurately established the southerly flight orientation, indicating that the antenna's reading of light is key to navigation.

The Science paper, "Antennal circadian clocks coordinate sun compass orientation in migratory monarch butterflies," will be published September 25. Reppert, who is also the Higgins Family Professor of Neuroscience at UMMS, has been a pioneering force in the effort to understand monarch butterfly navigation and migration and hopes to trace the neural connection between the antennae clocks and the brain's sun compass. In addition, his team is investigating other functions of the that they believe are critical for successful migration.

Source: University of Massachusetts Medical School (news : web)

Explore further: Invasive parasitic fly on Galapagos Islands probably came from mainland Ecuador

Related Stories

How monarch butterflies are wired for navigation

May 04, 2005

In their extraordinary annual migration from North America to Mexico, monarch butterflies are known to use the angle of polarized sunlight as a celestial guide to help them keep to a straight and true path southward. But ...

Genetic basis for migration

Mar 31, 2009

Scientists studying Eastern North American monarch butterflies (Danaus plexippus) have uncovered a suite of genes that may be involved in driving the butterflies to migrate towards Mexico for the winter. Their research, publis ...

Monarchs fly south for the winter

Sep 12, 2005

As many as 300 million monarch butterflies are now flying south from Canada and the northern United States to winter in Mexico and Southern California.

Recommended for you

Telling the time of day by color

20 hours ago

Research by scientists at The University of Manchester has revealed that the colour of light has a major impact on how the brain clock measures time of day and on how the animals' physiology and behavior adjust accordingly. ...

Aphrodisiac for fish and frogs discovered

Apr 17, 2015

A supplement simply added to water has been shown to boost reproduction in nematodes (roundworms), molluscs, fish and frogs – and researchers believe it could work for humans too.

Evolution puts checks on virgin births

Apr 17, 2015

It seems unnatural that a species could survive without having sex. Yet over the ages, evolution has endowed females of certain species of amphibians, reptiles and fish with the ability to clone themselves, ...

Humans can't resist those puppy-dog eyes

Apr 16, 2015

When humans and their four-legged, furry best friends look into one another's eyes, there is biological evidence that their bond strengthens, researchers report.

Roundworm parasite targets canine eyes

Apr 16, 2015

(HealthDay)—A small number of dogs and cats across the United States have been infected by a roundworm parasite that targets the eye, according to a new report.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.