Jerusalem -- While "navigation" systems in automobiles are afairly new (and still costly) innovation, monarch butterflies havemanaged for millennia to navigate their way for a distance of some 3000miles (4800 kilometers) each fall from Canada to Mexico (and vice-versain the spring) without losing their way.
The phenomenon oflong-range bird migration is a well-known one, but not in the insectworld. Also, among birds their migration route is a round-trip one,which they make more than once in their lifetimes, while for themonarch it is strictly a one-way trip for each butterfly. How do thesecreatures do it?
The mystery of the mechanisms involved in thisremarkable phenomenon has been resolved by a team of scientists who didthis by exploring the infinitesimal butterfly brain and eye tissues touncover new insights into the biological machinery that directs thisdelicate creature on its lengthy flight path.
The research team,led by Prof. Steven Reppert of the University of Massachusetts MedicalSchool, included Dr. Oren Froy, now of the Faculty of Agricultural,Food and Environmental Quality Sciences of the Hebrew University ofJerusalem. Others involved were from the Czech Academy of Sciences andthe University of California, Irvine. Their latest findings werepublished in a recent issue of Neuron magazine, constituting acontinuation of their earlier work, published in the journal Science.
Whilelight in general is essential to the functioning of the "biologicalclock" in the butterfly brain – governing its metabolic cycles,including its "signal" to migrate -- the researchers discovered that itis specifically the ultraviolet band of light that is crucial to thecreature's orientation. The butterflies have special photoreceptors forultraviolet (UV) light in their eyes which provide them with theirsense of direction.
They proved that this ultraviolet"navigation" is crucial by placing butterflies in a "flight" simulator.When a UV light filter was used in the simulator, the butterflies losttheir orientation
Further probing revealed a key wiringconnection between the light-detecting navigation sensors in thebutterfly's eye and its brain clock Thus, it was shown that input fromtwo interconnected systems – UV light detection in the eye and thebiological clock in the brain -- together guide the butterflies"straight and true" to their destination at the appointed times intheir two-month migration over thousands of miles/kilometers.
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