How monarchs arrive at their destination

Monarch butterflies en route to Mexico

Scientists create model of butterflies’ neural control mechanisms.

A team of scientists from the United States may have finally uncovered the mechanism that allows monarch butterflies to migrate up to 7,700 kilometers without getting lost.

And in the process they may have come up with the means of creating small, insect-sized drones that could aid scientists and environmentalists in efforts to protect the monarch butterflies on their yearly North American migration.

A group of mathematicians from the University of Washington teamed up with biologists from the University of Massachusetts and along with a third team of specialists from the University of Michigan set out to recreate the internal compass the monarchs use to navigate on their journey between the U.S. and Canada and Mexico.

In a report published in the journal Cell Reports, the joint team said it has modeled the neural control mechanisms at work in the butterfly’s brain.

Lead researcher Eli Shlizerman explained that, as a mathematician, he wanted to know how the insects’ neurobiological systems are wired and what can be learned from them.

“Monarch butterflies [complete their journey] in such an optimal, predetermined way,” he told BBC News, “they end up in a particular location in central Mexico after two months of flight, saving energy and only using a few cues.”

Shlizerman’s research identified that those cues depend entirely on the sun: “One is the horizontal position of the sun and the other is keeping the time of day, giving [the insects] an internal sun compass for traveling throughout the day.”

“We wanted to understand how the monarch is processing these different types of information to yield this constant behavior, flying southwest each fall,” said Shlizerman.

Monarchs watch the sun, but that’s not enough to get them where they need to go. They also need the time of day. For that they possess an internal clock of sorts that aids them in keeping track of the time. This “clock” is centered in their antennae.

After identifying the inputs for the butterflies’ internal compass, Shlizerman then created a system to simulate it consisting of two control mechanisms, one based on the timekeeping “clock” neurons in the butterflies’ antennae and the other from what are called azimuth neurons in their eyes, which monitor the position of the sun.

“The circuit gets those two signals then matches them, according to how it’s wired, to control signals that tell the system if a correction is needed to stay on the correct course.

“For me this is very exciting, as it shows how a behavior is produced by the integration of signals,” he added.

The scientists’ model also accounted for how the butterflies get back on course if they stray, and suggested that the neural mechanisms just reverse direction when it’s time for them to head back north in the spring.

“And when that happens, their compass points northeast instead of southwest,” said Shlizerman. “It’s a simple, robust system to explain how these butterflies, generation after generation, make this remarkable migration.”

Shlizerman explained that one of the team’s goals was to build a robotic monarch butterfly that could follow the insects and track their entire migration.

“It’s a very interesting application that could follow the butterflies and even aid in their preservation. Their numbers are decreasing, so we want to keep this insect, the only one that migrates these huge distances, with us for many years.”

Source: Discovery News (en), BBC News (en)

Thanks for reading,

Stewart Rogers USA-South Carolina.

 

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