by Carl Strang
If I had to choose one scientific journal to follow, it would be Science. Not only is this the most prestigious American journal (on par with Europe’s Nature), it is available at many public libraries and all college libraries. In addition to the original scientific papers published in Science, there is excellent reporting on results published elsewhere. Today I want to focus on one of the papers published in Science last year:
Merlin, Christine, Robert J. Gegear, and Steven M. Reppert. 2009. Antennal circadian clocks coordinate sun compass orientation in migratory monarch butterflies. Science 325: 1700-1704.
One of the wonders of nature in North America is the monarch migration. Each autumn, monarch butterflies from across eastern North America fly to a small area in the Mexican mountains and spend the winter there. They are removed by several generations from their ancestors who last made the trip. How do they navigate?
These three researchers looked at an aspect of this question. They knew from earlier studies that monarchs orient toward the sun to move in a southerly direction during their fall migration. Furthermore, the butterflies use a physiological clock (consisting of certain chemical reactions) to tell them where the sun is relative to south. This study found that the clock is located in the antennae rather than in the brain as had been thought. I would have guessed that persistent pheromones were involved somehow in monarch navigation, the butterflies perhaps following gradients of concentration with the aid of sensitive chemoreceptors in the antennae. It seems from this study that the antennae are indeed involved, but in a completely different way.
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