Natures wonders: migrating monarchs set a course (Introduction)

by David Turell @, Thursday, April 14, 2016, 21:30 (950 days ago) @ David Turell

There are two ways, the sun's position and by a circadian clock:

"Their compass integrates two pieces of information—the time of day and the sun's position on the horizon—to find the southerly direction," said Eli Shlizerman, a University of Washington assistant professor.


"Monarchs use their large, complex eyes to monitor the sun's position in the sky. But the sun's position is not sufficient to determine direction. Each butterfly must also combine that information with the time of day to know where to go. Fortunately, like most animals including humans, monarchs possess an internal clock based on the rhythmic expression of key genes. This clock maintains a daily pattern of physiology and behavior. In the monarch butterfly, the clock is centered in the antennae, and its information travels via neurons to the brain.


"In their model, two neural mechanisms—one inhibitory and one excitatory—controlled signals from clock genes in the antennae. Their model had a similar system in place to discern the sun's position based on signals from the eyes. The balance between these control mechanisms would help the monarch brain decipher which direction was southwest.

"Based on their model, it also appears that during course corrections monarchs do not simply make the shortest turn to get back on route. Their model includes a unique feature—a separation point that would control whether the monarch turned right or left to head in the southwest direction.

"'The location of this point in the monarch butterfly's visual field changes throughout the day," said Shlizerman. "And our model predicts that the monarch will not cross this point when it makes a course correction to head back southwest."

"Based on their simulations, if a monarch gets off course due to a gust of wind or object in its path, it will turn whichever direction won't require it to cross the separation point.

"Additional studies would need to confirm whether the researchers' model is consistent with monarch butterfly brain anatomy, physiology and behavior. So far, aspects of their model, such as the separation point, seem consistent with observed behaviors."

comment: And all of this transpires through 4 larva/adult metamorphoses. It shows how information can be sustained and transmitted by DNA.

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