UMMS scientists show that monarch butterflies employ a magnetic compass during migration

June 24, 2014

WORCESTER, MA - Each fall millions of monarch butterflies use a sophisticated navigation system to transverse 2,000 miles from breeding sites across the eastern United States to an overwintering habitat in specific groves of fir trees in central Mexico. Scientists at the University of Massachusetts Medical School and Worcester Polytechnic Institute have identified a new component of this complex system. They reported in Nature Communications that monarchs use a light-dependent, inclination magnetic compass to help them orient southward during migration.

"Taken as a whole, our study reveals another fascinating aspect of the monarch butterfly migratory behavior," said senior study author Steven Reppert, MD, the Higgins Family Professor of Neuroscience and distinguished professor of neurobiology at UMass Medical School. "Greater knowledge of the mechanisms underlying the fall migration may well aid in its preservation, currently threatened by climate change and by the continuing loss of milkweed and overwintering habitats. A new vulnerability to now consider is the potential disruption of the magnetic compass in the monarchs by human-induced electromagnetic noise, which can also affect geomagnetic orientation in migratory birds."

Co-author Robert Gegear, PhD, assistant professor of biology and biotechnology at WPI, explained, "Our study shows that monarchs use a sophisticated magnetic inclination compass system for navigation similar to that used by much larger-brained migratory vertebrates such as birds and sea turtles."

Monarchs use a time-compensated sun compass in their antenna to help them make their 2,000 mile migratory journey to overwintering sites. During the absence of daylight cues, such as under dense cloud cover, migrants have been, surprisingly, seen flying in the expected southerly direction. It's been hypothesized that monarchs use geomagnetic cues to help navigate when day light cues are unavailable to them during migration.

Previous attempts by scientists to isolate use of an internal inclination compass in monarchs have yielded conflicting or unconvincing results. These studies, however, may not have accounted for the possibility that the magnetic compass was influenced by ultraviolet light that can penetrate cloud cover.

Given the ability of monarch cryptochromes (CRY), a class of proteins that are sensitive to ultraviolet A/blue light, to restore a light-dependent magnetic response in CRY-deficient Drosophila, Reppert and colleagues suspected that monarchs also possessed a light-dependent magnetic compass.

Using flight simulators equipped with artificial magnetic fields, Patrick Guerra, PhD, a postdoctoral fellow in the Reppert lab, examined monarch flight behavior under diffuse white light conditions. He found that tethered monarchs in the simulators oriented themselves in a southerly direction. Further tests in the simulator revealed that the butterflies used the inclination angle of Earth's magnetic field to guide their movement. Reversing the direction of the inclination caused the monarchs to orient in the opposite direction, to the north instead of the south.

To test the light-dependence of the monarch's magnetic compass, Dr. Guerra applied a series of wavelength blocking filters to the lights in the simulator. Monarchs exposed to light only in the wavelength range above 420nm exhibited a lack of direction by flying in circles. Monarchs exposed to light in the wavelength range above 380nm showed clear signs of directional flight. These tests showed that the monarch's magnetic compass, and thus directional flight, was dependent on exposure to light wavelengths (380nm to 420nm) found in the ultraviolet A/blue light spectral range.

Together, these results provide the first demonstration that the monarch butterfly uses a light-dependent, inclination compass during its long journey. It is also the first evidence of such a navigational tool in a long-distance migratory insect.

"For migratory monarchs, the inclination compass may serve as an important back up system when daylight cues are unavailable," Guerra said. "It may also augment hand-in-hand with the time-compensated sun compass to provide orientation and directionality throughout the migration process."

The next step for Reppert and colleagues will be to evaluate the molecular and genetic mechanisms of magneto-reception in the monarch butterfly and the involvement of CRYs.
-end-
About the University of Massachusetts Medical School

The University of Massachusetts Medical School (UMMS), one of five campuses of the University system, comprises the School of Medicine, the Graduate School of Biomedical Sciences, the Graduate School of Nursing, a thriving research enterprise and an innovative public service initiative, Commonwealth Medicine. Its mission is to advance the health of the people of the commonwealth through pioneering education, research, public service and health care delivery with its clinical partner, UMass Memorial Health Care. In doing so, it has built a reputation as a world-class research institution and as a leader in primary care education. The Medical School attracts more than $240 million annually in research funding, placing it among the top 50 medical schools in the nation. In 2006, UMMS's Craig C. Mello, PhD, Howard Hughes Medical Institute Investigator and the Blais University Chair in Molecular Medicine, was awarded the Nobel Prize in Physiology or Medicine, along with colleague Andrew Z. Fire, PhD, of Stanford University, for their discoveries related to RNA interference (RNAi). The 2013 opening of the Albert Sherman Center ushered in a new era of biomedical research and education on campus. Designed to maximize collaboration across fields, the Sherman Center is home to scientists pursuing novel research in emerging scientific fields with the goal of translating new discoveries into innovative therapies for human diseases.

University of Massachusetts Medical School

Related Butterflies Articles from Brightsurf:

Two centuries of Monarch butterflies show evolution of wing length
North America's beloved Monarch butterflies are known for their annual, multi-generation migrations in which individual insects can fly for thousands of miles.

Vagabonding female butterflies weigh in on reproductive strategies
A new study by researchers from the National Centre for Biological Sciences (NCBS), Bengaluru, published today in the Royal Society's journal Biology Letters, shows that dispersals, when undertaken by butterflies in search of unpredictable resources, selectively burden the egg-carrying females on their long flights.

Migration and dispersal of butterflies have contrasting effect on flight morphology
Migration and dispersal are vastly different activities with very different benefits and risks.

Scientists unravel the evolution and relationships for all European butterflies in a first
For the first time, a complete time-calibrated phylogeny for a large group of invertebrates is published for an entire continent.

Human handling stresses young monarch butterflies
People handle monarch butterflies. A lot. Every year thousands of monarch butterflies are caught, tagged and released during their fall migration by citizen scientists helping to track their movements.

What do soap bubbles and butterflies have in common?
A unique butterfly breeding experiment gave UC Berkeley researchers an opportunity to study the physical and genetic changes underlying the evolution of structural color, responsible for butterflies' iridescent purples, blues and greens.

Bacteria get free lunch with butterflies and dragonflies
Recent work from Deepa Agashe's group at NCBS has found that unlike other insects, neither butterflies nor dragonflies seem to have evolved strong mutualisms with their bacterial guests.

How some butterflies developed the ability to change their eyespot size
New insight on how a butterfly species developed the ability to adjust its wing eyespot size in response to temperature has been published today in eLife.

Butterflies can acquire new scent preferences and pass these on to their offspring
Two studies from the National University of Singapore demonstrate that insects can learn from their previous experiences and adjust their future behaviour for survival and reproduction.

Beating the heat in the living wings of butterflies
Columbia engineers and Harvard biologists discover that butterflies have specialized behaviors and wing scales to protect the living parts of their wings.

Read More: Butterflies News and Butterflies Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.